Table 1.

Debris-flow parameters and sensors employed for their measurement.

Parameter	Sensor employed for the measurement
Peak flow depth	Direct post-event observation through theodolite or GPS, wire sensors, photocells, ultrasonic sensors
Flow depth as function of time	Ultrasonic sensors, radar sensors
Ground vibration	Seismometer or geophones (velocimeters, accelerometers)
Underground sound	Microphones
Mean flow velocity	Ultrasonic sensors, geophones
Surface velocity	Electromagnetic doppler speedometers, video recordings, speed sensors based on spatial filtering velocimetry
Basal forces (normal and shear stress)	Load cells
Fluid pore pressure	Pressure sensors
Impact force	Pressure mark gauges, piezoelectric sensors