microsoft word - guidelines for development in high risk areas 2

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MM II TT II GG AATT II NNGG NNAATT UURR AALL HH AA ZZ AARR DDSS GUIDELINES FOR DEVELOPMENT IN HIGH RISK AREAS

Mitigation Planning and Research DivisionOFFICE OF DISASTER PREPAREDNESS AND EMERGENCY MANAGEMENT

Draft August 2004


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Draft Guidelines For Development in Disaster Prone/High Risk Areas

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CC OO NNTT EE NNTT SS

Forward

Introduction

Purpose of the guidelinesPurposeObjectivesPrinciplesNational Hazard Mitigation ProgrammeODPEMS Disaster Management FunctionA Synopsis of the National, Regional and Local Disaster

Management FrameworkHazard InformationFloodingLandslides

EarthquakesHurricanesStorm surgesTsunamiThe GuidelinesFloodingLandslidesEarthquakesHurricanesStorm surgesTsunamiAppendix A Guideline reference resource personnelAppendix B ReferencesAppendix C List of Hazard Maps for the ParishesList of Damage Assessment Reports for major eventsVulnerability Assessment Reports Available for the Parishes


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INTRODUCTION

The occurrences of disasters are of concern to islands and small economies such asJamaicas, as a single disaster is capable of interrupting the development process and

entire economy. Disasters have the potential to retard economic development bydestroying physical infrastructure, and the environment and invariably redirecting scarceresources to address recovery and rehabilitation.

The vulnerability of Jamaica is increasing and a number of factors have led to thisincrease. These include

Increased use of marginal (high risk) areas.Relaxing of efforts to mitigate the effects of hazardsIncreased occurrences of extreme events due to climate change

The planning process is essential for mitigation success, both before and after natural

disasters. According to Morentz et al. (1982), "Planning is a process of anticipating futureneeds and programming resource expenditures in light of expected hazardous conditionsand human vulnerabilities." Planning for natural disasters therefore, must be a dynamicand flexible process, due to the unpredictable nature of natural disasters

The ODPEM is part of a group of technical agencies that make recommendations onsubdivisions in high risk or hazard prone areas. High-risk areas are those areas that fallwithin the following criteria, and are categorized as follows:

Areas of high population density.Areas with a history of disastersContribution of the area to GNPHydrology and geology of the areaPresent disaster potential in the area.

Source: Jamaicas National Hazard Management Programme - A review of work in progress by F. McDonald and K.Ford

Development within such areas is considered special depending on the land use and thepotential impact from the hazard. Figure 2 highlights the high-risk map for Jamaica. Andfigure 3 Hazard vulnerability matrix for the country. These two maps aid in guiding theareas that will require special standards for development. Several maps within theseareas will require special permission for development and will also have to adhere to

specific standards.


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Purpose of the Guidelines

Developers of land located within Disaster prone areas are faced with additional issues ofdisaster management that must be taken into account in their project planning anddesign, and in the approval processes. Decisions must be taken in relation to the degree

of related risk to owners, occupiers and the community in general.These guidelines for development in high-risk areas are intended to assist in the planningand design of development proposals.

These guidelines set out key factors which need to be considered in assessing thedegree of risk, and the management of the risks through appropriate disastermanagement, planning and design measures.

Scope of Guidelines

The guideline document is intended to apply to all developments and subdivision of land.Under the Town and Country Planning Act (1958), development means the carrying outof any building, engineering, mining and other operations in, on, over or under land andthe making of any material change in the use of any buildings or other land.

Limitations Of GuidelinesThe techniques included in the document in some cases represent some of the morepopular techniques used to mitigate the impacts of natural hazard. The list of mitigationtechniques outlined for each hazard is by no means exhaustive as there are several othertechniques that may not have been included.

The diagrams included are not intended to be engineered diagrams but mere illustrationof the anatomy of the structures. Therefore it is expected that there must be engineeringinput into the design of the structures before they are constructed and the relevantapproval agencies including the local planning authority must give permission for theerection of these structures.

It is to be further noted that these measures are to be applied only after careful analysis ofsite conditions to determine which technique is more appropriate.

Aims And Objectives

AimThe main aim of the guidelines contained in the document is to promote sustainabledevelopment through the integration of mitigation techniques in the development of landin order to minimize the effects of hazards on lives, property and the environment.


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The objectives of the guidelines are to:Highlight the major hazards to which the island is vulnerable;Provide a set of mitigation techniques to minimize the hazards identified in order toassist in the planning, design and subsequent implementation of developmentproposals

PrinciplesThe following principles 1 apply:

The impact of natural hazards can be reduced . The information and methodsexist to minimize the effects of even the most sudden and forceful of hazardousevents and therefore prevent them from causing a disaster. While in some casesthe event itself cannot be avoided, construction methods and location decisionscan save lives and minimize damage. In cases such as flooding, the integration ofhazard mitigation measures into development planning and investment projectsmay make it possible to avoid the event altogether.

Hazard mitigation pays high social and economic dividends in a region with a history of natural disasters . Mitigation measures are seen as a basicinvestment, fundamental to all development projects in high-risk areas, and not asa luxury that may or may not be affordable.

Hazard Management is most effective in the context of integrated development planning . The focus should not just be on the sector that is beingdeveloped but on all who share the same physical defined space

Natural Hazard considerations should be introduced at the earliest possible stage in the development process. If a site lies in a fault zone it may be subject

to earthquakes and that information should be known beforehand so that it isplanned for in the development. When natural hazards are identified earlier in theplanning it can influence the original formulation of the project. Projects can berestricted based on the level of risk involved.

Use Common Sense . People know the kinds of hazards that occur in theirneighbourhoods. They may not know how to quantify these hazards or the bestways to mitigate them, but they understand something must be done about them.

Legal And Policy Framework For Disaster Mitigation

Disaster Preparedness and Emergency Management Act, 1993The main aim of the Office of Disaster Preparedness and Emergency Management underthis Act is to advance disaster preparedness and emergency management measures inJamaica by facilitating and co-coordinating the development and implementation ofintegrated disaster management systems.

1 The principles have been adopted from Disaster, Planning and Development: Managing Natural Hazards to reduceloss. Organization of American States (OAS), 1990.


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The functions of the Office includes:

1. Enhancing public awareness of disaster related issues2. Encouraging and supporting disaster preparedness and mitigation measures in all

parishes in collaboration with local government authorities, community based

organizations and the private and voluntary agencies respectively.3. Developing and enhancing policies and programmes aimed at achieving a highlevel of preparedness to cope with emergency situations.

The office also has a duty to encourage measures for mitigating the effects of hazardsand to reduce losses from disaster.

Hazard Mitigation Policy (Draft 2002)Currently the ODPEM has a draft Hazard mitigation Policy, which was adopted at aworkshop, sponsored and facilitated by CDB/DMFC, NEPA, PIOJ, ODPEM and USAID.

