Design of rock protection to prevent erosion by water flows down steep slopes

Conventional stability analysis methods for determining rock armor size to protect steep (tan theta > 0.1) embankments from erosion due to downslope flow do not predict the correct dependency of armor size on the slope. Consequently, such methods become very conservative (discharge factor of safety similar to 8) at high slopes. We review published large-scale measurements recorded in the literature and show that adequate representation of flow aeration is important as proposed by Hartung and Scheuerlein in 1970. However, the assembled measurements show that the Hartung and Scheuerlein design method is not conservative. The aerated flow equations of Hartung and Scheuerlein, when combined with a correctly formulated stability equation, yield good collapse of the available large-scale data and a conservative design method.