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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Short Traveling FloodShort Traveling Flood
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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Short Traveling FloodShort Traveling Flood
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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Non Structural measures
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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Non Structural measures
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 :