碩士 / 國立聯合大學 / 土木與防災工程學系碩士班 / 106 / Geomorphic change is one of important factors to affect the hydrodynamics in an estuary, and this also affects salt transport and, thereby, the distribution and salt intrusion. The Danshui River passes through the Taipei city, which is the area with high population density and the center of government and economy. Therefore, the water uses and the geomorphic changes of the estuarine system of the Danshui River have been noticed. In this study, a three-dimensional hydrodynamic and salt transport model was used to simulate hydraulic characteristics and salt transport of the estuarine system of Danshui River. After the model calibration and validation, the model was applied to explore the effects of geomorphic change on hydraulic characteristics, e.g., tidal prism, residence time, and plume, in the Danshui River estuarine system in 1981 and 2015, respectively.
In terms of calibration and validation of hydrodynamic model, the measured data of the water level, tidal current, and salinity in 2015, 2016, and 2017 were compared with model predictions. The results of the calibration and validation for the water level show that the values of skill score were between 0.830 (excellent) and 0.999 (excellent); besides, the tidal currents illustrate the values of skill score were between 0.341 (good) and 0.957 (excellent), and those for salinity indicate the values of skill score were between 0.313 (good) and 0.955 (excellent). Based on the results of model calibration and validation, the model simulations reproduce the measured data.
The validated model was then used to explore the effects of geomorphic change on hydraulic characteristics in the Danshui River estuarine system. The results indicate that the time series of water level, tidal current, and salinity of Danshui River estuarine system in 1981 and 2015 (present), respectively, were affected by geomorphic changes; also, there were time lag and the change of tidal range. Considering the effects of geomorphic changes on salt intrusion, the results reveal that, in Danshui River-Dahan Stream and Hsintien Stream, the distances of salt intrusion in 2015 were shorter than those in 1981, while, in Keelung River, the distance of salt intrusion in 2015 was farther up-river than that in 1981. Concerning the effects of geomorphic changes on tidal prism, the results show that, in the Danshui River estuarine system, the tidal prism in 2015 was less that in 1981. Accordingly, it indicates that Danshui River’s channel was influenced by the geomorphic changes. In the estuary, the volume of outflow during ebb tides in 2015 was less than that in 1981. In terms of the effects of geomorphic changes on residence time, in this study, the residence time of the Danshui River estuarine system was calculated using the theories of Sanford et al. (1992) and Luketina (1998). The results show that the residence time in 2015 was less than that in 1981. Namely, the time that pollutants stayed in the Danshuei River estuarine system in 2015 was shorter than that in 1981. In addition, the model was applied to explore the effects of geomorphic change on the plume of the coast. The results indicate that the plume distance in 2015 was farther than that in 1981; hence, it indicates that, in 2015, the degree of pollution diffusion in the adjacent coastal area of Danshuei River was better.
| Identifer | oai:union.ndltd.org:TW/106NUUM0653008 |
| Date | January 2018 |
| Creators | Ke, Min-Hsin, 柯旻欣 |
| Contributors | Liu, Wen-Cheng, 柳文成 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 103 |
Page generated in 0.0114 seconds