hazus-mh risk assessment and user group series hazus …

FEMAFEMA 436

HAZUS®-MH Risk Assessment and User Group Series

HAZUS-MH and DMA 2000 Pilot Project – Portland, Oregon

March 2004

Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon

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Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon i

ABBREVIATIONS

B Billion

BIT Building Information Tool

CREW Cascadia Region Earthquake Workgroup

DEM U.S. Geological Survey Digital Elevation Model

DMA 2000 Disaster Mitigation Act of 2000

DOGAMI Oregon Department of Geology and Mineral Industries

FEMA Federal Emergency Management Agency

FIRM Flood Insurance Rate Map

FIT Flood Information Tool

G Gravitational acceleration

GIS Geographic Information System

HAZUS Hazards U.S.

HAZUS-MH Hazards U.S. Multi-Hazard

LCD Oregon Department of Land Conservation and Development

M Million

M Magnitude

MRP Mean return period

N/A Not applicable

NA Not available

NE Not evaluated

NFIP National Flood Insurance Program

OEM Office of Emergency Management

ORS Oregon’s Revised Statutes

PGA Peak ground acceleration

PMSA Primary Metropolitan Statistical Area

RLIS Regional Land Information System

USGS United States Geological Survey

ii Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon


Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon iii

CONTENTS

SECTION PAGE

ABBREVIATIONS ............................................................................. i

CONTENTS..................................................................................... iii

FOREWORD................................................................................... vii

EXECUTIVE SUMMARY ................................................................. ix

Portland Identified Hazards of Interest ............................................. x Portland’s Hazard Profiles .............................................................. x Portland’s Inventory of Assets ........................................................ x Portland’s Loss Estimates...............................................................xi Summary of Results and Conclusions..............................................xii Uncertainties and Limitations........................................................xiv

1 INTRODUCTION........................................................................... 1

2 IDENTIFICATION OF HAZARDS................................................... 3

Background Regarding the City of Portland...................................... 3 Identification of Hazards for the Portland Study Area........................... 5

3 PROFILE OF HAZARDS ................................................................ 7

Earthquake................................................................................... 8 Flood .........................................................................................10 Landslide ....................................................................................12 Wildland Fire ..............................................................................14

4 INVENTORY OF ASSETS............................................................ 17

5 LOSS ESTIMATES....................................................................... 27

Earthquake..................................................................................29 Flood .........................................................................................37 Landslide ....................................................................................46 Wildland Fire ..............................................................................52 Portland Relative Ranking Analysis ................................................58 Summary of Results and Conclusions..............................................59

REFERENCES..................................................................................63

APPENDICES 1 GLOSSARY 2 DATA SUMMARY 3 RELATIVE HAZARD RANKING BACKGROUND

iv Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon

TABLES

TABLE PAGE ES-1 Summary of Loss Estimates for Portland...................................... xi ES-2 Relative Risk Categories Used for Infrastructure............................ xi ES-3 Summary of the Relative Risk of Loss and

Exposure Estimates for Infrastructure.......................................... xii 2-1 Qualitative Hazard Ranking Results for Multnomah County............. 6 3-1 Historic Landslides for Portland (1996-2002)............................... 13 4-1 Inventory of General Building Stock........................................... 21 4-2 Inventory of Critical Facilities.................................................... 23 5-1 Summary of Risk Assessment Methodology Selection................... 27 5-2 Summary of the Relative Risk Categories Used for Critical Facilities ......................................................... 28 5-3 Estimated Social Impacts from Earthquake.................................. 29 5-4 Estimated Damages/Losses to General

Building Stock from Earthquake................................................. 31 5-5 Infrastructure at Risk from a 100-Year Earthquake Event............... 33 5-6 Infrastructure at Risk from a 500-Year Earthquake Event............... 33 5-7 Estimated Damage to Hazardous Materials Sites

from PGA-specific Earthquakes ................................................. 34 5-8 Estimated Damage to Transportation Lifeline

Systems from an Earthquake...................................................... 34 5-9 Estimated Damage to Utility Lifeline

Systems from an Earthquake...................................................... 34 5-10 Estimated Damages for Other Lifeline Facilities

from a 100-year Earthquake........................................................ 35 5-11 Estimated Damages for Other Lifeline Facilities

from a 500-year Earthquake........................................................ 35 5-12 Estimated Population at Risk from Riverine Flood........................ 38 5-13 Estimated Exposure Values for Structures at

Risk from Floods ..................................................................... 40 5-14 Estimated Damages/Losses to General

Building Stock from Floods....................................................... 41 5-15 Infrastructure at Risk from Riverine Flood................................... 43 5-16 Estimated Population at Risk from Landslides .............................. 46 5-17 Estimated Exposure Values for Structures

at Risk from Landslide Hazard................................................... 48 5-18 Infrastructure at Risk from Landslide .......................................... 49 5-19 Estimated Population at Risk from Wildland Fires ........................ 52 5-20 Estimated Exposure Values for Structures

at Risk from Wildland Fires....................................................... 54 5-21 Infrastructure at Risk from Wildland Fire..................................... 55 5-22 Summary of Loss Estimates for Portland ................................ 58 5-23 Summary of the Relative Risk Categories

Used for Infrastructure.............................................................. 58 5-24 Summary of the Relative Risk of Loss and

Exposure Estimates for Infrastructure.......................................... 59

Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon v

FIGURES

FIGURE PAGE 1-1 Risk Assessment Process............................................................. 1 2-1 Regional Map Showing the Portland

Study Area and Surrounding Counties........................................... 3 2-2 City of Portland Study Area Delineated by Census Tract.................. 4 2-3 Identification of Hazards of Interest.............................................. 5 3-1 Probability of Exceeding Various Peak

Ground Acceleration Levels for Portland....................................... 9 3-2 Major Past Earthquakes for the Pacific

Northwest (1600 to 2002)............................................................ 9 3-3 100-Year and 500-Year Flood Zone Boundaries ............................11 3-4 Landslide Hazard Areas for Portland

Study Area and 1996 Landslide Locations ....................................13 3-5 Areas at Risk from Wildland Fire Hazard .....................................15 4-1 Distribution of General Population by Census Tract.......................18 4-2 Distribution of Low Income Population by Census Tract.................19 4-3 Distribution of Elderly Population by Census Tract........................19 4-4 Annual Population Change by County

for the Portland/Vancouver PMSA...............................................20 4-5 Change in the Share of County Population

for the Portland/Vancouver PMSA...............................................20 4-6 Distribution of Commercial Building

Stock Exposure Density .............................................................22 4-7 Critical Facilities.......................................................................24 4-8 Transportation Lifelines .............................................................25 4-9 Utility Lifelines ........................................................................25 5-1 Distribution of General Population Density

in Relation to the Earthquake Hazard ..........................................30 5-2 Distribution of Elderly Population Density

in Relation to the Earthquake Hazard...........................................30 5-3 Distribution of Low-Income Population Density

in Relation to the Earthquake Hazard...........................................31 5-4 Residential Dollar Loss Density

for 500-Year Earthquake Event...................................................32 5-5 Commercial Dollar Loss Density

for 500-Year Earthquake Event...................................................33 5-6 Distribution of Critical Facilities in Relation

to the Earthquake Hazard Based on Soil Type ...............................35 5-7 Distribution of Transportation Lifeline Systems in Relation

to the Earthquake Hazard Based on Soil Liquefaction Potential........36 5-8 Distribution of Utility Lifeline Systems in Relation to

the Earthquake Hazard Based on Soil Liquefaction Potential ...........36 5-9 Distribution of Population Density in Relation

to 500-Year Flood Extent...........................................................38 5-10 Distribution of Elderly Population Density

in Relation to 500-Year Flood.....................................................39 5-11 Distribution of Low-Income Population Density

in Relation to 500-Year Flood.....................................................39

vi Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon

5-12 Dollar Loss Density for Annualized Flood Losses for Residential Structures........................................42

5-13 Dollar Loss Density for Annualized Flood Losses for Commercial Structures.......................................42

5-14 Critical Facilities in Relation to the 500-Year Flood Zone ...............44 5-15 Transportation Lifeline Systems in

Relation to the 500-Year Flood Zone ...........................................44 5-16 Utility Lifeline Systems in Relation

to the 500-Year Flood Zone........................................................45 5-17 Population Density in Relation

to Landslide Hazard Areas..........................................................47 5-18 Elderly Population Density in Relation

to Landslide Hazard Areas..........................................................47 5-19 Low-Income Population Density in Relation

to Landslide Hazard Areas..........................................................48 5-20 Critical Facilities in Relation to Landslide Hazard Areas.................50 5-21 Transportation Lifeline Systems in Relation

to Landslide Hazard Areas..........................................................50 5-22 Utility Lifeline Systems in Relation

to Landslide Hazard Areas..........................................................51 5-23 Population Density Exposed to Wildland Fire................................53 5-24 Elderly Population Density Exposed to Wildland Fire.....................53 5-25 Low-Income Population Density Exposed

to Wildland Fire........................................................................54 5-26 Critical Facilities in Relation

to Wildland Fire Hazard Areas....................................................56 5-27 Transportation Lifeline Systems in Relation

to Wildland Fire Hazard Areas....................................................56 5-28 Utility Lifeline Systems in Relation

to Wildland Fire Hazard Areas....................................................57 5-29 Projected Population Growth for Portland.....................................62

Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon vii

FOREWORD

Hazards U.S. (HAZUS), a risk-based Geographic Information System software management tool, is a critical tool for risk assessments to support mitigation planning and other emergency management efforts. HAZUS was developed as a tool that communities across the U.S. can use to evaluate the risk and potential loss associated with priority hazards. The Federal Emergency Management Agency (FEMA) developed HAZUS Multi-Hazard (HAZUS-MH), which includes the previously released earthquake model with updated data, and new models that estimate potential losses from wind (hurricanes) and floods (riverine and coastal).

In response to the requirements and deadlines of the Disaster Mitigation Act of 2000 (DMA 2000), FEMA’s Mitigation Division, has conducted a series of risk assessment pilot projects across the country using HAZUS-MH. These pilot projects demonstrate the value of using HAZUS-MH to prepare the risk assessments that are needed for hazard mitigation planning. HAZUS-MH applies engineering and scientific risk calculations that have been developed by hazard and information technology experts to provide defensible damage and loss estimates; these methodologies are accepted by FEMA and provide a consistent framework for assessing risk across a variety of hazards and locations. The pilot projects apply HAZUS-MH to evaluate and analyze hazards that can be addressed or supported by the software.

FEMA’s Mitigation Division supports the National Flood Insurance Program and a number of other areas related to mitigation planning across a range of hazards. Mitigation focuses on taking actions to reduce the impact of future natural hazards when they occur; in turn, it protects property and human life in the event of emergencies. Therefore, mitigation is a cornerstone of emergency management.

This document presents the results of the second risk assessment pilot project, which supported the City of Portland, Oregon, with short- and long-term efforts in hazard mitigation planning. The results of this risk assessment will be used by the City to address DMA 2000 requirements and meet a State of Oregon goal to develop model hazard mitigation plans in addition to the already approved “Clackamas County Natural Hazard Mitigation Plan.”

This risk assessment document was prepared in accordance with regulations in the following sources: Oregon’s Revised Statutes (ORS) Chapter 401 (“planning, preparing, and providing for the prevention, mitigation, and management of emergencies or disasters”); sample guidance outlined in the State of Oregon’s 1992 Natural Hazards Mitigation Plan; FEMA’s “A Guide to Using HAZUS for Mitigation,” FEMA 386-2, “State and Local Mitigation Planning How-To Guide: Understanding Your Risks – Identifying Hazards and Estimating Losses” (FEMA 2001), and FEMA 433, “How-To Guide for Using HAZUS-MH for Risk Assessment” (FEMA 2004). The risk assessment results presented in this document will eventually be included as part of the City’s hazard mitigation plan and are being applied by the City of Portland to support the identification and prioritization of appropriate mitigation strategies and actions to minimize potential losses from hazards. The State of Oregon’s 2000 Natural Hazards Mitigation Plan is available at http://www.osp.state.or.us/ oem/programs/hazard%20mitigation/state%20plan%20volume%201.htm.

Pilot project participants:

• FEMA Headquarters and Region X

• State of Oregon Emergency Management and the Department of Geology and Mineral Industries

• City of Portland Office of Emergency Management

• Partnering agencies, including City of Portland Bureau of Technology Services, Bureau of Environmental Services, and Bureau of Planning; Metro Regional Services; Multnomah County Office of Emergency Management; and Clackamas County Emergency Management

• Consultants to FEMA (Tetra Tech EM Inc. and PBS&J)

viii Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon


Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon ix

Hazard mitigation is any sustained action taken to reduce

or eliminate the long-term risk and effects that can result from

specific hazards.

FEMA defines a Hazard Mitigation Plan as the

documentation of a state or local government’s evaluation of

natural hazards and the strategy to mitigate such hazards.

Risk assessment is a methodology used to assess

potential exposure and estimated losses associated with priority

hazards.

EXECUTIVE SUMMARY

This pilot project was conducted by the Federal Emergency Management Agency (FEMA) to assist the City of Portland, Oregon, in meeting the following needs:

1) Address “hazard mitigation planning” in response to the requirements and deadlines of the Disaster Mitigation Act of 2000 (DMA 2000)

2) Meet a State of Oregon goal to develop model “Hazard Mitigation Plans”

The first step in hazard mitigation planning is completing a “risk assessment.” The risk assessment presented in this document is part of a series of pilot projects implemented by FEMA to demonstrate how the Hazards U.S. Multi-Hazard (HAZUS-MH) software program, a Geographic Information System (GIS)-based program, can be used to support the development of risk assessments as required under DMA 2000. The HAZUS-MH software program assesses risk in a quantitative manner to estimate damages and losses associated with natural hazards. HAZUS-MH can be used to streamline the risk assessment process for specific hazards because it (1) uses a consistent and defensible methodology and (2) produces maps and loss estimates that state, local governments, and the private sector can apply to develop quality risk assessments that form the basis for programs and plans required for emergency management.

The pilot projects demonstrate the value and benefits of using HAZUS-MH to perform the risk assessment portion of hazard mitigation plans required by DMA 2000. These pilot projects show that local communities can use HAZUS-MH as a tool to (1) make better decisions about infrastructure and disaster planning needs; (2) evaluate alternative mitigation scenarios; and (3) generate maps and other useful outputs to support community involvement and to facilitate the review of the DMA 2000 mitigation planning process and outcomes.

FEMA is providing technical support to the pilot project communities, including (1) supporting local data collection and evaluation to update HAZUS-MH provided data, (2) assisting with local hazard identification and prioritization, (3) providing Executive Overview training regarding the pilot project process and HAZUS-MH, (4) training local groups to update and run HAZUS-MH using local data, (5) interpreting and analyzing risk assessment results, and (6) supporting the integration of HAZUS-MH results into a local hazard mitigation plan.

This pilot project was completed in March 2003. The stakeholders for this pilot project agreed to focus on selected natural hazards and use project resources to analyze these hazards using the HAZUS-MH software and related methodology. Although DMA requirements address only natural hazards, HAZUS-MH, which is designed to assess earthquake, flood, and

x Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon

The study area is the geographic unit for which

data is collected and analyzed. In this case, the municipal boundaries of the City of Portland comprised

the study area.

The initial profile ranking process generally includes a preliminary review of the

hazard profiles to categorize hazards of

no/low to severe concern. For Portland, the pilot

project was able to build on previous ranking efforts

implemented by Multnomah County.

hurricane hazards, can also support the analysis of other types of natural and human-caused hazards.

This pilot project report serves four major purposes:

(1) Describes priority hazards of interest to the City of Portland and selected for this pilot project,

(2) Profiles significant historic hazard events,

(3) Inventories Portland’s assets, and

(4) Provides estimates of damages and losses or potential exposure for each hazard.

Significant findings for each area listed above are summarized below.

Portland Identified Hazards of Interest

The City of Portland, as defined by the City’s geographic boundary, was defined as the “study area.” Initially, the City identified 12 natural and human-caused hazards within the study area. From the list of 12 hazards, four were selected as hazards of interest for the City and for the pilot project. These four include earthquake, landslide, and wildland fire. The eight hazards eliminated from further consideration for this pilot project include dam failure, drought, hazardous materials site release, severe winter storm (ice and snow), terrorism, urban fires, volcano, and windstorm.

Portland’s Hazard Profiles

The four priority hazards selected for the pilot project were profiled using historical event data, FEMA information, and state and local knowledge. Each hazard profile addresses background and local conditions, historic frequency and probability of occurrence, severity, and historic losses and impacts. Each profile includes an “initial ranking” of the overall importance of that hazard (ranging from low/no concern to severe concern) in the Portland study area. Of the four priority hazards, three were ranked as severe (earthquake, landslide, and wildland fire) and was ranked as high (flood).

Portland’s Inventory of Assets

HAZUS-MH provided data and local data were used to prepare an inventory of what can be damaged or lost if a hazard occurs. Specific assets evaluated for this risk assessment include population, buildings, critical facilities, including infrastructure (roads and bridges) and lifelines (pipelines and other utilities). This report also explains how local data were used to supplement or replace HAZUS-MH supplied data. Over $59 billion of assets were identified for the Portland study area, including residential and commercial structures and building content, critical facilities, and infrastructure (utilities and transportation lifelines).

Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon xi

Portland’s Loss Estimates

Table ES-1 summarizes the loss and exposure estimates for the Portland study area. The annualized loss column shows the average annualized loss estimated for the earthquake and flood hazard. Loss estimates could not be calculated for the landslide and wildland hazards based on current data limitations. The residential and commercial assets at risk column shows the value of building stock estimated to be at risk for each hazard based on available knowledge of the hazard and HAZUS-MH inventory data. The annualized loss estimate per $1,000 of assets at risk compares the annualized loss estimate to the assets at risk. In this case, the ratio is lower for earthquake than it is for flood. Although the earthquake hazard is estimated to have a greater loss estimate than flood ($29.7 million versus $15.4 million), its relative impact is lower because the area at risk is larger (in this case, the entire city is at risk for earthquake, whereas only flood zone areas are at risk for the flood hazard). This type of evaluation assists in comparing impacts across hazards and serves as one input to the city’s mitigation planning efforts.

Table ES-1. Summary of Loss Estimates for Portland

Hazard Annualized Loss Estimate

Residential and Commercial Assets at Risk Estimate(s)

Annualized Loss Estimate per $1,000 of

Assets at Risk

Earthquake $29.7M $59B 0.5

Flood $15.4M $5.9B 2.6 Landslide NE $8.8B NA

Wildland Fire NE $7.8B NA Notes: NE indicates not evaluated. NA indicates not available. M indicates millions and B indicates billions. Dollars rounded to the nearest hundred thousand (column 2) or million (column 3). For the flood hazard event, the 500-year at risk residential and commercial building stock is shown in column three. For earthquake, all of the residential and commercial building stock is exposed and used as the at-risk estimate.

DMA 2000 requires risk to be assessed qualitatively (such as high, medium, or low) and quantitatively, where feasible. For infrastructure (critical facilities, transportation lifelines, and utility lifelines), loss or exposure estimates are presented in this pilot study as a percent of total facilities at risk or damaged. These loss and exposure percentages are then used to express relative risk qualitatively, using the scale shown in Table ES-2.

Table ES-2. Summary of Risk Categories for Infrastructure

Percent of Facilities Exposed or Impacted Relative Risk Classification Less than 1 percent Considered to present No or Low Risk

Between 1 and 5 percent Considered to present Limited Risk

Between 5 and 20 percent Considered to present Moderate Risk

Between 20 and 40 percent Considered to present High Risk

Over 40 percent Considered to be Severe Risk

Annualized loss is the estimated long-term value

of losses to the general building stock averaged on an annual basis for a

specific hazard type. Annualized loss considers

all future losses for a specific hazard type

resulting from possible hazard events with

different magnitudes and return periods, averaged

on a “per year” basis. Like other loss estimates,

annualized loss is an estimate based on available data and

models. Therefore, the actual loss in any given

year can be substantially higher or lower than the

estimated annualized loss.

xii Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon

The Mean Return Period (MRP) considers the

severity of a hazard event that can occur within a given time period. For

example, the 100-year MRP event for earthquake

addresses the severity of ground shaking that has a 1

percent probability of occurring in any given year and is generally anticipated to occur at least once within

a 100 year period. The 500-year MRP event is

more severe than the 100-year event, but has a lower probability of occurring in

any given year (0.2 percent chance of occurring in any

one year and likely to occur once in a 500-year period).

