| Popis: |
Extreme rainfall in the Arunachal Himalaya has the potential to create floods in the downstream regions of Assam, with the rivers in the region exceeding their capacity and competence. High-intensity rainfall also leads to higher sediment generation in the sub- Himalayan catchment. Though floods have been incurring huge losses to both life and property frequently in Assam, there are only a few studies on the meteorological and orographic dynamics of such extreme rainfall events and their potential to create a flood. The present study highlights the pre-flood and post-flood scenario in the Lower Subansiri Basin (LSB) in Brahmaputra valley, Assam, through satellite data analysis and ground field surveys to establish linkages between extreme rainfall events and a subsequent major flood event that occurred during September 2012. We observed that the flood was mostly triggered by the extreme rainfall induced by orographic lifting of moisture-laden winds from the south. In addition to submerging an area of ~1900 km2, the flood also brought along fragile Neogene clastics that increased barren soil over the floodplains by ~47% compared to the pre-flood period, thus disrupting the agrarian economy of the region for several cropping seasons. These findings demonstrate the need for a reliable meteorological forecast for extreme rainfall as a prerequisite for developing effective flood-forecasting models in the Brahmaputra valley, which will positively contribute towards flood hazard management in the region. |
