An estimation of gravel mobility over an alpine river gravel bar (Arc en Maurienne, France) using PIT-tag tracers

River morphodynamics and sediment transportRiver morphology and morphodynamic

Impact of land use on the hydraulic properties of the topsoil in a small French catchment

The hydraulic properties of the topsoil control the partition of rainfall into infiltration and runoff at the soil surface. They must be characterized for distributed hydrological modelling. This study presents the results of a field campaign documenting topsoil hydraulic properties in a small French suburban catchment (7 km2) located near Lyon, France. Two types of infiltration tests were performed: single ring infiltration tests under positive head and tension disk infiltration using a mini-disk. Both categories were processed using the BEST Beerkan Estimation of Soil Transfer parameters- method to derive parameters describing the retention and hydraulic conductivity curves. Dry bulk density and particle size data were also sampled. Almost all the topsoils were found to belong to the sandy loam soil class. No significant differences in hydraulic properties were found in terms of pedologic units, but the results showed a high impact of land use on these properties. The lowest dry bulk density values were obtained in forested soils with the highest organic matter content. Permanent pasture soils showed intermediate values, whereas the highest values were encountered in cultivated lands. For saturated hydraulic conductivity, the highest values were found in broad leaved forests and small woods. The complementary use of tension disk and positive head infiltration tests highlighted a sharp increase of hydraulic conductivity between near saturation and saturated conditions, attributed to macroporosity effect. The ratio of median saturated hydraulic conductivity to median hydraulic conductivity at a pressure of -20 mm of water, was about 50. The study suggests that soil texture, such as used in most pedo-transfer functions, might not be sufficient to properly map the variability of soil hydraulic properties. Land use information should be considered in the parameterizations of topsoil within hydrological models to better represent in situ conditions, as illustrated in the paper

The AVuPUR project (Assessing the Vulnerabiliy of Peri-Urbans Rivers): experimental set up, modelling strategy and first results

International audienceLe projet AVuPUR a pour objectif de progresser sur la compréhension et la modélisation des flux d'eau dans les bassins versants péri-urbains. Il s'agit plus particulièrement de fournir des outils permettant de quantifier l'impact d'objets anthropiques tels que zones urbaines, routes, fossés sur les régimes hydrologiques des cours d'eau dans ces bassins. Cet article présente la stratégie expérimentale et de collecte de données mise en ½uvre dans le projet et les pistes proposées pour l'amélioration des outils de modélisation existants et le développement d'outils novateurs. Enfin, nous présentons comment ces outils seront utilisés pour simuler et quantifier l'impact des modifications d'occupation des sols et/ou du climat sur les régimes hydrologiques des bassins étudiés. / The aim of the AVuPUR project is to enhance our understanding and modelling capacity of water fluxes within suburban watersheds. In particular, the objective is to deliver tools allowing to quantify the impact of anthropogenic elements such as urban areas, roads, ditches on the hydrological regime of suburban rivers. This paper presents the observation and data collection strategy set up by the project, and the directions for improving existing modelling tools or proposing innovative ones. Finally, we present how these tools will be used to simulate and quantify the impact of land use and climate changes on the hydrological regimes of the studied catchments

Recueil de données du bassin versant de l'Yzeron. Année 2009

[Departement_IRSTEA]Eaux [TR1_IRSTEA]ARCEAU [Relecteur_IRSTEA]Branger, F. ; Le Coz, J.Ce document présente les données suivies en continu sur le bassin hydrographique de l'Yzeron, site atelier géré par l'unité de recherche Hydrologie-hydraulique du Cemagref de Lyon. Quelques données de mesures ponctuelles ou à caractère discontinu complètent ce document

Recueil de données du bassin versant de l'Yzeron. Année 2010

[Departement_IRSTEA]Eaux [TR1_IRSTEA]ARCEAU [Relecteur_IRSTEA]Le Coz, J. ; Branger, F.Ce document présente les données suivies en continu sur le bassin hydrographique de l'Yzeron, site atelier géré par l'unité de recherche Hydrologie-hydraulique du Cemagref de Lyon. Quelques données de mesures ponctuelles ou à caractère discontinu complètent ce document

Surveillance, prévision des crues et inondations dans le bassin de l'Yzeron : Étude de définition d'un système d'interprétation des relations entre la saturation des sols, les précipitations et les débits

Dans le cadre du Programme d'Actions et de Prévention des Inondations (PAPI) du bassin de l'Yzeron, mis en oeuvre par le SAGYRC, l'une des actions concerne une « Etude de définition d'un système d'interprétation des relations entre la saturation des sols, les précipitations et les débits ». Le présent rapport contribue à cette action. Une première tâche visait la mise à disposition auprès du SAGYRC, des données collectées par Irstea sur le bassin versant de l'Yzeron, à savoir les données de pluie et de hauteur d'eau dans les cours d'eau. Il s'agit de 6 stations pluviométriques et de 5 stations de mesure du niveau d'eau et température de l'eau dans les cours d'eau ainsi que le débit dans le déversoir d'orage et le collecteur de Grézieu-la-Varenne. Y ont été ajoutées les deux stations de mesure de l'humidité des sols mises en place par Irstea début 2018. Ceci a été mené à bien, après une mise à niveau des modes de télétransmission des données, la création d'un site FTP sur les serveurs d'Irstea permettant au SAGYRC de récupérer les données en temps quasi-réel avec un pas de temps d'une heure en régime normal et mise à jour des données toutes les 5 minutes lors d'une crue. Le logiciel permettant la lecture et l'exploitation des données a été installé sur le serveur du SAGYRC. Le service est maintenant opérationnel et le SAGYRC peut récupérer l'information dans de bonnes conditions. Une deuxième tâche avait pour obectif l'analyse des données disponibles et la modélisation hydrologique. Une première étape du travail a consisté à réunir ou mettre à jour les jeux de données nécessaires à l'étude. Ceux-ci concernent essentiellement la pluviométrie (données de stations pluviométriques, données radar, réanalyses SAFRAN) et l'hydrométrie (chroniques de hauteur d'eau et de débits) disponibles sur le bassin. Une étude comparative des différentes sources de données pluviométriques disponibles a montré la pertinence des données de réanalyses radar pour le bassin versant et la bonne cohérence avec les mesures des pluviographes du bassin

