Spatial distribution of natural debris-flow impact

University of Natural Resources and Life Sciences, Vienna, Austria

^* Corresponding author: georg.nagl@boku.ac.at

Abstract

The high destructive potential of debris flows poses a challenge for the design of structural mitigation measures to protect vulnerable areas. An essential part of designing such structures is to determine the magnitude and spatial distribution of the impact forces. The impact is expected to be related to the composition of the flow, which can vary from clay to large boulders along a flow event and between events. Experimental studies are prone to scaling bias and benchmark observations at the full scale are rare so far. Here we present measurements of the temporal and spatial variations of the impact of a natural debris flow in the Gadria creek, IT, onto an instrumented barrier structure. The flow event was preceded by a precursory surge, which was then followed by the debris flow with multiple surges. The flow height reached up to 2.3 m. We found that the impact of boulders occurs primarily in the upper half of the flow profile, the highest forces were measured in first part of the flow, and deposition has a strong influence on the lower part of the structure by damping and/or redirection.