Abstract:
The Erosivity Index (EI) and the Modified
Fournier Index (MFI) are two commonly used methods in
calculating the R factor of the universal soil loss equation/
revised universal soil loss equation formula. Using Mauritius
as a case study, the value of high-resolution data versus
long-term totals in erosivity calculations is investigated. A
limited number of four Mauritius Meteorological Services
stations located on the west coast and the Central Plateau
provided the study with detailed rainfall data for 6 years at
6-min intervals. Rainfall erosivity for erosive events was
calculated using different set interval data. In this study,
within the EI, the use of 6-min rainfall intervals during
erosive rainfall gave estimates of around 10% more erosivity
than the 30-min time intervals and 33% more rainfall erosivity
than the 60-min rainfall measurements. When the MFI
was used to determine erosivity through annual and monthly
rainfall totals, substantially higher erosivity than the EI
method was calculated in both regions. This stems from the
large amount of non-erosive rainfall that is generated on
Mauritius. Even when the MFI was used to calculate erosivity
through monthly and annual rainfall totals derived purely
from erosive rainfall, erosivity calculations were not comparable
to those from high-resolution data within the EI. We
suggest that for the computation of erosivity, rainfall data
with the highest possible resolution should be utilised if
available and that the application of annual and monthly
rainfall totals to assess absolute soil erosion risk within a
high rainfall tropical environment must be used with caution.
