Radar Mapping along landslide-prone areas is a useful tool to find any blocks or sections of rock that are moving and can cause rockfalls or -slides. The technology is not dependent on daylight and the instrument can be set up on a tripod if need for urgent measures arises.

Radarmonitoring E16 Bergen Voss Gudvangen

Deformation between 2014 and 2015 measured by ground based interferometric SAR draped over a 3D model acquired with a photogrammetry-drone. Green means no significant movements, yellow to red show patches of deformations especially in the lower debris area.

Challenge

The problem defined by the NPRA is to monitor six rockfall-exposed sites along a major highway (E16) to see whether it is possible to find and monitor larger blocks and / or rock faces that are in motion and that could potentially harm E16.

Method

A method called differential interferometry is used; this is also used in satellite-based radar measurements. The method assumes that the difference in the radar signal between two or more measurements taken at different times, are compared and from this comparison, one can calculate the movement as a time-dependent function. The displacement is measured in the radar line of sight on a millimetre scale, so that one can identify very small movements in the rock wall.

Results

The measurements have given the NPRA an overview of the rock walls along E16, which so far show signs of minor loose blocks / displacement. Eighteen months into the project no sign of significant movement in the monitored areas has been observed, other than the locality at Gudvangen, a rock face which is known for very large rockfall activity.