Quels liens entre climatologie, occupation des sols et inondations dans le bassin versant de l'Yzeron (ouest Lyonnais) ? Apport de l'analyse conjointe de données hydroclimatiques et d'images satellitaires très haute résolution

Le bassin versant de l'Yzeron, situé en périphérie immédiate de la ville de Lyon, est un bassin représentatif des bassins versants périurbains français. Il connaît, depuis les années 1970, une augmentation importante de son urbanisation. Ces dernières années, des crues importantes, entraînant des inondations à l'aval du bassin versant ont marqué les esprits, posant la question de l'impact des modifications de l'occupation des sols dans le bassin versant sur le régime des crues. Dans cet article, nous utilisons l'analyse combinée de données hydroclimatiques (pluie, température, évapotranspiration de référence -ET0, débits) et de cartes de l'occupation des sols dérivées d'images satellites SPOT à haute et très haute résolution pour aborder cette question. L'analyse des débits montre l'existence d'une évolution du régime des crues, avec une augmentation significative des crues sub -seuils pour des durées de 1,5h, 3h, 6h, 12h et 36h sur la période 1970-2010. L'analyse de l'échantillon de crues obtenue par cette analyse débit-durée-fréquence montre que les crues les plus importantes sont plutôt liées à des épisodes ayant conduit à un cumul de pluie important (> 80 mm en quelques jours). Une corrélation significative est aussi obtenue entre débit de base et coefficient de ruissellement, ce qui montre que ces crues peuvent être associées à des écoulements sur surfaces saturées. Les évolutions du climat (pluviométrie, température, ET0) ne permettent pas d'expliquer l'augmentation des crues observées. En revanche, l'occupation des sols entre 1990 et 2008 montre une augmentation des sur faces imperméables qui passent de 15,2 % de la surface totale du bassin en 1990 à 18,2 % en 1999 et 22,6 % en 2008. Cette évolution de l'imperméabilisation est mise en regard de l'accroissement de la population du bassin sur cette même période. Enfin, nous illustrons la réponse hydrologique du bassin versant avec deux épisodes pour lesquels le rôle de l'occupation des sols est différent. Le premier, celui du 02/12/2003 est typique d'une réponse par saturation du bassin, avec une contribution majeure des zon es rurales, suite à des cumuls pluviométriques importants. Le second, celui du 09/08/2009 représente un orage d'été, très court mais avec des intensités importantes, conduisant essentiellement à une réponse rapide des zones urbaines et pour lequel l'occupation des sols joue un rôle majeur

Impact de l'urbanisation sur le cycle hydrologique dans un bassin versant periurbain. Application au bassin de l’Yzeron - ouest lyonnais, France

International audienceL’urbanisation croissante, en particulier dans les zones périphériques aux grandes villes (zones périurbaines) a des conséquences sur le cycle hydrologique en modifiant l’infiltrabilité des sols, la recharge des nappes, ainsi que les chemins naturels de l’eau via les différents réseaux (routiers, eau potable, assainissement). Une modélisation à l'aide du modèle hydrologique distribué J2000 est mise en ½uvre sur le bassin versant de l’Yzeron, en périphérie de Lyon, représentatif des bassins périurbains français. Nous montrons en particulier que l’urbanisation modifie les composantes des écoulements en accroissant le ruissellement de surface au détriment des écoulements de base ou de sub-surface (comparaison de simulations s’appuyant sur des cartes d’occupation du sol de 1990, 1999, 2008). La prise en compte des réseaux d’assainissement et des déversoirs d’orage dans la modélisation permettra d’améliorer la simulation des bilans hydrologiques dans le bassin. / Urban growth, in particular close to big cities impacts the hydrological cycle by modifying soil infiltration capacity, groundwater recharge, but also by modifying natural water pathways due to the various networks associated with urbanization (roads, drinkable and sewer networks). The distributed hydrological model J2000 is set up in the Yzeron catchment, close to Lyon city. We show that urban growth modifies the flow components by increasing surface runoff and decreasing base and sub-surface flows (comparison of simulations based on past land use mapping of 1990, 1999, 2008). The inclusion of sewer networks and sewer overflow devices in the model will improve the water balance simulations of the catchment

Bouches-du-Rhône. Au large de Marseille. Sondage au port de l’île de Pomègues, EA 3321

International audienceNotice scientifique d'opération d'archéologie sous-marine, 201

Bouches-du-Rhône. Au large de Marseille. Le port de l’île de Pomègues. Sondage à la pointe de la Capitainerie, EA 1290

Notice scientifique d'opération d'archéologie sous-marine, 2012Notice scientifique d'opération d'archéologie sous-marine, 201

Investigating the impact of two decades of urbanization on the water balance of the Yzeron peri-urban catchment, France

International audienceThis paper addresses the impact of 18 years of urbanization (1990-2008) on the Yzeron meso-scale peri-urban catchment (150 km²), located close to Lyon, France. A simplified version of the distributed hydrological model J2000 was used to perform long term simulations at a daily time step for several land use scenarios. These scenarios were derived from satellite SPOT images from years 1990, 1999 and 2008. The corresponding land use maps were classified into 5 classes depending on the percentage of impervious surfaces and the dominant non-impervious land use (agriculture or forest). The paper presents the methodology for the model setup and the simulation results for the main water balance components of the catchment: total runoff, runoff components, evapotranspiration and soil moisture. The results highlight the change of the catchment seasonal response from 1990 to 2008, mainly due to a change of the respective contributions of groundwater flow / surface runoff (+ 92% / - 28%, respectively). Monthly mean summer discharge unexpectedly appears to be higher in summer. It is provided by intermittent surface runoff generated by summer storm events. As surface runoff generated on urban surfaces is likely to carry a wide range of contaminants, this has a potential large impact on water quality

