Environmental Engineering Reference
In-Depth Information
Sanaga delta; the ''Bouches du Cameroun''; the volcanic
horst proper the Rio-del-Rey; and the Niger delta.
The Douala-Rio-del-Rey basin takes the shape of an
isosceles triangle with its peak at Yabassi and its side
measuring 150 km. The height of the triangle corresponds
to the maximum width of the basin (50-60 km). The relief
has preserved traces of destructive tectonic activities which
calved out the base into steps. The 200 m isobath Douala is
at the same distance from the coast (40 km), it is off Kribi-
Campo. On the other hand, within the Rio-del-Rey basin,
this isobath lies up to 80 km from the beach. The conti-
nental shelf in this area is twice as broad as it is in the
South-East of Mount Cameroon.
inter-tropical front within the continent. Along the coast,
rainfall intensity increases from south to north. Recorded
values show average annual rainfall of 3,000 mm in Kribi,
4,000 mm in Douala and more than 11,000 mm in Deb-
undscha. There are two distinct seasons: a long rainy season
of more than 8 months and a dry season which generally
stretches from November to February. Air temperature is
high throughout the year (above 25 C).The coastal climate
is also characterized by monsoon winds of the Guinean type,
predominantly south-westerly. These winds cause humidity
values to be most always at saturation point. Winds speeds
attain exceptional values of 18 m/s (April 1993). In general,
average wind speeds recorded over a period of 10 years
(1983-1993) vary between 0.5 and 2 m/s.
Cameroon coastal surface waters are warm throughout
the year, unlike the coastal waters of other West African
countries (Côte d'Ivoire, Ghana, Togo, Benin, etc.) which
are characterized by seasonal upwelling. Water tempera-
tures remain always above 24 C. This warm water layer
has a thickness of 20-30 m (Crosnier
1964
) depending on
the location and the season. It overlies a less warm water
layer whose temperature varies between 18 and 20 C.
There is a thermocline between the two water layers which
plays an important role in the dynamics of living organisms.
Cameroon's coastal waters are generally characterized by
low salinity due to high rainfall and a dense river network
which supplies freshwater. Lafond (1965) recorded peak
salinity values of 20 % at 15 km from Douala port in the
dry season and less than 12 % in the rainy season. Tides on
the Cameroon coast are of the semi-diurnal type. In general,
the amplitude varies between 0.3 and 3 m depending on the
location. Their effects are felt in the estuarine complexes.
The propagation of the waves and ebb tides are enormous,
but poorly known. Olivry (
1986
), Morin and Kuete (
1989
)
estimate them at 10
6
m
3
for the River Dibamba and
50 9 10
6
for the River Wouri, in nature are tidal currents
which are sometimes violent: 1-1.5 m/s for the flux and up
to 2.6 m/s for the reflux. The river flow disturbs this already
unstable system by submerging the estuarine complexes.
According to observations made by Chaubert and Garraud
(
1977
), sea swells are from the south to south-west sector
and of distant origin. Their peculiarity results from the
double obstacle constituted by Bioko Island and the wid-
ening of the continental shelf at the level of Rio-Del-Rey.
Sediment Dynamics
Sediments deposition leads to the creation of sandy offshore
bars whose origin is either marine (effect of the Benguela and
Gulf of Guinea currents) or volcanic (Mount Cameroon).
The progression of offshore bars and sandy spits parallel to
the coast (Souelaba Point), and of various points between
Idenau and Bamusso, is caused by: the predominance of the
Benguela current over that of the Gulf of Guinea which flows
from the west; the low amplitude of tides (2 m on the
average); the low charge of coarse detritus material in rivers
which flows through a woody hinterland; the build-up of
these coastal structures tends to regularize the coastal profile.
Erosion is significant along the volcanic coast of Cam-
eroon. A displacement of the coastline towards the continent
has been observed in the South West province. The estuaries
and mangroves are characterised by high turbidity which
extends right up to 30 km into the sea from Bakassi. This
phenomenon is also noticed in the estuaries of ''Bouches du
Cameroon''. The entire eastern part of Rio-Del-Rey basin is
blocked by accumulation of mud and fine sand advancing
southwards the River Meme. The evolution of the coast will
also depend on the quantity and rate of deposition of alluvial
material. Between River Akwayafe and Limbe, the offshore
currents can reverse direction. This phenomenon can either
lead to enlargement of the beaches or otherwise cause ero-
sion as in the case of Bamusso. The portion of the coast
between Kribi and Campo consists of crystalline rocks
which appear sometimes as isolated out crops in the sea.
This rocky portion is characterized by the absence of sig-
nificant deposits of sand and mud.
Climate and Oceanographic Conditions
The coastal climate in Cameroon, just as in the rest of the
Gulf of Guinea, is influenced by the meteorological equator,
which is the meeting point between the anticyclone of
Azores (North Atlantic) and that of Saint Helen (South
Atlantic). This climate results from the combined effect
of convergence of the tropical low-pressure zone and the
Data Collection Methods
Sea Turtles
From several monitoring of sea turtles species population in
the area, we made identification and description of nesting
sites and species according to standard KUDU-Program
protocols and the different nesting beaches patrolled by
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