Abstract
Flooding is a common feature on lower alluvial plains due to their structure in landform as flood plains. Careful analysis on repeated floods and cautious classification in geomorphology enable foretelling of potential flooding zone with improved accuracy. For identifying vulnerable zones against floods in the Shonai river basin, we draw a geomorphologic land classification map utilizing aerial photographs taken in 1974 and topographical maps published by GSI. Also, with a purpose of improving accuracy in the classifications of micro landforms, we conducted several field investigations to survey field surfaces. We evaluated flood risks on land use and land cover changes occurred in the last 40 years, comparing them with flooding area and long inundation zone on each fluvial landforms in the study area,. The lower river basin is mainly composed of natural levee, back marsh, valley plain, conspicuous meandering scroll with abandoned channels. Recent settlements onto the lower and middle basin are continuously marching regardless of flooding and inundation risks. The geomorphologic land classification map we draw shows flood inundated areas, which enables more effective for flood monitoring and mitigation. It can be useful in flood damage evaluation and also assessment the future risk as well.
