European Geologist Journal 61

Assessing pipeline detachment risk at river crossings under future climate scenarios

by Clélia Marchand 1, Claire Saint-Macary 2, and Guayente Corral-Broto 3,*

1  Hydraulic Engineer at SURVEY

2  Head of the Industrial Safety Department at TEREGA

3    Head of the Studies and Engineering Department at SURVEY

*  Corresponding author: g.corral@survey-groupe.fr

Abstract

Transmission pipelines often intersect dynamic river environments where natural geomorphic processes can lead to scour, exposure, and potential failure. This study, conducted with TEREGA, assesses current and future detachment risk at more than 500 river crossings in southwestern France. A methodology combining two decades of inspection data with climate and hydrological projections for 2030 and 2050 was developed, using RCP and GWL scenarios. Each crossing was assigned a risk level through a weighted scoring system integrating environmental hazard indicators and site-specific vulnerability. Results show strong spatial variability, with localized increases in extreme flows despite regional drying trends. The approach supports targeted monitoring and provides a scalable framework for climate‑resilient pipeline management.  

Keywords

Pipeline exposure, infrastructure vulnerability, detachment risk, river crossings, climate projections, hydrological projections, TEREGA

Cite as: Marchand, C., Saint-Macary, C.& Corral-Broto, G. (2026). Assessing pipeline detachment risk at river crossings under future climate scenarios. European Geologist, (61). https://doi.org/10.5281/zenodo.21888180

Note:

Papers published in this special issue of the European Geologist journal have undergone a thorough peer-review process but have not been copy-edited. Authors bear full responsibility for the linguistic accuracy of their contributions.

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1. Introduction

Gas transport pipelines inevitably intersect dynamic environments such as rivers, whose morphology evolves over time and can compromise structural integrity especially under climate event [1]. This study, conducted in collaboration with TEREGA [2], one of the main natural gas transmission operators in southwestern France, aims to assess and anticipate the risk of pipeline detachment at river crossings under changing climatic conditions.

TEREGA operates a network of approximately 5,000 km, representing nearly 15.7% of the French transmission system, including more than 500 river crossings—critical points requiring continuous monitoring.

Figure 1: TEREGA gas network.

SURVEY has partnered with TEREGA for decades to perform morphodynamical monitoring and related studies. This paper presents the methodology and findings of the latest assessment, integrating climate change projections into risk analysis.

2. Detachment Risk at River Crossings

2.1 Monitoring and Inspection Protocols

Regular monitoring programs are implemented for each crossing to track morphodynamic evolution. These include classical topographic and bathymetric surveys [3] and pipe detection campaigns conducted every 2–10 years, depending on site sensitivity and management priorities.

Figure 2: (a) Plan and (b) photograph of a river crossing in 2018.

Figure 3: (a) Plan and (b) photograph of a river crossing in 2025.

The resulting database, spanning over 20 years for some crossings, provides a robust foundation for analysing morphological trends and hydraulic changes.

2.2 Risk Assessment Framework

Pipeline burial depth varies according to installation period, regulatory context, and technical constraints. Based on observed trends, we estimate the likelihood of pipe exposure and potential uprooting, defined as the point where hydraulic forces exceed mechanical resistance [4,5].

Three risk levels are established:

  • High risk: Pipe excavated and hydraulic conditions sufficient for uprooting,
  • Moderate risk: Pipe exposed but hydraulic stresses insufficient for immediate failure,
  • Low risk: Burial depth and river dynamics ensure protection in the short to medium term.

Figure 4: Example of an exposed pipe.

3. Integrating Climate Change into Risk Analysis

3.1 Data Sources

To account for climate change, we used two major French portals:

  • DRIAS-Climat [6]: Provides climate projections aligned with adaptation strategies,
  • DRIAS-Eau [7]: Aggregates hydrological projections, notably from the Explore 2 project,

These portals offer free access to indicators derived from IPCC scenarios, adapted to the French context [8].

3.2 Climate and Hydrological Projections

Flow projections follow IPCC Representative Concentration Pathways (RCPs) [9]:

  • 6: Optimistic, carbon neutrality before 2100 (now considered unrealistic).
  • 5: Emissions peak ~2040, then decline (partial stabilization).
  • 5: Pessimistic, emissions continue rising throughout the century.

Figure 5: Carbon emission trends under RCP scenarios.

Precipitation projections are expressed by Global Warming Levels (GWL) [10]:

  • 2030 / GWL1.5°C: +2°C in France,
  • 2050 / GWL2.0°C: +2.7°C in France,
  • 2100 / GWL3.0°C: +4°C in France.

Southern Europe warms faster than the global average due to its transitional climate zone, increasing vulnerability to drier summers and reduced Atlantic regulation.

4. Data Processing and GIS Integration

4.1 Hydrological and Climate Data Treatment

We integrated DRIAS data at the scale of each river crossing using GIS-based spatial joins. Two cases were considered:

  • Direct station match: Projection station located on the stream crossing the pipeline.
  • Nearest station approach: Data from hydrologically comparable catchments weighted by inverse distance.

Figure 6: Percentage change in the annual maximum of daily discharge at the scale of France between 2024 and 2030.

Precipitation data were processed similarly. The outcome: projections of annual maximum precipitation and discharge for each crossing.

4.2 National Contextualization

To assess significance, we performed statistical analyses on climate and hydrological projections across France, defining quantile-based classes. Each crossing was then classified relative to national trends, providing a comparative risk level.

Figure 7: Percentage change in the annual maximum of daily discharge at the location of TEREGA RC’s between 2024 and 2030.

5. Conclusion and discussion

The results highlight a strong spatial variability in pipeline detachment risk at river crossings, both under current conditions and in climate projections. This heterogeneity confirms the need for a differentiated approach, prioritizing areas where fluvial dynamics and hydrological regimes are most sensitive to extreme events.

Integrating climate and hydrological projections into the risk assessment represents a significant advantage compared to traditional methods, which rely primarily on historical observations. The scenarios analysed show that, despite an overall drying trend in southwestern France, extreme flood events may intensify locally, increasing detachment risk for certain crossings. This evolution underscores the importance of going beyond climate averages and accounting for variability and extremes.

The methodology developed in this study presents several strengths:

  • Scalability: it can be applied to a large number of sites while remaining adaptable to local specificities.
  • Regulatory compliance: it meets national requirements [11] and aligns with the broader European framework [12,13].
  • Forward looking capability: it supports the development of monitoring and adaptation strategies, in line with climate resilience objectives.

However, some limitations must be noted:

  • The accuracy of projections depends on uncertainties inherent to climate and hydrological models [14].
  • Historical morphodynamical datasets, although robust, do not always cover all crossings with the same level of detail.

In conclusion, this study demonstrates the relevance of integrating climate risks into the management of linear infrastructure. For TEREGA, it provides a decision-support tool to prioritize interventions and strengthen network resilience. More broadly, the proposed methodology can serve as a reference for other operators facing similar challenges, contributing to a harmonized approach to adapting energy infrastructure to climate change.

References

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This article has been published in European Geologist journal 61 – 5th IPGC Special Edition 2