火炎山土石流之流動型態與地聲特性分析

The Flow Patterns and Geophone Characteristics of Debris Flows at Houyenshan, Miaoli, Taiwan

周憲德(Hsien-Ter Chou[) ； 楊祥霖(Hing-Lin Yang) ； 李璟芳(Ching-Fang Lee) ； 黃郅軒(Chih-Hsuan Huang)

《中華水土保持學報》 46卷2期 (2015/06) Pp. 71-78

https://doi.org/10.29417/JCSWC.201506_46(2).0001

摘要

山區蝕溝驟發性的礫石型土石流因其流速快、堆積深度大且巨礫集中於波前，對於下游經常造成嚴重土砂危害。本文主要探討苗栗縣三義火炎山一號坑2013/5/22降雨引起之火炎山土石流事件，依現場地聲及次聲監測系統配合影像與雨量觀測資料，將該集水區內的土石流分為黏性土石流與稀性水石流兩類，並進一步分析土石流的流動型態及地聲訊號特性。另一方面依事件前後以光達掃瞄產製的數值地形，判釋災後溝渠內的土石流波峰及側積堤特徵。由頻譜分析結果得知地表逕流與土石流訊號分析，得知地聲訊號強度與土石流規模具正相關，且地表逕流頻譜分佈的主頻較土石流的主頻略高。本次事件的地表逕流頻譜特性介於30-45Hz；土石流頻譜特性則在10-32Hz。最後藉由地聲訊號之振動強度與土石流流量、流深所建立之關係，可研判火炎山土石流流動類型與規模判斷準則，並提供未來預警系統建置之參考。

關鍵字

土石流 ； 火炎山 ； 降雨 ； 側積堤 ； 地聲訊號

並列摘要

Debris flows running from mountainous gullies are often with destructive high velocities, large buried depth and great number of coarse particles and may cause serious slope disasters. By analyzing the geophone and acoustic signals, real-time CCD images and the rainfall data in the gully 1 catchment at Houyenshan, Miaoli, one can classify the debris flow into two different flow patterns such as viscous debris flows and diluted debris flows based on their flow characteristics. This paper studies the rainfall-induced debris-flow event on May 22, 2013. The multi-temporal digital elevation model produced by airborne and terrestrial LiDAR was also adopted to map the location of wave surge and nature levees after debris flow events. Frequency distribution of surface runoff is higher than that of debris-flow events. The frequency spectrums of surface runoffs are 30 to 45Hz, while the frequency spectrum of debris flows are 10 to 32Hz. Through verifying both geophone and acoustic monitoring systems by the CCD images, it can be concluded that the signals of geophone sensors, by frequency spectrum analysis and judging signal duration and their amplitudes can be regarded as the basis of debris-flow warning system.

並列關鍵字

Debris flow ； Houyenshan ； rainfall ； natural levées ； geophone signals