Monday 17 September 2012

Tackling ocean surge at Kuramo Beach

Many Faces Of Kuramo After It Fell
The Nigerian coastline borders 853km of the Atlantic Ocean and is interrupted by a series of estuarine entries to the sea. The Lagos landmass is significantly covered by a meandering network of large expanse of wetlands, adjoining creeks and lagoons.
The Kuramo lagoon is one of the 10 lagoons in Lagos. The formation of these lagoons over geological time is evidently the result of movement of sand along the West African coast in a west-east direction by long shore current/drift and sediment movement.
The dominant current (Guinea current) operating in the Lagos coastline area runs from the west to the east and hits the shoreline at approximately 43?. This is what created the lagoons in geological past and anywhere else in West Africa where the coast aligns likewise.
The Lagos harbour, which is part of the Lagos lagoon, is the only opening for nine of the coastal or marginal lagoons to the sea. There is no natural rocky shore in Nigeria; however, at the mouth of the Lagos harbour, there exists a rocky outcrop (stone moles) in the form of harbour breakwaters. These moles were chiefly constructed (i.e. the east, west and training moles) between 1901 and 1930 to protect the Lagos harbour from siltation (natural sediment flow), hence allowing the easy passage of ocean-going vessels to berth in the Lagos harbour, ports, wharfs and other terminals inland.
These constructions were more of an economic consideration than an ecological one.
In addition and more recently is the commencement of the construction of the Eko Atlantic City project. This is a large construction work in a systemic and natural current regulating coastline. There is also the case of “renovation” of the stone moles at the harbour entrance to make them more “effective.”
The issue, over the years, has been the large-scale habitat modification resulting from the construction of the moles, which has obstructed the natural sediment regime and flow. Large-scale dredging and sand mining in the Lagos harbour/Bar Beach area has also gone on for years. There is also the case of negative modifying effect of shipwrecks over the years.
All these have affected the dynamics of coastline areas, leading to loss of lives, coastal land mass, infrastructure, etc.
Currently, we are in the “rough sea season,” especially in the Gulf of Guinea. Again, tropical regions worldwide are presently experiencing heavy sea storms, hurricanes, forest fires, etc. Hurricanes have ravaged the gulf of the U.S., North Korea and other parts of the world since August; and they may continue till September ending.
Sediment budget in the Lagos harbour, Bar Beach and, especially, the Kuramo Beach areas (since it is located downstream) have been increasingly compromised over the years. Furthermore, the effect of global warming, leading to climate change and rise in sea levels worldwide has also exacerbated the reach of the high energy waves.
If these aforementioned realities coincide with a high tide situation, a beach overflow should be expected. This was what caused the recent Kuramo Beach ocean surge. Indeed, studies in the last three years have shown regular beach overflows in the Apese area into the Onijedi lagoon just 1.5km away from Kuramo Beach. That is another clear and present danger.
It is evident the overflow at Kuramo is a result of the downstream effect of large-scale modification and obstruction of natural sediment flow, which has resulted in sediment deficit and changes in the local current climate in the area. Coupled with sea level rise due to global warming and high tide sea level in the Lagos harbour, Kuramo and Bar Beach areas, it is important to note that the hard engineering coastal management structure protecting the Bar Beach stops at the beginning of Kuramo Beach stretch. Hence, the area was also exposed.
The signs of the recent overflow were already with us from many years back. Unfortunately, they are still going to be with us until the right things are done. The way forward, therefore, is to do an all-inclusive hard and soft engineering coastal management system that could mitigate the effects of pounding wave energy on our shore without transferring the sea dynamics energy further downstream (east).
Also, we need to implement the mitigation plans of Environmental Impact Assessment for these projects to the letter. We must enlighten the shoreline masses and develop an environmentally friendly coastal culture. Similar feats have been achieved in Dubai and elsewhere without devastating environmental consequences. And the time to act is now.
At present, Kuramo lagoon is one of the only two closed lagoons we have in Lagos, and their ecological, economic and tourism potential cannot be overemphasised. Kuramo lagoon is also suffering from heavy and continuous organic pollution. There is the need to realistically and ecologically protect our coastline in Lagos, particularly areas where human activities have caused large-scale deleterious effects.
•Dr. Onyema wrote from the Dept. of Marine Sciences, University of Lagos, vide (Punch News)

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