EDIT
Huge breakers constantly battering Benin's coast -- and the rest of the shoreline on the Gulf of Guinea -- are starting to take their toll. Ivory Coast, Ghana, Togo and Nigeria are also fighting to stop the sea from gulping up chunks of land.
In tiny Benin, the erosion on its narrow stretch of coastline was first recorded a century ago. The phenomenon has been exacerbated by the rise in seawater levels, attributed to global warming, and by massive construction projects such as the Nangbeto dam in Benin and the Akossombo dam in Ghana, as well as the development of deep-water ports at Cotonou and Lome, according to experts.
"The coastline to the east of Cotonou has moved back 400 metres (yards) in 40 years, that is an average of 10 metres a year," said Paul Houssou who heads up an anti-erosion project for the UN Environment Programme (UNEP).
Worldwide, seawater levels are estimated to have risen between 10 and 20 centimetres (four to eight inches) in the past 100 years and that trend is speeding up. A study by Columbia University showed that sea water levels on the West African coast could rise by more than 50 centimetres between now and the end of the century.
EDIT
http://www.terradaily.com/reports/Benins_Cotonou_a_city_slowly_swallowed_by_waves_999.html