TY - JOUR
A1 - Di Baldassarre, Giuliano
A1 - Kreibich, Heidi
A1 - Vorogushyn, Sergiy
A1 - Aerts, Jeroen
A1 - Arnbjerg-Nielsen, Karsten
A1 - Barendrecht, Marlies
A1 - Bates, Paul
A1 - Borga, Marco
A1 - Botzen, Wouter
A1 - Bubeck, Philip
A1 - De Marchi, Bruna
A1 - Llasat, Carmen Maria
A1 - Mazzoleni, Maurizio
A1 - Molinari, Daniela
A1 - Mondino, Elena
A1 - Mard, Johanna
A1 - Petrucci, Olga
A1 - Scolobig, Anna
A1 - Viglione, Alberto
A1 - Ward, Philip J.
T1 - Hess Opinions: An interdisciplinary research agenda to explore the unintended consequences of structural flood protection
JF - Hydrology and earth system sciences : HESS
N2 - One common approach to cope with floods is the implementation of structural flood protection measures, such as levees or flood-control reservoirs, which substantially reduce the probability of flooding at the time of implementation. Numerous scholars have problematized this approach. They have shown that increasing the levels of flood protection can attract more settlements and high-value assets in the areas protected by the new measures. Other studies have explored how structural measures can generate a sense of complacency, which can act to reduce preparedness. These paradoxical risk changes have been described as "levee effect", "safe development paradox" or "safety dilemma". In this commentary, we briefly review this phenomenon by critically analysing the intended benefits and unintended effects of structural flood protection, and then we propose an interdisciplinary research agenda to uncover these paradoxical dynamics of risk.
Y1 - 2018
U6 - https://doi.org/10.5194/hess-22-5629-2018
SN - 1027-5606
SN - 1607-7938
VL - 22
IS - 11
SP - 5629
EP - 5637
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Vorogushyn, Sergiy
A1 - Apel, Heiko
A1 - Kemter, Matthias
A1 - Thieken, Annegret
T1 - Analyse der Hochwassergefährdung im Ahrtal unter Berücksichtigung historischer Hochwasser
T1 - Analysis of flood hazard in the Ahr Valley considering historical floods
JF - Hydrologie und Wasserbewirtschaftung
N2 - The flood disaster in July 2021 in western Germany calls for a critical discussion on flood hazard assessment, revision of flood hazard maps and communication of extreme flood scenarios. In the presented work, extreme value analysis was carried out for annual maximum peak flow series at the Altenahr gauge on the river Ahr. We compared flood statistics with and without considering historical flood events. An estimate for the return period of the recent flood based on the Generalized Extreme Value (GEV) distribution considering historical floods ranges between about 2600 and above 58700 years (90% confidence interval) with a median of approximately 8600 years, whereas an estimate based on the 74-year long systematically recorded flow series would theoretically exceed 100 million years. Consideration of historical floods dramatically changes the flood quantiles that are used for the generation of official flood hazard maps. The fitting of the GEV to the time series with historical floods reveals, however, that the model potentially inadequately reflects the flood population. In this case, we might face a mixed sample, in which extreme floods result from very different processes compared to smaller floods. Hence, the probabilities of extreme floods could be much larger than those resulting from a single GEV model. The application of a process-based mixed flood distribution should be explored in future work.
The comparison of the official HQextrem flood maps for the AhrValley with the inundation areas from July 2021 shows a striking discrepancy in the affected areas and calls for revision of design values used to define extreme flood scenarios. The hydrodynamic simulations of a 1000-year return period flood considering historical events and of the 1804 flood scenario compare much better to the flooded areas from July 2021, though both scenarios still underestimated the flood extent.
Particular effects such as clogging of bridges and geomorphological changes of the river channel led to considerably larger flooded areas in July 2021 compared to the simulation results. Based on this analysis, we call for a consistent definition of HQextrem for flood hazard mapping in Germany, and suggest using high flood quantiles in the range of a 1,000-year flood. Flood maps should additionally include model-based reconstructions of the largest, reliably documented historical floods and/or synthetic worst-case scenarios. This would be an important step towards protecting potentially affected population and disaster management from surprises due to very rare and extreme flood events in future.
N2 - Die Hochwasserkatastrophe im Juli 2021 in Westdeutschland erfordert eine kritische Diskussion über die Abschätzung der Hochwassergefährdung, Aktualisierung von Hochwassergefahrenkarten und Kommunikation von extremen Hochwasserszenarien. In der vorliegenden Arbeit wurde die Extremwertstatistik für die jährlichen maximalen Spitzenabflüsse am Pegel Altenahr im Ahrtal mit und ohne Berücksichtigung historischer Hochwasser berechnet und verglichen. Die Schätzung der Wiederkehrperiode für das aktuelle Hochwasser mittels Generalisierter Extremwertverteilung (GEV) unter Berücksichtigung historischer Hochwasser schwankt zwischen etwa 2.600 und über 58.700 Jahren (90%-Konfidenzintervall) mit einem Median bei etwa 8.600 Jahren, wogegen die Schätzung, die nur auf der systematisch gemessenen Abflusszeitreihe von 74 Jahren basiert, theoretisch eine Wiederkehrperiode von über 100 Millionen Jahren ergeben würde. Die Berücksichtigung der historischen Hochwasser führt zu einer dramatischen Änderung der Hochwasserquan-
tile, die für eine Gefahrenkartierung zugrunde gelegt werden. Die Anpassung der GEV an die Zeitreihe mit historischen Hochwassern zeigt dennoch, dass das GEV-Modell möglicherweise die Grundgesamtheit der Hochwasser im Ahrtal nicht adäquat abbilden kann. Es könnte sich im vorliegenden Fall um eine gemischte Stichprobe handeln, in der die extremen Hochwasser im Vergleich zu kleineren Ereignissen durch besondere Prozesse hervorgerufen werden. Somit könnten die Wahrscheinlichkeiten von extremen Hochwassern deutlich größer sein, als aus dem GEV-Modell hervorgeht. Hier sollte in Zukunft die Anwendung einer prozessbasierten Mischverteilung
untersucht werden. Der Vergleich von amtlichen Gefahrenkarten zu Extremhochwassern (HQextrem) im Ahrtal mit den Überflutungsflächen vom Juli 2021
zeigt eine deutliche Diskrepanz in den betroffenen Gebieten und die Notwendigkeit, die Grundlagen zur Erstellung der Extremszenarien zu überdenken. Die hydrodynamisch-numerischen Simulationen von 1.000-jährlichen Hochwassern (HQ1000) unter Berücksichtigung historischer Ereignisse und des größten historischen Hochwassers 1804 können die Gefährdung des Juli-Hochwassers 2021 deutlich besser widerspiegeln, wenngleich auch diese beiden Szenarien die Überflutungsflächen unterschätzen. Besondere Effekte wie die Verklausung von Brücken und die geomorphologischen Änderungen im Flussschlauch führten zu noch größeren Überflutungs- flächen im Juli 2021, als die Simulationsergebnisse zeigten. Basierend auf dieser Analyse wird eine einheitliche Festlegung von HQextrem bei Hochwassergefahrenkartierungen in Deutschland vorgeschlagen, die sich an höheren Hochwasserquantilen im Bereich von HQ1000 orientiert. Zusätzlich sollen simulationsbasierte Rekonstruktionen von den größten verlässlich dokumentierten historischen Hochwassern und/oder synthetische Worst-Case-Szenarien in den Hochwassergefahrenkarten gesondert dargestellt werden. Damit wird ein wichtiger Beitrag geleistet, um die potenziell betroffene Bevölkerung und das Katastrophenmanagement vor Überraschungen durch sehr seltene und extreme Hochwasser in Zukunft besser zu schützen.