The 100-year MRP earthquake in Portland

would be roughly equivalent to the ground shaking that would be associated with a 5.8 Magnitude earthquake

occurring in the Portland Hill area or a 7.0 Magnitude

earthquake occurring in the subduction zone (ocean).

The relative ranking of hazards identified

through this pilot project provides a starting point

for the mitigation planning committee, which will evaluate

additional hazards and mitigation goals and

options as it prepares the city’s all hazards mitigation plan.

Table ES-3 summarizes the relative risk categories for infrastructure for each of the hazards analyzed for the Portland study area.

Table ES-3. Summary of the Relative Risk of Loss and Exposure Estimates for Infrastructure

Hazard Critical Facilities Transportation Lifelines Utility Lifelines Earthquake –

100-year MRP Event

Limited Risk (2.7% to 4.3%)

No Risk to Limited Risk (0.0% to 1.4%)

Limited Risk to Moderate Risk (3.8% to 8.6%)

Earthquake – 500-year MRP

Event

Moderate Risk (11.6% to 16.1%)

Limited Risk to Moderate Risk

(1.3% to 18.5%)

Limited Risk to Severe Risk (3.8% to 57.4%)

Flood – 100-year MRP

Event

No Risk to Moderate Risk (0.0% to 7.2%)

Low Risk to Moderate Risk

(0.9% to 19.2%)

No Risk to Severe Risk (0.0 to 100%)


Event

No Risk to High Risk

(0.0% to 23.2%)

Moderate Risk to High Risk

(5.6% to 30.0%)


Landslide No Risk to High Risk (0.0% to 30.0%)


No Risk to Severe Risk (0.0% to 45.5%)

Wildland Fire No Risk to



(1.3% to 17.3%)

No Risk to High Risk (0.0% to 24.4%)

Notes: For categories where more than one loss ratio data is included, the relative ranking reflects the highest loss ratio within that category. Green indicates no to limited risk. Yellow indicates up to a moderate risk. Red indicates high risk to severe risk.

Summary of Results and Conclusions

As discussed in the loss estimate section and summarized on Table ES-1, HAZUS-MH was used to support loss estimates for the flood and earthquake hazard and exposure estimates for the landslide and wildland fire hazards. For the earthquake and flood hazards, the annualized loss estimate was then compared to the total assets at risk for each of these hazards. Based on the HAZUS-MH analysis and the input of the project team, the relative ranking of the four selected priority hazards for the City of Portland is estimated as follows (from highest to lowest concern):

1. Flood 2. Earthquake 3. Landslide 4. Wildland fire

Flood has a lower total loss estimate than earthquake ($15.4 million versus $29.7 million) but a greater proportionate impact on the assets at risk (2.6 for flood versus 0.5 for earthquake). The landslide and wildland fire hazards can not be compared directly to the flood and earthquake hazards because an annualized loss estimate was not feasible for these hazards. However, the exposures at risk for the landslide and wildland fire hazards are lower than the exposure at risk for the earthquake hazard and the likelihood that all of the inventory at risk would be lost should a landslide or wildfire occur is considered to be low. Therefore, these hazards are ranked lower than flood and earthquake for this analysis. Landslide has a greater exposure at risk

Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon xiii

For additional explanation of the meaning of the 100-year and 500-year MRP earthquake events, see

page xii.

For additional explanation of the meaning of the 100-year and 500-year MRP

flood events, see page xii or the Appendix 1 definitions for the 100-year flood and

500-year flood.

value than the wildland fire ($8.8 billion versus $7.8 billion); therefore, it is ranked higher than the wildland fire hazard above.

Other findings include:

? Growth trends indicate that the population in areas surrounding the study region is experiencing growth greater than that of the City of Portland. For example, the population of Multnomah County constituted 51 percent of the Portland/Vancouver area’s total population in 1970 and only 35 percent of the total population in 2000. The City of Portland comprises a large part of Multnomah County’s population. Studying growth trends can assist in state, regional and local emergency planning and mitigation decisions.

? Areas along the Willamette River include flood zones, landslide potential, liquefaction potential, soft soil areas, and significant development. The multiple hazard areas along the river, combined with the level of development, appear to indicate that this area may face greater risk of losses than other areas of the study region.

? Inventory in the study region is significant with, $59 billion in assets estimated, including: buildings, critical facilities, and infrastructure.

Earthquake

? For the 100-year MRP earthquake event, up to 1 percent of the households in the area (2,000 households) could require shelter. This increases to 4.6 percent (8,000 households) for the 500-year MRP event.

? For the 100-year MRP earthquake event, minor injuries are expected to impact up to 2,500 persons and major injuries and fatalities are expected to be as high as 200. For the 500-year MRP event, this increases 240 percent (to 8,500 persons) for minor injuries and 350 percent (to 900 persons) for major injuries and fatalities, respectively.

? The total economic loss ratio for residential and commercial occupancy classes for the 100- and 500-year MRP events ranged from 2 percent to 7.4 percent, respectively. The economic loss ratio represents the percent of the total building and content dollar value that would be required to repair or replace damaged structures and building content.

Flood

? For the 100-year MRP flood event, 4.9 percent (11,200 households) are exposed. Approximately 6.7 percent (15,300 households) are exposed to the 500-year MRP flood event.

? For the 100-year MRP flood event, 29,900 persons are exposed to this hazard (that is, live within the area likely to be impacted). This increases to 38,400 persons for the 500-year MRP event. For this

xiv Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon

hazard, socially vulnerable populations represent 17.7 percent and 22.6 percent of the total population exposed for the 100- and 500- year MRP flood events, respectively. Persons from low-income households represent 22.2 percent of the overall population. Therefore, it appears that socially vulnerable populations are not disproportionately exposed to this hazard.

? Commercial building class losses account for about 37 and 43 percent of the total estimated loss for both the 100- and 500-year flood events, respectively. However, commercial buildings and content represent only about 20 percent of the total building and content value in Portland. This appears to indicate that commercial exposure may warrant further examination in relation to the flood hazard, as it appears to be disproportionately exposed to the flood hazard.

Landslide and Wildland Fire

? The population at risk from landslides and wildland fires is 66,400 and 64,400, respectively. This indicates that exposure is somewhat greater for the landslide hazard.

? For the landslide and wildland fire hazards, total residential and commercial occupancy class value exposed to each hazard was $8.8 billion and $7.8 billion, respectively. This indicates that exposure is somewhat greater for the landslide hazard in the Portland area.

Uncertainties and Limitations

For this risk assessment, the loss estimates and exposure calculations rely on the best available data and methodologies. Uncertainties are inherent in any loss estimation methodology and arise in part from incomplete scientific knowledge concerning natural hazards and their effects on the built environment. Uncertainties also result from (1) approximations and simplifications that are necessary to conduct such a study, (2) incomplete or outdated data on inventory, demographic, or economic parameters, (3) the unique nature and severity of each hazard when it occurs, and (4) the amount of advance notice that the residents have to prepare for the event. These factors result in a range of uncertainty in loss estimates, possibly by a factor of two or more. As a result, potential exposure and loss estimates are approximate. These results do not predict precise results and should be used to understand relative risk.

At risk for the landslide and wildland fire hazards

indicates the number of persons or building value

lying within the geographic areas identified as defining

the hazard area.

Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon 1

Figure 1-1. Risk Assessment Process

STEP 1: IDENTIFY HAZARDS

STEP 2: PROFILE HAZARD EVENTS

USE RISK ASSESSMENT OUTPUTS TO PREPARE A HAZARD

MITIGATION PLAN

STEP 4: ESTIMATE LOSSES

STEP 3: INVENTORY ASSETS

INTRODUCTION 1

In November 2002, a pilot project was initiated between the Federal Emergency Management Agency (FEMA) and the City of Portland, Oregon, to demonstrate the applicability of using Hazards U.S. Multi-Hazard (HAZUS-MH) software to address the risk assessment requirements of the Disaster Mitigation Act of 2000 (DMA 2000). The risk assessment project was conducted to evaluate priority hazards of primary concern to the community, and to estimate potential damages and losses. This risk assessment provides a foundation for the community’s decision makers to evaluate mitigation measures that can help reduce the impacts of future hazard events.

The risk assessment process used for this pilot project is consistent with the process and steps presented in FEMA 386-2, “State and Local Mitigation Planning How-To Guide, Understanding Your Risks – Identifying Hazards and Estimating Losses” (FEMA 2001). Figure 1-1 shows the steps that comprise the risk assessment process. Details regarding how HAZUS-MH can be used to conduct a DMA 2000 risk assessment are provided in FEMA 433, “How-To Guide for Using HAZUS-MH for Risk Assessment” (FEMA 2004).

Two methodologies were used to assess potential exposure and losses associated with priority hazards for this pilot project. These methodologies are summarized below.

? The HAZUS-MH risk assessment methodology is parametric, in that distinct hazard parameters (for example, ground motion for earthquake and discharge velocity for flood) and inventory parameters (for example, first floor elevations and building types) are modeled to determine the potential impact (damages and losses) on humans, buildings, roads and other assets. For this risk assessment, the HAZUS-MH risk assessment methodology was applied using HAZUS-MH software to estimate losses associated with the earthquake and flood hazards.

? The HAZUS-MH supported risk assessment methodology was applied to analyze hazards of concern that are outside the scope of the current HAZUS-MH software. For these hazards, historic data were not adequate to support the estimation and modeling of future events and losses. Instead, HAZUS-MH inventory data and professional judgment and hazard area data regarding the geographic scope of each hazard were used to estimate exposure to the hazard. Estimated exposure to a hazard is different than an estimated loss. However, when data were not adequate to estimate loss, exposure (or at-risk inventory) was estimated as a first step to evaluating the risk. The landslide and wildland fire hazards were addressed in this manner. Over the long term, Portland will collect additional data to assist in estimating potential losses for these hazards.

2 Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon

For this risk assessment, the loss estimates and exposure calculations rely on the best available data and methodologies. Uncertainties are inherent in any loss estimation methodology and arise in part from incomplete scientific knowledge concerning natural hazards and their effects on the built environment. Uncertainties also result from (1) approximations and simplifications that are necessary to conduct such a study, (2) incomplete or outdated inventory, demographic, or economic parameter data, (3) the unique nature and severity of each hazard, and (4) the amount of advance notice residents have to prepare for the event. These factors can result in a range of uncertainty in exposure loss estimates, possibly by a factor of two or more. Therefore, potential exposure and loss estimates are approximate. These results do not predict precise results and should be used to understand relative risk.

This document is organized around the risk assessment process shown in Figure 1-1 and includes the following sections and appendices:

? SECTION 2: IDENTIFICATION OF HAZARDS – describes the study area and how the City identified priority hazards of greatest concern.

? SECTION 3: PROFILE OF HAZARDS – includes available data, information, and sources used to profile priority hazards.

? SECTION 4: INVENTORY OF ASSETS – describes the data collected and used to estimate the assets at risk (for example, buildings, people, and infrastructure, which includes).

? SECTION 5: LOSS ESTIMATES – describes the estimates of exposure or loss for each of the four priority hazards. It also summarizes the results of the analysis and presents annualized loss estimates, where possible, to support a relative ranking of the hazards.

? REFERENCES – includes a list of references.

? APPENDIX 1: GLOSSARY – includes a glossary of definitions.

? APPENDIX 2: DATA SUMMARY – provides a summary of local data collected and assessed for the pilot project.

? APPENDIX 3: HAZARD RELATIVE RANKING BACKGROUND – summarizes the framework for evaluating the relative risk of different hazards.


The study area is the geographic unit for which

data is collected and analyzed. In this case, the municipal boundaries of the City of Portland comprised

the study area.

IDENTIFICATION OF HAZARDS 2

This section provides background information about the “study area” for this risk assessment. It also describes the hazard identification process. This process included identifying an initial list of hazards and then selecting hazards of interest. Four natural hazards were selected for further profiling and assessment as part of this pilot project.

Background Regarding the City of Portland

The City of Portland is the most populous city in Oregon and the 28th most populous in the United States. Located in the northwest part of the state on the Willamette River, the City of Portland is the seat of Multnomah County and is in the heart of the Portland/Vancouver Oregon-Washington Primary Metropolitan Statistical Area (Portland/Vancouver PMSA). The Portland/Vancouver PMSA has a land area of 4,371 square miles and comprises six counties: Multnomah, Clark, Clackamas, Columbia, Washington, and Yamhill (shown on Figure 2-1). Its population of 1.95 million is expected to grow to 2.2 million by 2010 (Portland Development Commission 2003a). The land area for all of Multnomah County, in which most of the study area lies, is approximately 465 square miles or 297,600 acres. Multnomah is the most urban of the counties in the Portland/ Vancouver PMSA. The land area of the Portland study area is 144.8 square miles or 92,672 acres.

Figure 2-1. Regional Map Showing the Portland Study Area and Surrounding Counties

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MarionMarionMarionMarionMarionMarionMarionMarionMarion

TillamookTillamookTillamookTillamookTillamookTillamookTillamookTillamookTillamook

YamhillYamhillYamhillYamhillYamhillYamhillYamhillYamhillYamhill

PacificPacificPacificPacificPacificPacificPacificPacificPacific

WahkiakumWahkiakumWahkiakumWahkiakumWahkiakumWahkiakumWahkiakumWahkiakumWahkiakum

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ShermanShermanShermanShermanShermanShermanShermanShermanSherman

YakimaYakimaYakimaYakimaYakimaYakimaYakimaYakimaYakima

CowlitzCowlitzCowlitzCowlitzCowlitzCowlitzCowlitzCowlitzCowlitz

Grays HarborGrays HarborGrays HarborGrays HarborGrays HarborGrays HarborGrays HarborGrays HarborGrays Harbor MasonMasonMasonMasonMasonMasonMasonMasonMason

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ClackamasClackamasClackamasClackamasClackamasClackamasClackamasClackamasClackamas

ClatsopClatsopClatsopClatsopClatsopClatsopClatsopClatsopClatsopColumbiaColumbiaColumbiaColumbiaColumbiaColumbiaColumbiaColumbiaColumbia

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Washington

Clackamas

Clark

Portland Study Area


A major disaster declaration is a post-

disaster status requested by a state’s governor when local and state resources are not sufficient to meet disaster needs. It is based on a

damage assessment, and an agreement to commit state funds and resources to the long-term recovery. The

event must cause impacts that are clearly more than

the state or local government can handle alone.

As agreed upon by the pilot project participating agencies and shown on Figure 2-2, the study area for this risk assessment is limited to the geographic boundaries of the City of Portland. For this pilot project, the Portland study area included all census blocks and tracts entirely within the City boundaries and all census blocks and tracts that intersect with the City’s boundaries.

Figure 2-2. City of Portland Study Area Delineated by Census Tract

Portland is subject to substantial natural hazard risks. An examination of national data on disaster declarations provides a reference point for understanding the potential for future hazard events and the potential impact that hazards can have in this area. Of the 1,037 “major disaster declarations” in the 50 states, the District of Columbia, and nine U.S. territories between 1972 and 2000, the State of Oregon has claimed 12, ranking it 22nd in the number of disaster declarations for any state or territory (FEMA 2003a). Total aggregated losses from natural disasters in Oregon have mounted into the hundreds of millions of dollars during the past decade. In fact, over $220 million was provided to Oregon under several federal relief programs for three flood and landslide disasters that occurred in 1996 and 1997 (Oregon Office of Emergency Management [OEM] 2000).

The Portland study area, because of its setting, is subject to natural hazards, which result in disasters when they destroy human development or cause injury. During the winters of 1996 and 1997, the Portland area experienced floods, landslides, ice storms, and other disasters. Seismic activity, heavy precipitation, weather extremes, and geography will continue to result in earthquakes, floods, and landslides. In addition, periods of long dry summers and fuel accumulation (tree, grass, and understory growth) can contribute to the potential for wildland fires.

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Hazards of interest are those hazards that are

considered most likely to impact a community. These are identified

using available data and local knowledge.

Identification of Hazards for the Portland Study Area

The City of Portland initiated hazard identification efforts as part of its mitigation planning process. The City of Portland identified a preliminary list of hazards of concern during a pilot project meeting in November 2002. The preliminary list was based on past planning efforts and incorporated the professional knowledge of local, state, and federal planning and emergency response personnel. During the pilot project, the project participants, including representatives of the City of Portland, county and regional representatives, the State of Oregon, FEMA, and FEMA’s consultants, discussed the initial list of hazards.

Four hazards were selected for further evaluation as part of this pilot project. These hazards were considered “hazards of interest” of primary concern for the Portland study area. Figure 2-3 summarizes the initial hazard identification and selection process conducted for this pilot project. This figure is modified from Worksheet No. 1 of FEMA 386-2, “State and Local Mitigation Planning How-To Guide, Understanding Your Risks – Identifying Hazards and Estimating Losses” (FEMA 2001), which provides additional information on the hazard identification and selection process. Figure 2-3 summarizes the 12 initial hazards identified and the four hazards of interest selected for further analysis. It also shows historical event data and sources identified and used for the pilot project.

Figure 2-3. Identification of Hazards of Interest

This figure summarizes the pilot project hazard identification and selection process. Column A indicates the initial hazards identified. Column B shows hazards of interest carried forward for further study based on group discussion. The table also summarizes available information regarding each hazard and its impact on the Portland study area.

A B þ ̈ Dam Failure þ ̈ Drought þ þ Earthquake þ þ Flood þ ̈ Hazardous Material

Release þ þ Landslide þ ̈ Severe Winter Storm þ ̈ Terrorism þ ̈ Urban Fire þ ̈ Volcano þ þ Wildland Fire þ ̈ Windstorm

Summary of Hazards of Interest for Portland Pilot Project

Hazard Year(s) No. of Events Significant Impacts

Available Data Sources

and Maps

Earthquake 1872 to 1999 56 17 deaths during past 100 years

$2 billion losses (Nisqually 2001)

Cascadia Region

Earthquake Workgroup

(CREW) 2003; Metro 1999

Flood 1861 to 1999

14 major

1948 (31.6 feet above flood stage level) 1996 (30.2 feet) – 5 deaths, 100s of

homes, over $1 billion loss Metro 1999

Landslide 1996 800 17 homes destroyed, 64 badly damaged, no serious injuries

Oregon OEM 2000

Wildland Fire

1900 to 2002

0 Area wildfires have occurred in national forests south and west of Portland but

no events have caused Portland losses USFS 2004

Notes: Modified from FEMA 386-2, Worksheet No. 1 (FEMA 2001). Major flood events for the Columbia and Willamette River basins are indicated.


The Portland study area comprises a large portion of Multnomah County. The County has conducted previous mitigation planning efforts, including a qualitative ranking of hazards. Table 2-1 shows an initial qualitative ranking analysis for the pilot project hazards of interest that was as part of the Multnomah County Hazard Analysis effort. This analysis was developed under a separate study but is presented here because it supported the selection of hazards for the pilot project and presented a strong starting point for further study of the area’s hazards and refinement of the rankings to address the specific needs of the City of Portland. Also, this qualitative method of ranking is one option discussed in FEMA 386-2 and illustrates how one county applied the state’s qualitative ranking approach to initial hazard ranking. Section 3.0 provides detailed profiles of the hazards listed below. Also, the pilot project team identified additional factors to support analysis and comparison of the hazards and assigned a risk gauge initial profile ranking to each hazard, as discussed in Section 3.0.

