Application of an improved version of the erosion potential method in alpine areas

the assessment of erosive processes is of great importance in environmental engineering, resource management and land planning. in this paper the empirical approach known as erosion Potential Method (EPM) was improved to simplify the identifi- cation of the involved parameters. in addition, EPM suitability for alpine watersheds, where the average yearly temperature may be below 0°C, was discussed. the advantages of distributed ap- proaches rather than lumped methodologies were tested. EPM was then implemented in a distributed form for a set of 31 catch- ments located in alta valtellina (northern italy) in order to cap- ture the spatial variability of the parameters and the intensity of the erosion processes. the results obtained for these catchments were positively compared to long-term sedimentation data from three reservoirs and from a turbidimetric station

Improving sustainability of sediment management in Alpine reservoirs: control of sediment flushing operations to mitigate downstream environmental impacts.

This thesis focuses on the desiltation of Alpine reservoirs in order to sustain their long-term utilization and restore the functioning of the bottom outlets, minimizing at the same time downstream environmental impacts of sediment removal operations. Different case studies of controlled sediment flushing operations (CSFs) are analysed adopting a multidisciplinary approach. In particular, sediment transport and downstream riverbed alteration, ecological impacts on benthic macroinvertebrates and fish, and performance indicators were investigated. Moreover, the experimental dataset acquired before, during, and after a sediment removal operation was used to carry out and calibrate a one-dimensional sediment transport model of the monitored event. The duration of the CSFs and the average suspended sediment concentration in the outflowing water were constrained, with the specific environmental objective of limiting the downstream fish mortality as predicted by a simple dose/response model. The biomonitoring indicated that this model allowed for a first approximation estimate of the impacts on trout. On the other hand, similar scenarios of sediment removal in terms of duration and average SSC can be identified with analogous predicted impacts on fish but non-negligible differences in flushing efficiency. Therefore, site-specific investigation of environmental impacts may be the key aspect for upgrading the trade-off between economic and environmental needs in planning further operations in the same area

A review of applied methods in Europe for flood-frequency analysis in a changing environment

The report presents a review of methods used in Europe for trend analysis, climate change projections and non-stationary analysis of extreme precipitation and flood frequency. In addition, main findings of the analyses are presented, including a comparison of trend analysis results and climate change projections. Existing guidelines in Europe on design flood and design rainfall estimation that incorporate climate change are reviewed. The report concludes with a discussion of research needs on non-stationary frequency analysis for considering the effects of climate change and inclusion in design guidelines. Trend analyses are reported for 21 countries in Europe with results for extreme precipitation, extreme streamflow or both. A large number of national and regional trend studies have been carried out. Most studies are based on statistical methods applied to individual time series of extreme precipitation or extreme streamflow using the non-parametric Mann-Kendall trend test or regression analysis. Some studies have been reported that use field significance or regional consistency tests to analyse trends over larger areas. Some of the studies also include analysis of trend attribution. The studies reviewed indicate that there is some evidence of a general increase in extreme precipitation, whereas there are no clear indications of significant increasing trends at regional or national level of extreme streamflow. For some smaller regions increases in extreme streamflow are reported. Several studies from regions dominated by snowmelt-induced peak flows report decreases in extreme streamflow and earlier spring snowmelt peak flows. Climate change projections have been reported for 14 countries in Europe with results for extreme precipitation, extreme streamflow or both. The review shows various approaches for producing climate projections of extreme precipitation and flood frequency based on alternative climate forcing scenarios, climate projections from available global and regional climate models, methods for statistical downscaling and bias correction, and alternative hydrological models. A large number of the reported studies are based on an ensemble modelling approach that use several climate forcing scenarios and climate model projections in order to address the uncertainty on the projections of extreme precipitation and flood frequency. Some studies also include alternative statistical downscaling and bias correction methods and hydrological modelling approaches. Most studies reviewed indicate an increase in extreme precipitation under a future climate, which is consistent with the observed trend of extreme precipitation. Hydrological projections of peak flows and flood frequency show both positive and negative changes. Large increases in peak flows are reported for some catchments with rainfall-dominated peak flows, whereas a general decrease in flood magnitude and earlier spring floods are reported for catchments with snowmelt-dominated peak flows. The latter is consistent with the observed trends. The review of existing guidelines in Europe on design floods and design rainfalls shows that only few countries explicitly address climate change. These design guidelines are based on climate change adjustment factors to be applied to current design estimates and may depend on design return period and projection horizon. The review indicates a gap between the need for considering climate change impacts in design and actual published guidelines that incorporate climate change in extreme precipitation and flood frequency. Most of the studies reported are based on frequency analysis assuming stationary conditions in a certain time window (typically 30 years) representing current and future climate. There is a need for developing more consistent non-stationary frequency analysis methods that can account for the transient nature of a changing climate

Sustainable management of hydraulic diversions in fluvial ecosystem.

This thesis focuses on the study of the negative effects induced on stream ecosystems by hydropower schemes in an Alpine river system. The downstream ecological consequences of 4 controlled free-flow flushing operations designed to remove sediments accumulated in an Alpine reservoir are described. Sediment removals were carried out for analogous duration and in the same period of the year from 2006 to 2009. Brown trout populations were remarkably reduced after the beginning of flushing operations, but appeared to reach equilibrium with the new environmental conditions. Macroinvertebrate fauna, despite exhibiting a significant reduction in abundance and biomass following each flushing, showed a quick recovery within 3 months. Nevertheless, the yearly occurrence of sediment flushing changed the taxa composition, allowing species with fast life cycle and good colonizing ability to become dominant. Particle size analysis of core samples collected in riffle habitats provide evidence of a significant increase in interstitial fine sediment, that could adversely affect the recovery processes. Maximum allowable SSCs of 10 g L-1(daily average) and 5 g L-1(overall average) for flushing operations carried out in small to medium high-gradient Alpine streams are recommend. In the same river network, a data set (n=30) of free-flowing and altered flow streams was used to detect the effects of water diversion on macroinvertebrate communities using single and multimetric indices as well multivariate approaches. Although macroinvertebrate diversity decreased significantly in response to reduced flows, the results suggest that invertebrate-based metrics may be poor descriptors of the magnitude of flow reduction. A consistent pattern in the dataset was demonstrated through multivariate analysis by groups of taxa that were respectively reduced or increased in abundance at the impaired sites, confirming that diversions are potentially responsible for a change in macroinvertebrate composition. The findings of this research showed how both activities have the potential to alter biological communities, but even that could be managed together to minimize risks. Considering obtained results this project will help support current and future research of Alpine stream ecosystems and will provide information for a management of freshwater resource balancing economical, technical and environmental issues

Early Flash Flood Warning: A Feasibility Study with a Distributed Hydrological Model and Threshold Exceedance

In Mediterranean Europe, flash flooding is one of the most devastating hazards in terms of loss of human life and infrastructures. Over the last two decades, flash floods have caused damage costing a billion Euros in France alone. One of the problems of flash floods is that warning times are very short, leaving typically only a few hours for civil protection services to act. This study investigates if operationally available short-range numerical weather forecasts together with a rainfall-runoff model can be used for early indication of the occurrence of flash floods. One of the challenges in flash flood forecasting is that the watersheds are typically small, and good observational networks of both rainfall and discharge are rare. Therefore, hydrological models are difficult to calibrate and the simulated river discharges cannot always be compared with ground measurements. The lack of observations in most flash flood prone basins, therefore, necessitates the development of a method where the excess of the simulated discharge above a critical threshold can provide the forecaster with an indication of potential flood hazard in the area, with lead times of the order of weather forecasts. This report is focused on four case studies in Mediterranean part of Europe: i) The September 2002-flash flood event in the Cévennes-Vivarais region in the Southeast of the Massif Central in France, a region known for devastating flash flood; ii) the August 2003-flash flood event in both Fella subcatchment of Tagliamento watershed and upstream part of Isonzo river basin, iii) the October 2006-flash flood event in Isonzo river basin and iv) the September 2007-flash flood event in Upper Sava river basin in Slovenia. The French case study is described in more detail with the principles and methodologies being explained that are then applied to the remaining three case studies. Also, there were more data available for the 1st case study. The critical aspects of using numerical weather forecasting for flash flood forecasting are being described together with the threshold ¿ exceedance approach previously postulated for the European Flood Alert System (EFAS). The short-range weather forecasts, from the Local model of the German national weather service, are driving the LISFLOOD model, a hybrid between conceptual and physically based rainfall-runoff model. Results of the study indicate that high resolution operational weather forecasting combined with a rainfall-runoff model could be useful to determine flash floods more than 24 hours in advance.JRC.H.7-Land management and natural hazard

Evaluation of empirical approaches to estimate the variability of erosive inputs in river catchments

Die Dissertation erforscht die Unsicherheit, Sensitivität und Grenzen großskaliger Erosionsmodelle. Die Modellierung basiert auf der allgemeinen Bodenabtragsgleichung (ABAG), Sedimenteintragsverhältnissen (SDR) und europäischen Daten. Für mehrere Regionen Europas wird die Bedeutung der Unsicherheit topographischer Modellparameter, ABAG-Faktoren und kritischer Schwebstofffrachten für die Anwendbarkeit empirischer Modelle zur Beschreibung von Sedimentfrachten und SDR von Flusseinzugsgebieten untersucht. Der Vergleich alternativer Modellparameter sowie Kalibrierungs- und Validierungsdaten zeigt, dass schon grundlegende Modellentscheidungen mit großen Unsicherheiten behaftet sind. Zur Vermeidung falscher Modellvorhersagen sind kalibrierte Modelle genau zu dokumentieren. Auch wenn die geschickte Wahl nicht-topographischer Algorithmen die Modellgüte regionaler Anwendungen verbessern kann, so gibt es nicht die generell beste Lösung. Die Ergebnisse zeigen auch, dass SDR-Modelle stets mit Sedimentfrachten und SDR kalibriert und evaluiert werden sollten. Mit diesem Ansatz werden eine neue europäische Bodenabtragskarte und ein verbessertes SDR-Modell für Einzugsgebiete nördlich der Alpen und in Südosteuropa abgeleitet. In anderen Regionen Europas ist das SDR-Modell bedingt nutzbar. Die Studien zur jährlichen Variabilität der Bodenerosion zeigen, dass jahreszeitlich gewichtete Niederschlagsdaten geeigneter als ungewichtete sind. Trotz zufriedenstellender Modellergebnisse überwinden weder sorgfältige Algorithmenwahl noch Modellverbesserungen die Grenzen europaweiter SDR-Modelle. Diese bestehen aus der Diskrepanz zwischen modellierten Bodenabtrags- und maßgeblich zur beobachteten bzw. kritischen Sedimentfracht beitragenden Prozessen sowie der außergewöhnlich hohen Sedimentmobilisierung durch Hochwässer. Die Integration von nicht von der ABAG beschriebenen Prozessen und von Starkregentagen sowie die Disaggregation kritischer Frachten sollte daher weiter erforscht werden.This dissertation thesis addresses the uncertainty, sensitivity and limitations of large-scale erosion models. The modelling framework consists of the universal soil loss equation (USLE), sediment delivery ratios (SDR) and European data. For several European regions, the relevance of the uncertainty in topographic model parameters, USLE factors and critical yields of suspended solids for the applicability of empirical models to predict sediment yields and SDR of river catchments is systematically evaluated. The comparison of alternative model parameters as well as calibration and validation data shows that even basic modelling decisions are associated with great uncertainties. Consequently, calibrated models have to be well-documented to avoid misapplication. Although careful choices of non-topographic algorithms can also be helpful to improve the model quality in regional applications, there is no definitive universal solution. The results also show that SDR models should always be calibrated and evaluated against sediment yields and SDR. With this approach, a new European soil loss map and an improved SDR model for river catchments north of the Alps and in Southeast Europe are derived. For other parts of Europe, the SDR model is of limited use. The studies on the annual variability of soil erosion reveal that seasonally weighted rainfall data is more appropriate than unweighted data. Despite satisfactory model results, neither the careful algorithm choice nor model improvements overcome the limitations of pan-European SDR models. These limitations are related to the mismatch of modelled soil loss processes and the relevant processes contributing to the observed or critical sediment load as well as the extraordinary sediment mobilisation during floods. Therefore, further research on integrating non-USLE processes and heavy-rainfall data as well as on disaggregating critical yields is needed

Improving sustainability of sediment management in Alpine reservoirs: control of sediment flushing operations to mitigate downstream environmental impacts.

This thesis focuses on the desiltation of Alpine reservoirs in order to sustain their long-term utilization and restore the functioning of the bottom outlets, minimizing at the same time downstream environmental impacts of sediment removal operations. Different case studies of controlled sediment flushing operations (CSFs) are analysed adopting a multidisciplinary approach. In particular, sediment transport and downstream riverbed alteration, ecological impacts on benthic macroinvertebrates and fish, and performance indicators were investigated. Moreover, the experimental dataset acquired before, during, and after a sediment removal operation was used to carry out and calibrate a one-dimensional sediment transport model of the monitored event. The duration of the CSFs and the average suspended sediment concentration in the outflowing water were constrained, with the specific environmental objective of limiting the downstream fish mortality as predicted by a simple dose/response model. The biomonitoring indicated that this model allowed for a first approximation estimate of the impacts on trout. On the other hand, similar scenarios of sediment removal in terms of duration and average SSC can be identified with analogous predicted impacts on fish but non-negligible differences in flushing efficiency. Therefore, site-specific investigation of environmental impacts may be the key aspect for upgrading the trade-off between economic and environmental needs in planning further operations in the same area

Europe's ecological backbone: recognising the true value of our mountains

Europe's mountain areas have social, economic and environmental capital of significance for the entire continent. This importance has been recognised since the late 19th century through national legislation; since the 1970s through regional structures for cooperation; and since the 1990s through regional legal instruments for the Alps and Carpathians. The European Union (EU) first recognised the specific characteristics of mountain areas in 1975 through the designation of Less Favoured Areas (LFAs). During the last decade, EU cohesion policy and the Treaty of Lisbon have both focused specifically on mountain