Precipitation, soil mosture and runoff variabilty in a small river catchment (Ardèche, France) during HyMeX Special Observation Period 1

Flash flooding is a potentially destructive natural hazard known to occur in the Cévennes-Vivarais region in southern France. HyMeX (Hydrological Cycle in the Mediterranean Experiment) is an international program focused on understanding the hydrological cycle in the Mediterranean basin. Soil moisture is known to be a useful indicator of catchment response, however, establishing a meaningful estimation of soil moisture at the catchment level can be difficult due to its high variability in space and time. In a small gauged catchment in the Cévennes-Vivarais region in southern France, a series of manual soil moisture measurements was taken from September to December 2012 at both the field and catchment scale during the Special Observation Period 1 (SOP1) as part of the HyMeX program. Six plots were selected along a trajectory of a microwave link installed in the catchment and were chosen to represent different elevations in the catchment. Within each field plot, surface soil moisture was measured along a 50 m transect at 2 m intervals. This allowed the study of changes in within-field variability as well as between-field variability in response to precipitation events and during the drying out phase. Several precipitation events occurred over this autumn 2012 period which caused a significant wetting-up of the catchment, allowing the study of soil moisture processes over a wide range of wetness conditions. The influence of antecedent catchment conditions (soil moisture) on rainfall–runoff dynamics is demonstrated through the comparison of storm hydrographs for the various events. Dry catchment conditions result in minimal response in event flow, whereas large precipitation events occurring during wetter conditions produce much stronger responses in event flow. This further confirms the importance of quantifying catchment initial conditions to enhance the prediction of flash flood occurrences

Un jeu de données à haute résolution spatiale et temporelle reliant forçage météorologique et réponse hydro-sédimentaire dans le bassin méso-échelle de l'Auzon (Ardèche, France)

International audienceA comprehensive hydrometeorological dataset is presented spanning the period 1 January 2011-31 December 2014 to improve the understanding of the hydrological processes leading to flash floods and the relation between rainfall, runoff, erosion and sediment transport in a mesoscale catchment (Auzon, 116 km²) of the Mediterranean region. Badlands are present in the Auzon catchment and well connected to high gradient channels of bedrock rivers which promotes the transfer of suspended solids downstream. The specificity of the dataset is its high space -time resolution, especially concerning rainfall and the hydrological response which is particularly adapted to the highly spatially variable rainfall events that may occur in this region. This type of dataset is rare in scientific literature because of the quantity and type of sensors for 30 meteorology and surface hydrology. Rainfall data include continuous precipitation measured by rain gauges (5 min time step for the research network of 21 rain gauges and 5min or 1h time step for the operational network of 10 rain gauges), S-band Doppler dual-polarization radars (1 km², 5 min resolution), disdrometers (16 sensors working at 30 s or 1 min t ime step) and Micro Rain Radars (5 sensors, 100 m height resolution). Additionally, during the special observation period (SOP-1) and enhanced observation period (Sep-Dec 2012, Sep-Dec 2013) of the HyMeX (Hydrological Cycle in the Mediterranean 35 Experiment) project, two X-band radars provided precipitation measurements at very fine spatial and temporal scales (1 ha, 5min). Meteorological data are taken from the operational surface weather observation stations of Météo -France (including 2-m air temperature, atmospheric pressure, 2-m relative humidity, 10-m wind speed and direction, global radiation) at the hourly time resolution (6 stations in the region of interest). The monitoring of surface hydrology and suspended sediment is multi-scale and based on nested catchments. Three hydrometric stations measure water discharge at a 2 to 10 min time resolution. Two of these stations also measure additional physico-chemical variables (turbidity, temperature, 5 conductivity) and water samples are collected automatically during floods allowing further geochemical characterizat ion of water and suspended solids. Two experimental plots monitor overland flow and erosion at 1 min time resolution on a hillslope with vineyard. A network of 11 sensors installed in the intermittent hydrographic network continuously measures water level and water temperature in headwater subcatchments (from 0.17 km² to 116 km²) at a time resolution of 2 -5 min. A network of soil 10 moisture sensors enable the continuous measurement of soil volumetric water content at 20 min time resolution at 9 sites. Additionally, opportunistic observations (soil moisture measurements and stream gauging) were performed during floods between 2012 and 2014. The data are appropriate for understanding the rainfall variability in t ime and space at fine scales, improving areal rainfall estimations and progressing in distributed hydrological and erosion modelling

Multi-scale hydrometeorological observation and modelling for flash flood understanding

This paper presents a coupled observation and modelling strategy aiming at improving the understanding of processes triggering flash floods. This strategy is illustrated for the Mediterranean area using two French catchments (Gard and Ardeche) larger than 2000 km(2). The approach is based on the monitoring of nested spatial scales: (1) the hills-lope scale, where processes influencing the runoff generation and its concentration can be tackled; (2) the small to medium catchment scale (1-100 km(2)), where the impact of the network structure and of the spatial variability of rainfall, landscape and initial soil moisture can be quantified; (3) the larger scale (100-1000 km(2)), where the river routing and flooding processes become important. These observations are part of the HyMeX (HYdrological cycle in the Mediterranean EXperiment) enhanced observation period (EOP), which will last 4 years (2012-2015). In terms of hydrological modelling, the objective is to set up regional-scale models, while addressing small and generally ungauged catchments, which represent the scale of interest for flood risk assessment. Top-down and bottom-up approaches are combined and the models are used as "hypothesis testing" tools by coupling model development with data analyses in order to incrementally evaluate the validity of model hypotheses. The paper first presents the rationale behind the experimental set-up and the instrumentation itself. Second, we discuss the associated modelling strategy. Results illustrate the potential of the approach in advancing our understanding of flash flood processes on various scales