Table 2-1. Qualitative Hazard Ranking Results for Multnomah County (Multnomah County 2002)

Hazard Severity Score

History (2)

Vulnerability (5)

Maximum Threat (10)

Probability (7) Total Score

Earthquake HIGH 20 50 100 70 240

Flood MEDIUM 20 25 60 42 147

Landslide HIGH 20 50 100 70 240 Wildland Fire HIGH 12 35 100 56 203

Notes: Categories were assigned weighting factors as noted in parentheses under the column heading. The categories are defined as follows:

• Numeric values (ratings used for History, Vulnerability, Maximum Threat, and Probability): Low = 1 to 3 points; Medium = 4 to 7 points; High = 8 to 10 points.

• History indicates the record of previous major occurrences. (Low = 0 to 1 event per 100 years; Medium = 2 to 3 events per 100 years; High = >4 events per 100 years) X Weighting Factor of 2.

• Vulnerability indicates the percentage of population and property at risk. (Low = <1% affected; Medium = 1 to 10% affected; High = >10% affected) X Weighting Factor of 5.

• Maximum threat indicates the maximum percentage of population and property at risk under a worst-case scenario. (Low = <5% affected; Medium = 5 to 25% affected; High = >25% affected) X Weighting Factor of 10.

• Probability indicates the likelihood of occurrence within a given period of time. (Low = > 1 chance per 100 years; Medium = > 1 chance per 50 years; High = > 1 chance per 10 years) X Weighting Factor of 7.

• Total score ranking is a quantitative measure relates to the qualitative description or “severity score” based on the following scale: 24 to 72 = Low; 73 to 168 = Medium; and 169 to 240 = High.


PROFILE OF HAZARDS 3

This section presents “hazard profiles” for the four hazards identified in Section 2.0: earthquake, flood, landslide, and wildland fire.

For the Portland study area, the City of Portland, its stakeholders, and FEMA consultants, conducted considerable research to obtain profile information for the priority hazards. Much of the data for these profiles was obtained from various regional studies including reports from the Oregon Department of Geology and Mineral Industries (DOGAMI), the Natural Hazards Mitigation Plan prepared by Oregon OEM, regional planning documents from Metro, emergency operations information from Multnomah County, and studies from the City of Portland. The Multnomah County qualitative ranking was used as one input to develop hazard profiles for this pilot project and this information was supplemented during the pilot project. Each hazard profile includes available hazard data regarding: (1) background and local conditions; (2) historic frequency and probability of occurrence; (3) severity; (4) historic losses and impacts; and (5) designated hazard areas. Available data sources are described and hazard area maps are provided with each profile. A summary of “risk factors” for each hazard profile includes (1) a column summarizing the Multnomah County Hazard Analysis qualitative results from Table 2-1 and (2) a column listing other summary considerations.

Finally, for each hazard, the project team prepared a preliminary overall assessment of the relative risk of each hazard in the Portland study area (ranging from no or low concern to severe concern). This assessment is presented as a “hazard risk gauge” in the upper corner of each hazard profile. The hazard risk gauge considers all of the information obtained and risk factors considered for these profiles. It builds on, and refines, the county-wide findings presented in Table 2-1 and presents the initial ranking assigned by the pilot project team using additional information and input and focusing on the specific study area defined by the city boundaries.

The risk assessment outputs developed as part of this pilot project (see Section 5.0) will inform the mitigation process and may lead to new conclusions about risk and to redistribution of mitigation resources.

Hazard profiles focus on answering the question:

How bad can it get? (FEMA 2001). To answer

this question, data regarding historic events,

future probability, severity, and hazard location are collected and evaluated.

Risk factors are characteristics of a hazard

that contribute to the potential losses that may occur in the study area.

The hazard risk gauge is a graphic icon used during the initial hazard ranking

process to convey the relative risk of a given

hazard in the study area. The scale ranges from

green, indicating relatively low or no risk, to red, indicating severe risk.


Earthquake

EARTHQUAKE HAZARD PROFILE

Background and Local Conditions There are several different sources for hazardous earthquakes in the Pacific Northwest. Oregon sits on the Cascadia Subduction Zone where the Pacific / Juan de Fuca Plate is sliding under (or being pushed under) the less dense North American Plate. While earthquakes along this zone occur infrequently (none since records have been kept), plate movement can produce major earthquakes. In addition, the western part of Oregon is underlain by a large and complex system of faults (for example, the Portland Hills) that can produce significant and more frequent earthquakes. Historic Frequency and Probability of Occurrence The Metro 1999 study cites research indicating that “major geologic structures capable of magnitude (M) 7 earthquakes” underlie the Portland study area. Since 1820, 7,000 earthquakes have been documented in Oregon. Fifty-six significant earthquakes occurred in or near the Portland study area between 1872 and 1999. Severe local earthquakes occurred in 1877, 1880, 1953, 1962, and 1993 (Metro 1999). Strong Pacific Northwest earthquakes also include an 1872 M 7.4 North Cascades event, an M 6.8 earthquake in 1873, a 1949 M 7.1 event near Olympia, Washington, a 1965 M 6.5 event in Seattle-Tacoma, and a 2001 Olympia, Washington event that caused over $2 billion in property damage (Oregon OEM 2000). Regional earthquakes, such as the deep, intra-plate Nisqually Earthquake of 2001 (Olympia, Washington) are felt widely in northwest Oregon. Figure 3-1 illustrates the annual probability of exceeding a range of peak ground acceleration (PGA) levels in Portland. Severity There is a direct relationship between a fault’s length and location and its ability to generate damaging ground motion. In Portland, smaller, local faults produce lower magnitude quakes, but their ground shaking can be strong and damage can be high as a result of the fault’s proximity. In contrast, offshore or distant subduction zone quakes can generate great magnitudes, but because of their distance and depth, may result in only moderate shaking in the Portland study area (Metro 1999). The Cascadia Subduction Zone fault could produce an earthquake of M 8.0 to 9.0 or greater. Geologic evidence shows that earthquakes of similar magnitude have occurred on average every 500 to 600 years in this area. Based on the Mutlnomah County analysis and pilot project data gathering and review, this hazard was given an initial profile ranking of severe. Historic Losses and Impacts Damage results from earthquakes because structures that cannot withstand the shaking, are situated on ground that amplifies shaking, or are located on soil that is subject to liquefaction. Structures can cause injury or fatalities and suffer content and functionality losses. The 2001 Nisqually event caused over $2 billion in losses. The two 1993 Klamath Falls earthquakes (M 5.9 and 6.0) caused damage to more than 1,000 buildings and $10 million in losses (DOGAMI 2002). Since 1872, there have been about 25 damaging earthquakes in Washington and Oregon (CREW 2003).

Multnomah County Hazard Analysis Summary of Risk Factors

Severity Score High Period of occurrence: At any time

History (2) 20 Probability of event(s):

Highly likely

Vulnerability (5) 50 Warning time: No warning time

Maximum Threat (10) 100 Major contributor(s): Highly active seismic

zone, local soil characteristics

Probability (7) 70 Cause injuries? Yes, and risk of death

Total Score 240 Potential facilities shutdown?

30 days or more

Magnitude (M) is a measure of earthquake size that represents the amount of energy released by an

earthquake. Energy release increases 30 times

for each integer on the magnitude scale. Moment

Magnitude is a direct measure of energy and is a more accurate measure of

the true strength or intensity of an earthquake.


Figure 3-1. Probability of Exceeding Various Peak Ground Acceleration Levels for Portland

Figure 3-2. Major Past Earthquakes for the Pacific Northwest (1600 to 2002)

Note: The Portland study area is highlighted in blue.

EARTHQUAKE HAZARD PROFILE (continued) Designated Hazard Areas The entire Pacific Northwest is subject to the earthquake hazard. However, certain local conditions can mitigate or amplify the effects. Figure 3-2 illustrates that the Portland study area has experienced earthquakes with various intensities of ground shaking. The figure shows major past earthquakes by moment magnitude.

0.050

0.100

0.150

0.200

0.250

0.300

0.350

0.400

0.450

0.500

0 0.002 0.004 0.006 0.008 0.01 0.012

Annual Probability of Occurrence

Pea

k G

rou

nd

Acc

eler

atio

n [

g's

] (S

oil

B)

Minimum PGA Average PGA

Maximum PGA

PGA [g] Shaking Level Expected Damage0.0 - 0.02 Negligible None

0.02 - 0-04 Very Light Very Minor0.04 - 0.08 Light Minor0.08 - 0.15 Moderate Minor - Moderate0.15 - 0.25 Moderate - Strong Moderate0.25 - 0.4 Strong Moderate - Extensive0.4 - 0.7 Violent Extensive

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WascoWascoWascoWascoWascoWascoWascoWascoWasco

ShermanShermanShermanShermanShermanShermanShermanShermanSherman

YakimaYakimaYakimaYakimaYakimaYakimaYakimaYakimaYakima

Hood RiverHood RiverHood RiverHood RiverHood RiverHood RiverHood RiverHood RiverHood River

MultnomahMultnomahMultnomahMultnomahMultnomahMultnomahMultnomahMultnomahMultnomah

CowlitzCowlitzCowlitzCowlitzCowlitzCowlitzCowlitzCowlitzCowlitz

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WashingtonWashingtonWashingtonWashingtonWashingtonWashingtonWashingtonWashingtonWashington

Grays HarborGrays HarborGrays HarborGrays HarborGrays HarborGrays HarborGrays HarborGrays HarborGrays Harbor MasonMasonMasonMasonMasonMasonMasonMasonMason

ThurstonThurstonThurstonThurstonThurstonThurstonThurstonThurstonThurston

KingKingKingKingKingKingKingKingKingChelanChelanChelanChelanChelanChelanChelanChelanChelan

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Major Past Earthquakesby Moment Magnitude

55.15.25.35.55.65.75.86.26.36.57.1

Note: PGA indicates peak ground acceleration. There is a 2 in 1,000 probability of an earthquake with a PGA of 0.2 or greater in any one year (or a 2 percent chance over a 10 year period).

Soil B is characterized as a

stiff, rocky soil. Portland generally

has softer soil, which tends to amplify ground

motion and increase potential

damage.


Flood

FLOOD HAZARD PROFILE

Background and Local Conditions Flooding results when rain or snowmelt creates water flows that exceed the carrying capacity of river channels or other watercourses and storage facilities (for example, reservoirs). Flooding poses a threat to safety and can cause severe damage to public and private property. In Oregon, flooding is most common when storms from the Pacific Ocean bring intense rainfall (typically between October and April). The area’s major rivers include the Columbia, Willamette, Clackamas, and Tualatin. There are also many streams in the area that drain to these rivers and can exacerbate riverine flooding primarily during prolonged wet periods. Local drainage flooding occurs on smaller streams, creeks, and drainage ways, and is more likely to result from heavy local storms and debris-clogged storm drain systems. This pilot project focuses on riverine flooding, which generally impacts larger areas at greater depths than drainage flooding. Historic Frequency and Probability of Occurrence Floods are a common and widespread hazard in Oregon. The Portland/Vancouver PMSA has been subject to major floods throughout recorded history. Flooding can be aggravated when heavy rains are accompanied by snowmelt and frozen ground. It was the combination of these factors that caused recent, disastrous floods in February and November 1996. Flood risk or probability can be expressed by frequency of occurrence. It is measured as the average recurrence interval for a flood of a given magnitude and can be stated as the percent chance that a flood of a certain magnitude or greater will occur in any given year. FEMA’s National Flood Insurance Program (NFIP) is based on the risk associated with a “100-year” or base flood; that is, a flood that has a one percent chance of occurring in any year. Although flash flooding is not a particular concern in Portland, rapid onset flooding can occur along tributaries to major rivers (for example, Johnson Creek). Major rivers such as the Willamette and Columbia will generally have more warning time before a flood occurs; these rivers are controlled by dams and also are monitored closely during heavy rain events. Severity Flooding can be a frequent, costly, and deadly hazard facing Portland; flash flooding also poses a significant danger. Many roads run through low-lying areas that are prone to sudden and frequent flooding during storms. Motorists often attempt to drive through barricaded or flooded roadways. Because it takes only 18 to 24 inches of water moving across a roadway to carry away most vehicles, this presents a significant potential cost and human health risk. The second largest impact on injuries results from people walking or playing in or near flooded areas. The lowest risk to humans is associated with flooding in the home. Generally, floods kill people in two ways: when people ignore basic safety precautions (such as evacuations and warnings), or when a flash flood hits an area with no warning. Floods can be very damaging, and depend on the depth and velocity of the floodwaters. During a severe event, buildings can be washed off their foundations; however, most flood damage is caused by water saturating materials that are susceptible to loss (for example, wood, insulation, and furnishings).


Severity Score Medium Period of occurrence: October through April

History (2) 20 Probability of event(s): Highly likely

Vulnerability (5) 25 Warning time: 0 to 3 hours (tributaries) or days (main stem of rivers)

Maximum Threat (10)

60 Major contributor(s): Intense precipitation,

increase in impervious surface, vegetation loss



30 days or more


FLOOD HAZARD PROFILE (continued) Historic Losses and Impacts Significant historic flooding has been recorded for the Willamette and Columbia River basins in 1861, 1880, 1881, 1894, 1909, 1913, 1927, 1928, 1942, 1946, 1948, 1961, 1964/1965, and 1996 (Oregon OEM 2000). Historic flood inundation levels for the Willamette River at Portland occurred in 1894 (35.1 feet above flood stage warning), 1948 (31.6 feet), 1964 (29.8 feet), 1974 (25.7 feet), and 1996 (30.2 feet) (Metro 1999). Major past events include floods in 1948 on the Lower Columbia River in the Portland/Vancouver PMSA that caused about 25 deaths; in December 1964 and January 1965 that forced the evacuation of thousands, destroyed scores of bridges and secondary roads, caused the Willamette River at downtown Portland to have a flood stage of 29.8 feet, caused $157 million in damages, and caused 17 deaths; and statewide floods in February 1996 that caused five deaths, forced thousands into shelter, destroyed hundreds of homes, caused damages in excess of $280 million, and forced the City of Portland to erect makeshift barriers to prevent flood waters from moving into the downtown area (Oregon State Police 2003). Twenty-seven counties, including Multnomah, were eventually covered by a disaster declaration due to the 1996 floods (Oregon OEM 2000). Many residents who have suffered damage rebuild in the same vulnerable areas, only to be flooded again. These properties are termed repetitive loss properties, and are troublesome because they continue to expose lives and property to flooding (Clackamas County 2002). Designated Hazard Areas According to NFIP, Oregon has 256 flood-prone communities, including all 36 counties. Flood hazard areas are defined as areas that would be inundated by a flood of a given magnitude. The areas subject to riverine flooding have been mapped by FEMA under the NFIP and are illustrated on Figure 3-3 for the Portland study area for the 100-year and 500-year flood zones. These areas are determined using statistical analyses of flood discharge data and hydraulic and topographic analyses. A 100-year flood has a 1 percent chance of being equaled or exceeded in any one year. This flood event is also referred to as the base flood. A flood that has a 0.2 percent chance of being equaled or exceeded in any one year is called a 500-year flood. The Columbia River and Willamette River are shown below.

Figure 3-3. 100-Year and 500-Year Flood Zone Boundaries

100-year

500-year

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Columbia River

Willamette River

The 100-Year Flood Zone represents the area that has

a 1 percent probability of being flooded in any given

year and a 100 percent probability of being flooded within 100 years. The 500-

Year Flood Zone includes a greater area, but has a lower probability of being flooded

in any given year (0.2 percent annual probability of being equaled or exceeded).


Landslide

LANDSLIDE HAZARD PROFILE Background and Local Conditions Landslides are part of the natural, on-going process of smoothing topographical high points. Landslides occur when gravitational forces associated with slide mass exceed the resistance produced by the material holding that mass in place. Landslides are downhill or lateral movements of soil and rock that can include rock falls, slides, slumps, lateral spreading, earth and mudflows, and settlement. Landslides can result from ground saturation after intense or prolonged rainfall, erosion associated with surface water runoff, improper or poorly designed drainage systems or slopes, vegetation removal by land clearing, and shocks or vibrations from earthquakes. After wildland fires, land is also more subject to landslide because resistance forces produced by roots associated with trees, shrubs, and grass are reduced. Many hillsides in the Portland/Vancouver PMSA are unstable and vulnerable to landslides and mudflows. Landslides associated with rainfall tend to be relatively smaller; earthquake-induced landslides may be much larger. The pilot project focuses on rain-induced landslides. Historic Frequency and Probability of Occurrence The Portland study area has been subject to major and minor landslides. Hundreds of landslides (as many as 800) were recorded during the February and December 1996 flood events. In general, landslide recurrence intervals are highly variable. Some large landslides are continuous and slow moving. Others are triggered by acute conditions and occur sporadically. Table 3-1 lists the types and number of landslides in the City of Portland from 1996 to 2002. Severity Existing mitigation and emergency directives for this risk in the Portland area evidence the high risk of this hazard. For example, the State of Oregon has a Debris Avalanche Action Plan that directs state agencies to seek solutions to reduce the loss of life from debris flow and landslides. The Multnomah County Hazard Analysis considered this hazard a high risk. Similarly, this hazard is considered a severe risk based on the Multnomah County hazard analysis and data reviewed by the risk assessment team as part of this project. Historic Losses and Impacts Hundreds of landslides occurred during the February and December 1996 flood events and accounted for 20 percent ($13 million) of the $64 million in damages associated with the February 1996 storms. During those events, 17 homes were completely destroyed and 64 were badly damaged due to landslides (Oregon OEM 2000). During the 1996 landslides, eight deaths were recorded statewide. During a March 1972 landslide, three motorists were injured in a mud and rockslide on Interstate 5 near Portland. Losses for the State of Oregon generally average less than one or two lives per year and between $1 million and $10 million annually (Oregon Department of Land Conservation and Development [LCD] 2003). Designated Hazard Areas Although the total area of land subject to a high potential for landslides is small, the consequences are serious when structures, roads, or lifeline systems are affected. Many hillsides in the study area are unstable and subject to slides and flows. Landslide losses most likely will increase because city -wide development is occurring on and near increasingly less


Severity Score High Period of occurrence: Fall, Winter, and Spring

History (2) 20 Probability of event(s): Occasional

Vulnerability (5) 50 Warning time: Hours to days

Maximum Threat (10) 100 Major contributor(s):

Topographic characteristics, terrain, development and

construction practices, and water saturation



30 days or more


LANDSLIDE HAZARD PROFILE (continued) stable land. According to a study of the February 1996 storm, changes to slopes through cutting or filling increased the risk of landslides in 76 percent for the inventoried landslide areas in the Metro region (Burns and others 1998). The study also found that there are four dominant landslide areas: the West Hills Silt Soil Province; the debris flows in the Valley Bottoms Province along the Columbia River; the steep bluffs along Rivers Province on the Willamette and Clackamas Rivers, and the fine-grained Troutdale Formation Province (which was not analyzed for this pilot study). It is important to note that hazard maps only provide a general indication of landslide hazards. Figure 3-4 shows the dominant landslide hazard areas in the Portland study area as well as the locations of the 1996 landslides.