KW - Extreme value statistics
KW - historical floods
KW - flood hazard mapping;
KW - inundation simulation
KW - Ahr River
KW - Extremwertstatistik
KW - historische Hochwasser
KW - Gefahrenkarten
KW - Überflutungssimulation
KW - Ahr
Y1 - 2022
U6 - https://doi.org/10.5675/HyWa_2022.5_2
SN - 1439-1783
VL - 66
IS - 5
SP - 244
EP - 254
PB - Bundesanst. für Gewässerkunde
CY - Koblenz
ER -
TY - JOUR
A1 - Merz, Bruno
A1 - Viet Dung Nguyen,
A1 - Vorogushyn, Sergiy
T1 - Temporal clustering of floods in Germany: Do flood-rich and flood-poor periods exist?
JF - Journal of hydrology
N2 - The repeated occurrence of exceptional floods within a few years, such as the Rhine floods in 1993 and 1995 and the Elbe and Danube floods in 2002 and 2013, suggests that floods in Central Europe may be organized in flood-rich and flood-poor periods. This hypothesis is studied by testing the significance of temporal clustering in flood occurrence (peak-over-threshold) time series for 68 catchments across Germany for the period 1932-2005. To assess the robustness of the results, different methods are used: Firstly, the index of dispersion, which quantifies the departure from a homogeneous Poisson process, is investigated. Further, the time-variation of the flood occurrence rate is derived by non-parametric kernel implementation and the significance of clustering is evaluated via parametric and non-parametric tests. Although the methods give consistent overall results, the specific results differ considerably. Hence, we recommend applying different methods when investigating flood clustering. For flood estimation and risk management, it is of relevance to understand whether clustering changes with flood severity and time scale. To this end, clustering is assessed for different thresholds and time scales. It is found that the majority of catchments show temporal clustering at the 5% significance level for low thresholds and time scales of one to a few years. However, clustering decreases substantially with increasing threshold and time scale. We hypothesize that flood clustering in Germany is mainly caused by catchment memory effects along with intra- to inter-annual climate variability, and that decadal climate variability plays a minor role. (C) 2016 Elsevier B.V. All rights reserved.
KW - Climate variability
KW - Flooding
KW - Temporal clustering
KW - Index of dispersion
KW - Kernel occurrence rate
Y1 - 2016
U6 - https://doi.org/10.1016/j.jhydrol.2016.07.041
SN - 0022-1694
SN - 1879-2707
VL - 541
SP - 824
EP - 838
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - Murawski, Aline
A1 - Bürger, Gerd
A1 - Vorogushyn, Sergiy
A1 - Merz, Bruno
T1 - Can local climate variability be explained by weather patterns? A multi-station evaluation for the Rhine basin
JF - Hydrology and earth system sciences : HESS
N2 - To understand past flood changes in the Rhine catchment and in particular the role of anthropogenic climate change in extreme flows, an attribution study relying on a proper GCM (general circulation model) downscaling is needed. A downscaling based on conditioning a stochastic weather generator on weather patterns is a promising approach. This approach assumes a strong link between weather patterns and local climate, and sufficient GCM skill in reproducing weather pattern climatology. These presuppositions are unprecedentedly evaluated here using 111 years of daily climate data from 490 stations in the Rhine basin and comprehensively testing the number of classification parameters and GCM weather pattern characteristics. A classification based on a combination of mean sea level pressure, temperature, and humidity from the ERA20C reanalysis of atmospheric fields over central Europe with 40 weather types was found to be the most appropriate for stratifying six local climate variables. The corresponding skill is quite diverse though, ranging from good for radiation to poor for precipitation. Especially for the latter it was apparent that pressure fields alone cannot sufficiently stratify local variability. To test the skill of the latest generation of GCMs from the CMIP5 ensemble in reproducing the frequency, seasonality, and persistence of the derived weather patterns, output from 15 GCMs is evaluated. Most GCMs are able to capture these characteristics well, but some models showed consistent deviations in all three evaluation criteria and should be excluded from further attribution analysis.
Y1 - 2016
U6 - https://doi.org/10.5194/hess-20-4283-2016
SN - 1027-5606
SN - 1607-7938
VL - 20
SP - 4283
EP - 4306
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Merz, Bruno
A1 - Nguyen, Viet Dung
A1 - Apel, Heiko
A1 - Gerlitz, Lars
A1 - Schröter, Kai
A1 - Steirou, Eva Styliani
A1 - Vorogushyn, Sergiy
T1 - Spatial coherence of flood-rich and flood-poor periods across Germany
JF - Journal of hydrology
N2 - Despite its societal relevance, the question whether fluctuations in flood occurrence or magnitude are coherent in space has hardly been addressed in quantitative terms. We investigate this question for Germany by analysing fluctuations in annual maximum series (AMS) values at 68 discharge gauges for the common time period 1932-2005. We find remarkable spatial coherence across Germany given its different flood regimes. For example, there is a tendency that flood-rich/-poor years in sub-catchments of the Rhine basin, which are dominated by winter floods, coincide with flood-rich/-poor years in the southern sub-catchments of the Danube basin, which have their dominant flood season in summer. Our findings indicate that coherence is caused rather by persistence in catchment wetness than by persistent periods of higher/lower event precipitation. Further, we propose to differentiate between event-type and non-event-type coherence. There are quite a number of hydrological years with considerable nonevent-type coherence, i.e. AMS values of the 68 gauges are spread out through the year but in the same magnitude range. Years with extreme flooding tend to be of event-type and non-coherent, i.e. there is at least one precipitation event that affects many catchments to various degree. Although spatial coherence is a remarkable phenomenon, and large-scale flooding across Germany can lead to severe situations, extreme magnitudes across the whole country within one event or within one year were not observed in the investigated period. (C) 2018 Elsevier B.V. All rights reserved.
KW - Flood timing
KW - Spatial coherence
KW - Flood regimes
KW - Climate variability
KW - Catchment wetness
Y1 - 2018
U6 - https://doi.org/10.1016/j.jhydrol.2018.02.082
SN - 0022-1694
SN - 1879-2707
VL - 559
SP - 813
EP - 826
PB - Elsevier
CY - Amsterdam
ER -
TY - JOUR
A1 - He, Zhihua
A1 - Vorogushyn, Sergiy
A1 - Unger-Shayesteh, Katy
A1 - Gafurov, Abror
A1 - Kalashnikova, Olga
A1 - Omorova, Elvira
A1 - Merz, Bruno
T1 - The Value of Hydrograph Partitioning Curves for Calibrating Hydrological Models in Glacierized Basins
JF - Water resources research
N2 - This study refines the method for calibrating a glacio-hydrological model based on Hydrograph Partitioning Curves (HPCs), and evaluates its value in comparison to multidata set optimization approaches which use glacier mass balance, satellite snow cover images, and discharge. The HPCs are extracted from the observed flow hydrograph using catchment precipitation and temperature gradients. They indicate the periods when the various runoff processes, such as glacier melt or snow melt, dominate the basin hydrograph. The annual cumulative curve of the difference between average daily temperature and melt threshold temperature over the basin, as well as the annual cumulative curve of average daily snowfall on the glacierized areas are used to identify the starting and end dates of snow and glacier ablation periods. Model parameters characterizing different runoff processes are calibrated on different HPCs in a stepwise and iterative way. Results show that the HPC-based method (1) delivers model-internal consistency comparably to the tri-data set calibration method; (2) improves the stability of calibrated parameter values across various calibration periods; and (3) estimates the contributions of runoff components similarly to the tri-data set calibration method. Our findings indicate the potential of the HPC-based approach as an alternative for hydrological model calibration in glacierized basins where other calibration data sets than discharge are often not available or very costly to obtain.
