THE nant Manant du Bois de la Bâtie is an urban watercourse flowing, in its upper part open to the sky for approximately 250 meters, then entirely buried downstream to its restitution point in the Aire gallery (under the Route des Jeunes), which joins the Arve at from the Saint-Georges bridge.
The peaceful little stream that runs down the slope from the top of the woods towards the Arve can turn into a torrent, which overflows during violent storms, flooding up to the rue des Deux-Ponts. This very variable flow has, over time, caused strong erosion. The bed of the watercourse has deepened and the banks are now destabilized. Paths are at risk of collapse and debris accumulates at the edge, when water disappears underground, creating dams.
Necessary work
The renaturation project plans to have around thirty thresholds, with a height of approximately 50 centimeters, along the 250 meters of the watercourse in order to break the dynamics of the water, reduce the slope and reduce the flow speed. This work, carried out by the Green Spaces Service (SEVE), will drastically reduce erosion of the river bed, which will also be widened in places. Traveling along the water will be safe and movement nearby will be made easier.
A new gateway
On the upper two thirds of the stream, access will be removed to give more space to the nant. A new gatewaydevoid of pillars and therefore not subject to erosion by the waves, will span the river and the entire valley. It will be based on the commune of Lancy on the right bank and that of Geneva on the left bank.
The footbridge will be connected to Promenade Nicolas-Bouvier. L’entire route, dedicated to soft mobilitywill connect the Chapelle district to the Bois de la Bâtie and will be networked with the urban area greenway and the future Bernex greenway. The lower part of the path will be renovated and its base reinforced to avoid subsidence. The maintained path will be entirely repeated but will remain coated due to slope issues. A new barrier will be built, the existing candelabra will be replaced by the model used for the Bâtie wood paths.
L’All of these measures will also have a favorable effect on biodiversity.by the creation of small “lakes” generated by thresholds, stones and other light installations that are more respectful of the environment. Alternative access is offered to pedestrians until the work is completed.
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