Field data are used to study the size distribution of bedload in paved gravel-bed streams. Similarity analysis yields the results that all grain size ranges are of approximately equal transportability when the critical condition for breaking the pavement is exceeded. This result is only approximately correct due to deviations from similarity. However, it is adequate to justify development of a method for calculating total bedload, which requires only the subpavement median grain size rather than the size distribution. A method for calculating bedload size distribution that accounts for deviation from similarity is also developed.

Closure of "Bedload and Size Distribution in Paved Gravel-Bed Streams"

Water-energy-ecosystem nexus: Balancing competing interests at a run-of-river hydropower plant coupling a hydrologic–ecohydraulic approach

https://aslopubs.onlinelibrary.wiley.com/doi/pdf/10.4319/lo.1998.43.5.1020

Methods on stream ecology

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Mechanics Of Sediment Transport

Torbjørn Forseth*, Bjørn T. Barlaup, Bengt Finstad, Peder Fiske, Harald Gjøsæter, Morten Falkegård, Atle Hindar, Tor Atle Mo, Audun H. Rikardsen, Eva B. Thorstad, Leif Asbjørn Vøllestad, and Vidar Wennevik Norwegian Institute for Nature Research, P.O. Box 5685 Sluppen, Trondheim N-7485, Norway Uni Research Environment, P.O. Box 7810, Bergen N-5020, Norway Institute of Marine Research, P.O. Box 1870 Nordnes, Bergen N-5817, Norway Norwegian Institute for Water Research, Gaustadalléen 21, Oslo N-0349, Norway Norwegian Veterinary Institute, P.O. Box 750 Sentrum, Oslo N-0106, Norway UiT The Arctic University of Norway, Tromsø N-9037, Norway Department of Biosciences, University of Oslo, Centre for Ecological and Evolutionary Synthesis, P.O. Box 1066, Blindern, Oslo N-0316, Norway *Corresponding author: tel: þ47 926 43437; e-mail: torbjorn.forseth@nina.no.

/pdf/the-major-threats-to-atlantic-salmon-in-norway-piamej4erv.pdf

The major threats to Atlantic salmon in Norway

Extreme, short-duration fluctuations caused by storage hydropower plant discharges or ‘hydropeaking’ occur when hydropower is used to cover the peak electrical loading conditions of a power network. The overall effects of hydropeaking can result in serious disturbances to the hydrologic regime, river morphology and the ecological condition of a river. In this study a transient, fuzzy logic based two-dimensional fish habitat model was used to investigate the stranding risk to juvenile European grayling (Thymallus thymallus) corresponding to different river morphologies. The stranding risk was simulated using two 24 hour discharge hydrographs in two alpine gravel bed river reaches. Both reaches were in close proximity to the hydropower plant outlet and were chosen due to their starkly contrasting morphological features. Spatially distributed stranding risk was determined based on a multi-step procedure which took into account the stationary habitat suitability, critical dewatering rates and flow depths. Although the number of reaches used in the investigation was limited in scope, clear distinctions with respect to the stranding risk were found. The reach with wider, flatter cross sections had a larger amount of stranding risk areas as compared to the reach with a steeply incised channel form. Stranding risk was found to be related to a specific set of changes in the discharge than to a particular rate of change or magnitude of the flow fluctuations. The temporal distribution of stranding risk was found to be almost identical for both reaches.

Estimating Stranding Risk due to Hydropeaking for Juvenile European Grayling Considering River Morphology

The Habitat Modelling System CASiMiR: A Multivariate Fuzzy Approach and its Applications