KW - hydrograph partitioning curves
KW - model calibration
KW - glacierized basins
Y1 - 2018
U6 - https://doi.org/10.1002/2017WR021966
SN - 0043-1397
SN - 1944-7973
VL - 54
IS - 3
SP - 2336
EP - 2361
PB - American Geophysical Union
CY - Washington
ER -
TY - JOUR
A1 - Metin, Ayse Duha
A1 - Dung, Nguyen Viet
A1 - Schröter, Kai
A1 - Vorogushyn, Sergiy
A1 - Guse, Björn
A1 - Kreibich, Heidi
A1 - Merz, Bruno
T1 - The role of spatial dependence for large-scale flood risk estimation
JF - Natural hazards and earth system sciences
N2 - Flood risk assessments are typically based on scenarios which assume homogeneous return periods of flood peaks throughout the catchment. This assumption is unrealistic for real flood events and may bias risk estimates for specific return periods. We investigate how three assumptions about the spatial dependence affect risk estimates: (i) spatially homogeneous scenarios (complete dependence), (ii) spatially heterogeneous scenarios (modelled dependence) and (iii) spatially heterogeneous but uncorrelated scenarios (complete independence). To this end, the model chain RFM (regional flood model) is applied to the Elbe catchment in Germany, accounting for the spatio-temporal dynamics of all flood generation processes, from the rainfall through catchment and river system processes to damage mechanisms. Different assumptions about the spatial dependence do not influence the expected annual damage (EAD); however, they bias the risk curve, i.e. the cumulative distribution function of damage. The widespread assumption of complete dependence strongly overestimates flood damage of the order of 100% for return periods larger than approximately 200 years. On the other hand, for small and medium floods with return periods smaller than approximately 50 years, damage is underestimated. The overestimation aggravates when risk is estimated for larger areas. This study demonstrates the importance of representing the spatial dependence of flood peaks and damage for risk assessments.
Y1 - 2020
U6 - https://doi.org/10.5194/nhess-20-967-2020
SN - 1561-8633
SN - 1684-9981
VL - 20
IS - 4
SP - 967
EP - 979
PB - European Geosciences Union (EGU) ; Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Kreibich, Heidi
A1 - Di Baldassarre, Giuliano
A1 - Vorogushyn, Sergiy
A1 - Aerts, Jeroen C. J. H.
A1 - Apel, Heiko
A1 - Aronica, Giuseppe T.
A1 - Arnbjerg-Nielsen, Karsten
A1 - Bouwer, Laurens M.
A1 - Bubeck, Philip
A1 - Caloiero, Tommaso
A1 - Chinh, Do T.
A1 - Cortes, Maria
A1 - Gain, Animesh K.
A1 - Giampa, Vincenzo
A1 - Kuhlicke, Christian
A1 - Kundzewicz, Zbigniew W.
A1 - Llasat, Maria Carmen
A1 - Mard, Johanna
A1 - Matczak, Piotr
A1 - Mazzoleni, Maurizio
A1 - Molinari, Daniela
A1 - Dung, Nguyen V.
A1 - Petrucci, Olga
A1 - Schröter, Kai
A1 - Slager, Kymo
A1 - Thieken, Annegret
A1 - Ward, Philip J.
A1 - Merz, Bruno
T1 - Adaptation to flood risk
BT - Results of international paired flood event studies
JF - Earth's Future
N2 - As flood impacts are increasing in large parts of the world, understanding the primary drivers of changes in risk is essential for effective adaptation. To gain more knowledge on the basis of empirical case studies, we analyze eight paired floods, that is, consecutive flood events that occurred in the same region, with the second flood causing significantly lower damage. These success stories of risk reduction were selected across different socioeconomic and hydro-climatic contexts. The potential of societies to adapt is uncovered by describing triggered societal changes, as well as formal measures and spontaneous processes that reduced flood risk. This novel approach has the potential to build the basis for an international data collection and analysis effort to better understand and attribute changes in risk due to hydrological extremes in the framework of the IAHSs Panta Rhei initiative. Across all case studies, we find that lower damage caused by the second event was mainly due to significant reductions in vulnerability, for example, via raised risk awareness, preparedness, and improvements of organizational emergency management. Thus, vulnerability reduction plays an essential role for successful adaptation. Our work shows that there is a high potential to adapt, but there remains the challenge to stimulate measures that reduce vulnerability and risk in periods in which extreme events do not occur.
KW - flooding
KW - vulnerability
KW - global environmental change
KW - adaptation
Y1 - 2017
U6 - https://doi.org/10.1002/2017EF000606
SN - 2328-4277
VL - 5
SP - 953
EP - 965
PB - Wiley
CY - Hoboken
ER -
TY - JOUR
A1 - Tarasova, Larisa
A1 - Merz, Ralf
A1 - Kiss, Andrea
A1 - Basso, Stefano
A1 - Blöchl, Günter
A1 - Merz, Bruno
A1 - Viglione, Alberto
A1 - Plötner, Stefan
A1 - Guse, Björn
A1 - Schumann, Andreas
A1 - Fischer, Svenja
A1 - Ahrens, Bodo
A1 - Anwar, Faizan
A1 - Bárdossy, András
A1 - Bühler, Philipp
A1 - Haberlandt, Uwe
A1 - Kreibich, Heidi
A1 - Krug, Amelie
A1 - Lun, David
A1 - Müller-Thomy, Hannes
A1 - Pidoto, Ross
A1 - Primo, Cristina
A1 - Seidel, Jochen
A1 - Vorogushyn, Sergiy
A1 - Wietzke, Luzie
T1 - Causative classification of river flood events
JF - Wiley Interdisciplinary Reviews : Water
N2 - A wide variety of processes controls the time of occurrence, duration, extent, and severity of river floods. Classifying flood events by their causative processes may assist in enhancing the accuracy of local and regional flood frequency estimates and support the detection and interpretation of any changes in flood occurrence and magnitudes. This paper provides a critical review of existing causative classifications of instrumental and preinstrumental series of flood events, discusses their validity and applications, and identifies opportunities for moving toward more comprehensive approaches. So far no unified definition of causative mechanisms of flood events exists. Existing frameworks for classification of instrumental and preinstrumental series of flood events adopt different perspectives: hydroclimatic (large-scale circulation patterns and atmospheric state at the time of the event), hydrological (catchment scale precipitation patterns and antecedent catchment state), and hydrograph-based (indirectly considering generating mechanisms through their effects on hydrograph characteristics). All of these approaches intend to capture the flood generating mechanisms and are useful for characterizing the flood processes at various spatial and temporal scales. However, uncertainty analyses with respect to indicators, classification methods, and data to assess the robustness of the classification are rarely performed which limits the transferability across different geographic regions. It is argued that more rigorous testing is needed. There are opportunities for extending classification methods to include indicators of space-time dynamics of rainfall, antecedent wetness, and routing effects, which will make the classification schemes even more useful for understanding and estimating floods. This article is categorized under: Science of Water > Water Extremes Science of Water > Hydrological Processes Science of Water > Methods
KW - flood genesis
KW - flood mechanisms
KW - flood typology
KW - historical floods
KW - hydroclimatology of floods
Y1 - 2019
U6 - https://doi.org/10.1002/wat2.1353
SN - 2049-1948
VL - 6
IS - 4
PB - Wiley
CY - Hoboken
ER -
TY - JOUR
A1 - Gerlitz, Lars
A1 - Steirou, Eva
A1 - Schneider, Christoph
A1 - Moron, Vincent
A1 - Vorogushyn, Sergiy
A1 - Merz, Bruno
T1 - Variability of the Cold Season Climate in Central Asia. Part II: Hydroclimatic Predictability
JF - Journal of climate
N2 - Central Asia (CA) is subjected to a large variability of precipitation. This study presents a statistical model, relating precipitation anomalies in three subregions of CA in the cold season (November-March) with various predictors in the preceding October. Promising forecast skill is achieved for two subregions covering 1) Uzbekistan, Turkmenistan, Kyrgyzstan, Tajikistan, and southern Kazakhstan and 2) Iran, Afghanistan, and Pakistan. ENSO in October is identified as the major predictor. Eurasian snow cover and the quasi-biennial oscillation further improve the forecast performance. To understand the physical mechanisms, an analysis of teleconnections between these predictors and the wintertime circulation over CA is conducted. The correlation analysis of predictors and large-scale circulation indices suggests a seasonal persistence of tropical circulation modes and a dynamical forcing of the westerly circulation by snow cover variations over Eurasia. An EOF analysis of pressure and humidity patterns allows separating the circulation variability over CA into westerly and tropical modes and confirms that the identified predictors affect the respective circulation characteristics. Based on the previously established weather type classification for CA, the predictors are investigated with regard to their effect on the regional circulation. The results suggest a modification of the Hadley cell due to ENSO variations, with enhanced moisture supply from the Arabian Gulf during El Nino. They further indicate an influence of Eurasian snow cover on the wintertime Arctic Oscillation (AO) and Northern Hemispheric Rossby wave tracks. Positive anomalies favor weather types associated with dry conditions, while negative anomalies promote the formation of a quasi-stationary trough over CA, which typically occurs during positive AO conditions.
