Debris-Flow Monitoring System with Acoustic Sensing and Digital Image Processing

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The purpose of this research is to develop a new monitoring system to prevent and to mitigate debris-flow hazards. The results of this research during three years are as follows:1. An acoustic sensor with a microphone inside a pipe set underground has a high signal-to-noise ratio compared with other ground vibration sensors, seismometer, piezoelectric sensor, or moving-coil sensor. An improved acoustic sensor having a microphone immersed in oil inside the pipe shows a possibility of twice detection range.2. A digital image processing based on video images of debris flow can make a proximity-detection by utilizing a detection algorithm of MPEG motion vectors. Another digital image processing methods such as computer-based spatial filtering velocimetry, spatio-temporal derivative space method, or cross-correlation method can estimate surface velocity of debris flow.3. A combination system of an acoustic sensor and an image-processing method may have a good performance of debris-flow monitoring. The acoustic sensor may compensate the image processing under a bad weather condition of deep fog or heavy rain : on the other hand, the image-processing method makes clear the real image of debris flow, which the acoustic sensor can't observe. Unfortunately, the feasibility test of this combination system has not been confirmed because debris flows have not occurred in a test torrent.4. A workshop on debris flow monitoring was held at the Swiss National Hydrological and Geological Survey in Ittigen-Bern, Switzerland, on 5-6 November 2001 by partial supporting of this found. The results of this research were presented in the workshop and took a good evaluation in viewing future monitoring of debris flow.