Mitigating the city floods

The recent prediction by NIMET of the concentration of the annual rainfall volume in a very short period when the heavy rainfall starts should be a matter of serious concern. The manifestation of the global Climate Change this year is the very late arrival of the effective rainy season. The danger is not only on […]

The recent prediction by NIMET of the concentration of the annual rainfall volume in a very short period when the heavy rainfall starts should be a matter of serious concern. The manifestation of the global Climate Change this year is the very late arrival of the effective rainy season. The danger is not only on the imminent short planting season which has already started manifesting across the region, but also that of possible widespread floods that have the tendency of endangering lives and property across the country.
Previous records indicated the peak raining season occur within the last week of July and the first week of August. This is the period we are at the moment. Within Abuja and environs, this particular period were always marked by the floods and the notorious incidents of building collapse. For the fact that this year, the rains seem to be insufficient from the onset, does not betray the known trend of the exact period of the commencement of the floods, as we have started witnessing the incident with the Wuse City Park flood of last week. Thus, authorities must not be complacent on measures against the floods. Weather phenomenon which is largely unpredictable can also be highly destructive at a time it is least expected.
Natural disaster can never be prevented, but it is possible for it to be substantially mitigated, with a very careful environmental planning and development. Such considerations were embedded in the plan for Abuja City development. The Garden City Concept was very particular in the maintenance of ecological balance and the respect for the natural landforms with the view to the prevention and mitigation of possible flood occurrence. The plan earmarked 33 percent of the city land use to be reserved for green developments only. These include green stretches along stream valleys, river beds, flood plains, hilly patches and some incidental open spaces.
The removal of natural ground cover and creation of essentially impervious areas increases volume and rate of storm water runoff from urbanizing areas. It was originally expected that Abuja’s development would cause increased stream flows which could lead to local flooding and erosion, if adequate design provisions in the city plan are not made and subsequently managed after implementation. The entire runoff and drainage pattern would be prone to the menace of flashy and localized floods of short duration. One hundred years of flood regime of the streams and valleys on site earmarked for the city was preserved by the International Plan Associates (IPA) prior to the original layout plan for the city. Accordingly, wherever valley occurs such as in the Central Business District they are recommended to be left in their original natural state. Additionally, reasonable buffers between the streams and built up areas are maintained.
Meanwhile, despite the comprehensive plan, the city is not free from localized floods in notable spots whenever heavy storm is recorded. Our major challenge is the violation of the city land use plan, consequent upon indiscipline and greed for material acquisition by those saddled with the responsibility of the city lands allocations. Rules governing land allocation and development guidelines were unceremoniously desecrated, such that allocations for various land uses were made on those areas preserved for green development, around the stream valleys. They are areas serving as tributaries for onward transfer of the collected storm water to be drained out of the territory by the network of the perennial rivers. These are areas most susceptible to the floods, thus, endangering people’s lives and property.
The experience of year 2013 widespread floods should galvanize us on studies of flood regimes in our environments, and subsequently implementing the measures for floods mitigations. The Global Climate Change has proved to be notorious with very drastic reduction of periodic weather cycles, such as widespread floods occurrences. The 100 years flood regime considered by our city planners could recur this time within 10 years or less, as witnessed in many areas here and around the world. We might wake up tomorrow to experience the repeat of the 2013 devastating floods, such that resulted in the Abuja-Lokoja road blockade. A situation never witnessed in living memory, now has the tendency of recurring, just two years after.
Urban floods can never be stopped either by the use of dams or levees. As stated by Gilbert White a renowned environmentalist, “Floods are acts of God, but floods losses are largely acts of man”. The safest approach is to stop obstructing the floods path. It must be allowed to be drained as fast as it comes. Containing floods is not on large engineering solutions, but more on good land-use planning and stewardship. Our planning must accommodate the floods, and be centered on how to get the water moving through and not create blockages during flood events.