KW - Asia
KW - Climate prediction
KW - Seasonal forecasting
KW - North Atlantic Oscillation
KW - Southern Oscillation
Y1 - 2019
U6 - https://doi.org/10.1175/JCLI-D-18-0892.1
SN - 0894-8755
SN - 1520-0442
VL - 32
IS - 18
SP - 6015
EP - 6033
PB - American Meteorological Soc.
CY - Boston
ER -
TY - JOUR
A1 - He, Zhihua
A1 - Unger-Shayesteh, Katy
A1 - Vorogushyn, Sergiy
A1 - Weise, Stephan M.
A1 - Kalashnikova, Olga
A1 - Gafurov, Abror
A1 - Duethmann, Doris
A1 - Barandun, Martina
A1 - Merz, Bruno
T1 - Constraining hydrological model parameters using water isotopic compositions in a glacierized basin, Central Asia
JF - Journal of hydrology
N2 - Water stable isotope signatures can provide valuable insights into the catchment internal runoff processes. However, the ability of the water isotope data to constrain the internal apportionments of runoff components in hydrological models for glacierized basins is not well understood. This study developed an approach to simultaneously model the water stable isotopic compositions and runoff processes in a glacierized basin in Central Asia. The fractionation and mixing processes of water stable isotopes in and from the various water sources were integrated into a glacio-hydrological model. The model parameters were calibrated on discharge, snow cover and glacier mass balance data, and additionally isotopic composition of streamflow. We investigated the value of water isotopic compositions for the calibration of model parameters, in comparison to calibration methods without using such measurements. Results indicate that: (1) The proposed isotope-hydrological integrated modeling approach was able to reproduce the isotopic composition of streamflow, and improved the model performance in the evaluation period; (2) Involving water isotopic composition for model calibration reduced the model parameter uncertainty, and helped to reduce the uncertainty in the quantification of runoff components; (3) The isotope-hydrological integrated modeling approach quantified the contributions of runoff components comparably to a three-component tracer-based end-member mixing analysis method for summer peak flows, and required less water tracer data. Our findings demonstrate the value of water isotopic compositions to improve the quantification of runoff components using hydrological models in glacierized basins.
KW - Water stable isotope
KW - Isotope-hydrological integrated modeling
KW - Quantification of runoff components
KW - Glacierized basins
Y1 - 2019
U6 - https://doi.org/10.1016/j.jhydrol.2019.01.048
SN - 0022-1694
SN - 1879-2707
VL - 571
SP - 332
EP - 348
PB - Elsevier
CY - Amsterdam
ER -
TY - GEN
A1 - Metin, Ayse Duha
A1 - Dung, Nguyen Viet
A1 - Schröter, Kai
A1 - Guse, Björn
A1 - Apel, Heiko
A1 - Kreibich, Heidi
A1 - Vorogushyn, Sergiy
A1 - Merz, Bruno
T1 - How do changes along the risk chain affect flood risk?
T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - Flood risk is impacted by a range of physical and socio-economic processes. Hence, the quantification of flood risk ideally considers the complete flood risk chain, from atmospheric processes through catchment and river system processes to damage mechanisms in the affected areas. Although it is generally accepted that a multitude of changes along the risk chain can occur and impact flood risk, there is a lack of knowledge of how and to what extent changes in influencing factors propagate through the chain and finally affect flood risk. To fill this gap, we present a comprehensive sensitivity analysis which considers changes in all risk components, i.e. changes in climate, catchment, river system, land use, assets, and vulnerability. The application of this framework to the mesoscale Mulde catchment in Germany shows that flood risk can vary dramatically as a consequence of plausible change scenarios. It further reveals that components that have not received much attention, such as changes in dike systems or in vulnerability, may outweigh changes in often investigated components, such as climate. Although the specific results are conditional on the case study area and the selected assumptions, they emphasize the need for a broader consideration of potential drivers of change in a comprehensive way. Hence, our approach contributes to a better understanding of how the different risk components influence the overall flood risk.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 1067
KW - global sensitivity analysis
KW - climate change
KW - river floods
KW - frequency
KW - Europe
KW - model
KW - vulnerability
KW - adaptation
KW - strategies
KW - catchment
Y1 - 2021
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-468790
SN - 1866-8372
IS - 1067
ER -
TY - THES
A1 - Vorogushyn, Sergiy
T1 - Analysis of flood hazard under consideration of dike breaches
T1 - Analyse der Hochwassergefährdung unter Berücksichtigung von Deichbrüchen
N2 - River reaches protected by dikes exhibit high damage potential due to strong value accumulation in the hinterland areas. While providing an efficient protection against low magnitude flood events, dikes may fail under the load of extreme water levels and long flood durations. Hazard and risk assessments for river reaches protected by dikes have not adequately considered the fluvial inundation processes up to now. Particularly, the processes of dike failures and their influence on the hinterland inundation and flood wave propagation lack comprehensive consideration. This study focuses on the development and application of a new modelling system which allows a comprehensive flood hazard assessment along diked river reaches under consideration of dike failures. The proposed Inundation Hazard Assessment Model (IHAM) represents a hybrid probabilistic-deterministic model. It comprises three models interactively coupled at runtime. These are: (1) 1D unsteady hydrodynamic model of river channel and floodplain flow between dikes, (2) probabilistic dike breach model which determines possible dike breach locations, breach widths and breach outflow discharges, and (3) 2D raster-based diffusion wave storage cell model of the hinterland areas behind the dikes. Due to the unsteady nature of the 1D and 2D coupled models, the dependence between hydraulic load at various locations along the reach is explicitly considered. The probabilistic dike breach model describes dike failures due to three failure mechanisms: overtopping, piping and slope instability caused by the seepage flow through the dike core (micro-instability). The 2D storage cell model driven by the breach outflow boundary conditions computes an extended spectrum of flood intensity indicators such as water depth, flow velocity, impulse, inundation duration and rate of water rise. IHAM is embedded in a Monte Carlo simulation in order to account for the natural variability of the flood generation processes reflected in the form of input hydrographs and for the randomness of dike failures given by breach locations, times and widths. The model was developed and tested on a ca. 91 km heavily diked river reach on the German part of the Elbe River between gauges Torgau and Vockerode. The reach is characterised by low slope and fairly flat extended hinterland areas. The scenario calculations for the developed synthetic input hydrographs for the main river and tributary were carried out for floods with return periods of T = 100, 200, 500, 1000 a. Based on the modelling results, probabilistic dike hazard maps could be generated that indicate the failure probability of each discretised dike section for every scenario magnitude. In the disaggregated display mode, the dike hazard maps indicate the failure probabilities for each considered breach mechanism. Besides the binary inundation patterns that indicate the probability of raster cells being inundated, IHAM generates probabilistic flood hazard maps. These maps display spatial patterns of the considered flood intensity indicators and their associated return periods. Finally, scenarios of polder deployment for the extreme floods with T = 200, 500, 1000 were simulated with IHAM. The developed IHAM simulation system represents a new scientific tool for studying fluvial inundation dynamics under extreme conditions incorporating effects of technical flood protection measures. With its major outputs in form of novel probabilistic inundation and dike hazard maps, the IHAM system has a high practical value for decision support in flood management.
