Par Valentin Lebosse
Published on 20 May 22 at 7:08
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It’s a airplane not like the others who will fly over the Norman Seine valley in the next few days. In this case, a device equipped with a lidar. Either a laser that scans the ground, calculates the position and altitude of the points impacted, so as to obtain a three dimensional vision of the earth’s surface, with its micro-reliefs (such as ditches) or even the height of buildings, vegetation, etc.
Update flood risk prevention
Le public interest group (GIP) Seine-Aval had already carried out an equivalent project in 2011. But “these new data will be more precise”, indicates the GIP in a press release dated May 18, 2022.
The main information that we will draw from it will be a very precise topographic map. [de l’ordre de 5 cm pour l’altitude mesurée, NDLR] of the entire Seine valley, it will thus be possible to update the maps of the risk of flooding.
–This spatial analysis could also be of interest to other areas of public action such as town planning, observation of forest resources or the preservation of wetlands. According to Nicolas Bacq, it is also likely to pique the curiosity of archaeologists: “Forests preserve traces of constructions. However, the laser system can cross the forest cover, describe the topography and thus better understand the past use of the land. »
–When will it pass over Rouen?
If “the bulk of the work has already been done in March” between Vernon (Eure) et Le Havre (Seine Maritime), additional missions are planned for May, to take advantage of favorable tidal conditions. “The laser does not pass under water so when the Seine is high, we cannot collect information on the banks which are covered. You have to go at the right time, ”continues the coordinator.
The aircraft should fly over the Rouen area next week, the 22, 23 or 24 mai. If the weather turns out to be unfavorable, the next period will take place on June 4, 5 and 6.
The plane will circulate at 1,000 meters above the ground level. “It can make a little noise but that will have practically no consequences for local residents, relativizes Nicolas Bacq. It will be a small dot in the sky, so don’t expect to take pictures. »
To carry out this project, the GIP Seine-Aval joined forces with the Métropole Rouen Normandie and the Syndicat mixte de gestion de la Seine-Normande.
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