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Start date: 22.09.2025 Language of thesis: English, German Master's Project/Master's Thesis

The outcomes of this work are expected to contribute to a better understanding of best practices for sensor installation and provide recommendations for minimizing signal distortion in both laboratory and field studies. The findings may ultimately improve the reliability and comparability of pressure-based flow measurements in hydraulic research.

For further information please contact Janine Vögele (voegele@vaw.baug.ethz.ch)

Turbulence in the flow field influences fish behavior, swimming efficiency, foraging success, habitat selection, and population density. Elevated turbulence levels can increase the energetic costs of locomotion and, under extreme conditions, result in physical injury or mortality. Fish can also exploit energy from specific turbulence structures or turbulent eddies to enhance locomotion efficiency. In other cases, fish may avoid these turbulent eddies to avoid loss of balance and injury. These diverse behavioral responses can be artificially induced by generating turbulent eddies in the flow field using turbulence generators, structures, or elements. These elements obstruct the flow field and generate a controlled eddy structure moving downstream at defined inflow conditions. These eddies can have different intensities, periodicity, orientation, and sizes. **The FishPath Project** has investigated the behavioral responses of the fish to three distinctly oriented eddies, namely: horizontal, vertical eddies and streamwise eddies for two different eddy sizes and frequencies through live- fish tests in an ethohydraulic flume. Based on these fish-eddy interactions tests, three different novel structural/elements arrangements (Figure. 1) were designed using these elements in such a way that, when placed in a flow field, the fish are expected to avoid the turbulent eddies generated by these elements and swim towards alternative paths termed as “bypass” during their downstream migration. In real-world applications, these structures will guide the downstream migrating fish towards a safe path or bypass system, preventing turbines or spillway entry in water diversion structures or hydropower intakes. This novel structure is termed as _**E**ddies based behavioral fish **G**uidance **S**ystem (EGS)_. Live fish tests of this EGS-bypass system were performed at VAW ETH Zurich's ethohydraulic flume for different configuration using different fish species namely: Atlantic Salmon smolts, European eel, spirlin, barbel, roach, chub. Atlantic salmon tests showed excellent guidance efficiency of >95% for streamwise EGS and >75% for vertical prismatic EGS. The EGS was further tested at a larger ethohydraulic flume in Vattenfall, Sweden, and preliminary results indicates similar or even better guidance efficiency for Salmon smolts. The preliminary results demonstrate the feasibility of turbulent eddies as a behavioral guidance structure for downstream migrating fish, especially Salmon smolts. The real-world implementation of the EGS-bypass system requires a detailed knowledge of flow field and operational aspects such as probability of clogging due to floating debris and organic fine materials, headloss due to structures, and a change in downstream flow field, potentially affecting inflow conditions for water intake structures. Thus, detailed knowledge on flow field and operational aspects of EGS is required. This thesis will systematically investigate these aspects through laboratory flume experiments for different physical and hydraulic configurations of EGS. Start date: 22.09.2025 Language of thesis: English

The goal of this thesis is to investigate the following operational aspects of three different EGS namely: vertical prismatic EGS, streamwise EGS and transverse EGS: a) Systematic driftwood tests in laboratory flume to determine the influence of EGS configurations, driftwood log parameters and hydraulic conditions on clogging process, and analyse possible solutions to the problem. b) Velocity field measurements of inflow, around the EGS and bypass, using ADV to analyse the impact of different EGS configuration on the overall flow field c) Headloss computations for different EGS configurations using data from ultrasonic distance measurement devices The thesis will consist of 2-4 weeks of laboratory tests at VAW to collect the required data. A basic knowledge of turbulent flows and knowledge of Matlab/Python or another programming language is advantageous.

For further information please contact Kamal P. Pandey (pandey@vaw.baug.ethz.ch).

