礫石型土石流之觸發降雨特性與監測訊號判釋

降雨引致礫石型土石流常對下游保全對象造成嚴重的土砂危害，故建立現地監測系統及進行降雨預警，有助於精進坡地防災科技及降低保全對象之災害損失。本文綜整2007-2019年間於苗栗火炎山一號坑現地監測的訊號特性，並建立土石流運移距離與有效累積降雨之關係。礫石型土石流常呈陣流方式，每次陣流的延時約2-3分鐘，尖峰地表振幅值約0.1-0.2 mm/s，其地聲頻率則介於15至45 Hz間。地表逕流及高含砂水流之地聲頻率範圍則介於50至70 Hz間，且延時大於5分鐘。火炎山現地量得之背景噪音如風聲、雷聲、地震等，可綜整其振幅、頻率及延時三個參數加以判釋。

關鍵字

礫石型土石流；現地監測；降雨預警；地聲

並列摘要

Rainfall-induced gravelly debris flows can cause devastating disasters downstream. Both onsite monitoring and rainfall warning systems are effective countermeasures to mitigate damages. In this study, the onsite signals collected at the Houyenshan monitoring station from 2007 to 2019 were analyzed, and the relationship between the effective accumulated rainfall and the traveling distance of gravelly debris flows was established. Gravelly debris flows occurred as pulse flows for 2-3 min, and the peak frequencies were recorded within a range of 15-45 Hz. Runoff and high concentration flow were recorded at a higher frequency of 50-70 Hz and lasted for longer than 5 min. The signals generated by background noises such as wind, rock falls, and earthquakes could be identified based on their amplitudes, frequency, and duration.

並列關鍵字

Gravelly debris flows ； onsite monitoring ； rainfall threshold ； geophone

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