The purpose of the policy is to provide a framework for integrating hazard mitigation intoall policies programmes and plans at the national and community levels. It sets out thebroad goals and guiding principles for hazard risk reduction, and thus informs thedevelopment of any national hazard mitigation plans. The policy specifically addressesthe mitigation aspect of disaster management.

The policy recognizes some of the sources of vulnerability as inappropriate land use andconstruction on marginal lands such as flood plains. It further recognizes that vulnerabilitycan be reduced by the avoidance of hazard prone areas and carrying out proper design,construction and maintenance of buildings and infrastructure. In this regard the guidelinesis intended to provide the public, especially local authorities and those involved indevelopment with a set of guidelines that will act to mitigate the hazards identified.

A Synopsis of the National Disaster Management Framework

The disaster management framework can be broken down into 3 broad categories;1. Pre disaster mitigation measures2. Disaster preparedness and response measures3. Post disaster recovery and reconstruction measures


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PART 1

Hazard IdentificationThe natural hazards to which the island is vulnerable are as follows:Hurricane Storm SurgesFlooding TsunamiEarthquake LandslideBush Fire

HURRICANES

HAZARD ASSESSMENTHurricanes are tropical cyclones with wind speeds of 75 miles per hour (m.p.h), or greaterwhich develop into severe storms characterized by winds directed inward in a spiraling

pattern toward the center. They are generated over warm ocean water at low latitudesand are particularly dangerous due to their destructive potential, large zone of influence,spontaneous generation, and erratic movement. The phenomena that are associated withhurricanes are:

Winds exceeding 64 knots (74 mi/hr or 118 km/hr). This wind speed defineshurricane force winds. Damage usually results from the winds direct impact onfixed structures and from wind-borne objects.

Heavy rainfall, which commonly precedes and follows hurricanes for up to severaldays. The quantity of rainfall is dependent on the amount of moisture in the air, thespeed of the hurricanes movement, and its size. On land, heavy rainfall can

saturate soils and cause flooding because of excess runoff (land-borne flooding); itcan cause landslides because of added weight and lubrication of surface material;and/or it can damage crops by weakening support for the roots.

Storm surge, especially when combined with high tides, can easily flood low-lyingareas that are not protected.

Effects of Hurricane Air moving at high speed becomes a very destructive agent mainly because of the

force extended by the wind. Increased rainfall which becomes an agent of destruction by causing flooding Damage to small buildings Damage to glass in windows and lightweight walls Damage to power supply


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Vulnerability Analysis It is very important that hazards be evaluated in order that project engineers candetermine the most appropriate design criteria for each development. The mostdestructive elements of a low-pressure system are wind and water force. Therefore, thevulnerability of existing or proposed structures must be assessed.

Construction Weight.Lightweight structures are more vulnerable to hurricanes as they can be easily blownaway or can sustain severe damage.

Stability Construction should be able to resist horizontal force due to strong winds. Diagonalbracing therefore becomes very important in construction practice, especially inlightweight structures.

Connections between Structural Elements

Connection between the various structural elements of a building can affect thevulnerability of a building. If joints are improper, the roof will be blown off. It is alsoessential that the walls be appropriately connected to its foundation in order to preventthe structure being displaced.

Dia ram 1: The Effects of Hurricanes


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Mitigation Measures For Hurricane

Standard for Hurricane ProtectionAfter Hurricane Gilbert, which affected Jamaica in 1988, the national building codes/standards were reviewed. A minimum standard for retrofitting and reconstruction of structures to withstand hurricane winds up to 130 MPH or a category 3 hurricane. The use of hurricane straps is mandatory.

Hurricane Protection MeasuresA new development in an area prone to effect of a hurricane can be carried out providing:

a. Selection of good foundation for soil, which will not loose its bearing capacity wheninundated.

Porchesb. Reinforce porches as they are a major source of weakness in a buildingc. Avoid half porches, as wind trapped underneath an open or half porch will increase

high uplift forced on the roof.

d. Buildings should be well anchored and connected together.e. The use of bracing for stability is crucial (important in Hall Type Buildings such as

schools)f. Window frames should be well anchored in wall.g. Use timber or metal louvers if possible as they have been proven to have the

highest resistance to damage. Glass is prone to shattering from flying debris.h. Separate doors from windows if possible.

Dia ram 2: A ro riate Desi n for Porches


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i. Buildings can be protected by planting trees no less than 15m from the buildingsand there should be no unnecessary felling of trees which will act as windbreaksespecially on coastal areas.

j. Provide shutters for windows and doors, especially glass which has very littleresistance to wind.

Roofsk. Minimize the use of flat or low-pitched roofs. Hip roofs are best and roofs should not

be pitched less than 15 0C.l. Section 4.1.2 of the National Building Code provides the basis of design for wind

pressures and stresses due to wind loading.

m. Avoid verges, eaves and overhangs longer than 18.n. Rafter should be attached to wall plates with twisted metal strapso. Pockets under eaves should be minimized by boarding or sheeting to the

underside. Detail at ends of eaves should protect open edges of sheet of sheetcovering to avoid uplift.

p. Fascia boards must be installed

Specifications for Galvanized Shingle Roof Hurricane twisted straps to every rafter 26 Gauge Alusteel or Galvalume Sheeting should be used. Wall plates to hold down bolts at 1050 mm centers. Maximum specification of timber purling 900 mm. Use more fixings to secure sheeting that are thin. Putting the laths at closer

centers and the nails closer together can do this. See table below:

Dia ram : Desi n of a House for Hurricane


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Gauge Of Sheeting Spacing Of Lath28 18 ins 2ft.26 2ft. 2ft. 6ins24 2ft for nails

3ft. for screws

Flooding and Landslide from hurricanes (see parts 2&4)


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STORM SURGE PROTECTION MEASURES

Guidelines for development in Flood Prone Coastal Areas

A new development in an area prone to flooding or storm surges can be permitted

providing:a. Developments be set back appropriately from the coastal high water markaccording to the distances specified in the manual for development. The line ofpermanent vegetation can also be used as a base for setbacks. For areas wherestorm surge maps exist, the maximum-recorded surge distance and surge heightcan be used as a guide (see appendix showing storm surge maps for the northcoast) for offsetting developments from the coastline.

b. Buildings should be constructed at higher elevations , with timber piles or poles onconcrete piles or columns embedded in grain so that the first floor structure is at thehigh water level. Care must be taken in using this strategy as it must be ensuredthat the design takes into consideration water, wind, waves, velocity and erosion.

c. On Limestone Cliffs development should be set back at a minimum 30m after thenatural vegetative line.d. Critical facilities should not be located in areas susceptible to storm surges.(see

appendix showing list of critical facilitiese. No development will be permitted seaward of the baseline of permanent vegetation,

except for jetting and docking facilities

For Existing Development Located in Storm Surges Areas.a. Retrofitting of structures may be required.b. An evacuation plan will be required.

