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Using Tygron to assess the extent of hindrance due to stormwater in Olst

Verboom, M. (2022) Using Tygron to assess the extent of hindrance due to stormwater in Olst.

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Abstract:This study looks at the predictive power of Tygron in assessing the extent of hindrance due to stormwater in villages in the Netherlands. This was done by carrying out a sensitivity analysis on different parameters. The results were used to construct a base model which was able to predict the extent of hindrance due to stormwater in Olst. These results were compared with validated results simulated via the software InfoWorks to assess the predictive power of Tygron. Firstly, the schematization of Tygron was investigated. The schematization of the sewer system has some major simplifications. The largest is that water can enter the sewer system at a lower location than it can overflow. Also, the sewer system is schematized as a point-based construction, with this the sewer system in Tygron has no bottlenecks inside the network while this is often the case in reality. With the schematization known, a sensitivity analysis was carried out. The results of Tygron were checked if they were sensitive to the following parameters; the grid size, initial groundwater depth, pump capacity per sewer area, storage capacity of the sewer system, the capacity of the sewer overflow and the height of the sewer overflow. During the sensitivity analysis, it became clear that the results of Tygron are not sensitive for the grid size when set finer than 1x1m, and the initial groundwater depth. The results are sensitive to the other parameters, especially the overflow height combined with maximum overflow discharge for larger rain events. When the open water reaches the sewer overflow height, the overflow will stop discharging water. In reality, the pressure behind the overflow is important, this is not taken into account in the schematization of Tygron. Therefore, to have an overflow discharge, it is recommended to set the overflow height one meter above ground level. Secondly, the water hindrance as simulated by Tygron was assessed. The water hindrance extent in Olst, according to Tygron simulations, is large for heavy rain events when looking at the average water level per street section. When comparing the maximum simulated water levels, almost every street experiences water hindrance. Even for the smallest simulated rain event in this research (Bui08) on 114 of the 117 streets, water hindrance occur. Thirdly, a result comparison was done between the results obtained by Tygron and InfoWorks for three rain events. The parameters for the compared Tygron were set on values which were close to reality or adapt for the simplifications and schematization of the Tygron model. The overall performance between Tygron and InfoWorks is not well. There is much more water in Tygron compared with InfoWorks for all rain events. When taking a closer look at where the maxima water levels are simulated, similar results can be seen between Tygron and InfoWorks. When taking the highest 10% simulated water levels, 60% is simulated in the same location. For assessing the extent of hindrance due to stormwater in Olst, Tygron is not considered to give the same water volumes as InfoWorks. However, Tygron simulates the maximum water levels in similar locations as InfoWorks. Tygron is therefore recommended to be used for quick scans, but not for detailed assessments of the extent of hindrance due to stormwater.
Item Type:Essay (Bachelor)
Faculty:ET: Engineering Technology
Programme:Civil Engineering BSc (56952)
Link to this item:https://purl.utwente.nl/essays/92659
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