A debris flow triggered by 575 mm of rainfall over a 24-h period during Typhoon Soulik on July 13,2013 buried debris-flow monitoring equipment in the gully 1 catchment at Houyenshan, Miaoli, Taiwan. The buried depth and covered area exceeded 2.5 m and 100 m2, respectively. Portable magnetometers were later deployed to detect a buried iron instrument case, and manual excavation was conducted from February 11 to April 6, 2015. The geomagnetic
characteristics of the hot spots for the buried equipment exhibited both a high geomagnetic gradient and a null
value on the magnetic anomaly contour map. The particle size distribution in the excavated pit indicated that the gravelly debris flows were both matrix-supported and muddy during the deposition process.
Key Words: portable magnetometer, magnetic anomaly, subsurface prospecting, debris flow