- Gate-structure dam at Charly-sur-Marne...
- (R.R. Philéas Fotos/Daniel Osso)
- and at Chatou.
Gate-structure dams are designed to make rivers navigable by constructing a channel through them.
Thanks to these structures, the river level will be raised several metres to create successive reaches where boats can navigate. Nevertheless, they must be able to be overridden in the event of seasonal floodwater, as the river flow then increases massively.
The first of this type of structures appeared on the Yonne in 1842. These were so-called needle dams, in other words made of needles of wood mounted on an iron supporting structure.
Subsequently, these were improved to allow the structures to be lowered more easily when flooding came.
As techniques evolved, different models appeared, such as the hausses Aubert, from the name of their designer who was also the first director general of the CNR. Today, gate-structure dams are equipped with shutter gates or sector gates, supported on piles that take the stress.
It is worth noting that all the structures of the CNR on the Rhône are gate-structure dams... but of proportions quite different from those that are on smaller rivers.