Demolition of the Denges weir

As part of an overall plan to restore fish migration in the Venoge, 6 weirs have been identified as currently constituting major obstacles to the free movement of fish. The Denges weir (weir O1) is of particular importance as it is the furthest downstream, with a height of over 2m. Several remediation options were studied and compared. The chosen option is to remove the weir entirely and allow the natural dynamics and equilibrium gradient of the watercourse to take hold. As the safety issues are fairly limited (few objects to be protected apart from the Domaine Equestre de la Garenne), changes to the bed and banks upstream of the weir will be subject to the natural dynamics of the watercourse and regular monitoring will be put in place. In all cases, the danger situation will not be exacerbated, particularly downstream, thanks to the installation of a protective dyke around the Garenne estate.

1D hydraulic and sediment modelling with long-term simulation (10 hydrological years) has highlighted the potential for reaching the equilibrium slope.

As the weir is a Vaud cantonal heritage site, stabilisation works will enable the historic structures on the left bank to be preserved and protected, while allowing the Venoge to flow freely.

The project was engineering by Gruner from the analysis of variants to the call for tenders. The subsequent phases up to execution are still to come.

Period :

2019-2022

Services :

Variant analysis 
Hydraulic and sediment modelling ;
Preliminary design ;
Dimensioning and conceptual analysis;
Coordination with the piscicultural expert
Preparation of the engineering design
Prepaparation of the Public Enquiry dossier;
Construction aspects and preservation of listed heritage.

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