N2 - Entlang eingedeichter Flussabschnitte kann das Hinterland ein hohes Schadenspotential, aufgrund der starken Akkumulation der Werte, aufweisen. Obwohl Deiche einen effizienten Schutz gegen kleinere häufiger auftretende Hochwässer bieten, können sie unter der Last hoher Wasserstände sowie langer Anstaudauer versagen. Gefährdungs- und Risikoabschätzungsmethoden für die eingedeichten Flussstrecken haben bisher die fluvialen Überflutungsprozesse nicht hinreichend berücksichtigt. Besonders, die Prozesse der Deichbrüche und deren Einfluss auf Überflutung im Hinterland und Fortschreiten der Hochwasserwelle verlangen eine umfassende Betrachtung. Die vorliegende Studie setzt ihren Fokus auf die Entwicklung und Anwendung eines neuen Modellierungssystems, das eine umfassende Hochwassergefährdungsanalyse entlang eingedeichter Flussstrecken unter Berücksichtigung von Deichbrüchen ermöglicht. Das vorgeschlagene Inundation Hazard Assessment Model (IHAM) stellt ein hybrides probabilistisch-deterministisches Modell dar. Es besteht aus drei laufzeitgekoppelten Modellen: (1) einem 1D instationären hydrodynamisch-numerischen Modell für den Flussschlauch und die Vorländer zwischen den Deichen, (2) einem probabilistischen Deichbruchmodell, welches die möglichen Bruchstellen, Breschenbreiten und Breschenausflüsse berechnet, und (3) einem 2D raster-basierten Überflutungsmodell für das Hinterland, das auf dem Speiherzellenansatz und der Diffusionswellengleichung basiert ist. Das probabilistische Deichbruchmodell beschreibt Deichbrüche, die infolge von drei Bruchmechanismen auftreten: dem Überströmen, dem Piping im Deichuntergrund und dem Versagen der landseitigen Böschung als Folge des Sickerflusses und der Erosion im Deichkörper (Mikro-Instabilität). Das 2D Speicherzellenmodell, angetrieben durch den Breschenausfluss als Randbedingung, berechnet ein erweitertes Spektrum der Hochwasserintensitätsindikatoren wie: Überflutungstiefe, Fliessgeschwindigkeit, Impuls, Überflutungsdauer und Wasseranstiegsrate. IHAM wird im Rahmen einer Monte Carlo Simulation ausgeführt und berücksichtigt die natürliche Variabilität der Hochwasserentstehungsprozesse, die in der Form der Hydrographen und deren Häufigkeit abgebildet wird, und die Zufälligkeit des Deichversagens, gegeben durch die Lokationen der Bruchstellen, der Zeitpunkte der Brüche und der Breschenbreiten. Das Modell wurde entwickelt und getestet an einem ca. 91 km langen Flussabschnitt. Dieser Flussabschnitt ist durchgängig eingedeicht und befindet sich an der deutschen Elbe zwischen den Pegeln Torgau und Vockerode. Die Szenarioberechnungen wurden von synthetischen Hydrographen für den Hauptstrom und Nebenfluss angetrieben, die für Hochwässer mit Wiederkehrintervallen von 100, 200, 500, und 1000 Jahren entwickelt wurden. Basierend auf den Modellierungsergebnissen wurden probabilistische Deichgefährdungskarten generiert. Sie zeigen die Versagenswahrscheinlichkeiten der diskretisierten Deichabschnitte für jede modellierte Hochwassermagnitude. Die Deichgefährdungskarten im disaggregierten Darstellungsmodus zeigen die Bruchwahrscheinlichkeiten für jeden betrachteten Bruchmechanismus. Neben den binären Überflutungsmustern, die die Wahrscheinlichkeit der Überflutung jeder Rasterzelle im Hinterland zeigen, generiert IHAM probabilistische Hochwassergefährdungskarten. Diese Karten stellen räumliche Muster der in Betracht gezogenen Hochwasserintensitätsindikatoren und entsprechende Jährlichkeiten dar. Schließlich, wurden mit IHAM Szenarien mit Aktivierung vom Polder bei extremen Hochwässern mit Jährlichkeiten von 200, 500, 1000 Jahren simuliert. Das entwickelte IHAM Modellierungssystem stellt ein neues wissenschaftliches Werkzeug für die Untersuchung fluvialer Überflutungsdynamik in extremen Hochwassersituationen unter Berücksichtigung des Einflusses technischer Hochwasserschutzmaßnahmen dar. Das IHAM System hat eine hohe praktische Bedeutung für die Entscheidungsunterstützung im Hochwassermanagement aufgrund der neuartigen Deichbruch- und Hochwassergefährdungskarten, die das Hauptprodukt der Simulationen darstellen.
KW - Hochwasser
KW - Deichbruch
KW - Unsicherheitsanalyse
KW - Gefährdungskarten
KW - Polder
KW - Flood
KW - dike breach
KW - uncertainty analysis
KW - hazard maps
KW - polder
Y1 - 2008
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus-27646
ER -
TY - GEN
A1 - Murawski, Aline
A1 - Bürger, Gerd
A1 - Vorogushyn, Sergiy
A1 - Merz, Bruno
T1 - Can local climate variability be explained by weather patterns?
BT - a multi-station evaluation for the Rhine basin
T2 - Postprints der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe
N2 - To understand past flood changes in the Rhine catchment and in particular the role of anthropogenic climate change in extreme flows, an attribution study relying on a proper GCM (general circulation model) downscaling is needed. A downscaling based on conditioning a stochastic weather generator on weather patterns is a promising approach. This approach assumes a strong link between weather patterns and local climate, and sufficient GCM skill in reproducing weather pattern climatology. These presuppositions are unprecedentedly evaluated here using 111 years of daily climate data from 490 stations in the Rhine basin and comprehensively testing the number of classification parameters and GCM weather pattern characteristics. A classification based on a combination of mean sea level pressure, temperature, and humidity from the ERA20C reanalysis of atmospheric fields over central Europe with 40 weather types was found to be the most appropriate for stratifying six local climate variables. The corresponding skill is quite diverse though, ranging from good for radiation to poor for precipitation. Especially for the latter it was apparent that pressure fields alone cannot sufficiently stratify local variability. To test the skill of the latest generation of GCMs from the CMIP5 ensemble in reproducing the frequency, seasonality, and persistence of the derived weather patterns, output from 15 GCMs is evaluated. Most GCMs are able to capture these characteristics well, but some models showed consistent deviations in all three evaluation criteria and should be excluded from further attribution analysis.
