A proposed model to predict the development of level bench terraces from steep backslope terraces.

Abstract

A simple model has been proposed to predict changes in terrace conformation, during the development of level bench terraces from steep backslope terraces by natural processes of erosion and normal tillage practices. The model is based on the universal soil loss equation, and applies to closed system terraces where soil and runoff losses are largely prevented. An iterative procedure is used, to give the amounts of soil redistributed within the terrace, and the changes in width and gradient of the sloping part of the terrace, as a function of time. The percentage of terrace which becomes too shallow for crop growth is also given for different periods of time and different tolerable reductions in soil depth. Equations to predict the proportion of "shallow" terrace that develops when a level bench terrace has been formed, and hence the optimum terrace width have also been formulated. These equations are based solely on simple geometrical considerations and should have general application.