Im neuen Energiegesetz sind die Ziele für den Ausbau der Elektrizität aus Wasserkraft in der Schweiz angegeben. Mit der Berücksichtigung der Restwasserbestimmungen ist bis im Jahr 2050 ein Zubau von 4325 GWh/Jahr notwendig. Die Erreichung dieser Ziele soll auch zur Stärkung der Versorgungssicherheit im Winter beitragen. Jedoch beeinträchtigen Wasserkraftwerke häufig die in der Gewässerschutzverordnung geforderte naturnahe Gewässerdynamik und wirken sich in der Regel negativ auf die Lebensräume der Pflanzen und Tiere sowie auf die Landschaft aus. Der Ausbau der Wasserkraft muss somit nachhaltig erfolgen, damit die Erhaltung der Ökosysteme und der Biodiversität sichergestellt ist. Startdatum: 22.09.2025, Projektsprache: Deutsch oder Englisch

Ziel dieser Arbeit ist die Bestimmung von verbleibenden Linienpotenzialen an Gewässern im Rahmen von Schutz- und Nutzungsplanungen der Kantone gemäss einer neuen Empfehlung von Schweizerischen Bundesämtern (inkl. GIS-Anleitung). Eine übergeordnete Frage ist: Kann ein Ausbau helfen, die Ziele der Energiestrategie zu erreichen, unter Beachtung des Gewässerschutzes sowie des Arten-, Lebensraum- und Landschaftsschutzes? Dabei soll ein besonderes Augenmerk auf die Winterproduktion gelegt werden. Eine projektunabhängige Beurteilung auf hoher Flughöhe soll eine Fokussierung auf bisher nicht genutzte, aber tatsächlich geeignete Strecken und eine ökologisch vertretbare Beschleunigung des Ausbaus der Wasserkraft ermöglichen.

Für weitere Informationen bitte Gabor Süss kontaktieren (suess@vaw.baug.ethz.ch).

LSPIV allows to measure flow velocity fields using videos and tracers. In this work, videos are taken through a drone hovering over the MREs, while small bio-soluble tracers are thrown into the current to highlight velocity gradients. The analysis of videos through a well-established Matlab code allows to quantify the flow velocity and compare the hydraulic responses of different MREs under similar hydraulic regimes. Field experiments are planned to be carried out together with the help of colleagues from VAW. Start date: 22.09.2025. Project language: English.

The goal of this study is to characterize the flow velocity fields around different MREs. Field experiments were already performed in 2023-2024, providing results that can be used for reference. Target is to increase the current dataset by performing additional field experiments for the year 2025, and carrying out the data analysis to compare the actual results from previous years. Specifically, the student will use the current workflow (Matlab and Python) to analyze videos and images and provide more results about parameters (velocity gradients and classes, turbulent kinetic energy) that depend on the specific macro-roughness element and vary with the discharge. The scope is to inform river practitioners and scientists about similarities and differences among macro-roughness elements.

For further information please contact Simone Speltoni (speltoni@vaw.baug.ethz.ch).

Engineered logjams (ELJs) are widely used as macro-roughness elements, constructed in diverse designs and configurations. These structures vary in height, width, length, porosity, and placement, each influencing the local flow field by altering shear stress intensity, turbulence, and sediment dynamics. This leads to the formation of scours and deposits of different intensities around the ELJs. Additionally, even well-defined designs can generate different flow patterns when hydraulic conditions change (e.g., variations in discharge, or relative submergence). To address these complexities, a systematic investigation of the interactions between flow fields, mobile bed and ELJ designs is planned through physical experiments. Start date: 22.09.2025. Project language: English

The goal of this study is to characterize the flow field and the morphology development around porous structures like logjams. The experiments will be conducted under steady-state conditions and with a mobile bed. Different grain size distributions will be used, and scaled models of ELJ will be tested, with different porosity, width and location. Focus will be put on studying the resulting flow and turbulence structures (herein defined by water depth, flow velocity, turbulent kinetic energy, and eddy size), as well as local morphologies (scours and deposits) for the different setups. The water depth (h) will be varied with respect to the ELJ height (H) to investigate different submergence levels, and their implications on the local scour and deposit configuration. Multiple logjams might be tested together in the same run, to study the role of relative distance and location.