Table 3-1. Historic Landslides for Portland (1996-2002) (DOGAMI 2002b)

Historic Landslide Type Number of Occurrences In the City of Portland

Debris Flow 13 Debris Slide 56 Earth Flow 168

Earth Flow / Debris Flow 3 Earth Flow / Rockfall 1

Rockfall 11 Rockfall / Earth Flow 2 Rockfall / Mudflow 1

Slump 49 Slump – Earth Flow 89

Slump – Earth Flow / Debris 7 Slump – Earth Flow / Rockfall 1

Slump / Debris Flow 1 Translational (horizontal movement) 1

N

0 2 4

miles

1996 LandslideOccurrence

Landslide AreasDebris Flows In Valley BottomsSteep Bluffs Along The RiversWest (Portland) Hills Silt Soils

Figure 3-4. Landslide Hazard Areas for Portland Study Area and 1996 Landslide Locations


Wildland Fire

WILDLAND FIRE PROFILE

Background and Local Conditions Fire is a natural part of the ecosystem and plays an important role in shaping the environment. Wildland fires generally occur heavily wooded areas but can also impact metropolitan areas; for example, these fires occur at the interface of wooded and brush areas and developed areas. These fires can be triggered by fires in the home, fires resulting from industrial activities, fires resulting from natural hazards (for example, fires associated with lightning strikes), and other events. This hazard profile considers wildland fires in the Portland study area. Historic Frequency and Probability of Occurrence Wildland fires can occur at any time of the year but are especially likely during hot, arid periods. The probability of occurrence is high, with an occurrence probable each year. Specific historic or probable frequency data are not available for the Portland wildland fire hazard. Severity The risk of impact of major wildland interface fires can be high. Wildland fire events can cause multiple deaths, completely shut down facilities, and cause more than 25 percent of affected properties to be destroyed or suffer major damage. Historic Losses and Impacts To date, there have been no major losses due to wildland fires in the Portland study area since records have been kept. Thus, while the area has been spared the impacts of fires, it is prudent to expect that such a fire represents a threat and could occur in the Portland area (Metro 1999). While no specific events have impacted Portland a number of significant wildfires occurred during 2002 and 2003 in the national forests (Deschutes and Ochoco) west and south of Portland. These necessitated road closures on Highway 20. The recent severe wildland fires and subsequent landslides in Southern California (2003) illustrate the danger that is associated with this hazard. Designated Hazard Areas Residences have long occupied the heavily forested hillsides around Portland, and the trend of locating near undeveloped land continues to increase interface areas that in turn intensify the potential impacts of wildland fires and may increase ignition sources. Structures built in interface areas may be more vulnerable to wildland fires. Approximately 30 square miles of the 145 total square miles in the Portland study area (or 20 percent) is at risk from the wildland fire hazard. Figure 3-5 shows the at-risk regions within the Portland study area. These areas are considered to be at risk because of fuel types, vegetation, and slope characteristics. The figure shows that the western and southwestern regions of the Portland study area are at greatest risk from wildland fires.


Severity Score High Period of occurrence: Any time, particularly summer or fall

History (2) 12 Probability of event(s): Highly likely

Vulnerability (5) 35 Warning time: 0 to 3 hours

Maximum Threat (10) 100 Major contributor(s):

Lightning or human activities resulting in fire, fuel type and condition, vegetation, and slope



14 days or more

Interface is used to describe areas where

homes and other structures have been

built on, or adjacent to, forest and range lands. It is an intermingling of

built structures with natural cover at various degrees of growth and

complexity.


WildfireThreat

N

Portland Area = 144.8 square miles

Area at Risk from Wildfires = 29.9

0 2 4

miles

Figure 3-5. Areas at Risk from Wildland Fire Hazard


INVENTORY OF ASSETS 4

This section describes the “inventory of assets” data used for this risk assessment.

Because Portland has strong, local Geographic Information System (GIS) data, local building data were collected and evaluated to support a partial Level 2 analysis. HAZUS-MH provided data was supplemented with local data for specific categories of inventory. The local inventory data collected from Metro’s Regional Land Information System (RLIS) (Metro-RLIS 2002) were consistent with tax lot information and were determined to be complete and accurate for use in HAZUS-MH. Local data were used to help classify and update HAZUS-MH data for critical facilities, transportation lifeline facilities, and utility lifeline facilities. HAZUS-MH provided data were used to estimate general occupancy inventory because those data were determined to have more consistent and reliable square-foot estimates.

Appendix 2 to this risk assessment report, Data Summary, provides a summary of the data collection efforts conducted for the Portland pilot project. Where available, both spatial and non-spatial local data were gathered, compiled, and analyzed. In addition to local inventory data, local GIS data also assisted Level 2 hazard modeling (as discussed in Section 5.0, Loss Estimates).

Inventory data for Portland are discussed under the following categories: (1) population, (2) general building stock (aggregate inventory), and (3) critical facilities (site-specific inventory).

The inventory of assets considers, What can be lost when a disaster occurs? –

that is, what community resources are at risk? Assets include people,

buildings, transportation systems, and other valued

community resources.


Figure 4-1. Distribution of General Population by Census Tract

Population. The 2001 population of the City of Portland was 536,240 (Portland Development Commission 2003a). After a comparison of this total to the HAZUS-MH provided data, which estimates a population of 542,608, it was determined that HAZUS-MH population data would be used without modification. Because the two totals are similar, using the HAZUS-MH provided data would not affect the quality of the results. The HAZUS-MH estimates are slightly higher because of how the study area was defined (see Section 2.0, Identification of Hazards). Figure 4-1 shows the distribution of the general population for Portland by census tract.

N

0 2 4

miles

Population Density[per square mile]

10,000 and Over5,000 to 9,9991,000 to 4,999

500 to 999Less than 500

In 2000, the per capita income in the Portland/Vancouver PMSA was $33,947, and the median family income for the same period was $53,700. The median household income for Multnomah County was $41,278 in 2000 (Oregon Natural Hazards Workgroup 2003). As of 2000, there were 229,333 households in the City of Portland (Metro-RLIS 2002), or an average of 2.37 individuals per household based on a population estimate of 542,608. Today, about 21 percent of Multnomah County’s population is defined as minority (Oregon Natural Hazards Workgroup 2003).

DMA 2000 requires that social vulnerabilities be analyzed to consider those people that may be subject to disproportionate impacts. Vulnerable populations are considered to be most susceptible to hazards based on a number of factors, including their physical and financial ability to react or respond during a hazard and the location and construction quality of their housing. Based on HAZUS-MH data, the vulnerable populations in the City of Portland evaluated for the purposes of this pilot project include the following:


Figure 4-2. Distribution of Low Income Population by Census Tract

Figure 4-3. Distribution of Elderly Population by Census Tract

? Low Income - 50,937 households with an annual income of less than $20,000 (22.2 percent of the population). Based on an average of 2.37 persons per household, this represents 120,721 low income persons.

? Elderly – 62,931 elderly persons (65 years or older) living in the city (11.6 percent of the total population).

The low income and elderly populations are not mutually exclusive and may include individuals that appear in both categories. For the purposes of this pilot project, such overlap is not considered. Figures 4-2 and 4-3 illustrate the distribution of low income and elderly populations in the Portland study area, respectively.

N

0 2 4

miles

Low Income HouseholdsDensity Map [per square mile]

2,000 and over1,000 to 1,999

500 to 999100 to 499

Less than 100

N

0 2 4

miles

Elderly Population DensityMap [per square mile]

2,000 and Over1,000 to 1,999

500 to 999100 to 499

Less than 100


Figure 4-5. Change in the Share of County Population for the Portland/Vancouver PMSA (Metro-RLIS 2002)

Changes in population and development over time can increase the potential impacts associated with hazards and affect how agencies prepare for and respond to disaster. Therefore, DMA 2000 requires an analysis of development trends. Figure 4-4 illustrates the annual population change by county in the Portland/Vancouver PMSA from 1991 to 2001. The figure shows that since 1991, the regional population has exhibited a positive growth pattern. Multnomah County has grown between 5,000 and 10,000 persons annually, or about 13 percent over the 10-year period.

Figure 4-5 illustrates each county’s share of the total population for the Portland/Vancouver PMSA for 1970 and 2000. The figure shows that suburban county growth in Washington, Yamhill, Clackamas, Clark, and Columbia Counties has been greater than population growth in urban, Multnomah County in the last 30 years. Therefore, Multnomah’s percentage of the total regional population has decreased from 51 to 35 percent.

Figure 4-4. Annual Population Change by County for the Portland/Vancouver PMSA (Metro-RLIS 2002)

Washington 23%

2000 Population (1,918,009)

Washington 15%

Yamhill 4% Yamhill 4%

1970 Population (1,078,100)

Clackamas 15%

Clackamas 18%

Clark 12%

Clark 18%

Columbia 2%

Columbia 3%

Multnomah 51%

Multnomah 35%


General Building Stock. Metro-RLIS data were used to develop a detailed inventory of Portland’s built environment and included the following attribute data for buildings:

? Name of facility ? Exact location ? Year built ? Replacement value ? Number of stories/floors ? Square footage

After the participating agencies reviewed these data, they determined to use HAZUS-MH provided data for general building stock. HAZUS-MH provided data for general inventory and occupancy were determined to have more reliable square-foot estimates. The industrial occupancy class is not evaluated in this pilot project risk assessment because it is not required under DMA 2000 and because site-specific data were not available at the time this report was prepared.

For additional detail related to the data attributes, refer to Appendix 2, Data Summary. Portland will continue to collect additional attribute data for buildings to support many planning efforts, including future HAZUS-MH analysis. Local building data efforts are facilitated by the use of the building information tool (BIT) provided with HAZUS-MH.

Table 4-1 presents the estimated number of buildings and dollar value for these buildings by occupancy class for Portland. Exposure values are based on the data provided with HAZUS-MH (FEMA 2003b). Values shown include average building values, structural values (replacement costs), “content value,” and total value. The total inventory value for residential and commercial buildings is $59 billion.

Table 4-1. Inventory of General Building Stock

Building Occupancy

Class

Number of Buildings

Average Building Value

Estimated Replacement

Cost

Estimated Content Value

Data Source

Residential

171, 041 occupancies

(159,488 single

family dwellings)

$184,000

($146,000 for single family dwellings)

$31.4B

($23.3 B for single family dwellings)

$15.7B

($11.7 B for single family dwellings)

FEMA 2003b

Commercial 2,867 $2,014,000 $5.8B $6.1B FEMA 2003b

Total 173,908 N/A $37.2B $21.8B FEMA 2003b

Notes: Single family dwellings are a subset of the total residential occupancy class. Dollar values are rounded to the nearest hundred million or nearest hundred thousand, as appropriate. Total values include the sum of residential and commercial occupancy classes. B indicates billion. N/A indicates not applicable.

In addition to the number and distribution of residential structures, the construction date is also an important consideration for hazard mitigation

Content value includes all of the

items in a building, excluding the

structure itself. The values are modeled in the HAZUS-MH

provided data. Generally, content

value is estimated to be 50 percent of the residential structural replacement value and 100 percent of

the commercial building replacement

value.


because older homes are generally at greater risk of damage. For Multnomah County, approximately 53 percent of homes were built before 1959, 27 percent between 1960 and 1979, and the remaining 20 percent between 1980 and 2000 (Oregon Natural Hazards Workgroup 2003).

Distribution maps can help communities evaluate areas of the city in relation to specific hazards. For example, areas of heavy or planned development can be overlain with flood zones to see if areas of high exposure are present or may occur if further development is approved. The distribution of residential buildings is not illustrated in a separate figure because the distribution of residential structures is almost 100 percent correlated with the population density, as shown on Figure 4-1. Figure 4-6 shows the distribution of buildings and exposure density for the commercial occupancy category. The commercial occupancy class exposure tends to be scattered, with an area of concentration along the Columbia River.

N

0 2 4

miles

Commercial Building ExposureDensity [per square mile]

$20M and Over10 to 19.95 to 9.91 to 4.9

Less than $1M

Infrastructure at Risk. The infrastructure exposed or “at risk” in Portland includes critical facilities, transportation lifeline systems, and utility lifeline systems, as shown in Table 4-2.

Infrastructure facilities including schools, police and fire stations, and hospitals, are known as “critical facilities.” Lifeline systems are separated into distinct classes that have substantially different damage and loss characteristics. The two lifeline classes are (1) transportation systems (bridges, key roads, railway tracks, and light rail) and (2) utility lifelines (potable water treatment plants, wastewater treatment plants, electric power substations, potable water pipelines, sewer pipelines, natural gas pipelines, and oil pipelines).

Figure 4-6. Distribution of Commercial Building Stock Exposure Density

At-risk exposure values include the entire building inventory value in census blocks that lie within, or

bordering, the hazard areas (that is, generally within the

hazard areas).

Willamette River

Columbia River


Data on hazardous material sites were collected from the Portland Fire Department, Metro-RLIS, and HAZUS-MH provided data and were reviewed to evaluate exposure. Data supplied by the Fire Department provided information on the most common types of chemicals and the spatial distribution of chemical use and storage facilities throughout the Portland study area; however, upon review, it was noted that these data were too detailed and included many, smaller facilities. The Metro-RLIS data, which identified 263 facilities, were selected for estimating inventory because the Metro-RLIS inventory represented local data for the larger facilities and was considered to be current data. It was determined that hazardous materials site exposure could be modeled using this smaller subset because these facilities were larger and considered to pose the greatest risk.

Table 4-2 provides available transportation infrastructure data for the Portland study area. Multnomah County has 333 state highway bridges, 44 county bridges, 126 city/municipal highway bridges, and 1 historical covered bridge, for a total of 504 bridges. There are 647 bridges in the footprint of the Portland study area. The Portland/Vancouver PMSA’s major expressway is Interstate 5, which runs north-south through the region. Other state highways in the region include Interstate 84 and Highway 30, which intersect in Portland; Interstate 205, which runs through Multnomah and Clackamas Counties; and US Highway 26, which intersects US Highway 101 in Clatsop County. A network of state, county, and city roads also traverse the region (Oregon Natural Hazards Workgroup 2003).

Due to heightened security concerns, local utility data sufficient to complete the analysis were not obtained. Utility system data that were available

Table 4-2. Inventory of Infrastructure Facilities (Metro-RLIS 2002)

Facility Class Facility Count Critical Facilities Schools (K-12) 167 Hospitals 10 Fire Stations 33 Police Stations 10 Hazardous Material Sites* 263

Transportation Lifeline Systems Bridges (railway/highway) 647 Key Roads (in miles) 210 Railway Tracks (in miles) 150 Light Rail (in miles) 15 Utility Lifeline Systems Potable Water Treatment Plants 11 Wastewater Treatment Plants 1 Electric Power Substations 1,030 Potable Water Pipelines (in miles) 124 Sewers (in miles) 307 Natural Gas Pipelines (in miles) 83 Oil Pipelines (in miles) 9

HAZUS-MH asset data also address infrastructure, which includes critical facilities and

lifelines deemed to be of significant importance (see

definitions, Appendix 1). Critical facilities include

schools, hospitals, fire stations, and police stations.

Lifelines include transportation systems

(airways, bridges, roads, tunnels and waterways) and

utility systems (potable water, wastewater, oil,

natural gas, electric power facilities and communication

systems).

Note: K-12 indicates kindergarten through high school. *Hazardous material sites are shown above with critical facilities but are a separate inventory category in HAZUS-MH.


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N

Hazardous Materials Site

CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCFire Station

Hospital

School

Police Station

0 2 4

miles

through HAZUS-MH were not considered sufficient to support accurate loss estimates; for example, data on the age and construction of utility lifelines were not consistently available. Therefore, these data were not used in the loss estimates presented in this report; however, the utility system data was determined to be sufficient to estimate exposure.

There is one major airport at risk in the Portland study area. In addition, there are several high-hazard reservoirs that are part of the Portland inventory; no major dams are included in this study. Figure 4-7 illustrates the locations of several categories of critical facilities in the study area.

Figures 4-8 and 4-9 illustrate the locations of the transportation and utility lifeline systems in the study area, respectively.

Figure 4-7. Distribution of Critical Facilities


Figure 4-8. Transportation Lifelines

N

0 2 4

miles

Key

Major HighwayKey RoadwayLight Rail TrackRailway Track

N

0 2 4

miles

Pipe TypeOilGasWaterSewer

Figure 4-9. Utility Lifelines


Because the number of infrastructure facilities exposed was considered of primary importance for planning purposes (rather than loss value), exposure values were not calculated for these facilities for the pilot project. Therefore, critical facilities are evaluated based on the number of buildings, facilities, or miles that could be affected. In some cases the potential degree of impact also is estimated (see Section 5.0, Loss Estimates). The City of Portland will continue to collect additional attribute data for these and other lifeline facilities to assist with the development of detailed dollar exposure values for these infrastructure facilities in the future.


LOSS ESTIMATES 5

This section of the risk assessment presents the “estimate of losses,” including: exposure, damage, and loss estimates analyzed on a hazard-by-hazard basis. The findings support local and regional planners’ understanding of the potential impacts of each hazard and enable a comparison of hazards by quantifying potential exposures impacts.

For this portion of the risk assessment, available data, methodologies, and assumptions were used to select and apply a risk assessment methodology for each hazard. Table 5-1 shows the risk assessment methodologies selected for each hazard. The two methodologies are described in Section 1.0, Introduction.

Table 5-1. Summary of Risk Assessment Methodology Selection

Hazard Output HAZUS-MH Methodology

Earthquake

Flood HAZUS-MH Exposure and Loss Estimates

HAZUS-MH Supported Methodology

Landslide

Wildland Fire HAZUS-MH Supported Exposure Estimate

For each hazard, the following data are provided with the loss estimate: (2) risk assessment data used, (2) hazard methodology and assumptions, and (3) estimated damages and losses.

When sufficient data are available to estimate the frequency and severity of a potential hazard (as is the case with earthquake and flood), annualized losses can be computed. If historical or simulation data are insufficient, the ability to estimate frequency and severity in a reliable manner is limited. Therefore, where those data are not available (as for the landslide and wildland fire hazards), annualized losses cannot be computed. For these hazards, exposure estimates were calculated using local hazard data and HAZUS-MH and local inventory data. Additional follow-up study would be required to develop in-depth estimates of hazard frequency and severity to calculate loss estimates for these hazards.

DMA 2000 requires risk to be assessed qualitatively (such as high, medium, or low) and recommends quantitative assessment. For this pilot project, loss or exposure estimates are presented in a quantitative manner. For example, the number of buildings impacted. For buildings, the impact is also shown as a loss or exposure ratio (facilities at risk compared with the total facility universe). These values are then used to express relative risk as shown in Table 5-2.

The estimate of losses considers how

community assets will be impacted by hazard

events. For each hazard, the appropriate

risk assessment methodology, risk

scenario, inventory, and hazard data are used to

estimate losses.


Table 5-2. Summary of Risk Categories for Critical Facilities






For hazards analyzed using exposure estimates (HAZUS-MH supported risk assessment methodology), the population at risk is shown (for landslide and wildland fire); the population that is potentially exposed, or at risk, is estimated using HAZUS-MH inventory data and the locally derived hazard maps. However, injury and casualty data are not estimated for these hazards because data were insufficient.

Where population loss estimates are provided, socially vulnerable populations are also indicated. These populations include persons over 65 years of age (elderly persons) and those persons from households with an annual income of less than $20,000 (low income). These persons may be unduly impacted by hazards based on the construction of their homes, their personal physical condition, or their financial capability to respond to hazard damages.

For critical facilities, transportation lifeline systems, and utility lifeline systems, the number of facilities impacted or exposed is estimated. Dollar value loss estimates for infrastructure were not calculated for this pilot project because accurate valuations of these facilities were not available to the project team. However, it would be possible to use the loss or exposure ratios provided in this analysis to derive or calculate dollar loss estimates if facility valuations become available.

Although, indirect economic loss estimates are not required for DMA 2000 compliance, indirect economic losses are useful in evaluating hazards and can be calculated for HAZUS-MH hazards. Indirect economic losses typically represent less than 10 percent of the total economic loss estimates and represent long-term costs. Given the project schedule and pilot project resources, results for indirect economic losses are not presented.

Note: The colors shading illustrate increasing risk from no or limited risk (green) to high to severe risk (red).


Earthquake

The earthquake hazard loss estimate analysis is presented below. The HAZUS-MH earthquake model was used to evaluate this hazard.

HAZUS-MH does not include local soil liquefaction or soil type data; a Level 1 analysis assumes liquefaction is not a concern and assumes a soil type. For this pilot project, local soil and liquefaction data were available locally and were incorporated (Metro-RLIS 2002 and DOGAMI 2002). This supports a refined modeling of the potential affects of the earthquake hazard based on the effect that soil type has on ground shaking amplification. Liquefaction data also helps refine the analysis for ground failure. HAZUS-MH provided inventory data were modified with updated local critical facilities and lifelines information. Population data were taken from HAZUS-MH and are based on the most recent census conducted in 2000 (FEMA 2003b).

The HAZUS-MH earthquake model provides loss estimates for general building stock and estimates how much of the at-risk infrastructure would be affected by the hazard. The earthquake module also estimates affected population, including displaced households, shelter requirements, and injuries. Mean return period (MRP) and annualized losses were estimated for this hazard.

