Spatio-temporal analyses of shoreline change in the Western Region of Ghana

Shoreline change is an issue of concern to coastal stake holders because the coastal zone is home to over 60% of the world's population. In Ghana, for instance, shoreline change has been associated with loss of economic lands and properties. Previous researches have showed that the coastline is eroding at variable rates in spatial times. Studies have also shown that shoreline change trends vary in geologic time scale, such that erosion or accretion is reversible along same shore at different time periods. The Eastern and Central Zones of the Ghanaian coast are said to be receding while the Western Zone is thought of as stable. This opinion, however, contrasts field observations and interview with local coastal community members. This research sought to determine the shoreline change trends in the study area over short-term (1974-2005) and long-term (1895-2005) interval so as to ascertain the variability of shoreline trends to aid future prediction. From available multi-temporal datasets of topographic maps and ortho photographs, the shoreline feature was extracted using the High Water Line (HWL) as an indicator. From which the shoreline time series datasets were overlaid before transects cast using DSAS an extension of ArcGIS. The shoreline change statistics were computed analysed. The results show a mean rate change of - 4.18 m/year for the entire study area, while the Western Section recorded a mean of 5.4 m/year and the Eastern Section recorded a mean of 2.36 m/year. An average shoreline change rate of -6.55 m/year recorded for the entire study area in the long term analysis. The Eastern Section is eroding at a rate of -2.18 m/year while a portion of the Western Section registered highest change rates with a mean of -11.64 m/year. Examination of the short and long terms shoreline change trends revealed a condition of long period of irreversible recession of the shoreline with little accretion at most portions of the study area.