PRELIMINARY ASSESSMENT OF RIVERBANK EROSION HAZARDS IN THE MEKONG DELTA, VIETNAM: INSIGHTS FROM ACTIVE TECTONICS, SUBSURFACE GEOPHYSICS, AND SELF-ORGANIZING MAPS

This study employs self-organizing maps (SOMs) in conjunction with geophysical, geological, and hydrogeological approaches to identify feature factors associated with erosion phenomena along the Tien and Hau rivers in Vietnam, encompassing 255 recorded sites. The SOM categorized the erosion sites into: Group 1 (21.6% of sites), with the distance of riverbank erosion sites to existing buildings being the smallest and the length of these sites and the distance to faults being the highest; Group 2 (20.4%) exhibits characteristics, such as the length of erosion sites, the distance to faults, local bank slopes, and the distance to the roads are lower values compared to Group 1, but a higher distance to existing buildings; the distance to faults, length of erosion sites in Group 3 (34.5%) are lower than those in Groups 1 and 2; Group 4 (23.5%) has the highest values for the distance to the roads and distance to existing buildings, but the lowest values for the length of erosion, riverbank slope, and distance to faults. The unusual changes in the anomaly characteristics of radon radioactive gas and mercury vapor concentrations showed the presence of active faults. Riverbank material, stratigraphy, and groundwater flow direction also influence this hazard. The findings can help mitigate the risk of riverbank erosion and reduce the socio-economic consequences in the affected area.