Assessment of Flood Risk in Dire Dawa Town, Eastern Ethiopia, Using Gis
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Date
2007-03
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Addis Ababa Universty
Abstract
Flooding in any circumstance causes major stresses on the economic, social and
environmental regimes of the affected area. The flooding of 5/6 August 2006, however,
demonstrated that structural measures undertaken so far are not adequate to withstand
flood threats resulting in over 300 fatalities and significant damage to the flood defenses,
public infrastructure, housing and livelihoods in Dire Dawa town.
This paper studied flood risk analysis of Dire Dawa town and flash flood hazard mapping
of Dechatu catchment. To do this an original GIS-based approach was used to build
geodatabase for the selected flood hazard layers and elements at risk (land use and
population density).Then the important factors were developed to a uniform raster layers
with 28.5 m pixel and were masked by the town area in the catchment. Each factor was
standardized and then a pair wise comparison method was used to determine the factor
weights. Then weighted overlay analysis in multi criteria evaluation (MCE) was used to
carry out flood hazard and risk analysis.
DEM and mean annual daily maximum rainfall data were used to make flash flood
hazard mapping using hydro extension version 1.1 in Arc View 3.2 for Dechatu
catchment. Sink filled DEM was used to compute flow direction, flow accumulation,
watershed, mean slope, shape factor, and mean precipitation from raster layer generated
from mean annual daily maximum rainfall. All these parameters were entered into stream
attribute table for characterization. Eight Pour points were computed from the delineated
watershed of Dechatu catchment. Accordingly, Lege Dole, Lege Dechatu, Lege Gogeti
and Lege Ala were the flash flood hazard wadis in the catchment.
The major findings of the paper showed that most of the land use types in the town are
within low to moderate flood hazard and flood risk level. With these Dire Dawa town
flood risk map and flash flood hazard map, Development of future land use in
development policy should be done to decrease the hazard of flooding in Dire Dawa
town.
Key words: - Flood, Risk, Hazard, GIS, MCE, Dire Dawa, Dechatu
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Keywords
Flood, Risk, Hazard, GIS, MCE, Dire Dawa, Dechatu