BACK CALCULATION OF AVALANCHE DIMENSIONS FROM LASER SCANNING AND SFM- PHOTOGRAMMETRY

ABSTRACT: After avalanche events happen it is always difficult to collect useful data from the avalanche dimensions such as snow volume that was released in the avalanche starting zone, entrained in the track and deposited in the accumulation zone. Usually rapidly changing weather conditions or measures taken to remove the snow for emergency rescue preclude the possibility to collect useful data after the avalanche occurred. Snow depth data of the slopes involved prior to the avalanche basically never exists, if the avalanche was not artificially released for a scientific test. But such data is vitally important to calculate avalanche dynamic parameters and in tragic cases such as the avalanche that occurred in Longyearbyen Svalbard on December 19th 2015 for event documentation to improve hazard mapping. In this work we explain how it is possible using sfm-photogrammetry done using pictures from a simple smart phone camera or other cameras using a fixed objective in combination with terrestrial laser scanning to achieve such data. We discuss data accuracy we achieved investigating the Longyearbyen avalanche and explain a methodology that can be used for snow depth mapping for back calculation of avalanche events anywhere in the world