AN ENGINEERING GEOLOGICAL ANATOMY OF THE PADMA RIVER BANK FAILURE AND EROSION, 2018: A CASE STUDY OF NARIA BANK SECTION, BANGLADESH
A unique erosion phenomenon prevailing in this part of Bengal delta prompted this study. During Aug-Sept, 2018 a sudden complex attenuation of current, wave and vortex in the Padma water flow caused an extraordinary disaster and made more than 5000 people homeless overnight by devouring away houses including concrete buildings, factories and markets. It is observed that geologically the Padma River remained confined within a width of 5 miles striking NW-SW trend following the margins of older alluvium and Faridpur Trough. The river tends to a meandering pattern consisting of deep vertical trenches along the Naria curvature. The deep trenches form along right bank and render the ground increasingly more vulnerable to subaqueous slope failure due to presence of thick (~200 ft.) alternating cross-bedded silt and micaceous fine sand of very high dilatancy and low angle of friction.
The present study identifies some application of technological advancement for developing real-time engineering geological mapping systems for monitoring and managing complex river bank erosion. Large scale 3D engineering geological map coupled with air-borne photogrammetric and radar inferrometry methods can be applied for real-time monitoring and prediction of differential settlements, subaqueous failures and ground movement. The point cloud maps developed using data from these systems can refine engineering geological maps for decision makers and improve the design of protective measures and sustainable engineering structures.