Debris-Flow Monitoring and Geomorphic Change Detection Combining Laser Scanning and Fast Photogrammetric Surveys in the Moscardo Catchment (Eastern Italian Alps)

Monitoring debris-flow prone catchments and collecting field data is of extreme importance for improving the knowledge and therefore the management of such hazardous phenomena. High-resolution Digital Elevation Models (DEMs) have recently established as an important tool for the study of geo-hydrological and geomorphological processes. Monitoring surface changes over time allows to analyze sediment dynamics from several points of view, ranging from the accounting of volumetric changes to numerical modeling, to the correlation of morphometric indexes with different components of geo-hydrological processes. The present study examines the Moscardo Torrent, a small alpine stream in the Eastern Italian Alps which is characterized by a high occurrence of debris flows. The original monitoring instrumentation, which made it possible to record hydrographs of 15 debris-flow events in the years 1989- 1998, was renewed, allowing to record three debris flows in the years 2011-2012. Surface morphology of three areas exposed to debris-flow dynamics was surveyed across the recorded debris-flow events by means of Terrestrial Laser Scanning (TLS), and 0.2 m DEMs of Differences (DoDs) were calculated. During the third TLS campaign, close-range digital photogrammetric images were acquired in order to directly compare 3D surface representation with the high-resolution DEMs derived by TLS.