Vulnerability of Ghana’s Coast to Relative Sea-level Rise: A Scoping Review

Coastal areas are regions of essential value that are home to a myriad of services. However, population growth and climate change along with their cascading impacts have had profound impacts on their topography and evolution. Consequently, many coastal regions, of which Ghana’s coast is no exception, are incessantly plagued with hazards that are increasing in both magnitude and frequency. Predominantly through the recurrence of floods and erosion, Ghana’s coast is increasingly becoming susceptible, with huge socioeconomic implications considering its environment dependent economy. Several previous attempts have been made to assess Ghana’s coastal vulnerability to comprehend the complexities underpinning the occurrence of these hazards. Most studies blame global sea-level rise, but coastal land subsidence could also have significant impacts. Indeed, land subsidence is a major component of relative sea-level rise in many coastal cities worldwide. Drawing on extant literature in Ghana, this scoping study provides an overview of three crucial and interrelated dimensions: sea-level rise, subsidence and coastal vulnerability. We also identify crucial knowledge gaps which impede comprehensive risk assessment of Ghana’s coast. The survey findings indicate a significant understudy of these issues albeit posing potential threats to Ghana’s coast. It brought to light the absence of a ground-validated subsidence study; a non-identification of potential local subsidence drivers; a non-availability of a subsidence-infused coastal vulnerability assessment; non existing studies on combined effects of climate change and subsidence; and huge deficits in available data for numerical modelling of coastal subsidence. A case study of the Volta delta using the PS-InSAR technique and Global Positioning System (GPS) surveys is also provided. It establishes the occurrence of subsidence. Interferograms of Sentinel-1 data from 2016 to 2020 indicated deformation rates ranging from -9.16 mm/yr to 1.77 mm/yr, with a majority of persistent scatterers (99.81%) showing land subsidence. Guided by the identified knowledge and data gaps and the need to mitigate impacts, the study recommends a thorough assessment of relative sea-level rise and coastal vulnerability; a continuous and long-term monitoring framework for drivers of change; a review of coastal management strategies; and the establishment of continuous GPS stations, tidal stations, elevation benchmarks.