Listen
19 Ergebnisse
Ergebnisse nach Hochschule und Institut
Publikation Simulation of policies for automated ride-hailing and ride-pooling services(05.01.2025) Kagho, Grace; Balac, Milos; van Eggermond, Michael; Erath, AlexanderAutomated vehicles are becoming more prevalent, and the disruption they would cause in combination with ride-hailing and ride-pooling services could be tremendous. Therefore, this study investigates the impacts of ride-hailing and ride-pooling automated fleets in two Swiss cities, Chur and Zurich, and potential policy measures to steer their operations towards more sustainable solutions. We employ the results of the stated preference survey and combine the estimated mode-choice and car ownership model results with the agent-based simulation, MATSim, to simulate the impacts of various scenarios. We find that automated ride-hailing (aRH) and automated ride-pooling (aRP) services do not seem to be competing for the same demand. In general, these services would lead to a reduction in total travel time but an increase in total vehicle distance, which is more substantial in transit-oriented Zurich than in car-oriented Chur. Furthermore, we found that even though the proposed policies increased vehicle occupancy, they did not manage to overcome the increase in VKT, signaling the need for more targeted policies and operational strategies. Finally, we provide recommendations for transport policy and future research based on our findings.04B - Beitrag KonferenzschriftPublikation Comparing Q347 development and regionalization using recent data in two Swiss cantons(09.11.2024) Dups, Yanick; Lebrenz, HenningIn Switzerland, low flows are characterized by the discharge level corresponding to a 95% exceedance probability on a ten-year average flow duration curve, referred to as Q347. This threshold not only has significant implications for planning but also requires authorities to adjust the operation of relevant infrastructure to mitigate ecological impacts on watercourses. The value of Q347 can be determined from a flow duration curve if a discharge time series of at least ten years is available. However, for smaller catchments such time series are typically unavailable, necessitating the regionalization of Q347 values. In Switzerland, multiple linear regression has been established to estimate the area-specific discharge q347 for ungauged basins. The primary objective of this study was to regionalize Q347 values for small, ungauged catchments (383 in the Canton of Solothurn and 9'034 in the Canton of Zürich) each with an area of less than 100 km². Daily discharge, precipitation, and temperature time series were collected for a 30-year study period from 1990 to 2020 from 56 gauged catchments in Solothurn, and similarly for a ten-year study period from 2013 to 2023 in Zürich, focusing on catchments smaller than 500 km² surrounding the target areas. A total of 30 “static” parameters delineating geometry, topography, geology, land use, and drainage along with nine “climatic” parameters describing temperatures, precipitation distributions, and potential evapotranspiration were defined and computed to characterize both gauged and ungauged catchments. The temporal variability of low flow events was then analysed for observed catchments in the two study areas. Over the past 30 years, the frequency of low flow events below the threshold has systematically increased, while the ten-year Q347 values for these catchments have decreased during the same period. Three multiple linear regression methods were developed and implemented to be coupled with two adjustment techniques supplementing truncated discharge time series. Validation of the proposed models showed reduced errors and increased linear correlations between estimated and observed values compared to standard models. Notably, a spatially more homogeneous yet catchment-specific distribution of estimated values is observable. The proposed models yielded promising results, particularly when time series remain unadjusted, or adjustment is done using the Antecedent Precipitation Index (API) combined with the flow duration curve of a donor basin (Ridolfi et al., 2020). Using recent data for parameter selection and model fitting, especially in the Zürich study area (2013-2022), often resulted in lower Q347 values compared to standard models, reflecting an adaptation to current climatic trends.06 - PräsentationPublikation Introducing the pedestrian accessibility tool. Walkability analysis for a geographic information system(SAGE, 2017) Erath, Alexander; van Eggermond, Michael; Ordóñez, Sergio A.; Axhausen, Kay W.The indexes for walkability proposed so far refer generally to the closest amenities and public transport stops and the existing network structure. The weights of the attributes do not reflect the independently measured preferences of the users and residents. Design attributes such as the location and type of crossings and walkway design features are usually surveyed in walkability audits. However, such attributes are usually not considered when pedestrian walksheds or other accessibility-based walkability indexes are calculated. Nevertheless, these design attributes are very relevant for actual planning decisions. The proposed walkability index can be behaviorally calibrated, has been implemented as a geographic information system tool, and is published as open source software. The pedestrian accessibility tool allows the evaluation of existing and future urban plans with regards to walkability. The tool calculates Hansen-based accessibility indicators with the use of a customizable specification of the generalized walking costs, and it incorporates user-defined weights of destination attractiveness. The basic user workflow of the tool is summarized. Three case studies show real-world applications of the tool to support the planning of pedestrian infrastructure in an urban context. With indications of potential areas of improvement that have been reported by pilot users working in an urban planning department, hints are also given for future research.