Assessment of short-term beach sediment change in the Volta Delta coast in Ghana using data from Unmanned Aerial Vehicles (Drone)

Abstract

Reduced sediment in delta beach systems affects delta coast topography and influence delta beach evolution. It opens the deltaic environment up to severe ocean waves and tide attack, which threatens vulnerable coastal communities and increases the risk of the inhabitants. Changes in the beach sediment systems vary from few meters to several kilometres and from hours/days (short term) to decades (long term). Various methods have been developed to analyse changes in beach sediments. This study used Unmanned Aerial Vehicle (UAV or Drone) approach to assess short-term sediment dynamics (from April 2017 to April 2018) in three vulnerable beach systems at Old Ningo (west), Fuveme (central) and Keta (east) communities within the Volta Delta coast in Ghana. High-resolution Digital Elevation Models (DEMs) were developed from the drone images captured, which enabled perpendicular profiles to be generated. Sampled sediments were analysed to determine variation in sizes along the coast. Analysis of the profiles revealed that for the period between April 2017 and April 2018, the beach system at Ningo recorded a net loss of about 8,850 m3 volume of sediment; at Fuvemeh the beach system gained about 12,700 m3 net volume of sediment; in Keta the beach system also gained about 12,100 m3 net volume of sediment. Sediment size analysis revealed that the western section has a relatively finer grain size compared to the east. The coast experienced lower waves between January and February and higher waves between July and August. The pattern of change in the sediment dynamics follows the changing trend in the wave height observed in the region. This indicates that wave dynamics is a major driver of short term sediment change in the Volta delta beach systems. Increased wave intensity as a result of climate change will have a significant impact on the delta beach systems, which will increase erosion and flooding incidence.