Study to Find Remedial Measures to Overcome Water Logging Problem in the Noakhali Area of Bangladesh

The drainage congestion in the Noakhali area is a long-standing and complicated issue. It is seen that large-scale siltation in the drainage channels due to reduction in tidal prism arising out of and subsequent manmade interventions (Crossdam I and II) are the causes behind such development. Due to manmade interventions in the past the south of the area has undergone major morphological changes resulting in channel and bay siltation. Thus new land formations have developed with the constriction and closure of major drainage routes. Some 200,000 hectare remains water logged for more than half of the year. This has led to severe environmental hazards in the area. Study has been undertaken to use mathematical modelling technique to analyze the complex problem and obtain a comprehensive solution. A 1-Dimensional sub-model for the area has been set up from the existing South East Regional Model of Bangladesh. The calibrated sub-model has been used to study various options of channel improvement and structural measures at the outfall channels. Later GIS flood depth maps have been produced to show the amount of improvement obtained in the various options. It has been observed that by controlling the outfalls of the rivers it has been possible to reduce siltation and flooding inside the area, but the major problem still remained outside the river outfalls where the discharge from the rivers and the tidal currents of the sea play a significant role in inducing the sedimentation process.