Author(s): Fahima Shahadat; Mustafa Ataus Samad; Jalaluddin M. Abdul Hye
Linked Author(s):
Keywords: Global climate change; Sea level rise; Increased flooding; River morphology
Abstract: Bangladesh is located in one of the largest delta in the world comprising three great rivers in the region, the Ganges, the Brahmaputra and the Meghna. The low-lying topography and funnel shaped coast make the country exposed to recurrent riverine and coastal flooding. The severity of these floods increase while the peaks in the three major river basins occurs simultaneously. The passage of floodwater is also hindered by the presence of a spring tide situation at the Bay of Bengal. On the other hand, Bangladesh is also widely known as one of the most vulnerable countries to global climate change. In the present paper the effect of increased flooding due to global climate change and simultaneous occurrence of several natural events has been analyzed for a catchment in the northwest part of the country located adjacent to the left bank of the river Ganges. Corresponding morphological development in the riverbed of Ganges has been also considered in the study. It is to be noted that the study area was not flooded during 1988 and 1998 floods, the two recent severe most floods in Bangladesh that flooded 60% and 70% of the country respectively. Flooding behavior in the catchment for different combination of natural events and its impact on river morphology have been obtained through numerical simulations where MIKE11 and MIKE21C software of Danish Hydraulic Institute have been used. The simulation results show that the catchment would be inundated with a depth of about 1.5 m when increased flooding and sea level rise due to global climate change is considered along with simultaneous occurrence of flood peaks and spring tide condition at the bay. The flood height would remain above a critical level, 15.5m from mean sea level, for 12 days corresponding to an annual hydrograph distribution similar to that of 1988. This also indicates that apart from losing land as a result of sea level rise, increased monsoon flooding would also inundate high lands of the country at present considered as flood free. Morphological analysis shows that the main channel of Ganges shifts from right bank towards the left bank near the study area due to the global climate change.
Year: 2002