Temporal sensitivity analysis of erosivity estimations in a high rainfall tropical island environment

摘要

The Erosivity Index (EI) and the ModifiedFournier Index (MFI) are two commonly used methods incalculating the R factor of the universal soil loss equation/revised universal soil loss equation formula. Using Mauritiusas a case study, the value of high-resolution data versuslong-term totals in erosivity calculations is investigated. Alimited number of four Mauritius Meteorological Servicesstations located on the west coast and the Central Plateauprovided the study with detailed rainfall data for 6 years at6-min intervals. Rainfall erosivity for erosive events wascalculated using different set interval data. In this study,within the EI, the use of 6-min rainfall intervals duringerosive rainfall gave estimates of around 10% more erosivitythan the 30-min time intervals and 33% more rainfall erosivitythan the 60-min rainfall measurements. When the MFIwas used to determine erosivity through annual and monthlyrainfall totals, substantially higher erosivity than the EImethod was calculated in both regions. This stems from thelarge amount of non-erosive rainfall that is generated onMauritius. Even when the MFI was used to calculate erosivitythrough monthly and annual rainfall totals derived purelyfrom erosive rainfall, erosivity calculations were not comparableto those from high-resolution data within the EI. Wesuggest that for the computation of erosivity, rainfall datawith the highest possible resolution should be utilised ifavailable and that the application of annual and monthlyrainfall totals to assess absolute soil erosion risk within ahigh rainfall tropical environment must be used with caution.