Sea level variations and the impacts along the coastal areas of Nigeria
A brief review of the Nigerian Coastal Areas including the geology, geomorphology, topography, climate, and vegetation has been given. Nigeria has a coastline of about 850km facing the Atlantic Ocean and the coastal areas support a population of about 20 million people and a myriad of economic activities. Global sea level is known to be rising gradually and in some areas due to subsidence either from natural tectonic actions or in combination with fluid withdrawal from under the ground, the rate is much higher than the global average. The latter situation is believed to be the caseon the Nigerian Coast where oil and gas exploitation and water supplies are being withdrawn from under the ground at uncontrolled rates. Tidal data obtained from the Nigerian Coast have been used to study the various sea level variations on that Coast.Using 19 years of tidal data from Bonny, the sea level is observed to be rising at the rate of about 1mm per annum compared to the global average results between 1 -2mm per annum. Forty years of tidal data from Takoradi Port, Ghana also on the Atlantic Coast of West Africa have showed a rise of 3.9mm per annum. The contribution due to subsidence has not been determined because the tide gauge benchmark have not been connected to a stable control point and monitored regularly. Maximum surges of the order of 7m were observed. Other variations and characteristics of the sea level on the Nigerian Coast include seasonal, tidal ranges, frequency distribution of tidal data, and behaviour of the tidal data in absence of some major tidal constituents. The impacts of these variations on the Nigerian Coast have been studied. These include erosion, flooding and inundation, salinity intrusion, destruction of coastal settlements, deforestation and destruction of the marine ecosystem, increased effect of oil spillage on the Coastal environment, and destruction of infrastructural facilities and industries. Response measures have been discussed and the integrated management of the coastal areas of Nigeriais seen as a very important response in addressing the impacts, development, and management of the Nigerian Coastal environment. Continuous data collection, monitoring of the various processes on the Coast, further researches and regional cooperation on the issue of sea level variations are recommended as very important components
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