The widespread, regional nature of the earthquake hazard means that the entire Portland population is estimated to be at risk. Therefore, exposure values for number of households, general population, and socially vulnerable populations are not evaluated. However, estimated social impacts such as displaced households, shelter requirements, and injury were estimated and are summarized in Table 5-3 for the 100- and 500-year MRP events.

Table 5-3. Estimated Social Impacts from Earthquake

Social Loss Parameter 100-year Earthquake 500-year Earthquake

Expected Displaced Households 1,500 to 2,000 7,500 to 8,000 Expected Persons Requiring Shelter 900 to 1,200 4,700 to 5,000

Expected Minor Injuries 2,000 to 2,500 8,000 to 8,500 Expected Major Injuries and Fatalities 150 to 200 800 to 900

Note: Figures rounded to the nearest hundred. Major injuries are those that require hospitalization.

Figure 5-1 shows the extent of the earthquake hazard in relation to the population density to illustrate areas of the city where greater numbers of people likely would be exposed.

The mean return period (MRP) is the average

period of time, in years, between occurrences of a

particular hazard event with a given severity.

Mean return period and annualized loss scenarios are probabilistic because

they evaluate events based on the probability of

their occurrence.

One might expect that the number of persons requiring shelter would be greater than number of displaced households because more than one

person lives in each household. However, some individuals from

displaced households do not require shelter

because they stay with friends or family or

choose to stay at a hotel.


Figures 5-2 and 5-3 illustrate the distribution of elderly and low-income populations (socially vulnerable populations) in relation to the earthquake hazard.

Figure 5-2. Distribution of Elderly Population Density in Relation to the Earthquake Hazard

Figure 5-1. Distribution of General Population Density in Relation to the Earthquake Hazard

Soft Soil Areas -Higher Ground

Shaking Amplification

N

0 2 4

miles


2,000 and Over1,000 to 1,999

500 to 999100 to 499

Less than 100



N

0 2 4

miles


10,000 and Over5,000 to 9,9991,000 to 4,999



Estimated property damage and loss ratios are summarized in Table 5-4 for residential and commercial classes for the 100- and 500-year MRP events. Damage estimates reflect the cumulative estimated loss based on impacts to individual buildings.

Table 5-4. Estimated Damages/Losses to General Building Stock from Earthquake

100-year Earthquake 500-year Earthquake Occupancy Class Estimated

Damages Economic Loss Ratio

Estimated Damages

Economic Loss Ratio

Residential Structures $500.2 M 1.59% $2,223.7 M 15.6% Residential Building Contents $157.1 M 1.00% $660.3 M 4.21%

Total Residential $657.3 M 1.40% $2,984.0 M 6.34%

Commercial Structures $349.4 M 6.05% $1,101.2 M 19.07% Commercial Building Content $122.7 M 2.02% $284.1 M 4.67%

Total Commercial $472.1 M 3.98% $1,385.3 M 11.68%

Total $1,129.4 M 1.9% $4,369.3 M 7.4% Notes: M indicates millions. Dollars rounded to the nearest hundred thousand.

The total estimated loss for an earthquake with a severity equal to a 500-year MRP is approximately $4.4 billion. Residential buildings account for about 68 percent of the total losses for this event. Because of differences in building construction, residential structures are more susceptible to damage from earthquakes than commercial and industrial structures.

“Annualized loss” estimates consider all potential future hazard events and estimate the average annual loss that can be expected based on the individual events that may occur over time. The total estimated average annualized loss

The economic loss ratio is the estimated value of the loss divided by the

total inventory value. This represents the percent of the total exposed value

that likely would be incurred to repair or

restore inventory to its original, pre-hazard state.

Qualitative categories describing the relative

magnitude of the economic loss are

described on Page 28.

Figure 5-3. Distribution of Low-Income Population Density in Relation to the Earthquake Hazard



N

0 2 4

miles


2,000 and Over1,000 to 1,999

500 to 999100 to 499

Less than 100


associated with earthquakes is $29.7 million. The average annualized loss by occupancy class associated with the earthquake hazard is presented below.

§ Total losses of $19.9 million for residential occupancy class, or an annualized loss ratio of 0.04 percent, including:

o $15.6 million for residential structures, or an annualized loss ratio of 0.05 percent

o $4.3 million for content loss for residential occupancy class, or an annualized loss ratio of 0.03 percent

§ Total losses of $9.8 million for commercial occupancy class or, an annualized loss ratio of 0.08 percent, including:

o $7.7 million for commercial structures, or an annualized loss ratio of 0.13 percent

o $2.1 million for content loss for commercial occupancy class, or an annualized loss ratio of 0.03 percent

Figures 5-4 and 5-5 show the dollar loss density of 500-year loss estimates for the earthquake hazard for both the residential and commercial occupancy classes. The dollar loss density indicates the loss in dollars per square mile of land.

Figure 5-4. Residential Dollar Loss Density for 500-Year Earthquake Event

Annualized loss is the estimated long-term value

of losses to the general building stock averaged on an annual basis for a

specific hazard type. Annualized loss considers

all future losses for a specific hazard type

resulting from possible hazard events with

different magnitudes and return periods, averaged

on a “per year” basis. Like other loss estimates,

annualized loss is an estimate based on available data and

models. Therefore, the actual loss in any given

year can be substantially higher or lower than the

estimated annualized loss.

N

0 2 4

miles

Residential Loss Density[x $1,000 per square mile]

100,000 and Over50,000 to 99,99925,000 to 49,99910,000 to 24,999

Less than 10,000


N

0 2 4

miles

Commercial Loss Density[x $1,000 per square mile]

100,000 and Over50,000 to 99,99925,000 to 49,99910,000 to 24,999

Less than 10,000

Table 5-5 presents the exposure for critical facilities associated with the earthquake hazard for a 100-year MRP earthquake. The number of facilities at risk for damage categorized from no damage to complete loss is shown. The economic loss ratio indicates the percent of the total value expected to be lost.

Table 5-6 presents the exposure for critical facilities associated with the earthquake hazard for a 500-year earthquake.

As shown in the Tables 5-5 and 5-6, the loss ratio is anticipated to be limited for the 100-year MRP earthquake and moderate for the 500-year MRP earthquake event.

Table 5-5. Critical Facility Infrastructure at Risk from a 100-Year Earthquake Event

Facility Class No

Damage Slight

Damage Moderate Damage

Extensive Damage

Complete Damage

Economic Loss Ratio

Schools (K-12) 131 16 14 4 2 2.7% Hospitals 7 1 1 0 0 3.9% Fire Stations 25 3 3 1 1 4.3% Police Stations 8 1 1 0 0 3.2%

Table 5-6. Critical Facility Infrastructure at Risk from a 500-Year Earthquake Event

Facility Class No

Damage Slight


Extensive Damage

Complete Damage

Economic Loss Ratio

Schools (K-12) 57 40 41 18 10 11.6% Hospitals 4 2 3 1 0 13.4% Fire Stations 10 6 8 5 3 16.1% Police Stations 3 3 3 1 1 12.4%

Figure 5-5. Commercial Dollar Loss Density for 500-Year Earthquake Event

The HAZUS-MH User Manual describes the categories of

damage for different occupancy classes.


Note: PGA indicates peak ground acceleration. “g” indicates gravitational acceleration.

Table 5-7 presents the potential impact to hazardous materials sites associated with various PGA ranges caused by potential earthquakes in Portland. This table was generated by mapping hazardous materials sites falling within different ground shaking potential hazard areas. Professional judgment was used to estimate the level of action required following an earthquake (i.e., “may need inspection”). In the case of the 100-year MRP earthquake, spills are not expected; however spills are predicted for a 500-year MRP earthquake.

Tables 5-8 and 5-9 present the estimated impacts to transportation and utility lifeline systems, respectively, for the 100- and 500-year MRP earthquakes events. For each category, the miles “at risk” are the total miles in the study region. Table 5-8. Estimated Damage to Transportation Lifeline Systems from an Earthquake

100-year Earthquake 500-year Earthquake Transportation Lifeline Systems

At Risk Expected Damages At Risk Expected

Damages Key Roads 40.4 miles 0.4 miles 40.4 miles 6.7 miles

Railway Tracks 79.3 miles 1.1 miles 79.3 miles 14.7 miles

Light Rail 15 miles 0.01 miles 15 miles 0.2 miles Table 5-9. Estimated Damage to Utility Lifeline Systems from an Earthquake

100-year Earthquake 500-year Earthquake Utility Lifeline Systems

At Risk Expected Damages At Risk Expected

Damages Potable Water Pipelines 12.2 miles 0.47 miles 12.2 miles 6.8 miles

Sewers 75.5 miles 2.9 miles 75.5 miles 2.9 miles

Natural Gas Pipelines 25.1 miles 1.0 miles 25.1 miles 13.8 miles

Oil Pipelines 5.4 miles 0.24 miles 5.4 miles 3.1 miles

Table 5-10 presents the estimated damages to special infrastructure facilities, such as bridges, electric substations, and water and sewer treatment plants, associated with the 100-year MRP earthquake.

Table 5-7. Estimated Damage to Hazardous Materials Sites from PGA-specific Earthquakes

PGA Range (g)

0 to 0.1 0.1 to 0.2 0.2 to 0.3 >0.3 Event

No Damage Expected

May Need Inspection

Slight Damage Expected

Significant Damage Expected

Number of Hazardous Materials Sites

(100-year Event) 32 231 0 0

Number of Hazardous Materials Sites

(500-year Event) 0 18 130 115


Table 5-11 presents the estimated damages to special infrastructure facilities, such as bridges, electric substations, and water and sewer treatment plants, associated with the 500-year MRP earthquake.

Figures 5-6, 5-7, and 5-8 illustrate at-risk critical facilities, transportation lifeline systems, and utility lifeline systems with respect to the earthquake hazard based on soil type and liquefaction potential. Transportation and utility lifeline systems are overlain with liquefaction potential maps because major damage for these systems typically occurs in these areas.

Table 5-10. Estimated Damages for Other Lifeline Facilities from a 100-year Earthquake

Facility Class No

Damage Slight


Extensive Damage

Complete Damage

Economic Loss Ratio

Bridges 647 0 0 0 0 0.0% Potable Water and Wastewater Treatment Plants

9 1 1 1 0 6.3%

Electric Power Substations 440 225 212 149 5 8.6%

Table 5-11. Estimated Damages for Other Lifeline Facilities from a 500-year Earthquake

Facility Class No

Damage Slight


Extensive Damage

Complete Damage

Economic Loss Ratio

Bridges 470 126 30 19 3 2.3% Potable Water and Wastewater Treatment Plants

4 2 3 2 1 15.4%

Electric Power Substations

41 67 108 707 108 36.0%

Figure 5-6. Distribution of Critical Facilities in Relation to the Earthquake Hazard Based on Soil Type


CCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCCC







N



HospitalSchool

Police Station

0 2 4

miles


Figure 5-7. Distribution of Transportation Lifeline Systems in Relation to the Earthquake Hazard Based on Soil Liquefaction Potential

Figure 5-8. Distribution of Utility Lifeline Systems in Relation to the Earthquake Hazard Based on Soil Liquefaction Potential

N

0 2 4

miles

Pipe Type

OilGasWaterSewer

LiquefactionPotentialVery LowLowMediumHighVery High

N

0 2 4

miles

Key

HighwayKey RoadLight RailRail Track

LiquefactionPotential

Very LowLowMediumHighVery High


Flood

The flood hazard loss estimate analysis is presented below.

Input data collected for the flood hazard includes local damage data from historical flood events and FEMA Q3 flood zone data, which delineate the 100- and 500-year flood plain boundaries. Metro-RLIS also provided 100-year and 500-year flood maps. In addition, creek data were provided but were determined to be too localized to provide study area-wide coverage. HAZUS-MH provided inventory data were modified with updated local critical facilities and lifelines information. Population data were taken from HAZUS-MH and are based on the most recent census conducted in 2000 (FEMA 2003b). Portland is in the process of updating and refining its Q3 data but it the updates were not available at the time of the pilot project. Therefore, FEMA Q3 flood zone data were identified as the most comprehensive “flood polygon” data for the study region. To support the use of HAZUS-MH and study area coverage, the modeling approach used Q3 flood zone flood polygon data. U.S. Geologic Survey (USGS) Digital Elevation Model (DEM) data were used as the base elevation.

The HAZUS-MH methodology was customized to analyze the flood hazard. An automated computer query or command series, known as a “macro,” is available as a complement to HAZUS-MH. The macro approach to flood hazard analysis has been tested and typically estimates results with only a 10 to 15 percent margin of error compared to the Level 2 analysis using the HAZUS-MH model. The flood macro is a third-party model and complement to the HAZUS-MH software package and was specifically designed for these pilot projects and to support communities in addressing the requirements of DMA 2000. It supports analyses for larger areas and can provide a first estimate to support further, detailed study of particular stream reaches using the HAZUS-MH flood model. The flood macro was used to estimate flood impacts at the study area level. Losses were estimated for a 100- and a 500-year MRP flood event. Losses also were estimated on an annualized basis. The 11 residential and 10 commercial occupancy classes traditionally used by HAZUS-MH were condensed into two occupancy classes (residential and commercial) to facilitate the analysis.

In addition, impacts to critical facilities were evaluated for the 100-year and 500-year MRP events. Indirect losses were not addressed as part of this pilot project. Although HAZUS-MH can provide indirect loss estimates for commercial and industrial occupancy classes, those damages are estimated to represent less than 10 percent of the overall losses and were therefore not considered significant to the final estimates for flood. While HAZUS-MH supports injury and casualty analyses for the flood hazard, injuries and casualties are typically negligible for this hazard because of the warning times associated with the flood hazard. Therefore, injuries and casualties were not estimated for this hazard. However, the population impacted by damages to buildings (potentially displaced persons) was estimated.

At-risk population includes residents living in buildings that lie within or bordering the inundation

areas. Estimated damages represent a sub-

set of the at-risk value.

A flood polygon is a GIS vector file outlining the area exposed to the flood hazard. HAZUS-MH

generates this polygon at the end of the flood computations in order to analyze the at-risk inventory.


Table 5-12 shows the total potential population estimated to be at risk for the two flood events evaluated.

Table 5-12. Estimated Population at Risk from Riverine Flood

100-year Flood 500-year Flood

Category Population within Flood

Zone

At-Risk Ratio

Population within Flood

Zone

At-Risk Ratio

Number of Households 11,200 4.9% 15,300 6.7% General Population 29,900 5.5% 38,400 7.1%

Population from Households with Income less than $20K 5,300 4.4% 8,700 7.2%

Elderly People (65 years old or more) 3,300 5.2% 4,000 6.3% Notes: For the low-income category, households are assumed to include 2.37 persons. The model does not address potential overlap in the socially vulnerable (low-income and elderly) categories; however, this impact is expected to be minor. Population numbers rounded to the nearest hundred.

Figure 5-9 shows the extent of the 500-year flood zone in relation to the population density to illustrate areas of the city where populations could be most impacted. Figures 5-10 and 5-11 show the population densities for elderly and low-income populations in relation to the 500-year flood zone, respectively.

500-yearFlood Extent

N

0 2 4

miles


10,000 and Over5,000 to 9,9991,000 to 4,999


Figure 5-9. Distribution of Population Density in Relation to 500-Year Flood Extent


Figure 5-11. Distribution of Low-Income Population Density in Relation to 500-Year Flood


N

0 2 4

miles


2,000 and Over1,000 to 1,999

500 to 999100 to 499

Less than 100


N

0 2 4

miles


2,000 and Over1,000 to 1,999

500 to 999100 to 499

Less than 100

Figure 5-10. Distribution of Elderly Population Density in Relation to 500-Year Flood


Displaced households and shelter requirements are not estimated by the HAZUS-MH flood macro. However, the full HAZUS-MH flood module could be used to estimate these. For this pilot project, the potential exposed or at-risk population is used as a surrogate measure of the potential maximum number of persons that may be displaced or require shelter during a flood. The total number of injuries and casualties resulting from flooding is generally limited because of the nature of the flood hazard and therefore, was not included in this study.

The total exposure value for buildings in the flood zone and considered to be at risk is summarized in Table 5-13 for both the 100-year and 500-year floods.

Table 5-13. Estimated Exposure Values for Structures at Risk from Floods

100-year Flood 500-year Flood Category At-Risk

Estimate At-Risk Ratio

At-Risk Estimate

At-Risk Ratio

Total Number of At-Risk Structures 9,739 5.6% 11,643 6.7%

Total Number of At-Risk Residential Structures

9,393 5.5% 11,083 6.5%

Residential Structure Exposure $1,634.7M 5.2% $2,247.3M 7.2% Residential Content Exposure $817.3M 5.2% $1,123.6M 7.2%

Total Residential Exposure $2,452.0M 5.2% 3,370.9M 7.2% Total Number of At-Risk Single

Family Dwelling Structures 8,006 5.0% 9,453 5.9%

Single-Family Dwelling Structure Exposure $1,140.0M 4.9% $1,354.4M 5.8%

Single Family Dwelling Content Exposure $570.0M 4.9% $677.2M 5.8%

Total Single Family Exposure $1,710.0M 4.9% $ 2,031.6 5.8% Total Number of At-Risk Commercial Structures 346 12.1% 560 19.5%

Commercial Structure Exposure $718.7M 12.4% $1,262.1M 21.9% Commercial Content Exposure $722.5M 11.9% $1,271.3M 20.9%

Total Commercial Exposure $1,441.2M 12.1% $2,533.4M 21.5%

Total Exposure $3,893.2M 6.6% $5,904.3M 10.6% Notes: Single-family dwellings are a subset of the total residential occupancy class. M indicates million. Dollars rounded to the nearest hundred thousand.

In Table 5-14 property damage due to the flood hazard is estimated by occupancy class. The total estimated loss for a 100-year MRP flood for the residential and commercial occupancy classes is about $258.7 million. The total expected loss for a 500-year MRP flood for residential and commercial occupancies is approximately $373.2 million. Residential losses account for approximately 60 percent of the total loss for both the 100- and 500-year MRP flood events. Building structure, content, and total loss estimates are shown. The damage counts include buildings damaged at all severity levels, from slight damage to total destruction; the total dollar damage estimates the impact to individual buildings at an aggregate level.


Table 5-14. Estimated Damages/Losses to General Building Stock from Floods

100-year Flood 500-year Flood Occupancy Class Estimated

Damages Economic Loss Ratio

Estimated Damages

Economic Loss Ratio

Residential Structure $98.2M 6.01% $134.4M 8.22% Residential Content $61.0M 7.46% $83.1M 10.16%

Total Residential $159.2M 6.49% $217.5M 8.87% Commercial Structure $20.8M 2.90% $29.5M 4.10% Commercial Content $78.7M 10.89% $126.2M 17.47%

Total Commercial $99.5M 6.90% $155.7M 10.80%

Total $258.7M 6.6% $373.2M 9.6% Notes: M indicates million. Dollars rounded to the nearest hundred thousand.

The total expected average annualized loss associated with riverine flooding for residential and commercial occupancy classes is $15.4 million. The average annualized loss by occupancy class associated with riverine flooding is as follows:

§ Total losses of $9.4 million for residential occupancy class, or an annualized loss ratio of 0.38 percent, including:

o $5.8 million for residential structures, or an annualized loss ratio of 0.36 percent

o $3.6 million for content loss for residential occupancy class, or an annualized loss ratio of 0.44 percent

§ Total losses of $6.0 million for commercial occupancy class, or an annualized loss ratio of 0.41 percent, including:

o $1.2 million for commercial structures, or an annualized loss ratio of 0.17 percent

o $4.7 million for content loss for commercial occupancy class, or an annualized loss ratio of 0.66 percent

Figures 5-12 and 5-13 show the dollar-loss density of annualized loss estimates for the flood hazard for the residential and commercial occupancy classes, respectively.


N

0 2 4

miles

Residential Loss Density[x $1,000 per square mile]

100,000 and Over50,000 to 99,99920,000 to 49,9995,000 to 19,999

Less than 5,000

Table 5-15 presents the critical facilities at risk for the 100- and 500-year MRP flood events.

