Adapter les transports régionaux au changement climatique : passer du constat à l’action

Climate change is directly affecting the resilience of regional transport systems. The increasing frequency and intensity of extreme events such as floods, droughts, landslides, and heatwaves are exposing infrastructure to growing risks of degradation and service disruption.

In response to these challenges, the Région Sud – Provence-Alpes-Côte d’Azur and the French State launched an ecological planning initiative in 2023 to strengthen the sustainability and resilience of the regional transport system.

This approach is based on the ACoRS framework (Adaptation, Conversion, Modal Shift, Sobriety) and is part of a State-Region agreement aimed at developing a regional transport adaptation plan.

The objective is clear: anticipate rather than react. This requires integrating climate considerations as a core parameter in transport policies and investment decisions.

A robust scientific foundation to support public decision-making

Cerema is leading a research and development study aimed at assessing the physical climate risks affecting all transport infrastructures, including road, rail, river, maritime, and airport systems.

To carry out this analysis, Cerema Méditerranée has formed a consortium of public and private stakeholders, including:

• BRGM, for the analysis of certain natural hazards;
• GeographR, for environmental and territorial geoscience and foresight;
• Hydroclimat, for the production of climate indicators and climate risk modeling.

The objective goes beyond building a knowledge base. It is about producing information that can be directly used for planning, prioritizing actions, and guiding public investment decisions.

Hydroclimat’s contribution

Producing climate data tailored to infrastructure

Open-source reference climate datasets (CMIP6, DRIAS, TRACC) are essential. However, they reach their limits when it comes to conducting detailed spatial analyses at the scale of local infrastructure.

Hydroclimat has therefore developed a downscaling methodology at a 1 km² resolution, enabling:

• a more accurate representation of climate extremes (intense precipitation, heatwaves, droughts);
• the analysis of return periods to better characterize extreme events;
• the integration of uncertainty through a multi-scenario and climate narrative approach.

This spatial resolution is essential to move from a regional understanding of climate to an operational analysis of transport networks.

Developing differentiated hazard and vulnerability indicators

Rather than relying on a single-threshold approach, Hydroclimat develops composite indicators that combine climate data, topography, and land use.

These indicators make it possible to:

• identify areas of exposure within the transport system;
• assess the physical vulnerability of infrastructure;
• define multiple levels of risk adapted to diverse territorial contexts.

This approach provides a more detailed and robust framework for prioritizing adaptation actions.

Linking climate data to on-the-ground realities

The analyses produced do not rely solely on climate modeling. They also incorporate operational feedback (infrastructure managers, local engineering teams) to refine degradation thresholds and assess the capacity of systems to absorb and adapt to climate hazards.

This integration of science, engineering, and operational insight is essential to deliver assessments that are both credible and truly actionable.

Making results clear and accessible

Hydroclimat also supports the design of reporting formats to ensure both scientific rigor and usability for a wide range of audiences, including technical teams, local authorities, and decision-makers.

Maps, dashboards, risk narratives, and transparent communication of uncertainties are developed as true decision-support tools, rather than simple technical deliverables.

What this approach delivers in practice

Hydroclimat’s contribution to this project provides the Region and the State with:

• a robust, spatially detailed scientific foundation for ecological transport planning;
• a significant improvement in the territorial accuracy of risk analyses;
• operational decision-support tools to prioritize adaptation investments;
• a better understanding of uncertainties and their impact on infrastructure resilience;
• enhanced integration of local knowledge and field feedback, strengthening the legitimacy of recommendations.

Conclusion

This collaboration demonstrates that an effective transport adaptation strategy cannot rely on generic climate data or purely top-down approaches. It requires a territorially grounded adaptation science, capable of linking climate modeling, local vulnerabilities, and operational decision-making.

At Hydroclimat, we are convinced that only under these conditions can climate information become a true lever for transforming public policy, supporting more resilient territories in the face of climate change.