圖書典藏及影音數位平台

高屏溪流域高屏溪流域約計來回560公里大斷面測量、高屏溪重要橋梁及固床工斷面(約計151處)、東港溪及支流萬安溪及牛角灣溪河道大斷面測量(約計來回130公里)。

I. Overview A. The Origin and Objective of Project River Cross-section Survey data provided basic surveying reference for river course alert level formulation, flood area hydraulic routing, sediment transport, design and planning of flood prevention construction, river management, river-crossing structure, ground sill safety investigation and riverbed sedimentation analysis. Furthermore, River Cross-section survey serves as an essential method for reviewing the alert level and management of rivers administered by central government. Therefore, this paper followed the Project of Water Resource Agency-“Cross-section River Surveying for Management and Alert Level Reviewing of Year 2006”, implementing Cross-section Surveying observation on yearly base in order to provide a reference for river management and review of river alert level. B. Work Items and Contents i. In the field Investigation ii. 74 locations of Cross-section Surveying at Gaoping River iii. 152 locations of Cross-section Surveying at Qishan River iv. 159 locations of Cross-section Surveying at Laonong River v. 45 locations of Cross-section Surveying at Ailiao River vi. 118 locations of Cross-section Surveying at Tributary of Jhuokou River, Northen Ailiao River and Southen Ailiao River. vii. 74 locations of Cross-section Surveying at Tributary of Meinong River viii. 138 locations of Cross-section Surveying at Donggang River, Tributary of Wanan River and Niujiowan River. ix. 151 locations of Cross-section Surveying of crucial bridge and ground sill at Gaoping River basin x. 57 points of Leveling including 20 points of airborne LiDAR surveying point. xi. 57 points of cross-section stake GPS surveying and 20 points of airborne LiDAR surveying point. xii. Office work included data organizing, investigation result analyzing and report writing. Re-calculation on the condition of riverbed sedimentation using the current circumstances of surveying data and Cross-section data over the years. Submitted 25 copies of surveying project outcome report, one A3 on-site surveying result atlas (with disk). C. Project Period From March 14th, 2016 to December 15th, 2016 II. Surveying Method and Process A. Control Systems i. Plane coordinate system adopted the Taiwan region TM2 TWD-97[2010] system, TM2 TWD-97 system, TM2 TWD-67 system and cadastral coordinate system by Ministry of Interior. ii. Vertical system adopted “2015 Taiwan First Order Levelling Network Levelling Result” released by Ministry of Interior in 2016. B. Horizontal Control System The Horizontal Control in this report applied TWD-97[2010] coordination system in total of 34 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 0.04m+8ppmxL(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 37 points and airborne LiDAR surveying points of 20 points. C. 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 13 measured points were qualified with the standard of 7mm√K, and these points were then drawn to cross sectional stake at site as the reference for the vertical control. D. 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. E. River Cross-section Surveying 151 locations at crucial bridge and ground sill Cross-section, 760 locations at river Cross-section and 911 locations at surveyed river cross section. F. Airborne LiDAR Surveying This project placed 20 airborne LiDAR surveying points in total and took five flights to finish the aerial photography. Flight height at 2000m to 2200m and had flown 670 kilometers. The rate of front-back overlap was 80%, while left-right was 30% and LiDAR left-right overlap by 40%. With Ground resolution GSD of 20cm, LiDAR point cloud density 1 points per square meters. Through categorization, editing and inspection, ground point data and outcome were saved in plain text, figures in meters. Moreover, data columns includes X,Y,Z three-dimensional coordinates. III. Riverbed Sedimentation Comparative Analysis on Yearly Basis A. Basic Data Collection This report collected and reorganized all river cross-section surveying data conducted by each bureau unit to provide a comparison reference for this analysis. B. 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. C. Change of Riverbed Gradient Distinguished each river section with different slope according to the calculation result of average riverbed height and longitudinal section or construction within the river, and computed both average slope and average slope on yearly base for further application. D. Change of River Sedimentation Elevation In line with the data collection from 1975 to the surveying result of this report, the yearly average riverbed height and data from 2016 of main and tributary stream of Gaoping River was deliberated. Furthermore, the sedimentation from each cross section of each year was also analyzed to have a better understanding on all main and tributary region’s both river section and cross section change regarding riverbed sedimentation. The result contributed to the planning and review of river course management and river construction management. E. Change of River Course Channel To discover the process of main channel change of the main and tributary stream in this river basin, cross section data from 2008, 2010, 2012, 2013 and 2016 were collected and analyzed so as to offer a resource base for Flood Prevention Project and management. F. 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. G. Result and Review of Sedimentation Analysis The comparison of the average riverbed height of cross section in the past and this year may exist a slight deviation with the actual change; however, this result could still provide foundation for future management plans and dredging and stone filling plan. Similarly, this can also be a reference for project engineers. H. Sedimentation Comparative Analysis of Gaoping River Bridge and Ground Sill Cross Section on Yearly Base There were 51 locations investigated quantity at Gaoping river regarding to the Gaoping River Bridge and Ground Sill Cross Section observation points, 37 at Tributary of Laonong River, Tributary of Qishan River and Tributary of Ailiao River, total of 151 locations. Bridge and Ground Sill data of each Cross Section from 2009, 2010, 2011, 2012, 2013, 2014 and 2016, 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 (1999 through 2016) was further analyzed. The above offered resource base for bridge or related supervising bureau of maintenance and management. IV. Conclusion and Suggestion This report collected comprehensive information from each year, and investigated in detail of all main and tributary stream of the river basin, including bridges, ground sill cross section average riverbed height, slope, scour depth, sedimentation volume and average sedimentation depth at each river section. Despite lacking few data source, the examination result of this report is able to provide a reference foundation for the planning and management, dredging project, sediment transport research, engineering use gravel excavation field and river management in the future. Airborne LiDAR scanning surveying can quickly obtain the cross section data in the same period and acquire laser scanning point cloud data of whole area. Density of point clouds can deliver complete information and add extra cross section data when needed. The point cloud can be further conducted into DEM result for the Organizer providing basic data to analyze river. River Cross-section Surveying is recommended to be implemented every two to three year in order to set up a long term riverbed change data base. It is also suggested to track the scour depth of whole area and river section (or cross section) with relatively larger change of sedimentation within the period of dry season to offer a reference base for the future conduc.