Estimating the fluvial sediment input to the coastal sediment budget: A case study of Ghana
Estimating the fluvial sediment input to the coastal sediment budget: A case study of Ghana
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Date
2011-08
Authors
Boateng, Isaac
Bray, Malcolm
Hooke, Janet
Journal Title
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Publisher
University of Portsmouth
Abstract
Knowledge of fluvial sediment supply to the coastal sediment budget is important for the assessment of the
impacts on coastal stability. Such knowledge is valuable for designing coastal engineering schemes and the de velopment of shoreline management planning policies. It also facilitates understanding of the connection
between rivers in the hinterland and adjoining coastal systems. Ghana's coast has many fluvial sediment sources
and this paper provides the first quantitative assessments of their contributions to the coastal sediment budget.
The methods use largely existing data and attempt to cover all of Ghana's significant coastal rivers. Initially work
was hindered by insufficient direct measured data. However, the problem was overcome by the application of a
regression approach, which provides an estimated sediment yield for non-gauged rivers based on data from
gauged rivers with similar characteristics. The regression approach was effective because a regional coherence
in behaviour was determined between those rivers, where direct measured data were available. The results of
the assessment revealed that Ghana's coast is dissected by many south-draining rivers, stream and lagoons.
These rivers, streams and lagoons supply significant amounts of sediment to coastal lowlands and therefore con tribute importantly to beaches. Anthropogenic impoundment of fluvial sediment, especially the Akosombo dam
on the Volta River, has reduced the total fluvial sediment input to the coast from about 71×106 m3
/a before 1964
(pre-Akosombo dam) to about 7×106 m3
/a at present (post-Akosombo dam). This sharp reduction threatened
the stability of the east coast and prompted an expensive ($83 million) defence scheme to be implemented to
protect 8.4 km-long coastline at Keta. Sections of Ghana's coast are closely connected to the hinterland through
the fluvial sediment input from local rivers. Therefore, development in the hinterland that alters the fluvial
sediment input from those local rivers could have significant effects on the coast. There is the need, therefore,
to ensure that catchment management plans and coastal management plans are integrated or interconnected
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Citation
Boateng, I., Bray, M., & Hooke, J. (2012). Estimating the fluvial sediment input to the coastal sediment budget: A case study of Ghana. Geomorphology, 138(1), 100-110.