MANAGING THE SEDIMENT LOAD IN TIDAL RIVER MANAGEMENT (TRM)

Abstract

Bangladesh has a large number of tidal rivers in the South-West region which are characterized by erosion and sedimentation and all of them discharges into the Bay of Bengal. Tidal River Management (TRM) which is a concept based on indigenous knowledge and sediment management practice is one of the key factors for river basin management in this region. Raising of low lying land inside the beel (depressed area) and maintaining proper drainage capacity of the rivers are the two main objectives of Tidal River Management (TRM) process. It was observed in the previous TRM practices in Beel Kedaria and East Beel Khuksia of South-West regionthat the sedimentation inside the beels were not uniform due to technical and operational problems inthe TRM process. The present practice of TRM operation, a link canal is constructed to connect the beel with the river. This results in sediment deposition at the mouth of the link canal, preventing uniform sedimentation inside the wider area of beel. Technical feasibility of this option has been assessed in this paperby a cohesive sediment transport model namely MIKE21 FM.The option which has been selected for sediment management inside the beel during TRM operation is such that one link has been constructed to connect the beel with the river. Deposition volume in Beel Baruna in Jessore district has been assessed. From the simulation results, it has been found that sedimentation inside the beel is not uniform with the present TRM practice. The deposition volume shows linear variation from 0.68Mm3 to 2.28Mm3 through the four consecutive years but the deposition pattern within the beel is non-uniform. The sediment deposition continues to increase even after four years in all areas. So it is necessary to implementa better functional technique for uniform and effective sedimentation inside the beel areas to overcome the long term drainage congestion and water logging problem from the study.