Temporal (1948-2012) and dynamic evolution of the Wouri estuary coastline within the gulf of Guinea

Abstract

The Wouri estuary is located in the Gulf of Guinea on the Atlantic coast of Cameroon's coastline plain (3°49' and 4°04' north latitude and 9°20' to 9°40' east longitude), and is strongly influenced by coastal dynamics that have remained unquantified over a long period of time. This study analyzed the historical evolution of the Wouri estuarine coastline between 1948 and 2012. Variations in the estuarine evolution of the Wouri were studied from (i) minute topographic extracts from 1948, (ii) 1996-1999 nautical charts, and (iii) 2012 spatial map vectors. The net temporal spatial variation rates were calculated using the statistical methods of the Digital Shoreline Analysis System (DSAS). These change rates were also calculated over two time intervals (1948-1996 and 1996-2012) and over a 64-year period (1948-2012). The study reveals highly disparate results. Indeed, kinematics show that the Wouri estuary was dominated by erosion in its downstream section, with 262.83 ha for -3.2 m/year and 110.56 ha for -5.8 m/year between 1948-1996 and 1996-2012 respectively, and by accretion on the other hand in its upstream section, with 239.17 ha for 4.3 m/year in zone 5 between 1948-1996 and 150.82 ha for 12.6 m/year in zone 4 between 1996-2012. Thus, over the 64-year period (1948-2012), we have a dominance of variation by erosion downstream and conversely by accretion upstream, marked by the presence of amplifying factors (anthropogenic pressure and climate change) of the rate of variation of morphological evolution at the beginning of the 21st century, as compared to the middle-20th century. The observed development of sediment loss and accumulation, both influences and will influence, the sediment regime along theWouri estuarine coastline. There is a need to develop a systematic sub-regional coastal surveillance activity to effectively manage Cameroon's coastline system.