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Annecatherine Favre - One of the best experts on this subject based on the ideXlab platform.
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identification of flood reactivity regions via the functional clustering of Hydrographs
Water Resources Research, 2018Co-Authors: Manuela I. Brunner, Jan Seibert, Daniel Viviroli, Reinhard Furrer, Annecatherine FavreAbstract:Flood Hydrograph shapes contain valuable information on the flood-generation mechanisms of a catchment. To make good use of this information, we express flood Hydrograph shapes as continuous functions using a functional data approach. We propose a clustering approach based on functional data for flood Hydrograph shapes to identify a set of representative Hydrograph shapes on a catchment scale and use these catchment-specific sets of representative Hydrographs to establish regions of catchments with similar flood reactivity on a regional scale. We applied this approach to flood samples of 163 medium-size Swiss catchments. The results indicate that three representative Hydrograph shapes sufficiently describe the Hydrograph shape variability within a catchment and therefore can be used as a proxy for the flood behavior of a catchment. These catchment-specific sets of three Hydrographs were used to group the catchments into three reactivity regions of similar flood behavior. These regions were not only characterized by similar Hydrograph shapes and reactivity but also by event magnitudes and triggering event conditions. We envision these regions to be useful in regionalization studies, regional flood frequency analyses, and to allow for the construction of synthetic design Hydrographs in ungauged catchments. The clustering approach based on functional data which establishes these regions is very flexible and has the potential to be extended to other geographical regions or towards the use in climate impact studies.
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synthetic design Hydrographs for ungauged catchments a comparison of regionalization methods
Stochastic Environmental Research and Risk Assessment, 2018Co-Authors: Manuela I. Brunner, Anna E. Sikorska, Jan Seibert, Daniel Viviroli, Reinhard Furrer, Annecatherine FavreAbstract:Design flood estimates for a given return period are required in both gauged and ungauged catchments for hydraulic design and risk assessments. Contrary to classical design estimates, synthetic design Hydrographs provide not only information on the peak magnitude of events but also on the corresponding Hydrograph volumes together with the Hydrograph shapes. In this study, we tested different regionalization approaches to transfer parameters of synthetic design Hydrographs from gauged to ungauged catchments. These approaches include classical regionalization methods such as linear regression techniques, spatial methods, and methods based on the formation of homogeneous regions. In addition to these classical approaches, we tested nonlinear regression models not commonly used in hydrological regionalization studies, such as random forest, bagging, and boosting. We found that parameters related to the magnitude of the design event can be regionalized well using both linear and nonlinear regression techniques using catchment area, length of the main channel, maximum precipitation intensity, and relief energy as explanatory variables. The Hydrograph shape, however, was found to be more difficult to regionalize due to its high variability within a catchment. Such variability might be better represented by looking at flood-type specific synthetic design Hydrographs.
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representative sets of design Hydrographs for ungauged catchments a regional approach using probabilistic region memberships
Advances in Water Resources, 2018Co-Authors: Manuela I. Brunner, Jan Seibert, Annecatherine FavreAbstract:Abstract Traditional design flood estimation approaches have focused on peak discharges and have often neglected other Hydrograph characteristics such as Hydrograph volume and shape. Synthetic design Hydrograph estimation procedures overcome this deficiency by jointly considering peak discharge, Hydrograph volume, and shape. Such procedures have recently been extended to allow for the consideration of process variability within a catchment by a flood-type specific construction of design Hydrographs. However, they depend on observed runoff time series and are not directly applicable in ungauged catchments where such series are not available. To obtain reliable flood estimates, there is a need for an approach that allows for the consideration of process variability in the construction of synthetic design Hydrographs in ungauged catchments. In this study, we therefore propose an approach that combines a bivariate index flood approach with event-type specific synthetic design Hydrograph construction. First, regions of similar flood reactivity are delineated and a classification rule that enables the assignment of ungauged catchments to one of these reactivity regions is established. Second, event-type specific synthetic design Hydrographs are constructed using the pooled data divided by event type from the corresponding reactivity region in a bivariate index flood procedure. The approach was tested and validated on a dataset of 163 Swiss catchments. The results indicated that 1) random forest is a suitable classification model for the assignment of an ungauged catchment to one of the reactivity regions, 2) the combination of a bivariate index flood approach and event-type specific synthetic design Hydrograph construction enables the consideration of event types in ungauged catchments, and 3) the use of probabilistic class memberships in regional synthetic design Hydrograph construction helps to alleviate the problem of misclassification. Event-type specific synthetic design Hydrograph sets enable the inclusion of process variability into design flood estimation and can be used as a compromise between single best estimate synthetic design Hydrographs and continuous simulation studies.
