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Descripción
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| Accurate design flood estimates associated with high return periods are necessary to design and manage hydraulic structures such as dams. In practice, the estimate of such quantiles is usually done via univariate flood frequency analyses, mostly based on the study of peak flows. Nevertheless, the nature of floods is multivariate, being essential to consider representative flood characteristics, such as flood peak, hydrograph volume and hydrograph duration, to carry out an appropriate analysis; especially when the inflow peak is transformed into a different outflow peak during the routing process in a reservoir or a floodplain. However, the application of multivariate flood frequency analyses involves complexity. Recently, the use of copulas has been extended in hydrology because of its benefits regarding dealing with the multivariate approach. A copula is a function that represents the dependence structure of the studied variables, and allows obtaining the multivariate frequency distribution of them by using their marginal distributions, regardless of the kind of marginal distributions considered. The estimate of multivariate return periods, and therefore multivariate quantiles, is also facilitated by the way in which copulas are formulated. The present doctoral thesis seeks to provide methodologies for guiding practitioners to perform bivariate flood frequency analyses based on the copula approach, in order to achieve suitable flood quantiles for dam design, dam management and flood risk assessment. The flood variables considered for that goal are peak flow and hydrograph volume. In order to accomplish a complete study by using copulas, the present research addresses: (i) a bivariate local flood frequency analysis focussed on examining and comparing theoretical return periods based on the natural probability of occurrence of a flood, with the return period associated with the risk of dam overtopping, to estimate quantiles at a given gauged site; (ii) the extension of the local to the regional approach to supply a complete procedure for performing a bivariate regional flood frequency analysis, to estimate quantiles for ungauged sites or improving at-site estimates for gauged sites in terms of reduction of uncertainty; (iii) the use of copulas to investigate bivariate flood trends due to increasing urbanisation levels in a catchment; and (iv) the extension of observed flood series by combining the benefits of a copula based model and hydro-meteorological modelling. | |
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Internacional
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Si |
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ISBN
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Tipo de Tesis
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Doctoral |
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Calificación
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Apto cum laude |
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Fecha
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27/04/2015 |