MODEL TO DESIGN LEVEL TERRACES

A procedure was developed to determine the maximum surface runoff volume (MSR) employing the constant rate of infiltration after prolonged wetting of the soil (fc). This procedure can also be employed to determine a factor (H), which, associated with the land topography and the soil conservation system characteristics, is used to calculate the depth of the stored water in level terrace channels. This procedure is applicable to places where the rainfall intensity-duration-frequency relationship is known. Hence, it has been applied to the typical conditions of Cascavel, state of Parana, Brazil. Graphs and equations relating the MSR and the H factor with the fc are presented. The calculated values using this procedure were compared with those obtained by the U.S. Soil Conservation Service—USDA curve number method. The effects of fc and of the return period on MSR values were analyzed.