Budapest University of Technology and EconomicsFaculty of Civil Engineering - Since 1782

Morphological changes of rivers strongly determine the possibilities of the different water uses. For instance, inadequate water depth at shallow sections in low flow regimes can decrease navigational possibilities, incision of the river bed can lower ground water levels, or sediment deposition in side branches can deteriorate the quality of habitats. Sedimentation processes on the floodplain can decrease the lateral habitat connectivity, or even increase the flood risks. The morphological development of river beds can occur on different temporal scales, as on one hand, long-term low and mean flow discharges can slowly shape the bed, but on the other hand, floods can have short but very intensive influence on the morphodynamics. During floods, the bed erosion capacity can strongly increase resulting in the temporary rearrangement of the bed morphology in the main channel. At the same time, the high sediment transport capacity during floods leads to significant suspended sediment load, which, in case of overbank flows, can reach the floodplains and be trapped there due to the locally decreasing flow velocities. On a long-term, floodplains are exposed to the continuous sedimentation, however, in a strongly varying nature, depending on several features, such as the topography, land use, density and type of vegetation, dominant sediment type, flow features, etc. 

The proposed PhD research focuses on the impact of floods on the river morphology, with a special attention on floodplain sedimentation. The main goal of the research is to gain a general understanding about the steering hydromorphological processes in floodplain sedimentation and to work out investigation tools that can quantify the morphological changes. The research will be built on two pillars: i) assessment of field data and ii) computational modeling. For the development of the assessment methods, case studies from Hungary will be chosen, preferably for large rivers, such as the Danube or the Tisza. Field data, most probably detailed topographical information, such as LIDAR data, will be collected which can provide quantitative information on the spatial and temporal behavior of sedimentation processes. In case of significant data gaps, complementary field data collection, e.g. sediment sampling will be performed at the study sites. Literature as well as the collected field data will be used to set up, parameterize and validate computational hydrodynamic and sediment transport models of different dimensions (1D-2D-3D) to study the hydromorphological processes.

 

A few relevant questions that should be addressed within the proposed research:

    • What are the determining features (hydrological, morphological, vegetation) in floodplain sedimentation processes?

    • How do the deposited sediments behave in the floodplain? Can it be deposited and compacted, or can it resuspend?

    • What is the role of vegetation in the sedimentation processes? 

    • Can computational models adequately simulate floodplain sedimentation?

    • How does floodplain sedimentation influence flood conveyance capacity? Does it lead to increasing flood risks?

    • How does floodplain sedimentation influence the lateral connectivity of rivers?