THE ENVIRONMENTAL IMPACT OF FLOODING ON TRANSPORTATION LANDUSE IN BENIN CITY, NIGERIA
ABSTRACT
Environmental problems of flooding on transportation land use manifest as a result of different land use activities of man to earn his living and his livelihood. Natural surfaces were replaced by more impermeable roads and concrete which have very low infiltration capacity, which have hydrological consequences of resulting into flooding problems in the Benin City metropolis. Data for this study were collected through the administration of 200 questionnaires, using the random sampling technique on respondents and through the physical survey of the study area. Simple percentages were used to analyze the data. Two hypotheses were formulated. The student ‘t’ test statistical method was used to test the hypotheses. Results from this study show that illegal disposal of refuse on drainage channels, high intensity of rainfall, the absence or infective drainage channels, poor construction of roads and building of houses on stream channels were identified as the causes of flooding on transportation land use in the study area. The study recommends that good road construction works, controlled dump sites, and timely response of the town planning authority to flooding menace should be carried out as a matter of urgency to tackle the environmental problems of flooding on transportation land use in benin city, nigeria.
1.0 INTRODUCTION
In general, the environment provides all life support system in the air, water, on land and in the forests (Glasson et al; 1999). However, the Nigeria environment generally, and Benin City in Edo State in particular, today presents a grim litany of woes across the length and breath of the country. Environmental problems therefore manifest as a result of different land use activities of man to earn his living and his livelihood. In the urban land use, deforestation has become a peculiar problem in Nigeria and Benin City in particular, which results from uncontrolled logging and tree felling for the purpose of urban development. In many parts of the Southern States of Nigeria, this goes with its loss of precious biological diversity. Afolabi (2005) noted that the environment is itself, the point in which one is found ata time, the surroundings, the more distant places, other earth components, conditions, prospects and problems which account for its flourishing or otherwise. Flooding can be described as high water stage in which water overflows its natural or artificial banks on the normally dry land, such as stream or river  inundating its adjacent lowlands.
In this regard, geophysical hazards can be wrought on civil artifacts, facilities, other aspects of human activities and occasionally loss of human lives may be incurred, (www.vision 2010.org, 2009). Â Adebayo (1987) recognized four major mechanisms for the increase in the flooding potentials of urban catchments. The first one is increasing the percentage of impervious surface that infiltrates in the ground and increase in the total volume of runoff. Secondly, paving, straightening or otherwise improving stream channels, all of which reduces the time lag between rainfall and channel runoff. Thirdly, landscaping and subdivision of land into building sites, a process that shortens the distance over which the water flows before reaching drainage way and hence reduces the time lag between rainfall and channel runoff. Lastly, filling in and human settlement on flood plains, which reduces the space available for storing flood waters. African Research Review Vol. 4(1) January, 2010. Pp. 390-400
The phenomenon of flood hazards, according to Ward (1978), comprises several aspects including structural damage, loss of lives and properties, disruption of socio-economic activities including transport, communication and the destruction of agricultural land. According to Ayoade (1979), floods are natural phenomena rather than natural disasters. They, like drought, form part of the normally occurring range of stream flow conditions. Flood disasters are man-made as they occur when and where man puts himself at risk by developing and occupying floodable areas, there by causing damage, congestion and hold ups to the transportation networks in the area. Man, therefore, develops and occupies flood plains, at risk of flooding, out of ignorance or for economic reasons.
The basic cause of urban flooding is man’s modification of the basin network and channels characteristics during the process of settlement on the particular flood plain (Adeleke, 1978). Natural surfaces are replaced by more impermeable roads and concrete which have very low infiltration capacity. The hydrological consequences of this is that water which should normally infiltrate into the ground or be intercepted by vegetation and then delay for some time before running, would be immediately available for runoff. This considerably decreases the lag time between rainfall and storm water and increase the runoff with concomitant increase in peak discharge and total volume of runoff (Adeleke, 1978).
