Floodplain Mapping and Risks Assessment of the Orashi River Using Remote Sensing and GIS in the Niger Delta Region, Nigeria

Abstract

Residents along the shoreline of the Orashi River have yearly been displaced and recorded loss of lives,farmland,and infrastructures. The Government’s approach has been the provision of relief materials to the victims instead of implementing adequate control measures.This research employs Shuttle Radar Topographic Mission and Google Earth imagery in developing a 3D floodplain map using ArcGIS software. The result indicates the drainage system in the study area is dendritic with catchment of 79 subbasins and 76 pour point implying the area is floodplain .Incorporating the 3D slope which reveals that> 8 and <8 makes up 1.15% and 98.85% of the study area respectively confirms the area is a floodplain. Aspect indicate west-facing slope are dark blue, 3D hillshade indicate yellow is very low area and the high area is pink and also the buffer analysis result reveals waterbodies reflecting blue with an estimated area of 1.88 km2,yellow indicate 0.79 km2 of the shoreline, red indicate 0.81 km2 of the minor floodplain and pink contain 0.82 km2 with the length of 32.82 km. The result from google earth image in 2007 indicate absent of settlement, 2013 indicate minimal settlement and 2020 indicate major settlement in the study area when correlated with 3D Floodplain mapping before and during the flood in other to analyze and manage flooding for further purpose and the majority of the area are under seize with flood like in 2020. Therefore, Remote Sensing and GIS techniques are useful for Floodplain mapping, risk analysis for control measures for better flood management.