Tidal River Management in the Southwest Region of Bangladesh Using Mathematical Modelling

In the low-lying coastal areas of Bangladesh, a series of embankments, also known as polders, were built in the 1960s to protect these areas from tidal floods. However, these polders have adversely impacted social and coastal ecosystems by causing excessive siltation in rivers. To solve this problem, an initiative known as tidal river management (TRM) has been implemented since the 1990s. With this initiative, polder embankments are periodically cut in selected locations to allow the sediment-laden water to reach the polders, allowing sedimentation to occur. Subsequently, these cuts are closed. The authors assessed the suitability of the TRM initiative for the polder in East Beel Kuksia. The research was carried out using coupled 1D and 2D hydrodynamic models, built with the software tool MIKE11 and coupled with MIKE21. Erosion was calculated based on information on bed shear stress from the hydrodynamic model and erosional critical shear stress. With the implementation of TRM, the drainage capacity of the rivers downstream of the studied polder consequently increased.