Water Erosion Prediction Project (WEPP)

Purpose:	Process-based hill slope continuous erosion model
Developer:	United States Department of Agriculture, Agriculture Research Center (USDA ARS)
Key Features:	Processed based erosion; ArcGIS interface
Latest Release:	Version 2012.8, 2012
OS Platform:	Windows
Cost:	Free
Related Software:	Eurosem, AnnAGNPS
Website:	WEPP home page

Introduction

The WEPP erosion model, first released in 1995, is a process-based, distributed parameter, continuous simulation, erosion prediction model that computes soil loss along a slope and sediment yield at the end of the hillslope for small watersheds. The WEPP models erosion as mix of the different erosion processes (rill and inter rill) occurring in the study area. After the peak runoff rate and runoff duration have been estimated from overland flow routing, steady state conditions are assumed and the peak runoff rate is used for erosion calculations. Erosion equations are then normalized for peak flow and shear stress at the end of the uniform slope. The model has been used to estimate the amount of erosion from farmlands or hill slopes for small watersheds, and results can inform soil and water conservation management options for agricultural, rangeland and forest areas

Key features of the WEPP model include its use of physics-based formulas, and the estimation of the amount of erosion. The model also benefits from an ArcGIS extension (GeoWEPP) developed by the University of Buffalo.

Advantages and Limitations

Advantages	Limitations
An ArcGIS extension (GeoWEPP) is available The model has performed well under disturbed forest and roads Can be used on an event basis Model is used extensively around the world	Model code not available Approximately 400 variables are needed to parameterize a run in WEPP WEPP over-predicts sediment load at the outlet resulting from its rudimentary sediment routing mechanism based on empirical parameters. The physical characteristics that affect routing are subtle and may not improve with a high quality DEM Model lacks a robust mechanism to account for in-channel and floodplain storage Model under predicts soil loss over a 30% slope for inter rill erosion (Grosh)
Illustrative Screens

Sample Applications

Africa	East Asia and the Pacific	Europe & Central Asia	Latin America & the Caribbean	Middle East and North Africa	South Asia