CHARACTERISTICS OF MORPHOLOGICAL CHANGE RESULTING FROM TIDAL CURRENTS IN THE MEGHNA ESTUARY

抄録

 This study investigates the characteristics of suspended sediment transportation and associated morphological changes in the Meghna Estuary in Bangladesh, specifically focusing on sediment transport dynamics in the lower Meghna River and the sediment budget in the Noakhali islands area, which is located in the northeastern part of the Meghna Estuary. A depth-averaged 2-D model, spanning 350 km in length including the entire lower Meghna River and surrounding estuary area, is prepared for flow and sediment calculations, employing a uniform sediment size of 0.06 mm. The results of an entire year calculation, considering the wide seasonal variation, indicate that the Noakhali islands area experiences significant morphological changes during the ebb tide period of the spring tide time, particularly in the monsoon season. During this time, a strong current diverges from the main flow of the lower Meghna River, carrying a significant amount of suspended sediment, which leads to high sediment concentration particularly in the slack time, resulting in significant storage and deposition of fine sediment in this area. Therefore, this present study proposes a model which can evaluate the seasonal, daily, and hourly variation of sediment storage and deposition processes in an estuary dominated by fine sediment.