The thesis is concerned with development of efficient regional frequency analysis (RFA) approaches to estimate quantiles of hydrometeorological events. The estimates are necessary for various applications in water resources engineering. The classical approach to estimate quantiles involves fitting frequency distribution to at-site data. However, this approach cannot be used when data at target site are inadequate or unavailable to compute parameters of the frequency distribution. This impediment can be overcome through RFA, in which sites having similar attributes are identified to form a region, and information is pooled from all the sites in the region to estimate the quantiles at target site. The thesis proposes new approaches to RFA of precipitation, meteorological droughts and floods, and demonstrates their effectiveness. The approach proposed for RFA of precipitation overcomes shortcomings of conventional approaches with regard to delineation and validation of homogeneous precipitation regions, and estimation of precipitation quantiles in ungauged and data sparse areas. For the first time in literature, distinction is made between attributes/variables useful to form homogeneous rainfall regions and to validate the regions. Another important issue is that some of the attributes considered for regionalization vary dynamically with time. In conventional approaches, there is no provision to consider dynamic aspects of time varying attributes. This may lead to delineation of ineffective regions. To address this issue, a dynamic fuzzy clustering model (DFCM) is developed. The results obtained from application to Indian summer monsoon and annual rainfall indicated that RFA based on DFCM is more effective than that based on hard and fuzzy clustering models in arriving at rainfall quantile estimates. Errors in quantile estimates for the hard, fuzzy and dynamic fuzzy models based on the proposed approach are shown to be significantly less than those computed for Indian summer monsoon rainfall regions delineated in three previous studies. Overall, RFA based on DFCM and large scale atmospheric variables appeared promising. The performance of DFCM is followed by that of fuzzy and hard clustering models. Next, a new approach is proposed for RFA of meteorological droughts. It is suggested that homogeneous precipitation regions have to be delineated before proceeding to develop drought severity - areal extent - frequency (SAF) curves. Drought SAF curves are constructed at annual and summer monsoon time scales for each of the homogeneous rainfall regions that are newly delineated in India based on the proposed approach. They find use in assessing spatial characteristics and frequency of meteorological droughts. It overcomes shortcomings associated with classical approaches that construct SAF curves for political (e.g., state, country) and physiographic regions (e.g., river basin), based on spatial patterns of at-site values of drought indices in the study area, without testing homogeneity in rainfall. Advantage of the new approach can be noted especially in areas that have significant variations in temporal and spatial distribution of precipitation (possibly due to variations in topography, landscape and climate). The DFCM is extended to RFA of floods, and its effectiveness in prediction of flood quantiles is demonstrated by application to Godavari basin in India, considering precipitation as time varying attribute. Six new homogeneous regions are formed in Godavari basin and errors in quantile estimates based on those regions are shown to be significantly less than those computed based on sub-zones delineated in Godavari basin by Central Water Commission in a previous study.

Connaître la probabilité d'occurrence des aléas océano-météorologiques extrêmes est fondamental pour prévenir les risques de submersion marine en zone côtière ou concevoir des aménagements côtiers, portuaires ou des plate-formes offshore. Notamment, le concept de niveau de retour est fréquemment utilisé en ingénierie côtière pour dimensionner des ouvrages de protection. Ces niveaux, dont les périodes de retour d'intérêt se situent généralement entre 100 et 1000 ans, sont habituellement estimés par une analyse statistique locale, à partir de données observées en un site unique. Cependant, la période d'observation est généralement limitée, de sorte que les incertitudes associées aux niveaux de retour élevés sont importantes. L'analyse régionale représente une solution possible pour réduire les incertitudes inhérentes aux analyses locales. Le principe est d'exploiter l'information de sites d'observation provenant d'une région homogène, où les extrêmes sont supposés avoir un comportement probabiliste similaire. L'analyse régionale peut ainsi estimer les niveaux de retour de manière plus fiable qu'une analyse locale. Cependant, son application dans le domaine maritime étant relativement limitée et récente, différentes questions méthodologiques de meurent non-Résolues, comme la formation des régions homogènes ou le traitement de la dépendance entre sites. L'objectif scientifique de la thèse est donc d'approfondir certains points méthodologiques de l'analyse régionale, dans le cadre des aléas maritimes extrêmes. Les points suivants sont abordés en particulier :• Échantillonnage des extrêmes pour l'analyse régionale, à partir des tempêtes détectées via une procédure de declustering spatio-Temporel.• Formation de régions homogènes à partir d'une méthode basée sur l'identification des empreintes typiques des tempêtes.• Prise en compte de la dépendance entre sites d'observation, à travers la construction d'un modèle permettant par exemple d'évaluer la durée effective régionale d'observation ou la période de retour régionale d'une tempête.