Observation et modélisation hydrométéorologique multi-échelles pour la compréhension des crues rapides

International audienceThis paper presents a coupled observation andmodelling strategy aiming at improving the understanding ofprocesses triggering flash floods. This strategy is illustratedfor the Mediterranean area using two French catchments(Gard and Ardèche) larger than 2000 km2. The approach isbased on the monitoring of nested spatial scales: (1) the hillslope scale, where processes influencing the runoff generationand its concentration can be tackled; (2) the small to mediumcatchment scale (1-100 km2), where the impact of the networkstructure and of the spatial variability of rainfall, landscapeand initial soil moisture can be quantified; (3) the largerscale (100-1000 km2), where the river routing and floodingprocesses become important. These observations are part ofthe HyMeX (HYdrological cycle in the Mediterranean EXperiment)enhanced observation period (EOP), which willlast 4 years (2012-2015). In terms of hydrological modelling,the objective is to set up regional-scale models, while addressingsmall and generally ungauged catchments, whichrepresent the scale of interest for flood risk assessment. Topdown and bottom-up approaches are combined and the models are used as “hypothesis testing” tools by coupling modeldevelopment with data analyses in order to incrementallyevaluate the validity of model hypotheses. The paper firstpresents the rationale behind the experimental set-up andthe instrumentation itself. Second, we discuss the associatedmodelling strategy. Results illustrate the potential of the approach in advancing our understanding of flash flood processes on various scales

Quelle stratégie d’observation et de modélisation pour l’étude des crues rapides.

Observation et modélisation hydro-météorologique multi-échelle pour la compréhension et la simulation des crues éclairs. Quels apports pour les gestionnaires de territoires et les fournisseurs de services?International audienceChaque année, spécialement à l’automne, des épisodes pluvieux intenses, dits Méditerranéens, affectent les départements du sud de la France. Ces épisodes, conduisant à des cumuls de pluie importants (quelques centaines de mm en quelques heures ou quelques jours). La figure de la diapo 1, tirée du site de Météo-France ;présente le nombre d’épisodes par an avec un cumul de pluie >150mm /jour et on voit que les départements du sud de la France, principalement le Gard, l’Ardèche et l’Hérault sont les départements les plus affectés. Ces épisodes de pluie conduisent souvent à des crues rapides, parfois dévastatrices. Les exemples récents incluent Nîmes en 1988, Vaison la Romaine en 1992, l’Aude en 1999, le Gard en 2002, le Var en 2010 ou les Alpes Maritimes en 2015, sans oublier la dizaine d’épisodes ayant affecté le sud de la France en 2014. Les conséquences de ces crues sont des submersions de bâtiments, mais aussi des coupures de route sur des petits cours d’eau coupant le réseau hydrographique. L’analyse des victimes de la crue de septembre 2002 dans le Gard a ainsi montré qu’environ la moitié des victimes, plutôt jeunes, avaient péri sur des petits bassins de taille 1000 km (Ruin et al., 2008). Sur les petits bassins, il y a très peu d’informations car, en France, la majorité des stations hydrométriques concernent des bassins de plus de 50 km et l’alerte hydrologique (Vigicrues) concerne les cours d’eau principaux

Variation in paediatric hospital antibiotic guidelines in Europe

Objective: To assess the availability and source of guidelines for common infections in European paediatric hospitals and determine their content and characteristics. Design: Participating hospitals completed an online questionnaire on the availability and characteristics of antibiotic prescribing guidelines and on empirical antibiotic treatment including duration of therapy for 5 common infection syndromes: respiratory tract, urinary tract, skin and soft tissue, osteoarticular and sepsis in neonates and children. Results: 84 hospitals from 19 European countries participated in the survey of which 74 confirmed the existence of guidelines. Complete guidelines (existing guidelines for all requested infection syndromes) were reported by 20% of hospitals and the majority (71%) used a range of different sources. Guidelines most commonly available were those for urinary tract infection (UTI) (74%), neonatal sepsis (71%) and sepsis in children (65%). Penicillin and amoxicillin were the antibiotics most commonly recommended for respiratory tract infections (RTIs) (up to 76%), cephalosporin for UTI (up to 50%) and for skin and soft tissue infection (SSTI) and bone infection (20% and 30%, respectively). Antistaphylococcal penicillins were recommended for SSTIs and bone infections in 43% and 36%, respectively. Recommendations for neonatal sepsis included 20 different antibiotic combinations. Duration of therapy guidelines was mostly available for RTI and UTI (82%). A third of hospitals with guidelines for sepsis provided recommendations for length of therapy. Conclusions: Comprehensive antibiotic guideline recommendations are generally lacking from European paediatric hospitals. We documented multiple antibiotics and combinations for most infections. Considerable improvement in the quality of guidelines and their evidence base is required, linking empirical therapy to resistance rates.</p