本研究於苗栗縣三義鄉火炎山一號坑進行土石流現地監測，透過影像畫面及地聲儀監測土石流的流動歷程，分析土石流的前端速度及體積，及探討土石流產生堵塞以及河道改道等原因。本研究分析2016年至2019年間二十四次土石流事件的雨量相關特性，除前期累積雨量外，後續降雨、連續土石流事件及河道改道皆是影響土石流移動距離之重要因子。以現地攝影設備配合地聲儀監測並記錄地表逕流、土石流以及高含砂水流所產生的地表震動訊號，探討其不同的地聲訊號與頻率特性，並得知地表逕流事件的頻譜特性為50至 60 Hz之間，落石事件的頻譜特性約為40 Hz，土石流事件的頻譜特性為20至40 Hz之間，高含砂水流事件的頻譜特性則與地表逕流的結果相同。;This field study of rainfall-induced debris flows at the Houyenshan of San Yi county, Miaoli, Taiwan was performed by analyzing the recorded images of time-lapse photography cameras, the geophone signals and the rainfall data. The rainfall characteristics of the 24 debris-flow events from 2016 to 2019 show that the previous accumulated rainfall, subsequent rainfall, previous debris-flow events and channel avulsion are all important factors affecting the runout distance of the debris flow. The on-site photography equipment and geophone instruments are combined to categorize the geophone patterns generated by surface runoff, debris flows and debris floods. The peak frequencies of surface runoff events and debris floods are between 50 and 60 Hz, while the main vibration frequencies of rockfall events are about 40 Hz. On the other hand, the peak frequencies of debris flow events are between 20 and 40 Hz.
