Flood Risk Due to Heavy Rains and Rising Sea Levels in the Municipality of Maputo

Abstract

This article assesses flood risk due to heavy rains and sea level rise in the municipality of Maputo (Mozambique) (1.1 million inhabitants in 2007, 346 sq km). The risk assessment methodology took into consideration four factors (hazard, vulnerability, exposure, and adaptation) using the formula ${\text{R}} = {{\left( {{\text{H }} \times {\text{ V}} \times {\text{ E}}} \right)} \mathord{\left/ {\vphantom {{\left( {{\text{H }} \times {\text{ V}} \times {\text{ E}}} \right)} {\text{A}}}} \right. \kern-0pt} {\text{A}}}$, where R = risk, H = hazard, V = vulnerability, E = exposure, A = adaptation. The four factors are measured using different indicators (rainfall, return periods of heavy rains and extreme tides, nature of the soil, density and poverty of population, etc.). The study uses photo interpretation of high-resolution satellite images, population figures, and terrain data, analyzed through the use of open source GIS software and on-site information. Eleven flood prone areas are identified: eight threatened by heavy rains and three by sea level rise. According to these results, an estimated 7 % of the population of Maputo lives in areas (106 ha) where the flood risk is greater than 6 on a scale of 1–10.