Soil erosion risk mapping with new datasets: An improved identification and prioritisation of high erosion risk areas

The numerous estuarine, marshy and marine ecosystems along the coastline of Mauritius Island are potential sinks for sediment especially during intense rainfall events when delivery ratios are high at basin outlets. For sustainable environmental management, soil and water conservation measures are needed, as these will better protect the cultivated lands and aquatic ecosystems from the damages associated with excessive soil loss and sediment deposition. Conservation program usually requires focusing available resources on a limited number of priority action areas. Such areas typically have the highest erosion risk and are connected to aquatic ecosystems. An erosion risk mapping model has been applied in this work to find the priority action areas of Mauritius and new datasets representing rainfall erosivity and topographic factors were used compared to a previous application of the same model. Rainfall erosivity was mapped with Fournier Index instead of rainfall depth. The topographic effect was mapped using a function combining slope length and slope gradient (LS) and was based on the unit contributing area algorithm along with land parcels effect. These new datasets improved the erosion risk mapping and the identification and prioritisation of high erosion areas. The prioritisation was done at basin and subbasin scales and considered the location of wetlands. This enabled the identification of basins and subbasins with the greatest erosion risk and towards which conservation measures can be directed for protecting lands on-site and wetlands off-site from environmental damages.

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