TY - JOUR A1 - Creutzfeldt, Benjamin A1 - Troch, Peter A. A1 - Guentner, Andreas A1 - Ferre, Ty P. A. A1 - Gräff, Thomas A1 - Merz, Bruno T1 - Storage-discharge relationships at different catchment scales based on local high-precision gravimetry JF - Hydrological processes N2 - In hydrology, the storage-discharge relationship is a fundamental catchment property. Understanding what controls this relationship is at the core of catchment science. To date, there are no direct methods to measure water storage at catchment scales (10(1)-10(3)km(2)). In this study, we use direct measurements of terrestrial water storage dynamics by means of superconducting gravimetry in a small headwater catchment of the Regen River, Germany, to derive empirical storage-discharge relationships in nested catchments of increasing scale. Our results show that the local storage measurements are strongly related to streamflow dynamics at larger scales (> 100km(2); correlation coefficient=0.78-0.81), but at small scale, no such relationship exists (similar to 1km(2); correlation coefficients=-0.11). The geologic setting in the region can explain both the disconnection between local water storage and headwater runoff, and the connectivity between headwater storage and streams draining larger catchment areas. More research is required to understand what controls the form of the observed storage-discharge relationships at the catchment scale. This study demonstrates that high-precision gravimetry can provide new insights into the complex relationship between state and response of hydrological systems. KW - water storage KW - high-precision gravimeter KW - storage-discharge relationship KW - nested catchments Y1 - 2014 U6 - https://doi.org/10.1002/hyp.9689 SN - 0885-6087 SN - 1099-1085 VL - 28 IS - 3 SP - 1465 EP - 1475 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Delgado, Jose Miguel Martins A1 - Merz, Bruno A1 - Apel, Heiko T1 - Projecting flood hazard under climate change: an alternative approach to model chains JF - Natural hazards and earth system sciences N2 - Flood hazard projections under climate change are typically derived by applying model chains consisting of the following elements: "emission scenario - global climate model - downscaling, possibly including bias correction hydrological model - flood frequency analysis". To date, this approach yields very uncertain results, due to the difficulties of global and regional climate models to represent precipitation. The implementation of such model chains requires major efforts, and their complexity is high. We propose for the Mekong River an alternative approach which is based on a shortened model chain: "emission scenario - global climate model - non-stationary flood frequency model". The underlying idea is to use a link between the Western Pacific monsoon and local flood characteristics: the variance of the monsoon drives a non-stationary flood frequency model, yielding a direct estimate of flood probabilities. This approach bypasses the uncertain precipitation, since the monsoon variance is derived from large-scale wind fields which are better represented by climate models. The simplicity of the monsoon-flood link allows deriving large ensembles of flood projections under climate change. We conclude that this is a worthwhile, complementary approach to the typical model chains in catchments where a substantial link between climate and floods is found. Y1 - 2014 U6 - https://doi.org/10.5194/nhess-14-1579-2014 SN - 1561-8633 VL - 14 IS - 6 SP - 1579 EP - 1589 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Merz, Bruno A1 - Aerts, Jeroen C. J. H. A1 - Arnbjerg-Nielsen, Karsten A1 - Baldi, M. A1 - Becker, Andrew C. A1 - Bichet, A. A1 - Bloeschl, G. A1 - Bouwer, Laurens M. A1 - Brauer, Achim A1 - Cioffi, F. A1 - Delgado, Jose Miguel Martins A1 - Gocht, M. A1 - Guzzetti, F. A1 - Harrigan, S. A1 - Hirschboeck, K. A1 - Kilsby, C. A1 - Kron, W. A1 - Kwon, H. -H. A1 - Lall, U. A1 - Merz, R. A1 - Nissen, K. A1 - Salvatti, P. A1 - Swierczynski, Tina A1 - Ulbrich, U. A1 - Viglione, A. A1 - Ward, P. J. A1 - Weiler, M. A1 - Wilhelm, B. A1 - Nied, Manuela T1 - Floods and climate: emerging perspectives for flood risk assessment and management JF - Natural hazards and earth system sciences N2 - Flood estimation and flood management have traditionally been the domain of hydrologists, water resources engineers and statisticians, and disciplinary approaches abound. Dominant views have