Manuela I. Brunner - One of the best experts on this subject based on the ideXlab platform.
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identification of flood reactivity regions via the functional clustering of Hydrographs
Water Resources Research, 2018Co-Authors: Manuela I. Brunner, Jan Seibert, Daniel Viviroli, Reinhard Furrer, Annecatherine FavreAbstract:Flood Hydrograph shapes contain valuable information on the flood-generation mechanisms of a catchment. To make good use of this information, we express flood Hydrograph shapes as continuous functions using a functional data approach. We propose a clustering approach based on functional data for flood Hydrograph shapes to identify a set of representative Hydrograph shapes on a catchment scale and use these catchment-specific sets of representative Hydrographs to establish regions of catchments with similar flood reactivity on a regional scale. We applied this approach to flood samples of 163 medium-size Swiss catchments. The results indicate that three representative Hydrograph shapes sufficiently describe the Hydrograph shape variability within a catchment and therefore can be used as a proxy for the flood behavior of a catchment. These catchment-specific sets of three Hydrographs were used to group the catchments into three reactivity regions of similar flood behavior. These regions were not only characterized by similar Hydrograph shapes and reactivity but also by event magnitudes and triggering event conditions. We envision these regions to be useful in regionalization studies, regional flood frequency analyses, and to allow for the construction of synthetic design Hydrographs in ungauged catchments. The clustering approach based on functional data which establishes these regions is very flexible and has the potential to be extended to other geographical regions or towards the use in climate impact studies.
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synthetic design Hydrographs for ungauged catchments a comparison of regionalization methods
Stochastic Environmental Research and Risk Assessment, 2018Co-Authors: Manuela I. Brunner, Anna E. Sikorska, Jan Seibert, Daniel Viviroli, Reinhard Furrer, Annecatherine FavreAbstract:Design flood estimates for a given return period are required in both gauged and ungauged catchments for hydraulic design and risk assessments. Contrary to classical design estimates, synthetic design Hydrographs provide not only information on the peak magnitude of events but also on the corresponding Hydrograph volumes together with the Hydrograph shapes. In this study, we tested different regionalization approaches to transfer parameters of synthetic design Hydrographs from gauged to ungauged catchments. These approaches include classical regionalization methods such as linear regression techniques, spatial methods, and methods based on the formation of homogeneous regions. In addition to these classical approaches, we tested nonlinear regression models not commonly used in hydrological regionalization studies, such as random forest, bagging, and boosting. We found that parameters related to the magnitude of the design event can be regionalized well using both linear and nonlinear regression techniques using catchment area, length of the main channel, maximum precipitation intensity, and relief energy as explanatory variables. The Hydrograph shape, however, was found to be more difficult to regionalize due to its high variability within a catchment. Such variability might be better represented by looking at flood-type specific synthetic design Hydrographs.
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representative sets of design Hydrographs for ungauged catchments a regional approach using probabilistic region memberships
Advances in Water Resources, 2018Co-Authors: Manuela I. Brunner, Jan Seibert, Annecatherine FavreAbstract:Abstract Traditional design flood estimation approaches have focused on peak discharges and have often neglected other Hydrograph characteristics such as Hydrograph volume and shape. Synthetic design Hydrograph estimation procedures overcome this deficiency by jointly considering peak discharge, Hydrograph volume, and shape. Such procedures have recently been extended to allow for the consideration of process variability within a catchment by a flood-type specific construction of design Hydrographs. However, they depend on observed runoff time series and are not directly applicable in ungauged catchments where such series are not available. To obtain reliable flood estimates, there is a need for an approach that allows for the consideration of process variability in the construction of synthetic design Hydrographs in ungauged catchments. In this study, we therefore propose an approach that combines a bivariate index flood approach with event-type specific synthetic design Hydrograph construction. First, regions of similar flood reactivity are delineated and a classification rule that enables the assignment of ungauged catchments to one of these reactivity regions is established. Second, event-type specific synthetic design Hydrographs are constructed using the pooled data divided by event type from the corresponding reactivity region in a bivariate index flood procedure. The approach was tested and validated on a dataset of 163 Swiss catchments. The results indicated that 1) random forest is a suitable classification model for the assignment of an ungauged catchment to one of the reactivity regions, 2) the combination of a bivariate index flood approach and event-type specific synthetic design Hydrograph construction enables the consideration of event types in ungauged catchments, and 3) the use of probabilistic class memberships in regional synthetic design Hydrograph construction helps to alleviate the problem of misclassification. Event-type specific synthetic design Hydrograph sets enable the inclusion of process variability into design flood estimation and can be used as a compromise between single best estimate synthetic design Hydrographs and continuous simulation studies.