The complexity and dynamic nature of ecosystem processes impose high requirements on the approaches, methods and modelling techniques applied to support ecological assessments of rivers. Particularly the interactions of abiotic and biotic variables, the high spatial and temporal variability of parameters and processes and the interdisciplinary research field present a special challenge on the development of appropriate tools. Given the naturally dynamic creation, destruction and maintenance of habitat templates in rivers (habitat dynamics) the habitat can be regarded as a basic element of fluvial ecosystems. Accordingly, high demands are placed on aquatic habitat modelling techniques emphasizing the need for the improvement and further development of existing approaches.
The present study predominantly addresses three research fields encompassing the hydromorphology, the fluvial ecology and the hyporheic interstitial of rivers. All disciplines are involved by interacting processes defining the quality of reproduction habitats for gravel-spawning fish. This work is focused on implementing the hydromorphological and hyporheic variability in physical habitat modelling considering all variables that describe the habitat in their spatial and temporal variability to allow a dynamic representation of habitat suitability. The reproduction period of gravel-spawning fish works as an excellent indicator for interstitial habitats, as the life-stages during reproduction are characterised by high requirements on the habitat. Based on the abiotic description of the environment a multi-step habitat modelling framework is developed that addresses each life-stage during the reproduction by an appropriate selection of key habitat variables that are linked via a multivariate fuzzy-logic model to simulate habitat suitability indices of each life stage during the reproduction period. The last step of the modelling framework includes the aggregation of the dynamic habitat values to a temporally integrated parameter and the final result of the modelling framework, the reproduction habitat suitability.
The proposed multi-step habitat modelling framework is applied in a mountainous river reach downstream of a dam and produced reliable results. The simulated habitat suitability indices for each life-stage during reproduction allow for a representation of physical habitats in the form of spatial distribution maps for different time-steps, time-series for different locations and an integrated habitat supply over the entire reproduction period. This provides highly valuable information about habitat dynamics as all spatially and temporally varying input variables are considered in the multi-step habitat modelling framework. Consequently a direct identification of occurring bottlenecks during the reproduction of brown trout is feasible and can be referred back to responsible habitat variables. In the case study it is found that the spawning and emergence stages are not limiting the reproduction success and the most restricting conditions occurred during hatching. These limitations are predominantly caused by critical temperatures during the winter season and critical permeability conditions due to sediment infiltration processes during the regulated flow period. The aggregated reproduction habitat suitability contains the summarized effects of all varying abiotic conditions during the reproduction period of gravel-spawning fish and allows for a quick identification of the availability and quality of reproductive habitats.
Although the obtained results provide valuable results it is worth noting that models in general are never able to fully reflect the dynamic behaviour of rivers and its ecological relations given their numerous and complex interactions. The simplification of the physical and ecological processes requires a well-founded verification of obtained simulation results against field observations and reference sites. The highest benefit of the proposed modelling framework comprises the spatial and temporal consideration of conventional and new habitat variables resulting in a detailed representation of habitat dynamic processes occurring in river reaches. Further, the presented work is the first attempt to simulate the quality of reproduction habitats for gravel-spawning fish using physical habitat modelling. Possible future applications predominantly include the support of ecological impact assessments but also the applicability as an instrument supporting the management and planning processes of restoration measures (e.g. for re-establishing reproducing fish population in rivers) as the simulation of reproduction habitats presents one fundamental process for the development of stable fish populations. 
Die Komplexitat und Dynamik fluvialer okologischer Prozesse stellt auserst hohe Anforderungen an die Entwicklung von Methoden und Modellen zur Unterstutzung in okologischen Bewertungen von Fliesgewassern. Insbesondere die Interaktion zwischen abiotischen und biotischen Komponenten, die hohe raumliche und zeitliche Variabilitat sowie die Interdisziplinaritat der beteiligten Prozesse erschweren die Entwicklung geeigneter Modellierungs- und Prognosewerkzeuge. Die regelmasige Erzeugung, Zerstorung und Erhaltung von charakteristischen Habitatmustern (Habitatdynamik) sind grundlegende Prozesse fluvialer Okosysteme, die mit aktuell verfugbaren Habitatmodellen schwierig abzubilden sind und die Notwendigkeit der Weiterentwicklung von existierenden Ansatzen der Habitatmodellierung verdeutlichen. 
Die vorliegende Arbeit befasst sich mit Prozessen aus der Hydromorphologie, der Fliesge-wasserokologie und des hyporheischen Interstitials, die interaktiv die Habitatqualitat wahrend der Reproduktion von kieslaichenden Fischarten bestimmen. Die Motivation dieser Arbeit resultiert aus der wachsenden Anforderung dynamische Prozesse, wie die hydromorphologische und hyporheische Variabilitat in die physikalische Habitatmodellierung von Fischen zu implementieren um somit die Simulation von dynamisch veranderlichen Habitateignungen zu ermoglichen. Der Fokus richtet sich hierbei auf morphodynamische Prozesse, wie Kornsortierungen (longitudinal, horizontal und vertikal), Infiltration von Feinsedimenten in das Korngerust der Gewassersohle und Sohlumlagerungen, die einerseits notwendig sind um geeignete Habitate zu erzeugen aber andererseits auch limitierend wirken konnen. Um den Habitatanspruchen wahrend der Reproduktion durch Modellierung gerecht zu werden besteht weiterhin der Bedarf an der Entwicklung eines geeigneten Indikators zur Beschreibung der hyporheischen Variabilitat. Dieser soll dazu dienen den interstitialen Lebensraum wahrend den Entwicklungsstadien des Inkubationszeitraums (Augenpunktstadium, Schlupfzeit und larvale Phase) entsprechend zu bewerten. Das primare Ziel ist daher die Entwicklung eines Modellsystems, basierend auf dem Prinzip der physikalischen Habitatbeschreibung um die raumlich und zeitlich variierenden Habitateignungen der einzelnen Entwicklungsstadien wahrend der Reproduktionsphase von kieslaichenden Fischarten zu simulieren und zu einem aggregierenden Gesamtergebnis - der Reproduktionshabitateignung - zusammenzufuhren. 
Das Modellsystem wird in einer typischen Gebirgsstrecke unterhalb einer Staumauer angewendet. Die Berucksichtigung von raumlich und zeitlich variierenden Habitatvariablen erlauben die simulierten Habitateignungen der einzelnen Entwicklungsstadien wahrend der Reproduktion kieslaichender Fische in Form von Habitateignungskarten zu verschiedenen Zeitpunkten, Habitateignungsganglinien an verschiedenen Orten und als integrierendes Habitatangebot darzustellen und auszuwerten. Damit wird einerseits die Habitatdynamik beschrieben und andererseits bieten die Auswertungen die Moglichkeit limitierende abiotische Randbedingungen sowohl zeitlich als auch raumlich zuzuordnen. Einschrankend ist jedoch festzuhalten, dass insbesondere der hyporheische Austausch in Zukunft verstarkt in der abiotischen Beschreibung der Habitate zu berucksichtigen ist und eine fundierte Uberprufung anhand biologischer Untersuchungen notwendig ist, um die Belastbarkeit der Ergebnisse zu erhohen. 
Obwohl die erzielten Ergebnisse eine hohe Bedeutung fur die Bewertung der Reproduktion kiesaichender Fischarten beinhalten, bleibt festzuhalten, dass Modelle nie die gesamte fluviale Dynamik und deren Interaktion mit okologischen Prozessen abbilden konnen. Die Vereinfachung physikalischer und okologischer erfordern eine ausfuhrliche und wohlbedachte Verifizierung der erhaltenen Simulationsergebnisse anhand von Naturdaten und Referenzbedingungen. Die Weiterentwicklung der physikalischen Habitatmodellierung im Rahmen dieser Arbeit besteht masgeblich aus der raumlich und zeitlich hochaufgelosten Verwendung von bestehenden und neuen Habitatvariablen. Diese erlauben eine detaillierte Abbildung der relevanten abiotischen Prozesse in Fliesgewassern in ihrem zeitlichen Verlauf und somit Aussagen uber die Habitatdynamik. Des Weiteren stellt das Modellsystem erstmals den Versuch dar, die Reproduktionshabitate von kieslaichenden Fischarten im Rahmen einer physikalischen Habitatmodellierung abzubilden. Aufgrund der beinhalteten Dynamik und der Prognosefahigkeit des Modellsystems bestehen Anwendungsmoglichkeiten vorwiegend im Rahmen von okologischen Untersuchungen und Bewertungen, aber auch in der Planung und dem Management wasserwirtschaftlicher und wasserbaulicher Masnahmen, die zum Beispiel auf eine Wiedereinfuhrung von reproduzierenden Fischpopulationen abzielen, da die Simulation von verfugbaren Reproduktionshabitaten eine fundamentale Grundlage fur die nachhaltige Entwicklung von stabilen gewassertypischen Fischpopulationen ist.