Figure 5-12. Dollar Loss Density for Annualized Flood Losses for Residential Structures

Figure 5-13. Dollar Loss Density for Annualized Flood Losses for Commercial Structures

N

0 2 4

miles

Commercial Loss Density[x $1,000 per square mile]

100,000 and Over50,000 to 99,99920,000 to 49,999

5,000 to 19,999Less than 5,000


Notes: Values for segments are reported in miles, as appropriate. K-12 indicates kindergarten through high school.

The table shows that the city’s wastewater treatment plant is at risk for both flood events. The at-risk ratio for other facilities range from 0 to 23 percent for the 100- and 500-year MRP flood events. Figures 5-14, 5-15, and 5-16 illustrate the distribution of critical facilities, transportation lifeline systems, and utility lifeline systems, respectively, in relation to the 500-year, flood zone boundaries.

Table 5-15. Infrastructure at Risk from Riverine Flood

100-Year Flood 500-Year Flood

Facility Class Estimated Number of Structures

at Risk

At-Risk Ratio

Estimated Number of Structures

at Risk

At-Risk Ratio

Critical Facilities Schools (K-12) 0 0.0% 0 0.0% Hospitals 0 0.0% 1 10.0% Fire Stations 2 6.1% 5 15.2% Police Stations 0 0.0% 2 20.0% Hazardous Materials Sites 19 7.2% 61 23.2%

Transportation Lifeline Systems Bridges (railway/highway) 64 9.9% 112 17.3% Key Roads (in miles) 16 7.6% 37 17.6% Railway Tracks (in miles) 29 19.3% 45 30.0% Light Rail (in miles) 0.14 0.9% 0.84 5.6% Utility Lifeline Systems Potable Water Treatment Plants 0 0.0% 0 0.0% Wastewater Treatment Plants 1 100% 1 100% Electric Power Substations 80 7.8% 153 14.9% Potable Water Pipelines (in miles) 6.3 5.1% 8.3 6.7% Sewers (in miles) 25.2 8.2% 47.7 15.5% Natural Gas Pipelines (in miles) 3.3 4.0% 8.8 10.6% Oil Pipelines (in miles 0 0.0% 0.1 1.1%


Figure 5-14. Critical Facilities in Relation to the 500-Year Flood Zone

Figure 5-15. Transportation Lifeline Systems in Relation to the 500-Year Flood Zone

500-year

N

0 2 4

miles

Key










N



Hospital

School

Police Station

0 2 4

miles


Figure 5-16. Utility Lifeline Systems in Relation to the 500-Year Flood Zone

500-year

N

0 2 4

miles

Pipe Type

OilGasWaterSewer


Landslide

The landslide hazard loss estimate analysis is presented below. For this hazard, areas of landslide susceptibility were overlain with inventory data to estimate exposure, rather than loss.

Local expertise, GIS, and geologic data have been used to delineate three dominant landslide-prone hazard areas. The three dominant landslide-prone hazard areas were identified based on terrain information (slope and stability factors), geologic characteristics, and degrees of water saturation. DOGAMI provided these hazard area maps for use in the pilot project. They are the “debris flows in the valley bottoms,” “steep bluffs along rivers,” and “West (Portland) Hills silt soils.” HAZUS-MH provided inventory data were modified with updated local critical facilities and lifelines information. Population data were taken from HAZUS-MH and are based on the most recent census conducted in 2000 (FEMA 2003b).

For this pilot project, limited long-term historic hazard information with respect to frequency (recurrence) and impact of the landslide hazard led to the decision to use the HAZUS-MH-supported risk assessment approach. Therefore, annualized losses cannot be computed. Instead, separate, at-risk exposure values were assessed. The HAZUS-MH supported risk assessment method was developed using the inventory in HAZUS-MH supplemented with local data for critical facilities and hazard areas. Inventory data were superimposed over the hazard areas to enable GIS queries to estimate the quantity of assets at risk (population, structures, critical facilities, etc.).

Table 5-16 shows the population estimated to be at risk in the three primary landslide hazard areas.

Table 5-16. Estimated Population at Risk from Landslides

Category Debris Flows

in Valley Bottoms

Steep Bluffs Along Rivers

West (Portland)

Hills Silt Soils

Total at Risk

At-Risk Ratio

Number of Households 500 2,200 26,100 28,800 12.6% General Population 1,200 6,000 61,200 66,400 12.6%

Population from Households with Income

Less than $20K 200 1,100 7,500 8,800 7.3%

Elderly People (65 years old or more)

100 700 6,800 7,600 12.0%

Notes: For the low-income category, households are assumed to include 2.37 persons. The model does not address potential overlap in the socially vulnerable (low-income and elderly) categories; however, this impact is expected to be minor. Population numbers rounded to the nearest hundred.

Figure 5-17 shows the extent of the landslide hazard areas in relation to the population density. Figures 5-18 and 5-19 illustrate the socially vulnerable


Figure 5-17. Population Density in Relation to Landslide Hazard Areas

population densities for the elderly and low-income populations, respectively, in relation to the landslide hazard areas. The total population exposed to this hazard would be 66,400 (rounded to the nearest hundred persons). The socially vulnerable population exposed includes an estimated 8,777 persons living in households with annual household incomes of less than $20,000. It also includes 7,557 elderly persons (over the age of 65).

LandslidePotential

N

0 2 4

miles


2,000 and Over1,000 to 1,999

500 to 999100 to 499

Less than 100

Figure 5-18. Elderly Population Density in Relation to Landslide Hazard Areas

LandslidePotential

N

0 2 4

miles


10,000 and Over5,000 to 9,9991,000 to 4,999



Figure 5-19. Low-Income Population Density in Relation to Landslide Hazard Areas

LandslidePotential

N

0 2 4

miles


2,000 and Over1,000 to 1,999

500 to 999100 to 499

Less than 100

Table 5-17 summarizes building stock exposure for the landslide hazard.

Table 5-17. Estimated Exposure Values for Structures at Risk from Landslide Hazard

Category Debris Flows

in Valley Bottoms

Steep Bluffs Along Rivers

West (Portland) Hills Silt

Soils

Total at Risk At-Risk Ratio

Total At-Risk Structures 494 1,691 24,699 26,884 15.6% Number of At-Risk Residential

Structures 468 1,640 24,399 26,507 15.5%

Residential Structure Exposure $76.6M $356.8M $4,542.5M $4,975.9M 15.9%

Residential Content Exposure $38.3M $178.4M $2,271.2M $2,487.9M 15.9%

Total Residential Exposure $114.9M $535.2M $6,813.7M $7,463.8M 15.9%

At-Risk Single Family Dwellings 461 1,541 23,802 25,804 16.2% Single Family Dwelling Structure

Exposure $65.9M $220.7M $3,909.2M $4,195.8M 18.0%

Single Family Dwelling Content Exposure $32.9M $110.4M $1,954.6M $2,097.9M 18.0%

Total Single Family Dwelling Exposure $98.8M $331.1M $5,863.8M $6,293.7M 18.0%

At-Risk Commercial Structures 26 51 300 377 13.1% Commercial Structure Exposure $56.4M $112.5M $461.8M $630.7M 10.9% Commercial Content Exposure $56.5M $119.9M $547.0M $723.4M 11.9%

Total Commercial Exposure $112.9M $232.4M $1,008.80M $1,354.1M 11.5%

Total Exposure $227.8 $767.6M $7,822.5M $8,817.9M 14.9% Notes: Single-family dwellings are a subset of the total residential occupancy class. M indicates million. Dollars rounded to the nearest hundred thousand.


Table 5-18 presents the critical facilities, transportation lifelines, and utility lifelines at risk for the landslide hazard. For critical facilities, the total inventory located in all three landslide-prone areas is shown. As shown in the table, the loss estimates for the total number of facilities estimated to be impacted (from minor impacts to total destruction) are anticipated to range from no risk to severe for the landslide hazard.

Notes: Values for transportation and pipeline segments are reported in miles, as appropriate. K-12 indicates kindergarten through high school.

Figures 5-20, 5-21, and 5-22 illustrate the distribution of critical facilities, transportation lifeline systems, and utility lifeline systems, respectively, in relation to the landslide hazard areas.

Table 5-18. Infrastructure at Risk from Landslide

Facility Class Estimated Number of Structures at Risk At-Risk Ratio

Critical Facilities Schools (K-12) 16 9.6% Hospitals 3 30.0% Fire Stations 6 18.2% Police Stations 0 0.0% Haz Mat Sites 9 3.4%

Transportation Lifeline Systems Bridges (railway/highway) 71 11.0% Key Roads (in miles) 28 13.3% Railway Tracks (in miles) 13 8.7% Light Rail (in miles) 1.8 12.0% Utility Lifeline Systems Potable Water Treatment Plants 5 45.5% Wastewater Treatment Plants 0 0.0% Electric Power Substations 126 12.2% Potable Water Pipelines (in miles) 8.7 7.0% Sewers (in miles) 18.6 6.1% Natural Gas Pipelines (in miles) 6.6 8.1% Oil Pipelines (in miles 1.8 20.0%









LandslidePotential

N



HospitalSchool

Police Station

0 2 4

miles

Figure 5-20. Critical Facilities in Relation to Landslide Hazard Areas

Figure 5-21. Transportation Lifeline Systems in Relation to Landslide Hazard Areas

LandslidePotential

N

0 2 4

miles

Key



Figure 5-22. Utility Lifeline Systems in Relation to Landslide Hazard Areas

LandslidePotential

N

0 2 4

miles

Pipe Type

OilGasWaterSewer


Wildland Fire

The wildland fire hazard loss estimate analysis is presented below.

For this hazard, an approach was used to assume a reasonable area of impact based on factors associated with slopes, vegetation fuel types, and other contributory factors in relation to the built environment. Data provided by the Metro-RLIS and DOGAMI included information on the location of slopes and vegetation fuel types that that contribute to the risk of wildland fires. These were used to estimate areas of the Portland study area at risk of wildland fires.

The HAZUS-MH supported risk assessment methodology was applied to the wildland fire hazard analysis. Historical and simulation data for the wildland fire hazard are insufficient to estimate the frequency and severity of the hazard in a reliable manner; therefore, annualized losses cannot be computed. Instead, separate at-risk exposure values were assessed by occupancy class and for critical facilities, using the inventory data in HAZUS-MH.

Table 5-19 shows the population estimated to be at risk in the wildland fire hazard areas.

Table 5-19. Estimated Population at Risk from Wildland Fires

Category Total at Risk At-Risk Ratio

Number of Households 27,100 11.8 General Population 64,400 11.9

Population from Households with Income Less than $20K 8,700 7.2

Elderly People (65 years old or more)

7,500 11.9

Notes: For the low-income category, households are assumed to include 2.37 persons. The model does not address potential overlap in the socially vulnerable (low-income and elderly) categories; however, this impact is expected to be minor. Population numbers rounded to the nearest hundred.

Figure 5-23 shows the extent of the wildland fire hazard areas in relation to the population density to illustrate areas of the city where populations would be most impacted. Figures 5-24 and 5-25 illustrate the impacts to the socially vulnerable and show the population densities for elderly and low-income populations, respectively, in relation to the wildland fire hazard areas.

The population exposed to this hazard would be 64,400 (rounded to the nearest hundred persons). The socially vulnerable population exposed includes an estimated 8,700 low-income persons. It also includes 7,500 elderly persons (over the age of 65 years old).


Figure 5-23. Population Density Exposed to Wildland Fire

Figure 5-24. Elderly Population Density Exposed to Wildland Fire

WildfireThreat

N

0 2 4

miles


10,000 and Over5,000 to 9,9991,000 to 4,999


WildfireThreat

N

0 2 4

miles


2,000 and Over1,000 to 1,999

500 to 999100 to 499

Less than 100


Figure 5-25. Low-Income Population Density Exposed to Wildland Fire

WildfireThreat

N

0 2 4

miles


2,000 and Over1,000 to 1,999

500 to 999100 to 499

Less than 100

The total exposure value and at-risk ratio for structures considered to be exposed to wildland fire hazard areas are summarized in Table 5-20.

Table 5-20. Estimated Exposure Values for Structures at Risk from Wildland Fires

Category Total at Risk At-Risk Ratio

Total At-Risk Structures 25,048 14.4%

Residential Structures Exposed 24,791 14.5% Residential Structure Exposure $4,616.3M 14.7% Residential Content Exposure $2,308.1M 14.7%

Total Residential Exposure $6,924.4M 14.7%

Single Family Dwellings Exposed 23,938 15.0% Single Family Dwellings Structure

Exposure $3,873.2M 16.6%

Single Family Dwellings Content Exposure $1,936.6M 16.6%

Total Single Family Dwelling Exposure $5,809.8M 16.6%

Commercial Structures Exposed 257 9.0% Commercial Structure Exposure $414.0M 7.2% Commercial Content Exposure $495.4M 8.1%

Total Commercial Exposure $909.4M 7.6%

Total Exposure $7,833.3M 13.3% Notes: Single-family dwellings are a subset of the total residential occupancy class. M indicates million. Dollars rounded to the nearest hundred thousand.

Table 5-21 presents the impacts to critical facilities, transportation lifelines, and utility lifelines associated with the wildland fire hazard. The at-risk ratio is also shown.


Notes: Values for transportation and pipeline segments are reported in miles, as appropriate. K-12 indicates kindergarten through high school.

As shown in the table, the loss estimates for infrastructure from the wildland fire hazard are estimated to range from no or low risk to high risk for critical facilities, transportation lifelines, and utility lifelines.

Figures 5-26, 5-27, and 5-28 illustrate the distribution of critical facilities, transportation lifeline systems, and utility lifeline systems, respectively, in relation to the wildland fire hazard area.

Table 5-21. Infrastructure at Risk from Wildland Fire

Facility Class Estimated Number of Structures at Risk At-Risk Ratio

Critical Facilities Schools (K-12) 10 6.0% Hospitals 2 20.0% Fire Stations 4 12.1% Police Stations 0 0.0% Haz Mat Sites 6 2.3%

Transportation Lifeline Systems Bridges (railway/highway) 30 4.6% Key Roads (in miles) 5 2.4% Railway Tracks (in miles) 2 1.3% Light Rail (in miles) 2.6 17.3% Utility Lifeline Systems Potable Water Treatment Plants 2 18.2% Wastewater Treatment Plants 0 0.0% Electric Power Substations 138 13.4% Potable Water Pipelines (in miles) 20.8 16.8% Sewers (in miles) 14.0 4.6% Natural Gas Pipelines (in miles) 4.7 5.7% Oil Pipelines (in miles) 2.2 24.4%


Figure 5-26. Critical Facilities in Relation to Wildland Fire Hazard Areas

Figure 5-27. Transportation Lifeline Systems in Relation to Wildland Fire Hazard Areas








WildfireThreat

N



HospitalSchool

Police Station

0 2 4

miles

WildfireThreat

N

0 2 4

miles

Key



Figure 5-28. Utility Lifeline Systems in Relation to Wildland Fire Hazard Areas

WildfireThreat

N

0 2 4

miles

Pipe Type

OilGasWaterSewer


The Mean Return Period (MRP) considers the

severity of a hazard event that can occur within a given time period. For

example, the 100-year MRP event for earthquake

addresses the severity of ground shaking that has a 1

percent probability of occurring in any given year and is generally anticipated to occur at least once within

a 100-year period. The 500-year MRP event is

more severe than the 100-year event, but has a lower probability of occurring in

any given year (0.2 percent chance of occurring in any

one year and likely to occur once in a 500-year period).

The 100-year MRP earthquake in Portland

would be roughly equivalent to the ground shaking that would be associated with a 5.8 Magnitude earthquake

occurring in the Portland Hill area or a 7.0 Magnitude

earthquake occurring in the subduction zone (ocean).

Portland Hazard Relative Ranking Analysis

Table 5-22 summarizes the loss and exposure estimates for the Portland study area. The annualized loss column shows the average annualized loss estimated for the earthquake and flood hazard. Loss estimates could not be calculated for the landslide and wildland hazards based on current data limitations. The residential and commercial assets at risk column shows the value of building stock estimated to be at risk for each hazard based on available knowledge of the hazard and HAZUS-MH inventory data. The annualized loss estimate per $1,000 of assets at risk compares the annualized loss estimate to the assets at risk. In this case, the ratio is lower for earthquake than it is for flood. Although the earthquake hazard is estimated to have a greater loss estimate than flood ($29.7 million versus $15.4 million), its relative impact is lower because the area at risk is larger (in this case, the entire city is at risk for earthquake, whereas only flood zone areas are at risk for the flood hazard). This type of evaluation assists in comparing impacts across hazards and serves as one input to the city’s mitigation planning efforts.

Table 5-22. Summary of Loss Estimates for Portland

Hazard Annualized Loss Estimate

Residential and Commercial Assets at Risk Estimate(s)

Annualized Loss Estimate per $1,000 of

Assets at Risk

Earthquake $29.7M $59B 0.5

Flood $15.4M $5.9B 2.6 Landslide NE $8.8B NA

Wildland Fire NE $7.8B NA Notes: NE indicates not evaluated. NA indicates not available. M indicates millions and B indicates billions. Dollars rounded to the nearest hundred thousand (column 2) or million (column 3). For the flood hazard event, the 500-year at risk residential and commercial building stock is shown in column three. For earthquake, all of the residential and commercial building stock is exposed and used as the at-risk estimate.

DMA 2000 requires risk to be assessed qualitatively (such as high, medium, or low) and quantitatively, where feasible. For infrastructure (critical facilities, transportation lifelines, and utility lifelines), loss or exposure estimates are presented in this pilot study as a percent of total facilities at risk or damaged. These loss and exposure percentages are then used to express relative risk qualitatively, using the scale shown in Table 5-23.

Table 5-23. Summary of Risk Categories for Infrastructure







The relative ranking of hazards identified through this pilot project provides a

starting point for the mitigation planning

committee, which will evaluate additional hazards

and mitigation goals and options as it prepares the

city’s all hazards mitigation plan.

Table 5-24 summarizes the relative risk categories for infrastructure for each of the hazards analyzed for the Portland study area.

Table 5-24. Summary of the Relative Risk of Loss and Exposure Estimates for Infrastructure

Hazard Critical Facilities Transportation Lifelines Utility Lifelines Earthquake –

100-year MRP Event

Limited Risk (2.7% to 4.3%)

No Risk to Limited Risk (0.0% to 1.4%)

Limited Risk to Moderate Risk (3.8% to 8.6%)

Earthquake – 500-year MRP

Event



(1.3% to 18.5%)

Limited Risk to Severe Risk (3.8% to 57.4%)


Event

No Risk to Moderate Risk (0.0% to 7.2%)

Low Risk to Moderate Risk

(0.9% to 19.2%)



Event

No Risk to High Risk

(0.0% to 23.2%)

Moderate Risk to High Risk

(5.6% to 30.0%)


Landslide No Risk to High Risk (0.0% to 30.0%)


No Risk to Severe Risk (0.0% to 45.5%)

Wildland Fire No Risk to



(1.3% to 17.3%)

No Risk to High Risk (0.0% to 24.4%)

Notes: For categories where more than one loss ratio data is included, the relative ranking reflects the highest loss ratio within that category. Green indicates no to limited risk. Yellow indicates up to a moderate risk. Red indicates high risk to severe risk.

Summary of Results and Conclusions

As discussed in the loss estimate section and summarized on Table ES-1, HAZUS-MH was used to support loss estimates for the flood and earthquake hazard and exposure estimates for the landslide and wildland fire hazards. For the earthquake and flood hazards, the annualized loss estimate was then compared to the total assets at risk for each of these hazards. Based on the HAZUS-MH analysis and the input of the project team, the relative ranking of the four selected priority hazards for the City of Portland is estimated as follows (from highest to lowest concern):

1. Flood 2. Earthquake 3. Landslide 4. Wildland fire

Flood has a lower total loss estimate than earthquake ($15.4 million versus $29.7 million) but a greater proportionate impact on the assets at risk (2.6 for flood versus 0.5 for earthquake). The landslide and wildland fire hazards can not be compared directly to the flood and earthquake hazards because an annualized loss estimate was not feasible for these hazards. However, the exposures at risk for the landslide and wildland fire hazards are lower than the exposure at risk for the earthquake hazard and the likelihood that all of the inventory at risk would be lost should a landslide or wildfire occur is considered to be low. Therefore, these hazards are ranked lower than flood and earthquake for this analysis. Landslide has a greater exposure at risk


For additional explanation of the

meaning of the 100-year and 500-year MRP earthquake events, see

page xii.

