A physically-based parsimonious hydrological model for flash floods in Mediterranean catchments

A spatially distributed hydrological model, dedicated to flood simulation, is developed on the basis of physical process representation (infiltration, overland flow, channel routing). Estimation of model parameters requires data concerning topography, soil properties, vegetation and land use. Four parameters are calibrated for the entire catchment using one flood event. Model sensitivity to individual parameters is assessed using Monte-Carlo simulations. Results of this sensitivity analysis with a criterion based on the Nash efficiency coefficient and the error of peak time and runoff are used to calibrate the model. This procedure is tested on the Gardon d'Anduze catchment, located in the Mediterranean zone of southern France. A first validation is conducted using three flood events with different hydrometeorological characteristics. This sensitivity analysis along with validation tests illustrates the predictive capability of the model and points out the possible improvements on the model's structure and parameterization for flash flood forecasting, especially in ungauged basins. Concerning the model structure, results show that water transfer through the subsurface zone also contributes to the hydrograph response to an extreme event, especially during the recession period. Maps of soil saturation emphasize the impact of rainfall and soil properties variability on these dynamics. Adding a subsurface flow component in the simulation also greatly impacts the spatial distribution of soil saturation and shows the importance of the drainage network. Measures of such distributed variables would help discriminating between different possible model structures

Parameter regionalization for a process-oriented distributed model dedicated to flash floods

This contribution is one of the first studies about the regionalization of parameter sets for a rainfall-runoff model process-oriented and dedicated to flash floods. MARINE model performances are tested on a large database of 117 flash floods occurred during the last two decades in the French Mediterranean region. Given the scarcity of flash flood data, the dataset used in this study represents a large sample of hydrology and landscapes from Pyrenean, Mediterranean, Cévennes-Vivarais and Provence regions. Spatial proximity and similarity approaches with several combinations of descriptors are tested. Encouraging results are obtained with two similarity approaches based on physiographic descriptors with two and three donor catchments. There is only a small decrease of performance of 10 from cal/val to regionalization for these two methods. For 13 catchments out of 16 there is at least one flood event simulated with rather good performance. This study highlights the importance of hydrological information that is available in calibration events for a gauged catchment and from donor catchment(s) for regionalization. Moreover it is found that regionalization is easier for catchments with an apparently more regular behaviour. The most sensitive parameter of MARINE model, CZ, controlling soil volume and water balance, is rather well constrained by the two similarity approaches thanks to bedrock descriptors

Analysis of flash flood-triggering rainfall for a process-oriented hydrological model

We propose an extended study of recent flood-triggering storms and resulting hydrological responses for catchments in the Pyrenean foothills up to the Aude region. For hydrometeorological sciences, it appears relevant to characterize flash floods and the storm that triggered them over various temporal and spatial scales. There are very few studies of extreme storm-caused floods in the literature covering the Mediterranean and highlighting, for example, the quickness and seasonality of this natural phenomenon. The present analysis is based on statistics that clarify the dependence between the spatial and temporal distributions of rainfall at catchment scale, catchment morphology and runoff response. Given the specific space and time scales of rainfall cell development, we show that the combined use of radar and a rain gauge network appears pertinent. Rainfall depth and intensity are found to be lower for catchments in the Pyrenean foothills than for the nearby Corbières or Montagne Noire regions. We highlight various hydrological behaviours and show that an increase in initial soil saturation tends to foster quicker catchment flood response times, of around 3 to 10 h. The hydrometeorological data set characterized in this paper constitutes a wealth of information to constrain a physics-based distributed model for regionalization purposes in the case of flash floods. Moreover, the use of diagnostic indices for rainfall distribution over catchment drainage networks highlights a unimodal trend in spatial temporal storm distributions for the entire flood dataset. Finally, it appears that floods in mountainous Pyrenean catchments are generally triggered by rainfall near the catchment outlet, where the topography is lower

Analyse de défaillance de nouvelles technologies microélectroniques (nouvelles approches dans la méthodologie de préparation d'échantillon)

