A Numerical Investigation into the Back Water Effect on Flood Water in the Meghna River in Bangladesh due to the South-west Monsoon Wind

Flood is a recurring and devastating phenomenon in Bangladesh. One of the important causes of devastating floods in Bangladesh is the ‘ back water effect ’ from the Bay of Bengal. A multilevel numerical model has been used to investigate the back water effect of the south-west (SW) monsoon wind prevailing over the Bay of Bengal on the discharge through the Meghna River in Bangladesh into the bay. Separate experiments were performed with (1) flood water discharge only, (2) SW monsoon wind only and (3) both flood water discharge and SW monsoon wind. The model demonstrates that a substantial amount of flood water is held up inside Bangladesh by the SW monsoon wind, but this is dependent on the relative strength of the wind and the discharge.