Fluvial Geomorphology and Basin Development of Karra Khola Basin,Hetauda, Central Nepal

Abstract

Geomorphological study of a basin is important for understanding the overall basin characteristics which are helpful for the management of water resources, construction along the river bank and natural hazard mitigation within the area. The study was carried out in the Karra Khola Basin, one of the prominent basins in the Eastern extreme of the Hetauda Dun Valley, Central Nepal, to investigate geomorphic characteristics of the main stream of the basin, categorize them into various stream types and study basin development through drainage basin’s morphometric parameters. Geographical Information System (GIS) and Remote sensing techniques using satellite images were used as a tool to make the morphometric analysis of the basin along with its major 13 sub basins and delineate stream classification following the Rosgen’s Level I hierarchical inventory. The main stream of the Karra Khola is characterized as A-, B- and C-type and the tributaries segments as B- and F-type. The basin is structurally unaffected and has the permeable surface area and elongated shape. The hypsometric analysis indicates that the basin is mostly at the old stage of geomorphic development while four out of 13 sub basins being at mature stage. The Karra Khola sub basins have higher risk to flash flooding (Lg=0.1-0.16km). Drainage density value reveals that the basin is highly susceptible to flooding, gully erosion, etc. Similarly, dissection index value implies that the north eastern region of the basin is highly vulnerable to erosion as it at the younger stage of geomorphic development. Since the study area is highly sensitive to future natural hazards, further study and appropriate measures should be followed for safeguarding against the future risk along the Karra Khola basin and its tributaries.