圖書典藏及影音數位平台

本計畫主要目的為動床水工試驗探討八掌溪河川外側設置攔砂潛堤用以保護海岸之可行性，並藉試驗分析結果找出最佳攔砂效益之設計方案。其他執行內容尚包括八掌溪河口附近海域海象、漂砂、河道斷面、河口地形及海岸線等資料之蒐集分析等工作，今就各節之內容作精簡之內容摘要如下： 　　第一章中敘述本計畫之研究動機與目的，同時闡明本計畫執行後之預期成果等，第二章則說明本計畫之工作項目，其中除資料蒐集外，最主要之工作項目則為動床水工模型。 　　第三章敘述本計畫所蒐集有關河口及近岸地區之各項水文海象及地形資料，文中綜整出各單位於八掌溪河口附近之風速、雨量、流量、輸砂量、潮汐、潮流及漂砂運動趨勢等資料。另外亦對八掌溪下游段之河口地形及河道斷面進行變遷分析，結果顯示八掌溪河口於兩岸尚未整治前其河口常有改道之現象，且河口灘面面積在2002年前南、北岸灘面面積變化甚大，且有大幅縮減情形，而在2002~2007年間河口南、北灘面面積之變化已大幅減緩，尤其北岸已漸減穩定，而河道斷面之分析中大致發現河口附近之-003~000斷面樁地形，河道深樁有於2005~2009年間有逐漸刷深之現象，而河道兩岸則有侵淤互現情形，但整體而言，河口附近之河道有隨年代增加而逐漸變寬的趨勢。於海岸線變遷分析結果則顯示八掌溪河口至布袋間之海岸線自1976~2007年間接皆呈現侵蝕大於堆積之情形，至2002~2007年間海岸線每年仍後退約有3.2公尺。而八掌溪口南岸至雙春間之地形於1992年前海岸線之前進量尚大於侵蝕量，但1992年後海岸線已轉為侵蝕狀況，至2002~2007年間，其整段海岸線每年平均後退約有4~5公尺左右。 　　第四章則敘述本計畫水工模型試驗之規劃過程、試驗步驟與方法等，總計共進行有無攔砂潛堤、變化潛堤高度與不同設置水深等不同條件共計九個試驗。 　　第五章之主要內容即就本計畫試驗結果進行討論分析，由各試驗結果發現佈設潛沒式欄砂潛堤於河口外側後，皆能有效攔阻河口外流之河川輸砂，且這些堆蓄於潛堤外側之土砂在波浪之作用下皆可被沿岸水流帶往下游側成為額外之沿岸漂砂量，由零米線之分析中可之攔砂潛堤設置後，河口下游側海岸線與未設置攔砂堤比較分析可發現設置後，海岸線皆有前淤之效果，最大可有近40公尺之前淤長度，最小仍有約5公尺之前淤量。在淤砂損失率之分析中可發現設置攔砂潛堤後確實可有效將外流損失之輸砂堆蓄在潛堤內，由無因次分析結果可發現潛堤設置後最少亦可攔下約7%左右之放流砂量，另由何道至河口外側水位分析結果顯示，攔砂潛堤設置後，雖然部分試次有河口抬升之現象，但抬升量甚小，最大抬升量不超過15公分，故各試次之潛堤佈置方式，應不致對八掌溪口之排洪能力造成影響，在綜合海岸線變化量、堤趾淘刷量、淤砂損失率及河道水位抬升等現象之評估後，各項分析結果皆以潛堤高度2.0公尺、設置於離岸水深4.0公尺處會有最佳之防護效果。

The main purpose of this project is to explore the movable bed hydraulic experiment set the bar outside Pachang river sand submerged breakwater to protect the feasibility of the coast and through the experiment results to find the best benefits of the sand bar design, the implementation of the contents of other include Pachang waters near the mouth of walrus, sand transport, river section, estuaries and coastlines and other terrain information analysis and so on, contents of various sections of streamlined content summarized as follows: The first chapter describes the motivation of this plan and purpose, while also addressing the implementation of this project after the expected results. The second chapter of the present plan of work projects, except data collection, the most important item of work was fixed bed hydraulic model. Chapter III of this project is to collect information on estuaries and near-shore areas of the walrus hydrology and topography data, the paper integrated whole out of units near the mouth of the Pachang wind speed, rainfall, flow, sediment yield, tidal, current and drift sand movement trend information. Another paragraph also Pachang River estuary to changes in terrain and the river section analysis showed that Pachang estuary at its mouth before the two sides have not yet rectification phenomenon often diverted, and the estuary beach area of the South before 2002, North Shore Beach area of change in a very large, and there is a substantial reduction in cases, while in 2002 and 2007, River South, the North Beach area of the change has been a significant reduction, especially north has been decreasing stability, the channel section of the analysis generally found near the mouth of -003 ~ 000 section pile topography, river deep pile there between 2005 and 2009, there have been deep brush phenomenon, but both sides have invaded river silt each other is the case, but on the whole, near the mouth of the river has gradually changed with increasing age of wide trend. Changes in shoreline analysis showed Pachang River to the coastline between bag from 1976 to 2007 are presented indirectly, greater than the accumulation of cases erosion to the coastline between 2002 and 2007, about 3.2 meters back each year. The Pachang mouth to the south bank of the terrain between two-spring 1992 years ago, is still greater than the amount of coastline erosion progress, but the coastline has changed since 1992 Erosion, 2002 to 2007, its entire coastline, the average annual retreat about 4 ~ 5 meters. The fourth chapter describes the project planning process of hydraulic model tests, test steps and methods, a total of silt were carried out with or without submerged breakwater, changes in submerged breakwater height and depth of different settings such as a total of nine different test conditions. Chapter V of the main content of the test results on this project, discussion and analysis, mobile bed experiments in order to change through different submerged breakwater height, set the depth of different combinations of test, measurement, topography, river mouth water level, scour and embankment toe Zero rice noodle change analysis, we found various combinations of the coastline before the deposition, on the lower reaches of coastal drift sand added are better than not set a submerged breakwater to have a better effect, and the mouth of the CASE will not affect the existing drainage capacity, then The comparison analysis found that both the sand and then releasing the first wave or to discharge the same time, when sand wave after wave of results were mainly focused on submerged breakwater height of 2.0 meters, set in the offshore water depth of 4.0 meters will be the best protective effect