T3 - Zweitveröffentlichungen der Universität Potsdam : Mathematisch-Naturwissenschaftliche Reihe - 525
KW - athmospheric circulation patterns
KW - stochastic rainfall model
KW - within-type variability
KW - river Rhine
KW - precipitation
KW - temperature
KW - trends
KW - classification
KW - Europe
KW - scenarios
Y1 - 2019
U6 - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:kobv:517-opus4-410155
SN - 1866-8372
IS - 525
ER -
TY - JOUR
A1 - Macdonald, Elena
A1 - Merz, Bruno
A1 - Guse, Björn
A1 - Wietzke, Luzie
A1 - Ullrich, Sophie
A1 - Kemter, Matthias
A1 - Ahrens, Bodo
A1 - Vorogushyn, Sergiy
T1 - Event and catchment controls of heavy tail behavior of floods
JF - Water resources research
N2 - In some catchments, the distribution of annual maximum streamflow shows heavy tail behavior, meaning the occurrence probability of extreme events is higher than if the upper tail decayed exponentially. Neglecting heavy tail behavior can lead to an underestimation of the likelihood of extreme floods and the associated risk. Partly contradictory results regarding the controls of heavy tail behavior exist in the literature and the knowledge is still very dispersed and limited. To better understand the drivers, we analyze the upper tail behavior and its controls for 480 catchments in Germany and Austria over a period of more than 50 years. The catchments span from quickly reacting mountain catchments to large lowland catchments, allowing for general conclusions. We compile a wide range of event and catchment characteristics and investigate their association with an indicator of the tail heaviness of flood distributions, namely the shape parameter of the GEV distribution. Following univariate analyses of these characteristics, along with an evaluation of different aggregations of event characteristics, multiple linear regression models, as well as random forests, are constructed. A novel slope indicator, which represents the relation between the return period of flood peaks and event characteristics, captures the controls of heavy tails best. Variables describing the catchment response are found to dominate the heavy tail behavior, followed by event precipitation, flood seasonality, and catchment size. The pre-event moisture state in a catchment has no relevant impact on the tail heaviness even though it does influence flood magnitudes.
KW - heavy tail behavior
KW - floods
KW - event characteristics
KW - catchment
KW - characteristics
KW - catchment response
Y1 - 2022
U6 - https://doi.org/10.1029/2021WR031260
SN - 0043-1397
SN - 1944-7973
VL - 58
IS - 6
PB - American Geophysical Union
CY - Washington
ER -
TY - JOUR
A1 - Barendrecht, Marlies H.
A1 - Viglione, Alberto
A1 - Kreibich, Heidi
A1 - Merz, Bruno
A1 - Vorogushyn, Sergiy
A1 - Blöschl, G.
T1 - The Value of Empirical Data for Estimating the Parameters of a Sociohydrological Flood Risk Model
JF - Water resources research
N2 - In this paper, empirical data are used to estimate the parameters of a sociohydrological flood risk model. The proposed model, which describes the interactions between floods, settlement density, awareness, preparedness, and flood loss, is based on the literature. Data for the case study of Dresden, Germany, over a period of 200years, are used to estimate the model parameters through Bayesian inference. The credibility bounds of their estimates are small, even though the data are rather uncertain. A sensitivity analysis is performed to examine the value of the different data sources in estimating the model parameters. In general, the estimated parameters are less biased when using data at the end of the modeled period. Data about flood awareness are the most important to correctly estimate the parameters of this model and to correctly model the system dynamics. Using more data for other variables cannot compensate for the absence of awareness data. More generally, the absence of data mostly affects the estimation of the parameters that are directly related to the variable for which data are missing. This paper demonstrates that combining sociohydrological modeling and empirical data gives additional insights into the sociohydrological system, such as quantifying the forgetfulness of the society, which would otherwise not be easily achieved by sociohydrological models without data or by standard statistical analysis of empirical data.
Y1 - 2019
U6 - https://doi.org/10.1029/2018WR024128
SN - 0043-1397
SN - 1944-7973
VL - 55
IS - 2
SP - 1312
EP - 1336
PB - American Geophysical Union
CY - Washington
ER -
TY - JOUR
A1 - Sairam, Nivedita
A1 - Brill, Fabio Alexander
A1 - Sieg, Tobias
A1 - Farrag, Mostafa
A1 - Kellermann, Patric
A1 - Viet Dung Nguyen,
A1 - Lüdtke, Stefan
A1 - Merz, Bruno
A1 - Schröter, Kai
A1 - Vorogushyn, Sergiy
A1 - Kreibich, Heidi
T1 - Process-based flood risk assessment for Germany
JF - Earth's future / American Geophysical Union
N2 - Large-scale flood risk assessments are crucial for decision making, especially with respect to new flood defense schemes, adaptation planning and estimating insurance premiums. We apply the process-based Regional Flood Model (RFM) to simulate a 5000-year flood event catalog for all major catchments in Germany and derive risk curves based on the losses per economic sector. The RFM uses a continuous process simulation including a multisite, multivariate weather generator, a hydrological model considering heterogeneous catchment processes, a coupled 1D-2D hydrodynamic model considering dike overtopping and hinterland storage, spatially explicit sector-wise exposure data and empirical multi-variable loss models calibrated for Germany. For all components, uncertainties in the data and models are estimated. We estimate the median Expected Annual Damage (EAD) and Value at Risk at 99.5% confidence for Germany to be euro0.529 bn and euro8.865 bn, respectively. The commercial sector dominates by making about 60% of the total risk, followed by the residential sector. The agriculture sector gets affected by small return period floods and only contributes to less than 3% to the total risk. The overall EAD is comparable to other large-scale estimates. However, the estimation of losses for specific return periods is substantially improved. The spatial consistency of the risk estimates avoids the large overestimation of losses for rare events that is common in other large-scale assessments with homogeneous return periods. Thus, the process-based, spatially consistent flood risk assessment by RFM is an important step forward and will serve as a benchmark for future German-wide flood risk assessments.
KW - risk model chain
KW - continuous simulation
KW - expected annual damage
KW - risk
KW - curves
KW - multi-sector risk
Y1 - 2021
U6 - https://doi.org/10.1029/2021EF002259
SN - 2328-4277
VL - 9
IS - 10
PB - Wiley-Blackwell
CY - Hoboken, NJ
ER -
TY - JOUR
A1 - Winter, Benjamin
A1 - Schneeberger, Klaus
A1 - Dung, N. V.
A1 - Huttenlau, M.
A1 - Achleitner, S.
A1 - Stötter, J.
A1 - Merz, Bruno
A1 - Vorogushyn, Sergiy
T1 - A continuous modelling approach for design flood estimation on sub-daily time scale
JF - Hydrological sciences journal = Journal des sciences hydrologiques
N2 - Design flood estimation is an essential part of flood risk assessment. Commonly applied are flood frequency analyses and design storm approaches, while the derived flood frequency using continuous simulation has been getting more attention recently. In this study, a continuous hydrological modelling approach on an hourly time scale, driven by a multi-site weather generator in combination with a -nearest neighbour resampling procedure, based on the method of fragments, is applied. The derived 100-year flood estimates in 16 catchments in Vorarlberg (Austria) are compared to (a) the flood frequency analysis based on observed discharges, and (b) a design storm approach. Besides the peak flows, the corresponding runoff volumes are analysed. The spatial dependence structure of the synthetically generated flood peaks is validated against observations. It can be demonstrated that the continuous modelling approach can achieve plausible results and shows a large variability in runoff volume across the flood events.