• Spécification et estimation de la loi régionale, avec incorporation des co-variables influentes, comme la saison d'occurrence ou la direction de provenance pour les vagues.• Comparaison entre analyses locale et régionale, notamment à travers les incertitudes sur les estimations des extrêmes et la capacité à modéliser les horsains présumés.Ces aspects sont illustrés sur des données de hauteurs significatives de vagues et de surcotes de pleine mer, dans la zone Atlantique Nord-Est, Manche et Mer du Nord.Parallèlement, l'objectif applicatif de ces travaux est de contribuer à garantir la sûreté des ouvrages EDF contre le risque de submersion marine. Ceci peut être réalisé grâce à l'exploration de nouvelles techniques d'estimation des aléas maritimes extrêmes telles que l'analyse régionale, qui permet notamment une meilleure prise en compte des horsains. / The knowledge of the probability of occurrence of oceano-Meteorological extremes is essential to prevent risks of coastal flooding or to build coastal protections or off-Shore structures. In particular, the concept of return level is frequently used in coastal engineering to design protection structures. These levels, whose return periods of interest generally lie between 100 and 1000 years, are usually estimated by a local statistical analysis, from data observed at a unique site. However, the period of observation is generally limited, which can imply high uncertainties for high return levels. Regional frequency analysis is a possible solution to reduce uncertainties inherent to local analyses. The principle is to exploit the information of sites of observation from a homogeneous region, where extremes are supposed to share a similar probabilistic behavior. Thus, regional frequency analysis can estimate return levels more accurately than a local analysis. However, its application to the marine field being relatively limited and recent, several methodological questions are still unsolved, such as the formation of homogeneous regions or the dependence between sites. The scientific objective of this thesis is thus to develop some methodological points of regional frequency analysis, in the framework of extreme marine hazards. The following questions are tackled:• Sampling of extremes for regional analysis, from the storms detected through a spatiotemporal declustering procedure.• Formation of homogeneous regions from a method based on the identification of the typical storms footprints.• Consideration of the dependence between sites of observation, through the building of a model allowing, for example, to assess the regional effective duration or the regional return period of a storm.• Specification and estimation of the regional distribution, with the incorporation of influent covariables, such as the season of occurrence or the direction for waves.• Comparison between regional and local analyses, especially through the uncertainties on the estimated extremes and the ability to model the potential outliers. These aspects are illustrated on significant wave height data and skew surge data located in the Northeast Atlantic, the Eastern Channel and the North Sea. At the same time, the industrial objective of this work is to contribute to guarantee the safety of EDF structures against the risk of coastal flooding. This can be achieved through the exploration of new techniques of estimation of extreme marine hazards such as regional frequency analysis, which allows in particular a better representation of outliers

京都大学 / 0048 / 新制・課程博士 / 博士(工学) / 甲第18562号 / 工博第3923号 / 新制||工||1603(附属図書館) / 31462 / 京都大学大学院工学研究科社会基盤工学専攻 / (主査)教授 寶 馨, 教授 中北 英一, 教授 田中 茂信 / 学位規則第4条第1項該当 / Doctor of Philosophy (Engineering) / Kyoto University / DFAM

Conselho Nacional de Desenvolvimento Científico e Tecnológico / The knowledge of intense precipitation is primordial in hydraulic structures design. However, the determination of this variable stumbles on its monitoring deficiency. Thus, the use of statistical methods, such as regional frequency analysis, aims to support the determination or caracterization of these precipitation. The purpose of this study was to identify behavioral patterns of daily intense precipitation that allows the estimative of design storm in ungauged basins. The study was directed to the southernmost state of Brazil, Rio Grande do Sul (RS), a region with one of the world highest intense precipitation events. The hydrometeorological monitoring of the region is accomplished mainly by the National Water Agency (ANA). In this study were analyzed 1070 rain gauges, containing records between 1912 and 2014. Firstly, the consistency procedure was performed, by pre-analyzing and classifying the precipitation events (adapted Z score), selection of annual maximum series of continuous periods, and punctual validation. In the second stage, the maximum events were submitted to a regional frequency analysis, based on the regionalization method of Hoskins e Wallis. Finally, was demonstrated a precipitation estimative method for ungauged basins. The results of the pre-analysis characterized the periods of greatest temporal and spatial continuity from the available records, which occurred in the decade of 1970. On the other hand, this period has the greatest number of monitoring inconsistencies. The classification of the precipitation records indicated possible inconsistent data. Parallel to this, the selection process allowed the elaboration of maximum series of 15 and 30 years, uninterrupted, which occurred between 1963 and 1977, and between 1971 and 2000, with 91 and 40 gauges, respectively. Among the series, 