Management of a Tropical River: Impacts on the Resilience of the Senegal River Estuary - The Land/Ocean Interactions in the Coastal Zone of West and Central Africa - page 45

In addition, groundwater changes related to the devel-
opments of rivers are seen as a major issue in many parts the
world. In Morocco, for example, following the construction
of the Mohamed V Dam, the coastal wetlands of Moulouya
are no longer subject to flooding from rivers, which is
responsible for the recharge of groundwater used for irri-
gation. Both water and soil have become increasingly saline
as arable lands are abandoned; this has caused farm workers
to emigrate (Arthurton et al. 2008 ). Groundwater contami-
nated by saltwater intrusion makes inappropriate irrigated
crops. The population around the lower estuary is highly
dependent on groundwater which constitutes their irrigation
system for market gardening. The problem remains severe
since the opening of the new mouth; the salinization of
groundwater has reached critical levels, causing an exten-
sion of the salt marshes and a progressive loss of farmland.
Important changes were noted in the coastal hydrody-
namics such as the tidal patterns. During high tides, there is
a large increase in marine water with an important evacu-
ation of the river flows during low tides. The acceleration of
coastal erosion cause real threats to the area. The mangrove
swamp has shown a progressive degradation following the
opening of the new mouth. The area of the mangrove
swamp has fallen by 636 ha (or 59 %), from 1086 ha in
1979 to 450 ha in 2003 (Kane 2010 ). The area of the island
of Doun Baba Dièye decreased by 8 % between 2003 and
2007, from 257 to 236 ha and now has completely dam-
aged since October 2012.
Many villages such as Dieule Mbame, Tassinere and
Keur Bernard (Fig. 2 ) are under threat. Resettlement of
populations constitutes indeed a real problem as rehousing
in the lower estuary is a big issue relatively to the avail-
ability of land.

appears to be a risk-prone area, where the conjunction of
several factors can produce incommensurable effects.
Physical conditions (geomorphological, lower altitude)
determine an area where risk is permanent and expose
populations to hazard. Moreover, communities may aggra-
vate the intensity or frequency of certain phenomena and
the reach of their effects.
To prevent the occurrence of flooding requires the means
to contain floods, such as the construction of dams or river
dikes and the establishment of non-structural measures such
as alarm systems for flood prevention, public participation,
and institutional commitment (Tingsanchali 2012 ). How-
ever, the new opening of the mouth, which aims at reducing
population vulnerability within the estuary, has been
favored over precautionary principles. Also, questions
concerning the human impact on risk aggravation are
inevitably directed toward inquiring about negligence dur-
ing establishment of these new developments, weaknesses
in protection systems including alert and prevention, safety
devices, and toward any negligence which may obstruct
proper control and handling of these phenomena as well as
reduction in the consequences.
Considering the impact of an extremely vulnerable area
at the opening of ''Langue de Barbarie,'' which has had the
consequences described above, the occurrence of a natural
disaster will only increase the fragility of the system. It is
probable that rising of sea levels will intensify environ-
mental pressures and undermine sustainable development.
This will result in higher risks of flooding and greater
ingress of seawater while the lower estuary is already
experiencing groundwater salinization due to exchanges
between river and marine water following the opening of
the new mouth. Populations located in low and coastal
areas as well as in deltas and which are estimated to make
up approximately 10 % of the world's population will be
particularly vulnerable to climate change (Nicholls et al.
2008 ; McGranahan et al. 2007 ). Simulations conducted by
Durand et al. ( 2010 ), based on the potential height of water
at the end of the rainy season and carried out for several
scenarios for the rise in sea level, show that a 0.5-m sea-
level rise would be enough to flood part of the town of
Saint-Louis at times of annual high waters and that it
would be almost completely submerged in the event of a 1-
m rise.
Figure 5 represents the probable evolution of submer-
gence of St-Louis based on increase in sea-level areas. It
should be noted that the island and the sandy spit of
''Langue de Barbarie'' will be less affected than the ''Fau-
bourg de Sor.'' The surface losses are 3 and 126 ha or 4 %
of the territory up to 1 m. However, as we mentioned ear-
lier, the ''Langue de Barbarie'' currently experienced
recurring phenomena of coastal erosion. This situation can
be explained by the importance of altitudes of more than

Box 1: The opening of two new mouths
Recently, in October 2012, it has been reported
that the two natural openings which are distant of
150 m have accelerated the process of dismantling of
the sandy spit of ''Langue de Barbarie,'' and the
disappearance of the coastal habitats. After having
amalgamated with the breach opened in 2003, they
reinforced

the problem of the salinization of the

grounds in the lower estuary.

Risks Linked to Water Management
in the Senegal River Estuary

The major risk in this area is linked to population settle-
ments and the impacts of the various changes to the eco-
system and the resources. The Senegal River estuary