Dependence between flood peaks and volumes: a case study on climate and hydrological controls

Gaál, Ladislav; Szolgay, Ján; Kohnová, Silvia; Hlavčová, Kamila; Parajka, J.; Viglione, Alberto; Merz, Ralf; Blöschl, Günter

doi:10.1080/02626667.2014.951361

Cited by 79 publications

(67 citation statements)

References 63 publications

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“…Therefore, the relationship between flood peaks and volumes is an interesting scientific research issue both from the statistical and hydrological points of view. In particular, the examination of the interplay of climatic and catchment processes in defining the probabilities of peaks and volumes is a challenging problem (Gaál et al, 2015). In engineering hydrology practice, the statistical analysis of flood peaks and volumes are often dealt with in a multivariate frequency framework.…”

Section: Introductionmentioning

confidence: 99%

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A process-based analysis of the suitability of copula types for peak-volume flood relationships

et al. 2015

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Abstract. The work aims at analyzing the bivariate relationship between flood peaks and flood volumes, with a particular focus on the type and seasonality of flood generation processes. Instead of the usual approach that deals with an analysis of the annual maxima of flood events, the current analysis includes all independent flood events in a catchment. Flood events are considered independent when they originate from distinguishably different synoptic/meteorological situations. The target region is located in the northern part of Austria, and consists of 72 small and mid-sized catchments. On the basis of the discharge measurements with a time resolution of 1 h from the period 1976-2007, independent flood events were identified and were assigned to one of the three following flood generation type categories: synoptic floods, flash floods and snowmelt floods. These were subsequently divided into two seasons, thereby separating predominantly rainfall-fed and snowmelt-fed floods. Nine frequently-used copula types were locally fitted to the samples of the flood type and seasonal data. Their goodness-of-fit was examined locally as well as analyzed in a regional scope. It was concluded that (i) treating flood processes separately is beneficial for the statistical analysis; (ii) suitability patterns of acceptable copula types are distinguishably different for the seasons/flood types considered, (iii) the Clayton and Joe copulas shows an unacceptable performance for all the seasons/flood types in the region; (iv) the rejection rate of the other copula types depends on the season/flood type and also on the sample size; (v) given that usually more than one statistically suitable dependence model exists, an uncertainty analysis of the design values in the engineering studies resulting from the choice of model seems unavoidable; (vi) reducing uncertainty in the choice of model could be attempted by a deeper hydrological analysis of the dependence structure between flood peaks and volumes in order to give hydrological support to the decision on model's suitability in specific regions and for typical flood generation mechanisms.

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Section: Introductionmentioning

confidence: 99%

“…In Gaál et al (2015), our aim was to understand the causal factors controlling the relationship between flood peaks and volumes for the same data. The consistency of the peakvolume relationship was quantified by Spearman's rank correlation coefficient, which ranged from about 0.2 in the high alpine catchments to about 0.8 in the lowlands.…”

Section: Introductionmentioning

confidence: 99%

A process-based analysis of the suitability of copula types for peak-volume flood relationships

et al. 2015

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“…This is also suggested by a pure visual comparison of the scatterplots that indicate that the synoptic and snowmelt floods are more similar to each other than the remaining process pairs; or, in other words, flash floods tend to be more dissimilar from both the synoptic and snowmelt floods (in terms of their empirical copulas). This could be intuitively partly related to a much stronger upper tail dependence of flash floods and their specific (similar) hydrograph shapes (Gaál et al, 2014). However, the overall rejection rates are rather small and the analysis has not brought really conclusive results for the subsequent selection of theoretical copula models for engineering design, which would logically follow such an analysis in practice.…”

Section: Comparison Of the Similarity Of Empirical Copulas For Differmentioning

confidence: 99%

“…before and during the individual flood events. Gaál et al (2014) reduced the number of the flood process types from five to three by merging similar categories. Their three classes consist of synoptic floods (originally long-rain and short-rain floods), flash floods (no change in the classification) and snowmelt floods (originally rain-onsnow floods and snowmelt floods).…”

Section: Classification Of Flood Generation Processesmentioning

confidence: 99%

“…The results described the roles of climate (through the type of precipitation generated), together with the attributes of the environment and flow generation processes (through antecedent soil moisture and soil characteristics) on the magnitude of flood time scales. Gaál et al (2014) attempted to understand the causal hydrological factors controlling the strength of the relationship between flood peaks and volumes for the same data quantified by Spearman's rank correlation coefficient. The results suggested that the factors controlling the strength of the dependence are more related to climate instead of catchment characteristics.…”

