Flood Hazard Mitigation

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Flood Hazard and MitigationFlood Hazard and Mitigation

zanur a man, Ph.D., PDFPh.D., PDFBangladesh Water Development Board,Bangladesh Water Development Board,

Ministry of Water ResourcesMinistry of Water Resources


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What is Flood?

Discharge exceeds the capacity of waterDischarge exceeds the capacity of waterbody, like a river,body, like a river, lakes,lakes, oror pondpond of water atof water at

or near the point where the rain fall andor near the point where the rain fall and

then proceeds to inundate the surroundingthen proceeds to inundate the surroundingareas to damage the life and socioareas to damage the life and socio

economic infrastructures is the flood.economic infrastructures is the flood.


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RAINFALLPOTENTIAL EVAPORATION

MODEL/EQUATION

PARAMETERS/ASSUMPTIONS

RUNOFF COMPONENTS

EVAPORATION

RECHARGE

Rainfall Runoff Model

Evapo-transpiration

Water Level

Run-Off

Iterception andSurface Retention


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Types of Flood

According to Duration of the TravelingAccording to Duration of the Traveling

Lon Time Travelin floodLon Time Travelin flood

Short Time Traveling floodShort Time Traveling flood


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Long Traveling floodLong Traveling flood

More travel time, Follows river systems, Events (Rainfall and

Snow melt) may be occurred outside the Flood area

Example:

1. Ganges carries water from Himalayan of Uttarakhand: Snow

melting and heavy rainfall in Himalayan will affect in Bihar and

then Bangladesh

2. Brahmaputra starts from Manosh Sarawar in Tibet and

passes through China, Arunachal, Assam and then

Bangladesh3. Bihar Arunachal Assam and Bangladesh are getting flooding

RIVER FLOODRIVER FLOOD

Continued


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More travel time, follows tide and current, events

(eartquake in the sea) may be outside the affectedarea

Exam le:

Long Traveling floodLong Traveling flood

Earthquake occurred in Sumatra, Indonesia. High sea wave

hits Sri Lanka.

TSUNAMI


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Indonesia


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Short Traveling FloodShort Traveling Flood

Less travel time, may not follow river, events (heavy

rainfall) may occurred within or nearby catchment

area)

Exam le: hill area ma e heav rainfall and heExam le: hill area ma e heav rainfall and he

runoff may affect the plain land immediately afterrunoff may affect the plain land immediately after

steep hilly terrain.steep hilly terrain.

FLASH FLOODSFLASH FLOODS

Continued


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Less travel time, not follow river, events (heavy

rainfall) may occurred in urban area

Example: Heavy rainfall starts in the paved areas,Example: Heavy rainfall starts in the paved areas,

when draina e ca aci failed hen beca se of overwhen draina e ca aci failed hen beca se of over

flow surface runoff occurred.flow surface runoff occurred.

URBAN FLOODURBAN FLOOD

Continued


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Very less travel time, may not follow river, events

(failure of water retention structures) are occurred

within or nearby affected area)

Exam le: Wa er re en ion s r c res o re ain wa erExam le: Wa er re en ion s r c res o re ain wa er

in a reservoir or in a water body may fail and createin a reservoir or in a water body may fail and create

catastrophic disaster in the downstream of thecatastrophic disaster in the downstream of the

structure or water bodystructure or water body

Dam Break Floods andDam Break Floods and

Glacier Lake Outburst Flood (GLOF)Glacier Lake Outburst Flood (GLOF)

Continued


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Short Traveling FloodShort Traveling FloodVery less travel time, may not follow tide and current,

events (eartquake or depression in the sea) are

occurred within or nearby affected area

Example: Earthquake in at Sumatra Indonesia andExample: Earthquake in at Sumatra Indonesia and

and affect the nearby coastal area.and affect the nearby coastal area.

Tsunami andTsunami and

Tidal storm floodsTidal storm floods


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According to location of the eventsAccording to location of the events

Tidal Storm Flood (Surge and Cyclone)Tidal Storm Flood (Surge and Cyclone) Coast AreasCoast Areas

Tsunami (Earthquake in the Sea)Tsunami (Earthquake in the Sea)-- IslandsIslandsand Coastand Coast

Types of Flood

Arroyos Flood (DAM Break andArroyos Flood (DAM Break and GlacierGlacierLake Outburst)Lake Outburst)-- Mountain AreasMountain Areas

River Flood ( Flood in the flood plain)River Flood ( Flood in the flood plain)

Plain LandPlain Land Rain fed flood (Rural and Urban area)Rain fed flood (Rural and Urban area)--

Urban AreaUrban Area

Flash FloodFlash Flood (Hilly areas)(Hilly areas)


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Flood HazardFlood hazard is the potential risk to life

from flooding.


