The sheet & rill erosion model is based upon RUSLE. RUSLE is an erosion model predicting longtime average annual loss resulting from raindrop splash and runoff from specific field slopes in specified cropping and management systems and from rangeland. However, it is currently considered to be the best sheet & rill technology suited for continuous simulation of watershed sediment yield. HUSLE is used to determine the delivery ratio for the sheet & rill erosion for each cell to its receiving reach. The delivery ratio for the individual particle-size classes is proportioned according to their respective fall velocities. The resulting sediment is called the sediment yield to the stream system.