Mitigating Perennial Flooding in Victoria Island and Lekki by Christian OkworiFlooding problems are not peculiar to Nigeria or developing countries alone, even the Western worlds suffer it too but such is limited to the level of flooding that exceed economically sustainable modern technologies in flood control methods. Contrary to the pedestrian claims that the new Eko Atlantic City in Victoria Island seating on the former Bar Beach and estates of its likes are the cause of the floodings, the crisis of flooding is almost as old as these areas but worsened by environmental changes occasioned by global warming and some human errors. The Eko Atlantic City if properly sandfilled and prepared could even become a part of the solution to flooding problems.

The problem with Victoria Island and most of Lekki is that the challenges of perennial flooding were not envisaged or figured out during their creation just like we don’t build earthquake and bomb resistant buildings in this part of the world just because we done yet experience earth vibrations to such scales aside the obvious techno-economic lapses of not raising the post caking sandfill much higher above sea level and regulating subsequent sandfilling and land extension activities to comply with those minimum heights above sea level(ASL) to the equivalents of mainlands like Oshodi or Ebute Meta areas. The Ocean as the ultimate sink where all drainage channels get emptied has to be the lowest land relative to inhabited surfaces. As such, flooding is inevitable in a land not fairly higher than the sea level. Even the city of New Orleans in the United States and places like Netherlands are below sea levels but have less rainfalls compared to Lagos but they too can only manage flood up to certain capacity of rainfalls.

This is based on the natural law that water must flow on gravitational influence from higher to lower topographies. The issues at hand now are basically that Victoria Island and Lekki areas are at the same or marginal heights with the Atlantic Ocean and Lagoons as such water flows from these areas to the ocean and lagoon are very limited even with the best of drainage designs and once the rainfall becomes slightly average, flooding occurs not to mention heavy rainfalls. Hence, we are left to seek ways out of the problem at hand, and not to magnify them by accusations and shifting of blames as usual. Here are some suggestions.

1. Proper even sandfilling of new Island estates and reclaimed marshlands to certain minimum post caking regulatory heights above sea level as a proactive measure. The ongoing Orange Island being created in the Lekki Lagoon close to Admiralty Way and the planned sandfilling of former Makoko and Otodo Gbame, and the ongoing land reclamation at Oworonshoki Lagoon corridor among others must be made to adhere to those standards. Though this will imply higher cost of land and properties in these estates but it will be worth it in the long run. We must not let greedy property developers mortgage the future of generations to come in the eyes of looming natural disasters. Nothing wrong with sandfilling for housing but greed and inadequate planning, Environmental Impact Analysis(EIA), lack of due diligence in techno-economic cum risk simulations, technically deficient regulatory framework, neglect of concerned core experts, and poor disaster management cultures.

2. Expansion of existing drainage systems with respect to maximum flow gradient depths. Most of the canals in Victoria Island and most of the street drainages are not wide enough but fortunately some have been optimally corrected at Akin Adesola, some affluent Ikoyi streets, and a few areas though more than 90% of the street drainages are horrible hence they keep dissolving the roads while causing flooding at the same time. The expansion needs to be wholistically done though in phases as they all link up.

3. Removal of obstructions on the drainages. Majority of the major canals and street drainage channels in Victoria Island have been virtually blocked by underground telecommunications and power cables in the most bizarre of manners. They have to be aesthetically surface re-routed whenever such trenching encounter drainage paths. Aside that, a good number of the drainages are overgrown with weeds and stagnated by sewage discharges from office and residential buildings which have turned the waters in the drains into viscous colloidal solutions making them more resistant to follow worsened by the paucity of gradient.

4. Removal of structures obstructing water courses and virtual drainage paths. Quite a number of high profile buildings and landmark structures are either partially or fully thwarting the path of drainage flow. The canals and drainages are often narrowed to avoid or give way to the structures. Obvious some of these structures pre-exist the drainage systems but what has to be done has to be done.

5. Centralized sewage treatment and discharge system. The current practice in which offices and companies in Lekki and Victoria Island treat and discharge sewage at night into the street drainages are contributing to flooding because these discharge are heavy and viscous thus holding water from flowing and percolating as well as depositing silts on them. Such sewers should be collected by trucks and taken to convenient locations in the mainlands for recycling into various useful products.

6. Creation of artificial gorges or predischarge underground concrete lined cisterns at certain cardinal points for collection and onward transfer by both natural and forced methods into the oceans and lagoons in order to quickly evacuate street drains. These may be a bit capital intensive but worth it.

7. New structures and building premises should be made to raise their rafts and sandfills to very good heights above sea level in order to minimize the overflow of canals and drainages into their premises.

8. Regular and prompt de-silting of canals and drainages. Also the use of thick concrete slabs to cover street drainages should be discouraged as they often sink under the weight of parked cars to block the drainages aside narrowing flow cross sections.

9. Dredging of neighbouring lagoons. The dredging of neighbouring lagoons will help in a good extent in improving drainage influx from the sandfill estates.

10. Residents and truck pushing waste collectors must adopt responsible attitudes in waste disposal. It not uncommon to occasionally sight househelps dumping garbages in canals and lagoon fronts. Accumulate plastic, paper, woods, and other solid wastes do block drainages in most of Lagos. This requires both government and private efforts.

11.Engineers and concerned experts both in private and organised capacities like The Nigeria Society of Engineers, private engineering consultants, and COREN in these areas should be carried along in drainage construction and be empowered to report wrong practices by construction contractors and government officials.

Engr. Christian Okwori is the Technical Secretary of The Nigeria Society of Engineers, Victoria Island Branch.

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