Quantifying and Predicting the Contribution of Sea-Level Rise to Shoreline Change in Ghana: Information for Coastal Adaptation Strategies


The purpose of this study is to estimate the contribution of sea-level rise (SLR) in Ghana over the last decades and provide an estimation of shoreline retreat due to the projections of regional SLR. This study first analyzes historical shoreline change in Ghana from 1974 to 2015 using satellite images and orthophotos. Second, this study quantifies the SLR contribution to historical shoreline change using sea-level trend estimates from satellite observations, results from digital elevation model analysis, and shoreline change rates. This study finally makes predictions of shoreline in Ghana on the basis of modified Intergovernmental Panel on Climate Change Fifth Assessment Report representative concentration pathways (RCPs) scenarios for Ghana. On average, sea level has risen by about 5.3 cm over the last 21 years and accounts for only 31% of the observed annual coastal erosion rate (about 2 m/y) in Ghana. On the basis of the projected model ensemble-mean rise in sea-level (2.6, 4.5, and 8.5 RCPs) scenarios and assuming that SLR will also contribute to 31% of shoreline retreat in the future, by the year 2025, about 6.6, 4.7, and 5.8 m of coastland in Ghana with lowest slope range (0–0.4%) are projected to be inundated respectively. These projected changes increase to 19.8, 20.7, and 24.3 m by 2050 and further to 36.6, 51.6, and 83.9 m by 2100 for the 2.6, 4.5, and 8.5 RCPs respectively. The analysis that separates sea-level contribution to coastal change from other contributing factors could provide useful information about climate impact for coastal adaptation strategies. This study, however, recommends further research into the anthropogenic and other factors that contribute about 69% of the annual erosion rate in Ghana to help improve adaptation efforts.
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