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Understanding water infiltration and transfer in soft-clay shales slopes is an important scientific issue, especially for landsliding. Geochemical investigations are carried out at the Super-Sauze and Draix-Laval landslides, both developed in the Callovo-Oxfordian black marls, with the objective to define the origin of the groundwater. In situ investigations, soil leaching experiments and geochemical modeling are combined to identify the boundaries of the hydrological systems. At Super-Sauze, the observations indicate that an external water flow occurs in the upper part of the landslide at the contact between the weathered black marls and the overlying formations, or at the landslide basement through a fault network. Such external origin of water is not observed at the local scale of the Draix-Laval landslide but is detected at the catchment scale with the influence of deep waters in the streamwater quality of low river flows. Hydrogeological conceptual models are proposed emphasizing the role of the interactions between local (slope) and regional (catchment) flow systems. The observations suggest that this situation is a common case in the Alpine area. Expected consequences of the regional flows on slope stability are discussed in term of rise of pore water pressures and physicochemical weathering of the clay shales.

International audience; The establishment of plant species can limit soil erosion dynamics in degraded lands. In marly areas in the Southern French Alps, both harsh water erosion and drought conditions in summer due to the Mediterranean mountainous climate prevent the natural implementation and regeneration of vegetation. Soil fertility improvement is sometimes necessary. With the purpose of revegetating such areas, we aimed to evaluate the effects of wood chip amendments on the revegetation performance of different native or sub-spontaneous plant species. We conducted two experiments on steep slopes over three growing seasons (2012-2014). The first consisted of planting seedlings (ten species), the second consisted of seeding (nine species including six used in the first experiment). First we noted that wood chips were able to remain in place even in steep slope conditions. The planting of seedlings showed both an impact of wood chip amendment and differences between species. A positive effect of wood chips was shown with overall improvement of plant survival (increasing by 11% on average, by up to 50% for some species). In the seeding experiment, no plants survived after three growing seasons. However, intermediate results for the 1st and 2nd years showed a positive effect of wood chips on seedling emergence: seeds of four species only sprouted on wood chips, and for the five other species the average emergence rate increased by 50%.

The Roubine catchment located in the experimental research station of Draix-Bléone (south French Alps) is situated in Callovo-Oxfordian black marls, a lithology particularly prone to erosion and weathering processes. For 30 years, this small watershed (0.13 ha) has been monitored for analysing hillslope processes on the scale of elementary gullies. Since 2007, surface changes have been monitored by comparing high-resolution digital elevation models (HRDEMs) produced from terrestrial laser scanner (TLS). The objectives are (1) to detect and (2) to quantify the sediment production and the evolution of the gully morphology in terms of sediment availability/transport capacity vs. rainfall and runoff generation. Time series of TLS observations have been acquired periodically based on the seasonal runoff activity with a very high point cloud density ensuring a resolution of the digital elevation model (DEM) on the centimetre scale. The topographic changes over a time span of 2 years are analysed. Quantitative analyses of the seasonal erosion activity and of the sediment fluxes show and confirm that during winter, loose regolith is created by mechanical weathering, and it is eroded and accumulates in the rills and gullies. Because of limited rainfall intensity in spring, part of the material is transported in the main gullies, which are assumed to be a transport-limited erosion system. In the late spring and summer the rainfall intensities increase, allowing the regolith, weathered and accumulated in the gullies and rills during the earlier seasons, to be washed out. Later in the year the catchment acts as a sediment-limited system because no more loose regolith is available. One interesting result is the fact that in the gullies the erosion–deposition processes are more active around the slope angle value of 35°, which probably indicates a behaviour close to dry granular material. It is also observed that there exist thresholds for the rainfall events that are able to trigger significant erosion; they are above 9 mm rainfall or of an intensity of more than 1 mm min−1, values which can vary if antecedent precipitation is significant within the last 5 days.This study improves knowledge of the spatial distribution of erosion seasonality in badlands and demonstrates the potential of careful 3-D high-resolution topography using TLS to improve the understanding of erosive processes.

