Science et changements planétaires / Sécheresse


Rainfall and water erosion monitoring in Burkina Faso. Using a cartographic model Volume 11, issue 3, Septembre 2000


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CIRAD TA 60/15, 34398 Montpellier Cedex 5, France.
  • Page(s) : 163-9
  • Published in: 2000

The proposed cartographic model provides decision-makers with a qualitative insight into soil erosion throughout Burkina Faso. Wischmeier’s formula parameters were used to select data and corresponding thematic maps. The basic map was drawn up on the basis of a soil map (erosion susceptibility), an administrative map (statistical data) and a land-use and occupation map (spatial data). These maps were digitized (vector mode) and then overlaid with Arc/Info software and some contours were simplified. The equiproblematic zone map comprises polygons that outline sectors with the same characteristics relative to farmland in Burkina Faso. The database takes into account that merging retains information from the basic maps (land use, soil erosion susceptibility). For rainfall severity, the polygons were informed directly. Human data give a temporal dimension to the model and only involve population and livestock density. A hierarchic classification is used for each parameter. Modelling is carried out in the attribute field. Wischmeier’s formula is not adapted to capped soils and was thus not used. Year 1985 was used to calibrate a simple additive formula after weighting the parameter values. The index relative to hydric erosion is thresholded according to classes. A soil degradation map of Burkina Faso was used for calibration purposes while taking our knowledge of this country into account. A simulation for 1995 was produced using statistics on population and livestock representing pressure. A new response parameter represented by the percentage of areas with anti-erosion ridges was introduced into the model. The new model must be calibrated and validated. This cartographic model mainly aims at supplying decision-makers with the qualitative status of water erosion on a map representing an entire country.