CJAMY. Camille Gaubert’s column is broadcast daily on “C Jamy”, hosted by Jamy Gourmaud from Monday to Friday at 5 pm, in France 5.
When it comes to floods, those who do not invest in trenches or inflatable boats, but in science, are more far-sighted today. Proof with the Icube laboratory in Strasbourg, where the unique model and equations of fluid mechanics allow the creation of flood prevention tools.
Flood model using a unique model
At the University of Strasbourg, the Icube laboratory has set up a strange and impressive system, unique in its kind, to study the hundred-year-old floods, these great floods that happen once a century. The goal is to model them, that is, to reproduce their behavior on a computer using equations: in which direction will the water flow, at what speed, at what height, what will be the impact of the buildings in its path? Thanks to this model, whose initial parameters can be adjusted, it is possible to predict it.
The researchers’ calculations are based on observations made on makes a model of five meters per side which reproduces a quarter of an imaginary city. Each tank represents a block of buildings, between which cross streets whose slope can be changed. At the end of each street, a pump controls the water supply used to simulate the flood. When water attacks the model, sensors and cameras monitor its speed, height and flow. With this model, researchers can therefore create custom floods to study them! “The challenge is to be able to model extreme floods. This neighborhood is completely imagined. We are trying to understand how water circulates on the pavement, on the street, how it spreads at the intersection, how it divides, that is, whether it will have strong or strong currents. Low speed“, explains José Vazquez, Professor of Hydraulics at ENGEES, Team Leader” MécaFlu “at the Icube Laboratory at the University of Strasbourg
Avoid “torrents” that take away anything in their path
It may sound ridiculous, but this work is vital. You should know that during a flood, even a very athletic adult cannot stand in 50 cm of water when running at a speed of 1 meter per second … However, floods can reach 5 meters per second. Second: we are talking about torrents, the strongest and most dangerous. They are dominated by their speed and therefore flow straight ahead, unlike slow so-called “fluvial” species, says José Vazquez. This type of flow affected the village of Breil-sur-Roya in October 2020 in the Maritime Alps, following storm Alex. “The big difference is that we see the fluvial flow coming in, we see the height increase little by little. On the other hand, with the torrent flow, the water rises very quickly and the emergency services have great difficulties in intervening.“, points out the expert.
A useful tool for regional planning
The team uses the classical equations of fluid mechanics to model what are the velocities, the heights of the water, how the water divides at the intersection, which creates constrictions, which restricts the flow. Possible obstacles, such as the accumulation of parked cars or the width of the sidewalk, are also taken into account. “The whole point is that an engineer can use our results, simply because our method cannot be sold: the model itself already costs 600,000 euros!“, supports José Vazquez. The aim is to use their tool during urban development, for example the relevance of adding an intersection or roundabout in a particular place. In France, 13,300 municipalities out of 30,000 in France are exposed. floods.