Section: Introductionmentioning

confidence: 99%

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A regional comparative analysis of empirical and theoretical flood peak-volume relationships

Szolgay

Gaál

Bacigál

et al. 2016

Journal of Hydrology and Hydromechanics

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This paper analyses the bivariate relationship between flood peaks and corresponding flood event volumes modelled by empirical and theoretical copulas in a regional context, with a focus on flood generation processes in general, the regional differentiation of these and the effect of the sample size on reliable discrimination among models. A total of 72 catchments in North-West of Austria are analysed for the period . From the hourly runoff data set, 25 697 flood events were isolated and assigned to one of three flood process types: synoptic floods (including long-and short-rain floods), flash floods or snowmelt floods (both rain-on-snow and snowmelt floods). The first step of the analysis examines whether the empirical peak-volume copulas of different flood process types are regionally statistically distinguishable, separately for each catchment and the role of the sample size on the strength of the statements. The results indicate that the empirical copulas of flash floods tend to be different from those of the synoptic and snowmelt floods. The second step examines how similar are the empirical flood peak-volume copulas between catchments for a given flood type across the region. Empirical copulas of synoptic floods are the least similar between the catchments, however with the decrease of the sample size the difference between the performances of the process types becomes small. The third step examines the goodness-of-fit of different commonly used copula types to the data samples that represent the annual maxima of flood peaks and the respective volumes both regardless of flood generating processes (the traditional engineering approach) and also considering the three process-based classes. Extreme value copulas (Galambos, Gumbel and Hüsler-Reiss) show the best performance both for synoptic and flash floods, while the Frank copula shows the best performance for snowmelt floods. It is concluded that there is merit in treating flood types separately when analysing and estimating flood peak-volume dependence copulas; however, even the enlarged dataset gained by the process-based analysis in this study does not give sufficient information for a reliable model choice for multivariate statistical analysis of flood peaks and volumes.

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Flood‐type classification in mountainous catchments using crisp and fuzzy decision trees

Sikorska

Viviroli

Seibert

2015

Water Resources Research

106

138

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Floods are governed by largely varying processes and thus exhibit various behaviors. Classification of flood events into flood types and the determination of their respective frequency is therefore important for a better understanding and prediction of floods. This study presents a flood classification for identifying flood patterns at a catchment scale by means of a fuzzy decision tree. Hence, events are represented as a spectrum of six main possible flood types that are attributed with their degree of acceptance. Considered types are flash, short rainfall, long rainfall, snow-melt, rainfall on snow and, in high alpine catchments, glacier-melt floods. The fuzzy decision tree also makes it possible to acknowledge the uncertainty present in the identification of flood processes and thus allows for more reliable flood class estimates than using a crisp decision tree, which identifies one flood type per event. Based on the data set in nine Swiss mountainous catchments, it was demonstrated that this approach is less sensitive to uncertainties in the classification attributes than the classical crisp approach. These results show that the fuzzy approach bears additional potential for analyses of flood patterns at a catchment scale and thereby it provides more realistic representation of flood processes. AbstractFloods are governed by largely varying processes and thus exhibit various behaviors. Classification of flood events into flood types and the determination of their respective frequency is therefore important for a better understanding and prediction of floods. This study presents a flood classification for identifying flood patterns at a catchment scale by means of a fuzzy decision tree. Hence, events are represented as a spectrum of six main possible flood types that are attributed with their degree of acceptance. Considered types are flash, short rainfall, long rainfall, snow-melt, rainfall on snow and, in high alpine catchments, glacier-melt floods. The fuzzy decision tree also makes it possible to acknowledge the uncertainty present in the identification of flood processes and thus allows for more reliable flood class estimates than using a crisp decision tree, which identifies one flood type per Provide feedback or get help event. Based on the data set in nine Swiss mountainous catchments, it was demonstrated that this approach is less sensitive to uncertainties in the classification attributes than the classical crisp approach. These results show that the fuzzy approach bears additional potential for analyses of flood patterns at a catchment scale and thereby it provides more realistic representation of flood processes.

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Dependence between flood peaks and volumes: a case study on climate and hydrological controls

Cited by 79 publications

References 63 publications

A process-based analysis of the suitability of copula types for peak-volume flood relationships

A process-based analysis of the suitability of copula types for peak-volume flood relationships

A regional comparative analysis of empirical and theoretical flood peak-volume relationships

Flood‐type classification in mountainous catchments using crisp and fuzzy decision trees

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