Flood Hazard Mapping of Dhaka-narayanganj-demra (dnd) Project Using Geo-informatics Tools

Dhaka-Narayanganj-Demra (DND) Project is one of about 700 water sector projects built by Bangladesh Water Development Board (BWDB) in Bangladesh. It was a successful project from all considerations. But during 1998 flood, there was overtopping and breaching of embankment. At that time BWDB was able to stop much inundation by doing emergency work. Still many people are building their houses and factories in low-lying area. The study area is nearer to central Dhaka city. So urbanization is increasing rapidly. Again, due to global warming, intensity and magnitude of different disasters are increasing. That is why this project is chosen as study area to examine the inundation depth in overtopping occurrence and that result is used to prepare an informative Flood Hazard Map. A flood hazard map of DND Project was developed using the 1988 flood data. The inundation simulation was conducted using ArcGIS and HEC-RAS considering water level of 6.93 m at Shitalakhya river and that of 7.23 m at Buriganga river. The analysis shows that about 21 % of the total study area has been inundated by less than 1 m depth which is 45 % of the total inundated area. 15 % of the total study area has been inundated by 1 m to less than 2 m depth which is 32 % of the total inundated area. So in total 36 % of the total study area has been inundated by less than 2 m depth which is 77 % of the total inundated area. The maximum inundation depth has been found 6.67 m. This affected about 47 % of land of the study area and about 250,000 people. But the residents are not aware of it. The results obtained in this study would provide essential information for flood plain management aimed at containing flood damages in future. The way of dissemination of FHM has been done to raise public awareness.