Bridges, dams, dykes… How drought destabilizes infrastructure

This summer, a historic drought affects Europe but also France. Currently, 93 departments out of 96 are experiencing water restrictions and a crisis meeting on the drought took place this Monday at the Ministry of Agriculture. Such a situation has consequences on our daily lives, our homes but also… our infrastructure. Indeed, European bridges, dykes and dams are put under pressure by the lack of water.

Dryness, the enemy of clay

This is, for example, the case dykes in the Nederlands. In water shortage since August 2, the country finds that the constructions in question are weakened by the drought, in particular the small structures which are essential for draining water and drying out the polders. “ In the Netherlands, many dikes are made of sand and especially clay coverings which pose a problem in the event of drought.explains Édouard Durand, geotechnical and natural hazard expert, specialist in dykes for the CEREMA. “These clay materials, when they dry, experience a very significant change in volume and cracks appear on the ridges, dykes and embankments. In fact, this layer of clay providing the seal can lose its role with this situation “, he adds.

And France is no exception when it comes to its own dikes: “ Some structures have been monitored for several years because they have cracks, on the Atlantic coast in particular“says the researcher. The main problem being water variation around these structures explains Édouard Durand. Indeed, if said variations are too great, they impact the clay materials. These impacts can lead to these cracks but also to sliding or even, in extreme cases, a collapse during a flood, where a breach opens through the cracks. These fluctuations being set to multiply with climate change, the “surveillance must be increased“, Considers Édouard Durand, who specifies:”In the Nederlands, on some dykes, they have to water to avoid cracking and maintain a certain level of water. However, that has costs and that does not help the problem of drought”.

Turfing of infrastructures to fight against water variations

Moreover, this problem does not only concern dykes but also, to a lesser extent, bridges where water tends to become scarce. This is the case, among others, of Italy where the Po river has been dry for several weeks. However, bridges installed on clay soils can suffer the consequences of desiccation: “ in particular on the bearings on which the bridges are placed. Heat and dryness can cause them to expand», observes Roland Abou, specialist in bridges and works of art at CEREMA.

The drought does not spare the dams either: Dams, unlike dykes, are permanently filled with water. If some parts are exposed due to drought, there may also be degradation.“, underlines Edouard Durand. He adds that this drought also leads to feeding difficulties when the dam is used to produce electricity, but not only: “ It is also necessary to feed the river and the managers have an obligation to do so. It is essential to sustain life in waterways “. Consequences already experienced by the Fabrèges dam, in the Pyrenees-Atlantiques. This supplies water to the Vallée d’Ossau and has never known such a low reserve.

However, the impact of Drought is still minimal for most French works of art: “today they are rather designed to avoid having too much water, so drought has less consequences», Reacts Roland Abou. Despite everything, measures have been taken to strengthen the infrastructure: “ One of the solutions is to turf the structures, in particular the dykes“says Édouard Durand. The specialist explains that this sodding not only helps maintain humidity at the same level while preventing the penetration of drought. “ And then, it must be said that the phenomenon of drought is quite recent so studies are underway to best respond to these changes. concludes the researcher.

SEE ALSO – China triggers artificial rains to fight drought