KW - derived flood frequency
KW - continuous modelling
KW - temporal disaggregation
KW - flood hazard
KW - synthetic flood events
Y1 - 2019
U6 - https://doi.org/10.1080/02626667.2019.1593419
SN - 0262-6667
SN - 2150-3435
VL - 64
IS - 5
SP - 539
EP - 554
PB - Routledge, Taylor & Francis Group
CY - Abingdon
ER -
TY - JOUR
A1 - Merz, Bruno
A1 - Vorogushyn, Sergiy
A1 - Lall, Upmanu
A1 - Viglione, Alberto
A1 - Blöschl, Günter
T1 - Charting unknown waters-On the role of surprise in flood risk assessment and management
JF - Water resources research
N2 - Unexpected incidents, failures, and disasters are abundant in the history of flooding events. In this paper, we introduce the metaphors of terra incognita and terra maligna to illustrate unknown and wicked flood situations, respectively. We argue that surprise is a neglected element in flood risk assessment and management. Two sources of surprise are identified: (1) the complexity of flood risk systems, represented by nonlinearities, interdependencies, and nonstationarities and (2) cognitive biases in human perception and decision making. Flood risk assessment and management are particularly prone to cognitive biases due to the rarity and uniqueness of extremes, and the nature of human risk perception. We reflect on possible approaches to better understanding and reducing the potential for surprise and its adverse consequences which may be supported by conceptually charting maps that separate terra incognita from terra cognita, and terra maligna from terra benigna. We conclude that flood risk assessment and management should account for the potential for surprise and devastating consequences which will require a shift in thinking.
Y1 - 2015
U6 - https://doi.org/10.1002/2015WR017464
SN - 0043-1397
SN - 1944-7973
VL - 51
IS - 8
SP - 6399
EP - 6416
PB - American Geophysical Union
CY - Washington
ER -
TY - JOUR
A1 - Duethmann, Doris
A1 - Bolch, Tobias
A1 - Farinotti, Daniel
A1 - Kriegel, David
A1 - Vorogushyn, Sergiy
A1 - Merz, Bruno
A1 - Pieczonka, Tino
A1 - Jiang, Tong
A1 - Su, Buda
A1 - Güntner, Andreas
T1 - Attribution of streamflow trends in snow and glacier melt-dominated catchments of the Tarim River, Central Asia
JF - Water resources research
N2 - Observed streamflow of headwater catchments of the Tarim River (Central Asia) increased by about 30% over the period 1957-2004. This study aims at assessing to which extent these streamflow trends can be attributed to changes in air temperature or precipitation. The analysis includes a data-based approach using multiple linear regression and a simulation-based approach using a hydrological model. The hydrological model considers changes in both glacier area and surface elevation. It was calibrated using a multiobjective optimization algorithm with calibration criteria based on glacier mass balance and daily and interannual variations of discharge. The individual contributions to the overall streamflow trends from changes in glacier geometry, temperature, and precipitation were assessed using simulation experiments with a constant glacier geometry and with detrended temperature and precipitation time series. The results showed that the observed changes in streamflow were consistent with the changes in temperature and precipitation. In the Sari-Djaz catchment, increasing temperatures and related increase of glacier melt were identified as the dominant driver, while in the Kakshaal catchment, both increasing temperatures and increasing precipitation played a major role. Comparing the two approaches, an advantage of the simulation-based approach is the fact that it is based on process-based relationships implemented in the hydrological model instead of statistical links in the regression model. However, data-based approaches are less affected by model parameter and structural uncertainties and typically fast to apply. A complementary application of both approaches is recommended.
KW - trend analysis
KW - data-based
KW - simulation-based
KW - multiobjective calibration
KW - hydrological modeling
KW - glacier melt
Y1 - 2015
U6 - https://doi.org/10.1002/2014WR016716
SN - 0043-1397
SN - 1944-7973
VL - 51
IS - 6
SP - 4727
EP - 4750
PB - American Geophysical Union
CY - Washington
ER -
TY - JOUR
A1 - Metin, Ayse Duha
A1 - Nguyen Viet Dung,
A1 - Schröter, Kai
A1 - Guse, Björn
A1 - Apel, Heiko
A1 - Kreibich, Heidi
A1 - Vorogushyn, Sergiy
A1 - Merz, Bruno
T1 - How do changes along the risk chain affect flood risk?
JF - Natural hazards and earth system sciences
N2 - Flood risk is impacted by a range of physical and socio-economic processes. Hence, the quantification of flood risk ideally considers the complete flood risk chain, from atmospheric processes through catchment and river system processes to damage mechanisms in the affected areas. Although it is generally accepted that a multitude of changes along the risk chain can occur and impact flood risk, there is a lack of knowledge of how and to what extent changes in influencing factors propagate through the chain and finally affect flood risk. To fill this gap, we present a comprehensive sensitivity analysis which considers changes in all risk components, i.e. changes in climate, catchment, river system, land use, assets, and vulnerability. The application of this framework to the mesoscale Mulde catchment in Germany shows that flood risk can vary dramatically as a consequence of plausible change scenarios. It further reveals that components that have not received much attention, such as changes in dike systems or in vulnerability, may outweigh changes in often investigated components, such as climate. Although the specific results are conditional on the case study area and the selected assumptions, they emphasize the need for a broader consideration of potential drivers of change in a comprehensive way. Hence, our approach contributes to a better understanding of how the different risk components influence the overall flood risk.
Y1 - 2018
U6 - https://doi.org/10.5194/nhess-18-3089-2018
SN - 1561-8633
SN - 1684-9981
VL - 18
IS - 11
SP - 3089
EP - 3108
PB - Copernicus
CY - Göttingen
ER -
TY - JOUR
A1 - Murawski, Aline
A1 - Vorogushyn, Sergiy
A1 - Bürger, Gerd
A1 - Gerlitz, Lars
A1 - Merz, Bruno
T1 - Do changing weather types explain observed climatic trends in the rhine basin?
BT - an analysis of within- and between-type changes
JF - Journal of geophysical of geophysical research-atmosheres
N2 - For attributing hydrological changes to anthropogenic climate change, catchment models are driven by climate model output. A widespread approach to bridge the spatial gap between global climate and hydrological catchment models is to use a weather generator conditioned on weather patterns (WPs). This approach assumes that changes in local climate are characterized by between-type changes of patterns. In this study we test this assumption by analyzing a previously developed WP classification for the Rhine basin, which is based on dynamic and thermodynamic variables. We quantify changes in pattern characteristics and associated climatic properties. The amount of between- and within-type changes is investigated by comparing observed trends to trends resulting solely from WP occurrence. To overcome uncertainties in trend detection resulting from the selected time period, all possible periods in 1901-2010 with a minimum length of 31 years are analyzed. Increasing frequency is found for some patterns associated with high precipitation, although the trend sign highly depends on the considered period. Trends and interannual variations of WP frequencies are related to the long-term variability of large-scale circulation modes. Long-term WP internal warming is evident for summer patterns and enhanced warming for spring/autumn patterns since the 1970s. Observed trends in temperature and partly in precipitation are mainly associated with frequency changes of specific WPs, but some amount of within-type changes remains. The classification can be used for downscaling of past changes considering this limitation, but the inclusion of thermodynamic variables into the classification impedes the downscaling of future climate projections.