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Bivariate analysis of floods in climate impact assessments
Science of The Total Environment, 2017Co-Authors: Manuela I. Brunner, Anna E. Sikorska, Jan SeibertAbstract:Climate impact studies regarding floods usually focus on peak discharges and a bivariate assessment of peak discharges and Hydrograph volumes is not commonly included. A joint consideration of peak discharges and Hydrograph volumes, however, is crucial when assessing flood risks for current and future climate conditions. Here, we present a methodology to develop synthetic design Hydrographs for future climate conditions that jointly consider peak discharges and Hydrograph volumes. First, change factors are derived based on a regional climate model and are applied to observed precipitation and temperature time series. Second, the modified time series are fed into a calibrated hydrological model to simulate runoff time series for future conditions. Third, these time series are used to construct synthetic design Hydrographs. The bivariate flood frequency analysis used in the construction of synthetic design Hydrographs takes into account the dependence between peak discharges and Hydrograph volumes, and represents the shape of the Hydrograph. The latter is modeled using a probability density function while the dependence between the design variables peak discharge and Hydrograph volume is modeled using a copula. We applied this approach to a set of eight mountainous catchments in Switzerland to construct catchment-specific and season-specific design Hydrographs for a control and three scenario climates. Our work demonstrates that projected climate changes have an impact not only on peak discharges but also on Hydrograph volumes and on Hydrograph shapes both at an annual and at a seasonal scale. These changes are not necessarily proportional which implies that climate impact assessments on future floods should consider more flood characteristics than just flood peaks.
Jan Seibert - One of the best experts on this subject based on the ideXlab platform.
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identification of flood reactivity regions via the functional clustering of Hydrographs
Water Resources Research, 2018Co-Authors: Manuela I. Brunner, Jan Seibert, Daniel Viviroli, Reinhard Furrer, Annecatherine FavreAbstract:Flood Hydrograph shapes contain valuable information on the flood-generation mechanisms of a catchment. To make good use of this information, we express flood Hydrograph shapes as continuous functions using a functional data approach. We propose a clustering approach based on functional data for flood Hydrograph shapes to identify a set of representative Hydrograph shapes on a catchment scale and use these catchment-specific sets of representative Hydrographs to establish regions of catchments with similar flood reactivity on a regional scale. We applied this approach to flood samples of 163 medium-size Swiss catchments. The results indicate that three representative Hydrograph shapes sufficiently describe the Hydrograph shape variability within a catchment and therefore can be used as a proxy for the flood behavior of a catchment. These catchment-specific sets of three Hydrographs were used to group the catchments into three reactivity regions of similar flood behavior. These regions were not only characterized by similar Hydrograph shapes and reactivity but also by event magnitudes and triggering event conditions. We envision these regions to be useful in regionalization studies, regional flood frequency analyses, and to allow for the construction of synthetic design Hydrographs in ungauged catchments. The clustering approach based on functional data which establishes these regions is very flexible and has the potential to be extended to other geographical regions or towards the use in climate impact studies.
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synthetic design Hydrographs for ungauged catchments a comparison of regionalization methods
Stochastic Environmental Research and Risk Assessment, 2018Co-Authors: Manuela I. Brunner, Anna E. Sikorska, Jan Seibert, Daniel Viviroli, Reinhard Furrer, Annecatherine FavreAbstract:Design flood estimates for a given return period are required in both gauged and ungauged catchments for hydraulic design and risk assessments. Contrary to classical design estimates, synthetic design Hydrographs provide not only information on the peak magnitude of events but also on the corresponding Hydrograph volumes together with the Hydrograph shapes. In this study, we tested different regionalization approaches to transfer parameters of synthetic design Hydrographs from gauged to ungauged catchments. These approaches include classical regionalization methods such as linear regression techniques, spatial methods, and methods based on the formation of homogeneous regions. In addition to these classical approaches, we tested nonlinear regression models not commonly used in hydrological regionalization studies, such as random forest, bagging, and boosting. We found that parameters related to the magnitude of the design event can be regionalized well using both linear and nonlinear regression techniques using catchment area, length of the main channel, maximum precipitation intensity, and relief energy as explanatory variables. The Hydrograph shape, however, was found to be more difficult to regionalize due to its high variability within a catchment. Such variability might be better represented by looking at flood-type specific synthetic design Hydrographs.
