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Institute of Hydraulic Engineering

Research: Hydraulic Laboratory

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Focal point of research activities:
Hydromorphology

Summary:

Hydromorphology describes the interaction of water and sediments in water bodies on spatial as well as on temporal scales. Erosion, transport and sedimentation are vital processes and play an important role in the evolution of the highly dynamic hydromorphological fluvial systems. However, besides natural factors, which govern the river bed evaluation and the development of bed structures such as ripples and dunes, anthropogenic influences also affect the hydraulic characteristics. Hence, these processes are in the focus of our research. Our work involves not only fundamental research to understand the processes behind the morphological behavior but also applied projects in collaboration with administration as well as the private sector. Balancing ecological demands and structural implementations is the main aim of this research. To achieve these goals analytical, numerical and physical models as well as field measurements are used at our department.
The main topics in this field of research are:





Sediment transport, morphodynamics and sediment balances in watercourses

Understanding and describing bedload and suspended sediment transport is an essential aspect for long-term predictions. Only with this knowledge an accurate prediction of e.g. the development of the river bed is feasible. A large number of watercourses were disturbed in their natural sediment balance due to anthropogenic measures realized in the past. By taking into account both, small and large scale sediment transport processes, it is possible to find appropriate measures to re-vitalize these river sections in a sustainable way.

Large scale processes: Developing a balance of bedload and suspended sediment transport allows an estimation of long-term river bed evolution and provides information regarding the influence of anthropogenic measures. With this knowledge nature like river training structures can be planned and implemented, which will enable a natural dynamic behavior of the river bed in the future.

Small scale processes: A further research focus lies on the analysis of so called colmation processes, which is the transport of fine sediments into the porous structure of the river bed. Beside the examination of the governing process in the laboratory a core area is the development of practical in-situ measurement techniques to quantify the degree of colmation.




Physical model of a gravel sluice
Mesh for the simulation of river training structures (revetment in combination with a river bed widening)



Sediment management in reservoirs

Reservoirs interrupt the continuous sediment transport in watercourses and often lead to problems concerning reservoir sedimentation. Here, the research emphasizes on in-situ measurements, numerical simulations as well as basic research on the erosion behavior of cohesive sediments. The IWS has developed a flume to assess a vertical profile of the critical shear stress of sediment samples (SETEG). Moreover, in-situ measurement devices help to gain a better understanding of the processes and help to advance the development of numerical approaches. Furthermore, we examine the microbial settlements (for example algae and biofilm) and its impact on sediment erosion in an interdisciplinary team of biologists and engineers.




Simulated distribution of suspended sediments in the Angostura reservoir, Costa Rica




Nature-compatible river engineering and river development

Regarding the European water framework directive a good ecological status must be achieved for all European watercourses. Thus, the restoration of natural morphodynamic functions of rivers is essential to accomplish this objective. Our research in this topic is mainly focused on practical applications of numerical models to predict the morphological long term behavior of rivers for different scenarios, such as the implementation of river bed widening sections or river revetments. A basic element is the analysis of ecological deficiency of rivers which is needed to develop and optimize river training measures. An important tool to evaluate the potential success of proposed measures is the software tool CASiMiR which has been developed by IWS. Casimir illustrates and facilitates the evaluation of the effects of river engineering measures on habitat suitability. It enables the optimization of river engineering projects regarding the habitat quality for fish and invertebrates not only qualitatively but also quantitatively.





Comparison of the simulated habitat quality with field investigation



Assessment of flood protection measures

Precise predictions of small and large-scale inundated areas during flood events are necessary for a sustainable and effective and integrated flood protection. Numerical models are applied to determine flood areas, water levels and flood duration. These data support the evaluation of flood intensity and risk. Moreover, the models facilitate the assessment of construction projects as well as scenarios e.g. the reactivation of retention areas and flood plains. We develop detailed options for sustainable and ecological-compatible flood protection measures by using physical models.




Numerical simulation of a flood inundation map



Related projects: