This paper investigates the relationship between expert judgement and numerical criteria when evaluating hydrological model performance by comparing simulated and observed hydrographs. Using a webbased survey, we collected the visual evaluations of 150 experts on a set of high-and low-flow hydrographs. We then compared these answers with results from 60 numerical criteria. Agreement between experts was found to be more frequent in absolute terms (when rating models) than in relative terms (when comparing models), and better for high flows than for low flows. When comparing the set of 150 expert judgements with numerical criteria, we found that most expert judgements were loosely correlated with a numerical criterion, and that the criterion that best reflects expert judgement varies from expert to expert. Overall, we identified two groups of 10 criteria yielding an equivalent match with the expertise of the 150 participants in low and high flows, respectively. A single criterion common to both groups (the Hydrograph Matching Algorithm with mean absolute error) may represent a good indicator for the overall evaluation of models based on hydrographs. We conclude that none of the numerical criteria examined here can fully replace expert judgement when rating hydrographs, and that both relative and absolute evaluations should be based on the judgement of multiple experts. Comparaison des avis d'experts et des critères numériques pour l'évaluation d'hydrogrammesRésumé Cet article examine la relation entre jugement expert et critères numériques lorsque l'on évalue les performances de modèles hydrologiques en comparant des hydrogrammes simulés et observés. Une enquête en ligne nous a permis de collecter 150 évaluations d'experts sur un échantillon d'hydrogrammes en hautes et basses eaux. Ces évaluations ont ensuite été comparées aux résultats obtenus à l'aide de 60 critères numériques. Les experts ont été plus fréquemment en accord en termes absolus (en notant les modèles) qu'en termes relatifs (en comparant les modèles), et sur les hautes eaux que sur les basses eaux. La comparaison des 150 jugements d'experts et des critères numériques montre que la plupart des experts sont faiblement corrélés à un critère numérique, et que le critère qui reflète le mieux le jugement expert varie d'un expert à l'autre. Globalement, nous avons identifié deux groupes de dix critères qui reflètent bien l'expertise des 150 participants en basses et hautes eaux respectivement. Un critère commun aux deux groupes (l'algorithme de correspondance des hydrogrammes basé sur l'erreur absolue moyenne) peut représenter un bon indicateur pour l'évaluation globale de modèles basée sur les hydrogrammes. On conclut qu'aucun des critères numériques examinés ne peut remplacer le jugement expert lorsque l'on note des hydrogrammes, et que des évaluations relatives ou absolues devraient être basées sur des expertises multiples.Mots clefs évaluation d'hydrogrammes ; modèle hydrologique ; jugement expert ; efficacité ; critère numérique ; enquête en ligne 402

Abstract. In light of climate change and growing numbers of people inhabiting riverine floodplains, worldwide demand for flood protection is increasing, typically through engineering approaches such as more and bigger levees. However, the well-documented “levee effect” of increased floodplain use following levee construction or enhancement often results in increased problems, especially when levees fail or are compromised by big flood events. Herein, we argue that there are also unintended socio-economic and ecological consequences of traditional engineering solutions that need to be better considered, communicated and weighed against alternative solutions. Socio-economic consequences include reduced aesthetic and recreational values as well as increased downstream flooding risk and reduced ecosystem services. Ecological consequences include hydraulic decoupling, loss of biodiversity and increased risk of contamination during flooding. In addition, beyond river losses of connectivity and natural riparian vegetation created by levees, changes in groundwater levels and increased greenhouse gas emissions are likely. Because flood protection requires huge financial investments and results in major and persistent changes to the landscape, more balanced decisions that involve all stakeholders and policymakers should be made in the future. This requires a transdisciplinary approach that considers alternative solutions such as green infrastructure and places emphasis on integrated flood management rather than on reliance on technical protection measures.

Abstract. The question of how catchments actually "function" has probably caused many sleepless nights as it is still an unsolved and challenging scientific question. Here, we approach this question from the similarity perspective. Instead of comparing single physiographic features of individual catchments we explore the interplay of state and structure on different runoff formation processes, aiming to infer information on the underlying "functional" behaviour. Therefore, we treat catchments as lumped terrestrial filters and relate a set of different structure and storage descriptors to selected response measures. The key issue here is that we employ dimensionless quantities exclusively by normalizing the variable of interest by its limiting terrestrial or forcing characteristic. Specifically we distinguish extensive/additive and intensive/non-additive attributes through normalizing storage volumes by maximum storage capacities and normalizing fluxes (e.g. discharge) by permeability estimators. Moreover, we propose the normalized temporal derivative of runoff as a suitable measure to detect intensity-triggered (high frequency) runoff production. Our dimensionless signatures evidently detect functional similarity among different sites for baseflow production, storm runoff production and the seasonal water balance. Particularly in the latter case we show that normalized double and triple mass curves expose a typical shape with a regime shift that is clearly controlled by the onset and the end of the vegetation period which we can adequately characterize by a simple temperature index model. In line with this, temperature explained 70 % of the variability of the seasonal summer runoff coefficients in 22 catchments distributed along a strong physiographic and climatic gradient in the German part of the Danube basin. The proposed non-additive response measure detected signals of high frequency intensity controlled runoff generation processes in two alpine settings. The approach, in fact edge filtering, evidently works when using "low-pass" filtered hourly rainfall-runoff data of mesoscale catchments ranging from 12 to 170 km2. We conclude that vegetation exerts a first order control on summer stream flow generation when the onset and termination of summer are more significantly defined by temperature than simply by the actual Gregorian day. We also provide evidence that properties describing gradients (e.g. surface topography) and resistances (e.g. hydraulic conductivities) may be much more powerful in explaining runoff response behaviour when they are treated as groups compared to their individual use. Lastly, we show that storage estimators such as the proposed normalized versions of pre-event discharge and antecedent moisture can be valuable predictors for event runoff coefficients: For some of our test regions they explain up to 70 % of their variability.

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s u m m a r yRainfall simulations are a useful and important tool in studying infiltration, surface runoff generation, soil erosion and nutrient as well as agro-chemical transport from arable land. Such simulations are time-consuming and costly and hence are usually only carried out under a limited variation of settings necessary to answer specific research questions. Therefore, it is difficult to use rainfall simulation data for hypothesis testing in a more general sense or to parameterize hydrological or erosion models applicable under a wider range of environmental conditions. To overcome these restrictions and to set-up a broader basis for following up studies, we analyzed, harmonized and filled gaps of a large set of existing rainfall simulations carried out by five different research groups in Germany. This covered 726 rainfall simulations (24,384 runoff measurements) carried out on 209 plots under a wide range of conditions for which 4 rain properties, 5 plot properties, 20 soil properties, 5 land use properties and 2 runoff properties were compiled. These data were quality controlled and made available for public use (Seibert et al., 2011). The most important deficiencies were smoothed runoff measurements, missing time to ponding data, different soil descriptions including frequent gaps in stone content, inconsistent moisture measurements and sometimes rather rough measurements of surface cover. The calculation of the geometric mean particle diameter, time since tillage and the application of different site specific procedures supported harmonization and helped to overcome several of these deficiencies. A satisfying gap filling procedure was developed for time to ponding. The most important inconsistencies that could not be removed were different depths of moisture measurement. Hence, there is a need to define a set of basic variables that always should be measured and documented with defined standards to enable comparison between different studies, to assess the boundary conditions of validity and possibly to make wider use of individual data sets by combining several of them.