KW - attribution
KW - weather pattern
KW - trend analysis
KW - downscaling
KW - hypothetical trend
Y1 - 2018
U6 - https://doi.org/10.1002/2017JD026654
SN - 2169-897X
SN - 2169-8996
VL - 123
IS - 3
SP - 1562
EP - 1584
PB - American Geophysical Union
CY - Washington
ER -
TY - JOUR
A1 - Merz, Bruno
A1 - Apel, Heiko
A1 - Dung Nguyen, Viet-Dung
A1 - Falter, Daniela
A1 - Guse, Björn
A1 - Hundecha, Yeshewatesfa
A1 - Kreibich, Heidi
A1 - Schröter, Kai
A1 - Vorogushyn, Sergiy
T1 - From precipitation to damage
BT - a coupled model chain for spatially coherent, large-scale flood risk assessment
JF - Global flood hazard : applications in modeling, mapping and forecasting
N2 - Flood risk assessments for large river basins often involve piecing together smaller-scale assessments leading to erroneous risk statements. We describe a coupled model chain for quantifying flood risk at the scale of 100,000 km(2). It consists of a catchment model, a 1D-2D river network model, and a loss model. We introduce the model chain and present two applications. The first application for the Elbe River basin with an area of 66,000 km(2) demonstrates that it is feasible to simulate the complete risk chain for large river basins in a continuous simulation mode with high temporal and spatial resolution. In the second application, RFM is coupled to a multisite weather generator and applied to the Mulde catchment with an area of 6,000 km(2). This approach is able to provide a very long time series of spatially heterogeneous patterns of precipitation, discharge, inundation, and damage. These patterns respect the spatial correlation of the different processes and are suitable to derive large-scale risk estimates. We discuss how the RFM approach can be transferred to the continental scale.
Y1 - 2018
SN - 978-1-119-21788-6
SN - 978-1-119-21786-2
U6 - https://doi.org/10.1002/9781119217886.ch10
SN - 0065-8448
VL - 233
SP - 169
EP - 183
PB - American Geophysical Union
CY - Washington
ER -
TY - JOUR
A1 - Wietzke, Luzie M.
A1 - Merz, Bruno
A1 - Gerlitz, Lars
A1 - Kreibich, Heidi
A1 - Guse, Björn
A1 - Castellarin, Attilio
A1 - Vorogushyn, Sergiy
T1 - Comparative analysis of scalar upper tail indicators
JF - Hydrological sciences journal = Journal des sciences hydrologiques
N2 - Different upper tail indicators exist to characterize heavy tail phenomena, but no comparative study has been carried out so far. We evaluate the shape parameter (GEV), obesity index, Gini index and upper tail ratio (UTR) against a novel benchmark of tail heaviness - the surprise factor. Sensitivity analyses to sample size and changes in scale-to-location ratio are carried out in bootstrap experiments. The UTR replicates the surprise factor best but is most uncertain and only comparable between records of similar length. For samples with symmetric Lorenz curves, shape parameter, obesity and Gini indices provide consistent indications. For asymmetric Lorenz curves, however, the first two tend to overestimate, whereas Gini index tends to underestimate tail heaviness. We suggest the use of a combination of shape parameter, obesity and Gini index to characterize tail heaviness. These indicators should be supported with calculation of the Lorenz asymmetry coefficients and interpreted with caution.
KW - upper tail behaviour
KW - heavy-tailed distributions
KW - extremes
KW - diagnostics
KW - surprise
Y1 - 2020
U6 - https://doi.org/10.1080/02626667.2020.1769104
SN - 0262-6667
SN - 2150-3435
VL - 65
IS - 10
SP - 1625
EP - 1639
PB - Routledge, Taylor & Francis Group
CY - Abingdon
ER -
TY - JOUR
A1 - Ullrich, Sophie Louise
A1 - Hegnauer, Mark
A1 - Nguyen, Dung Viet
A1 - Merz, Bruno
A1 - Kwadijk, Jaap
A1 - Vorogushyn, Sergiy
T1 - Comparative evaluation of two types of stochastic weather generators for synthetic precipitation in the Rhine basin
JF - Journal of hydrology
N2 - Stochastic modeling of precipitation for estimation of hydrological extremes is an important element of flood risk assessment and management. The spatially consistent estimation of rainfall fields and their temporal variability remains challenging and is addressed by various stochastic weather generators.
In this study, two types of weather generators are evaluated against observed data and benchmarked regarding their ability to simulate spatio-temporal precipitation fields in the Rhine catchment. A multi-site station-based weather generator uses an auto-regressive model and estimates the spatial correlation structure between stations. Another weather generator is raster-based and uses the nearest-neighbor resampling technique for reshuffling daily patterns while preserving the correlation structure between the observations.
Both weather generators perform well and are comparable at the point (station) scale with regards to daily mean and 99.9th percentile precipitation as well as concerning wet/dry frequencies and transition probabilities. The areal extreme precipitation at the sub-basin scale is however overestimated in the station-based weather generator due to an overestimation of the correlation structure between individual stations. The auto-regressive model tends to generate larger rainfall fields in space for extreme precipitation than observed, particularly in summer. The weather generator based on nearest-neighbor resampling reproduces the observed daily and multiday (5, 10 and 20) extreme events in a similar magnitude. Improvements in performance regarding wet frequencies and transition probabilities are recommended for both models.
KW - Rainfall generation
KW - Rainfall occurrence
KW - Multi-site stochastic weather
KW - generator
KW - Resampling weather generator
KW - Time series analysis
Y1 - 2021
U6 - https://doi.org/10.1016/j.jhydrol.2021.126544
SN - 0022-1694
SN - 1879-2707
VL - 601
PB - Elsevier
CY - Amsterdam [u.a.]
ER -
TY - JOUR
A1 - Farrag, Mostafa
A1 - Brill, Fabio Alexander
A1 - Nguyen, Viet Dung
A1 - Sairam, Nivedita
A1 - Schröter, Kai
A1 - Kreibich, Heidi
A1 - Merz, Bruno
A1 - de Bruijn, Karin M.
A1 - Vorogushyn, Sergiy
T1 - On the role of floodplain storage and hydrodynamic interactions in flood risk estimation
JF - Hydrological sciences journal = Journal des sciences hydrologiques
N2 - Hydrodynamic interactions, i.e. the floodplain storage effects caused by inundations upstream on flood wave propagation, inundation areas, and flood damage downstream, are important but often ignored in large-scale flood risk assessments. Although new methods considering these effects sometimes emerge, they are often limited to a small or meso scale. In this study, we investigate the role of hydrodynamic interactions and floodplain storage on flood hazard and risk in the German part of the Rhine basin. To do so, we compare a new continuous 1D routing scheme within a flood risk model chain to the piece-wise routing scheme, which largely neglects floodplain storage. The results show that floodplain storage is significant, lowers water levels and discharges, and reduces risks by over 50%. Therefore, for accurate risk assessments, a system approach must be adopted, and floodplain storage and hydrodynamic interactions must carefully be considered.
KW - hydrodynamic interactions
KW - derived flood risk analysis
KW - flood modelling;
KW - Rhine basin
Y1 - 2022
U6 - https://doi.org/10.1080/02626667.2022.2030058
SN - 0262-6667
SN - 2150-3435
VL - 67
IS - 4
SP - 508
EP - 534
PB - Routledge, Taylor & Francis Group
CY - Abingdon
ER -