Floodplain Determination Using Geographical Information System (GIS) (A Case Study of Ogunpa River in Ibadan Oyo State, Nigeria) (Published)
Flood causes loss of life, destruction of public and private properties and disrupts the normal cultivating cycle. Floodplains are important land features that are highly discriminated from the neighboring uplands in terms of their hydrological and geomorphologic processes. Ogunpa area which is liable to flood has witnessed an encroachment by urban settlements within its precinct. This has been accompanied by inundation which is retained on the land as a result of the impervious nature it has turned into. The aim of this project is to produce a floodplain map within River Ogunpa catchment. The geometric data for the river and flood plain were extracted from the Digital Elevation Model (DEM) using Geographic Information System. The Study analyzed the morphometric parameters of Ogunpa catchment area located in four local government of Ibadan which are Ibadan north local government, Ibadan south local government, Ibadan north east local government, Ibadan south north local government, determining areas which are prone to flooding. Data used were generated from topographical map of Ibadan scale 1:25,000 A triangular irregular network (TIN) was created to satisfy the Delaunay triangle criterion, which ensures that no vertex lies within the interior of any of the triangles in the network. Result obtained indicated that Ogunpa River exhibits high spatial variation in their properties. Ogunpa’s water profile increases as the water flows downstream. The result revealed the flow direction of flood water in the area. The water profile increases as one move downstream along the length of the river. It was observed that most of the area was under medium hazard zone. The river has high tendency to flood due to its flat or low-lying terrain. Little or no provision has been made for surface drainage to aggravate the situation. Municipal waste refuse and eroded soil sediments contributes to the lower course stagnation of the river, resulting in poor drainage and tendency for flooding, the existing drainage basin are likely to induce high magnitude of flooding
Keywords: Digital elevation model, Flood plain, Flooding, Triangular irregular network