Isabella Schalko

Last Name

Schalko

First Name

Isabella

ORCID

0000-0002-4602-0758

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Publications 1 - 10 of 47

WoodFlow project - large wood management in rivers
Steeb, Nicolas; Badoux, Alexandre; Boes, Robert; et al. (2021)
14th congress INTERPRAEVENT 2021. Natural Hazards in a Changing World
This contribution summarises the most important practical findings from the WoodFlow research project. The main goal was to improve understanding of the processes governing large wood (LW) dynamics in watercourses and to provide practitioners with suitable tools to help assess LW-related hazards. The results provide a basis for estimating potential LW quantities, modelling wood transport during floods and describing the associated hazards due to wood accumulations. The resulting recommendations can be used by specialists as a basis for silvicultural and river-engineering measures.
Large Wood Accumulation Probability at a Single Bridge Pier
Schalko, Isabella (2017)
Proceedings of the 37th IAHR World Congress
Large wood management in rivers - a practice-oriented research project in Switzerland
Ruiz-Villanueva, Virginia; Badoux, Alexandre; Boes, Robert; et al. (2016)
13th Congress Interpraevent 2016 : living with natural risks : 30 May to 2 June 2016, Lucerne, Switzerland. Conference proceedings
Laboratory flume experiments on the formation of spanwise large wood accumulations Part I: Effect on backwater rise
Schalko, Isabella; Lageder, Carmen; Schmocker, Lukas; et al. (2019)
Water Resources Research
Fuzzy-logic indicators for riverbed de-clogging suggest ecological benefits of large wood
Schwindt, Sebastian; Negreiros, Beatriz; Ponce, Maria; et al. (2023)
Ecological Indicators
Rivers provide dynamic habitats with ecological niches, particularly in their mobile sand, gravel, and cobble riverbed patches that create an active hyporheic zone. Natural or artificial deposition of fine sediment may clog the porous matrix of the hyporheic zone, impairing exchange processes between the subsurface and surface water. Clogging reduces the permeability of the sediment matrix, thus degrading the ecological functionality of the hyporheic zone. Once clogged, the ecological functions may be recovered through active stream restoration, which requires considerate site assessment. To this end, clogging is typically assessed by expert opinion of substrate characteristics including grain size characteristics, porosity, hydraulic conductivity, and interstitial oxygen content. To overcome limitations of expert assessment, such as subjectivity expressed in noisy decision-making, this study introduces a novel fuzzy-logic method based on physically sound rules. The method provides quantitative indicators for clogging and declogging to evaluate the effectiveness of stream restoration. We applied the fuzzy-logic method to test whether the placement of large wood, a common restoration practice, can locally prevent or reduce clogging. Two measurement series from before and after a morphologically effective flood suggested that large wood placements perpendicular to the flow generate elevated amounts of declogging. The tested logs caused a greater amount of declogging within their region of influence than observed at a reference point. The effect was stronger for a log emergent at baseflow. The declogging assessment showed that the novel fuzzy-logic indicators can reasonably overcome subjective judgment by accounting for multi-variate quantitative changes rather than individual parameter trends.
Klein, aber mit grosser Wirkung: Wie Äste und Blätter den Rückstau einer Schwemmholzverklausung in Flüssen vergrössern
Schalko, Isabella; Schmocker, Lukas; Weitbrecht, Volker; et al. (2019)
Ingenieurbiologie
Risk reduction measures of large wood accumulations at bridges
Schalko, Isabella; Schmocker, Lukas; Weitbrecht, Volker; et al. (2020)
Environmental Fluid Mechanics
Quantification of large wood (LW) impact forces at field-scale using SmartWood
Spreitzer, Gabriel; Schalko, Isabella; Boes, Robert; et al. (2022)
Proceedings of the 39th IAHR World Congress
While wood in rivers constitutes an essential element for the regulation of stream power and habitat creation, large wood (LW) carried during floods poses a high risk for interactions with in-stream structures such as bridges, dams or weirs. Although significant damage or total failure of impacted structures is frequently reported, there are no field-scale data of LW impacts available to date. Thus, acceleration data from innovative inertial measurement units (IMUs), which are deployed in the course of the SmartWood_3D research project at the Laboratory of Hydraulics, Hydrology and Glaciology (VAW) of ETH Zurich, were used to measure field-scale impact forces of transported LW during floods. The field experiments considered the release of up to four sensor-tagged prototype logs – SmartWood – at a time into flooded channels (approximately HQ₁) in Switzerland. Each SmartWood-log is fully debranched and measures 4.40 m in length at a mean diameter of 0.33 m. During the preparation of SmartWood in the laboratory, wood density decreased from 680 kg/m³ for the freshly cut and wet logs directly from the forest to 450 kg/m³ for the completed SmartWood logs at dry condition. The wetted density of SmartWood during the field experiments was roughly 500 kg/m³, yielding an impacting mass of roughly 188 kg. After SmartWood had been released into the channel, the logs were instantly mobilised by the high flow. On their journey downwards, complex LW dynamics were observed and successfully measured with high temporal resolution for the first time to the authors’ knowledge. Of particular interest were interactions of SmartWood with channel boundaries and in-stream obstacles (e.g., boulders). Deceleration of impacting logs were found to be significant, reaching the maximum measurable acceleration range (± 16 g) of the applied smart-sensors. The gained results contribute to a better understanding of LW dynamics in rivers and will help engineers to assess the vulnerability of existing structures as well as to improve the design of future flood-resilient structures in fluvial environments.
Laboratory study on wood accumulation probability at bridge piers
Schalko, Isabella; Schmocker, Lukas; Weitbrecht, Volker; et al. (2020)
Journal of Hydraulic Research
Macro-Roughness Elements for River Restoration: Flow Structures
Speltoni, Simone; Schalko, Isabella; Weitbrecht, Volker; et al. (2023)
Proceedings of the 40th IAHR World Congress
River restoration projects aim at reintroducing habitats and ecological functions that might have been lost due to anthropogenic forcings, such as flood protection measures or hydropower plants. The effort to restore the ecological value of a river can imply different concepts, considering target species, ecological habitats, as well as available space. In cases where space is limited, macro-roughness elements can be built to create morphological and flow heterogeneity to provide fluvial habitats such as pools, riffles, and runs. Their placement in the river reach, as well as their shape and geometry affect local flow and morphological structures. Besides improved ecological conditions these measures may as well have an impact on flood protection issues. In this paper, we present a brief literature review about previous laboratory and field experiments on the physical behavior of wood placements as macro-roughness elements with respect to flow dynamics. To complement previous studies, field experiments will be conducted on the effect of engineered logjams, rootwads, and boulder sills on the local flow conditions. The methods and research questions of the planned experiments using largescale surface particle image velocimetry are herein summarized.

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Isabella Schalko

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