Rainfall–runoff modelling of railway embankment steep slopes

A distributed 1D rainfall–runoff model is presented. It consists of the Saint Venant continuity andmomentum equations for overland flow and a modified Green-Ampt model for the infiltration on railway embankmentsteep slopes. The model is applied to adjacent 10-m-wide erosion control experimental plots with differentpercentages of grass cover. A relationship between the 2-day antecedent rainfall and initial moisture content wasestablished and used to predict the saturated hydraulic conductivity (Ks). Average values of Ks for 0, 50 and 100%grass cover were found to be 0.1, 1.19 and 2.56 mm/h, respectively. For the majority of cases, the model simulatedrunoff with acceptable accuracy, 68% having Nash-Sutcliffe efficiency (NSE) values above 0.50. The averageNSE value varied between 0.60 and 0.80, with 0% grass-covered plots yielding the highest values. As expected,the runoff volume decreased with increasing percentage of grass cover.