Dans le développement des technologies microélectroniques, l analyse de défaillance permet par l étude des mécanismes de défaillance potentiels de définir des solutions correctives. La mise en œuvre des techniques de localisation et d observation des défauts requiert une méthodologie, dont l étape clé est la préparation d échantillons. Celle-ci doit continuellement évoluer pour s adapter aux innovations technologiques qui introduisent de nouveaux matériaux, et augmentent la complexité des composants assemblés. Cette thèse s est intéressée à la méthodologie de préparation d échantillons pour l analyse de défaillance de deux familles de produits : les produits discrets et IPAD, et les micro-batteries. Pour les produits discrets et IPAD, une optimisation de la méthodologie existante a été réalisée en intégrant de nouvelles approches, développées pour résoudre des cas jusqu alors en échec. Pour les micro-batteries, les matériaux utilisés et leur architecture ont nécessité une remise en question complète de la méthodologie de préparation d échantillon.In the development of microelectronic technologies, the failure analysis makes it possible to define corrective actions thanks to the understanding of the failure mechanism. In order to define the most adequate localization and observation techniques to use, a failure analysis flow is required. The sample preparation is a key step of this flow. This flow must continuously evolve to take into account the technological innovations that introduce new materials, and increase the complexity of assembled components. This work concerned the sample preparation flow for the failure analysis of two product families : the discrete products and IPAD, and the micro-batteries. Concerning the discrete products and the IPAD, an optimization of the current flow was performed with the integration of new approaches developed to solve failed cases. For the micro-batteries, the used materials and their architecture required an entire reappraisal of the sample preparation flow.BORDEAUX1-Bib.electronique (335229901) / SudocSudocFranceF

Profiles of learner readers and their early literacy skills and environmental predictors: a large-scale longitudinal study from preschool to grade 1

As part of the French national cohort ELFE, a two-year longitudinal study was conducted and children’s literacy skills were assessed twice (N = 2,767), namely at the end of preschool (t1) and at the end of Grade 1 (t2). At t1, letter-name knowledge (LNK), phonological skills (PhoSk) and vocabulary were assessed and at t2, phonemic segmentation, word reading, listening and reading comprehension. Latent profile analyses conducted at t2 resulted in five profiles, ranging from good readers (48.8%), to average readers above the mean (16.2%), readers with very low phonological awareness skill (8.2%), poor readers with low reading comprehension skill (19.4%), and poor readers with general difficulties (7.4%). Two early literacy skills (LNK and PhoSk) and two environmental variables (parents’ educational level and household income) constituted good predictors of membership of a profile. However, home literacy practices also predicted membership of the good reader/poor reader profiles, albeit at a lower level

Évaluation des connaissances précoces prédictives de l’apprentissage de la lecture en grande section de maternelle

Le premier objectif de ce travail, mené auprès de plus de 3000 élèves de grande section de maternelle, était de valider une batterie de tests évaluant les compétences prédictives de l’acquisition de la lecture dans ses deux composantes, identification de mots écrits et compréhension. Pour cela, les qualités métrologiques des épreuves expérimentales en reconnaissance de lettres, en habiletés phonologiques, en vocabulaire et en compréhension orale ont fait l’objet d’un examen. Le second objectif était d’identifier des profils d’élèves et les difficultés des plus faibles (par l’analyse des erreurs). La conclusion souligne l’intérêt des sessions précoces d’évaluation afin de prévenir les difficultés avec des aides ciblées à l’apprentissage de la lecture en CP.The first goal of this study, conducted among more than 3000 kindergarten children, was to validate a series of tests which assess predictive skills necessary to master reading in two main components, word recognition and language comprehension. For that purpose, measurements from experimental tasks in letter recognition, phonological skills, vocabulary and comprehension were examined. The second aim was to specify pupils’ profiles and the difficulties of the poorest pupils (through error analysis). The conclusion emphasized the benefit of early assessment sessions, in order to prevent difficulties with targeted support for learning to read

Les apports des épreuves projectives dans les évaluations de l’autisme

L’auteur montre la nécessité de l’investigation du fonctionnement psychique des enfants autistes. Un bref historique des différents courants théoriques qui se sont intéressés à l’autisme depuis Kanner est présenté. L’apport des épreuves projectives et leur interprétation psycho dynamique est examiné dans sa complémentarité avec les épreuves cognitives. Cet apport constitue un éclairage pertinent des modalités de construction de la personnalité des sujets autistes. Il représente une évolution dans la connaissance des mécanismes autistiques et des potentialités de transformations de ceux-ci

Relations among specific linguistic, general cognitive skills and difficulties in word identification with very poor readers: a comparative study.

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