Modelling approach for interstitial sediment dynamics and reproduction of gravel-spawning fish

Rapid Flow Fluctuations and Impacts on Fish and the Aquatic Ecosystem

In contrast to non-cohesive sediments, the incipient motion of cohesive sediments is characterized by much more complex interactions between several sedimentary, biological, and chemical parameters. Thus, site-specific investigations are required to obtain information about the erosion stability of cohesive materials. This becomes even more relevant for contaminated sediments, stored in riverine sediments as a “burden of the past”, because of their remobilization potential during flood events. This article represents a twofold measuring strategy for the detection of erosion thresholds: an in situ device for determination of critical shear stresses in the field, and a laboratory approach where sediment cores are withdrawn and subsequently analyzed over depth. The combined measuring strategy was applied in the River Elbe and at selected sites of the catchment of the River Saale. The results show a great variety of erosion thresholds over depth, demonstrating the need to conduct vertical analyses, especially when addressing buried layers with contaminations. The latter is only possible in the laboratory but the in situ device revealed clear benefits in capturing the loose flocculent layer on top of the sediment that might be easily lost during sediment retrieval and transport. Consequently, it is ideal to combine both approaches for a comprehensive insight into sediment stability.

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Markus Noack

Papers

Estimating Stranding Risk due to Hydropeaking for Juvenile European Grayling Considering River Morphology

The Habitat Modelling System CASiMiR: A Multivariate Fuzzy Approach and its Applications

Modelling approach for interstitial sediment dynamics and reproduction of gravel-spawning fish

Rapid Flow Fluctuations and Impacts on Fish and the Aquatic Ecosystem

Combining Field and Laboratory Measurements to Determine the Erosion Risk of Cohesive Sediments Best