A Water Accumulation Flooding Potentiality Index (WAFPI) for rating the risk of flooding– A case study of Mauritius Island

Abstract

The Water Accumulation Flooding Potentiality Index (WAFPI) is a qualitative risk assessment method based on a factorial scoring system that is aimed at dividing the land into classes that are similar in their susceptibility to flooding due to accumulating water. Such an assessment precedes quantitative flood modeling work, the overall results that are used for planning flood mitigation measures. WAFPI takes the form of an equation with five parameters as input, namely, rainfall amount; topographic slope angle; permeability of geology strata; soil infiltration capacity & land cover imperviousness. The output is a map with indices ranging from 1 to 10, with 1 being the lowest risk and 10 the highest risk of flooding. The assessment has been carried for Mauritius for the rainiest month of February. Results show that the assessment method succeeds in qualitatively evaluating the geospatial potentiality and the geospatial distribution of flooding due to water accumulation.

Keywords: flooding, risk assessment, potentiality mapping, GIS, factorial scoring, Mauritius.