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Proceedings of the 18th Young Geomorphologists Meeting

(Paris, 27 January 2017)
Vincent Viel et Anaëlle Vayssière
Cet article est une traduction de :
Actes des 18ème journées des Jeunes Géomorphologues

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1The organizers thank the entire organizing committee (Gilles Arnaud‑Fassetta, Edouard de Belizal, François Bétard, Benoît Carlier, Rémi De Matos Machado, Aline Garnier, Emmanuèle Gautier, Vincent Jomelli, Franck Lavigne and Yann Le Drezen) as well as Paris Diderot University, for their help in organizing this meeting. We would also like to thank the eight reviewers who agreed to evaluate the four articles that make up this issue. Their comments and advices have greatly contributed to the scientific quality of this issue.

2Organized by the Groupe Français de Géomorphologie (GFG), the 18th Journée des Jeunes Géomorphologues (JJG) was held at the Paris Diderot University (Paris 7) on January 27, 2017. It was followed this year by the first Journée des métiers de la géomorphologie, conducted by Emmanuèle Gautier and Grégory Dandurand at the Institute of Geography in Paris. During this day, the students were able to meet professionals working in engineering companies, environmental or risk management services, or associations. Jointly organized by the Prodig (UMR CNRS 8586) and LGP (UMR CNRS 8591) laboratories, the JJG gathered about fifty participants representing 19 French universities. It was an opportunity for 15 young researchers to present their work as oral presentations (11) or as posters (4). Topics covered during the JJG were diversified and various studied areas were represented (France, Central African Republic, Indonesia, Spitsbergen, Greenland). Presentations were divided into 4 thematic sessions focusing on (i) hydromorphology and river management; (ii) current rivers dynamics; (iii) geomorphology: history and geoarchaeology; and (iv) observation and modeling of changes. This first 2018 issue brings together 4 articles from this 18th edition of the JJG. The article written by Hortobágyi et al., 2017, winner of the prize for best communication was published as part of a special issue devoted to the biogeomorphology (Géomorphologie : Relief, Processus, Environnement, 2017-3).

3The first three articles in this issue highlight the enthusiasm of French geomorphologists for questions related to sediment transit within the sedimentary cascade. In this research, the authors try to quantify the observed processes, using high precision investigation methods to measure the topography as well as water and sediment fluxes (D-GPS, photogrammetry, tracing RFID, seismic, etc.). These tools are now particularly used in research developed by young researchers in geomorphology. The works presented also demonstrate the highly operational scope of these studies in terms of environmental resource or risk management.

4With a fluvial hydromorphology approach, Gilet et al. analyze sediment mobilization and morphological adjustments induced by the restoration of ecological and sedimentary continuity in rivers, imposed in 2000 by the Water Framework Directive (DCE). They seek to understand the controlling factors and temporalities of hydromorphological adjustments of the Yonne River, following the removal of the Pierre Glissotte dam (Morvan, 89). The analysis is conducted using an accurate measurement of forms, water and sediment flows. The study provides particularly valuable information about the remobilization rates of sediments stored upstream of the reservoir and brings essential information poorly documented in France while the number of dam removal projects significantly increases. The results indicate a rapid response of the river system since 23% of the sediment initially stored in the reservoir was exported during the first 9 months. Silts and sands mobilization is almost immediate, even at low flows. Coarser sediments transport is also rapid because they traveled up to several hundred meters during the field work period.

5The following two articles are based on the Peynin watershed and the Peyronnelle, one of its tributaries (Queyras, 05), being periodically subject to significant torrential floods. In their article, Graff et al. try to evaluate the mobilization and the redistribution of sediments during a debris flow observed in August 2015. Authors trace coarse sediments using a RFID method, still infrequently used in a torrential context. They show that the distance traveled by sediments is particularly variable according to the location from which they were mobilized. They thus demonstrate a great complexity of sedimentary dynamics associated with debris flows. The quantification of the sedimentary flows and the analysis of their redistribution in the Peynin watershed underline the major role of this phenomenon which is able to significantly recharge the sedimentary cascade in the downstream part of the watershed.

6The article proposed by Carlier et al. seeks to spatialize and quantify sediment storage (mainly colluvial), set up since the last glacial maximum in the Peynin watershed. The study combines a dual approach based on (i) geological, geomorphological and geophysical expertise of the superficial geology conducted during field surveys, and (ii) morphometric modelings of sediment thicknesses. The mixed results of the models highlight the complexity of the evaluation of these storages and bring the authors to remain cautious about the sediment storage estimation. Nevertheless, they clearly show a significant spatial variability of these storages within the watershed. These storages are mainly located on the left bank of the Peynin, because of landslides, and in the upstream of the basin as rockslide or scree cones.

7The knowledge acquired in these two articles thus makes it possible to explore the functionality of the sedimentary cascade of the Peynin watershed, and its capacity (or not) to export large amounts of sediments. They highlight the intertwining of spatial and temporal scales that induce the very complex relay processes that must be taken into account to better understand sedimentary dynamics observed at the outlet of the watershed.

8Finally, Biette et al. seek to identify past climate change on a long time scale. They propose to estimate the temperature conditions at the end of the Medieval Climate Anomaly (~950 AD – 1250 AD, MCA) for the Disko Island (West Greenland). These data should be used to explain the increased glacial extent of the Lyngmarksbræen Glacier, whose dynamic is opposite to those usually observed in the northern hemisphere. The authors adopt an original approach associating a glaciological degree - day modeling and a simulation of ice flow by cellular automaton. Results rely on a chronology of the Lyngmarksbræen’s moraines previously established from cosmogenic data. They are also validated by a number of tests carried out on the various parameters modeled. They show a cooling between ‑1.3°C and ‑1.6°C at the MCA compared to the current period. The authors bring important discussion points to better understand the high spatial and temporal variability of temperatures at the MCA.

9All these articles published as part of this special issue devoted to the 18th Journée des Jeunes Géomorphologues thus present a variety of objects, approaches and questions, carried out at various spatial and temporal scales. However, this diversity also reveals the geomorphologist’s attachment to field work which still constitutes the base of the researches in the discipline.

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Vincent Viel et Anaëlle Vayssière, « Proceedings of the 18th Young Geomorphologists Meeting », Géomorphologie : relief, processus, environnement [En ligne], vol. 24 - n° 1 | 2018, mis en ligne le 30 mars 2018, consulté le 28 mai 2018. URL :

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Vincent Viel

Université Paris 7-Diderot, Sorbonne Paris Cité, UMR 8586 CNRS-PRODIG – 5 rue Thomas Mann, 75013 Paris, France (

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Anaëlle Vayssière

Université Paris 1 - Panthéon Sorbonne, UMR 8591 CNRS-LGP – 1 place Aristide Briand, 92195 Meudon, France (

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