EVALUATING OVERLAND-FLOW SEDIMENT TRANSPORT CAPACITY

An equation for evaluating the sediment transport capacity of overland flow is a necessary part of a physically based soil erosion model des cribing sediment detachment and transport as distributed processes. At first, for the hydraulic conditions of small-scale and large-scale ro ughness, the sediment transport capacity relationship used in the WEPP model is calibrated by Yalin and Govers' equation. The analysis shows that the transport coefficient K-t depends on the Shields parameter, Y, according to a semi-logarithmic (Yalin) or a linear (Govers) equati on. The reliability of the semi-logarithmic equation is verified by Sm art's, and Aziz and Scott's experimental data. Then the Low's formula, whose applicability is also proved by Smart's, and Aziz and Scott's d ata, is transformed as a stream power equation in which a stream power coefficient, K-SP, depending on Shields parameter, slope, sediment an d water-specific weight, appears. A relationship between transport cap acity and effective stream power is also proposed. Finally, the influe nce of rainfall on sediment transport capacity and the prediction of c ritical shear stress corresponding to overland flow are examined. (C) 1998 John Wiley & Sons, Ltd.