On the controls of fluvial hazards in the north Bihar plains, eastern India

Abstract

The rivers of the north Bihar plains, eastern India, pose three major fluvial hazards: rapid lateral migration, frequent flooding and extensive bank erosion. Lateral shifting of the Kosi, Gandak and several other rivers in the area has been attributed mainly to neotectonic tilting and subsidence of the area, and to some extent, local topography and sedimentological readjustments in the basin. Overbank flooding is a perennial problem, with most of the rivers of the north Bihar plains causing enormous damage to life and property. The construction of embankments along major portions of the rivers is only a short-term solution to mitigate floods not only because of frequent breaches in the embankment due to extremely high discharges during high flows but also because of the fact that these rivers carry a high sediment load causing rapid siltation and thereby raising the water level in a few years’ time. Severe bank erosion takes place during the lateral shifting of rivers as well as during high flows. Efforts to prevent these fluvial hazards in the area have largely failed as the geological and geomorphological considerations have not been taken into account.