TECHNIQUES FOR MITIGATING COASTAL FLOODING

The following mitigation strategies have been adopted from the Alabama HazardMitigation Strategies. The information is available at the web site www.csc.noaa.gov .These techniques are methods of shoreline stabilization, which is part of the set ofmitigation measures for ocean flooding. It should be noted that these strategies shouldnot be employed without the requisite approval from the relevant approval agencies orwithout the requisite Environmental Impact Assessment (EIA) if required.

Beach Fill


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Beaches are a first line of defense against erosion damage, protecting the area behindthem. In normal weather, gently sloping beaches cause incoming waves to break and useup their energy before reaching inland areas. A beach that is relatively stable or growingprovides natural protection to the land behind it. When there is loss of beach material,which results in the beach area shrinking, there is increased danger of damage as the

water line advances inland.Adding fill to a beach, either to replace the lost beach materials or to increase the size ofan existing beach, is often both economical and effective. As shown above, addition of fill

Increases the width of the backshore, moving the high water line farther offshore.Should resemble the original beach material: coarser fill will erode more slowly,finer fill, more quickly, than the native beach.Should also match the natural slope as closely as possible. Beach fill is often usedin combination with construction of a perched beach or groin field.

Breakwaters

Breakwaters are structures placedoffshore to dissipate the energy ofincoming waves. Large breakwaterssuitable for protecting deep harborsare generally beyond the resources ofthe individual property owner. Thebreakwaters may be small structures,placed one to three hundred feetoffshore in relatively shallow water,designed to protect a gently sloping

beach. As shown above, thedissipation of wave energy allows driftmaterial to be deposited behind the breakwater. This accretion protects the shore andmay also extend the beach. The amount of deposition depends on the site characteristicsand the design of the breakwater. Breakwaters may be either fixed or floating: the choicedepends on normal water depth and tidal range. These structures can be designed tomitigate against waves of various heights.

GroinsGroins are structures that extend,

fingerlike, perpendicularly from theshore. Usually constructed in groupscalled groin fields, their primarypurpose is to trap and retain sand,nourishing the beach compartmentsbetween them. Groins initially interruptthe longshore transport of littoral drift.They are most effective wherelongshore transport is predominantly in


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one direction, and where their action will not cause unacceptable erosion of the down driftshore. When a well-designed groin field fills to capacity with sand, longshore transportcontinues at about the same rate as before the groins were built, and a stable beach ismaintained.

RevetmentsRevetments are structuresplaced on banks or bluffs insuch a way as to absorb theenergy of incoming waves.They are usually built topreserve the existing uses ofthe shoreline and to protect theslope. Like seawalls,revetments armor and protect

the land behind them. Theymay be either watertight,covering the slope completely, or porous, to allow water to filter through after the waveenergy has been dissipated.

Most revetments :Do not significantly interfere with transport of littoral drift.Do not redirect wave energy to vulnerable unprotected areas, although beaches infront of steep revetments are prone to erosion.

Materials eroded from the slope before construction of a revetment may have nourished aneighboring area, however. Accelerated erosion there after the revetment is built can be

controlled with a beach-building or beach-protecting structure such as a groin or abreakwater.

Vegetation

Vegetation is an effective andinexpensive way to stabilizedunes and protect marshes. Inundisturbed environments,vegetation is often one of the

most important elements in thenatural protection of the land.Roots and stems tend to trap finesand and soil particles, formingan erosion-resistant layer oncethe plants are well established. In

marshes, vegetation also absorbs some of the water's energy, slowing down potentiallyerosive currents. It should be noted that other mitigation strategies may need to be usedalong with those mentioned above.


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Sea Walls

A seawall is a vertical, sloping, or stepped wall which protects a shoreline from erosionand other wave action. Seawalls are normally constructed of concrete or stone masonry.However, engineers have had some success with designs using steel, timber, and rubble.

Types of Sea Walls 1. Masonry seawalls . Seawalls resist the full force of waves. They are designed as

massive gravity-type retaining walls, with additional stability to resist wave andstorm action. A curved-face seawall and a combination stepped and curved-face

seawalls are shown in thediagram. Engineers buildthese structures to resist highwave action and to reducescour. Both seawalls havesheet pile cutoff walls at each

end. These prevent loss offoundation material by wavescour or storm drainagebeneath the wall. The curved-face seawall has an armoringof large rocks at the seaward

toe to reduce wave scour.

2. Cast-in-place concrete . Concrete is deposited underwater for leveling oldfootings, stabilizing rock fills, or setting new footings or walls. Bottom-dump

buckets with closed tops or tremies make the deposits. During placement, thelower end of the tremie is kept below the surface of the fresh concrete. Footingforms are usually light sheet piling. Wall forms are prefabricated and sunk in place.

3. Precast concrete blocks . First, engineers cast in place concrete footings withlevel tops; then they set precast blocks in place. These blocks are provided withrings for crane slings. Blocks are set in contact without mortar below low water.Joints are filled with mortar above low water. Divers may position the blocksunderwater. The end joints of the blocks may be battered to improve the contact.

4. Stone masonry . Stone is sometimes a suitable alternative to concrete masonry.

5. Rubble-mound seawalls . The rubble-mound seawall may be a cheaper, moreeasily designed seawall..Despite scour of thefronting beach, rockcomprising the seawallcan settle withoutcausing structural failure.The diagram shows a

-

Source: www. lobalsecurit .or / ... / arm /fm/5-


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The following table can be used as a guide for Permissible uses within the flood plain of ariver.

Two- Zone 3 Single Zone 2 Floodway Floodway Fringe

PermittedUse Agricultural uses such as farming,pasture, outdoor plant nurseries,horticulture.Industrial uses such as loading areas,parking, and airport landing strip.Recreational uses such as parks, golfcourses, picnic grounds etc.Residential uses such as lawns,gardens, parking areas.

All uses permitted inthe Single-zone All uses permitted in theflood way.Structures constructedon stilts or fill so firstfloors are aboveregulatory floodelevation.

SpecialExceptions

For-structures - a technicalassessment is required of the actualflood level. Increases that may becaused by proposed developmentsneeds to be assessed so thatregulatory standards for its approvalcan be applied. Consideration of theeffects shall be based on theassumption of equal degree ofencroachment over an extendedreach of both banks.

**Structures notdesigned for humanhabitation, have lowdamage potential andminimal obstruction toflood flows.Transient amusemententerprises: circus,carnivals.Drive-in theatres, carparksSand and gravel miningStorage for materialand equipment

Usage permitted in theflood way.

**Structure acting alone or in combination with existing or future use should not increase the flood heights above some threshold level. NB. This requires that a hydraulic assessment be done.

The two-zone approach should be use din urban areas and other areas subject todevelopment pressure and every effort should be made to obtain the necessary data forhydrologic and hydraulic studies to demarcate flood boundaries.

