Geological Evidence of Shoreline Erosion and Mitigation Challenges

Abstract

A survey was carried out along parts of the coastal stretch of Accra, the capital of Ghana, to determine the existence andthe extent of erosion. The survey was also to determine the effectiveness of the engineering solutions that have been put inplace. Coastal land forms as evidence of erosion were identified during the field survey. These include landslides of steepcoastal cliffs, coastal caves and arches, retreat of coastal cliffs, headlands, stacks and sand dunes. These pieces of evidenceconfirm earlier findings that the coastal shoreline of Accra is being eroded. The extent of erosion, however, is high in soft rocks and low in hard rocks. Several coastal protection measures have been put in place to address the effects of erosion by the sea waves and currents. These include revetments, jetties, ripraps and beach nourishment. Some of the mitigation measures however have shown signs of failure. The signs include rusted metal basket supporting cobbles of gabions, jetties causing down-current erosion of shoreline cliffs, and reduction in coconut population along the shoreline owing to human activities, such as sand winning and diseases attacks. Sand winning along the shore is lowering shoreline morphology and enhancing sea transgression and the destruction of coastal structures.
 Keywords: Erosion; Coastal landform; Coastal protection; Revetments; Shoreline morphology