Landslide and Flashflood in Bangladesh

Abstract

Flashflood and associated landslide are become major disasters in the hilly regions of Bangladesh, occurring almost every year. Flashflood and landslide disasters are caused by a set of preliminary and triggering factors which determine their location, frequency and magnitude. Excessive rainfall in the piedmont area with a high intensity is the main source of flashflood in the hilly area and resultant landslide specifically in the areas composed of unconsolidated rocks. The annual rainfall ranges from 2,200 mm along the western boundary to 5,800 mm in the north-east corner and even higher in different catchments due to monsoon depression. Being the higher order basin of the three largest basins Brahmaputra, Ganges and Meghna all the water discharges through the three major rivers of the country. Due to the higher intensity of rainfall with a shorter period of time these channels could not manage to discharges this deluge amount of water to the downstream to Bay of Bengal resultant sudden flood and associated landslide. Apart from physiology, hydrology and climatology, the changes in the geomorphology in relation to land use changes as well as deforestation, hill cutting and unplanned infrastructural development influences flashflood and landslide disaster impact further. Among the hilly region part of the north-eastern, north–south and northern regions are susceptible to and facing these disaster almost each year. Lack of proper landuse planning, weak enforcement by the local authorities increases risks and progress vulnerability significantly. Although the authority has taken initiatives of integrated planning including structural and non-structural measure to mitigate the damages by the disasters, lack of capacity of forecasting appropriately does not provide with sufficient lead time to reduce damages of personal property and economic assets. Further initiatives requires for basin wide integrated water resources management, increasing water retention capacity, early warning, landuse zoning and public awareness for effective management of flashflood and landslide disasters. The main objective of this chapter is to identify mountain risks and vulnerability of Bangladesh due to flashflood and landslide hazard and their underlying causes and effects. This discussion will also provide with some recommendations and policy implication for effective adaptation and mitigation measures.