Abstract:
Raising of low lying land inside the beel and maintaining proper drainage capacity of river are the two main objectives of Tidal River Management (TRM) process. But it was observed that sedimentation inside the beels were not uniformly distributed in the previous and current TRM practices in Beel Kedaria and East Beel Khuksia due to technical and operational problems/limitations during TRM process. In 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 further sedimentation inside the wider area of beel.
In this study sediment management options for uniform sediment deposition in tidal basins have been identified in consideration of existing problems of current TRM practices through review of literature, related reports, studies and better sedimentation inside the beel. Three options for sediment management inside the tidal basins have been identified. In Option-1, existing khal is connected with the river by constructing one link canal and allowing sedimentation in the beel. In Option-2, beel is divided into three compartments by constructing embankment around the compartment and allowing sedimentation in the compartments one after another. In Option-3, embankments are constructed along both banks of the main khal through the beel and cutting the embankment part by part gradually from upstream to downstream. Technical feasibility of these options have been assessed by a cohesive sediment transport model using MIKE21 FM modelling system.
Deposition volume in Beel Baruna in Jessore district for the three options have been assessed. The total deposition volume after four years operation for Option-1, Option-2 and Option-3 are 2.28, 2.97 and 3.12 million m3, respectively, in the beel area. Provision of dredging or manual re-excavation has been considered for all of the three options. It has been found that the maximum sediment deposition occurs in Option-3 and the minimum sediment deposition occurs for Option-1. Level of deposition for different options have been analyzed and found that deposition is more uniform in Option-3. The total construction costs of four years operation for different options also have been estimated. The minimum cost is required for Option-3. From the study it has been found that Option-3 is prefered in the study area.
