using gis for hazard assessment

7/31/2019 Using GIS for Hazard Assessment

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1

The use of GIS for hazard assessment

Cees van Westen

International Institute

for Geo-Information Science and Earth Observation

(ITC), Enschede, The Netherlands.

E-mail: [email protected]

RISK = HAZARD * VULNERABILITY * AMOUNT

Hazard = PROBABILITY of event with a

certain magnitude

Vulnerability = Degree of damage. Function of:

magnitude of event, and

type of elements at risk

ILWIS 2.1 concepts

Hazard, vulnerability and risk?

Hazard= PROBABILITY of event with a certain magnitude

Vulnerability = Degree of damage. Function of: magnitude of event, and type of elements at risk

Amount = Quantification of the elements at risk e.g. Replacement costs of buildings, infrastructure etc. Loss of function or economic activities Number of people


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ILWIS 2.1 concepts


z Example:

10 years RP

US $ 50.000

z Hazard = probability within a given period

= 0.1 / year

z Risk = hazard * vulnerability * amount

= 0.1 * 1 *50.000 = 5.000 US $

V = 1

ILWIS 2.1 concepts


z Example:

10 years RP

US $ 50.000


= 0.1 * (

(0.5*200.000)+

(0.1*100.000)+

(1 * 50.000)) = 0.1 * 160.000 = 16.000 $

V = 1

V = 0.1

US $ 100.000US $ 200.000

V = 0.5


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ILWIS 2.1 concepts


z Example:

2 years RP

10 years RP

50 years RP

US $ 50.000

z Hazard = 0.5 * 0.01 * 50.000 +

0.1 * 0.1 * 50.000 +

0.02 * 1 * 50.000 =

= 250 + 500 + 1000

= 1750 US $

V = 0.01

V = 0.1

V = 1

100000

1

0

0.020.1

0.5

1000

Risk curve

ILWIS 2.1 concepts

In reality

z Example:

RP = ??

Price is ???


= ? * ? * ? = unknown

What is needed:

hazard assessment , elements at risk mapping,

vulnerability assessment, cost estimation.

V = ????

Depth = ????


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ILWIS 2.1 concepts

Risk is a spatial problem

z Hazard:

How much water

when and where?

z Elements at risk:

Which elementswhere, and how

many/much ?

z Vulnerability:

How much waterwhere which elements

at risk are?

ILWIS 2.1 concepts

Risk is a multidisciplinary spatial problem

z Hazard assessment:

done by earth scientists,hydrologists, volcanologists,

seismologists etc.z Elements at risk:

done by geographers, urbanplanners, civil engineers

z Cost estimation:

done by economists

z Vulnerability:

done by structural engineers,civil engineers

z Risk assessment:

Done by GIS experts

Vulnerabilitymap

Risk map

Hazard map

Cost information

Elements at risk

Aerial photographs

Satellite images

GPS

Statistical tables

Risk assessment needs GIS


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ILWIS 2.1 concepts

Procedure

The use of GIS will:

z Decrease the time for data

collection (mobile GIS)

z Increase the time for data

management (digitizing)

z Decrease the time for data

analysis very much (to 5%

of total time).

ILWIS 2.1 concepts

What are you going to do?

z First define the objective of the study.

z Danger exists that the data that will be collected will not be in

accordance with the scale of analysis, or the method of analysis.z This might lead to a waste of time and money if too detailed data is

collected, or an oversimplification if too general data is collected.

z The following things should be considered:

z The objective of the study

z The scale of the study

z The type of analysis that will be followed

z The types of input data that will be collected.


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ILWIS 2.1 concepts

Defining objective

z Hazard studies can be made for any different purposes. Some ofthese might be:

z For an environmental impact study for engineering works;

z For the disaster management of a town or city;

z For the modelling of sediment yield in a catchment ;

z For a watershed management project;

z For a community participation project in disastermanagement;

z For a the generation of awareness among decision makers;

z For scientific purposes.

z Each of these objectives will lead to specific requirements withrespect to the scale of work, the method of analysis and the typeand detail of input data to be collected.

