Environmental Engineering Reference
In-Depth Information
Cross
River
Fig. 4
Satellite imagery showing Cross River estuary and adjoining river systems
Vegetation
drainage system. Structurally, the Cross River plain is
underlain by the Ogoja syncline and the Abakaliki uplift
wherein lie thick Cretaceous sandstones, marine shales and
limestones of the Asu River and the Cross River group.
The Cross River estuary is fed by several smaller rivers
which take their sources from the Oban hills in the north.
The river flows through swampy rainforest with numerous
creeks and forms an inland delta near its confluence with the
Calabar River about 20 km wide and 50 km long between the
cities of Oron on the west bank and Calabar on the east bank.
The delta empties into a broad estuary which it shares with a
few smaller rivers. At its mouth in the Atlantic Ocean, the
estuary is 24 km wide. The eastern side of the estuary is in
the neighbouring country of Cameroun. The Cross River
delta has been built out onto the cT shelf with deep sub-
marine canyons (e.g. the Calabar Canyon). The canyons
have been incised, with deep sea fans building out onto the
ocean floor and providing excellent petroleum traps.
The Cross River estuary is characterized by a broad belt of
mangrove swamps fronted by Nympa palms. Mangrove and
swamp ecosystems dominate the vegetation type. The man-
grove ecosystem is dominated by Rhizophora species, while
the Nympa palms and swamp vegetation are also abundant.
Along the Calabar estuary, Nympa palms are rapidly replac-
ing the mangrove vegetation (Isebor and Awosika
1993
).
Socio-Economic Activities and Infrastructure
Socio-economic activities in this area involve fishing,
tourism and subsistence agriculture. Commercial activities
include ship building, subsistence and large-scale agricul-
ture and lumbering. Considerable activities in support of the
oil and gas industry are also carried out within the area. The
population of the lower Cross River traditionally uses water
transport and Calabar has long had a major seaport, located
on the Calabar River about 10 km from its confluence with
the Cross River and about 55 km from the sea. The estuary
serves as a major navigational way to Calabar Port. The
physical modification of the estuaries result from sedi-
mentation processes involving tidal currents, storm surge,
exploration and exploitation of oil and gas.
Tidal Regime
The estuary has a tidal range of between 2.1 and 3.0 m.
Tides are semi-diurnal with two inequalities. This estuary
had the largest tidal range in the Gulf of Guinea reaching a
maximum of 3.5 m in Calabar port.
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