For additional explanation of the meaning of the 100-year and 500-year MRP

flood events, see page xii or the Appendix 1 definitions for the 100-year flood and

500-year flood.

value than the wildland fire ($8.8 billion versus $7.8 billion); therefore, it is ranked higher than the wildland fire hazard above.

Other findings include:

? Growth trends indicate that the population in areas surrounding the study region is experiencing growth greater than that of the City of Portland. For example, the population of Multnomah County constituted 51 percent of the Portland/Vancouver area’s total population in 1970 and only 35 percent of the total population in 2000. The City of Portland comprises a large part of Multnomah County’s population. Studying growth trends can assist in state, regional and local emergency planning and mitigation decisions.

? Areas along the Willamette River include flood zones, landslide potential, liquefaction potential, soft soil areas, and significant development. The multiple hazard areas along the river, combined with the level of development, appear to indicate that this area may face greater risk of losses than other areas of the study region.

? Inventory in the study region is significant with, $59 billion in assets estimated, including: buildings, critical facilities, and infrastructure.

Earthquake

? For the 100-year MRP earthquake event, up to 1 percent of the households in the area (2,000 households) could require shelter. This increases to 4.6 percent (8,000 households) for the 500-year MRP event.

? For the 100-year MRP earthquake event, minor injuries are expected to impact up to 2,500 persons and major injuries and fatalities are expected to be as high as 200. For the 500-year MRP event, this increases 240 percent (to 8,500 persons) for minor injuries and 350 percent (to 900 persons) for major injuries and fatalities, respectively.

? The total economic loss ratio for residential and commercial occupancy classes for the 100- and 500-year MRP events ranged from 2 percent to 7.4 percent, respectively. The economic loss ratio represents the percent of the total building and content dollar value that would be required to repair or replace damaged structures and building content.

Flood

? For the 100-year MRP flood event, 4.9 percent (11,200 households) are exposed. Approximately 6.7 percent (15,300 households) are exposed to the 500-year MRP flood event.

? For the 100-year MRP flood event, 29,900 persons are exposed to this hazard (that is, live within the area likely to be impacted). This increases to 38,400 persons for the 500-year MRP event. For this


hazard, socially vulnerable populations represent 17.7 percent and 22.6 percent of the total population exposed for the 100- and 500- year MRP flood events, respectively. Persons from low-income households represent 22.2 percent of the overall population. Therefore, it appears that socially vulnerable populations are not disproportionately exposed to this hazard.

? Commercial building class losses account for about 37 and 43 percent of the total estimated loss for both the 100- and 500-year flood events, respectively. However, commercial buildings and content represent only about 20 percent of the total building and content value in Portland. This appears to indicate that commercial exposure may warrant further examination in relation to the flood hazard, as it appears to be disproportionately exposed to the flood hazard.

Landslide and Wildland Fire

? The populations at risk from landslides and wildland fires are 66,400 and 64,400, respectively. This indicates that exposure is somewhat greater for the landslide hazard.

? For the landslide and wildland fire hazards, total residential and commercial occupancy class value exposed to each hazard was $8.8 billion and $7.8 billion, respectively. This indicates that exposure is somewhat greater for the landslide hazard in the Portland area.

For this risk assessment, the loss estimates and exposure calculations rely on the best available data and methodologies. Uncertainties are inherent in any loss estimation methodology and arise in part from incomplete scientific knowledge concerning natural hazards and their effects on the built environment. Uncertainties also result from (1) approximations and simplifications that are necessary to conduct such a study, (2) incomplete or outdated data on inventory, demographic, or economic parameters, (3) the unique nature and severity of each hazard when it occurs, and (4) the amount of advance notice that the residents have to prepare for the event. These factors result in a range of uncertainty in loss estimates, possibly by a factor of two or more. As a result, potential exposure and loss estimates are approximate. These results do not predict precise results and should be used to understand relative risk. However, the results of this risk assessment study are useful in at least three ways:

? These efforts and results improve our understanding of the risk associated with the natural hazards in the City of Portland through better understanding of the complexities and dynamics of risk, how levels of risk can be measured and compared, and the myriad factors that influence risk. An understanding of these relationships is critical in balanced and informed decisions regarding risk management.

? These results provide a baseline for policy development and comparison of mitigation alternatives. The data used for this analysis present a current picture of risk in the City. Updating this risk “snapshot” with

At risk for the landslide and wildland fire hazards

indicates the number of persons or building value

lying within the geographic areas identified as defining

the hazard area.


future data will enable comparisons of the changes in risk with time. This sort of analysis is required as part of the DMA 2000 risk assessment effort. Therefore, baseline data can support the objective analysis of policy and program options for risk. Figure 5-29 provides a snapshot of projected future growth in the Portland area. Development is also discussed in Section 4.0, Inventory of Assets.

The growth expected in the Portland area underscores that the currently estimated losses would increase in the future (as population and inventory increase) if no mitigation measures are planned and implemented.

Figure 5-29. Projected Population Growth for Portland

? This snapshot effort begins to allow the community to compare the relative risk posed by the natural and other hazards addressed. The ability to quantify the risk posed by all of these hazards relative to one another helps in developing a balanced, multi-hazard approach to risk management at each level of government. The ranking approach provides a systematic framework to compare and prioritize the very disparate natural hazards that are present in the City of Portland. This final step in the risk assessment provides the necessary information for the Mitigation Planning Committee to craft a mitigation strategy to focus resources on only those hazards that pose the most significant threats to the City of Portland.

500,000

520,000

540,000

560,000

580,000

600,000

620,000

640,000

660,000

1 2 3 4 5 6 7 8 9

Year

Pop

ulat

ion

2000 2005 20100 2015 2020 2025 2030 2035 2040


REFERENCES

Burns, Dr. Scott F., Burns, William J., James, David H., Hinkle, Jason C. 1998. “Landslides in the Portland, Oregon Metropolitan Area Resulting from the Storm of February 1996: Inventory Map, Databases, and Evaluation.” Department of Geology. Portland State University.

Cascadia Region Earthquake Workgroup (CREW). 2003. “Earthquakes in the Cascadia Region.” Accessed at http://www.crew.org/region/cascadia.html.

Clackamas County. 2002. Natural Hazards Mitigation Plan. September.

City of Portland. 2002. Data Results Provided by City of Portland Geographic Information Systems (GIS) and Other Personnel. September.

Disaster Mitigation Act of 2000. U.S. Census Bureau. 2000. Public Law 106-390, 106th Congress: Act of 2000. Definitions of Census Terms. Accessed on October 21, 2003, at http://www.census.gov/geo/www.tractez.html.

Federal Emergency Management Agency (FEMA). 2001. “State and Local Mitigation Planning How-to Guide: Understanding Your Risks, Identifying Hazards and Estimating Losses.” FEMA Document No. 386-2. August.

FEMA. 2002. Hazard Mitigation Planning and Hazard Mitigation Grant Program; Interim Final Rule. CFR Parts 201 and 206. February.

FEMA. 2003a. FEMA On-line Library, Major Disaster Declarations. Accessed on August 12, 2003, at http://www.fema.gov/library/diz72-98.shtm.

FEMA. 2003b. Hazards U.S.-Multi-Hazards. Pre-Release Version Build 28a. October.

FEMA. 2004. “How-To Guide for Using HAZUS-MH for Risk Assessment.” FEMA Document No. 433. January.

Loy, William G. (Ed.). 2001. Atlas of Oregon, Second Edition. University of Oregon Press. Portland, Oregon.

Metro. 1999. “Regional Hazard Mitigation Policy and Planning Guide: Reducing Disaster Loss.” June.

Metro Data Resource Center / Regional Land Information System (RLIS). 2002. Metro Regional Data Book: Portland-Vancouver Metropolitan Area. Accessed on September 15, 2003, at http://www.metro-region.org/library_docs/maps_data/metroregionaldatabook 2002.pdf.

Multnomah County. 2002. Multnomah County Emergency Operations Plan. Accessed on September 15, 2003, at http://www.co.multnomah.or.us/dbcs/emergency_mgmt/ eop2002.pdf.


Oregon Department of Geology and Mineral Industry (DOGAMI). 2002a. Earthquake Hazard Maps and Seismic Risk Assessment for Klamath County set to release. Accessed on April 29, 2003, at http://www.oregongeolgy.com/ news&events/KFalls4.29.02.htm.

DOGAMI. 2002b. Data Results for Hazard Information, and Inventory and Critical Facility Data Provided by DOGAMI Personnel. December.

Oregon Department of Land Conservation and Development (LCD). 2003. Natural Hazards Program: Landslides General Information. Accessed at http://www.lcd.state.or.us/landslides/geninfo.html.

Oregon Office of Emergency Management. 2000. “Emergency Management Plan: Natural Hazards Mitigation Plan.” March.

Oregon Natural Hazards Workgroup. 2003. “Draft Oregon Natural Hazard Risk Assessment.” July.

Oregon State Police. 2003. Oregon’s Top Weather Events of the 20th Century. Accessed at http://www.osp.state.or.us/oem/library.

PBS&J (formerly, Durham Technologies, Inc.). 2003. Data Analysis for City of Portland Pilot Project; prepared under subcontract to Tetra Tech EM Inc., for the Federal Emergency Management Agency. October.

Portland Development Commission. 2003a. Demographics: Portland Area Quick Facts. Accessed on September 8, 2003, at http://www.pdc.us/bus_serv/facts-quick.asp.

Portland Development Commission. 2003b. “Portland Facts.” Spring/Summer 2002. Accessed on September 8, 2003, at http://www.pdc.us/pdf/bus_serv/pubs/ec_fact_book_ 2002.pdf.

U.S. Forest Service (USFS). 2004. Information on Wildfires. Accessed on January 14, 2004, at http://www.fs.fed.us .

Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon Appendix 1-1

APPENDIX 1

GLOSSARY

This resource defines terms that are used in, or support, the risk assessment document. These definitions were based on terms defined in documents included in the reference section, with modifications as appropriate to address Portland-specific definitions and requirements.

100-year flood – A flood that has a 1 percent chance of being equaled or exceeded in any one year. This flood event is also referred to as the base flood. The term "100-year flood" can be misleading. It is not the flood that will occur once every 100 years. Rather, it is the flood elevation that has a 1 percent chance of being equaled or exceeded each year. Thus, the 100-year flood could occur more than once in a relatively short period of time. The 100-year flood, which is the standard used by most Federal and state agencies, is used by the National Flood Insurance Program (NFIP) as the standard for floodplain management and to determine the need for flood insurance.

500-year flood – A flood that has a 0.2 percent chance of being equaled or exceeded in any one year.

Aggregate Data – Data gathered together across an area or region (for example, census tract or census block data).

Annualized Loss – The estimated long-term value of losses from potential future hazard occurrences of a particular type in any given single year in a specified geographic area. In other words, the average annual loss that is likely to be incurred in each year based on frequency of occurrence and loss estimates. Note that the loss in any given year can be substantially higher or lower than the estimated annualized loss.

Annualized Loss Ratio – Represents the annualized loss estimate as a fraction of the replacement value of the local building inventory. This ratio is calculated using the following formula: Annualized Loss Ratio = Annualized Losses / Exposure at Risk. The annualized loss ratio gauges the relationship between average annualized loss and at-risk building value. This ratio can be used as a measure of relative risk between hazards as well as across different geographic units.

Asset – Any manmade or natural feature that has value, including, but not limited to people, buildings, infrastructure (such as bridges, roads, and sewer and water systems), and lifelines (such as electricity and communication resources; or environmental, cultural, or recreational features like parks, dunes, wetlands, or landmarks).

At Risk – Exposure values that include the entire building inventory or population value in a census block or tract that lie within, or bordering the

Appendix 1-2 Risk Assessment Pilot Project Results for DMA 2000 Plan – City of Portland, Oregon

inundation areas or any area potentially exposed to a hazard based on location.

Base Flood – Flood that has a 1 percent probability of being equaled or exceeded in any given year. It is also known as the 100-year flood.

Base Flood Elevation (BFE) – Elevation of the base flood in relation to a specified datum, such as the National Geodetic Vertical Datum of 1929. The BFE is used as the standard for the National Flood Insurance Program.

Building – A structure that is walled and roofed, principally above ground and permanently fixed to a site. The term includes a manufactured home on a permanent foundation on which the wheels and axles carry no weight.

Census Block– A subdivision of a census tract (or, prior to 2000, a block numbering area), a block is the smallest geographic unit for which the U.S. Census Bureau tabulates 100-percent data. Many blocks correspond to individual city blocks bounded by streets, but blocks – especially in rural areas – may include many square miles and may have some boundaries that are not streets.

Census Tract – A small, relatively permanent statistical subdivision of a county delineated by a local committee of census data users for the purpose of presenting data. Census tract boundaries normally follow visible features, but may follow governmental unit boundaries and other non-visible features in some instances; they always nest within counties. Designed to be relatively homogeneous units with respect to population characteristics, economic status , and living conditions at the time of establishment, census tracts average about 4,000 inhabitants. They may be split by any sub-county geographic entity.

Critical Facility – Facilities that are critical to the health and welfare of the population and that are especially important following a hazard. Critical facilities include essential facilities, transportation systems, lifeline utility systems, high-potential loss facilities, and hazardous materials sites. As defined for the Portland risk assessment, this category includes: schools, hospitals, fire stations, police stations, and hazardous materials sites.

Content Value – The value of a building’s content include all the items in a building, excluding the structure itself. The values are estimated to be 50 percent of the residential structural value and 100 percent of the commercial building replacement value.

Digital Elevation Model (DEM) – U.S. Geological Survey (USGS) Digital Elevation Model (DEM) data files are digital representations of cartographic information in a raster form. DEMs include a sampled array of elevations for a number of ground positions at regularly spaced intervals. These digital cartographic/geographic data files are produced by USGS as part of the National Mapping Program.


Displacement Time – After a hazard occurs, the average time (in days) that a building’s occupants must operate from a temporary location while repairs are made to the original building due to damages resulting from the hazard.

Disaster Mitigation Act of 2000 (DMA 2000) – Law that requires and rewards local and state pre-disaster planning, promotes sustainability as a strategy for disaster resistance, and is intended to integrate state and local planning with the aim of strengthening statewide mitigation planning.

Drought – A period of time without substantial rainfall that persists from one year to the next. Droughts can affect large areas and can impact areas that range from a few counties to several states. Along with decreasing water supplies for human consumption and use, droughts can kill crops, livestock, grazing land, edible plants, and even, in severe cases, trees.

Duration – The length of time a hazard occurs.

Earthquake – A sudden motion or trembling that is caused by a release of strain accumulated within or along the edge of earth’s tectonic plates.

Economic Loss Ratio – The estimated value of the loss divided by the total inventory value. This represents the percent of the total occupancy class inventory value that likely would be incurred to repair or restore the facility to its original, pre-hazard state. A loss ratio of less than 1 percent is considered to be a very low risk; 1 to 5 percent to be low; 5 to 20 percent to be medium; 20 to 40 percent to be high; and greater than 40 percent to be very high.

Erosion – Wearing away of the land surface by detachment and movement of soil and rock fragments, during a flood or storm or over a period of years, through the action of wind, water, or other geologic processes.

Erosion Hazard Area – Area anticipated to be lost to shoreline retreat over a given period of time. The projected inland extent of the area is measured by multiplying the average annual long-term recession rate by the number of years desired.

Essential Facility – A facility that is important to ensure a full recovery of a community or state following the occurrence of a hazard. These facilities can include government facilities, major employers, banks, schools, and certain commercial establishments (such as grocery stores, hardware stores, and gas stations).

Exposure – The number and dollar value of assets that are considered to be at risk during the occurrence of a specific hazard.

Extent – The size of an area affected by a hazard or the occurrence of a hazard.

Federal Emergency Management Agency (FEMA) – Independent agency (now part of the Department of Homeland Security) created in 1978 to


provide a single point of accountability for all Federal activities related to disaster mitigation and emergency preparedness, response, and recovery.

Flash Flood – A flood occurring with little or no warning where water levels rise at an extremely fast rate.

Flood – A general and temporary condition of partial or complete inundation of normally dry land areas resulting from (1) the overflow of inland or tidal waters, (2) the unusual and rapid accumulation or runoff of surface waters from any source, or (3) mudflows or the sudden collapse of shoreline land.

Flood Depth – Height of the flood water surface above the ground surface.

Flood Elevation – Height of the water surface above an established datum (for example, the National Geodetic Vertical Datum of 1929, North American Vertical Datum of 1988, or Mean Sea Level).

Flood Hazard Area – Area shown on a map to be inundated by a flood of a given magnitude.

Flood Information Tool (FIT) – HAZUS-MH tool designed to process and convert locally available flood information to data that can be used by the HAZUS-MH Flood Module. The FIT is a system of instructions, tutorials and GIS analysis scripts. When provided with user-supplied inputs (for example, ground elevations, flood elevations, and floodplain boundary information), the FIT calculates flood depth and elevation for riverine and coastal flood hazards.

Flood Insurance Rate Map (FIRM) – Map of a community, prepared by FEMA, which shows both the special flood hazard areas and the risk premium zones applicable to the community.

Flood Insurance Study (FIS) – A study that provides an examination, evaluation, and determination of flood hazards and, if appropriate, corresponding water surface elevations in a community or communities.

Floodplain – Any land area, including a watercourse, susceptible to partial or complete inundation by water from any source.

Flood Polygon – A Geographic Information System (GIS) vector file outlining the area exposed to the flood hazard. HAZUS-MH generates this polygon at the end of the flood computations in order to analyze the inventory at risk.

Frequency – A measure of how often events of a particular magnitude are expected to occur. Frequency describes how often a hazard of a specific magnitude, duration, and/or extent typically occurs, on average. Statistically, a hazard with a 100-year recurrence interval is expected to occur once every 100 years on average, and would have a 1 percent chance – its probability – of happening in any given year. The reliability of this information varies depending on the kind of hazard being considered.


Geographic Information Systems (GIS) – A computer software application that relates data regarding physical and other features on the earth to a database to be used for mapping and analysis.

GIS Shape Files – A type of GIS vector file developed by ESRI for its ArcView software. This type of file contains a table and a graphic. The records in the table are linked to corresponding objects in the graphic.

Hazard – A source of potential danger or an adverse condition that can cause harm to people or cause property damage. For this risk assessment, priority hazards were identified and selected for the pilot project effort. A natural hazard is a hazard that occurs naturally (such as flood, wind, and earthquake). A human-caused hazard is one that is caused by humans (for example, a terrorist act or a hazardous material spill). Hazards are of concern if they have the potential to harm people or property.

Hazard Identification – The process of identifying hazards that threaten an area.

Hazards of Interest – Hazards considered most likely to impact a community based on frequency, severity, or other factors such as public perception. These are identified using available data and local knowledge.

Hazardous Materials Sites – Facilities housing industrial and hazardous materials, such as corrosives, explosives, flammable materials, radioactive materials, and toxins.

Hazard Mitigation – Sustained actions taken to reduce or eliminate the long-term risk and effects that can result from the occurrence of a specific hazard. For example, building a retaining wall can mitigate potential hazards.

Hazard Mitigation Plan – A collaborative document in which hazards affecting the community are identified, vulnerability to hazards are assessed, and consensus is reached on how to minimize or eliminate the effects of these hazards.

Hazard Profile – A description of the physical characteristics of a hazard, including a determination of various descriptors including magnitude, duration, frequency, probability, and extent. In most cases, a community can most easily use these descriptors when they are recorded and displayed as maps.

Hazard Risk Gauge – The graphic icon used during the initial planning process to convey the relative risk of a given hazard in the study area. The scale ranges from green, indicating relatively low or no risk, to red, indicating severe risk.