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Types of Flood Hazard

Primary Hazard Direct Damage

n r H z r In ir D m

Tertiary Hazard Long Term Damage


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Primary HazardsPhysical damage

crops, roads and railways, bridges, transports, airport, houses, school, business centers, industries, sewer systems, canals, religious places, tourism,

forest, wildlife,

Continued


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Primary Hazards

Casualties

Human life and

Livestock.

Continued


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Primary Hazards

Health damages

epidemics and

waterborne diseases

Continued


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Primary Hazards

Displacement

sediments and rocks (some times suchlarge objects as automobiles),

houses and bridges.

Continued


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Primary Hazards

Soil Erosion

river bank,

levees and buildings


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Secondary Hazards

Disruption of services drinking water supplies and sewerage system

gas and electrical service.

Continued


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Secondary Hazards

Famine and disease transportation systems disrupted and crop

damages: resulting in shortages of food

,

Continued


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Secondary Hazards

Loss of institutional resources Institutional damages of school and colleges

Institutional and instrumental damage in hospital and

spensar es


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Tertiary HazardsEnvironmental effects

Shifting of the river channels

Coarse sand deposition on theagricultural land (non-productivity)

land (productivity).

Continued


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Tertiary HazardsLivelihood

Jobs may be lost due to the disruption ofservices, destruction of industries andbusiness etc.

Although jobs may be gained to helprebuild or repair flood damage

Continued


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Tertiary HazardsPrice escalation due increase of

taxes,

duties,

Continued


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Tertiary HazardsBiodiversity

Destruction of wildlife habitat

Fish migration


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Flood Hazard Mitigation

Flood hazard mitigation is the measures

against the floods to reduce the sufferings

and dama es of ro erties as well lives


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Types of Measuresfor mitigation

Structural measures

Non-structural measures


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Structural measures1. Protection of flood intrusion

embankment polder

barrage

regulator

sluice

Continued


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Structural measures2. Improvement of flood flow drainage

Dredging of channels River training

Flood risk mapping

Continued


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Structural measures3. Adaptation Mechanism

Constructing flood shelters, Raising home stead,

railway lines

Introducing flood proof agriculture

Continued


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Non Structural measures

1. Forecasting and early warning

Detection of onset Flood Development warning message

ssem na on o warn ng messageto the decision makers

Continued


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Flood Detection:Flood Detection:

Forecasting ModelsForecasting Models

Hydrologic Models

Simplified Models for rapid assessment

Less data requirement

Mostly aggregated parameters were used

Hydraulic Models

Complex Models for greater accuracy

Highly data demanding

Suitable for distributed watershed modeling

environment


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Hydrologic Processes in Flood ForecastingRainfall

Rainfall Excess

Interception

InfiltrationDepression Storage

Losses

Catchment Data

Overland flows

Channel flows

No FloodNo Yes

FloodingVulnerability

Analysis


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Flood Forecasting and Warning System

Indian Data

WMO

JRCWARPO

Radio

wir

Tele

River stage

Rainfall

R

e

a

l

T

i

m

e D a t a

Dissemination

to the public

InternetInternet

FFWC Radio Tower

FFWC Satellite dish

24, 48, 72 hr

forecasts

water level

flood extentmaps

thanainundation

maps

Telephone

Fax

Fax Modem

ModemTelevision

Bulletine

GIS data layers

less

communication

via modem

manual entry

etry

/Databox/Voice

SPARRSOSattelite images

BMD

Weather forecastSynoptic charts

Boundary estimation

Rainfal,Water level

Data Entry & Processing Modelling & Mapping

Dissemination

to various agencies


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Flood Warning Dissemination

Weekly Dry Season

Bulletin

Daily Flood Bulletin Annual Flood Report

pec a epor on y oo

Report

Mode of Dissemination

E-Mail

Fax Wireless Messenger

WWW


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2. Response to the flood

Preparedness for fighting Involvement of community

Relief distribution among the victims

Medical support

Rehabilitation of flood victims

Continued


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Protection of vital infrastructure


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Evacuated Flood Victims


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Flood victims for relief and rescue


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2. Flood Damage Assessment

Assessment of infrastructural loss

Mobilizing resources for

reconstruction and rehabilitation


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Flood Management Cycle

FloodEvent


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Vulnerability Analysis Spatial Extent of Flood Inundation

The spatial extent of the flood inundation is useful inidentifying the vulnerable regions

Useful for damage assessment and identification of

safe zones

Flow velocity A significant parameter during high flows in steep

slopes for risk assessment


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Thanks for your attention andfor further uer :

[email protected]

Flood Hazard Mitigation

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