For further information please contact Simone Speltoni (speltoni@vaw.baug.ethz.ch).

Der Oberpinzgau zwischen Mittersill und Wald wurde in den letzten Jahrzehnten vermehrt durch Hochwasserereignisse betroffen, mit zum Teil verheerenden Schäden an Gebäuden und Infrastrukturanlagen. Die Situation verschärft sich kontinuierlich durch den Anstieg des Schadenpotentials als Folge der ökonomischen Entwicklung sowie durch die Folgen der Klimaerwärmung. Um die Schäden in Zukunft einzudämmen, hat das Land Salzburg ein Hochwasserschutzprojekt ausgearbeitet, welches unter anderem auch Rückhaltemassnahmen in den angrenzenden Tauerntälern vorsieht. Diese stehen in der Kritik, da sie einen Eingriff in einen geschützten Naturraum darstellen und hinsichtlich der Geschiebebewirtschaftung sehr herausfordernd sind. Deswegen soll mit der vorliegenden Arbeit ein Alternativkonzept betrachtet werden, bei dem die Krimmler Ache, der grösste Zubringer zur Salzach im betrachteten Einzugsgebiet, mit Hilfe eines Stollenbauwerks in ein angrenzendes Einzugsgebiet in den bereits bestehenden Wasserkraftspeicher Durlassboden übergeleitet werden soll. Die wirtschaftliche Machbarkeit dieser Lösung ist nur im Falle einer dauerhaften Wasserkraftnutzung gegeben. Start Datum: 22.09.2025, Projektsprache: Deutsch

In einer Konzept- und Variantenstudie soll eine Bestvariante für Einlaufbauwerk, Stollen, Auslaufbauwerk und Wasserkraftwerk erarbeitet werden, die sowohl den Hochwasserschutz gewährleistet als auch eine Wasserkraftnutzung ermöglicht. Die Bestvariante ist in einem Vorprojekt hydraulisch-konstruktiv zu bemessen. Daneben soll die Machbarkeit der Hochwasserausleitung unter Berücksichtigung der Speicherreserven analysiert werden. Die Nutzung bestehender Wasserkraftwerke in zwei Unterstufen im Zillertal sowie die Wasserkraftnutzung durch eine neue Kraftwerksstufe Krimmler Ache – Durlassboden ist zudem bei der wirtschaftlichen Bewertung zu berücksichtigen. Die Auswirkungen der Wasserableitung auf das Erscheinungsbild der berühmten Wasserfälle an der Krimmler Ache sind mit einem Verfahren der VAW zu bewerten, und es sollen Vorschläge zu angemessenen Restwassermengen gemacht werden, um Hochwassersicherheit, regenerative Stromerzeugung und touristische Aspekte, speziell im Hinblick auf die Krimmler Wasserfälle, in Einklang zu bringen.

Für weitere Informationen bitte Barbara Stocker kontaktieren (stocker@vaw.baug.ethz.ch)

The Bu Mansour Dam was a large zoned earthen embankment dam on the Wadi Derna, approximately 16 km upstream of the city of Derna, Libya. In September of 2023, the dam was overwhelmed by inflow due to intense rainfall. The dam ultimately failed, producing a massive flood that was catastrophic to the city of Derna. The process of failure remains uncertain, but one plausible theory is that the dam was overtopped, causing the downstream portion of the dam to erode, and thus destabilizing the core. The core eventually broke, creating a large breach that resulted in a large flood wave. The flood wave quickly propagated downstream, soon hitting Derna with devastating power and inundation. Better understanding of this series of events is crucial for future improvement of dam breach modelling, flood risk management, and emergency operations. Start date: 22.09.2025. Language of thesis: English.

