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Proceedings of the 19th young geomorphologists days

Mathieu Fressard, Aurélien Christol et André-Marie Dendievel
p. 3-5
Cet article est une traduction de :
Actes des 19èmes journées des Jeunes Géomorphologues

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1The 2018 edition of the French young geomorphologists days have been organized in Lyon after a 12 year turnover between Paris and several other regional universities. We would like to thank the organizing committee (Fanny Arnaud, Adrien Bara, Barbara Belletti, Marie‑Laure Chambrade, Aurélien Christol, Étienne Cossart, Maël Crépy, André‑Marie Dendievel, Mathieu Fressard, Jean‑Philippe Goiran, Nicolas Jacob, Gary Lardaux, Jérôme Lejot, Kristell Michel and Oldrich Navratil) for their help with the preparation of the event and the tenue of the scientific sessions. We thank also the university Lyon 2, Lyon 3, the CNRS UMR 5600 EVS and 5133 Archéorient for their financial support for the event. This event is also supported by the French group of geomorphology (GFG). We acknowledge the 12 anonymous referees who, by donating their time in reviewing manuscripts, contributed to improving the scientific quality of the five articles of this special issue.

2On the 26 and 27 of January 2018, more than 75 participants attended to 22 oral presentations and 16 poster communications at the University of Lyon. This year again, the PhD students and young doctors came from the whole county (Aix‑en‑Provence, Caen, Cayenne, Chambéry, Clermont‑Ferrand, Grenoble, Lyon, Nantes, Paris, Saint-Étienne). Moreover, this 2018 edition is characterized by a high rate of young researchers from abroad, with 5 contributions from Italy and 4 contributions from Switzerland. The event was structured around 3 thematic sessions: Fluvial geomorphology (7 communications), slope dynamics (8 communications) and paleo-environments and geoarcheology (7 communications). Two invented speakers complemented the daily programs of these days: Michel Mietton (prof. emeritus, University Lyon 3 – UMR 5600 EVS) and Yann Callot (prof. emeritus, University Lyon 2 – UMR 5133 Archéorient). On Saturday afternoon, a field trip animated by Stéphane Gaillot from the archeological survey of Lyon (SAVL) brought us through the geomorphological patrimony of the city.

3This first 2019 issue of “Géomorphologie: Relief, Processus, Environnement” brings together five articles following this 19th edition of the JJG. The article from Defive et al. (2018), following the oral presentation of André‑Marie Dendievel about the fluvial system history of the Gage valley (Loire, France) has been published in the last issue of 2018 (2018–4).

4The first three articles are taken from the “Slope dynamics” session.

5The article of Farvacque et al. (2019) aims at quantifying the rockfall hazard on the Chartreuse massif hillslopes at Crolles (Isère). This article illustrates the current concern of geomorphologists to develop applied and reproductible approaches to help stakeholders in the risk prevention methodologies. The authors develop a mapping methodology founded on the combination of a physically based model and statistical analysis of the model outputs. Then, modelling can be seen as an interesting alternative to estimate the return period of low frequency/high magnitude events, that are often difficult to quantify due to the lack of historical data. Quantitative risk analyses appears to be a major perspective of applied research combining geomatics and geomorphology.

6Still in mountain areas, the article from Duvillard et al. (2019) deals with the role of permafrost in the destabilization of ski lifts pylons. In this case study developed in Val‑Thorens (French Alps), the authors use a multi-method approach (combining stratigraphic analysis, seismic tomography and stereophotogrammetry) to quantify the pylon displacements and interpreting the causes of the instability. The authors show that the permafrost melting is mainly due to earthworks and landscaping that modifies the surface (runoff) and sub-surface (active layer thickness) dynamics. Then, the authors underline the interest of the pre-implantation diagnosis for the infrastructure development in mountain areas that could help avoiding construction errors.

7Reconstructing the historical trajectories of geomorphological phenomena is often challenging due to the difficulty in combing and analyzing documents from various sources with different spatial resolutions. In their article, Roulland et al. (2019) develop a methodological approach based on the diachronic analysis of historical documents to reconstruct the evolution rate of the Vaches Noires cliffs in Normandy over 260 years. Based on a rigorous analysis of the error margins associated with the quality of the used documents, the authors show that the evolution rate can be significantly different regarding the observed temporal window. These cliffs evolve through a long term geomorphological cycle (from 250 to 300) and flowing a complex association of processes: landslide, mudflow propagation, marine erosion that lead to coastal retreat and progressive initiation of new landsliding processes upslope.

8The two other articles are taken from the “paleoenvironment and geoarchaeology” session.

9The article from Genuite et al. (2019) proposes an innovative and original approach based on the coupling of high resolution 3D data (Terrestrial Laser Scanning) with geomorphological mapping to study karstic landforms. The authors sought to identify the causes of the meander cutoff that lead to the Pont d’Arc formation (main geomorpholosite of the Ardèche gorges). The geomorphological correspondences observed in the field and on Digital Elevation Model (DEM) between the Chataigniers cave and the Pont d’Arc (karstic network, quaternary deposits etc.) allow a better documentation of the meander cutoff. The latter must be originating from the Quaternary period under the influence of a pre-existing karstic network.

10The article from Leblé and Poirot (2019) aims at documenting the geomorphological evolution of a small low energy river (le Sausset, Tremblay-en-France) from the middle age to the modern period. Based on a chronostratigraphic approach, the authors confirm the filling dynamics of these small catchments observed at the Paris basin scale. The local evolution of the valley is characterized by an extension/retraction of the wetland and also by sediment balance variations directly correlated with climate changes (little ice age) and anthropogenic pressure (pastoralism).

11This special issue of the 19th young geomorphologists days recall the importance given to specific research objects traditionally studied in geomorphology: rivers, hillslopes and coastal areas. These objects are analyzed through their relationship with local or global forcing either on a long time scale (millennial or century scale) or short time scale (annual or instantaneous scale). Faced with such an entanglement of spatial and temporal scales, one can only plead once again for a geographical approach in geomorphology. Regardless of the research object or analyzed timescale, the proposed approaches show the increasing use of quantitative analyses and modelling in the current research, still coupled with field investigations which are essential to provide first-hand datasets. The developed researches are also strongly connected to society by focusing on land use planning, natural hazards prevention or promoting the geomorphological heritage.

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Mathieu Fressard, Aurélien Christol et André-Marie Dendievel, « Proceedings of the 19th young geomorphologists days », Géomorphologie : relief, processus, environnement, vol. 25 – n° 1 | 2019, 3-5.

Référence électronique

Mathieu Fressard, Aurélien Christol et André-Marie Dendievel, « Proceedings of the 19th young geomorphologists days », Géomorphologie : relief, processus, environnement [En ligne], vol. 25 – n° 1 | 2019, mis en ligne le 08 mai 2019, consulté le 26 mai 2019. URL : http://journals.openedition.org/geomorphologie/13043

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Auteurs

Mathieu Fressard

Université de Lyon, Université Jean Moulin Lyon 3, UMR 5600 CNRS-Environnement Ville Société – Lyon, 69007, France (mathieu.fressard@univ-lyon3.fr).

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Aurélien Christol

Université de Lyon, Université Jean Moulin Lyon 3, UMR 5600 CNRS-Environnement Ville Société – Lyon, 69007, France (aurelien.christol@univ-lyon3.fr).

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André-Marie Dendievel

LEHNA-IPE, UMR 5023 CNRS, 3 rue Maurice Audin, 69518 Vaulx-en-Velin Cedex, France (andremarie.dendievel@gmail.com).

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