Changes in soil surface properties under simulated rainfall and the effect of surface roughness on runoff, infiltration and soil loss

•Soil surface roughness is an important factor in runoff and soil erosion.•Smooth surfaces became rougher due to dislocation of particles by raindrop impacts.•Surface roughness (oriented and random) degraded after the rainfall.•Random roughness produced the highest runoff and soil loss and lowest infiltration.•Oriented roughness across-slope does not always reduce runoff and soil loss.