The goal of this thesis is to perform a full 3-step dam breach analysis of the Bu Mansour dam breach. The project will begin with (i) modeling of the zoned dam failure by applying a recently developed method for parametric simulation of the breaching of zoned dams due to overtopping, which will produce a flood discharge hydrograph. The next step will be (ii) numerical hydraulic modeling of the downstream propagation of the flood hydrograph, using the BASEMENT software. The final step will be to (iii) assessing the flood impact to the city of Derna based on flow velocity, inundation depths, and flood arrival times, in order to map the flood intensity and extents. Modeling will be assessed and improved based on comparison with observations of the actual inundation and flood intensity. This project will be a valuable test case for the new parametric simulation method and for the workflow of simulating dam failure with BASEMENT. Previous experience with numerical modeling would be beneficial.

For further information please contact Dr. Matthew Halso (halso@vaw.baug.ethz.ch).

Sediment Bypass Tunnels (SBTs) are an efficient measure for managing reservoir sedimentation by routing sediment-laden flows around reservoirs. The Solis SBT, located on the Albula river in the Eastern Swiss Alps, was constructed to reduce or even stop sedimentation and contribute to the restoration of sediment connectivity between the upstream and downstream river reaches. With high sediment loads and flow velocities, the invert of SBTs is prone to hydroabrasion, which can lead to high maintenance costs and potential risks to structural integrity. In this thesis the hydroabrasion resistance of six invert materials at the Solis SBT, including different types of concrete, cast basalt plates, steel plates, and high-strength materials, shall be investigated. The study makes use of data from 3D laser scanning of the tunnel invert and from continuous bedload transport monitoring by a Swiss plate geophone device, along with hydraulic data from the operator, ewz (Zurich Electric Company). The primary goal is to determine the spatially averaged, maximum, and minimum abrasion depths and patterns along the tunnel, and to analyze the impact of sediment and hydraulic conditions on abrasion rates. We offer the student the opportunity to participate in the 4th International Workshop on Sediment Bypass Tunnels in Munich, taking place from 8 to 10 September, to become acquainted with the topic of this study.

The goal of this thesis is to investigate the hydroabrasion resistance of six different invert materials in the Solis SBT by: (i) analyzing abrasion depths and patterns over time using 3D laser scanning data obtained between 2012 and 2025, (ii) assessing bedload transport rates and correlating them with abrasion patterns and hydraulic conditions, (iii) validating the mechanistic abrasion prediction model enhanced by Demiral-Yüzügüllü (2021), and (iv) comparing the abrasion resistance of the invert materials with other materials used in Swiss SBTs. The outcomes of this study will inform cost-effective SBT design and contribute to the sustainable management of hydraulic infrastructure susceptible to hydroabrasion.

For further information, please contact Ismail Albayrak (albayrak@vaw.baug.ethz.ch).

Dynamic river widening is used as a local restoration measure in affected watercourses. By removing the fixed bank protection along a particular reach, lateral erosion processes and dynamic channel migration are initiated within a limited perimeter. However, the temporal and spatial development of bank erosion in the widening depends on numerous parameters, the effects and interactions of which are still insufficiently understood. Start date: 22.09.2025 Project language: English or German No specific programming skills are required. However, the lecture “River Morphodynamic Modellings” is mandatory.

The goal of this thesis is to investigate the morphodynamic processes within river widenings in relation to different floodplain offset heights and length of the widening. The 2D morphodynamic simulations will be performed with the software BASEMENT and the model will be calibrated and validated with experimental data that will be provided from large-scale laboratory experiments at VAW. Comparison to experimental data has the advantage of clearly defined boundary conditions and topographic measurements of high temporal resolution.

For further information please contact Paul Demuth (demuth@vaw.baug.ethz.ch)

