Gis And Remote Sensing Based Assessment Of Causes And Risk Analysis Of Flood Hazard In Iresha Watershed Meskan Wereda Snnpr Ethiopia

Flood hazard and water erosion are key environmental problems in degradedrnwatersheds. This study was conducted in Iresha watershed in Guraghe zone where therernis high incidences of floods and upland degradation. The objectives of this study are tornexamine LULC change and dynamics in the last three decades, to assess the retrospectivernand prospective state of soil erosion in the watershed, to analyze flood discharge andrnfuture flood risk potentials, to examine local land management practices and to suggestrnappropriate management interventions for the watershed. LULC change and dynamicsrnanalysis was conducted with RS and GIS. Soil loss was analyzed using RUSLE modelrnwith GIS and RS and also GIS and RS based analysis of runoff was determined withrncook’s method and management practices of the watershed is assessed using interviews ofrnlocal farmers, NGOs and government workers. The results show that Iresha watershed isrnexperiencing high LULC change and dynamics on cultivated lands, Enset, Erica bushrnland and natural vegetation with Eucalyptus and Cupressus. By now the watershed isrndominantly covered by cultivated land (26%) followed by natural vegetation with denserngrass (23%). In the watershed the most changed land cover is Erica bush land withrnsparse trees and it is changing 26 ha yr-1. The soil loss from the watershed is increasingrnover years and cultivated lands generate more soil (17.35 tha-1yr-1) that was beyond therntolerable limit for the area with the same agro-ecological setup and also for Africa andrnfor global average. Sub-watersheds on the upper part of the study watershed (32.4%) arerngenerating more soil with high future potentials. Runoff discharge was increasingrnannually and sub-watersheds in the upper slopes generates more runoff while subwatershedsrnin the lower slopes are generating less runoff which was calibrated byrnrecorded discharge values at the out let of the river by MoWR that ranges from 95m3s-1 torn305m3s-1. Maximum soil and runoff is generated from cultivated lands and the maximumrnrunoff and soil generating capacity is shifting upwards and more soil and runoff isrngenerated from the upper slopes due to the encroachment of cultivated lands to thernnatural forests and Erica bush lands, free grazing in the natural forests and Erica bushrnlands and lack of proper focus on natural resources management. Finally the cause forrnflood hazard in Iresha watershed is identified and to protect those causes of flood thernpossible corrective measures are planned.rnKey words:- Runoff discharge, Flood risk assessment & mapping, soil loss, soil erosion riskrnmapping, LULC Change detection, LULC dynamics analysis, GIS & RS, flood plain, floodrnhazard zone, RUSLE, Cook’s method, Catchment Characteristics, etc

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