Impact of Coriolis Force on the Flow Field and Sedimentation in Ideally Shaped Tidal Basins

Tidal basins under the Tidal River Management projects in Bangladesh exhibit complex morphological patterns consisting of substantial spatial and temporal variability of sedimentation. Sedimentation in the tidal basin is controlled by various physical and hydraulic factors. Therefore, it is indispensable to understand the dominant factors behind these morphological patterns. Flow field and sedimentation pattern in Pakhimara Beel (tidal basin), located in southwestern Bangladesh, are being investigated under the present study. Large-length scales of the beel, shallow water depth, and low depth-averaged velocity created by the hydraulic gradient of sediment-laden flows lead to Rossby number (defined as Ro = U/fL) < 1, making the system susceptible to the effect of Coriolis force. This condition alters the flow field and, thereby, the sedimentation pattern. Four ideally shaped computation domains with varying depth, inlet channel location, and orientation have been investigated through the Delft3D model. The results indicate that, for all domains, the flow velocity is deflected towards the right in the northern hemisphere due to Coriolis effect. It is found that at large peripheral areas of the beel with substantially low flow velocity, the circulations are influenced by Coriolis force, and higher sediment deposition occurs for higher latitudes. The results imply that the deposition patterns in large tidal basins are significantly influenced by Coriolis effect.