development of the Brinaz river

Following the mapping of flood hazards associated with the Brinaz river at its alluvial fan in the communes of Grandson and Montagny-près-Yverdon, and the development of guidelines for a safety concept (2009), Gruner SA was commissioned to design the works.

Before the first works were carried out in 2019, the Brinaz flowed through a trapezoidal masonry canal. The hydraulic capacity of this channel was insufficient to meet flood protection objectives, and it was also deficient in terms of the ecomorphology of the watercourse. 

The project involves widening the river by up to 29 m in areas where land-use planning permits, modifying its longitudinal profile and renaturating the bed and banks so as to make the area safe for low probability events (48 m³/s). The project also includes the raising of dykes (to over 2 m) and the construction of new integrated dykes.

The project involves replacing or modifying 7 water crossing structures, including a SBB structure and a cantonal road bridge with a 22 m span. The project also includes the installation of a 1.5 m high timber harrow upstream of the section to be upgraded. The work was divided into 3 lots. 

Gruner was responsible for supervising the construction work on 2 lots: the harrow (lot A) in 2017 and the development of the downstream section (lot C) in 2019, i.e. the renaturation work on 280 m of the Brinaz in the sector between the SBB bridge and the downstream farm road, as well as the construction work on a new bridge, known as the "downstream bridge", with a 13 m span. As part of the early work on lot B, Gruner was also responsible for building a retaining wall to protect a business from flooding.

Services:

• Hydraulic studies: hazard maps, 1D and 2D hydraulic modelling, solid transport analysis; river renaturation options;
• Assistance to the project owner during clarification meetings with riparian owners;
  Project design (SIA 32 phase), including pre-dimensioning of structures (harrows, bridges);
• Preparation of the building permit application file (SIA 33 phase);
• Preparation of tender documents for lots A and C, analysis of tenders (SIA 41 phase);
• Drawing up the execution file, calculation notes and plans (SIA 51 phase);
• Supervision of work on lots A and C (SIA 52 phase);
• Compliance with execution plans (SIA 53 phase).

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