Flood-Hazard Mapping In A Regional Scale – Way Forward To The Future Hazard Atlas In Bangladesh

Flood causes substantial economic loss and hindrance to development activities in many developing countries of the world. Bangladesh, a developing country in South-east Asia is ranked as the world’s ninth-most disaster-prone country by the World Risk Report, 2018 because of its high exposure to multiple hazards and less coping and adaptive capacities. The country is recurrently hit by flood hazard almost every year. Being a densely populated country with the fragile economic condition, Bangladesh urgently needs to focus on future flood-risk reduction with more effective measures in order to sustain the development milestone achieved till now. Flood hazard mapping, an initial phase of risk understanding (i.e., perception and knowledge), is often considered to be an indispensable component of flood-risk reduction strategies. In line with the contention, the present study aimed towards flood hazard mapping in Bangladesh where flood prone northeastern part of the country is taken as a case area. Multi-cri teria evaluation technique (MCE) for hazard mapping has been employed where elevation, slope, distance from river, land use and landcover (LULC), precipitation, flow length, and population density were taken as the causative factors. Each factor, as well as their subclasses, were assigned with pertinent weight values based on expert knowledge by analytical hierarchy process (AHP)and subsequently integrated into geographic information system (GIS) platform. According to the final flood-susceptibility map, ~4241 km2 (~ 20% of the total area) area is categorized as the highest flood potential zone which encompasses mostly the southern part of the study area, including Gazipur, Narsingdi, and Brahmanbaria districts. In contrast, low flood potential zone covers ~9362 Km2 (~43% of the total area) area covering the northwestern and southwestern parts (e.g., Mymensing and Tangail districts) of the study region. Besides, a considerable portion of the study region, mostly in the western part (e.g., Sunamganj and Kishoreganj districts) is categorized as moderate flood potential zone encompassing ~7823 km2 (~ 35% of the study area) area. Population density, distance to river and topographic characteristics are found as the most influencing factors for the mapping of flood-risk zones in the current study. This type of assessment in a regional scale may serve as a guide to the relevant stakeholders to formulate flood hazard atlas and minimize the adverse impact of the future flood in Bangladesh.