Results and interpretation of soil loss measurements from steep slopes in the Philippines

Abstract

Measurements of runoff-event soil loss and one-minute rates of rainfall and runoff are reported for runoff plots installed on the tropical Philippine island of Leyte. Plots were either under traditional crops cultivated using farmer practices, or kept bare. Plots were of length 12 m and at slopes of 50% to 70%. Soil loss for the cultivated crop was 35 t ha-1 y-1, and 63 t ha-1 y-1 for the bare soil plots. An erodibility parameter ߠcalculated for bare-plot data exceeded the value 1 for lower stream power events, indicating enhancement of flow-driven erosion by other processes, such as rainfall impact. This conclusion held whether an original erosion model was employed, or a subsequent model development designed to acknowledge the special effects of very high sediment concentrations and shallow flows common at the site.