ASSESSMENT OF COASTAL FLOOD VULNERABILITY USING RASTER-BASED MODELLING IN QGIS UNDER SEA LEVEL RISE AND STORM SURGE SCENARIOS: A CASE STUDY OF KETA MUNICIPAL DISTRICT, GHANA

 

Read full article: 1. https://doi.org/10.13140/RG.2.2.12170.32965

Abstract

Coastal flooding is a major threat to low-lying areas, especially in delta regions and lagoons. This study uses a raster-based flood simulation method in QGIS to evaluate potential flooding patterns due to rising sea levels and storm surges, specifically looking at a 3 m storm surge scenario. The research focuses on the Keta Municipal District and its immediate coastal communities, which are highly vulnerable to flooding because of their low elevation and closeness to the coast. Raster analysis techniques were employed to simulate flood extents for sea level rises of 4 m, 5 m, and 6 m. Boolean raster operations and map algebra were used in mapping inundated areas for each scenario. To make the simulation realistic, 3 m storm surge was run in conjunction with the three sea level rise scenarios ; 4 m, 5 m and 6 m to reflect extreme coastal flood rather than just gradual sea level rise. The results show a quick increase in flooded areas between the 5 m and 6 m scenarios, emphasising how flooding spreads across flat coastal land. Settlements, transport routes, and wetlands are particularly vulnerable under the 5 m and 6 m scenarios. In order not to misclassify flooding, the Digital Elevation Model was processed through sink filling beforehand, flow direction, and flood depth were also simulated with the purpose of outlining potential inundation areas. The flood maps highlight extensive exposure within the municipality, with flooding covering about 84%, 86%, and 89% of the total land area for the 4 m, 5 m, and 6 m scenarios, respectively. The patterns show that low-lying coastal plains and settlements near lagoons are most at risk. Although the modelling framework is simplified, the study gives valuable first estimates of flood exposure that can aid decision-making in areas with limited data. It demonstrates the value of open-source geospatial tools for assessing coastal flood risk and offers a method that can be replicated in other coastal regions of West Africa. The study concludes that including storm surge data in raster-based simulations enhances the realism of hazards and supports better coastal planning, disaster readiness, and climate adaptation efforts.



Keywords: coastal flooding, sea level rise, storm surge, raster modelling, QGIS, Keta municipal district, flood inundation, climate change, GIS, coastal vulnerability.

Read full article @:

1. https://doi.org/10.13140/RG.2.2.12170.32965

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