Abstract
Abstract. This study introduces a flood hazard assessment part of the global flood risk assessment (Part 2) conducted with a distributed hydrological Block-wise TOP (BTOP) model and a GIS-based Flood Inundation Depth (FID) model. In this study, the 20 km grid BTOP model was developed with globally available data on and applied for the Ganges, Brahmaputra and Meghna (GBM) river basin. The BTOP model was calibrated with observed river discharges in Bangladesh and was applied for climate change impact assessment to produce flood discharges at each BTOP cell under present and future climates. For Bangladesh, the cumulative flood inundation maps were produced using the FID model with the BTOP simulated flood discharges and allowed us to consider levee effectiveness for reduction of flood inundation. For the climate change impacts, the flood hazard increased both in flood discharge and inundation area for the 50- and 100-year floods. From these preliminary results, the proposed methodology can partly overcome the limitation of the data unavailability and produces flood~maps that can be used for the nationwide flood risk assessment, which is presented in Part 2 of this study.
Highlights
Bangladesh is flood prone and densely populated country that is located at the confluence of the Ganges, Brahmaputra and Meghna (GBM) rivers (FAO, 2012)
For the climate change impact assessment, the change of potential flood inundation depth between present and future climates is demonstrated to evaluate the effectiveness of existing river infrastructure in the future
The 0.45 km Flood Inundation Depth (FID) model was developed in the Bangladesh portion of the GBM basin to produce flood inundation maps using simulated river discharges with the 20 km Block-wise TOP (BTOP) model applied for the entire GBM basin
Summary
Bangladesh is flood prone and densely populated country that is located at the confluence of the Ganges, Brahmaputra and Meghna (GBM) rivers (FAO, 2012). In Bangladesh, the frequent floods cause fatalities and economic losses and are due to the combined influence of these rivers. Among these floods, the 1998 flood affected 53 out of 64 districts in Bangladesh and was considered the most devastating flood (BWDB, 2014). The 1998 flood affected 53 out of 64 districts in Bangladesh and was considered the most devastating flood (BWDB, 2014) Despite these frequent floods, embankments are only available means for the flood hazard reduction in Bangladesh while the forecasting of flood peaks in Bangladesh is complicated due to lack of hydrometeorological and water use data outside of Bangladesh. The existing levee infrastructure in Bangladesh needs to be considered with GBM flood flows in the flood hazard assessment to investigate its effectiveness due to climate change impacts
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