Abstract:
Riverine systems are important due to sediment transport to the coast. However,
this benefit is decreasing due to increasing rate of human influences that affect
river flow pattern and sediment discharge to coastal areas, leading to coastal
instability in many countries. This study assessed riverine sediment discharge
contributions to the short-term evolution of the coastline of the Anlo Beach in
Ghana. The Pra River catchment with focus on the coastal frontage (~3.5 km)
and 1.6 km inland was studied, with field surveys for six months (May to
October, 2022). River depths, sediment load, river velocities, and aerials
photographs were collected for each survey, and subsequently processed and
analysed with established protocols in ArcMap to produce shoreline changes,
bathymetry maps, river sediment and water discharges and particle size
distribution. Results from the study suggest a decreasing trend of average daily
river discharges, sediment load and particle sizes. These results were however
larger than what was reported in other rivers in and outside Ghana. Beach
sediment and shoreline are also eroding at a rate of -105,695.72 m3 and -8.22 m
for the six months period. The dynamics of the beach is associated with illegal
small-scale mining that supplies smaller sediment particles to the beach, and
reduction in longshore sediment transport by sea defence structures located to
the west of this beach. Also, shallow bathymetry was observed at the Pra
Estuary, which could lead to flooding during rainfall and high discharges.
