Assessing potential coastal flood exposure along the Port-Bouët Bay in Côte d’Ivoire using the enhanced bathtub model

Abstract

Coastal flooding is a growing concern for many communities worldwide due to climate change. This study focuses on the Port-Bouët Bay, located in Abidjan, Côte d’Ivoire. A coastal flood model based on the enhanced bathtub model was used to map the present and future flood extent and assess exposure to quantify the likely affected populations, buildings, and land uses for different scenarios. The model incorporated a digital elevation model, surface roughness, flood water source, and the once a century extreme sea-level scenarios. Validation was conducted against GPS coordinates of recently flooded zones. The analysis revealed that, under current conditions, around 21.58 hectares are vulnerable to flooding, and approximately 2465 people and 544 buildings are exposed to flooding today. Based on future projections, the extent of flooding is anticipated to increase by different ranges depending on the time period and the climate change conditions. By the end of the century, the increase in flooding extent could reach a percentage of 27%, 37%, and 90% under SSP1-2.6, SSP2-4.5, and SSP5-8.5, respectively. The impacts would consequently be worsened with greater number of people and assets exposed to future coastal flood hazard. The land use analysis showed that informal settlements are the occupation most exposed, followed by residential settlements, commercial and industrial land, in that order. The spatial disaggregation of this exposure across neighborhoods indicates that Sogefiha is the most exposed, followed by Petit-Bassam and Vridi. However, a substantial increase in coastal flooding in Vridi by 2100 under the SSP5-8.5 scenario could lead to significant exposure level change for this scenario. This information is critical for evaluating and managing present and future coastal flood risks in the Port-Bouët Bay area and for informing decision-making processes.