Flood Hazard Assessment along Delta State River Niger Basin using Remote Sensing and GIS

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Hazard, Flood Disasters, GIS, SRTM, MODIS, Vulnerability
Ahuchaogu Udo. E.; Ojinnaka O. C.; Njoku R. E.; Baywood C. N.
Adequate geographic information on vulnerability of facilities and people to hazards is required to be able to prepare for disasters. Flood hazard maps provide knowledge of the areas that are likely to be affected during flood event. Delta state is one of the states in Nigeria that is annually affected by flood t due to its location along the coast of Atlantic Ocean. In the past, the state government has spent millions of naira trying to reduce the damage resulting from flood disaster in the state but the damage trend keeps maintaining a rising curve. With the current situation, it has become apparent that the existing measures are not capable of handing the problem therefore the need to adopt a more promising technology. This study exploits Remote sensing (RS) and geographic information system (GIS) techniques in flood management with the goal of mapping areas vulnerable to flood hazard in delta state. It identifies spatial variations in flood hazard potentials in Delta state with a view of fostering the best approach for flood management.. Flood generating factors, i.e. elevation, proximity to the river, population density, drainage density, and) land use were combined to delineate flood hazard zones using a multi-criteria evaluation technique in a GIS environment. Each of these factors was reclassified into four levels of hazard categories namely very high hazard, high hazard low hazard and no hazard through ranking method and these reclassified factors were then overlaid using addition operator. Data used are SRTM of 1 arc seconds (30m) resolution, Landsat satellite Imagery with resolution 30m, Administrative map of the study area, Moderate resolution satellite imagery (MODIS) captured before and during 2012 flood disaster in Nigeria and the 2016 breakdown population figure of the state obtained from National Bureau of Statistics. The results obtained shows that, areas lying close to Atlantic Ocean and river Niger are most vulnerable to flood hazards with the hazard intensity decreasing towards the Northern part of the state. The very highly hazard places covered 4143.455(24%) square kilometers, High hazard areas covered11000.874(63%) square kilometers, lowly hazard areas covered 1323.75(7%), square kilometers, and no hazard region covered an area of 1061.927(6%) square kilometers. The hazard map produced was validated using the 2012 flood extent map of study area. Result revealed that areas inundated are part of the places identified as very high and high hazard zones.