3rd correction of the Rhône – Priority measures at the martigny elbow and the rivers Dranse and Trient

3rd correction of the Rhône – Priority measures at the martigny elbow and the rivers Dranse and Trient

Client

Office cantonal de la construction du Rhône (OCCR3)

Execution

Ongoing since 2014

Collaboration

BG piloted the "Coude du Rhône" joint-venture, including:

  • Moret & Associés SA
  • Stucky SA
  • kbm Engineers SA
  • Bureau d'Etudes Géologiques SA
  • BEB SA
  • Etec Sàrl
  • Alpa urbanisme et aménagement du territoire Sàrl

Project description

This sector at the Martigny elbow (the "Coude de Martigny") is a high priority area of the third correction of the river Rhône, due to the extent of the damage possible in the event of a major flood on the Martigny plain. This project represents the first step in a safeguarding plan for the Riddes-Martigny floodplain.

The project combines the widening of the river and the lowering of the riverbed at the elbow, comprising the construction of a ramp and the rehabilitation and protection of the banks over a length of 4.5km.

It integrates the geometrical transformations of the Dranse and Trient confluences, and modifications to the Leytron-Saxon-Fully and the Syndicat canals. Two major widenings in the Verney sector and downstream of the mouth of the Trient are planned as well. These technical measures have been developed considering ecological, social and landscape objectives.

The key points considered were:

  • Significant lowering of the river bed (~1.5m) requiring comprehension of the impacts on structures, groundwater and the natural environment.
  • Interactions with infrastructure, including a cantonal road, a highway, a gas pipeline, a high voltage line, the outlets of the Emosson and the Vernayaz hydroelectric power plants, roads, services networks etc.
  • Rigorous, quantifiable and ambitious ecological objectives.
  • Management of bedload transport, and significant volumes of excavation material.
  • Coordination with a large number of third party projects and the riverside communities.
  • Management of a large number of procedures in parallel in order to complete the planning permission.

Services provided

  • Preliminary design
  • Detailed design
  • Follow up of the physical modelling
  • Planning permission

BG managed the project and the multi-disciplinary team. We also took responsibility for a major part of the hydraulic design and the works, including the management of contaminated soil and materials

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