Assessment of Flood Vulnerability Levels in the Lower Orashi River, Niger Delta Region, Nigeria

Abstract

Flooding is one of the most frequent and widespread of all environmental hazards and of various types and sizes. This study investigated the flood vulnerability levels in the lower Orashi River, Niger Delta Region, Nigeria. The study considered the landuse, soil texture, elevation, slope, stream power index (SPI), rainfall, drainage density and proximity to river channels as factors determining flood. The components of these factors were reclassified as lowly, moderately and highly vulnerable areas with assigned numbers 1, 2 and 3 respectively. All the maps were overlaid using the UNION module for the final flood vulnerability levels. Descriptive statistics and inferential statistics were used in the data analysis. Results showed that the very low flood vulnerability levels covered spatial extent of 244.4 sq km (7.31%), low flood vulnerability covered 901.31 sq km (26.95%), moderate flood vulnerability level 1240.18 sq km (37.08%), high flood vulnerability level 846.47 sq km (25.31%) and very high had 112.11 sq km (3.35%). It can be concluded that more than 65% of the entire lower Orashi River are highly and moderately vulnerable to flood. It is therefore recommended among others that periodic studies should be carried out in lower Orashi River to monitor the factors that can cause flood in the area.