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To calibrate and validate a 3Dimensional mud model with field data for the Blyth estuary (Suffolk, UK) and determine if the 3D model is an improvement to the existing 2D model

Wardt, W. van de (2016) To calibrate and validate a 3Dimensional mud model with field data for the Blyth estuary (Suffolk, UK) and determine if the 3D model is an improvement to the existing 2D model.

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Abstract:In 2003 Thomas D. Benson completed his PhD in which he had analysed the sediment transport of the Blyth estuary (Suffolk, UK). This PhD required building a 2D depth averaged-model of the sediment transport of this estuary (Benson, 2004). However, as the state-of-the-art in modelling sediment transport progressed over time, this 2D model needed to be converted into a 3D model. The 3D sediment transport model has been modified and improved significantly in the last few years, but the model has only partly been tested against a limited amount of measured data. Therefore, in this thesis, the model will be calibrated and validated against the available data, resulting in the following goal: To calibrate and validate a 3Dimensional mud model with field data for the Blyth estuary (Suffolk, UK) and determine if the 3D model is an improvement to the existing 2D model. After exploring the properties of the estuary, and the sediment transport within an estuary, a dataset for which the model is calibrated and validated is determined. The data collected during spring tide, which has the highest current speeds and suspended sediment concentrations, will be used for the calibration of the model. The dataset collected during neap tide, which has lower current speeds and suspended sediment concentrations, will be used for the validation of the model. After calibration and validation, the best results for the model are as shown in Figure 1. The order of graphing is as following: 1. Water level on the spring tide 2. Suspended sediment concentration on the spring tide 3. Water level on the neap tide 4. Suspended sediment concentrations on the neap tide To quantify the quality of the model, the Brier Skill Score is calculated. This Brier Skill Score can be split up in 3 components, respectively the phase error, amplitude error and error in the average mud concentration. This is useful, because it points out where the weaknesses of the model lay. To see if the 3D model is an improvement to the existing 2D model, the Brier Skill Score for both the 2D and the 3D model is calculated. The model quality is also assessed using the Root Mean Square Error of the concentration. From the results summarised in Table 1, it can be concluded that the 3D model gives a better fit to the data than the 2D model. Even though it performs slightly worse on the spring tide than the 2D model, possibly due to uncertainties in the 3D model, the model is an excellent fit for the neap tide. The 3D model can possibly be improved by reducing the uncertainties. This could be achieved by collecting more data about the estuary and use those in the calibration. Important data are the soil type at different locations in the estuary, and the suspended sediment concentrations at these different locations. Since the boundary conditions could play an important role when the current speeds increase during the spring tide, it could also be considered measuring the erosion at the boundaries of the channel, to see how this boundary behaves during these high current speeds. Since it will take a while for the boundaries to erode, the measurements should probably be taken over a couple of tides. However, it can be concluded that the model works very good for the given data sets, but there are many uncertainties in the model parameters, which can probably be resolved by doing further research.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Subject:56 civil engineering
Programme:Civil Engineering BSc (56952)
Link to this item:http://purl.utwente.nl/essays/70667
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