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representative sets of design Hydrographs for ungauged catchments a regional approach using probabilistic region memberships
Advances in Water Resources, 2018Co-Authors: Manuela I. Brunner, Jan Seibert, Annecatherine FavreAbstract:Abstract Traditional design flood estimation approaches have focused on peak discharges and have often neglected other Hydrograph characteristics such as Hydrograph volume and shape. Synthetic design Hydrograph estimation procedures overcome this deficiency by jointly considering peak discharge, Hydrograph volume, and shape. Such procedures have recently been extended to allow for the consideration of process variability within a catchment by a flood-type specific construction of design Hydrographs. However, they depend on observed runoff time series and are not directly applicable in ungauged catchments where such series are not available. To obtain reliable flood estimates, there is a need for an approach that allows for the consideration of process variability in the construction of synthetic design Hydrographs in ungauged catchments. In this study, we therefore propose an approach that combines a bivariate index flood approach with event-type specific synthetic design Hydrograph construction. First, regions of similar flood reactivity are delineated and a classification rule that enables the assignment of ungauged catchments to one of these reactivity regions is established. Second, event-type specific synthetic design Hydrographs are constructed using the pooled data divided by event type from the corresponding reactivity region in a bivariate index flood procedure. The approach was tested and validated on a dataset of 163 Swiss catchments. The results indicated that 1) random forest is a suitable classification model for the assignment of an ungauged catchment to one of the reactivity regions, 2) the combination of a bivariate index flood approach and event-type specific synthetic design Hydrograph construction enables the consideration of event types in ungauged catchments, and 3) the use of probabilistic class memberships in regional synthetic design Hydrograph construction helps to alleviate the problem of misclassification. Event-type specific synthetic design Hydrograph sets enable the inclusion of process variability into design flood estimation and can be used as a compromise between single best estimate synthetic design Hydrographs and continuous simulation studies.
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Bivariate analysis of floods in climate impact assessments
Science of The Total Environment, 2017Co-Authors: Manuela I. Brunner, Anna E. Sikorska, Jan SeibertAbstract:Climate impact studies regarding floods usually focus on peak discharges and a bivariate assessment of peak discharges and Hydrograph volumes is not commonly included. A joint consideration of peak discharges and Hydrograph volumes, however, is crucial when assessing flood risks for current and future climate conditions. Here, we present a methodology to develop synthetic design Hydrographs for future climate conditions that jointly consider peak discharges and Hydrograph volumes. First, change factors are derived based on a regional climate model and are applied to observed precipitation and temperature time series. Second, the modified time series are fed into a calibrated hydrological model to simulate runoff time series for future conditions. Third, these time series are used to construct synthetic design Hydrographs. The bivariate flood frequency analysis used in the construction of synthetic design Hydrographs takes into account the dependence between peak discharges and Hydrograph volumes, and represents the shape of the Hydrograph. The latter is modeled using a probability density function while the dependence between the design variables peak discharge and Hydrograph volume is modeled using a copula. We applied this approach to a set of eight mountainous catchments in Switzerland to construct catchment-specific and season-specific design Hydrographs for a control and three scenario climates. Our work demonstrates that projected climate changes have an impact not only on peak discharges but also on Hydrograph volumes and on Hydrograph shapes both at an annual and at a seasonal scale. These changes are not necessarily proportional which implies that climate impact assessments on future floods should consider more flood characteristics than just flood peaks.
Sanjay Kumar - One of the best experts on this subject based on the ideXlab platform.
