APPLICATION OF GEOINFORMATICS TECHNIQUES IN CONTROLLING FLOODING IN VULNERABLE ROADS AND BUILDINGS IN NIGERIA. A RESEARCH PROJECT MATERIAL ON QUANTITY AND SURVEYING
Background to the Study
The acronym GIS stands for geographic information system, it is a system which allows a capture, updating and displaying of a number of previously unconnected dataset bringing them into a common reference system for spatial analysis from which relationship can be identified and decisions made (Sowton 1991).
Floods are probably the most recurring, widespread, disastrous and frequent natural hazards of the world. India is one of the worst flood-affected countries, being second in the world after Bangladesh and accounts for one fifth of global death count due to floods. Nigeria is not an exception and indeed the study area as series of flooding have affected inhabitants and disrupted socioeconomic activities. Flood management and control are necessary not only because floods impose a curse on the society, but the optimal exploitation of the land and proper management and control of water resources are of vital importance for bringing prosperity in the predominantly agricultural based economy of this diversely populated country. This cannot become technically feasible without effective flood hazard maps (Pradan, 2004)
Flood hazard mapping and flood inundation modeling are the vital components in flood mitigation measures and land use planning. Advances in geospatial technologies (GPS, Remote sensing and GIS) has enabled the acquisition of data and analysis of the river basin for flood mitigation projects (either structural or non-structural) in a faster and more accurate manner. GIS facilitates integration of spatial and non-spatial geographical data such as rainfall and stream flows. Other information such as flood maps, infrastructures and land use, social and economic information can be inventorized for future use. Flood maps prepared using satellite images of real flood events and information from the ground are useful for flood damage assessment, future flood mitigation planning. Flood vulnerability maps produced using GIS enabled effective tools for land use planning, flood management and development control. Therefore, an attempt has been made to apply modern techniques like Geographical Information System (GIS) for the management of flood in Port Harcourt, the study area, as it has been proved that the use of Geoinformatics to manage the databases, maps, and photos improves the ease of the analysis (Wisner et al., 2004; Noson, 2002).
1.2 Statement of Problem
Floods are among the most destructive acts of nature. World-wide, flood damages to agriculture, houses and public utilities amount to billions of dollars each year in addition to the loss of precious human and cattle lives (R.K.Khanna, 1989). In majority of cases, ‘flooding’ is caused by a river over-spilling its banks. This can be due to excessive precipitation, combined with inadequate channel capacity. Over-spilling can also occur due to obstruction in or aggradation of the river bed.
Flooding can also result from inadequate water way at rail and road crossings, or when there are encroachments in the flood plain. Flooding can also occur at confluences of streams when the main river is in high stage and backs up into the tributaries and areas there about.