LIttoral ENvironnement et Sociétés (LIENSs) - UMR 7266

Axis 3 : Marine submersions

Thierry Guyot — 2026-10-21T14:17:22Z

Marine flooding is among the natural disasters causing the heaviest human losses and material damage. Such disasters may be of meteorological and oceanographic origin (storms, high waves, infragravity waves) or geodynamic origin (earthquakes, landslides), and the phasing of these phenomena with the tide can also be decisive. The coastal areas most vulnerable to marine flooding are estuarine environments and deltas, particularly when they include poldered areas, often at very low elevations. The research conducted in Axis 3 first aims to improve understanding of the physical processes responsible for marine flooding, by combining numerical simulations with seabed hydrodynamic and geophysical measurements for tsunami hazard. This research also seeks to better determine the recurrence of these events, through their sedimentary record or the analysis of historical archives.

Action 1 : Physical processes and sedimentary record of marine flooding associated with storms, waves and infragravity waves.

Simulation numérique de la submersion marine associée à la tempête Xynthia (Bertin et al., 2014)

Action 2 : Seafloor deformation and sedimentary record of tsunami-related flooding.

Axis 2 : Hydro-sedimentary dynamics and stratigraphy of coastal zones

Thierry Guyot — 2026-10-21T14:15:39Z

This axis focuses on the hydrodynamic processes affecting coastal zones over the short term (waves, infragravity waves, tides, storm surges), the associated sediment transport, and the resulting morphological and stratigraphic changes, at time scales ranging from the hydrodynamic event (e.g. a storm) to the century. These processes are studied particularly in estuaries and the mouths of meso- to macrotidal coasts, as well as on specific sedimentary features such as foreshores, sand spits and tidal sandbanks.

Action 1 : Numerical modelling of hydrodynamics, transport and sediment behaviour in estuaries and lagoons

Coupled wave/current/sediment-transport morphodynamic simulation of the Longe de Boyard between 1960 and 2000 (Guérin et al., 2016)

Action 2 : From processes to sedimentary archives : sea-level variations, hydrodynamic processes and morphostratigraphic changes in coastal environments

The LIENSs laboratory is part of the DYNALIT (Coastal and Shoreline Dynamics) observation system, monitoring three coastal sites in Charente.

Axis 3

Axis 1 : Sea level and Vertical coastal movements

Thierry Guyot — 2026-10-21T14:13:13Z

Vertical land movements at the coast are present in the sea level variations recorded by tide gauges. They may be of epirogenic origin (tectonics, volcanism, postglacial rebound, sedimentation processes) or anthropogenic (subsidence related to the pumping of underground fluids, hydrocarbons or groundwater). A few examples opposite show their importance over long periods of time spanning several decades or even centuries (Figure adapted from PSMSL).

These are therefore signals of non-climatic origin that need to be carefully determined in order to separate them from the climatic contributions, namely the thermal expansion of the oceans and the melting of continental ice (polar ice caps or alpine glaciers), but also to better understand them and take them into account in projections of sea level evolution at the coast and the associated impact studies. The ultimate challenge is to better anticipate and better adapt to coming changes, whether of epirogenic or climatic origin.

– The first action of this research axis is to determine these vertical movements through observation, more precisely by space geodesy and absolute gravimetry methods. Among space geodesy techniques, GPS quickly established itself due to the quality of its results, its practical use and the relatively reasonable cost of the equipment. An example of the potential of this technique is given below, illustrating the presence of vertical land movements in long tide gauge time series and how detailed analyses of GPS measurements can separate (reduce) them in order to better isolate the climatic contributions (action 1).

Time series of annual mean sea levels derived from the analysis of : (left) tide gauges ; (middle) tide gauges corrected for postglacial rebound using the predictions of the Peltier [2004] ICE5G (VM2) model ; and (right) corrected using our GPS results expressed in the ITRF2005 geocentric reference frame ; (top) Northern Europe and (bottom) North-West America (units are in mm).

– The second action is to understand and model the processes responsible for vertical movements. Within the wide range of epirogenic processes, postglacial rebound is an important large-scale phenomenon for which relatively precise models exist (so-called glacio-isostatic adjustment or GIA models). However, the accuracy of their predictions is limited by our knowledge of the deglaciation history and of the parameters of the Earth model, such as lithosphere thickness or the viscosity profiles of the upper and lower mantle (action 2).

Marégrammes historiques (Marseille)

Precise sea level measurements, complementary to and independent of tide gauging, have been provided by satellite radar altimetry since 1992 (for example, the Topex/Poseidon satellite). Furthermore, historical archives are also an important source of sea level data, all the more so as the French heritage proves very significant, in terms of both stations and data volume, and it bears witness to a bygone past that can no longer be revisited (to measure), but which is interesting to study in order to understand present-day sea level fluctuations. these ancillary aspects of actions 1 and 2 are important in research axis 1, and we remain on the lookout for resource opportunities to explore them.

Action 1 : Determination of relative and absolute sea level variations ; separation of climatic contributions from epirogenic contributions

Action 2 : Understanding vertical movement processes related to postglacial rebound

Parallel action : Development of an observation Service infrastructure called SONEL (www.sonel.org), labelled by the INSU (CNRS) in 2011

Axis 2

Scientific production from team "DPL"

Thierry Guyot — 2026-10-21T13:39:10Z

publications 2026 :

16 résultats

2026

Article dans une revue

Four decades of morphological changes at a macrotidal bay: High-resolution intertidal sediment stock monitoring and uncertainty quantification

Loës Le Goff Le Gourrierec , Xavier Bertin , Jamal Khan , Nicolas Lachaussée , Natacha Volto

Coastal Engineering, 2026, 211, pp.105085. ⟨10.1016/j.coastaleng.2026.105085⟩

LIttoral ENvironnement et Sociétés (LIENSs) - UMR 7266

Axis 3 : Marine submersions

Action 1 : Physical processes and sedimentary record of marine flooding associated with storms, waves and infragravity waves.

Action 2 : Seafloor deformation and sedimentary record of tsunami-related flooding.

Axis 2 : Hydro-sedimentary dynamics and stratigraphy of coastal zones

Action 1 : Numerical modelling of hydrodynamics, transport and sediment behaviour in estuaries and lagoons

Action 2 : From processes to sedimentary archives : sea-level variations, hydrodynamic processes and morphostratigraphic changes in coastal environments

Axis 1 : Sea level and Vertical coastal movements

Action 1 : Determination of relative and absolute sea level variations ; separation of climatic contributions from epirogenic contributions

Action 2 : Understanding vertical movement processes related to postglacial rebound

Parallel action : Development of an observation Service infrastructure called SONEL (www.sonel.org), labelled by the INSU (CNRS) in 2011

Scientific production from team "DPL"

2026

Article dans une revue

Chapitre d'ouvrage

2025

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2024

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Chapitre d'ouvrage

2023

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2022

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2021

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2020

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Chapitre d'ouvrage

2019

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2018

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Chapitre d'ouvrage

2017

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Chapitre d'ouvrage

Research axis

Scientific objectives

Introduction