ILWIS 2.1 concepts

Scales of analysis (1)

z National scale

Smaller than 1:1.000.000,covering an entire country,

mainly intended to generate

awareness among decision

makers and the general

public. Maps on this scale are

often intended to be included

in national atlases.


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ILWIS 2.1 concepts


Regional scale

Between 1:100.000 and1:1.000.000, covering a largecatchment area, or a politicalentity of the country.

The maps at this scale aremostly intended forreconnaissance phases forplanning projects for the

construction of infrastructuralworks, or large developmentprojects.

ILWIS 2.1 concepts


Medium scale

Between 1:25.000 and

1:100.000, covering amunicipality or smallercatchment area.

Intended for the detailedplanning phases of projectsfor the construction ofinfrastructural works,environmental impactassessment and municipal

planning.


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ILWIS 2.1 concepts


Large scale

Between 1:2.000 and

1:25.000, covering a town or

(part of) a city.

They are used for generation

of detailed risk maps.

ILWIS 2.1 concepts


Site investigation scale

Between 1:200 to 1:2.000,

covering the area where

engineering works will be

carried out, or covering a

single problem area. They are

used for the detailed design

of engineering works, such as

roads, bridges, tunnels, dams,

and for the construction of

mitigation works.


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ILWIS 2.1 concepts

Input data for hazard analysis

The type of input data for a GIS-based hazard study

depends on:

z The type of hazard studied (e.g. earthquake hazard

assessment requires very different input data than

flood hazard assessment)

z The analysis method that will be used (more complexmethods are more data demanding).

z The scale of the study (the larger the area the more

data collection is needed)z The availability of resources (money and manpower)

z The amount of available data.

ILWIS 2.1 concepts

Altitude information:

z Existing digital elevation models

z Topographic maps at right scale digitizing

z Photogrammetrical methods with airphotos

z Photogrammetrical methods with satellite images

z Lidar (Light detection and ranging) best

z Radar interferometry.

Basic data for hazard analysis (1)


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ILWIS 2.1 concepts

Historical information of hazardous events:

z Existing catalogs/ records (seismic catalog, dischargemeasurements, rainfall records)z What is the timespan?? / completeness

z Historical study of archieves (newspapers, log booksetc.)

z Using multi-temporal imagery (satellite images orairphotos)

z How often can you get them? Scale? During the event?

z Field mapping (e.g. landslides, flood marks)z Should not be too long ago.

z Interviewing population / participatory approach


ILWIS 2.1 concepts

Collecting data on factors that determine hazards:

z Geological maps (e.g. landslides, earthquakes)

z Geotechnical maps (e.g. landslides, earthquakes)

z Landuse maps (e.g. landslides, floods, forest f ires)

z May have to be multi-temporal

z Slope maps, aspect maps, slope length (e.g. landslides)

z Field data collection (e.g. boreholes, geophysicalstudies, river cross sections, landslide characteristics)

z Laboratory analysis (e.g. soil strength, rock

composition)



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ILWIS 2.1 concepts

Types of hazard assessment

The past is the key to the future:

z Historical analysis:

z Mapping historic events and determining return period and

magnitude (e.g. flooding)

z Heuristic analysis:

z Expert determines susceptibility to particular type of hazard usingdecision rules, or weighting methods

z Statistical analysis:

z Analyze the conditions under which hazardous events occurred in

the past using statistical relations.

z Deterministic analysis:z Simulation of the hazardous events using computer models based on

physical understanding of the processes involved.

