The Effect of Urbanization on Channel Adjustment and Flood Vulnerability of Woji Basin, River State, Nigeria.

Abstract

The impact of urbanization on the hydrology and sediment supply of streams is a major problem causing the flooding of flood plains and its inhabitants. This study examines the impact of urbanization on the channel adjustment of the woji creek and flood vulnerability of the catchment area. The study used both primary and secondary data in its investigation. The primary data were obtained through direct field measurement of the hydro-geomorphic parameters of channel depth, width, discharge, velocity and channel morphology while data for sediment yield and infiltration capacity were obtain through laboratory analysis of samples collected from the stream channel. In the same vein, data for urbanization index was obtained by measuring the distance of urban infrastructure close to the channel. Findings showed that a unit decrease in distance to the channel resulting from an urban infrastructure will consequently lead to a increase of 0.555m/s in the velocity of flow;  0.458cumecs in discharge; 0.520m in width of the channel; 0.489m in depth of the channel;  0.466m in channel morphology and 0.504m/s in infiltration capacity of the Woji River. However, it was only sediment yield that increases at a unit of 0.372ppm for every unit increase in distance of any urban infrastructure which is a function of flood vulnerability. This shows that urbanization influence channel adjustment and exposes the catchment area to flood risk. Policies aimed at integrating flood management, preservation of the stream channel in addition to urban growth control along the Woji creek in Port Harcourt is advocated.

Keyword; sediment load, runoff, urbanization, flood vulnerability, channel adjustment.