Environmental Engineering Reference
In-Depth Information
Hence, estuaries are often characterized by fine sediment
deposition (sand and mud) and include extensive intertidal
areas (saltmarshes, mudflats, and sand flats), and semidi-
urnal or diurnal tidal regimes (Plate
1
). Pritchard (
1967
)
proposed four classes of estuaries based on their geomor-
phological status, while Hume and Herdendorf (
1988
)
developed a 16-type classification scheme based on the
geomorphology and oceanographic characteristics of the
estuary, tides, and the catchment hydrology. The Defra
(
2002
) estuaries classification was based on sediment ori-
gins, and Hayes (
1975
) classified estuaries of tidal ranges of
less than 2 m, between 2 and 4 m, and above 4 m into
microtidal, mesotidal and macrotidal estuaries, respectively.
Dyer (
1997
) pointed out that when the ratio between river
flow and tidal flow is equal to or greater than one, the
estuary is highly stratified, at about 0.25 is partially mixed,
and well mixed at values less than 0.1, based on the salinity
structure involving the mixing process between fresh and
salt water (Seminara et al.
2001
). Dilution processes within
estuaries take place at different mixing levels due to many
forcing mechanism like tides, tidal currents, and wave-
induced motion. At the mixing point, a salinity gradient is
formed and the occurrence of internal waves on the inter-
face generates a density flow gradient which tends to
increase flood currents in the deepest parts and decrease
flow near the surface and the shallow cross-sectional area of
the river channel.
Distortions to the dynamic 'steady state' of an estuary
may therefore severely alter the geomorphic and geological
characteristics and resilient behavior of the system, with the
possibility of total modification of its morphology or losing
the entire ecosystem (Pethick
1994
; French
2006
). Hence,
this study examines the shoreline morphology of the Niger
Delta shoreline and major estuaries for better understanding
of the natural forcing within the estuary systems and their
potential for ecotourism development planning and man-
agement beyond the twenty-first century.
Ecotourism entails the ability of human beings to utilize
the natural resources for the promotion of tourism without
being destructive to the ecosystem. It therefore entails
benefiting from the enormous provision of the numerable
natural resource environment without destroying the live-
lihood of indigenous communities. It is therefore beneficial
not only as a means of conserving the estuary-rich biodi-
versity and extensive ecosystem environment but also to the
economy of the host community (Moelry
1990
; Mowforth
and Munt
2009
). It is a promising means of advancing
social, economic, and environmental objectives of sustain-
able development of the numerable natural resource.
Box 1: Overview of Estuary and Ecotourism
• Estuaries are semi-enclosed coastal bodies of water
with free connection to the open sea.
• Estuaries are commonly found on the numerous
sedimentary coasts, providing numerous goods and
services.
• Estuaries classification can be based on geomor-
phological and oceanographic characteristics, sed-
iment deposition, and tidal regimes and dilution
processes.
• Ecotourism entails the ability of human beings to
utilize the natural resources for the promotion of
tourism without being destructive to the ecosystem.
• There is need to examine the Niger Delta shoreline
morphology
and
their
potential
for
ecotourism
development.
Niger Delta Shoreline Morphology System
The Nigeria coastline region of length approximately
859 km consists of a narrow low-lying topography coastal
strip of land and stretches inland for a distance of about
15 km in Lagos to about 150 km in the Niger Delta and
about 25 km east of the Niger Delta. This coastline lies
within Latitude 410
0
N and 620
0
N and Longitude 245
0
and
832
0
in the eastern section (Fig.
1
). Tides along the entire
Nigerian coast are semidiurnal and from a southwesterly
direction with two inequalities. The tidal range increases
progressively eastwards from 1 m at Lagos to about 3 m at
the Calabar estuary. Though the tidal range is relatively
small, the spring tidal range reaches on average 1.8 m
across the coastline (Abam
1999
). This intense tidal activity
can be destructive and significantly modify the coastline
morphology characteristics, as evident along the Mahin
coast during a spring tidal range of 1.5 m (Nwilo and On-
uoha
1993
).
Sediments near the shore of the coastline area are com-
posed of coarse to fine sand except off the Mahin mud coast,
which is void of sand but with sediment grades varying
from fine sand to silt; Nigerian coast are semidiurnal and
from a southwesterly direction with two inequalities to mud
at the outer shelf, with finer-grained sand beaches occurring
along the flanks of the Niger Delta (Plate
2
). The coastal
region is divided into four main geomorphic zones (from
east to west) namely the stranded coast/estuary complex, the
Niger Delta, the transgressive Mahin mud coast, and the
barrier beach lagoon coast complex (Awosika et al.
2000
).
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