Environment effects of coastal sedimentation: A case study of Shirazi-Funzi Lagoon
The aims of the study were to determine factors that affect sedimentology of the Shirazi-Funzi lagoon in Kenya; sediment mineralogy and source environments; economic importance of the lagoon; environmental problems within it; possible management policies for Kenya's coastal lagoons. Sediment grains distribution, composition and dynamics were studied; suspended sediment discharge by Ramisi River was determined, and POC was studied to investigate possible contribution of the river to nutrient replenishment in the lagoon. Geomorphology, hydrodynamics and socio-economic activities were also studied. The lagoon is dominated by terrigenous sediments, comprising mostly of fine quartz sand. Grain size diminishes gradually from mainland shoreline towards the tidal inlet. Carbonate mineral content ranges from 0.01 to 5.0% by weight in most parts of the lagoon, but adjacent to the coral reef, it increases to over 80% by weight. Total organic matter ranges between 0.01 to 2.0% by weight in the channels, but increases to over 50% by weight at channel banks, and decreases to minimum levels towards the centre of the mangrove islands. Cliffs, beaches, channels, sandbars and mangrove islands are the physiographic features of the lagoon. Off the lagoon, sea-wards is a trough, due to Pemba channel, with a maximum depth of 207 m. Wave energy is dissipated exponentially from the tidal inlet toward mainland shoreline. Annually, Ramisi River discharges about 1.534 x 10 super(3) tons of suspended matter. POC of surface water at Mamuja channel ranged from 645 mg/CI to 1940mgC/I in 24 hours, the highest values occurring during tidal ebbs. The main socio-economic activities in the lagoon are fisheries and mangrove exploitation. The rate of harvesting of fisheries resources is negatively correlated with that of mangrove resources. The main environmental problem in the lagoon are shoreline erosion, lagoonal sedimentation, mangrove felling and vulnerability of the lagoon to global-induced sea-level rise. Policies are suggested, which require research-based data, on management of Kenya's lagoons, in light of the observed environmental problems.
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| Format: | Book Section biblioteca |
| Language: | English |
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Acts Press
1998
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| Subjects: | Geomorphology, Environmental effects, Sedimentation, |
| Online Access: | http://hdl.handle.net/1834/8870 |
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