been shaped; one example is the catchment perspective: floods are formed and influenced by the interaction of local, catchment-specific characteristics, such as meteorology, topography and geology. These traditional views have been beneficial, but they have a narrow framing. In this paper we contrast traditional views with broader perspectives that are emerging from an improved understanding of the climatic context of floods. We come to the following conclusions: (1) extending the traditional system boundaries (local catchment, recent decades, hydrological/hydraulic processes) opens up exciting possibilities for better understanding and improved tools for flood risk assessment and management. (2) Statistical approaches in flood estimation need to be complemented by the search for the causal mechanisms and dominant processes in the atmosphere, catchment and river system that leave their fingerprints on flood characteristics. (3) Natural climate variability leads to time-varying flood characteristics, and this variation may be partially quantifiable and predictable, with the perspective of dynamic, climate-informed flood risk management. (4) Efforts are needed to fully account for factors that contribute to changes in all three risk components (hazard, exposure, vulnerability) and to better understand the interactions between society and floods. (5) Given the global scale and societal importance, we call for the organization of an international multidisciplinary collaboration and data-sharing initiative to further understand the links between climate and flooding and to advance flood research. Y1 - 2014 U6 - https://doi.org/10.5194/nhess-14-1921-2014 SN - 1561-8633 VL - 14 IS - 7 SP - 1921 EP - 1942 PB - Copernicus CY - Göttingen ER - TY - JOUR A1 - Nguyen Nghia Hung, A1 - Delgado, José Miguel Martins A1 - Guentner, Andreas A1 - Merz, Bruno A1 - Bardossy, Andras A1 - Apel, Heiko T1 - Sedimentation in the floodplains of the Mekong Delta, Vietnam Part II: deposition and erosion JF - Hydrological processes N2 - Deposition and erosion play a key role in the determination of the sediment budget of a river basin, as well as for floodplain sedimentation. Floodplain sedimentation, in turn, is a relevant factor for the design of flood protection measures, productivity of agro-ecosystems, and for ecological rehabilitation plans. In the Mekong Delta, erosion and deposition are important factors for geomorphological processes like the compensation of deltaic subsidence as well as for agricultural productivity. Floodplain deposition is also counteracting the increasing climate change induced hazard by sea level rise in the delta. Despite this importance, a sediment database of the Mekong Delta is lacking, and the knowledge about erosion and deposition processes is limited. In the Vietnamese part of the Delta, the annually flooded natural floodplains have been replaced by a dense system of channels, dikes, paddy fields, and aquaculture ponds, resulting in floodplain compartments protected by ring dikes. The agricultural productivity depends on the sediment and associated nutrient input to the floodplains by the annual floods. However, no quantitative information regarding their sediment trapping efficiency has been reported yet. The present study investigates deposition and erosion based on intensive field measurements in three consecutive years (2008, 2009, and 2010). Optical backscatter sensors are used in combination with sediment traps for interpreting deposition and erosion processes in different locations. In our study area, the mean calculated deposition rate is 6.86kg/m(2) (approximate to 6mm/year). The key parameters for calculating erosion and deposition are estimated, i.e. the critical bed shear stress for deposition and erosion and the surface constant erosion rate. The bulk of the floodplain sediment deposition is found to occur during the initial stage of floodplain inundation. This finding has direct implications on the operation of sluice gates in order to optimize sediment input and distribution in the floodplains. KW - Mekong delta KW - sediment dynamics KW - deposition KW - erosion KW - floodplain sedimentation Y1 - 2014 U6 - https://doi.org/10.1002/hyp.9855 SN - 0885-6087 SN - 1099-1085 VL - 28 IS - 7 SP - 3145 EP - 3160 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Nguyen Nghia Hung, A1 - Delgado, José Miguel Martins A1 - Güntner, Andreas A1 - Merz, Bruno A1 - Bardossy, Andras A1 - Apel, Heiko