Quantitative Assessment of Open Drainage and Storm Water Runoff Capacity in Nigeria: Consequences and Way Forward

It is undeniable that many existing traditional urban drainage systems in Nigeria are not adequate to accommodate the volume of storm water runoff that is being generated from the present rainfall pattern. Global rainfall pattern has being altered severely by climate changing situation which has resulted to intense and unpredictable rainfall. Urbanization activities, increased impervious surfaces and less vegetative natural environment remains a contributing factor. This study is focused at reviewing the challenges of open drainage, storm water runoff consequences and way forward in Nigeria urban area. From investigation, the urban physical environment in Nigeria is deteriorating and degrading with accumulated problems generating from poor and inadequate drainage system and accelerated urban storm runoff. The problem ranges from flooding situations, portholes with stagnant water splash, pollution of surface water, ground water quantity recharge among others. Flooding problem is always accompanied with destruction of infrastructures that support man's existence and loss of lives. Sustainable Drainage System (SuDS) is a shift from the usual piped drainage system to more natural way of treating storm water. This system of drainage is regarded as another better option for managing storm water. SuDS work with nature to manage rainfall close to where it falls and also with designed techniques to convey storm runoff water very slowly to a water course. It enhances surface water quality and quantity, reduce the risk of runoff in the environment, ameliorate flood challenges with the introduction of green environment and green roofing. This study therefore recommends SuDS source control methods in line with the amendment of the existing drainage as a support in major cities facing storm water runoff challenges.