The Water Erosion Prediction Project (WEPP) divides erosion on hillslopes into rill and interrill processes. Rill detachment happens when water flow is strong enough to move soil particles, while net deposition occurs when there is more sediment than the water can carry. To predict soil erosion, WEPP only needs information on runoff rate, duration, and rainfall intensity. The project uses specific equations to calculate erosion on hillslopes.