Impacts of lagoon opening and implications for coastal management: case study from Muni-Pomadze lagoon, Ghana

Lagoon-barrier systems are a dynamic coastal environment. When an ephemeral connection between a lagoon and the ocean develops, it has significant impact on hydrology, sedimentology and ecology. Increasingly, human actions and sea level rise also influence lagoons with the potential to increase their connectivity with the ocean. The Muni-Pomadze lagoon in central Ghana is a small lagoon-barrier system that is intermittently open to the ocean. Following opening in 2014 the lagoon was open to the ocean for more than two years. Causes for the unusually long period of lagoon opening are unclear although human intervention has played a role. Field observation, digital mapping and GIS analysis of the shoreline during the two year period of lagoon opening has enabled an understanding of how the lagoon-ocean connection has impacted coastal morphology, erosion and sedimentation. Opening has resulted in rapid changes to the location of the barrier breaching (tidal inlet), erosion on the barrier and sedimentation in the lagoon. Such modifications have implications for local resources and ecosystem services that underpin the livelihood and wellbeing of local communities. Elucidating how a connection to the ocean impacts lagoons and the coastal communities they support are important to managing lagoons not only in Ghana but across West Africa.