Holocene development and coastal dynamics at the Keta Sand Spit, Volta River delta, Ghana

Field process measurements and OSL/AMS-dating methods were employed in combination to examine the Holocene evolution of the Keta Sand Spit, east of the Volta River delta in Ghana, as well as the hydrodynamic processes driving present spit dynamics. Large-scale changes in shoreline configuration, with far-field implications for sediment supply to downdrift coasts along the Bight of Benin, have been rooted in river mouth switches, which are dated at approximately 5–7000 yr BP and 2500 yr BP. The most recent barrier stage is the present Keta Sand Spit, which originated about 2500 yr BP. The spit migrates slowly in an easterly direction due to gradients in longshore sediment transport induced by morphodynamic interactions between wave-induced currents and shoreline orientation. These autochthonous longshore transport gradients are the major reason for the large coastal erosion rates in the lee of the Sand Spit, rather than a decreased sediment supply caused by damming of the Volta River. •OSL-datings near the Volta River delta reveal a complex depositional history of the area.•Delta switches likely occurred about 6000 yrs BP and 2500 yrs BP.•Present coastal erosion is driven by internal morphodynamic feedbacks of the Keta Sand Spit.•The Akosombo Dam is not the main cause for the coastal erosion in eastern Ghana.