University of Twente Student Theses


Improving the parametrization of the main channel bed roughness in the Midden-Waal

Haase, J.R. (2023) Improving the parametrization of the main channel bed roughness in the Midden-Waal.

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Abstract:Rivers are an important part of the Dutch landscape. These waterways are vital for navigation and create unique ecosystems. Water is used for domestic, industrial and agricultural purposes. Their proper management protects us from floods and the effects of droughts. As flood and drought mitigation measures are based on hydrodynamic river model simulations, accurate water level predictions from these models are needed to ensure that measures are designed in a cost-effective way. Hydrodynamic models are relatively good at predicting water levels in the discharge range for which they are calibrated. However, there is uncertainty in predicting water levels outside the discharge range for which they are calibrated. One of the main sources of this uncertainty is the uncertainty in the main channel bed roughness parameterisation. River dunes are thought to be the main source of main channel roughness. The parameterisation of these bedforms to calculate main channel bed roughness is inaccurate as it does not account for the actual bedforms. The bed is parametrised using implicit 2D river dune geometry parameters by estimating these parameters as a function of water depth. A 2D parameterisation often only captures the dunes on the centreline of the fairway, while the centreline of the fairway is not representative of the entire river bed, resulting in an inaccurate roughness prediction (1).Furthermore, the implicit bedform covers the discharge history dependent bed evolution in the hydrodynamic river model DHYDRO, which has a large influence on the main channel bed roughness, as extreme discharge events are not accurately simulated, while these events are of great interest (2). Finally, the length scale over which roughness is assumed to be constant is too large to capture the spatial variation in bedforms (3).
Item Type:Essay (Master)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering and Management MSc (60026)
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