| Abstract: | The catchments in the western Rift Valley escarpment of northern Ethiopia are highly responsive in terms of hydro‐geomorphic changes. With deforestation, dense gully and scar networks had developed by the 1980s on the escarpment between the towns of Alamata and Korem, transporting huge amounts of runoff and sediment down to the fertile and densely populated Raya Valley. To reverse this problem, catchment‐scale rehabilitation activities were initiated in the mid‐1980s. In this study, we examine the major hydro‐geomorphic response of streams after catchment rehabilitation. Scar networks in 20 adjacent catchments were mapped on Google Earth imagery of 2005, and their density was explained in terms of its corresponding Normalized Difference Vegetation Index and slope gradient. Soil and water conservation measures and vegetation recovery have reduced discharge and sediment flow which in turn resulted in various hydro‐geomorphic changes. In a multiple regression analysis, scar density was negatively related with Normalized Difference Vegetation Index and positively with average gradient of very steep slopes (r2 = 0·53, p < 0·01, n = 20). The size and amount of sediment supply to streams decreased, and various channel adjustments occurred. Notably, previously braided streams have changed to single thread streams, lateral bars have been stabilized and stream channels are narrowing and incising. Copyright © 2013 John Wiley & Sons, Ltd. |
