Runoff response and sediment yield from urban road surfaces: an experimental study in semi-arid northern Ethiopia

This study investigated the effect of gravel and cobblestone road surfaces on runoff responses and sediment yield in semi-arid northern Ethiopia. A field experiment was set up with six treatments of gravel and cobblestone road surfaces at 1, 3 and 7% slope gradients. Cobblestone road surface produced significantly lower runoff than gravel. Slope gradient had a significant effect on the runoff amount from gravel and cobblestone road surfaces. Runoff reductions by cobblestone road surface compared to gravel at 1, 3 and 7% slopes were 27, 30 and 31%, respectively. Runoff coefficients for gravel road surface at 1, 3, and 7% slopes were 0.60, 0.65 and 0.68, respectively. Runoff coefficients for cobblestone at 1, 3 and 7% slopes were 0.41, 0.45 and 0.47, respectively. Slope gradient had a significant effect on sediment yield for a gravel road surface. Sediment yield from cobblestone, however, was insignificant compared to gravel.