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Virtual reality and choice modelling. Existing applications and future research directions(Edward Elgar Publishing, 2024) van Eggermond, Michael; Mavros, Panos; Erath, Alexander; Hess, Stephane; Daly, AndrewResearch eliciting individuals’ preferences, including stated preference (SP) research, have long utilised imagery as stimuli to visualise either attributes or situations deemed too complex to be expressed verbally. The advent of Virtual Reality (VR) offers choice modelers with exciting new opportunities. This chapter outlines key concepts underlying VR and summarises previous research combining VR and choice modeling. It provides a framework of different dimensions that should be considered when developing VR experiments, including technological aspects (display technology and movement) and other aspects, such as survey duration, motion sickness and the representation of time. The chapter concludes with several ways to further combine choice modeling and VR.04A - Beitrag SammelbandPublikation Event-based flood estimation using a random forest algorithm for the regionalization in small catchments(Eigenverlag des Instituts für Wasser- und Umweltsystemmodellierung, 07/2022) Pavía Santolamazza, DanielaThe hydrological cycle is a complex system, composed of multiple variables, which in most cases are not measured. This is one of the reasons why it is a challenge to have models that adequately represent the expected discharges. The PUB initiative reinforces the need on having models that capture the different catchment interactions and represent various catchment processes. These models are more robust and thus can be more reliable to transfer to the ungauged catchments. In recent years, the field of hydrological research has focused on understanding and explaining the different processes present in catchments. Nevertheless, few applications that include pre- cipitation, the main responsible of runoff change,are found.Further understanding of the temporal and spatial dependence of the meteorological event triggering the floods is needed. In this study, an analysis of the meteorological event triggering the floods was carried out. The concept of entropy was used to characterize the temporal distribution of precipitation. It was found that the precipitation temporal entropy is a better indicator of hydrograph shape than the duration or the intensity. Further, the geographical interdependence of the amount of precipitation and the temporal precipitation entropy causing the floods was described looking at the association of sta- tions triples. This suggested that, up until a given quantile, flood events are more likely caused by precipitation events of total coverage. However, for larger quantile values, it is observed that as the quantile increases the probability of observing joint occurrence in space decreases. The tem- poral distribution of precipitation events causing the floods showed to be more associated in space than the amount of precipitation triggering the floods. Nonetheless, this temporal distribu- tion is not constant over all flood events, what can be attributed to d ifferent flood mechanisms. The Antecedent Precipitation Index (API) was used to explain the soil moisture content. The em- pirical distribution of (API) at the time of a flood was compared with empirical distributions of unconditioned (API) data series. T o this end, the Wilcoxon statistic and the Kolmogorov -Smirnov distance were used to compare the empirical distributions. The re sults showed that the soil mois- ture triggering the floods is not an annual extreme, rather a value close to the monthly maximum (API). Further, it was observed that the longer memory of the catchment gives more information about the occurrence of the flood. Additionally, in order to estimate the catchment reaction at the time of a flood, a regiona lization of the flood wave hydrographs was carried out. T o this end, three methods of defining the simi- larity of the floods were considered. In all three methods, the similarity matrices were generated using the random forest algorithm. The novelty of this procedure was the use of a supervised random forest to describe the similarity of the floods events. It was supervised given that the algorithm was trained to estimate a target variable. The proximity matrix was obtained by calcu- lating the joint occurrence of floods in the random forest space. For evaluating the estimation the hydrograph peak and the time to peak were used. In all three methods, the same tendencies were observed, an overestimation of the peak and an underestimation of the time to peak. However, the bias was observed to be smaller when an ensemble of similarity matrices was used as com- pared to having a single similarity matrix. Moreover, an approach using an unsupervised random forest was compared to the supervised one. It was found that the unsupervised random forest yields larger estimation errors. Finally, to estimate the volume of the flood event a rainfall-runoff model was modified to represent the study region. The model chosen in this study was EPIC. The model was calibrated to be more representative of the study region. To this end, the estimation errors in the space of the model parameters were studied. This allowed to find the model parameters that can better represent the study area. The values obtained were considered reasonable. For example, it is observed that the longer memory of the catchment is more representative of the study catchments, which are the same results as when analyzing the meteorological phenomenon causing the floods. Further, the values obtained for the regional constant, parameter modifying the initial abstraction of the catchment, were found to be smaller than the original ones obtained for United States catchments, which agrees with other studies in European catchments.02 - MonographiePublikation Nachhaltige Ansätze zur Parkraumplanung(Bundesamt für Strassen, 09.07.2024) Erath, Alexander; van Eggermond, Michael; Sieber, Mark; Graf, Samuel; Perret, Fabienne05 - Forschungs- oder ArbeitsberichtPublikation Parameterization and results of SWE for gravity currents are sensitive to the definition of depth(American Society of Civil Engineers, 12.03.2021) Venuleo, Sara; Pokrajac, Dubravka; Tokyay, Talia; Constantinescu, George; Schleiss, Anton