Undergraduate (Bachelor) thesis Jelle van der Zwaag

In the mass balance of a riverbed, some terms are usually assumed constant for reasons of simplicity. One of the terms assumed to be constant is the change in bedload layer, which is defined as the sediment transport divided by the particle velocity. To study the effect of this assumption, a numerical morphodynamic model has to be computed. For such a morphodynamic model to work, some input parameters and models have to be determined. The most important input models are those of the predicted sediment transport and particle velocity, which are studied in this research. The Dutch upper Rhine is used as basis for this study, with particle diameters and sediment compositions as found in earlier studies. The sediment transport data of three measurement campaigns is used to compare the predicted sediment transport by sediment transport models. Before comparison between the sediment transport models and the measured data, a small literature study is used to determine which sediment transport models might be applicable for predicting the sediment transport. With the available specifications of the sediment transport models, two fractional transport models were chosen as applicable: the model of Wu et al. (2000) and the model of Wilcock & Crowe (2003). Both original models approximate the measured data quite well, so no calibration of the models is required. The model of Wu however, shows some unusual behavior for increasing sand/gravel ratios and is more sensitive for changes in its calibration parameter. Therefore, the model of Wilcock & Crowe is chosen as most applicable for this part of the Rhine River. To determine the propagation velocity of the particles, two models of Van Rijn (1984) and one model of Engelund-Fredsoe (1976) were used. One of the Van Rijn models predicted unrealistic particle velocities, but the remaining two models approximate the particle velocity in a very similar way, approaching measurements from Francis (1973) and Luque (1974). Due to the similar behavior of both models, no choice was made between them. Eventually, the thickness of the bedload layer is determined, providing a realistic input for a 1D sand/gravel morphodynamic model. Preface To achieve an undergraduate degree in Civil engineering, an individual thesis has to be written. After consideration of several possible topics, the eventual subject was found via the blackboard community of the section environmental fluid mechanics. Under supervision of dr.ir. Astrid Blom, Lodewijk de Vet and I attended this research, both with a …