圖書典藏及影音數位平台

近年來高屏溪流域由於氣候變遷、地震及颱風豪雨，導致山坡地產生大量的土石崩塌；一般而言，豪雨屬於天然災害，土石崩落屬於自然現象，而新崩落的土石與河道原有淤積的土砂，經由地表逕流至下游河道，土石所經之處易造成災害，對河川輸砂特性及穩定性亦造成極大影響。 近年本局及縣市政府於高屏溪流域積極辦理疏濬工程（99年疏濬2,527萬方，100年疏濬2,727萬方，101年疏濬1,386萬方，102年疏濬1,134萬方，103年疏濬753萬方，104年疏濬647萬方，105年截至9月底止疏濬405.9萬方），使轄區內之土砂環境有顯著改善災害發生機率。惟疏濬作業及疏濬後之河道演變可能影響防洪安全及自然環境，因此有必要針對高屏溪流域疏濬成效加以分析評估，並檢討各項水理、沖淤變化及防洪安全等，以達到防洪工程減災興利及河床穩定之目標。 爰此，本局為了解於103年至105年高屏溪疏濬成效提出本計畫，並透過各項評估研擬未來3年疏濬計畫。

Large amounts of loose gravel recently impacting the river sediment transport qualities and stability of the Gaoping River Basin have been produced by the effects of earthquakes and typhoon-related flooding. River sediment erosion and deposition in the Gaoping River Basin have already become key factors in maintaining river stability and flood control and safety. Because sediment data is an important reference basis for examining changes in riverbed sedimentation, river management, dredging operations, and because the subsequent changes to the riverbed may impact flood safety and the natural environment, analysis and evaluation of dredging conducted in the Gaoping River Basin is necessary. Water management, sediment changes, and flood prevention and control should be reviewed, with dredging countermeasures provided for relevant authorities for reference to achieve the objectives of effective flood-prevention engineering and riverbed stability. Furthermore, as the significant accumulation of soil and rock has altered the sediment-transportation conditions of the river, relevant tests should be conducted on the current state of the river to understand the river characteristics and changes in sediment transportation, and subsequently determining the changing trends to benefit future planning and assessment of overall river management. This project proposes standard operating procedures (SOP) for dredging operations. First, when the range of the river is wide, basic data collection and analysis should be used to determine dredging sections. Basic data analysis should include changes in the river sediment over the years, changes in the flow path and sections that have been dredged through the years and vulnerable sections. These data are used in coordination with on-site investigations to form an initial decision on the sections to be dredged. Furthermore, the current flood capacity capabilities of the river and long-term sediment changes should be analyzed, with sections possessing insufficient flood capacity and those exhibiting deposition trends listed as primary dredging sections. The accumulation of deposition leads to redirections of the river flow toward embankments, which often causes damage. These sections are defined as primary dredging sections. Although the dike structures are complete and possess sufficient flood-channeling capacity, deposition has significantly increased the water level, causing a decline in the flood-channeling capacity. These sections may be suitable for drudging. River sections exhibiting declines in river elevation and erosion are not recommended for dredging. After the dredging sections are determined, dredging efficacy evaluation is accomplished through a 2D water-management sediment-transportation model simulating differences in the river channel and back-silting before and after dredging is conducted. The amount of annual sediment transportation can be used as the basis for estimating the amount of dredging, with evaluation standards, such as the dredging ratio or effectiveness, used to determine optimal dredging cross-sections and elevations. Dredging projects should be continually evaluated based on changes in the river channel. If updated river terrain measurements are available, the effectiveness of the original dredging project should be evaluated and compared with changes in the river channel before and after dredging and the results used to reevaluate the dredging sections. The priority of future dredging projects is as follows: the section upstream of Shuangyuan Bridge, the section upstream of Gaoping Bridge, and the section upstream of the Lilin Bridge for the Gaoping River; the section of Ligang Bridge to Xinwei Bridge for the Laonong River; the confluence of the Qishan and Laonong Rivers to the upstream of the cross section No.8, the section downstream of the Xizhou Bridge, the section of the cross section No.18 to New Chiwei Bridge and the section of Yamay Bridge to the cross section No.48 for the Qishan River; the section downstream of Gaushu Bridge, the section of Gaushu Bridge to Nanhua Bridge, the confluence of the Ailiao and Wuluo Rivers, the section downstream of Sandimen Bridge, and the section of Sandimen Big Bridge to Ailiao Dam for the Ailiao River; the sections upstream and downstream of Guangfu Bridge, and the sections upstream of Koushe Bridge for the Wuluo River.