Shallow Subsurface Orientation & Rainfall/Snowmelt

Shallow subsurface orientation is measured by tiltmeters. These devices measure orientation along two axes and are set in concrete poured on or near bedrock at depths of about two meters (the devices are buried by about two meters of soil). The orientations along both the X and Y axes of the tiltmeters are shown on the graph (for example, X1 on the graph indicates the tilt along the X axis of tiltmeter 1). Landslide movement would probably result in sufficient change of orientation of the tiltmeters to be detected. The tiltmeters are much less vulnerable than the cable extension transducers to false indications of displacement. However, frost penetration to the depth of the tiltmeters would probably result in such false indications. The tiltmeters are equipped with temperature sensors to assist in determining potential frost effects. Rainfall and snowmelt are measured with a tipping-bucket rain gauge. This instrument is set into concrete on the ground surface so should accumulate snowfall similar to adjacent ground. During periods of snowmelt the rain gauge provides an approximate measure of equivalent rainfall.