Assessment of Climate Change, Flood Risks and Risk Reduction Measures in the Lower Volta River Basin in Ghana

Abstract

Introduction: Climate change-induced extremes, particularly flooding and sea-level rise, pose escalating risks to low-lying coastal systems globally, with current and future disproportionate impacts on vulnerable communities in sub-Saharan Africa. In Ghana, the Lower Volta River Basin and around its Delta, including the Keta Lagoon Zone, has experienced recurrent and compound flooding driven by climate change and variability, sea-level rise, coastal erosion, land-use change, and socio-economic exposures and vulnerabilities. While existing studies have largely emphasised flood hazards and biophysical exposures, there remains a critical gap in integrated assessments that simultaneously consider the hazards, exposures, vulnerabilities risk reduction measures. Method: This study evaluates changes and variabilities in the climatic conditions, flood projections, and flood risk reduction measures in the Lower Volta River Basin, concentrating on the Ada East District, Anloga District, Keta Municipality, and Ketu South Municipality. A mixed-methods approach was employed, integrating quantitative climatic and spatial analyses with qualitative socio-economic assessments. Long-term rainfall and temperature data (1960–2023) were analysed using trend and variability techniques, including the Mann–Kendall test. Flood hazards and inundation were modeled using GIS-based methods, applying a bathtub approach with a 12 m digital surface model under IPCC SSP2-4.5 and SSP5-8.5 scenarios for three-time horizons: 2020–2040, 2040–2060, and 2080–2100. Flood risk mapping combined the GIS/Analytic Hierarchy Process for weighted and anlysis of risk map, and Principal Component Analysis to load rotate, to present variables on hazards, exposure and vulnerability link to hydro-geomorphological and socio-economic components. Community survey questionnaires based on systematic sampling, focus group discussions, and key informant interviews were used to assess knowledge of hazards, exposure, vulnerability, risk reduction measures and practices. Results: study findings revealed significant interannual variability in rainfall and a rising temperature trend particularly in Keta on average but more warming in Ada by its daily maximum temperatures, alongside strong seasonal intensive rainfall patterns closely linked to recurrent flooding. Sea-level rise projections indicate substantially higher inundation extents under SSP5 8.5 business as usual, with increasing uncertainty toward High-emission scenarios project the inundation of up to 39.1% of the basin's land area by end of this century. Flood risk hotspots correspond with low-lying zones, dense settlements, degraded ecosystems, and areas with limited adaptive capacity. Despite widespread community awareness of flood hazards, risk reduction efforts remain fragmented, with a heavy reliance on structural defences and emergency responses and a limited integration of land-use planning, ecosystem-based approaches, and early warning systems. A strong emphasis on dredging the lagoon and some extent the river was strongly preferred over the physical measures, something that was not adequately visible in existing literatures. Conclusion: The study concludes that flood risk in the Lower Volta River Basin is shaped by the interaction of climate change, exposures and socio-economic vulnerability. The study emphasises the necessity for a comprehensive approach to flood risk management that incorporates climate projections, spatial planning, dredge, ecosystem restoration, early warning systems and infrastructure.