ILWIS 2.1 concepts

Examples: landslides

Fall Topple Slide

Spread Flow


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ILWIS 2.1 concepts

Historical landslide hazard assessment

ILWIS 2.1 concepts

Heuristic landslide hazard analysis (1)


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ILWIS 2.1 concepts

Heuristic landslide hazard analysis (2)

ILWIS 2.1 concepts

Statistical landslide hazard analysis (1)


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ILWIS 2.1 concepts

Statistical landslide hazard analysis (2)

ILWIS 2.1 concepts

Deterministic landslide hazard assessment (1)


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Deterministic landslide hazard assessment (2)

ILWIS 2.1 concepts

Case study Tegucigalpa


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ILWIS 2.1 concepts

Lidar and Landslides

ILWIS 2.1 concepts

Stereo image interpretation


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ILWIS 2.1 concepts

View 3-D using analgyph image

ILWIS 2.1 concepts

Mapping landslides


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ILWIS 2.1 concepts

ILWIS 2.1 concepts

Volume calculation of landslide using DEMs


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ILWIS 2.1 concepts

New Choluteca

Bridge

Location of Destroyed Neighborhoods

New CholutecaBridge Inundated

area

Examples: Flooding

ILWIS 2.1 concepts

Example from Bangladesh using SPOT.

Processing: in SPOT band 3/Band 1 density slicing.

Assessment of inundation hazard: land and water

boundaries.


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ILWIS 2.1 concepts

Example 2: Flood modeling in BangladeshExample 2: Flood modeling in Bangladesh

ILWIS 2.1 concepts

Flood mapping through interviews


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ILWIS 2.1 concepts

Hydrological modelling

ILWIS 2.1 concepts


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ILWIS 2.1 concepts

Example: simulation of dike breach in dutch

polder.

DEM :height in cm AMSLFlood extent map; water height

260 cm.

Resultling flood depthmap.

nonflooded

flooded


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ILWIS 2.1 concepts

Modelling hazard areas for cyclone storm

surge

ILWIS 2.1 concepts

Previous works

DTM 25 m

Arequipa Peru

Modelling lahars


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ILWIS 2.1 concepts

Historical analysis: Pinatubo

ILWIS 2.1 concepts

Multi-temporal DEMs for erosion

modelling (1)


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ILWIS 2.1 concepts

Multi-temporal DEMs for erosion

modelling (2)

ILWIS 2.1 concepts

Seismic hazard assessment

z Seismic macrozonation

z Define seismic source zones

z

Characterize source zonesz Calculate Peak Ground Acceleration

for different return periods

z Seismic microzonation

z Determine site response

z Soil amplification / topographic

amplification

z Secondary seismic hazards

z Relation with buildings


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ILWIS 2.1 concepts

Overview of seismic zonation methods

z Direct characterization of ground motion

Damage mapping

Instrumental observation

z Prediction of ground motion

Regional ground shaking hazard

Deterministic ca lculat ion of ground motion

z Characterization of site

Empirical methods

(Soil category mapping, Intensity anomaly mapping

Shear wave velocity mapping, Earthquake spectral ration techniques,

Microtremor techniques (e.g. Nakamura)

Numerical simulation methods

- E.g. SHAKE

z Topography effects

ILWIS 2.1 concepts

Data needed for seismic microzonation

z Representative strong motion data from dense network

of stations

z Detailed geological information

z Borehole data, reaching up to bedrock level

z Standard penetration test data (SPT)

z Digital Terrain Model

z Shear wave velocity data


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Seismic Intensity Map I. Mid Nepal Earthquake

ILWIS 2.1 concepts

Seismic Intensity Map II.North Bagmati Earthquake


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Seismic Intensity Map III. KV Local Earthquake

ILWIS 2.1 concepts

GIS & RS case study available on

Blackboard site of CASITA from Asia

Flood hazard assessment:

Bangladesh Coastal hazard assessment:

Bangladesh Landslide hazard assessment:

Kakani, Nepal

Volcanic hazard assessment:

Pinatubo, Phillipines

Seismic hazard assessment:

Kathmandu, Nepal

Liquefaction hazard

assessment: Bhuj, India


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ILWIS 2.1 concepts

THANK YOU

using gis for hazard assessment

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