Thesis supervisor: Gergely Tihamér Török
Location of studies (in Hungarian): Vízépítési és Vízgazdálkodási Tanszék Abbreviation of location of studies: BMEVV
Description of the research topic:
A common technic in the regulation of watercourses is the construction of wing dams. As a result of the transverse structure, the flow narrows locally. A weak flow pattern is formed between the wing dams and in their downstream area, which traps the sediment at low and medium water stages. However, erosion of previously deposited sediment is expected as a result of flood waves. For this reason, the spaces between the wing dams should be taken into account as sink or source term in the calculation of the sediment budget, depending on the water stage. Therefore, the sediment conditions of the regulated river sections may differ from the natural features. Based on the models found in the literature, it is not yet possible to provide a reliable answer to what extent and in what way the wing dams change the sediment budget. In the case of the Waal River, a rough estimate based on field measurements shows that the amount of sediment washed from the area between the wing dams is significant. This experience suggests that the sediment movement in groin fields may be significant for other rivers as well. Another questionable area is the effect of sediment conditions changed by interventions on downstream morphological processes.
The aim of the research topic is to examine the questions formulated above: to explore the effect of wing dams on sediment budget. The river section to be examined is the Hungarian Upper Danube. The study fits into the ongoing research topics and projects supervised by the morphodynamic research group at the Department of Hydraulic and Water Resources Engineering. The morphodynamic characteristics and data base required for the study are provided by literature sources and data collected by the Department in measurements and expert projects. The measurement infrastructure of the Department provides the possibility to perform additional targeted measurement campaigns.
In the subtasks to be developed during the study, we are looking for answers to questions such as how the trapped or eroded sediment is related to the flow stage (e.g., water level, duration)? What parameters can be used to characterize the critical state when the amount of eroding and settling sediment amounts are equal? Furthermore, how does the amount of sediment trapped and later eroded relate to the total amount of sediment in the river? As part of the study, we look for sediment characteristics that are suitable to describe the influence of wing dams. We intent to explore the dependence of these sensitive sediment parameters on water level.
Calculations need to be performed with 3D sediment transport modeling. Accordingly, in the initial phase of the research, it is necessary to set up and verify a sediment model that is suitable for the study of the phenomenon described above. A pivotal point of the research is the proper consideration of sediment movement. With the help of the constructed model, it is necessary to perform targeted studies, based on which the role of the wing dams can be characterized. At the end of the study, characteristic curves are expected to be generated, which characterize the changes in the sediment budget as a function of the morphodynamic parameters.
Finally, the last task is to examine, based on the characteristic curves, whether the altered sediment budget may have an effect on downstream morphological processes. This subtask presumably requires the study of a long river section where the application of the 3D numerical model would not be efficient, so we plan to use a lower dimensional approach.
Preferred competencies:
• experiences in numerical hydraulic and sediment transport modelling
Number of students who can be accepted: 1
Deadline for application: 2024-05-31
2024. IV. 17. ODT ülés Az ODT következő ülésére 2024. június 14-én, pénteken 10.00 órakor kerül sor a Semmelweis Egyetem Szenátusi termében (Bp. Üllői út 26. I. emelet).
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