HAZUS (Hazards U.S.) – A GIS-based nationally standardized earthquake loss estimation tool developed by FEMA. HAZUS was replaced by HAZUS-MH (see below) in 2003.


HAZUS-MH (Hazards U.S. - Multi-Hazard) – A GIS-based nationally standardized earthquake, flood, and wind loss estimation tool developed by FEMA. The purpose of this pilot project is to demonstrate and implement the use of HAZUS-MH to support risk assessments.

HAZUS-MH Provided Data – The databases included in the HAZUS-MH software that allow users to run a preliminary analysis without collecting or using local data.

HAZUS-MH Risk Assessment Methodology – This analysis uses the HAZUS-MH modules (earthquake, wind (hurricane) and flood) to analyze potential damages and losses. For this pilot project risk assessment the earthquake and flood hazards were evaluated using this methodology.

HAZUS-MH Supported Risk Assessment Methodology – This analysis involves using inventory data in HAZUS-MH combined with knowledge such as (1) information about potentially exposed areas, (2) expected impacts, and (3) data regarding likelihood of occurrence for hazards.

High Potential Loss Facilities – Facilities that would have a high loss associated with them, such as nuclear power plants, dams, and military installations.

Infrastructure – The public services of a community that have a direct impact on the quality of life. Infrastructure includes communication technology such as phone lines or Internet access, vital services such as public water supplies and sewer treatment facilities, transportation system (such as airports, heliports, highways, bridges, tunnels, roadbeds, overpasses, railways, bridges, rail yards, depots; and waterways, canals, locks, seaports, ferries, harbors, dry docks, piers and regional dams).

Intensity – A measure of the effects of a hazard occurring at a particular place.

Interface – A fire hazard term used to describe areas where homes and other structures have been built on or adjacent to forest and range lands. It is an intermingling of built structures with natural cover at various degrees of growth and complexity.

Inventory – The assets identified in a study region. The inventory assessment addresses what can be lost when a disaster occurs, that is, what community resources are at risk. Assets include people, buildings, transportation and other valued community resources.

Level 1 Analysis – A HAZUS-MH analysis that yields a rough estimate or preliminary analysis based on the HAZUS-MH provided nationwide databases. A Level 1 analysis is a useful way to begin the risk assessment process and prioritize high-risk communities without collecting or using local data.


Level 2 Analysis – A HAZUS-MH analysis that requires the input of additional or refined inventory data and hazard maps that will produce more accurate risk and loss estimates. Assistance from local emergency management personnel, city planners, GIS professionals, and others may be necessary for this level of analysis.

Level 3 Analysis – A HAZUS-MH analysis that yields the most accurate estimate of loss and typically requires the involvement of technical experts such as structural and geotechnical engineers who can modify loss parameters based on the specific conditions of a community. This level analysis will allow users to supply their own techniques to study special conditions such as dam breaks and tsunamis. Engineering and other expertise is needed at this level.

Lifelines – Critical facilities that include utility systems (potable water, wastewater, oil, natural gas, electric power facilities and communication systems) and transportation systems (airways, bridges, roads, tunnels and waterways.

Loss Estimation – The process of assigning hazard-related damage and loss estimates to inventory, infrastructure, lifelines, and population data. HAZUS-MH can estimate the economic and social loss for specific hazard occurrences. Loss estimation is essential to decision making at all levels of government and provides a basis for developing mitigation plans and policies. It also supports planning for emergency preparedness, response, and recovery.

Lowest Floor – Under the NFIP, the lowest floor of the lowest enclosed area (including basement) of a structure. For the HAZUS-MH flood model, this information can be used to assist in assessing the damage to buildings.

Magnitude – A measure of the strength of a hazard occurrence. The magnitude (also referred to as severity) of a given hazard occurrence is usually determined using technical measures specific to the hazard. For example, ranges of wind speeds are used to categorize tornados.

Magnitude (M) – A measure of earthquake size; the amount of energy released by an earthquake. Energy release increases 30 times for each integer on the scale. Moment Magnitude is a direct measure of energy and is a more accurate measure of the true strength or intensity of an earthquake.

Major Disaster Declarations – Post-disaster status requested by a state’s governor when local and state resources are not sufficient to meet disaster needs. It is based on the damage assessment, and an agreement to commit state funds and resources to the long-term recovery. The event must be clearly more than the state or local government can handle alone.

Mean Return Period (MRP) – The average period of time, in years, between occurrences of a particular hazard (equal to the inverse of the annual frequency of exceedance).


Mitigation Plan – A plan that documents the process used for a systematic evaluation of the nature and extent of vulnerability to the effects of natural hazards typically present in a state or community. The plan includes a description of actions to minimize future vulnerability to hazards. This plan should be developed with local experts and significant community involvement.

National Flood Insurance Program (NFIP) – Federal program created by Congress in 1968 that makes flood insurance available in communities that enact minimum floodplain management regulations in 44 Code of Federal Regulations (CFR) §60.3.

National Weather Service – Organization that prepares and issues flood, severe weather, and coastal storm warnings and can provide technical assistance to Federal and state entities in preparing weather and flood warning plans.

Occupancy Classes – Categories of buildings used by HAZUS-MH (for example, commercial, residential, industrial, government, and “other”).

Parametric Model – A model relating to or including the evaluation of parameters. HAZUS-MH uses parametric models that address different parameters for hazards such as earthquake, flood and wind (hurricane). For example, parameters considered for the earthquake hazard include soil type, peak ground acceleration, building construction type, and others.

Peak Ground Acceleration (PGA) – PGA is the movement experienced by a particle on the ground during a seismic event.

Pilot Project – In this case, a project sponsored by FEMA to support the implementation of studies conducted in coordination with communities. The project focuses on demonstrating the value and benefits of using HAZUS-MH for the risk assessment portion of all-hazard mitigation plans required by the DMA 2000. The projects demonstrate the value of using HAZUS-MH to evaluate and analyze natural hazards that a number of state and local communities might address in their planning process. The pilot projects demonstrate that HAZUS-MH can provide defensible cost and loss estimates using the engineering and scientific risk calculations included in the software.

Planimetric – Maps that indicate only built features like buildings.

Planning – The act or process of making or carrying out plans; the establishment of goals, policies and procedures for a social or economic unit.

Presidential Disaster Declaration – A post-disaster status that puts into motion long-term federal recovery programs, some of which are matched by state programs, and designed to help disaster victims, businesses, and public entities in the areas of human services, public assistance (infrastructure support), and hazard mitigation. If declared, funding comes from the


President’s Disaster Relief Fund and disaster aid programs of other participating federal agencies.

Probability – A statistical measure of the likelihood that a hazard event will occur.

Q3 Flood Zone Data – FEMA flood data that delineate the 100- and 500-year flood zone boundaries. The Q3 Flood Data are digital representations of certain features of FEMA’s Flood Insurance Rate Map (FIRM) product, intended for use with desktop mapping and GIS technology.

Recurrence Interval – The average time between the occurrence of hazards of similar size in a given location. This interval is based on the probability that the given event will be equaled or exceeded in any given year.

Repetitive Loss Property – A property that is currently insured for which two or more NFIP losses (occurring more than ten days apart) of at least $1,000 each have been paid within any 10-year period since 1978.

Replacement Value – The cost of rebuilding or repairing a structure. This cost is usually expressed in terms of cost per square foot and reflects the present-day cost of labor and materials to construct a building of a particular size, type and quality.

Risk – The estimated impact that a hazard would have on people, services, facilities, and structures in a community; the likelihood of a hazard occurring and resulting in an adverse condition that causes injury or damage. Risk is often expressed in relative terms such as a high, moderate or low likelihood of sustaining damage above a particular threshold due to occurrence of a specific type of hazard. Risk also can be expressed in terms of potential monetary losses associated with the intensity of the hazard.

Risk Assessment – A methodology used to assess potential exposure and estimated losses associated with priority hazards. The risk assessment process includes four steps: (1) identifying hazards, (2) profiling hazards, (3) conducting an inventory of assets, and (4) estimating losses. This pilot project report documents this process for selected hazards addressed as part of the pilot project.

Risk Factors – Characteristics of a hazard that contribute to the severity of potential losses in the study area.

Riverine – Of or produced by a river (for example, a riverine flood is one that is caused by a river overflowing its banks).

Scale – A proportion used in determining a dimensional relationship; the ratio of the distance between two points on a map and the actual distance between the two points on the earth’s surface.

Scour – Removal of soil or fill material by the flow of floodwaters. This term is frequently used to describe storm-induced, localized, conical erosion


around pilings and other foundation supports where the obstruction of flow increases turbulence.

Stafford Act – The Robert T. Stafford Disaster Relief and Emergency Assistance Act, Public Law (PL) 100-107 was signed into law on November 23, 1988. This law amended the Disaster Relief Act of 1974, PL 93-288. The Stafford Act is the statutory authority for most Federal disaster response activities, especially as they pertain to FEMA and its programs.

State Hazard Mitigation Officer – The representative of state government who is the primary point of contact with FEMA, other state and Federal agencies, and local units of government in the planning and implementation of pre- and post-disaster mitigation activities.

Structure – Something constructed (for example, a residential or commercial building).

Study Area – The geographic unit for which data are collected and analyzed. A study area can be any combination of states, counties, cities, census tracts, or census blocks. The study area definition depends on the purpose of the loss study and in many cases will follow political boundaries or jurisdictions such as city limits.

Substantial Damage – Damage of any origin sustained by a structure in a SFHA, for which the cost of restoring the structure to its pre-hazard event condition would equal or exceed 50 percent of its pre-hazard event market value.

Topographic – Map that shows natural features and indicates the physical shape of the land using contour lines based on land elevation. These maps also can include manmade features (such as buildings and roads).

Transportation Systems – One of the lifeline system categories. This category includes airways (airports, heliports), highways, bridges, tunnels, roadbeds, overpasses transfer centers, railways (tracks, tunnels, bridges, rail yards, depots), and waterways (canals, locks, seaports, ferries, harbors, dry docks, piers).

Utility Systems – One of the lifeline system categories. This category includes potable water, wastewater, oil, natural gas, electric power facilities, and communication systems.

Vulnerability – Description of how exposed or susceptible an asset is to damage. This term depends on an asset’s construction, contents, and the economic value of its functions. Like indirect damages, the vulnerability of one element of the community is often related to the vulnerability of another. For example, many businesses depend on uninterrupted electrical power. If an electric substation is flooded, it will affect not only the substation itself, but a number of businesses as well. Often, indirect effects can be much more widespread and damaging than direct ones.


Vulnerability Assessment – Evaluation of the extent of injury and damage that may result from a hazard event of a given intensity in a given area. The vulnerability assessment should address impacts of hazard occurrences on the existing and future built environment.

Watershed – Area of land that drains down gradient (from areas of higher land to areas of lower land) to the lowest point; a common drainage basin. The water moves through a network of drainage pathways, both underground and on the surface. Generally, these pathways converge into streams and rivers, which become progressively larger as the water moves downstream, eventually reaching an estuary, lake, or ocean.

Windstorm – A storm characterized by high wind velocities.

Zone – A geographical area shown on a National FIRM that reflects the severity or type of flooding in the area.


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APPENDIX 2

DATA SUMMARY MATRIX

This document provides an overview of local data collection efforts to support a HAZUS-driven risk assessment (RA) pilot project study for the City of Portland, Oregon. This appendix and the risk assessment document it supports serve as input to Portland’s Hazard Mitigation Plan and are intended to support the City’s long-term hazard mitigation planning efforts.

The risk assessment analysis was conducted between November 2002 and March 2004. Agencies and stakeholders involved in the collection of data used for the risk assessment include FEMA Headquarters and Region X; State of Oregon Emergency Management and the Department of Geology and Mineral Industries (DOGAMI); City of Portland Office of Emergency Management; partnering agencies, including: City of Portland Bureau of Technology Services, Bureau of Environmental Services, and Bureau of Planning; Multnomah County Office of Emergency Management; Clackamas County Emergency Management; Metro Regional Services; and consultants to FEMA (Tetra Tech EM Inc. and PBS&J).

In this appendix, data have been categorized into three broad categories consistent with the development of the risk assessment analysis. The three data categories are addressed as follows:

Ø Base Data Requirements

o Political boundaries (City, tracts, and blocks)

o Rivers

Ø Inventory Data Requirements

o Aggregate information

§ Land use (square footage)

§ Dollar exposure at-risk

§ Building count

§ People at-risk

o Site-specific information

§ Essential facilities

§ Critical facilities

§ Transportation systems

§ Utility systems


Ø Hazard Data Requirements (specific hazards to be addressed)

o Riverine flooding

o Earthquake

o Landslide

o Wildland fire

This summary addresses only data need to support the pilot project risk assessment. Additional data that may be useful (or desired) for the general support of the mitigation plan are not addressed in this summary because they are outside the scope of this pilot project risk assessment effort.

Base Data Requirements

Base data relates to geo-political and environmental data. These geospatial layers are needed to define the extent and the resolution level of the Portland study area to support the comprehensive risk assessment. Table 1 includes a summary of base data layers and the sources of the data that are important for planning purposes.

Table 1. Base Data Layer and Source

Data Layer Source

City boundary Regional Land Information System (RLIS) Block boundaries RLIS

Census boundaries RLIS Rivers RLIS

Parcels data RLIS

Inventory Data Requirements

Inventory data comprise land use (square footage), building stock, and demographic data. These data are better presented as aggregated versus site-specific. Table 2 includes a summary of the aggregated inventory data layers and the sources of the data used for the risk assessment study.

Table 2. Aggregated Inventory Data Layer and Source

Data Layer Source

Block-based demographic data HAZUS-MH - U.S. Census Bureau Block-based square footage / land use HAZUS-MH - Dun and Bradstreet (D&B)

Block-based dollar exposure by occupancy class HAZUS-MH Block-based building count by occupancy class HAZUS-MH


Inventory data also comprise essential facilities, critical facilities, transportation systems, and utility systems. These data are better presented as site-specific information. Point features other than bridges include:

Ø Essential facilities comprise schools, nursing homes, and hospitals (3 groups).

Ø Critical facilities comprise police stations, fire stations, emergency operation centers (EOCs), and other government facilities (4 groups).

Ø Transportation facilities comprise maintenance facilities, fuel facilities, dispatch facilities, and main terminal stations (4 groups).

Ø Utility facilities comprise treatment plants, storage tanks, wells, compressor stations, refineries, substations, electric power plants and central offices (8 groups).

All facility data has been obtained from RLIS / Portland Metro. The list below specifies attributes required for site-specific data for HAZUS-MH and whether these inventory attributes are available from the primary data source.

(1) Name of facility (yes)

(2) Exact location (yes)

(3) Year built (yes)

(4) Replacement value (yes)

(5) Content value (no)

(6) Number of stories / floors (yes)

(7) Square footage (yes)

(8) First floor elevation (no)

(9) Number of occupants (no)

(10) Building type (yes)

Additional attribute information related to the size and/or capacity was also obtained for all utility facilities.

Line features include roads, railway and light rail tracks, and pipelines (potable water, sewer, storm water, oil, and gas). RLIS provided the location of all these line features. In addition, for pipelines, the following attributes are required for HAZUS-MH and were available: (1) the diameter of the pipe, (2) the year of construction, and (3) the replacement value.

HAZUS-MH provides a data for county and state bridges as compiled by the Federal Highway Administration (FHWA) (data from 2000). Therefore, no additional data gathering was sought in this category.


Hazard Data Requirements

Four hazards were considered in this pilot project risk assessment study: (1) riverine flooding, (2) earthquake, (3) landslide, and (4) wildland fire. Tables 3 and 4 include a summary of hazard data and the sources of the data for each of the four hazards.

Table 3. Riverine Flooding Hazard Data Layer and Source

Data Layer Source

Drainage basins HAZUS-MH 100-year flood boundary map FEMA 500-year flood boundary map FEMA

Base flood elevation FEMA Damage data from historical flood events RLIS (partial)

High-resolution elevation data USGS

Table 4. Earthquake, Landslide, and Wildland fire Hazard Data Layers and Sources

Data Layer Source

Probabilistic hazard data HAZUS-MH - U.S. Geological Survey (USGS)

Soil Metro / Oregon Department of Geology and Mineral Industries (DOGAMI)

Liquefaction susceptibility Metro / DOGAMI Landslide susceptibility Metro / DOGAMI

Water table depth Not available Wildland fire susceptibility Metro /DOGAMI


APPENDIX 3

HAZARD RELATIVE RANKING BACKGROUND

This appendix of the Portland risk assessment provides a background overview of the approach to hazard ranking evaluation and relative risk analysis used in this pilot project.

Figure 1 provides a framework for evaluating relative risk based on of the likelihood and expected impact of various hazards. Each quadrant in the figure represents a relative area of concern based on the probability and estimated impact (damage/loss) of hazard events, ranging from the highest concern (quadrant D) to the lowest concern (quadrant A).

Figure 1. Framework for Relative Risk Evaluation

Hazards that tend to occupy the lower right-hand quadrant of the chart, Quadrant D, have a high probability of occurrence (occur with the most frequency) and high impact (high potential damage estimate). Therefore, these hazards are likely to be of greatest concern to a community and likely will be a focus for mitigation planning efforts.

Areas of secondary concern are those hazards identified in Quadrants B and C. Hazards in Quadrant B have a low probability of occurrence but a high potential impact, while Quadrant C hazards have a high probability of occurrence but a low potential impact. Hazards categorized in Quadrant A

Damage, $

Rec

urr

ence

MR

P, Y

ears

ALow ProbabilityLow Impact, $

CHigh Probability

Low Impact, $

BLow ProbabilityHigh Impact, $

D High Probability

High Impact, $


are likely to be of lowest relative concern because they are predicted to have both a low probability and a low impact.

The figure above provides a systematic framework within which to compare and prioritize hazards. However, public perception and other community-specific factors will affect the final hazard prioritization scheme. Particularly, the perception of hazards that fall into Quadrants A, B, and C will depend on factors such as the level of risk tolerance or importance a specific hazard might have to the community. For example, a particularly memorable historic drought event may affect community perception of risk exposure or loss tolerance. Planners will need to take public perception into account and provide education or other means to present risk information in a manner that makes sense to the local community. Also, public perceptions should be considered as part of the mitigation planning process.

The ranking of hazards also is dependent on the return period or “frequency” of occurrence for a hazard. For example, a damage profile for a 100-year return period will differ from a profile for a 50-year return period. The community must evaluate its risk threshold and tolerance, and determine the appropriate return period of interest. Urban and regional planners considering short- and medium-term planning horizons may be interested in a 25-year return period, while insurance companies examining deductible calculations may consider the 100-year return period to be appropriate.

To allow relative risk evaluations, the use of annualized losses for risk assessments is recommended, whenever possible. In general, annualized losses are useful on three fronts:

1. The contribution of potential losses from all future disasters is accounted for with this approach.

2. When annualized, results for different hazards are readily comparable and therefore, easier to compare in a relative manner.

3. When evaluating mitigation alternatives, use of annualized losses is the most objective approach to help assess cost/benefit potential.

Annualized losses for hazards that are analyzed using parametric models can be computed using the following three-step process:

1. Compute or estimate losses for a number of scenario events with different return periods [for example, 10-year, 100-year, 200-year, 500-year].

2. Approximate the Probability versus Loss Curve through curve fitting across the different mean return periods.

3. Calculate the area under the fitted curve to obtain the annualized loss.

This approach is illustrated graphically in Figure 2.

Annualized Loss means the average annual loss

that is likely to be incurred in each year, based on the

expected losses associated with a variety

of mean return periods for a hazard. The loss in any

given year can be substantially higher or

lower than the estimated annualized loss.


Figure 2. Graphical Representation of the Annualized Loss Methodology

Notes: The x -axis of this figure proceeds from a probability of 0 to P100 (a probability of 0.01, the annual probability of a 100 year event). The area under the curve represents the total annualized losses associated with this hazard.

If hazards are presented in an annualized loss manner, the hazard with the highest annualized loss estimate is generally the hazard of greatest concern, with other hazards following by order of the magnitude of the annualized loss. This methodology was applied in ranking the hazards for this risk assessment.

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