Environmental Engineering Reference
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Fig. 2
Digital elevation model Saint-Louis
and 2 %. Also, at this point, changes in the water level will be
low in case of flooding and lead to greater variation in the
extent of water. Many cities are located in flood areas as they
are likely to be places favorable for urban development
(Tingsanchali 2012 ). The town of Saint-Louis is in a similar
situation to many others throughout the world, for example, in
Ethiopia where floods occur regularly in all parts of the
country at times of rising water levels downstream of large
basins and in low ground (Ayalew 2009 ). In Saint-Louis,
following many years of drought, the local population occu-
pied much of the river bed normally under water; conse-
quently, many districts may be flooded in the event of a major
rise in water level. This raises the important issue of popu-
lation relocation during rainy seasons, as it is also a limitation
to the smooth flow of people and goods. This weakening of
the socio-economic system in the face of the threats of
flooding prompted the Senegalese authorities to open a new
mouth on the ''Langue de Barbarie'' in 2003 to enable a rapid
escape of excess water toward the sea.
Thus, since July 1986, the Diama Dam has controlled
most of the water influx into the estuary. An average annual
of 255 m 3 /s is released into the river below the dam during
this
Fig. 1
Location of the Senegal River basin and estuary
The Sahelian zone has in recent years recorded a return of
heavy rainy seasons. In the tropical wet area of Guinea, high
basin River, we note abundant precipitation creating an
increase in the river water flow. The increase in the river
water levels generates overflows which further increase the
risks of floods. The town of Saint-Louis stuck between the
Senegal River and Atlantic Ocean (Fig. 1 ) is built on an area
dominated by deposits of mud and is particularized by the
omnipresence of water (Kane et al. 2013 ). The digital ele-
vation model (Fig. 2 ) shows the lower elevations of the city of
Saint-Louis and identifies the most sensitive areas to flooding.
Low areas represent 53 % of which 17 % have altitudes
between -1 and 0 m and 36 % emerging barely above sea
level is between 0 and 3 m. They correspond, in fact, the main
bed of the river is located in ''Faubourg de Sor.'' The slopes
are also very low; they are between 0 and 9 %. In ''Faubourg
de Sor,'' the slopes are practically nil and they vary between 0
period.
Water
flows
through
the
dam
since
1986
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