Assessment of flood hazard,vulnerability and risk of mid-eastern Dhaka using DEM and 1D hydrodynamic model |
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Authors: | Masood Muhammad Takeuchi Kuniyoshi |
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Institution: | (1) Design Circle–1, Bangladesh Water Development Board, 72, Green Road, Dhaka, 1215, Bangladesh;(2) International Centre for Water Hazard and Risk Management (ICHARM), PWRI, 1-6 Minamihara, Tsukuba, Ibaraki 305-8516, Japan |
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Abstract: | Floods are regular feature in rapidly urbanizing Dhaka, the capital city of Bangladesh. It is observed that about 60% of the
eastern Dhaka regularly goes under water every year in monsoon due to lack of flood protection. Experience gathered from past
devastating floods shows that, besides structural approach, non-structural approach such as flood hazard map and risk map
is effective tools for reducing flood damages. In this paper, assessment of flood hazard by developing a flood hazard map
for mid-eastern Dhaka (37.16 km2) was carried out by 1D hydrodynamic simulation on the basis of digital elevation model (DEM) data from Shuttle Radar Topography
Mission and the hydrologic field-observed data for 32 years (1972–2004). As the topography of the area has been considerably
changed due to rapid land-filling by land developers which was observed in recent satellite image (DigitalGlobe image; Date
of imagery: 7th March 2007), the acquired DEM data were modified to represent the current topography. The inundation simulation
was conducted using hydrodynamic program HEC-RAS for flood of 100-year return period. The simulation has revealed that the
maximum depth is 7.55 m at the southeastern part of that area and affected area is more than 50%. A flood hazard map was prepared
according to the simulation result using the software ArcGIS. Finally, to assess the flood risk of that area, a risk map was
prepared where risk was defined as the product of hazard (i.e., depth of inundation) and vulnerability (i.e., the exposure
of people or assets to flood). These two maps should be helpful in raising awareness of inhabitants and in assigning priority
for land development and for emergency preparedness including aid and relief operations in high-risk areas in the future. |
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