Abstract
Estuarine shorelines similar to marine coastlines are highly dynamic and may increase disaster risk in vulnerable communities. The situation is expected to worsen with climate change impacts and increasing anthropogenic activities such as upstream water management. This study assessed shoreline changing trends along the Volta river estuary in Ghana as well as the marine coastline using satellite imageries, orthophotos and topographic maps spanning a period of 120 years (1895, 1990, 2000, 2005 and 2015). Linear regression method in the Digital Shoreline Analysis System (DSAS) was used to determine the estuary shoreline migration trend by estimating the shorelines rate of change for the eastern and western sides of the estuary. The rates of change of the marine coastlines on the east and west of the estuary were also estimated. The results show that the eastern and western shoreline of the estuary are eroding at an average rate of about 1.94 m/yr and 0.58 m/yr respectively. The coastlines on the marine side (eastern and western) are eroding at an average rate of about 2.19 m/yr and 0.62 m/yr respectively. Relatively high rates of erosion observed on the eastern estuarine shoreline as well as the coastline could be explained by the reduced sediment supply by the Volta River due to the damming of the Volta River in Akosombo and the sea defence structures constructed to manage erosion problems. The trend is expected to increase under changing oceanographic conditions and increased subsidence in the Volta delta. Effective management approach, such as developing disaster risk reduction strategy, should be adopted to increase the resilience of the communities along the estuarine shoreline and increase their adaptive capacity to climate change hazards and disasters.
Highlights
Estuarine shorelines are naturally dynamic and continuously shaped by natural and anthropogenic factors (Bio et al 2015; Appeaning Addo et al 2008; Jayson-Quashigah et al 2019)
Climate change induced oceanographic conditions is expected to increase coastal erosion and flooding hazards associated with estuarine shoreline dynamics (Arthurton et al 2000)
This paper presents results of Volta estuary shoreline morphological change assessment from 1895 to 2015 within the Volta delta region in Ghana
Summary
Estuarine shorelines are naturally dynamic and continuously shaped by natural and anthropogenic factors (Bio et al 2015; Appeaning Addo et al 2008; Jayson-Quashigah et al 2019). Monitoring the geometry of the estuarine shoreline morphology is key to understanding the evolution trend in the estuarine shoreline position over time and how it impacts the environment (Oyedotun 2014) It reveals how estuarine shorelines are responding to climatic and anthropogenic induced stressors that have the potential to result in environmental hazards. Geographical Information Systems (GIS) and Remote Sensing approach in mapping high erosion risk zones have increased accuracy in feature identification, feature extraction and change detection in coastal zones significantly (Natesan et al 2015; Kannan et al 2016; Van and Binh 2008) They help in collecting data from inaccessible and rapidly changing or hazardous environment (Wiafe et al 2013). Shoreline will be used to represent the riverine side of the coast while coastline will be used to represent the marine side of the coast
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