Contenu du sommaire

Coastal Development and Evolution of a Lagoon System ; A Case Study in Benin In 1885, when opening an artificial channel between lake Nokoue and the Atlantic Coast through the sandy coastal bar, man introduced a new element into the natural balance of the coastal system in South Benin. The disequilibrium that resulted gave immediate rise to significant repercussions on the environment and on its exploitation by the indigenous fishermen. Nevertheless, a new balance gradually emerged. It was soon disrupted, however, by the construction in the late 1950's of a deep water harbour in Cotonou, the existence of which completely changed the characteristics of the coastal current. Direct and indirect effects were so serious that in 1978 the authorities ordered the construction, near the channel mouth, of a regulating dam, the purpose of which was to check the penetration of salt water into lake Nokoue ; but this dam immediately led to unexpected disruptions, and its completion was rendered useless. The still unstable present situation is satisfactory as far as the fishermen of lake Nokoue are concerned. However, it entails very negative aspects for the development of Cotonou, a town where now thousands of urban dwellers are subject every years to floods, at times of disastrous proportions because of their extent and duration, and which, moreover, threaten their health as well as their homes.

Evolution of a Delta Coast and Anthropic Actions : the Case of the Volta Delta in Ghana Because of the displacement of the delta arms and the construction of Akossombo Dam, the eastern portion of the Volta delta is subject to rapid coastal erosion that has destroyed almost the whole of the town of Keta. A study of the hydro-sedimentary evolution dynamics has brought into relief the complex occurrences that are developing on this sector of the coast. Because of this study, it is possible to propose an alternative solution to the protection means - of doubtful efficacy and costly - of huge construction projects that are prefered by the authorities for political and cultural reasons.

The lagoon-dotted Shoreline of Côte d'Ivoire : Physical Environment, Settlement, and Anthropic modifications The Côte d'Ivoire shoreline entered history only in the recent past : there are hardly any vestiges of the periods preceding the great discoveries. The first attempts at settlement by colonists began in the eighteenth century, and they only became permanent towards the middle of the nineteenth century, a short time after the settlement of the main ethnic groups still living today on the lagoon shores. The introduction of modern techniques had as great an impact on the natural environment as that of man's appearance in it. For example, the forest has been damaged by more rapid means of exploiting it. The fragile equilibrium of the coast-line has, for its part, suffered from too ambitious development programs ; but, until contrary evidence is provided, neither the digging of the Vridi channel nor the shutting of the Kossou dam have caused, in the years that followed, any notable changes in the configurations of the coast.

The Uniqueness of the Mangroves of Guinea in the Wet Tropical World The ecological status of Guinean mangroves derives from the union of a terrigenous environment, which is very favorable for the development of muddy zones, and of a morphological-climatic instability amplified by the extension of coastal conversions and the anthropic degradation of the pre-forest savannahs of Fouta-Djalon. A comparison with other coastlines in the wet tropics brings out the unique features of the growth cycle of Guinean mangroves and the special constraints to which their future development will have to become adapted.

The Maritime Marshes of Mauritania : Protection and Valorization The Mauritanian coastline, subject to a semi-arid climate in the Southwest and to an arid climate farther north, has several types of coastal marshes. They are not exploited at present, but a very lovely park, Parc National du Banc d'Arguin, encompasses one of them . It would be interesting to know the exact causes for the depletion and disappearance of the mangrove to the north of Nouakchott. If, as we believe, these causes are not related either to drought or to the water temperature, the planting and farming of trees could indeed improve the living standards of the inhabitants along the coast.