圖書典藏及影音數位平台

大斷面測量為河道河川警戒水位之制定、洪水淹水範圍之水理演算、輸砂、河防構造物之規劃設計及河川管理、跨河建造物及固床工之安全調查、河床沖淤分析等均需依此基本資料，水利署為檢討中央管河川警戒水位及河川治理所需，爰此，本觀測計畫係遵照水利署「95年度河川治理及警戒水位檢討所需河道斷面測量計畫」每年辦理大斷面觀測工作，俾供河川治理及檢討警戒水位之參考。

I. Overview 1.1 The Origin and Objective of Project The project is " The observation and investigation of cross sections in the valley of Donggang River and Upstream Reach of Gaoping River " with a total area of about 313 sections including Loa-Nong River, Chi-Shan River, Ai-Liao SouthRiver, Ai-Liao North River, Donggang River, Wanan River and Niujiowan River. River Basin important bridges and BedGroungsill Works section of 120 cross-section measurement. 1.2 Detailed survey work includes: A. Site survey. B. Section pile survey. C. Section pile buried, the implementation of 60, as detailed in section 4-4 and Appendix I. D. Level check, the use of direct level survey, a total of 11 first-class level control points, as detailed in Section 4-3. E. Control point check, GPS static measurement measurements, a total of 12 satellite control points were checked, of which 1 failed to check the actual reference to 11 satellite control points, as detailed in Section 4-2. F. Section pile coordinate survey, the actual application of section 60 piles, as detailed in Section 4-5. G. Cross-section pile level survey, the actual distance level survey is about 77 kilometers, as detailed in Section 4-5. H. Cross-section survey, measuring a total of 433 river sections. As detailed in Section 4-6. I. Survey results and report compilation. 1.3 Project Period From April 1th, 2019 to December 15, 2019 II. Surveying Method and Process 2.1 Control Systems A. Plane coordinate system adopted the Taiwan region TM2 TWD-97[2010] system. B. Vertical system adopted “2015 Taiwan First Order Levelling Network Levelling Result” released by Ministry of the Interior TWVD-2001. 2.2 Horizontal Control System The Horizontal Control in this report applied TWD-97[2010] coordination system in total of 14 points of satellite control point to the surveying method as a reference survey lead, and then examine whether the satellite control point is in coordinate with the standard 0.02m+5ppmxL(L refers to side length, in meters). Applied with static surveying, the satellite control point which meets the standard was drawn to the cross sectional stake in the site. Accumulated surveyed cross sectional stake 8 points. 2.3 Vertical Control System The Vertical Control in this report implemented “2015 Taiwan First Order Levelling Network Levelling Result” released by Ministry of Interior in 2016. Total of 8 measured points were qualified with the standard of 7√K, and these points were then drawn to cross sectional stake at site as the reference for the vertical control. 2.4 Cross Sectional Stake Surveying Cross sectional stake GPS surveying with given value of qualified satellite control point adopted Rapid Static to implement GPS positioning surveying. The elevation of cross sectional stake was measured with electronic level using bar code level staff automatically recorded when conducting vertical survey. The collected vertical survey data was confirmed in comply with accuracy standard of 12mm√K after adjustment computation. 2.5 River Cross-section Surveying 120 locations at crucial bridge and ground sill Cross-section, 433 locations at river Cross-section and 313 locations at surveyed river cross section. III. Riverbed Sedimentation Comparative Analysis on Yearly Basis 3.1 Average Riverbed Height Refer to the river cross section data, and with the analyzed actual data of designated levee alignment or flood protection construction scope on site and low water route, the average riverbed height at each cross section was calculated. The result provided a comparison foundation to the river longitudinal slope and sedimentation analysis. 3.2 Riverbed Sedimentation Comparative Analysis on Yearly Basis The comparison analysis of riverbed sedimentation of this paper was based on merely the actual surveyed data from this project, including river cross section and average riverbed height of main and tributary stream in this river basin. This was because part of the analysis results had already been finished over the years. The analyzed circumstances of all river cross section each year offered awareness regarding depth change at each section and moreover, to calculate the river area, sedimentation depth and sedimentation volume by the information of average riverbed height, distance to river center and the width of cross section. Additionally, average riverbed height longitude drawing of full project river course was conducted in order to provide a database for the research in sedimentation transport and management 3.3 Result and Review of Sedimentation Analysis The depth of the scouring and silting, etc., the Laonong and Chi-Shan River is seeing each other,most of them are scouring,and there are no extreme changes in the cross sections ,the river channel is still stable .The Ai-Liao South and Ai-Liao North River are silting all the section over the years, but most section scouring lightly in recent years, the river channel is still stable.The upper and lower sections of Donggang River is scouring ,and the middle section is silting.However the scouring and silting is not large, and it does not affect the normal flood discharge and sediment transport function of the river .The upstream of Wanan and Niujiowan River are scouring,and downstreams are scouring and silting.All the section s are scouring over the years, and all the sediment is moving downstream. It still does not affect the normal flood discharge and sediment transport of the river, however, the downward movement of earth and rock should be frequently observed to avoid affecting downstream flood control and river crossing structures. IV. Sedimentation Comparative Analysis of Gaoping River Bridge and Ground Sill Cross Section on Yearly Base 4.1 The surveying result There were 20 locations investigated quantity at Gaoping river regarding to the Gaoping River Bridge and Ground Sill Cross Section observation points, andthen Tributary of Laonong River, Chi-Shan River, Ai-Liao River, River Basin important bridges and BedGroungsill Works section total of 120 locations. 4.2 Basic Data Collecti Bridge and Ground Sill data of each Cross Section from 2009, 2010, 2011, 2012, 2013, 2014, 2016, 2017, 2018and 2019, are collected to compute and compare average riverbed change each year. The change of sedimentation depth and riverbed sedimentation between the two ends of year range (2009 through 2019) was further analyzed. The above offered resource base for bridge or related supervising bureau of maintenance and management. 4.3 Change of Sedimentation Comparative Analysis of important Bridge and Ground Sill Cross Section on Yearly Base After collecting the cross-section data of Gaoping main river, tributary rivers, bridges, solid bed workers, etc., and the large-section results of the survey, the average riverbed height of each bridge section and solid-bed section is analyzed and compared. The depth of the scouring and silting, etc., the mainstream Gaoping River is seeing each other, the scouring and silting is not large, and it does not affect the normal flood discharge and sediment transport function of the river , and the river is still stable; There is no large scouring and silting under the Xinwei Bridge in Laonong River, or because of the wide width of the river. Construction of the project or river channel finishing, there is no extreme change in the upper and lower sections of the remaining bridges, and the river channel is still stable ; Chi-Shan River has its own bridges under the Chi-Shan Bridge. The bridges below the Chi-Shan Bridge are scouring and silting. The cross-sections of the bridges are still stable. However, the sections from the Yuemei Bridge to the Xiaolin Bridge vary greatly, and they are mostly washed. The section of the Changlang suspension bridge is silted, and there are no extreme changes in the upper and lower sections of the remaining bridges. The river channel is still stable ; the entire section of the Ai-Liao River has been eroded and silted, and there is no obvious change in each section ; the middle reaches of Wuluo River were gradually deposited, and the other sections showed no significant changes. V. Conclusion and Suggestion Cross-section measurements for the river warning river water level formulation, flooding flood calculation, sand, river structure design and planning of river management, river construction and solid bed safety, river bed scouring analysis Etc. Based on this basic information, the Water Resources Department is to review the water requirements of central river control and river control so as to provide references for river control and review of warning water levels.