Flood Vulnerability Mapping of Port Harcourt Nigeria, Using Geographical Information System and Multi Criteria Decision Analysis (GIS-MCDA)

Flooding is a major issue in Port Harcourt exacerbated by climate change. The city experiences annual flooding on a significant scale, with threats to the population and infrastructure. Poor urban planning, management, rapid urbanization, inadequate storm drainage systems, climate variability and extreme weather events, associated with climate change, are all contributing factors exacerbating the flooding issue in Port Harcourt. This study focuses on flood vulnerability mapping in Port Harcourt, integrating Geographical Information System and Multi Criteria Decision Analysis (GIS-MCDA) using selected variables including Elevation, Slope, Aspect, flow accumulation, flow direction, land surface temperature (LST), Rainfall, soil and Distance to stream to develop a vulnerability map. Findings revealed that the most predominant vulnerability level was High Vulnerability, which accounted for 49.87% of the total area, followed by Moderate Vulnerability at 40.53%, Low Vulnerability at 9.41%, Very Low Vulnerability at 0.17%, and Very High Vulnerability at 0.02%. For the statistical significance of the variables used, Rainfall, Slope, Distance from Streams and water body all contributed significantly to reducing deviance, as indicated by their small p-values, while Flow accumulation, Flow direction and Soil were not statistically significant due to their P-values greater than 0.05. The vulnerability maps obtained provides valuable information for flood mitigation and preparedness efforts. Hence, we recommend that high and moderate vulnerability areas calls for prioritizing measures like infrastructure improvements, early warning systems, and community awareness campaigns. Also, with a combination of vulnerability maps with information on population density, infrastructure, and land use, mitigation strategies could be tailored to specific contexts, especially in densely populated flood-prone locations with critical infrastructure.