Comparative Impact Analysis of Cyclone Ana in the Mozambique Channel Using Satellite Data

Abstract

There is still insufficient information available for a streamlined impact assessment of tropical cyclones on coastal habitats, particularly in the Mozambique Channel. Using Sentinel-1 and Sentinel-2 data, along with socio-ecological parameters including mangrove forest health and population density, we modeled the extent of flooding and its impact following the ‘severe tropical storm’ Ana which occurred between the 20 January until 25 January over the Mozambique Channel. Focusing on regions hit by Ana, namely the Sofala and Zambezia regions and the Boeny and Melaky provinces in Mozambique and Madagascar, respectively, we adapted a model by the United Nations Platform for Space-Based Information for Disaster Management and Emergency Response (UN-SPIDER) to effectively assess storm impacts at a resolution of up to 10 m. Our results showed that in Mozambique, more than 195,977 people have been potentially affected by Ana, while in Madagascar this number was down to 79,003. The central region of Zambezia accounted for the majority of flooding occurrences, although the Boeny province accounted for most of the flooding as a proportion of its total area. The Sofala region of Mozambique displayed the highest-affected population and highest-affected urban area, with 108,400 exposed people. However, it was found that only a small proportion of affected areas in all regions of interest (ROIs) were urban areas, accounting for 1.4% of the flooded areas on average. Low mangrove normalized-difference vegetation index (NDVI) changes between before the 2021–2022 cyclone season were found throughout all ROIs, despite the appearance of degraded mangrove patches in the proximity of barren areas at a fine scale (<20 m). Finally, it was found that healthy mangrove forest ecosystems in the Mozambique Channel were effective in protecting highly populated areas from cyclonic events for up to 40 km, on average.