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Flood Hydrograph with Synthetic Unit Hydrograph Routing
Water Resources Management, 2015Co-Authors: M. K. Bhuyan, Joygopal Jena, Sanjay Kumar, Prajesh Kiran BhunyaAbstract:Synthetic unit Hydrographs (SUH) based on geomorphology are used as a tool to produce flood Hydrographs from rainfall records, especially in ungauged and partially gauged catchments. This study presents a flood Hydrograph model formulated on SUH based approach using geomorphologic parameters derived from Survey of India maps and geographical information system (GIS) techniques to simulate basin runoff. It uses linear Muskingum routing model in which the routing parameters are determined from the kinematic approach rather than from runoff data. The model employs the unit Hydrograph suggested by Central Water Commission (CWC) India, as the discharge data from the sub-catchments and routes the concurrent discharges generated from them to the watershed outlet, and compared with the unit Hydrograph of the lumped catchment. Application of the model is demonstrated by using data of a small watershed in the Mahanadi basin, India. The study indicates the limitations of the CWC unit Hydrograph approach both in the small hilly and large plane catchments. It is observed that the CWC unit Hydrograph (UH) underestimates the peak discharges both for catchments smaller than 200 km 2 with steeper slope and larger than 600 km 2 with flatter slope. The study further emphasizes on using two parameter Gamma distribution for preparation of UH curve instead of adopting standard practice of drawing synthetic unit Hydrograph using seven known points with approximate curve fitting. Copyright Springer Science+Business Media Dordrecht 2015
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runoff estimation for an ungauged catchment using geomorphological instantaneous unit Hydrograph giuh models
Hydrological Processes, 2007Co-Authors: Rakesh Kumar, Chandranath Chatterjee, R Singh, A K Lohani, Sanjay KumarAbstract:A geomorphological instantaneous unit Hydrograph (GIUH) is derived from the geomorphological characteristics of a catchment and it is related to the parameters of the Clark instantaneous unit Hydrograph (IUH) model as well as the Nash IUH model for deriving its complete shape. The developed GIUH based Clark and Nash models are applied for simulation of the direct surface run-off (DSRO) Hydrographs for ten rainfall-runoff events of the Ajay catchment up to the Sarath gauging site of eastern India. The geomorphological characteristics of the Ajay catchment are evaluated using the GIS package, Integrated Land and Water Information System (ILWIS). The performances of the GIUH based Clark and Nash models in simulating the DSRO Hydrographs are compared with the Clark IUH model option of HEC-1 package and the Nash IUH model, using some commonly used objective functions. The DSRO Hydrographs are computed with reasonable accuracy by the GIUH based Clark and Nash models, which simulate the DSRO Hydrographs of the catchment considering it to be ungauged. Inter comparison of the performances of the GIUH based Clark and Nash models shows that the DSRO Hydrographs are estimated with comparable accuracy by both the models. Copyright © 2007 John Wiley & Sons, Ltd.
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runoff estimation for an ungauged catchment using geomorphological instantaneous unit Hydrograph giuh models
Hydrological Processes, 2007Co-Authors: Rakesh Kumar, Chandranath Chatterjee, R Singh, A K Lohani, Sanjay KumarAbstract:A geomorphological instantaneous unit Hydrograph (GIUH) is derived from the geomorphological characteristics of a catchment and it is related to the parameters of the Clark instantaneous unit Hydrograph (IUH) model as well as the Nash IUH model for deriving its complete shape. The developed GIUH based Clark and Nash models are applied for simulation of the direct surface run-off (DSRO) Hydrographs for ten rainfall-runoff events of the Ajay catchment up to the Sarath gauging site of eastern India. The geomorphological characteristics of the Ajay catchment are evaluated using the GIS package, Integrated Land and Water Information System (ILWIS). The performances of the GIUH based Clark and Nash models in simulating the DSRO Hydrographs are compared with the Clark IUH model option of HEC-1 package and the Nash IUH model, using some commonly used objective functions. The DSRO Hydrographs are computed with reasonable accuracy by the GIUH based Clark and Nash models, which simulate the DSRO Hydrographs of the catchment considering it to be ungauged. Inter comparison of the performances of the GIUH based Clark and Nash models shows that the DSRO Hydrographs are estimated with comparable accuracy by both the models. Copyright © 2007 John Wiley & Sons, Ltd.
Kaihung Cheng - One of the best experts on this subject based on the ideXlab platform.
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experimental investigation of bedload transport processes under unsteady flow conditions
Hydrological Processes, 2004Co-Authors: Kaihung ChengAbstract:Hydraulic engineering is usually based on theoretical analysis and/or numerical modelling simulation. As the dynamic behaviour of sediment movement under unsteady flow is still unclear, and field measurement is comparatively difficult during a large flood, prior investigations through flume experiments are required. A series of flume experiments, conducted using different inflow Hydrographs without sediment supply from upstream, was carried out to investigate the sediment transport process under unsteady flow conditions. A series of triangular Hydrographs were performed in the experiments. The results indicate that a temporal lag was found between the flow Hydrograph peak and the sediment Hydrograph peak because large size sand dunes lasted for a short period in the falling limb of the flow Hydrograph. The temporal lag was found to be about equal to 6–15% of the flow Hydrograph duration. Owing to the temporal lag, the total bedload yield in the rising period was less than that in the falling period. Furthermore, the measured total bedload yield in the unsteady flow experiments was larger than the predicted value, which was estimated by using the results obtained from the equivalent steady flow experiment. The peak bedload transport rate for unsteady flow conditions was also larger than the predicted value. The ratios of the measured to the predicted quantities mentioned above were found to be constant values for different shapes of Hydrographs. It is, therefore, expected that the analytical results of sediment transport from equivalent steady flow can be a good reference for sediment transport under unsteady flow conditions. Copyright 2004 John Wiley & Sons, Ltd.
