Study of the nature of urban flood in Benin City, Edo State; Nigeria

Abstract

The Niger Delta region of Nigeria is mostly flat, low lying, swampy basin resulting in severe regular flooding which has led to a limited land area available for human habitat. Approximately 7000km2 of land cannot be used owing to flooding. This study assessed the nature of urban flood in Benin City, Edo State; Nigeria. Thirty-five streets and roads were identified as areas prone to regular flooding and twelve of these streets including Uselu – Ugbowo Road, New Lagos- Uselu Road, Sakpoba – Oka Road, Plymouth – Oliha Road, Uwasota-Ogida road, Ogida-textile-Urubi Road, Television Road, Erhummunse Road, Upper Mission Road, Wire road, Forestry Road were identified as the most critical. The types of flood experienced are flash flood and flood pondages. 52% of the total area is inundated for more than two hours during flood episodes with an average water height of 1m. Laboratory analyses of soil samples collected from the twelve streets and roads show a greater clay fraction than any other soil fraction with clay as 52.23%, sand 28% and silt 19%. Permeability is low with a value of 1.17 x 10-3cm/sec. Bulk density ranged from 1.9gcm3 at Forestry road to 3.12gcm3 at Sakpoba – Okah road. The degree of variability between and within locations of the factors of flooding in Benin City showed that there is no significant variation between the locations of the flooded area in Benin City at P>0.05 level of significance. However, there was significant difference in the variation among the parameters with Clay varying significantly at P>0.05 level of significance from all others, while silt and sand are not different from each other as similarities exist between the other parameters. By this implication, Clay is the dominant
soil type of the study area. In consonance with dominance of the clay soil in the study area, bulk density is high. It is therefore concluded that the soil condition is a major determinant of flooding in Benin City. The flooding problems has resulted in traffic congestion and lost of man-hours giving rise to lopsided concentration of vehicular traffic.