2 In the single-zone approach a single zone is demarcated as the regulatory flood boundary. This zone can be base dontechnical studies or from historical floods or high water marks. This approach is most appropriate for rural areasundergoing scattered developments and is likely to attract large sub-divisions. Areas with steep valley slopes, unstablebanks and poor soils and areas with frequent flooding occurrences are also suitable for this approach.3 This approach divides the regulatory flood boundary into a floodway and a floodway fringe. The former is the area of the channel which is kept open to carry flood water, no building or fill is allowed. In the latter zone, use is permitted if it is protected by fill, flood proofed or otherwise protected.


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www.louisiana flood s.org/ fpdocs/Flood%20Proofing%20Matrix.doc

Based on FEMAs Flood Proofing/Retrofitting Decision Matrix From: Flood Proofing How to Evaluate Your Options, US Army Corps of Engineers,

National Flood Proofing Committee, July 1993

FLOOD PROOFING MEASURES

FLOODPROOFINGMATRIX

E l e v a

t i o n o n

F o u n

d a t

i o n

E l e v a

t i o n o n

P i e r s

E l e v a

t i o n P o s t s

o r

C o

l u m n s

E l e v a

t i o n P

i l e s

R e l o c a

t i o n

F l o o

d w a l l s

a n d

L e v e e s

F l o o

d w a l l s

a n d

L e v e e s w i t

h

C l o s u r e s

D r y

F l o o d

P r o o

f i n g

W e t

F l o o d

Flood DepthShallow (less than 3feet)Moderate (3 to 6 feet) N/ADeep (greater than 6feet)

N/A N/A N/A N/A

Flood VelocitySlow (less than 3 fps)Moderate (3 to 5 fps) N/A N/AFast (greater than 5fps)

N/A1 N/A1 N/A1 N/A1 N/A N/A

Flash FloodingYes (less than 1 hour) N/A 1 N/A2 N/A2 N/A2

F l o o d i n g

C h a r a c

t e r i s t i c s

NoSite LocationCoastal Floodplain N/A N/A N/A N/A N/ARiverine FloodplainSoil TypePermeable N/A 3 N/A3 N/A

S i t e

C h a r a c -

t e r i s

t i c s

ImpermeableBuilding FoundationSlab on GradeCrawl SpaceBasement N/A N/A N/A N/A N/A 4

Building ConstructionConcrete or Masonry N/A 5

Wood and Others N/A 5 N/A N/A4

Building ConditionExcellent to Good

B u

i l d i n g

C h a r a c

t e r i s t

i c s

Fair to Poor N/A N/A N/A N/A N/A N/A N/A


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Mitigation Techniques For Flood Prone AreasThere are a variety of techniques available to the developer to minimize the impact offlooding on a development. Individuals who are constructing their own units can alsoutilize some of these methods.

Flood ProofingFlood proofing has been defined as "any combination of structural or non-structuralchanges or adjustments incorporated in the design, construction, or alteration of individualbuildings or properties that will reduce flood damages." More simply put, it is anything youdo to reduce flood damage to your building or its contents. Flood proofing is personalflood mitigation; it may be supported by community mitigation programs.

As a property owner, you benefit from floodproofing in several ways:

Spend less on repair and cleanup after a flood;

Reduce hours away from work while recovering from flood damage; Avoid other inconveniences caused by flooding; Preserve the integrity of the building; Reduce the risk of deteriorating indoor air quality and other health hazards often

experienced in flood-damaged homes; and Possibly enhance the value of your property.

Floodproofing can create peace of mind and reduced anxiety.

By floodproofing a shop, warehouse or office building you may avoid lost wages, reducedprofits and other costly business interruptions

A. ElevationThis technique involves raising an entire structure above flood hazard. Theheight of the elevation is dependent on the Base Flood Level (BFL). If there areno regulatory base flood levels, then the known flood levels should be used as aguide. In using this method the following must be noted however:

Avoid supporting structures on spread footing, as they cannot accommodatemuch scouring without collapsing. Piles should be adequately designed toprevent failure.

Make sure that exterior walls have been designed to withstand the velocityflows of flood water or wave action.

All structural elements should be tied together to resist positive and negativeloads.


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Figure 1. House Elevated over Garage House Elevated over Garage

Source: http://www.usace.army.mil/inet/functions/cw/cecwp/NFPC/fplfpp/ace7-02.htm

The photographs below show how a house can be constructed so that it is elevatedabove flood levels, without losing its aesthetic appearance.

B. LeveesThese are embankments ofcompacted soil that can keep shallow

to moderate flood waters fromreaching a site. In this technique thereis no water pressure in the houseitself. These should be used only withthe approval of the respectiveauthority as they can impede thenatural flow of water in a flood plain,possibly resulting in increased flooding

of adjacent property. A suitable fill material for the levee is necessary.


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C. FloodwallsThese are barriers of man-made materials that can be used to protect a structure

from flooding. A floodwall can beconstructed using a variety ofdesigns and materials and can beused to protect practically any typeof structure. Floodwalls also havean added function that ofenhancing the appearance of thestructure.

D. ClosuresMany of the flood protection measures require special treatment for openingssuch as doors, windows, driveways etc. These closures act as shields to coverthe gap to prevent water from entering and can be a variety of shapes, sizes andmaterials.

E. Dry Flood proofing (Sealants)This method involves completely sealing the structure against the entry of water.This method can only be employed for buildings that are in good structuralconditions.

Storm Water Management In Urban AreasOverland/surface flooding with urban areas has become a significant problem in many ofthe towns. Localized flooding from rainfall can adversely affect many communities and


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surrounding areas in land areas such as low lying areas. Localized flooding from strongthunderstorms is also common. Flooding by poor drainage construction.

To prevent developments from creating a flood problem for surrounding properties, thefollowing guidelines should be adhered to:

1. Drainage systems need to cater for flood events in Urban Areas within a 1-5 yearsreturn period.

2. Ensure that flooding problems are not made worse or that other properties are notaffected by:

Avoiding re-direction of surface flow. Minimizing the number of areas on a site that contains hard surfaces in

order to minimize storm water run-off. All new developments should as far as possible incorporate sustainable

drainage measures to avoid adding to flood risks elsewhere and toencourage developers to promote building designs that are better able to

withstand flooding, and which, when flooded can recover faster.


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PART 3

EARTHQUAKES

Earthquakes are caused by the sudden release of slowly accumulated strain energyalong a fault in the earths crust. Earthquakes and volcanoes occur most commonly atthe collision zone between tectonic plates. Earthquakes represent a particularly severethreat due to the irregular time intervals between events, lack of adequate forecasting,and the hazards associated with these:

Ground shaking is a direct hazard to any structure located near the earthquakescenter. Structural failure takes many human lives in densely populated areas.

Faulting, or breaches of the surface material, occurs as the separation of bedrockalong lines of weakness.

Landslides occur because of ground shaking in areas having relatively steeptopography and poor slope stability.

Ground shaking can trigger liquefaction of gently sloping unconsolidated material.Flows and lateral spreads (liquefaction phenomena) are among the mostdestructive geologic hazards.

