Abstract
Fluvial sediment discharge to coastal area contributes to the stability of the coast. Deposition of fluvial sediment discharge is an important source of beach nourishment, nutrient for aquatic ecology and habitats. However, human development and interventions on rivers in the form of dams and flood alleviation schemes tend to reduce fluvial sediment supply to the coast, thus impacting on coastal stability and geomorphology. This paper assessed the contribution of fluvial sediment discharge to coastal stability for the study area. Multi-temporal topographic data acquired in 1974 and 2005; flow data on major rivers in the study area and field observations were used. Digital Shoreline Analysis System was for computation of shoreline change rates. Applying the power regression relation, sediment discharge by rivers was computed for rivers in the study area. The study revealed that rivers in the catchment supply about 1.8 × 105 tonnes of sediment to the shores daily, thus supporting coastal stability. Results of shoreline change showed relatively stable beach at the mouth of rivers and lagoons due to the sediment discharge. It is recommended that policies are implemented to reduce the impact of dams and beach sand mining activities along river channels to ensure the stability of Ghana’s Western coastline and the coastline of neighbouring countries. Key words: Coastal rivers, fluvial sediment, impacts of human interventions, coastal stability, Western Region of Ghana.
Highlights
Sediment supplied by rivers constitutes between 80 and 95% of total sediment deposited at the coast (Walling, 2006; Bittencourt et al, 2005)
The total sediment yield significant to the beach and contributing to the coastal stability of the case study area is estimated to be about 1.8 × 105 with Rivers Pra and Ankobra supplying more than 50% of the total estimate
Since suspended sediment constitutes about 90% of the total fluvial sediment supplied in the study area it is reasonable to conceive that the quantity of sediment supplied at the river mouths tend to decrease as one moves farther from the river mouths
Summary
Sediment supplied by rivers constitutes between 80 and 95% of total sediment deposited at the coast (Walling, 2006; Bittencourt et al, 2005). Such deposition is important for aquatic ecology and habitats (e.g. saltmarshes and tidal mudflats) (Owens, 2007). Saltmarshes and tidal mudflats) (Owens, 2007) It serves as a rich source of sediment supply for many settlements within the lower catchment of such rivers, high agricultural yields are often recorded.
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