Polymers dam up the flow

Plastics turn back tides

Earthquakes, cyclones and violent thunderstorms invariably cause water levels to rise. Water seeps in everywhere and is able to tear down even the strongest bridge and carry away everything in its path.

When it comes to floods, it is important to distinguish between those of maritime origin and those resulting from a thunderstorm. In the latter case, the consequences can be tragic, but they are usually very localized and affect "only" a few thousand people. Although the rise in water levels due to a tsunami is inevitable, dikes can more or less contain it, depending on its intensity. Contrary to the ideas conveyed by science fiction films, a tsunami is not a wave several dozen metres high. It is a succession of powerful waves a few metres in height which will ultimately end up striking the coast. Dikes are designed to stop them, or at least slow them down. However, they need to be strong enough to do so! Having said that, tsunamis are not the only danger facing people living in coastal areas. Sometimes a large winter storm coupled with high tidal coefficients can cause great damage.

A combination of polyurethane and elastomer enables dikes to withstand the worst storms. In addition, this composite is neutral for the environment.

Most often, dikes are piles of concrete blocks or rocks. Their mass and volume are normally sufficient to cope with the power of the waves. However, that is not always the case. That is why, when building new dikes or restoring existing ones, it is common practice to reinforce them using a special elastomer and polyurethane compound developed by the German company BASF. Elastocoast® is mixed with crushed stones and forms a watertight barrier making the dikes indestructible.

In addition, several studies have been carried out to assess whether the material affects the surrounding aquatic environment. Happily, the dikes covered with Elastocoast® were once again colonised by a number of endemic species after a few weeks.

Plastics weren’t born yesterday

Thunderstorms are also a natural scourge, and not just because of lightning. In urban areas, water from their heavy rains must be drained away to help it evacuate as quickly as possible. One of the best solutions is to build retention basins to which the water is channelled. This is effective if they are properly sized. The only problem is that it is impossible to cover them effectively to build even a public garden above them. This makes sense, since the basins are usually empty and contain only air... Some local authorities consider this wasted space. A French company may have found the solution by developing the Boulbac®, a hollow ball measuring about a dozen centimetres in diameter made of recycled polypropylene that fills the basins. The principle is simple and ingenious: once in the basin, the water infiltrates into the balls and drives out the air. It is stored there for the time it takes to drain slowly into the water table. The balls thus make it possible to store water while supporting the weight of a green space or a playground on the surface. It should be noted that, contrary to what one might think, the difference in storage capacity between a basin filled with balls and an empty basin is minimal because these balls have a voids ratio of 85%. To have a capacity equal to that of an empty basis, all that needs to be done is to increase its volume by 15%, which is not much... The idea seems to be particularly judicious as it allows tons of used polypropylene to be recycled. The Boulbac® won the Plastic Recycling Award Europe in 2018.

These balls made of recycled polypropylene enable retention basins to have a secondary use, as playgrounds or public gardens for instance.