Geography Reference
In-Depth Information
2013b). Data from such system is high resolution images specifically adopted
in this chapter for geovisualization and database creation.
The most recent Google earth engine (Google earth pro version 7.1.322)
was used in this chapter because it captures current urban footprints that have
taken place in the study region. Other vector data were downloaded from map
library website such as the territorial boundary of Lagos State and the local
administrative boundaries (polygons).
4.
M
ETHODOLOGY
Various GIS spatial analysis, extraction and image classification
techniques were conducted to develop a flood risk modeling methodology that
can easily be replicated (Figure 5). This was achieved majorly with the aid of
ESRI ArcGIS version 10.1 and Google earth pro version 7.1.322 softwares.
The primary objectives of this chapter are to develop a comprehensive
GIS driven methodology for flood risk analysis in a littoral mega city and to
demonstrate the capability of using GIS technology to create a geodatabase
system for flood risk management that contains spatially referenced informa-
tion as the flood prone areas and their various risk magnitudes, estimated
population and infrastructures at risk.
4.1. Extraction, Vectorization and Reclassification of Elevation
Data
Elevation data is one of the principal datasets needed for GIS-based flood
risk modeling. It is particularly useful for the generation of potential inunda-
tion extent and classification of risk zones.
It has been used by numerous researchers (Islam et al., 2001; Taubenbock
et al., 2011; Nkeki et al., 2013; Townsend and Walsh, 1998; Sobowale and
Oyedepo, 2013) to model flood risk and produce maps of potential flood prone
areas. The SRTM high resolution DEM which has been spatially corrected and
preprocessed to fill in the voids in the data were entered into ArcMap-ArcInfo
environment for further processing.
Using the DEM assembly tool extension in the software, the series of 1-
degree elevation data tiles were merged and resampled to create a composite
grid hydro DEM.
