| Summary: | 碩士 === 國立中興大學 === 土木工程學系 === 91 === In Taiwan, streamflow is calculated based on the point velocity measurements for all the verticals in a river cross section using a mechanical type current meter at present. Although the method is easy, all the velocity data can’t be obtained simultaneously for a wide river during the medium and high flows. The accuracy of the flow discharge is therefore reduced. To resolve this problem, a new flow discharge estimation technology, with application of an ADCP (Acoustic Doppler Current Profiler), is adopted to rapidly and accurately observe the medium and high flows.
The flow discharge data collected recently at important gauging stations by the River Management Bureaus of the Water Resources Agency were analyzed in this study. The new flow discharge estimation technology and the stability and accuracy of the parameters [y-axis (the vertical line passing the maximum velocity of the cross section), (the ratio of mean velocity to maximum velocity of a cross section), and the estimated flow area] were discussed. The applicability of the new flow discharge measuring technology to different types of river was also evaluated.
The results of this study indicated that the y-axis for straight, narrow and deep rivers, or rivers with low flow management were stable during either high or low flow. The applicability of the new flow discharge measuring technology was fairly high. For braided stream, the y-axis was extremely unstable during low flow, but it was relatively stable and the new technology can be adopted during high flow. As for channel with tilting cross section or meandering river, y-axis was relatively stable and the new technology was applicable for medium and high flows.
In general, the correlation between the mean velocity and the maximum velocity for each station was fairly high. The value was getting stable as the water level reached a certain height. It was also found that BD (product of water surface width and flow depth at y-axis) was the best variable for estimating the cross sectional area of the flow.
Based on the field test conducted at Hsi-Nan bridge station, it was found that the flow discharge measured by the portable ADCP system was fairly consistent with the value estimated by the new estimation technology. The system has high maneuverability and high potential for future development and application.
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