Plastic turning back the tide
Are rising sea levels inevitable ?
Even the experts don’t know!
Could rising sea levels due to climate change swamp many coastlines? No-one knows for sure, but the possibility can’t be ruled out. So, readiness is the watchword.
The precautionary principle prevails, and the plastics industry, architects and urban planners are already ramping up innovative and sustainable solutions.
A country built below sea level
One European country famously at risk from this potential rise in sea levels is the Netherlands.
This highly urbanized nation has continuously reclaimed land from the sea. In a matter of centuries it has made sub-sea-level areas liveable-on by creating the well-known polders. How exactly?
By building impressive dikes and digging countless channels to drain off the excess water.
But is this enough to cope with a big rise in sea levels?
The Dutch government is getting to grips with the matter, and has drafted architects and engineers to come up with ideas for floating homes. While some of the designs are really just houseboats, others can be described as amphibious.
Although anchored on dry land, they can adapt to a five-metre rise in water. Human ingenuity plays a big part, but it is a feat of engineering that couldn’t have happened without the use of plastics.
The bearable lightness of being
Houses are heavy, dense, and they don’t float. Well, not traditional buildings, anyway. So the architects and engineers had to first reinvent a more lightweight house. That meant finding new materials. And again, the plastics industry delivered by developing a composite material made up of a fibreglass- and epoxy resin-reinforced polyurethane core.
It is lightweight, strong, rigid, waterproof and long-lasting - all the properties needed for the structure of these floating houses. But still not enough to ensure householders’ safety and peace of mind…
No foundations, but hollow cubes
Lightweight structures are one thing, but how can you make a house rise if the sea level goes up? Simply by building them on huge floaters, also made of composites.
They are completely watertight and maintenance-free, even salt water abrasion-proof. What these floaters are, are permeation-resistant boxes buried beneath the house. If the waters rise, mini-channels divert it directly under the house and buoyant force makes the dwelling rise. The house is obviously anchored to very strong piles, and attached to rails which allow it to rise vertically.
It floats, but is it watertight ?
Watertightness is the second secret to the manufacture of these new-style houses. There are different ways of achieving it, all of them from the plastics industry. In most cases, a bituminous coating is used, reinforced with different polymers to which fibreglass strips are applied. Not much more can be said about these polymers, which remain a fiercely guarded industrial secret! The coating is applied only at ground-floor level and guarantees perfect impermeability even against high-pressure waters (tidal waves, storms, river flooding etc.). Best of all, this kind of house is very often eco-friendly and frequently fitted with solar panels and a waste-water and rainwater recycling management system.
There is also talk in Holland of extending the already well-developed concept of floating and amphibious housing to vegetable crops. Soilless culture (hydroponics) is a booming business, and floating greenhouse schemes are starting to appear. The principle would be pretty much the same as for housing, with the only difference that these greenhouses could have ten to fifteen times the floor area of residential buildings.
There seems to be no technological reason why not, as these greenhouses, while larger, are single-storied and, much lighter.
How many tragedies could have been averted if the dikes had held during Atlantic storm Xynthia? Dikes are easily damaged, and both difficult and costly to maintain! Over years, not to say centuries, the power of breaking waves can damage and weaken their structure.
Dikes are, after all, just an assembly of concrete blocks or stones. Water seeps through, wearing them away until one day, the whole structure collapses. But BASF, however, may just have found a way to make dikes almost indestructible. That solution is Elastocoast®.
Combien de drames auraient pu être évités si, lors de la tempête Xynthia, les digues avaient tenu ? Une digue, en effet, c’est fragile ! C’est par ailleurs aussi difficile que coûteux d’entretien. Au fil des ans, voire des siècles, la puissance des vagues peut rompre leur équilibre.
Rappelons que les digues ne sont qu’un amoncellement de blocs de béton ou de rochers. L’eau s’y infiltre, creuse, jusqu’au jour où l’édifice s’effondre. Toutefois, il semblerait bien que la société BASF ait trouvé la solution pour rendre les digues quasi indestructibles.
Cette solution, c’est l’Elastocoast®.
Strengthening the coastline
This remarkable innovation has been used by the Netherlands and Germany since 2004, and has also been taken up by France, most notably in Le Havre and the autonomous ports of Bordeaux and Paris.
Elastocoast® is an elastomeric polyurethane system (two-component polyurethane) purpose-developed to reinforce armourstone dike revetments. Simply put, it is a resin that is mixed with the armourstones. The mixture is then poured all over the traditional dike. Once dried, this innovative aggregate and plastic composite creates a perfect barrier preventing water from breaching the dike.
What about the environment ?
The components of all construction materials are always likely to migrate into the surrounding environment. This is a big concern for the plastics industry, and one that was taken into account when designing Elastocoast®. Studies were done to assess whether the material would impact the aquatic environment. The answer was not long coming – within weeks, the Elastocoast®-coated dikes had been colonized by a range of local vegetation and animals.