Estuarine and Ocean Circulation Dynamics in the Niger Delta, Nigeria: Implications for Oil Spill and Pollution Management - The Land/Ocean Interactions in the Coastal Zone of West and Central Africa - page 77

Fig. 2 Characteristics of
oceanographic parameters
offshore Nigeria (After Awosika
et al. 2000 )

Prevailing southwesterly wind direction

Prevailing W-E Guinea current
Down canyon current

Prevailing longshore current direction

Prevailing southwesterly wave approach

Harbour structures

Waves Longshore Currents

Waves affecting the Niger Delta are wind-generated and
approach the coastline from a south-westerly direction. The
wind systems consist of the onshore south westerlies and
offshore north easterlies. Swells generally approach the
coastline from the south/south-westerly direction, with
oblique angles of approach of not less than 3 and not more
than 15.

The dominant longshore drift cells responsible for nearshore
circulation and transport in the nearshore zone (Fig. 2 )
consist of the north-westerly longshore drift of the western
Niger Delta and the west-to-east longshore drift (Awosika
et al. 1994 , 1996 ). Between Akassa point and the Benin
River, the Niger delta runs NW-SE. The coastal configu-
ration along this part of the Niger results in the south-
westerly waves breaking obliquely to the coast with the
breaking waves opening to the north-west. This generates a
longshore drift in a north-westerly direction which is fed by
successive distributaries of the Niger delta between Akassa
Point and Benin River (Fig. 2 ). East of Akassa is the east-
to-west littoral longshore currents. This longshore drift cell
continues eastwards to the Calabar estuary (Fig. 2 ).

Tides

Tides within the Niger Delta are semi-diurnal with two
inequalities. Swells produced by the south-westerly winds
approach the Niger Delta coast in a south-westerly direction
(Fig. 2 ). Elevated water, close to the shore during the two
daily high tides, generally assists the waves to progress
further inshore. Stronger tidal currents, exceeding 5 m/sec
at the inlet/ocean intersection, have been found to occur
during ebb tides. Flood and ebb streams usually run for
about 3 h after High and Low water, respectively. The
active distributaries are tidally dominated and often display
typical bell-shaped river mouths.

Ocean Currents

Ocean currents off the Niger Delta consist of the Guinea
current, which is an extension of the North Equatorial
Counter current said to attain speed of 0.3 m/sec with some
reversals

(Fig. 3 ). The Guinea current runs above an