Hydrological and erosion responses of steep spoil heaps to taproot and fibrous root grasses under simulated rainfalls

•Effects of taproot and fibrous root grasses on soil loss of spoil heaps were revealed.•The grasses reduced soil loss by 91.1% that was 2.2 times that of runoff.•Taproot grass was preferred to control soil erosion of spoil heaps.•Taproot grass with greater stems causes lower effective shear stress detaching soil.