Africa Soil Information Service (AfSIS): Topographic Wetness Index (TWI)

The Africa Soil Information Service (AfSIS): Topographic Wetness Index (TWI) is a 90m raster dataset showing zones of increased soil moisture where the landscape area contributing runoff is large and slopes are low. The topographic wetness index, originally developed by Beven and Kirkby in 1979, provides a measure of wetness conditions at the catchment scale. This dataset combines local upslope contributing area and slope using the digital elevation model AfHydSRTM, which is based on the CGIAR-SRTM 90m Version 4. The dataset was produced at the World Agroforestry Centre (ICRAF) in Nairobi, Kenya and is distributed by the Africa Soil Information Service. This index is commonly used in soil landscape modeling and in the analysis of vegetation patterns. The images and data are available from the Africa Soil Information Service (AfSIS) in Geographic Tagged Image File Format (GeoTIFF) format via download at http://africasoils.net/.