The 18 August 2008 avulsion of the Kosi River draining the parts of north Bihar in eastern India may well be regarded as one of the greatest avulsions in a large river in recent years. The Kosi River shifted by ~120 km eastward, triggered by the breach of the eastern afflux bund at Kusaha in Nepal at a location 12 km upstream of the Kosi barrage. This event was widely perceived as a major flood in the media and scientific circles. Although a large area was indeed inundated after this event, it is important to appreciate that this inundation was different from a regular flooding event.

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The paper presents an account of the Kusaha breach of the Kosi river which has been widely perceived as a flood event in the media and scientific circles. It is true that a large area was inundated after this event but it is important to appreciate that this inundation was different from a regular flooding event. It is argued that this event marked a mega-avulsion of the Kosi river.

The recent Kosi floods have proved once again that inadequate control measures have been responsible for the recurring disasters. Typically flood control and riverine studies focus on hydrological information, whereas a much more integrated approach that pays attention to specific morphological factors is required.

The recent Kosi floods have proved once again that inadequate control measures have been responsible for the recurring disasters. Typically flood control and riverine studies focus on hydrological information, whereas a much more integrated approach that pays attention to specific morphological factors is required.

The rivers draining the Gangetic plains exhibit remarkable geomorphic diversity, and this has consequently characterized the rivers to be dominantly aggradational in the Eastern Gangetic Plains (EGP) and degradational in the Western Gangetic Plains. We suggest that steam power and sediment supply are the two main fluvial parameters which govern the aggradation or degradation in river systems which, in turn, are controlled by inherent catchment parameters such as rainfall and tectonics. The

Flood Hazard Mapping is a vital component for appropriate land use planning in flood-prone areas. It creates easily-read, rapidly-accessible charts and maps which facilitates the administrators and planners to identify areas of risk and prioritize their mitigation/ response efforts. This article presents an efficient methodology to accurately delineate the flood-hazard areas in the Kosi River Basin, North Bihar, India in a GIS environment.