台灣位處於太平洋火環帶附近，因此造山運動發達、地質較為破碎。近年來由於全球氣候變遷，長延時、強降雨的降雨型態愈發頻繁，其所造成的土砂災害也更是嚴重，在山區中土砂的運輸對於坡地的水土保持影響甚大，尤其底床載的運輸對於河床地形的演變更是劇烈。
在早期，政府對於底床載輸砂量的推估多是採取於降雨事件中直接量測水樣並加以分析或者是利用經驗公式推估，然而於降雨事件中直接量測水樣的方法有安全性上的疑慮並且受到採樣器的容量限制，而依照經驗公式推估的方法也會因沒有實際土砂濃度的影響而有錯估的情形。因此如日本管式水聲計、地聲計、地震波等底床載的間接量測方法便愈顯重要，本研究將會著重於日本管式水聲計的理論研究、實驗率定方法以及藉由實際降雨事件的量測結果推估底床載輸砂量。
由於台灣較高比例的山區地形，造成了大部分的河流流況短小且湍急，高強度的降雨所造成的湍急河水對於人為的採樣更是一大威脅，因此利用間接的方法量測底床載輸砂量是必要的。本研究區域為高雄市甲仙區的油礦溪，油礦溪為旗山溪支流，莫拉克颱風之後造成了本區域大量的崩塌產生，而崩塌的土砂為河道輸砂的主要來源，因此本區域的輸砂量是極為可觀的。本研究於2016年底裝設了日本管式水聲計，並且記錄了隔年6月1日及6月13日開始之梅雨事件以及7月29日和7月30日之尼莎、海棠颱風事件。

Taiwan is located in the Pacific Rim Seismic Belt, so typhoons and heavy torrential hit Taiwan every year. Along with the climate changes, the amount of rainfall increase and duration of rainfall also extend, which makes the sediment-related disaster more serious. Sediment transport is highly relative to water and soil conservation in the mountain area. Especially, bed-load monitoring plays an important role in riverbed variation.
In the past, the government usually used field investigation to obtain bed-load transport or calculated by empirical equations. However, it has some disadvantages like high risk in high flow and the empirical equations calculation are not match to the exact bed-load transport. Therefore, indirect methods like the acoustic method for the continuous monitor will become more important in the future. There are kinds of methodologies on indirect bed-load monitoring like hydrophone, geophone or seismic wave. This paper will focus on the theory of hydrophone and how it will be applied on site to identify the feasibility in Taiwan. What’s more, the detecting rate and difference of volume compared with different methods are also inferred.
Due to the high proportion of land on mountain area, most of the rivers in Taiwan are short and steep. The stormy weather and turbulent river also make it more difficult to evaluate the sediment transport during typhoon seasons. The research of indirect method on bed-load monitoring is necessary. The study area of this research is located at Yokaung River a mountain stream in Jiasian District, Kaohsiung city. The instrument of pipe hydrophone had been installed in 2016 and it had recorded two torrential rainfall events (June 1st and June 13th) and two typhoon events (July 29th and July 30th) in 2017.

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