Bouches-du-Rhône. Au large de Marseille. Le port de Pomègues

Notice scientifique d'opération d'archéologie sous-marine, 201

Three very high resolution optical images for land use mapping of a suburban catchment: input to distributed hydrological models

International audienceUrbanization and other modifications of land use affect the hydrological cycle of suburban catchments. In order to quantify these impacts, the AVuPUR project (Assessing the Vulnerability of Peri-Urban Rivers) is currently developing a distributed hydrological model that includes anthropogenic features. The case study is the Yzeron catchment (150 km2), located close to Lyon city, France. This catchment experiences a growing of urbanization and a modification of traditional land use since the middle of the 20th century, resulting in an increase of flooding, water pollution and river banks erosion. This contribution discusses the potentials of automated data processing techniques on three different VHR images, in order to produce appropriate and detailed land cover data for the models. Of particular interest is the identification of impermeable surfaces (buildings, roads, and parking places) and permeable surfaces (forest areas, agricultural fields, gardens, trees. . . ) within the catchment, because their infiltration capacity and their impact on runoff generation are different. Three aerial and spatial images were acquired: (1) BD Ortho IGN aerial images, 0.50 m resolution, visible bands, may 5th 2008; (2) QuickBird satellite image, 2.44 m resolution, visible and near-infrared bands, august 29th 2008; (3) Spot satellite image, 2.50 m resolution, visible and near-infrared bands, September 22nd 2008. From these images, we developed three image processing methods: (1) a pixel-based method associated to a segmentation using Matlab®, (2) a pixel-based method using ENVI®, (3) an object-based classification using Definiens®. We extracted six land cover types from the BD Ortho IGN (visible bands) and height classes from the satellite images (visible and near infrared bands). The three classified images are resampled in the same low resolution of 2.5 m and compared in order to evaluate the accuracy of different image processing methods and to determine for each cover type, the more appropriate image and/or method. This comparison provides hydrologists with a synthetic land cover map. Four parameters affect the accuracy of land cover mapping: firstly the addition of the NIR band improves vegetation classification such as the distinction between coniferous forest and broad-leaved forest. Moreover the intensity of chlorophyllian activity allows us to characterize the use of agricultural fields. Secondly, the images were taken at three dates in the agricultural calendar. This multi-date data allows the discrimination between permanently vegetalized pastures, and temporarily bare crops, a useful information for hydrologists who study surfaces hydraulic properties. Thirdly, the high resolution of the BD Ortho IGN image emphasizes the heterogeneity inside the spatial entities. Thus, in urbanised areas, high-resolution imagery allows the precise identification of objects > 5 m2 and consequently the quantification of impervious and pervious surfaces. However, the continuity of forest areas is not maintained because of the presence of small entities with sparser tree cover that were classified as herbaceous areas. Finally, image characteristics are more crucial than classification methods for the accuracy of land cover mapping. However, object based approach improves the classification of mixed pixels on the edge between different objects. It's particularly true for buildings and roads

Deleterious effects of thermal and water stresses on life history and physiology: a case study on woodlouse

We tested independently the influences of increasing temperature and decreasing moisture on life history and physiological traits in the arthropod  Armadillidium vulgare. Both increasing temperature and decreasing moisture led reproductive success to decrease. While the density of immune cells decreased and the β-galactosidase activity increased with increasing temperature and decreasing moisture, which suggests a negative impact of these stressors on individual performance, increased temperature and decreased moisture affected differently the other biomarkers conjuring different underlying mechanisms depending on the stress applied. Our findings demonstrate overall a negative impact of high temperature and low moisture on woodlouse welfare. Changing temperature or moisture had slightly different effects, illustrating the need to test further the respective role of each of these key components of climate change on organisms to predict more reliably the future of our ecosystems

Skeletal Muscle Biopsy Analysis in Reducing Body Myopathy and Other Fhl1-related Disorders

FHL1 mutations have been associated with various disorders that include reducing body myopathy (RBM), Emery-Dreifuss-like muscular dystrophy, isolated hypertrophic cardiomyopathy, and some overlapping conditions. We report a detailed histochemical, immunohistochemical, electron microscopic, and immunoelectron microscopic analyses of muscle biopsies from 18 patients carrying mutations in FHL1: 14 RBM patients (Group 1), 3 Emery-Dreifuss muscular dystrophy patients (Group 2), and 1 patient with hypertrophic cardiomyopathy and muscular hypertrophy (Group 2). Group 1 muscle biopsies consistently showed RBs associated with cytoplasmic bodies. The RBs showed prominent FHL1 immunoreactivity whereas desmin, alpha B-crystallin, and myotilin immunoreactivity surrounded RBs. By electron microscopy, RBs were composed of electron-dense tubulofilamentous material that seemed to spread progressively between the myofibrils and around myonuclei. By immunoelectron microscopy, FHL1 protein was found exclusively inside RBs. Group 2 biopsies showed mild dystrophic abnormalities without RBs; only minor nonspecific myofibrillar abnormalities were observed under electron microscopy. Molecular analysis revealed missense mutations in the second FHL1 LIM domain in Group 1 patients and ins/del or missense mutations within the fourth FHL1 LIM domain in Group 2 patients. Our findings expand the morphologic features of RBM, clearly demonstrate the localization of FHL1 in RBs, and further illustrate major morphologic differences among different FHL1-related myopathies