Geography Reference
In-Depth Information
comprise series of map layers that are geographically referenced as well as
attributes that can be linked to such map layers by common identifier (Vine et
al., 1997). Thus, each of the map layers contain, in most cases, one central
geographic theme (thematic map) of the studied phenomenon. However, one
of the fundamental merits of a GIS is its ability to synchronize several map
layers for on-screen visual comparison and extraction of spatial relationships.
This chapter focuses on the formidability of using high resolution remote
sensing data and GIS techniques to assess and identify flood prone areas
(estimating population and infrastructure at risk) before occurrence in Lagos
State-large coastal city of Nigeria, and develop a more accurate, easily replica-
ted geo-based flood risk model for sustainable mitigation strategies and policy
plans.
2.
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HE
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TUDY
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REA
Administratively, Lagos is the smallest state in Nigeria, and on the other
hand, this territory contains the largest urban center in the country and one of
the largest coastal city in Africa. It is composed of 20 local government areas
(LGA) of which 16 forms the high density metropolitan region.
Geographically, the region is located at the south-western edge of Nigeria
in the West African sub-region between latitude 6°22'N to 6°41'N and longi-
tude 2°42'E to 4°21'E (Figure 1a). It covers an overall area extent of
approximately 3,829.84 km
2
with a perimeter of 454,328.4 meters, and water
bodies of about 1,700 km
2
.
With respect to the topographical settings, Lagos can be categorized into
three major geographic regions: a low-lying coastal zone along the Atlantic
Ocean, consisting of beaches; a broad inland depression and flat land (sloping
gently from the hinterland to the sea) surrounding the Lagoon and stretching
from the eastern boundary of the state to the western border of the country
(between Nigeria and Benin Republic), this zone comprises series of
marshlands and mangrove wetlands with elevation ranging from between 0
meter to 25 meters above sea level; three distinctive upland zones in the
northern part of the state with elevation of 70 meters above sea level, the
region's highest point is at Iroko and Olasore (Figure 1b). The Ogun River
constitute the primary surface water (river) that drains the region and it
empty's its water into the Lagos Lagoon. The state has a coastline of about
180 km.
