Dynamic Geomorphology of the Kosi Fan in Consequence to a Mega- Avulsion Aided by Space Inputs and Hydraulic Modeling

摘要

Several geomorphic processes are occurring on our planet, so it is always need to understand the geomorphic changes and evaluate the land form dynamics. The geomorphic evolution of any area can be obtained by detailed land form mapping. In the present study, an area in the parts of the Kosi basin has been selected for the study mainly using remote sensing data. Various fluvial land forms mapped and changes in course of the river have been evaluated. Digital enhancements of Landsat ETM*, IRS LISS-IV and Cartosat-1 are found to be quite useful in identification and mapping of fluvial features. The present study demonstrate the utility of remote sensing in examine the geomorphic evolution of the area. Geomorphic elements such as active channels, avulsion channel, water logged areas, sand bars, meander scar, minor active channels, paleo channels, dry channels etc., were mapped and combined all elements mega geomorphic units prepared such as hard rock terrain, piedmont zone, inactive flood plain, active flood plain, channel belt, minor active channel and its flood plain, fan surface and avulsion belt. Comparative study carried out for landscape as well as geomorphic evolution between prior to avulsion and post avulsion after the mega event (2008 flood). Remote sensing based geomorphic mapping of the parts of the Kosi basin for the pre and post- to avulsion images have brought interesting changes in the regional landscape in consequence of a large avulsion which occurred on August 18th, 2008. Major changes occurred in the main channel as well as outer channel. It has been estimated that approximately 511 sq km of agricultural land got converted into sandy areas (moist) making them barren for few years.