Assessing The Impact Of Watershed Development Programs On Soil Erosion And Biomass Production Using Remote Sensing And Gis The Case Of Yezat Watershed West Gojam Zone Of Amhara Region Ethiopia

Environmental problems are alarming all over the world. Land degradation, environmentalrnand social problems associated with its use, calls for adopting appropriate policy measuresrnand practical actions for the best land management practices. Integrated WatershedrnDevelopment Program (IWSDP) was implemented for reducing soil erosion, improvingrnwater resources and reestablishing vegetation under the Sustainable land management (SLM)rnprogram. Consequently, this study was conducted in Yezat watershed with the objective ofrndetermining the trends and changes of soil erosion, vegetation cover and land-use/landcover(rnLULC) that has changed during pre and post treatment periods (2001−2010 torn2010−2015) and evaluating the impact of watershed development program using remoternsensing and Geographical information system(GIS) approach. The study was carried out timernseries satellite imageries (Landsat ETM+ 2001, TM 2010, and OLI 2015) together with otherrnancillary data covering the watershed. The satellite image was classified into different landuse/rnland-cover categories using supervised classification by maximum likelihood algorithm.rnThey were also classified into different biomass levels using Normalized DifferencernVegetation Index (NDVI) analysis. Revised Universal Soil Loss Equation (RUSLE)rnmodeling is applied in a GIS environment to quantify the potential soil erosion risk. Thernmodeling is carried out for the years 2001, 2010, and 2015, and is based on Landsat satelliternimageries, rainfall, soil and DEM data. The results reveal significant modification andrnconversion of land-use/land-cover of the watershed. A significant portion of the watershedrnwas continuously under intensively grass land, wood land and homesteads. The area coveredrnwith grassland, woodland and homesteads were increased by 610.69 ha (4%), 101.69 harn(0.67%) and 126.6 ha (0.83%) while cultivated land and shrub/bush land where decreased byrn323.43(0.02%) and 515.44ha (3.41%), respectively during post treatment periodrn(2010−2015). The estimated woody biomass considerably decreased during the periodrn2001−2010 (pre treatment) while in 2010 −2015 (post treatment), significant increase in thernwoody biomass area was observed. Based on the result, vegetation cover was decreasedrnduring pre treatment periods (2001−2010) which account for 91.1% of the land area. Fromrn2010 −2015 (post-treatment) period, 88% of the land area was changed to increasing trend.rnThe increasing of NDVI indicates better ground cover vegetation condition. The resultrnderived from the estimated annual soil loss rate has shown the mean annual soil losses arern7.2 tons ha-1 yr-1 in 2001, 7.7 tons ha-1yr-1in 2010 and 4.8 tons ha-1yr-1in 2015. The studyrnfurther shows that IWSDP decreased soil erosion, reduced sedimentation and run off, andrnrehabilitation of degraded lands. This study reconfirms the importance of IWSDP as a key tornimprove the status and utilization of watershed resources in response to sustainable landrnmanagement interventions and sustainable livelihood. Thus, remotely sensed data usingrnadvanced techniques such as remote sensing and Geographic information system (GIS) canrnbe useful to guide decision making process in evaluating the impact of IWDP on trends ofrnsoil erosion and biomass production.rnKeywords: Biomass, watershed, GIS, NDVI, LULC, Remote Sensing, RUSLE, Soil erosion

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