Subsidence or surface depressions result from the settling of loose orunconsolidated sediment. Subsidence occurs in waterlogged soils, fill, alluvium,and other materials that are prone to settle.

Tsunamis or seismic sea waves, usually generated by seismic activity under theocean floor, cause flooding in coastal areas and can affect areas thousands ofkilometers from the earthquake center.

Tsunamis

Tsunamis are long-period waves generated by disturbances such as earthquakes,volcanic activity, and undersea landslides. The crests of these waves can exceed heightsof 25 metres on reaching shallow water. The unique characteristics of tsunamis (wavelengths commonly exceeding 100 km, deep-ocean velocities of up to 700 km/hour, andsmall crest heights in deep water) make their detection and monitoring difficult.Characteristics of coastal flooding caused by tsunamis are the same as those of stormsurges.

Earthquake Protection MeasuresA level two (2) earthquake and ground motions correspond to levels of shaking that have a more remote probability of occurrence during a life of a structure. This level of exposure corresponds to the exposure times specified for building design in the Caribbean Uniform Building Code (CUBiC) and other national building codes.This level is also designated the contingency level earthquake for any ports and harbour facilities (Werner, 1998) See map showing epicenters from 1998 2003.


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Guidelines for development in Seismic prone areas.

For development in seismic prone regions, special building codes should be prepared.

These codes should include:1. Techniques for constructing resistant construction using various building material.2. Building should be built to the required safety factor.3. Effects of local geological conditions on the intensity.4. Buildings should be designed two (2) seismic locals for type of use.

NB The National Building Code of Jamaica, 2 nd Edition, contains guidelines forbuilding construction, that is, general requirements, public safety requirements,material and construction standards, service requirements and miscellaneousrequirements. For earthquake loads, section 4.1.3.1 speaks to the basis for design:

Every building and structure and every portion thereof shall be designed and constructed in accordance with the latest edition of Recommended Lateral Force Requirements and Commentary by the seismology Committee of the Structural Engineers Association of California .

The ODPEM recommends that all developments MUST be submitted to the LocalPlanning authority for approval prior to construction. That way, conformity with theBuilding Code can be ensured.

Tsunami Protection Measures

Developments may be permitted in areas prone to tsunamis provided that certainprecautions are observed.

Criteria for development in the above areas ( see also mitigation measures for coastalflooding ):

a. Precautions for the quick drying of immersed houses are similar to those in thecase of inundation.

b. The protection of settlements on the coast against tsunami by the construction ofembankments and flood walls is very expensive and can be justified economicallyonly in special cases.

c. The most efficient way of protecting buildings in the tsunami areas is theconstruction of new settlements, if possible above the locally acceptable risk level.

d. Buildings and houses in tsunami areas should be built of solid material (brick,concrete) to be able to resist the horizontal drag exerted on them, whilesubmerged.

e. If the coast topography is flat, the protection of structures against tidal waves canbe provided by supporting structures on timber piles and poles or concrete pilesand columns to provide a sufficient clearance of the structure above high waterlevel.


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PART 4

LANDSLIDES

The term landslide includes slides, falls, and flows of unconsolidated and weatheredmaterials. Earthquakes, volcanic eruptions, soils saturated by heavy rain or groundwaterrise, and river undercutting, can trigger landslides. Earthquake shaking of saturated soilscreates particularly dangerous conditions. Although landslides are highly localized, theycan be particularly hazardous due to their frequency of occurrence; especially during hurricanes . Classes of landslide include:

i. Rock falls, which are characterized by free falling rocks from overlying cliffs. Theseoften collect at the cliff base in the form of talus slopes which may pose an additionalrisk.

ii. Slides and avalanches , a displacement of overburden due to shear failure along astructural feature. If the displacement occurs in surface material without totaldeformation it is called a slump.

iii. Flows and lateral spreads , which occur in recent unconsolidated materialassociated with a shallow water table. Although associated with gentle topography,these liquefaction phenomena can travel significant distances from their origin.

The impact of these events depends on the specific nature of the landslide. Rock fallsare obvious dangers to life and property but, in general, they pose only a localized threatdue to their limited aerial influence. In contrast, slides, avalanches, flows, and lateralspreads (sediment water flows), often having great aerial extent, can result in massiveloss of lives and property table x. Mudflows (lahars), associated with volcanic eruptions,can travel at great speed from their point of origin and are one of the most destructivevolcanic hazards.

Table X: Magnitude rating and range of landslide

However within the Jamaican context, are the ill effects of sediment water flows:channelised down slope flow of saturated and weathered material (colluvium).


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With this consideration it is necessary to develop a nation wide strategy for managinglandslides in high-risk areas. The initiation of a landslide risk management project willcover Risk analysis and Risk assessment.

Risk analysis involves the preliminary analysis and risk estimation. It includes thesystematic use of information to identify hazards and to estimate the chance for, andseverity of, injury or loss to individuals or populations, the environment or other things ofvalue.

Risk Assessment involves a combination of risk analysis and the step of risk evaluationto determine if the risk is acceptable or tolerable. It does not include considering optionsfor risk control, nor does it includes actions to control risk or monitor performance of siteworks over time.

Collectively Risk management as illustrated by figure x is a complete process involving

all six steps in the decision making frame work and communicating about risk issues seefigure x.

Landslide Mitigation Measures (from an administrative perspective)Proposed development should be in harmony with the environment and developmentshould not cause slopes to be unstable or increase the rate of soil erosion greater than Xper year:

Figure x: The Risk Management process(source: Doug VanDine Landslide Risk Case Studies In Forest Development Planning

& Operations 2004)


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With reference to slopesProhibition of development on slopes with a gradient greater than XStabilization of slope toe to obtain stable angle of repose in slope

Buildings

If buildings are to be erected in landslide areas, structures of statisticallydetermined type are recommended.In areas that are heavily faulted and have steep slopes the construction of anybuilding in landslide prone areas should be forbidden.

Landslide mitigation MethodsLandslide mitigation methods incorporate the specific strategies utilized to reduce lossfrom the hazards of landslides/sediment water flows. This methodology as indicated byTable x, categorizes the mitigation plan that can be utilized for all high-risk areas of theisland.

Table X: Landslide mitigation Methodology

Bio-technical Slope Protection

In such work, vegetation is used as surface protection and to augment the strength of thesoil in which it grows, usually combined with naturally occurring or recycled inert materialssuch as timber, burlap, aggregate and rocks. This methodology is particularlycommendable on farms in high-risk areas such as coffee farmers in the Blue and Johncrow mountains, farmers in the Cockpit country and road cut areas adjacent to steepslopes.