T1 - Sedimentation in the floodplains of the Mekong Delta, Vietnam. Part I: suspended sediment dynamics JF - Hydrological processes N2 - Suspended sediment is the primary source for a sustainable agro-ecosystem in the Mekong Delta by providing nutrient input for the subsequent cropping season. In addition, the suspended sediment concentration (SSC) plays an important role in the erosion and deposition processes in the Delta; that is, it influences the morphologic development and may counteract the deltaic subsidence and sea level rise. Despite this importance, little is known about the dynamics of suspended sediment in the floodplains of the Mekong Delta. In particular, quantitative analyses are lacking mainly because of data scarcity with respect to the inundation processes in the floodplains. In 2008, therefore, a comprehensive in situ system to monitor the dynamics of suspended sediment in a study area located in the Plain of Reeds was established, aiming at the characterization and quantification of suspended sediment dynamics in the deeply inundated parts of the Vietnamese part of the Mekong Delta. The monitoring system was equipped with seven water quality-monitoring stations. They have a robust design and autonomous power supply suitable for operation on inundated floodplains, enabling the collection of reliable data over a long period of time with a high temporal resolution. The data analysis shows that the general seasonal dynamics of suspended sediment transport in the Delta is controlled by two main mechanisms: the flood wave of the Mekong River and the tidal backwater influences from the coast. In the channel network, SSC decreases exponentially with distance from the Mekong River. The anthropogenic influence on SSC could also be identified for two periods: at the start of the floodplain inundation and at the end of the flood period, when subsequent paddy rice crops are prepared. Based on the results, we recommend an operation scheme for the sluice gates, which intends to distribute the sediment and thus the nutrients equally over the floodplain. KW - Mekong Delta KW - floodplain KW - suspended sediment KW - sediment dynamics KW - floodplain sedimentation Y1 - 2014 U6 - https://doi.org/10.1002/hyp.9856 SN - 0885-6087 SN - 1099-1085 VL - 28 IS - 7 SP - 3132 EP - 3144 PB - Wiley-Blackwell CY - Hoboken ER - TY - JOUR A1 - Schroeter, Kai A1 - Kreibich, Heidi A1 - Vogel, Kristin A1 - Riggelsen, Carsten A1 - Scherbaum, Frank A1 - Merz, Bruno T1 - How useful are complex flood damage models? JF - Water resources research N2 - We investigate the usefulness of complex flood damage models for predicting relative damage to residential buildings in a spatial and temporal transfer context. We apply eight different flood damage models to predict relative building damage for five historic flood events in two different regions of Germany. Model complexity is measured in terms of the number of explanatory variables which varies from 1 variable up to 10 variables which are singled out from 28 candidate variables. Model validation is based on empirical damage data, whereas observation uncertainty is taken into consideration. The comparison of model predictive performance shows that additional explanatory variables besides the water depth improve the predictive capability in a spatial and temporal transfer context, i.e., when the models are transferred to different regions and different flood events. Concerning the trade-off between predictive capability and reliability the model structure seem more important than the number of explanatory variables. Among the models considered, the reliability of Bayesian network-based predictions in space-time transfer is larger than for the remaining models, and the uncertainties associated with damage predictions are reflected more completely. KW - floods KW - damage KW - model validation KW - Bayesian networks KW - regression tree Y1 - 2014 U6 - https://doi.org/10.1002/2013WR014396 SN - 0043-1397 SN - 1944-7973 VL - 50 IS - 4 SP - 3378 EP - 3395 PB - American Geophysical Union CY - Washington ER - TY - JOUR A1 - Uhlemann, Steffi A1 - Thieken, Annegret A1 - Merz, Bruno T1 - A quality assessment framework for natural hazard event documentation: application to trans-basin flood reports in Germany JF - Natural hazards and earth system sciences Y1 - 2014 U6 - https://doi.org/10.5194/nhess-14-189-2014 SN - 1561-8633 VL - 14 IS - 2 SP - 189 EP - 208 PB - Copernicus CY - Göttingen ER -