Description
The Topographic Wetness Index (TWI) estimates the tendency of water to pool based on a pixel’s slope and location within a hydrological catchment. These values were estimated for the four major villages and aggregated to the fokontany level.
Columns
comm_fkt
name of fokontany using standardized ‘new_commune’_’fokontany’ nomenclature
mean_twi
Average TWI value in a 1km buffer surrounding the four major villages in a fokontany. Calculated using a building-weighted mean.
Additional Info
✍️ Author
🔧 Maintainer
🗓 Last Updated
March 11, 2026
🔹 Data Link
Created as part of Evans et al. 2025 (doi: 10.1186/s12936-025-05266-0). Can be accessed via the associated figshare repository.
🔹 Processing Steps
The TWI is calculated based on the SRTM Digital Elevation model using the GRASS GIS function ‘topidx. It estimates TWI as ln(a/tan(β)), where a is the surface catchment area of that pixel and β is the local surface topographic slope. These values were then extracted using a spatial mean (weighted by included pixel area) around two zones of interest: within a 1-km radius of major villages and in rice paddy areas. These values were aggregated to the level of the fokontany via a building-weighted mean