碩士 / 國立中央大學 / 水文所 / 95 / Since a considerable amount of sewage from Taipei metropolis is discharged into the lower reach of the Danshuei River, it may significantly affect the estuarine environment and ecosystem. To understand the circulation in the estuary and the adjacent coastal zone is crucial to their environmental protection. For this study were collected tidal levels, ocean currents, river discharges, and satellite images for analysis of the shape and variation of the Danshuei River plume and understanding of its driving mechanisms. A three-dimensional model is adopted to facilitate the investigation of the river plume and estuarine circulation.
Results derived from model results and observations indicate that the plume is of about 5 m thick. Two hours after low tide, the plume extends toward the southwest and can reach 6~7 km from the river mouth. The simulation is consistent with that revealed by satellite images. Discharge rate (500 cms, cms =m3/s), distribution of plume extends 2~3 times offshore than the control run (90 cms). During low discharge, the plume extends be visible in the sea. While the discharge is greater than 50 cms, the plume during a high farther can hardly becomes more visible in the sea. During a flood caused by the torrential rain, the model predicts that the salinity in the coastal zone begins to change dramatically 17 hours after the flood began. After about 70 hours, the salinity returns to nearly the initial level. Based on a model run using a peak discharge rate of 300 cms, the model results show that the residence time is on the order of 72 hours. Through the numerical study with wind forcing, at a northeasterly wind of 10 m/s in speed, the plume extends westward prominently and the surface velocity doubles toward southwest. Under a southwester (by wind of 4.5 m/s in speed), the plume was restricted to a narrow band along the right side coast during ebbing tide, but the wind has little effect on the plume during flood tide.
| Identifer | oai:union.ndltd.org:TW/095NCU05761003 |
| Date | January 2007 |
| Creators | Jhe-jhen Lin, 林哲震 |
| Contributors | 詹森, 劉康克 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 72 |
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