2017-05-042024-05-17https://scholars.lib.ntu.edu.tw/handle/123456789/681625摘要：烏來地區104年蘇迪勒颱風在災前新店溪上游國有林之崩塌面積為22.35公頃，災後經林務局農林航空測量所判讀，崩塌地面積增加為65.48公頃，絕大部分之崩塌地坡度陡峻無道路可達，而土砂勢必向河道遞移且可能改變水流衝擊方向，影響河道通洪及河防構造物安全，而桂山壩位處烏來老街下游，壩體本身已攔蓄砂土，再加上崩塌部分經河流帶至桂山壩附近，使壩體之淤積量日益嚴重，雖民國99年、100年分別修定「桂山壩水庫水門操作規定」及「桂山壩水庫運用要點」，但每年颱洪期間沖刷至壩前之砂土，對於桂山壩水庫顯然已降低原有水庫之功能效率，另於河道部分也因淤積嚴重提升洪氾之風險。 本計畫目的係如何利用水力排砂以減緩水庫囚砂率，並評估排洪時配合閘門操作將泥砂排放至下游之效益，以減少庫內及南勢溪渠底清淤疏濬量，維持水庫沿岸環境景觀，使地區風貌重塑，恢復往日湖光山色景緻，達成增進休閒遊憩及環境營造之目標。本計畫工作事項繁雜，不過大致可區分為四個主要項目，分別為：基本資料蒐集、現場量測作業、模式發展運用以及對策研擬分析等。 基本資料蒐集部分除一般的河川情勢作為分析基礎外，最主要工作項目為流域年產砂之估算與輸砂量的推估，將為研究區域長期沖淤情勢的評估基礎；現場測量部分，除基本地形測量及河床質調查、及水位流量泥砂站的資訊都將作為模式率定驗證使用。本計畫最主要的部分則是水理輸砂模式的發展運用，一維模式考量需模擬桂山壩的影響，因此本工作團隊預計採對跨河構造物處理較佳的HEC-RAS作為模擬工具，探討長期沖淤趨勢跟通洪能力。HEC-RAS之模擬結果將提供作為二維模式作為分析條件。二維模式則採用SRH-2D，其相較於目前常用之二維水理輸砂模式，能處理大部分二維水理輸砂的條件，較無發散不收斂的問題，結果相對可靠，二維模式將作為本計畫評估各項排洪、排砂問題、策略之骨幹，過去本團隊運用此模式於石岡壩、後村堰之各項評估，成效良好，能高度掌握各種現象。另外由於桂山壩之排砂道固定輪閘門:為寬5.38x高4.15公尺浸沒於水下頂標高為102.0公尺處，致使部分排砂操作需考量三維水理泥砂之特性，因此本團隊也將運用過去發展於石門水庫之模式用以評估相關議題。 在相關水理輸砂模式的基礎上，本工作團隊將協助相關烏來河段河道穩定方案、桂山壩排砂操作及壩體改善、以及雨量警戒之評估。河道穩定方案之疏濬計畫部分主要為清淤河段、長寬比建議、疏濬深槽流路位置等，以及相對應之疏濬效益評估。此外也將協助評估目前計畫中河防方案對於河道變遷之影響。桂山壩排砂操作建議包過排砂操作的時間點及操作方式外，也將協助評估溢流堰高程改變是否能改善排砂，或是壩體移除之可行性評估。最後也將協助設定警戒雨量，運用於防災與水庫操作面向作為主辦機關操作參考。 本計畫第一年度完成主要工作內容包括：1. 基本資料蒐集整理及現場量測作業、2.評估如何監控桂山壩上游泥砂來源及推估水文、泥砂入流量、3.水理、輸砂與排砂分析、4.疏濬方案及效益評估、5.教育訓練與技術轉移。<br> Abstract: After Typhoon Soudelor hit Taiwan in 2015, the landslide area have been increased from 22.35 Ha to 65.48 Ha in the upstream of Xindian River in Wu-Lai district, which were recognized by Forestry Bureau Aerial Survey Office in Taiwan. The sediment would transport to the river and change the direction of water impact, which could results in the safety concerns of the flood capacity and flood-control structure. Although the “Reservoir Water Gate Operation of Guishan Dam” and “Guishan dam reservoir application Guidelines” were revised in 2010 and 2011, respectively. The sediment deposition in the downstream of Wu-Lai old street has been increased during the Typhoon season, and it reduced the functional efficiency of Guishan Dam reservoir and raise the flood risk due to the serious sediment deposition of the river part. The aim of this project is to analyze how the hydraulic flushing decreases the trap efficiency of the reservoir and evaluate the effectiveness that sediment was desilted by the gate operation during the drainage period. It could reduce the dredging amount in the reservoir and drainage bottom of Nanshi River, which could maintain the environmental landscape along the river and regain the former scenery, attaining the goals of the river environment leisure and recreation. The work items in this project are multifarious and we classified them in to 4 main parts, including information collection, field measurement, model development and countermeasures development. In addition to the general situation of the river basin as the basis for the analysis at basic data collection part, the main project is to estimate the annual sediment yield and discharge in the basin. It would become the evaluation basis. In the field measurement, the basic topographic and gravel-bed River material survey, as well as information of water level and sediment station will be used as a model calibration verification. The most important part in development of flow hydraulics and sediment transport modeling ,considering at the influence by Guishan Dam in One-dimensional model, our team adopted the HEC-RAS as the tool which has a better simulation result in cross-rive structure and explore long-term erosion sedimentation trends and flood drainage capacity. The HEC-RAS simulation results will be provided as the analysis conditions to the SRH2D, a two-dimensional model, which could deal with most conditions in 2D sediment transport modeling and without divergent problems. With this 2D model as the main tool , the desilting and drainage problems once be used in Shigang Dam and Hou-Cun Weir assessment and achieve good results. In addition to the fixed wheel gate of drainage tunnel of Guishan Dam which is 5.38m wide and 4.15m high are submerged at 102.0m underwater top elevation, results in some desilting parts should consider the 3D hydraulics and sediment characteristic. Our team would evaluate with our model once developed in Shimen Reservoir. On the foundation of hydraulics and sediment model, our team will assist the stabilization project of Wulai River section, desilting operation and improvement of Guishan Dam and rainfall warning evaluation. The main dredging part in the river stabilization scheme is dredging river section, giving the suggestion of the aspect ratio and the site of dredging flow path in deep groove. Besides the dredging effectiveness evaluation, our team would assist in assessing the impact from the method in this project. The suggestion includes dredging time operation and methods, also evaluate whether the weir elevation change would improve dredging or not, and the feasibility assessment of dam removal. Moreover, we would assist the rainfall warning setting, which could be used in disaster reduction and reservoir operation also as the reference for organizers.南勢溪桂山壩河道變遷水力排砂水理輸砂模式Nanshi RiverGuishan DamGeomorphologyRiver DredgingHydraulics and Sediment Transport Model