Suivi des réseaux hydrographiques à l'aide d'un réseau de capteurs de niveau d'eau

International audienceIn this study we considered that hydrological network is a central feature of the catchment. We assumed that hydrological regime depends on the activation and expansion of the drainage network witch controls flow lengths. The degree of drainage network expansion is not uniform in volume and timing. This spatial knowledge is essential to understand catchments behaviours conditioned at fine scale level by the connectivity between hillslope and channels. To efficiently achieve this monitoring, numerous, low cost and easy adaptable sensors have to be promoted with a specific sampling strategy. An experimental distributed water level sensor network was carried out in the temporary hydrological network of the Mercier catchment (7 km²) located near Lyon (France). This study site is one of the headwater research catchments of the Yzeron watershed (142 km²). Land use is principally composed of pasture, crops and some urbanized areas in the downstream part with a couple of road side ditches connected to the streams. Forest is concentrated on steepest hillslopes in the upper part. The catchment is located in small metamorphic mountains where infiltration and subsurface flow predominate during most rainfall events. Saturation excess runoff is the major process contributing to channel network. The device consisted of 18 sensors set up since 2008 in nested locations from high order streams to the outlet. The data logger recorded water levels directly by measurements of an electric capacity. By means of 4 rain gauges located in the catchment, rainfall events were selected with a reasonable spatial heterogeneity in volume, intensity and duration. Resultant pattern highlighted over all the attenuated response of the upstream channels to some filling degree of local storages and capacities. Differences were pointed out between upstream sub-catchments responses and breaks in propagation and discharges toward downstream channels were precisely located. For most of rainfall events the downstream part of the channel network controlled most of the quick flow response recorded at the outlet. Channel network expansion to upstream locations depended on rainfall threshold and antecedent condition expressed by the base flow. Upstream contribution became significant during only some consequent rainfall events, around 5 to 10 by year. Data recorded provided spatial representation of flow initiation and propagation improving the understanding of the Mercier catchment in the purpose of distributed hydrological modelling

Effect of different inlet flow conditions on turbulence in a straight compound open channel

peer reviewe

A distributed water level network in ephemeral river reaches to identify the hydrological responses of anthropogenic catchments

International audienceIn order to study the impact of land use change on the water cycle, distributed hydrological models are more and more used, because they have the ability to take into account the land surface heterogeneity and its evolution due to anthropogenic pressure. These models provide continuous distributed simulations of streamflow, runoff, soil moisture, etc, which, ideally, should be evaluated against continuous distributed measurements, taken at various scales and located in nested sub-catchments. Distributed network of streamflow gauging stations are in general scarce and very expensive to maintain. Furthermore, they can hardly be installed in the upstream parts of the catchments where river beds are not well defined. In this paper, we present an alternative to these standard streamflow gauging stations network, based on self powered high resolution water level sensors using a capacitive water height data logger. One of their advantages is that they can be installed even in ephemeral reaches and from channel head locations to high order streams. Furthermore, these innovative and easily adaptable low cost sensors offer the possibility to develop in the near future, a wireless network application. Such a network, including 15 sensors has been set up on nested watersheds in small and intermittent streams of a 7 km2 catchment, located in the mountainous Mont du Lyonnais area, close to the city of Lyon, France. The land use of this catchment is mostly pasture, crop and forest, but the catchment is significantly affected by human activities, through the existence of a dense roads and paths network and urbanized areas. The equipment provides water levels survey during precipitation events in the hydrological network with a very accurate time step (2 min). Water levels can be related to runoff production and catchment response as a function of scale. This response will depend, amongst other, on variable soil water storage capacity, physiographic data and characteristics of raining events. Several raining events, with different characteristics, have been extracted from a large data set collected during two years. From these numerous hydrographs, analyses of flow dynamic through rising limbs, falling limbs and lag times show different behaviour pattern according to instrumented reaches. The paper will present first results from this synoptic survey. It shows the dynamic spatial pattern of stream flow along the water pathes. At finer scale, this synoptic survey could show the impacts of anthropogenic features on water concentration and their hydrological connectivity to natural river network

Action 11 : Evaluation du potentiel écologique dans une rivière urbaine fortement modifiée

[Departement_IRSTEA]Eaux [TR1_IRSTEA]ARCEAU [TR2_IRSTEA]QUASAREL'évaluation du potentiel écologique d'un cours d'eau est ici abordée au travers de l'étude des variables de contrôle physiques qui conditionnent l'habitat aquatique lorsque la qualité de l'eau est par ailleurs réputée bonne. Des méthodes génériques sont proposées depuis un cas d'étude