An attempt was made to compensate for the lack of long hydrological time series and the lack of information on maximum streamflow in the Alzette River basin (Luxembourg) via the regionalization of stormflow coefficients. Streamflow data recorded since 1995 with a very dense streamgauge network allowed the determination of maximum stormflow coefficients in 18 sub-basins of the Alzette. The stormflow coefficients were then regionalized via stepwise multiple regression analysis for 83 different sub-basins of the Alzette. Combined with 10-year daily rainfall heights (statistical estimation), this regionalization allowed the spatial variability of storm runoff in the Alzette basin to be mapped, thus providing a view of hazard and risk-producing areas, as well as of risk-exposed areas. In a basin with little historical hydrological information this technique can help identify areas where storm runoff reducing measures should be applied from the outset. Key words stormflow coefficients; regionalization; hazard mapping; Alzette hasin, Luxembourg Utilisation de coefficients d'écoulement de crue régionalisés en vue de la cartographie de l'aléa hydro-climatologique Résumé Cette étude présente une tentative de pallier le manque de longues séries d'observations hydrologiques dans le bassin de l'Alzette (Luxembourg) à l'aide d'une régionalisation de coefficients d'écoulement de crue. Les observations hydrologiques réalisées depuis 1995 dans 18 sous-bassins de l'Alzette ont permis de déterminer des coefficients d'écoulement de crue maximum (K nrdX ). Les K m3X régionalisés à l'aide d'une régression multiple par étapes ont été déterminés pour 83 sous-bassins de l'Alzette. La superposition des coefficients d'écoulement de crue régionalisés et d'une pluie journalière théorique décennale a permis d'établir une carte détaillée de la variabilité spatiale de l'écoulement de crue dans le bassin de l'Alzette. Cette carte permet de distinguer clairement les zones productrices des aléas et des risques hydrologiques des zones exposées aux risques hydrologiques. Dans un bassin où l'historique hydrologique fait défaut, cette technique permet d'identifier les zones où les mesures visant à réduire l'écoulement de crue devraient être appliquées prioritairement. Mots clefs coefficient d'écoulement de crue; régionalisation; cartographie de l'aléa; bassin de l'Alzette, Luxembourg

This study sought to establish a quantitative functional hydrogeomorphological typology of river reference types in the French Upper Rhine basin that would meet the requirements of the European Water Framework Directive, defined in terms of hydromorphological quality and prospects for river restoration. Four ecoregions (i.e. hydrogeomorphic units) were delineated by expert opinion and validated by independent variables (i.e. 1·5-year peak discharge, comparison of 10-year daily flow and low flow, valley bottom morphology and specific stream power). A data set of 31 quantitative and qualitative variables for 187 field sites was established and analysed. Agglomerative hierarchical clustering (AHC) of the quantitative variables and principal component analysis (PCA) provided hierarchy and grouping of variables. Multiple correspondence analysis (MCA) confirmed these results, discriminating sites into seven groups, but did not lead to a functional typology due to important overlapping between groups and variability within groups. A definitive quantitative typology was obtained through AHC and discriminant analysis with cross-validation computed separately in each ecoregion. Results for two ecoregions, 'marly calcareous loess-covered hills' and 'crystalline Vosges mountains', are given as examples. Finally, the classification of the sites is extended to the whole river network by river sectorization, each homogeneous river section being classified to one category on the basis of the preceding classification of sites. Methodological implications regarding river classification are also given.WFD only suggests possible criterion for river classification (altitude, geology, energy, valley and channel morphology, sediment transport etc.). Each country has to elaborate its own operational method.A large array of methods for hydrogeomorphological typologies can be found in the literature. This range of approaches is related to various objectives, which are often linked to specific management problems, various scales and different geographical settings (Kondolf et al., 2003). Many authors have tried to highlight the principles and results of these numerous approaches through several bibliographic syntheses (Hawkes

The knowledge of rainfall patterns is a key issue for regionalization in hydroclimatic studies. In mountainous areas, the sparsity of the measurement network and the complexity of relationships between rainfall and topography make an accurate and reliable spatialization of rainfall amounts at the regional scale difficult. The purpose of this paper is to present an objective, analytical and automatic model of quantification and mapping of orographic rainfall applied to the north-eastern part of France but also applicable in other complex terrain. PLUVIA distributes point measurements of monthly, annual and climatological rainfall to regularly spaced grid cells through a multiple regression analysis of rainfall versus morpho-topographic parameters derived from a digital elevation model. The use of an omnidirectional parameterization of the topography induced by a windowing technique allows better account to be taken of the synopticscale weather systems generating the different rainfall quantities of interest and the spatial scale of orographic effects. It also provides a more physical interpretation of geographical and topographical parameters selected for spatial estimation. The application relies on a network of more than 150 rain gauges spread over 30 000 km 2 and concerns monthly to several yearly amounts of a sequence of 20 years. Advantages and limitations of the PLUVIA system are compared with those of two commonly used methods of multi-variate geostatistics: kriging with external drift and extended collocated co-kriging.

High spatio-temporal resolution monitoring has only been progressively developed in the Rhine-Meuse basins over the last few decades. As a consequence, basic hydrological information can be very scarce in some areas. In regions which are homogeneous from a hydroclimatological and physiogeographical point of view, hydrographs can be reproduced via regionalized hydrological models, provided that climatological observation series are available.The Alzette river basin, monitored since the mid-1990s by a very dense hydroclimatological observation network, had been chosen in the framework of the IRMA-SPONGE project FRHYMAP for transposing the conceptual hydrological models HRM and SOCONT and regionalizing their parameters. The regionalized models were to be used both for extending the currently available runoff series and evaluating runoff in neighbouring non-monitored basins.The 16 monitored sub-basins of the Alzette, reflecting the physiogeographical diversity of the study area, were divided into two subsets, serving for both the calibration and the validation procedures. Once the transposition of the models to the Alzette basin had been successfully assessed, their parameters were linked to the physiogeographical characteristics of the sub-basins. The performance of the thus regionalized models was assessed via a validation on a subset of basins that had not been retained for the elaboration of the regional parameter sets.The transposition of the HRM and SOCONT model to the Alzette river basin was completed successfully. Results overall proved to be satisfying, with the HRM model performing equally well for low flows and high flows, while the SOCONT model showed best results for high flows and a systematic overestimation of the mean discharge. Both models proved to be adequate for evaluating daily runoff in non-monitored basins of the Grand-Duchy of Luxembourg, helping thus to counterbalance the considerable lack of hydrological observation series in this part of the Rhine basin.

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