Un diagnostic archéologique, réalisé en 2009 par l'Inrap, sur la commune de Moncetz-Longevas (Marne), a permis de mettre en évidence des vestiges liés à une occupation protohistorique. La présence d'une sépulture ceinte d'un fossé circulaire a motivé la prescription d'une fouille archéologique, réalisée par le bureau d'études Éveha au début de l'année 2010. L'opération archéologique a mis en évidence une sépulture à chambre funéraire, dont l'architecture est en Blockbau, située au centre d'un enclos circulaire de 13 m de diamètre. L'étude stratigraphique relative à ce dernier a permis d'identifier la présence originelle d'un tertre qui coiffait la sépulture. Quelques restes osseux humains étaient répartis de façon éparse au sein de la chambre funéraire. Seuls deux os ont été découverts en position primaire; leur observation a permis d'envisager la position du défunt. La majorité du mobilier céramique correspond aux vases d'accompagnement découverts pour l'essentiel en position primaire. Aucune trace de la présence d'un char n'a été décelée mais de maigres indices interdisent d'écarter totalement l'hypothèse d'une telle présence. Dans un contexte archéologique dense, daté de la transition Hallstatt final — La Tène ancienne (Ve et IVe siècles avant notre ère), le défunt de la tombe de Moncetz semble d'un statut social élevé, même si l'on rejette l'idée de la présence originelle d'un char. Cette tombe constituerait alors l'exemple le plus remarquable et le plus prestigieux des tombes simples de la culture Aisne-Marne. Parallèlement, il est ici l'occasion d'effectuer un tour d'horizon des apports récents des campagnes de prospection aérienne dans ce secteur de la Champagne.

Dans cette étude, on a fait appel à la télédétection et aux systèmes d’information géographiques (SIG) pour évaluer et cartographier l’érosion hydrique en utilisant l’équation universelle des pertes en sol USLE dans le bassin versant de l’Oued Mina en Algérie. Ce bassin est caractérisé par une grande irrégularité dans les précipitations, une forte pente, une lithologie essentiellement marneuse et une couverture végétale très faible ce qui le rend très vulnérable à l’érosion. L’USLE est la combinaison de six facteurs spécifiques qui décrivent les caractéristiques du bassin versant. Les données de télédétection multi-temporelles et les SIG sont utilisés pour évaluer et cartographier chaque facteur individuellement. L’intégration des cartes thématiques des facteurs du modèle USLE dans le SIG permet de cerner l’impact de chaque facteur dans les pertes en sol, de classer par importance relative les zones d’érosion, et de quantifier les pertes en sol dans le bassin.

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International audience; Hybrid poplar plantations have become an important component of forest and agricultural landscapes in alluvial floodplains since poplars are among the fastest-growing trees in temperate regions. How- ever, these habitats are thought to decrease biodiversity, including ground beetle diversity, as compared to other traditional land-uses such as grasslands and semi-natural forests. To evaluate the impacts of poplar plantations on carabid diversity, we tested whether carabid assemblages are more affected by land-use type than by canopy cover type in three alluvial floodplains in North-Eastern France. We strat- ified our 63-plot sampling design according to four habitat types based on land-use and plantation age. Non-metric multidimensional scaling revealed a successional gradient in species composition related to canopy cover progressing from grasslands through young, then adult poplar plantations, to semi- natural forests. Species-level response models showed that many carabid species distinguished the open habitats (grasslands and young poplar plantations) from the closed ones (adult poplar plantations and semi-natural forests). Only a few species preferred one of the traditional land-uses such as grasslands or semi-natural forests. Based on our data, the deleterious effect of poplar plantations on the conservation of ground beetles may not be as high as expected.

In marly catchments of the French Southern Alps, the development of plant root systems is essential to increase slope stability and mitigate soil erosion, prevalent in this area. In a context of land restoration, it is important to be able to evaluate plant efficiency for soil reinforcement. This paper presents the results of investigations carried out on six dominant species from marly gullies and aims to compare the additional soil cohesion they provide. The six following species were collected: two tree species, Pinus nigra and Quercus pubescens, two shrubby species, Genista cinerea and Thymus serpyllum, and two herbaceous species, Achnatherum calamagrostis and Aphyllantes monspeliensis. For each of them, we measured root tensile strength and root area ratio in order to calculate the potential root reinforcement and to compare species suitability to prevent shallow mass movements. Results showed significant differences between species. The herbaceous species Aphyllantes monspeliensis and the shrubby species Genista cinerea provided the highest increase in soil shear strength while the tree species, Pinus nigra and Quercus pubescens were the least efficient at the early stages of plant development. These results, along with the knowledge on vegetation dynamics and species response to erosive constraint, allow us to better evaluate land vulnerability to erosion and the efficiency of restoration actions in eroded marly lands.

