By Christopher Sell
Christopher Sell looks into the technicalities of land reclamation projects.
Very few places in the world have relied on land reclamation techniques to the extent seen in Dubai. Burj Al Arab aside, land reclamation has played a pivotal part in shaping the emirate's future, with projects such as the Palm trilogy, Dubai Waterfront and the World acting as a marker for the scale of Dubai's ambition.
Yet what is actually required to develop these sites? From the coast, residents and tourists alike have, over the past five years witnessed dredgers depositing vast quantities of sand into the sea, until slowly a land mass has emerged. But how complicated is this process and what factors have to be taken into account to prevent damage to marine life, while at the same time ensuring that the off-shore construction is robust enough to withstand years of environmental exposure?
It is not devoid of life, but a relative desert in marine terms and nothing like a coral reef.
As it is a marine-based project, there is an emphasis on marine ecology. Therefore, the first part of an off-shore project is an environmental impact assessment (EIA), which will be assessed by marine biologists. According to Shaun Lenehan, senior manager, environment, Nakheel, results from this have caused changes in original designs, most notably, he says, the original plans for Dubai Waterfront were thrown out and re-drawn to take into account Jebel Ali reef, which is part of a wildlife sanctuary. Martin Mid-East was the firm tasked with the EIA on Palm Jumeirah.
Between the site investigations and the finished product, Nakheel must manage the dredging contractors who are under strict obligations from their governments' to behave in an environmentally responsible manner, as well as adhere to numerous international maritime agreements. Dutch dredger, Van Oord, has worked for Nakheel on the Palm Jumeirah, as well as the Palm Deira and The World.
"When we engage the dredging contractor, I get a visit from their credit insurers," says Lenehan. "They sit with me to ensure that Nakheel has sufficient environmental management systems and has done its environmental homework. They have to report to the Dutch government, for example, and have to stand up in the House and say it's legitimate, because some of these contracts are massive. They won't get insurance unless they are content Van Oord is doing something responsible."
Once contracted, these dredging companies - who are predominantly from Holland and Belgium, which has a rich history in land reclamation, are bound to the environmental management requirements that Nakheel has written. "Part of that is a dredging and reclamation guideline that we have prepared through a workshop with Jan DeNul and Van Oord, so it is very practical and real and takes into account Dubai's ambient water quality." This has also mapped sensitive areas along Dubai's coastline.
Lenehan adds that certain requirements are made of the dredging contractors, mainly the use of material and particularly the particle size itself, as well as the ‘borrow area' - the area where the sand is acquired. "The area is a long way out to sea, typically the sediment we want is coarse sand. It is not devoid of life but a relative desert in marine teams and nothing like a coral reef.
"Where possible, we get material as close as possible to our development. This way we don't have to carry it too far, it saves on fuel bills and we can therefore build faster," he adds.
Yet, as Oman's Cyclone Gonu proved in June this year, it is clear that sand grain dimension and dredging are not the only concern. The impact of global warming is being felt in the Middle East, as much as elsewhere. Rising sea levels and unpredictable weather patterns have raised the question: How well protected are these reclaimed projects? And what is being done to ensure that they are capable of coping with freak weather, such as that seen in Oman?
In answer, Lenehan points out that basic geographical and oceanic conditions predetermine very little chance of such an event occurring in the Gulf, as cyclones occur when low pressure systems coming out of the tropics hit landfall to produce a tropical depression and rain. The Gulf also has shallow water with depths of just 35m, which prevent generation of deep swells and has a very short fetch.
"Cyclone Gonu was a 60-year storm," he adds. "I'm guessing a lot of structures that broke were under-designed. Most of the damage done on the mainland occurred due to the rain and run-off due to overland flows. When they design a bridge or culvert, they design those for a certain rainfall event, and it was obviously nowhere enough in Oman, and that is why they were destroyed."
When you see on the news that something has failed, it is because it has been poorly maintained, poorly designed, or the storm has exceeded that criteria.
For the reclaimed off-shore projects, Lenehan explains that to ensure the structures can cope with such meteorological extremes, is actually relatively straightforward, with marine engineering measuring a number of probabilities, including a charcacteristic called average recurrence interval (ARI) or average exceedance probability (AEP). In other words a ‘storm event criteria', which in Nakheel's case is a 1 in 100.
"Historically, we look at the weather and forecast and see what is the biggest storm that will hit the Gulf in a 100 years and look at the wave size associated with that. That's assuming you get a big NW wind blowing all the way down to Kuwait, you look at the biggest waves coming out of that and then you design something that is going to withstand that.
"Any marine structure, be it a quay wall or sea wall, is designed this way. When you see on the news that something failed, it is because it has been poorly maintained, poorly designed, or the storm has exceeded that criteria."
Aside from the storm event criteria, other factors which must be factored into the design include the king tide, which is the peak tide at a certain point in the year. In Dubai, whose tidal range is between 0.3m to 1.92m, this is 2.2m. This in itself is not necessarily a major increase, but it is a cumulative effect when the wave effect is factored, which, combined with predicted storm surges must all be considered.
"And on top of all that, we have factored in 50-60cm sea level rise," Lenehan adds.
On the Al Marjan Islands, an off-shore development in Ras Al Khaimah, similar concerns over rising water levels have been levelled. "These things will happen - whether it's a cyclone or an earthquake," says Imad Haffar, chief operating officer, Rakeen - the company developing Al Marjan Islsands.
"But our island is going to be a safe place to live as we've taken care of issues such as water surges, tidal activity, water fluctuations and global warming - particularly since last year's World Bank report that predicted rising sea levels. So in terms of water elevation, the structure will be 4-4.5cm above sea level. This island is also being constructed within a 2A zone for seismic activity."
While the long term impacts of extensive off-shore land reclamation cannot be realised for many years to come - some already question the impact of the Palm on Dubai's beaches with regards to reduced sedimentation amongst other environmental concerns - the logistics of planning, managing and carrying out such extensive projects cannot be underestimated.
But for the hundreds of thousands who are in the process of, or planning to make a Gulf off-shore development their home, Cyclone Gonu should not influence their decision.For all the latest construction news from the UAE and Gulf countries, follow us on Twitter and Linkedin, like us on Facebook and subscribe to our YouTube page, which is updated daily.