West African Coastal Area: Challenges and Outlook - The Land/Ocean Interactions in the Coastal Zone of West and Central Africa - page 17

Fig. 5 Proportion of coastline
according to the physiography of
mangrove stands (by country)
(SDLAO, UEMOA-IUCN 2011 )

of being nurseries and feeding areas for large numbers of
marine species and water birds.
Beyond the mangrove area associated with the major
estuaries and the archipelago estuary of the Bijagos, the
string of small estuaries from Sierra Leone to Côte d'Ivoire
also represents a network of extremely rich ecosystems,
sheltering a fluvio-marine and brackish water fauna the
diversity of which remains relatively unexplored and
unknown. As far as fish species are concerned, the estuaries
are home to relatively diverse communities that are uniform
on a regional scale, with low seasonal variations compared
to adjacent marine waters.
The biological diversity and ecological processes asso-
ciated with the estuaries relates to the multiple gradients
(salinity, temperature, bathymetry and topography of the
banks and coastal lagoons, conditions and sediment
dynamics and local current systems) which characterise
these milieus, whose conservation certainly constitutes a
priority on a regional scale, in particular given their rich-
ness, their sensitivity to pollution and the risks associated
with

Africa and 45,000 worldwide). The two largest dams
in West Africa are the Akosombo on the Volta in
Ghana, built in 1964, which stands 134 m high (4th
highest in Africa) and has a capacity of 150 billion m 3
(3rd in Africa) and the Kossou on the Bandama in
Côte d'Ivoire, which has a capacity of 28 billion m 3
(6th in Africa).
The consequences of these developments are
multiple, in particular in terms of conserving biodi-
versity, but also in reducing sediment load and the
speed of flows particularly during flood peaks. The
consequences in the coastal zone and the deltas are
often major: salinisation of soils and surface waters,
erosion provoked by sediment deficits, accretion and
delta formation related to energy reduction when
annual expulsion of silt plugs should normally occur.
With the exception of special cases such as the
Gambia and Senegal, which have regional river
development organisations (OMVG, OMVS), the
majority of these dams were designed at national
level, and therefore often without taking into account
in depth the remote impacts of the developments,
which should be considered on a sub-regional scale.

the development dynamics of harbour and urban

infrastructure.

The dramatic effects of dams on coastal areas:
Hydrologic constraints have led to the building of
dams on the majority of large rivers, often for
hydroelectric power (50 % of dams), but also for
agricultural purposes. In certain cases, there are sev-
eral purposes, the Senegal River Basin Development
Organization for example tries to reconcile agricul-
tural production goals with the production of hydro-
electric power and navigation. There are
approximately 150 dams in West Africa, with several
more scheduled. This number is relatively low when
compared to Southern Africa, however, which has the
majority of dams (there is a total of 1,300 dams in

Coastal Conservation and Natural Infrastructure

The natural coastal milieus in West Africa, and in particular
the estuary systems and fluvio-marine connections, con-
tribute directly to producing ecological services that are
useful or even indispensable to the coastal societies, perhaps
even more so in the context of climate change on the agenda
today. These ecological services procure identifiable bene-
fits on every scale, including global: carbon sequestration