圖書典藏及影音數位平台

台灣近年受到極端氣候影響，颱洪災害日趨頻繁，為防災應變以及河川治理規劃之需要，水文觀測資料之收集至為重要。台灣因河川條件極為特殊與國外一般大陸型國家迥異，颱洪時期高強度之降雨常夾帶高含砂量之洪水，斷面沖淤變化甚大，流量觀測相當不易。惟國內之流量觀測工作，長久以來仍仰賴傳統之人工觀測方式進行，為一項耗時費力、危險度高、精準度不足之水文觀測工作。環顧國內、外現有先進儀器，尚無適合台灣極端水文以及高含砂量此特殊河川條件下之有效方法與自動化設備，故常僅能以水文模式間接推求，惟颱洪時期難以掌握動床變化以及相關水文與地文因子，而影響推估結果。 由於國內近年IT產業蓬勃發展，相關雷達科技之研究工作亦累積相當多的經驗與能量。因此，新階段應不僅是仰賴國外先進儀器之引入，更應持續深耕適合國內本土特殊條件及狀況之量測科技與方法，突破現階段流量觀測技術瓶頸，發展適用本土河川之科技與設備，進而拓展相關水利產業與國外商品市場，以獲致真正的突破及改善，爰擬本計畫發展適合國內非接觸式之「河川流量雷達自動觀測儀器」。

Heavy precipitation during typhoon season frequently causes floods with high sediment contents in Taiwanese rivers. The rapid cross-sectional erosion and deposition changes in these rivers make it difficult to measure flow rates. Among various river flow rate measurements, traditional manual methods are time-consuming, labor-intensive, highly dangerous, and inaccurate. This 3-year research and development project cooperated with Taiwan-based companies to develop non-contact, radar-based automatic river flow rate measurement instruments suitable for Taiwan to resolve technical bottlenecks in current river flow rate measurements and develop instruments that are suitable for measuring river flow rates in Taiwanese rivers. During the first year (2011) of the study period, data from 25 Taiwanese rivers, administrated by the central government, and their water level and flow gauging stations were collected. These data were investigated to determine principles for selecting demonstration stations. Analyses of the technical aspects and patents related to the research and development of the measurement instruments were completed. Furthermore, a measurement prototype was assembled and tested. The plan for the current year is to complete the assembly of three instruments, including a river surface velocity meter, a river water level meter, and a cross-sectional depth sounder, and to conduct a series of tests regarding the influence of environmental factors in the Water Resources Planning Institute. Analysis results have shown that the surface velocity calculated through the linear prediction method proposed in this project shows a ± 10 % relative error range compared with the moving velocity measured by a cart. In addition, under conditions with less than 200 mm/h of precipitation and less than 8 m/s wind speeds, surface ripples, caused by wind and raindrops, only affected the measurement of the surface velocity meter by 0.45 m/s or less, and the peak Doppler frequencies under the effects of wind and rainfall were mutually exclusive, meaning that the frequency did not change because of mixed effects between wind and rain. For the water level meter, the effect of surface ripples caused by wind on the measurement was within a ± 3 % error range. As for the cross-sectional depth sounder, the measurement with an antenna of 100 MHz, under various sediment concentrations, water electrical conductivities, and types of riverbed materials when applying autocorrelation function analysis, accurately interpreted the positions of water surfaces, bed sediment or particle layers, and cement beds. These measurements had an error range of ± 10 %. The surface velocity meter, when applying a linear prediction method, always approached stable values for the measurement of the steady-flow fixed-and-moving-bed clean water tests and velocity measurements. That is, the flow velocity measurement showed no signs of instability caused by changes in the moving bed. The unsteady-flow moving bed test with added sediment, could be analyzed in stages with steady flows. In addition to conducting tests in the lab, the project performed field tests at Shih-men Canal, Ji-ji Weir, and Fa-zi Creek Bridge. All of the results showed that the error range of the measurements were within ± 10 % for flow rate, and the measurement accuracy was not affected by the flow directions of rivers or bridges. When choosing natural measurement sites for this year, Shi-men Bridge (Chung-san Bridge), located by Yi-lan River in the Lan-yan River Basin, and Wan-li Creek Bridge, located by Wan-li Creek in the Hua-lien River Basin, were designated as the north and the east stations, respectively. According to the results measured at these stations, the instruments, without adjustments to their components, accurately measured flow rate under an error range of ± 10 %. However, the cross-sectional depth sounder cannot be operated without human oversight. Therefore, safety should be reinforced when field measurements are being performed.