KU Leuven Belgium1
Bangladesh is deltaic floodplains with an area of about 150000 sq km formed mainly by deposition of sediment loads of the three great rivers of the Himalaya: the Ganges, the Brahmaputra and the Meghna. These rivers drain a basin area of about 1.72 million square kilometers, of which only about 7% lies within Bangladesh. The economy of the country is essentially agrarian which in turn is critically dependent on water. Besides agriculture, water is also vital for other sectors such as domestic and municipal water supply, industry, fishery, forestry, navigation and above all for ecology and environment. Flood is the most common and recurrent disaster that affects the economy of Bangladesh. Major causes of flood is mostly associated with the low, flat topography of the country, simultaneous high monsoon rain and snow melt in the Himalayas and coastal cyclones. This paper reviews the flood and erosion problems of Bangladesh as well as well as their mitigation measures. Results of a pilot study on applicability of a new low cost method of river bank erosion controls tested on a medium sized river in Bangladesh are also presented in the paper.
Necessary data and literatures were obtained from various sources such as Bangladesh Water Development Board (BWDB), Water Resources Planning Organizations (WARPO), Bangladesh, Institute of Water Modelling (IWM), Bangladesh University of Engineering and Technology (BUET), Centre for Environmental and geographic Information Services (CEGIS) etc. A chronological review of flooding in Bangladesh was made from remote past to recent and flooding areas in different years were identified and compared to see the variations. It was identified that in Bangladesh erosion of river banks are directly related to flood magnitudes. High flood magnitudes is reflected to high bank erosion and higher displacement of population which in turn results in higher losses to life, livelihoods and economy of the country.
Flood management practices in Bangladesh for mitigating flood losses over the years are considered as management of water resources in Bangladesh and these have been reviewed. Performance of both structural and non-structural measures and been reviewed. It was found that for a country like Bangladesh structural measures alone is no more a viable option rather more emphasis should be given to non-structural measures which involves not only data of upstream gages beyond border but also peoples participation. Flood and water management strategy have been reviewed. It has been observed that the implementation of the plans into action is relatively very low mainly due to intervention of the influential people, complex and slow initiatives of concerned government official, inexperienced contractor and fund constraints.
A field level pilot study was also conducted to test the effectiveness of low cost bank protection materials on a medium sized river in Bangladesh. Necessary hydro-morphological data were collected from the pilot study to detail out the effectiveness of the bottom vanes made from locally available low cost materials in controlling erosion in a medium sized river in Bangladesh These data were compiled and results were analyzed and finally graphical presentation of the results were made using ARC-GIS. The pilot study were conducted for a whole hydrological cycle and relevant data such water levels, bottom bathymetry, flow velocity, sediment concentration etc were measured in the vicinity of the nine bottom vanes placed in the concave bank of the selected river. The result shows that the low cost method such as bottom vanes can be successfully applied for control of bank erosion of small to medium sized alluvial rivers in Bangladesh.