J.; Franca, Mário J.Rigorously derived shallow water equations (SWEs) are applied to results of large eddy simulation (LES) of a continuously fed gravity current in order to assess (1) sensitivity of current depth results to its definition; (2) coefficients in depth-averaged continuity and momentum equation due to the nonuniformity of density and velocity profiles; and (3) sensitivity of entrainment coefficient to definition of current depth. It is shown that using different definitions of the current depth may produce significantly different numerical results. The coefficients due to nonuniformity in the continuity equation are very close to unity, whereas the coefficients in the momentum flux and the pressure term in the momentum equation are different from unity by a margin that is very sensitive to the definition of current depth. The entrainment coefficient is more sensitive to the selected parameterization than to the definition of the current depth.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Continuously-fed gravity currents propagating over a finite porous substrate(American Institute of Physics, 31.12.2019) Venuleo, Sara; Pokrajac, Dubravka; Schleiss, Anton J.; Franca, Mário J.We present the results of laboratory investigations of continuously-fed density currents that propagate first over a smooth horizontal bed and then over a porous substrate of limited length. Inflow discharge, initial excess density, and substrate porosities are varied. Density measurements, acquired through an image analysis technique, are performed above the porous layer simultaneously with quasi-instantaneous vertical velocity profiles. After a first phase in which the current sinks into the substrate, freshwater entrainment from the bed begins and, gradually, a mixing layer forms at the interface between the surface flow and the porous bed. Shear-driven and Rayleigh-Taylor instabilities rule the dynamics of this mixing layer. The porous boundary effects are observed in the vertical distributions of both density and velocity, especially in the near-bed region. Here, larger flow velocities are recorded over porous substrates. We argue that these are due to the presence of a longitudinal pressure gradient, which in turn is a consequence of the current mass loss. Its presence over the porous substrate is proved by the current interface longitudinal slope. However, other effects of the presence of the porous substrate, such as the relaxation of the no-slip boundary condition and the bed-normal momentum exchange, also affect the velocity field. The turbulent structure changes significantly over the porous substrate: while streamwise turbulence decreases, shear and bed-normal Reynolds stresses increase in large part of the current depth. Buoyancy instabilities further enhance the bed-normal momentum flux and, in the near-bed region, contribute to turbulent kinetic energy generation together with shear.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Applying bias correction for merging rain gauge and radar data(Elsevier, 13.01.2015) Rabiei, Ehsan; Haberlandt, UweWeather radar provides areal rainfall information with very high temporal and spatial resolution. Radar data has been implemented in several hydrological applications despite the fact that the data suffers from varying sources of error. Several studies have attempted to propose methods for solving these problems. Additionally, weather radar usually underestimates or overestimates the rainfall amount. In this study, a new method is proposed for correcting radar data by implementing the quantile mapping bias correction method. Then, the radar data is merged with observed rainfall by conditional merging and kriging with external drift interpolation techniques. The merging product is analysed regarding the sensitivity of the two investigated methods to the radar data quality. After implementing bias correction, not only did the quality of the radar data improve, but also the performance of the interpolation techniques using radar data as additional information. In general, conditional merging showed greater sensitivity to radar data quality, but performed better than all the other interpolation techniques when using bias corrected radar data. Furthermore, a seasonal variation of interpolation performances has in general been observed. A practical example of using radar data for disaggregating stations from daily to hourly temporal resolution is also proposed in this study.01A - Beitrag in wissenschaftlicher ZeitschriftPublikation Measurements and observations in the XXI century (MOXXI). Innovation and multi-disciplinarity to sense the hydrological cycle(Taylor & Francis, 18.01.2018) Tauro, Flavia; Selker, John; Giesen, Nick van de; Abrate, Tommaso; Uijlenhoet, Remko; Porfiri, Maurizio; Manfreda, Salvatore; Caylor, Kelly; Moramarco, Tommaso; Benveniste, Jerome; Ciraolo, Giuseppe; Estes, Lyndon; Domeneghetti, Alessio; Perks, Matthew T.; Corbari, Chiara; Rabiei, Ehsan; Ravazzani, Giovanni; Bogena, Heye; Harfouche, Antoine; Brocca, Luca; Maltese, Antonino; Wickert, Andy; Tarpanelli, Angelica; Good, Stephen; Lopez Alcala, Jose Manuel; Petroselli, Andrea; Cudennec, Christophe; Blume, Theresa; Hut, Rolf; Grimaldi, SalvatoreTo promote the advancement of novel observation techniques that may lead to new sources of information to help better understand the hydrological cycle, the International Association of Hydrological Sciences (IAHS) established the Measurements and Observations in the XXI century (MOXXI) Working Group in July 2013. The group comprises a growing community of tech-enthusiastic hydrologists that design and develop their own sensing systems, adopt a multi-disciplinary perspective in tackling complex observations, often use low-cost equipment intended for other applications to build innovative sensors, or perform opportunistic measurements. This paper states the objectives of the group and reviews major advances carried out by MOXXI members toward the advancement of hydrological sciences. Challenges and opportunities are outlined to provide strategic guidance for advancement of measurement, and thus discovery.01A - Beitrag in wissenschaftlicher Zeitschrift