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International audience; The concentrations of dissolved trace elements (Li, B, Mn, Cu, As, Rb, Sr, Mo, Cd, Ba, Pb) in the Marne and Seine rivers in the Paris urban area were monitored over a 2-year period. The resulting data indicated moderate contamination of waters by the most toxic elements (Cu, As, Cd and Pb). The River Marne upstream and the River Seine downstream of the city of Paris displayed similar concentrations. However higher fluxes of trace elements were observed in the Seine than in the Marne due to their different discharges. Li, B, Rb, Sr and Ba concentrations were correlated with river discharge and concentrations were higher during high river flow. This was interpreted as a dilution by discharge from a major natural or anthropogenic source. Mn, Cu, Mo, Cd and Pb concentrations were not correlated with discharge. Dissolved Mn, Cu and Cd increased rapidly in summer, whereas the concentration of Mo decreased. These dariations were attributed to redox processes. During summer when the dissolved oxygen concentrations decrease, Mn, Cu, Cd and Pb are released into solution whereas Mo is immobilised. Like metals, variations in arsenic contents were not linked with discharge. Its similarity with phosphate distribution suggests similar controls involving phytoplankton uptake and release from sediments through organic matter mineralization.

International audience; The Cousance karst (located between the valleys of the Saulx and Marne) has been studied to determine the temporal records of river incision in the eastern Paris Basin, around the ANDRA experimental nuclear waste repository. Two generations of karst are recognized. The first is a palaeophreatic karst indicative of an old base level, now uplifted +75 m above the underground streams. It is underlain and drained by a second generation of karst with active sinks, which records the vertical evolution following the entrenchment of the River Marne. Ten U/Th dates of speleothems from shafts in the karst show that there were discontinuous growth episodes, mainly during isotopic stages 3 and 5 (between 102.4 ± 1.2 and 49.4 ± 0.4 ka bp) but also during isotopic stage 2 at 16.3 ± 0.1 and 20.9 ± 0.3 ka bp. These dates provide an absolute age limit for the start of vertical development of the karst, at the latest during isotope stage 5c.

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Present erosion in mountainous areas of Western Europe causes land management problems, particularly for areas located downstream of erosion zones. Except for transalpine roads and ski resorts, economic activities no longer require as much space as they did in the past. Therefore, natural reforestation has provided significant protection for alpine hillslopes during the 20th century. However, extreme floods continue to cause severe damage in intra-alpine valleys, as well as in piedmont and surrounding plains, making the study of present water erosion phenomena very important. Many studies have investigated the processes and factors of water erosion on slopes at both the catchment and plot scales. They have focused on rock fragmentation and transportation in different fields, the spatial and temporal explanatory variables, the consequences downstream (flooding, sedimentation, river bed evolution) and the impact of floods. In the French Alps, present erosion has been studied in a variety of outcrops, with several recent studies conducted in fields such as marls, clayey deposits, molasses and moraines. These kinds of outcrops are found throughout the alpine massif, including an area of special interest on the great Jurassic black marl outcrop where badlands are frequently observable. Geomorphologists and hydrologists have been particularly interested in the strong erosion processes in marls, seeking to determine the main patterns and the impact of spatial and temporal factors on soil loss quantities. The main climatic factors of rock disaggregation were found to be the freeze–thaw and wet–dry cycles, which destroy rock cohesion, and the splash effect of rain. The principal site variables are vegetation cover, exposure and dip–slope angle. Erosion rates are two or three orders of magnitude higher on bare soils than on pastures; northern aspect slopes suffer two to four times as much soil loss as southern aspect slopes. Finally, the angle formed by the slope and the dip also determines different behaviours: erosion rates are higher when slope and dip are perpendicular than when they are parallel. The transportation agents are mostly debris flows and runoff caused by intense precipitation. Annual erosion depth in the marls is generally assumed to be substantial, up to 10 mm. The high value can be explained by the severity of the climatic conditions and the brittleness of the lithology, which results in numerous fractures. Copyright © 2003 John Wiley & Sons, Ltd.

Jurassic black marls constitute one of the most extensive outcrops in the Alpine massif. They include the most eroded terrains in the French Alps. Black marls are subject to strong weathering and their erosion rate can reach values close to 1 cm year" (i.e. 100 rrr ha" year"1). Many studies have focused on the processes and forms of erosion of these black marls and on the development of an original metrology to improve our understanding of the seasonal processes in these badlands areas. This study shows that alternating freeze-thaw and wet-dry cycles are the main causes of disaggregation in the marls. The exposure of hillslopes and the dip-slope angle are the main site factors explaining the variability in the action of these processes and thus, in the soil thickness lost as a result of erosion. The kinetic energy of rainfall is similar everywhere, but the volumes of regolith transported by runoff depend on the effects of previous weathering.