Hydraulic Relationships of the Ikpoba River for Flood Studies

Abstract

Flooding is a temporary condition of partial or complete inundation of normally dry areas of overflow of inland or tidal waters or from extreme and rapid accumulation of runoff. Flooding phenomenon is considered the world worst global hazard in terms of magnitude, occurrence and geographical spread, loss of life and property, displacement of people and socio-economic activities. In the tropical and sub-tropical regions, severe flooding hazards resulting from heavy thunderstorms, torrential downpours, hurricanes and tidal waves are yearly occurrences. Flood disasters are said to account for one-third of all natural catastrophes throughout the world by number and economic losses and are responsible for more than half of the facility damage (Askew, 1999).

In Nigeria, many urban floods occur because of excessive extreme rainfalls improper land use and poor drainages. It has been estimated that more than seven hundred thousand hectares of useful land for agricultural and residential purposes are either lost or rendered useless due to annual floods (David and Aggrawal 2008). 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 for residence. Benin City experiences flash Flood and Flood pondages. Areas are inundated for more than two hours during flood episodes with an average water height of one meter (Ogbonna, et al 2011). As a result of flood events, every year government spends huge sums of money on compensation for flood victims, yet, the problems are unabated. Decision makers need supporting tools such as knowledge of extreme flood magnitudes and probability of re-occurrence, flood stages and river discharge relationships to enable decisions on a particular line of action which would be most adequate in mitigating against flood

This study seeks to derive hydraulic relationships for the Ikpoba River which can serve as decision support tools that can be used in evaluating flood damages in suburban-areas of  Benin-city metropolis.

The specific objectives are to:

1. i. Determine the exceedance frequency discharge relationship for the Ikpoba River.
2. ii. Establish depths for longitudinal and cross sectional profiles of the Ikpoba River
3. iii. Derive the stage discharge relationship of the Ikpoba River