MITIGATION METHODOLOGYPassiveUsually involves no direct engineering

ActiveUsually involves engineering

Methods thatreduce drivingforces

Methods thatincrease resistingforces

Avoidance

Relocation

PreventionincludingMaintenance

Regulationeg. Sub-division applications StabilizationWarning systemseg. Trip wires, stream water level, soilchanges Education

RemovingDetritus from

Talus slopes

Protection ofdownstream/downsloperesources


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Reinforced Earth

Technically the methodologyentails the combined approach

using vegetated geogrids toprovide the much-neededsurficial stability and to supportlong-term vegetative growthwith almost no maintenancerequirements. The geogrid is ahybrid design that incorporatesbrushlayers in the frontal,wrapped portion of theReinforced Soil Slopes. Overtime the live branches take root

and increase the internalstability of the reinforced slope.Figure x. Cross section of remedial slope designSource: http://www.sotir.com/pubs/publist/slope_failure/slope_failure.html

Live Facines (figure x) are constructed on the crest of slopes to prevent surface erosionand rapid re-vegetation ofslopes. The remedial design asdemonstrated in figure xreduces surface failures andeven deep seated landslides inareas as high as 150 m; thisentails:

Stabilize slopes to 4V:1Hratio

Creating an aestheticallypleasing landscape

Excavate failed slopeback to 6m.

Allow drainage panelthrough crushed stone borrows

Figure x: Cross-Section of the Live Facines.

Source: http://www.sotir.com/pubs/publist/slope_failure/slope_failure.html

Other Types of Bio-technical Slope ProtectionRetaining WallsLog and Timber CribsRock Breast WallsContour Farming/Landuse


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Slope Stability Hazard Mitigation

Slopes that possess factors of safety less than required by the governing agency, or withunacceptably large seismic slope displacements, require avoidance or mitigation to provetheir stability. Even if a slope is found from analyses to be stable, it might requireprotection in order to avoid degradation of shear strengths from weathering, to remainstable under future increased loading conditions, to prevent toe erosion, or to remainstable under future, potentially higher groundwater conditions than assumed in theanalyses. Protection for adjacent pad areas may also be required to minimize hazardfrom erosion and falling debris.

The most common methods of mitigation are (1) hazard avoidance, (2) grading toimprove slope stability, (3) reinforcement of the slope or improvement of the soil within the

slope, and (4) reinforcement of the structure built on the slope to tolerate the anticipateddisplacement.

The mitigation measures chosen for a given slope must be analyzed recognizing thatdifferent mitigation measures require analyses for different modes of failure. Somemethods (for example, slope reinforcement) require consideration of strain compatibilityand soil/structure and/or soil material interaction issues. The following sections describeboth stabilization and mitigation measures, and the potential modes of failure that shouldbe analyzed.

AvoidanceThe simplest method of mitigation may be to avoid construction on or adjacent to apotentially unstable slope. A setback distance for structures or other improvements/usescan be established from the slope such that failure of that slope would not pose a dangerto site improvements. The setback distance is based on the slope configuration, probablemode of slope failure, factor of safety, and potential consequences of failure. Wherefeasible, an estimate of the "runout" that would occur in the event of a slope failure shouldbe made. The required setback cannot generally be accurately calculated; therefore alarge degree of engineering/geologic judgment is required.

GradingGrading can often be performed to entirely or partially remove potentially unstable soil tocreate a finished slope with the required factor of safety. The available grading methodsrange from reconfiguration of the slope surface to a stable gradient, to removal andrecompaction of a soil that is preferentially weak in an unfavorable direction and itsreplacement with a more homogeneous soil with a higher strength.

ReconfigurationThe stability of a slope can be improved by reducing the driving forces as a resultof flattening the slope and/or decreasing its height. The reconfigured slope must be


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analyzed and must have at least the minimum required factor of safety or less thanthe maximum allowable seismic displacement.

Removal and Replacement

It may, in some cases, be feasible to completely excavate (remove) earth materialsthat contribute to the instability of a slope and replace the excavated soil withhigher-strength materials that result in a slope with the minimum required factor ofsafety. Materials that typically contribute to slope instability, and can often becompletely removed, include slopewash (colluvium) and landslide debris.Complete removal of an active landslide does not preclude the possibility of deeperseated sliding, which also should be checked in the analysis. The slope createdshould be analyzed for internal stability (within the replaced soil mass) and externalstability (through the remaining native soil) Often, the excavated material is reusedas fill, although, in some instances, new soil must be imported, if the strength ofthe existing soil when recompacted is inadequate.

Stability FillsA stability fill is used where a slope has an adequate factor of safety for grossstability, but an insufficient factor of safety for surficial stability or where thematerials exposed at the slope surface are prone to erosion, sloughing, rock falls,or other surficial conditions that require remediation. Stability fills are relativelynarrow, typically about 10 to 15 feet wide.

Stability fills should be keyed into firm underlying soil or competent bedrock. Thekey should be at least as wide as the stability fill and should extend at least 3 feetbelow the toe of the slope. Both the gross and surficial stability of the stability fillshould meet the minimum stability requirements set by the governing agency.

Buttress FillsA buttress fill provides the features of a stability fill, but is used where a slope does

not have a sufficient factor ofsafety for gross or deep-seatedstability and additional resistiveforces are required. For example,buttress fills can be used tosupport upslope landslides orslopes in sedimentary rock wherethe bedding is adversely dippingout of the slope.

The base of a buttress fill istypically wide, usually ranging from

about one third to almost the full height of the slope being buttressed. The actualwidth of the buttress must be determined by slope stability analysis. Soil placed inthe buttress fill should be compacted to minimum requirement. Water content alsoshould be controlled. Buttress fills should be keyed into competent underlying


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materials. The key should be at least as wide as the base of the buttress fill andshould extend at least 3 feet below the toe of the slope. The required depth of thekeyway must be evaluated by slope stability analysis. A typical buttress isillustrated in Figure (9.1f).

Shear KeysIn some cases, the shear resistance of soil along a deep potential failure plane canbe significantly increased by excavating a keyway into competent material belowthe potential failure surface and backfilling the keyway with compacted fill, slurry,or concrete. Stability analyses for slopes with a shear key should be performedusing an appropriate shear strength for the keyway backfill material. Potentialfailure surfaces passing through and beneath the shear key should be considered.

Sub drainsTwo types of subdrains can be used to maintain low water pressures within

engineered slopes: backdrains and chimney drains.Backdrains are generally used behind stability fills, buttress fills, andbeneath zones of total removal and replacement to maintain low water-pressures. Backdrains can consist of a 4-inch-diameter perforated or slottedpipe for small slopes or slopes where frequent outlets can be provided.Larger-diameter pipes may be required where significant quantities of waterare anticipated or where the distance to an outlet point exceeds 200 feet.

The purpose of a chimney drain is to collect subsurface water from multiplebedding planes. The use of chimney drains is particularly important forbuttress fills that will support bedded rock with considerably differentpermeability between layers. Conventional near-horizontal subdrains oftenwill not collect water from the permeable layers because they do notintersect or cross the permeable beds. The chimney drains should becontinuous between lateral backdrains and should be a minimum of 2 feet inwidth. Chimney drains may be created by stacking gravel-filled burlap (notwoven plastic) bags, placement of a continuous gravel column surroundedby non-woven filter fabric, or placement of a drainage composite. Drainlocations and outlet pipes should be surveyed in the field at the time ofinstallation.

