火炎山土石流之流動型態與地聲特性分析

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

羅浮合流部落土石流之致災機制分析與數值模擬

Typhoon Soudelor brought abundant rainfall in northern Taiwan on August 8, 2015. The rainfall caused a shallow landslide which was transformed instantly into a debris flow disaster in the Heliu catchment. We integrate remote sensing, rainfall analysis, micro-topography interpretation, lineament of tree fall, field investigation, a UAV survey, and RAMMS simulation to explore the failure mechanism and flow dynamics of this rainfall-induced debris flow. The high resolution shading relief map depicts the landforms of both the old deep-seated landslide and the ancient debris-flow fan. In this study, different numerical scenarios are performed by RAMMS to analyze the possible influence area via adopting the back-analysis approach. In comparison with the post-disaster landform model, the bestfit parameters for Heliu debris flow were also obtained. In addition, verification of dynamic images demonstrates that the maximum flow velocities for the event and deposition height on the debris-flow fan are about 14.3 m/s and 1-5 m, respectively.桃園市復興區羅浮里合流部落集水區，於 2015 年 8 月 8 日蘇迪勒颱風期間因強降雨誘發邊坡岩屑 崩滑形成土石流，造成下游 15 戶民宅遭到破壞或淤埋。本研究以遙測影像、UAV 攝影測量、致災雨量分析、 微地形判釋、崩塌地倒樹線型、現地勘查及數值模擬探討土石流致災機制與災害成因。合流集水區上游為一 舊岩體滑動區，且存在古土石流堆積扇地貌，本案例災害主要受降雨形成之地表逕流沖刷，導致坡腳失穩之 後退式岩屑崩滑。本文採 RAMMS 數值模擬以參數逆推法探尋土石流發生之可能情境，並與災後地貌進行驗 證。災害動態影片分析與數值模擬驗證則顯示合流部落土石流之流動段流速約 14.3 m/s，受災堆積段之溢淹深 度則介於 1-5 m