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Ingérop at the heart of a flood prevention project for SIRRA

For the past four years, Ingérop, a major player in engineering and consulting, has been working with SIRRA (Syndicat Isérois des Rivières Rhône Aval) on a project to restore the environment and protect against flooding in the Sanne and Dolon watersheds in Isère. Thanks to an innovative collaborative method involving all stakeholders, a development scenario for the two watersheds achieved general consensus. On the strength of its expertise and the support of the stakeholders for the approach, Ingérop will now carry out the preliminary design for this scenario.


Located in the Isère region of France, SIRRA’s objectives include preserving and restoring the proper functioning of aquatic environments, as well as preventing and protecting human interests from the impact of flooding. Within this framework, the syndicate is managing and coordinating a Flood Prevention Action Program (PAPI) for the Sanne and Dolon watersheds, as part of their development plan. The program focuses on a number of areas: raising public awareness of the risks, taking account of flood risk in urban planning, and reducing vulnerability.

In 2019, SIRRA launched a call for tenders to carry out a comprehensive study of the territory’s flooding potential, knowledge of how rivers function and knowledge of aquatic environments (state of rivers and surrounding environments). Ingérop won the tender, thanks to its technical expertise and in-depth knowledge of the area.


To carry out this mission, Ingérop joined forces with two partners: its subsidiary Géos, for the geotechnical component, and Ginger Burgeap, a consulting firm specializing in environmental studies.

Three phases were carried out:

  • Diagnosis of the area: Ingérop and its two partners collected and analyzed existing data to understand how the environment functions (flood history, environmental degradation, etc.). They also carried out a detailed analysis of the hydraulic functioning in the event of flooding. The group carried out hydraulic modelling (computerized flood simulations) based on very precise topographical data and land-use characteristics. An inventory of the current situation and a list of existing structures were thus drawn up.
  • Vulnerability study of the territory: this study enabled us to highlight sensitive areas, where property and people are particularly exposed to the risk of flooding. The aim of this phase was to provide a summary of the area’s vulnerabilities (exposure to flooding and environmental degradation), in order to define preservation/restoration and flood protection objectives.
  • Analysis of development solutions: the analysis of multiple solutions assessed their contribution to achieving the set objectives (flood reduction, improvement and restoration of environmental conditions). The effectiveness of development solutions was quantified using models (local, generalized effects, etc.). This numerical technique was used to select several combined development scenarios.

In June 2023, 4 combined development scenarios were presented to the steering committee partners (elected representatives, associative members, economic partners, etc.) to present the results of this analysis and enable collective reflection, through workshops. At the end of this collaborative process, a development scenario was selected. Ingérop is assisting SIRRA in the next stages of refining the characteristics of the selected project.