ENGINEERED STABILIZATION DEVICES AND SOIL IMPROVEMENTA grading solution to a slope stability problem is not always feasible due to physicalconstraints such as property-line location, location of existing structures, the presence ofsteep slopes, and/or the presence of very low-strength soil. In such cases, it may befeasible to mechanically stabilize the slide mass or to improve the soil with admixturestabilization. The resulting slope should be analyzed to meet the same requirements asother slopes. Mechanical stabilization of slopes can be accomplished using retainingwalls, deep foundations (i.e., piles or drilled shafts), soil reinforcement with geosynthetics,tieback anchors, and soil nails. Common admixture stabilization measures includecement and lime treatment as well as Geofibers TM.


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Deep FoundationsThe factor of safety of a slope can be increased by installing soldier piles/drilled shaftsthrough the unstable soil into competent underlying materials. The piles/drilled shafts aresized and spaced so as to provide the required additional resisting force to achieve

adequate slope stability.Soldier piles/drilled shafts used to stabilize a slope may also be used to support otherstructures, provided the structures can tolerate the deflection that can be reasonablyexpected to occur. If the location of piles/drilled shafts relative to other engineeredimprovements is such that deflections of the deep foundations are of concern, deflectionscan be calculated based on soil properties evaluated.. Soldier piles/drilled shafts used tostabilize the slope and provide support for a structure should be tied in two lateraldirections such that the potential for lateral separation is minimized.

Tieback Anchors

The loads on the soldier piles/drilled shafts are, in some cases, higher than theseelements can support in cantilever actionalone. Tieback anchors can be incorporated inthose cases to provide additional resistance.Tieback anchors also can be used withoutsoldier piles/drilled shafts by anchoring themagainst a wall or reinforced face element.Tieback anchors consist of steel rods or cablesthat are installed in a drilled, angled holes. Therods/cables are grouted in place within thereaction zone and extend through a frictionlesssleeve in the unstable mass. The anchors arepost-tensioned after the grout reaches its

design strength. Anchors are often tested to a load that is higher than the design load.The anchors must be long enough to extend into stable earth materials.

Temporary anchors generally do not need to be protected from corrosion. Permanentanchors should be protected from corrosion for the design life of the project.

Soil Nails

Soil nailing involves earthreinforcement by placing andgrouting reinforcing rods in holesdrilled in the ground. Thereinforcing rods are not pre-stressed or post-tensioned. Soilnailing should not be used inrelatively fines-free gravel andsandy soil. Soil nailing forpermanent slope stabilization has


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been widely used in some areas of the USA in Public Works projects. The application ofthis technique for general use is currently being studied.

Retaining Structures

A retaining wall can be constructed through an unstable slope to provide additionalresistance and raise the factor of safety for material behind the wall to an acceptablelevel . Retaining structures should be founded in stable earth materials . The retainingstructure should be evaluated for possible sliding, overturning, and bearing failures usingstandard techniques. Failure surfaces that extend below the wall foundation and abovethe top of the wall also should be analyzed. Consideration must be given to whethermaterial in front of the wall that is assumed to provide passive resistance could beremoved or excavated in the future. In some cases, the retaining wall system may consistof tiebacks and soldier piles/drilled shafts.

Strengthened or Reinforced SoilThe strength characteristics of compacted fill can be improved by mixing the soil withcement or lime during compaction or by mechanically reinforcing the soil. In the case ofadmixture stabilization, testing is required to determine the type and amount of admixturenecessary to achieve the required strength. Soil with more than 50 percent fines (passingthe #200 sieve) is not well suited for mixing with cement. Moist fine-grained soil is oftensuitable (amenable to) for lime treatment.

Soil reinforcement is commonlyaccomplished with geosynthetics such aswoven geotextiles, geogrids, or steelstrips. The reinforcement should extendbeyond the failure surface that has aminimum factor of safety of 1.5 and theallowable seismic displacement.

DewateringThe presence of water in a slope can reduce the shear strength of the soil, reduce theshear resistance through buoyancy effects, and impose seepage forces. Those effectsreduce the factor of safety of the slope and can cause failure of the slope. Dewatering aslope (removing subsurface water) and/or providing drainage control to prevent futuresubsurface water build-up can increase the factor of safety. Both passive and activedewatering/subsurface-water-control systems can be used. Many dewatering systems


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require periodic maintenance to remain effective. In addition, monitoring programs maybe required to document or verify the effectiveness of the system.

Installing slightly inclined gravity dewatering wells into the slope can passively dewater aslope. Those "horizontal" drains (also known as hydraugers) should be sloped toward an

outlet and extended sufficiently into the slope to dewater the earth materials that affectthe stability of the slope. Vertical pumped-wells also can be utilized to lower subsurfacewater levels within a potentially unstable mass.

The effectiveness of dewatering wells is dependent on the permeability of the soil. Insome cases, the soil is not sufficiently permeable, or other conditions exist that precludeeffective dewatering of the slope.

ContainmentLoose materials, such as colluvium, slope wash, slide debris, and broken rock, on theslope that could pose a hazard can be collected by a containment structure capable ofholding the volume of material that is expected to fail and reach the containment deviceover a given period of time. The containment structure type, size, and configuration willdepend on the anticipated volume to be retained and the configuration of the site. Debrisbasins, graded berms, graded ditches, debris walls, and slough walls can be used. Insome cases, debris fences may be permitted, although those structures often fail uponhigh-velocity impact.

Access should be provided to debris containment devices for maintenance. The type ofaccess required is dependent on the anticipated volume of debris requiring removal.Wheelbarrow access will be sufficient in some cases, whereas heavy equipment accessmay be required in other areas.


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Open Debris Basins Closed Debris Basins

Source: D. VanDine 1996 Source: D. VanDine 1996

DeflectionWalls or berms that are constructed at an angle to the expected path of a debris flow canbe used to deflect and transport debris around a structure. The channel gradient behindthose walls or berms must be sufficient to cause the debris to flow rather than collect.Required channel gradients may range from 10 to 40 percent depending on the expectedviscosity of the debris and whether thechannel is earthen or paved. An area for debris collection should be provided at theterminus of the deflection device.

Deflection Berm Terminal Berms

Source: D. VanDine 1996 Source: D. VanDine 1996


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Divergent V Walls

Source: D. VanDine 1996

Slope Protection For Rock SlopesWoven wire mesh and wire mesh have been used to mitigate rock fall hazards. The meshis hung from anchors drilled into stable rock and is placed over the slope face to helpkeep dislodged rocks from bouncing as they fall. The bottom of the mesh is generally leftopen so that dislodged rocks do not accumulate behind the mesh and cause it to fail.Usually a ditch is provided at the toe of the slope to collect fallen rock. Wire meshsystems can contain large rocks (3 feet in diameter) traveling at fast speeds. It is alsopossible to hold rocks in position with cables, rock bolts, or gunite slope covering.