Die Wasserkraftanlage Nuova Biaschina ist die letzte Stufe der Leventina-Kette im Kanton Tessin. Dem Tagespeicher Val d’Ambra mit einem Nutzvolumen von 370‘000 m3 fliesst das Wasser aus den Oberstufen mittels eines Druckstollens zu. Zudem wird das Wasser des direkten Einzugsgebiets gefasst. Von der Seewasserfassung startet ein Schrägschacht bis zur Zentrale, welche mit drei Maschinengruppen mit je 18 m3/s bzw. 49 MW ausgerüstet ist. Das Management von Sedimenten inkl. Schwebstoffen ist aufwändig und direkt an die Verfügbarkeit der Energieproduktion gekoppelt. Um die Verstopfungsgefahr zu reduzieren, wurde der Einlaufrechen mit einem einzigartigen Reinigungssystem ausgerüstet: durch Leitungsrohre wird Druckluft gegen den Rechen geblasen, um das abgesetzte Feinmaterial wieder aufzuwirbeln (resuspendieren). Das Vorgehen hat nur eine beschränkte Wirkung und muss bei unterbrochenem Betrieb der Zentrale ausgeführt werden, was die Flexibilität der Anlage einschränkt. Im See werden jährlich ca. 1‘500 m3 Sedimente mechanisch entfernt und auf eine Deponie gebracht. Die Reinigung benötigt eine Woche Zeit mit entsprechenden Produktionsverlusten. Dazu wird die Beschaffung von Deponievolumen immer schwieriger.

Ziel dieser Arbeit ist die Bearbeitung eines konkreten Vorschlags für die Optimierung des ganzen Einlaufbauwerks, inklusiv Stahlbetonstruktur, Grob- und Feinrechen, Reinigungsmaschine, Spülvorgang, usw. Das Projekt beginnt mit der Beschaffung von bestehenden Dokumenten (Pläne, Bilder, Berichte, Berechnungen, ..). Eine Begehung ist während der nächsten Seeentleerung Ende November 2025 vorgesehen. Der nächste Schritt ist die Bearbeitung von konzeptionellen Varianten mit der entsprechenden Auswertung und Kostenschätzung. In einem letzten Schritt wird ein Vorprojekt mit grober hydraulisch-konstruktiver Bemessung und Darstellung der Lösungsvorschläge entwickelt.

AET – Azienda Elettrica Ticinese, ing. Nicola Tatti (nicola.tatti@aet.ch); VAW, ETH Zurich, Dr. Simone Pagliara (pagliara@vaw.baug.ethz.ch)

Reservoir dams are critical infrastructure in modern society, supporting key functions such as hydropower production, flood control, climate change adaptation, irrigation, and drinking water supply. Low-level outlets (LLOs) serve as crucial safety structures of reservoir dams, enabling water level regulation and facilitating rapid drawdown during maintenance or emergency scenarios. The flow within LLOs is characterized by a transition from pressurized flow upstream to supercritical free-surface flow downstream of a regulating gate. In the free-surface tunnel section, the flow exhibits high turbulence and velocities, often reaching 30–60 m/s depending on the available head. These conditions result in significant air entrainment and transport, which can lead to sub-atmospheric pressures, causing potential challenges such as gate vibrations and cavitation. To mitigate these issues, flow aeration is indispensable, ensuring the safe and reliable operation of LLOs.

Recent experimental investigations at the Laboratory of Hydraulics, Hydrology, and Glaciology (VAW) have elucidated the influence of hydraulic parameters, tunnel geometry, wall roughness, and air vent design on LLO flow behaviour. These studies have yielded empirical equations that offer valuable guidance for the safe design of LLOs. However, the inherent scale effects in experimental models and the scarcity of high-quality prototype data pose challenges in validating these findings. In the summer of 2025, an experimental campaign will be conducted at the LLO of Spitallamm Dam (Switzerland), where air demand and high-velocity flow properties will be measured with sophisticated instrumentation. Complementing this effort, the present study involves experimental testing using the LLO physical model currently available at VAW. The tunnel geometry in the model will be modified to replicate the characteristics of the LLO tunnel of Spitallamm Dam. The primary objective of the thesis is to quantitatively assess scale effects, contributing to the development of safer design guidelines. This research provides the student with an opportunity to deepen his/her understanding of the hydraulics of high-velocity air-water flows while gaining hands-on experience with advanced laboratory instrumentation and data analysis techniques. The outcomes are expected to enhance the reliability of LLO designs and contribute to the advancement of hydraulic engineering practices.

For further information please contact Dr. Simone Pagliara (pagliara@vaw.baug.ethz.ch).