163 events were indicated as possibly inconsistent data, which then were analyzed by the punctual validation, resulting in more trustworthy maximum series. The results of the maximum series regionalization indicated that RS has from two to three regions of homogenous behavior. The estimative from the 15 years series generated the most accurate values for Return Periods (T) lower than ten years. In opposite, the 30 years series resulted in better approximations for T greater than 20 years. Nevertheless, the quality of the estimates is prejudiced in the regions with a low density of gauges. The processes applied to the consistency analysis were effective, and the suggested methodology demonstrated to be appropriate and flexible. / O conhecimento das precipitações intensas é primordial no projeto de estruturas hidráulicas. No entanto, a determinação desta variável esbarra nas deficiências do seu monitoramento. Assim, o emprego de métodos estatísticos, como análise de frequência regional visa auxiliar na determinação ou caracterização dessas precipitações. O objetivo deste estudo foi identificar padrões comportamentais das precipitações intensas diárias que possibilitem estimar chuvas de projetos em locais sem informações. O estudo foi direcionado ao estado do Rio Grande do Sul, Brasil, cujas precipitações intensas estão entre as maiores do mundo. Seu monitoramento hidrometeorológico é efetuado, principalmente, pela Agência Nacional de Águas (ANA). Foram analisadas 1070 estações pluviométricas, com registros entre os anos de 1912 a 2014. Foi realizado, primeiramente, o processo de consistência, que contou com: pré-análise e classificação dos eventos de precipitação (Z-score adaptado), seleção de séries de máximos anuais de períodos contínuos, e validação pontual. Na segunda etapa, os eventos de máximos foram submetidos a uma análise regional de frequências, baseada no método de regionalização de Hosking e Wallis, em seguida, foi demostrada uma forma de estimar as precipitações em locais sem dados. Os resultados da pré-análise caracterizaram os momentos de maior continuidade temporal e espacial dos registros disponíveis, os quais ocorreram em meados da década de 70. Por outro lado, este período também foi o com maior número de inconsciências no monitoramento. A classificação dos registros de precipitação indicou possíveis dados inconsistentes. Paralelo a isto, o processo de seleção permitiu a construção de séries de máximos de 15 e 30 anos, ininterruptos, os quais ocorreram entre 1963 a 1977 e, 1971 a 2000, com 91 e 40 estações, respectivamente. Dentre estas séries, 163 eventos foram indicados como possíveis dados inconsistentes, os quais passaram pelo processo de validação pontual, resultando em séries de máximos de maior confiabilidade. O resultado da regionalização das séries de máximos demonstrou que o Estado possui de duas a três regiões de comportamento homogêneo. As estimativas produzidas pelas regiões formadas pelas séries de 15 anos produziram valores mais precisos para tempos de retorno (Tr) inferior a dez anos. Já as séries de 30 anos resultaram numa melhor precisão nas estimativas com Tr superior a 20 anos. Contudo, a qualidade das estimativas é prejudicada nas regiões em que a densidade de estações é baixa. Os processos empregados na análise de consistência foram eficientes, e a metodologia sugerida demonstrou ser flexível e aplicável.

This study aimed at describing the characteristics of daily precipitation and discharge extremes in the Adige river basin at the city of Trento. Annual maximum series for the period 1975−2014 were analyzed in terms of trends, seasonality indices and L-moments. A Mann-Kendall trend analysis showed a weak but significant signal of decreasing ex-tremes; the percentages of sites with significant negative trends were overall larger than the significance levels. Precipitation extremes were characterized primarily by autumn storms, while floods had a stronger seasonality with peaks occurring predominantly in June and July which indicated that the timing not solely explained by rainfall maxima. The Adige basin was found to be a homogenous region with respect to precipitation, but the results did not support a corresponding assumption for discharge. A regional fre-quency analysis was performed for precipitation data and found both the Pearson type III and generalized normal distributions to be adequate regional frequency distributions. The extreme daily precipitation at Trento with a 100-year return period was estimated to be between 114 and 148 mm/d. / Egenskaperna hos extremvärden av dygnsnederbörd och -vattenföring i Adigeflodens av-rinningsområde vid staden Trento undersöktes. Serier med årsmaxima för perioden 1975–2014 analyserades med avseende på trender, säsongsindex och L-moment. Trendanalys med Mann-Kendallmetod antydde en svag men signifikant signal om minskande extrem-värden, då andelen mätstationer med signifikant negativa trender överlag var större än signifikansnivån. Den extrema nederbörden karakteriserades huvudsakligen av höststor-mar, medan vattenföringen hade en starkare säsongsbundenhet då maxima inträffade främst under juni och juli. Vattenföringens extremvärden kunde därmed inte enbart för-klaras av nederbördsmaxima. Avrinningsområdet kunde betraktas som en homogen reg-ion för nederbörd, men resultaten gav inte stöd åt ett motsvarande antagande för vatten-föring. En regional frekvensanalys genomfördes för nederbördsdata och visade att Pear-son typ III och den generaliserade normalfördelningen var lämpliga regionala sannolik-hetsfördelningar. Över Trento uppskattades den extrema dygnsnederbörden med en åter-komstperiod på 100 år till mellan 114 och 148 mm/d.