Intra-event characteristics of extreme erosive rainfall on Mauritius

Mauritius is a volcanic island with a raised interior where extreme rainfall events dominate rainfall erosivity. Intra-event characteristics of the 120 highest erosive events at six selected locations between 2004 and 2008 were analyzed to provide the first detailed intra-storm data for a tropical island environment. On Mauritius, spatial variation is evident in the characteristics of extreme erosive rainfall recorded at the stations, with a noticeable increase in rainfall depth, duration, kinetic energy, and erosivity of extreme events with altitude. Extreme events in the raised interior (central plateau) show high variability of peak intensity over time as well as a higher percentage of events in which the greatest intensity occurs in the latter part of the event. Intra-event distribution of rainfall in the interior of the island shows that rainfall there has a higher potential to exceed infiltration rates as well as the ability to generate high peak runoff rates and cause substantial soil loss. The study suggests that even though within-event rainfall characteristics are complex, they have implications for soil erosion risk, and that, in tropical island environments, the within-storm distribution of rainfall should be incorporated in soil-loss modeling.