Resistant Structures

Structures can sometimes be designed to resist damage during the anticipated slopemovement. Examples of structural systems that can resist damage include matfoundations and very stiff, widely spaced piles.

Mat foundations are designed to resist or minimize deflection or distortion of thestructure resting on the mat as a result of permanent displacement of theunderlying ground. The mat foundation itself may move or settle differentially, butthe mat is sufficiently stiff to reduce bending in the structure to a tolerable level.Mat foundations can be particularly useful when compacted fill slopes areexpected to experience greater than 5 cm of seismic displacement in the area of ahabitable structure. It must be recognized, however, that permanent verticaldifferential settlement may be undesirable and reveling may be required after thedesign event.

Another instance where a building can be designed to resist damage to earthmovement involves structures built over landslides experiencing plastic flow.Landslides that do not move as a rigid block can be penetrated with a series ofwidely spaced stiff piles . These piles are designed to resist loading imposed bymaterial acting on some tributary area to the piles (generally wider than the pile).The remaining material is designed to flow between the piles. The access andutilities leading to the building must be designed assuming that the ground surfacewill move vertically and laterally relative to the structure.


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General Guidelines For High Risk Areas

Any building having high occupancy content must have an evacuation/contingencyplan.The Chief fire prevention unit must certify all buildings over two storeys.

As far as is possible electricity supply should be underground to minimize damageto infrastructure by wind.Development over a 100 lots should have an evacuation plan in place. A zonalcommittee should also be formed.Upon handing over all new units in a development, the developer must also behand over to homeowners, the relevant disaster related information. This can beobtained from the ODPEM.All agricultural, commercial and industrial units must have a contingency plan.Drills must be conducted at least once per year with significant input from theODPEM.Developments of 50 lots and under will require a hazard impact assessment to be

submitted with the development application.Documentation required for subdivision application

All Applications are received By NEPA and the Local Authority. They are thendisseminated to the various technical agencies for comments before a final decision ismade to approve or not approve a subdivision. The following information is relevant forprocessing application within the ODPEM.

a. Physio-graphic featuresTopography, contours, slope analysis report, geo-hazard assessment and featuressuch as lakes streams and ponds are all factors that can affect the development.Designs should be planned with these in mind.

b. Site location informationAccurate property boundaries

The Procedures :

The procedure followed by the ODPEM is shown in figure 1 overleaf. The size andnature of the proposed development is always taken into account, the history of disastersin the area and the history of the performance of other developments in the area. Thevulnerability of elements at risk to the hazards is also assessed and the potential fordisasters is also pointed out. The organizations comments on both small developments(those including 9 lots and under) and large developments 10 lots and over and to includeresort and large-scale subdivisions for housing 400 lots and over in some cases).

A site inspection is required for all subdivision applications that come to the organization.However, depending on the size of the lots for small subdivisions and their location andrequest for example titles a site investigation may not always be required.


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Figure: 1 SHOWING procedures for subdivision Approval /Refusal

ODPEM receivessubdivision FromNEPA /PC

Draftletter of receipt

Background research anddata gathering

Conduct site investigation

Architectural Research

Preparation of report

Comments for Approvalwith conditions

Subdivisionfully approved Comments for

Refusal

Follow up with NEPAagency

Note final commentsfor records

Recommendation forbest land use

Submit comments to NEPA/PC


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Figure3 Hazard Vulnerability Matrix for the Country

Hazard Probability Significance Frequency Vulnerableareas

PotentialEconomicimpact.

Bush, Wildfires andForest FiresCivildisturbances

Coastal oilSpillDisease andoutbreaks

DroughtFloodingHazardousmaterial SpillHurricanetropicalstormsInfrastructuredisruptionNuclear powerplantSinkhole andsubsidenceTerrorismSeverthunderstormTransportationincident


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SS iittee iinn vvee ss tt iigg aa tt iioo nn ss

The purpose of the site investigation is to supplement in house data on the area carriedout in the desk study as to the extent to which to area is vulnerable. The desk studyinvolves analysis of topographic maps of 12, 500 scale or greater and cross referencing

with aerial photographic interpretation to develop the hazard map for the area. The siteinvestigations take into account:- The type of application The kind of development Identification of potential hazards Assessing vulnerability Assessing vulnerability of surrounding areas Recommendations for mitigation measures

Applications reviewed by ODPEM include all sites located along river courses or withinthe floodplain of the river, on gully banks, on hillsides, at coastal areas or near to active

faults, or located in areas exposed to high winds like hilltops or plateau would requirespecial guidelines or standards before they are developed. These sites includeresidential, commercial, industrial, agricultural and institutional land uses. Reports onthese sites usually cover the following areas;

Identification of hazardThe likelihood of occurrence of that hazardLocation of community most vulnerable/second nearestThe impact of the hazard The hazard index for each hazardLoss reduction strategies for the hazards identified.

Assessing vulnerabilityThis is calculated by combining the probability of various hazards in each area and theamount of value of development in the area. An inventory of the costs of damage tocritical facilities. Public facilities and other land uses should also be assessed.

Recommendation for mitigation measuresThe appropriate mitigation measure should be implemented only after the necessaryhazard and engineering analyses have been carried out.

IIDDEENNTTIIFFYYIINNGG RR IISS KKSS

A prudent first step is to list geographic and climatic hazards and other risks thatcould jeopardize the structures. These might include the developmentssusceptibility to hurricanes, tornadoes, flash flooding, earthquakes, or forest fires,and even the possibility of unusual hazards such as volcanic eruptions.

Hazard maps should be used to identify risks and vulnerability. Man-made disasters such as fuel or water supply failures, chemical spills, arson,

bombing, or other such problems should be accounted for.


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Take note of the environmental risks in the surroundings. Chemical industries,shipping routes for hazardous materials, and adjacent construction projects allexpose a development to damage.

Any event that is a real possibility should be covered under an emergency plan. A risk-assessment checklist should be developed for internal members of buildings

that require fire protection systems, electrical systems, plumbing, andenvironmental systems. It is also important to determine the vulnerability of theobjects.

RR IISS KK RR EEDDUUCCTTIIOO NN

Once the hazards are specified, a program with concrete goals, identifiable resources,and a schedule of activities for eliminating as many risks as possible. Some of the areasfor risk reduction include:

Control settlement of marginal lands in plains, combined with fragile and insecure

living conditions, infrastructure and social services; Public education and training to reduce hazard levels due to severe processes of

environmental degradation owing to poor land use Strengthening capacities for disaster risk management in critical institutions. Reducing human vulnerability resulting from poverty and inequality Monitor Rapid population growth Develop elevation requirements Change zoning regulations and building codes Create a hazard disclosure requirement for real estate sale Prepare local environmental/hazard impact orders

microsoft word - guidelines for development in high risk areas 2

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