Regional Debris Flow Hazard Assessment of the Grdelica Gorge (Serbia)

Abstract

AbstractRoad infrastructure development is currently very intensive in Serbia. One such example is the Grdelica Gorge, where a new highway was aligned and put into service in 2019. The Gorge has provided a very challenging engineering environment imposing high levels of several hazard types: floods; slides; debris flows; and rockfalls. In this work, the debris flow hazard for the first 15 km of the road route was in focus. The assessment included an expert-driven analysis for identifying potential source areas, coupled with deterministic modelling of the flowing process originating from these source areas, resulting in detailed simulations of the final runout distance, height of deposit, and flow velocity, which are all reliable parameters for mitigating the hazard across the road alignment. A combination of geomorphological criteria, processed in a GIS environment was used to narrow down the search of source areas containing loose, erodible material which easily mobilizes under saturated conditions. The criteria were calibrated by the outlines of the available inventory, acquired by remote sensing techniques. The Digital Terrain Model with 12.5 m resolution was used for running RApid Mass Movement Simulation (RAMMS), using estimated bulk density and friction coefficients as input parameters. Since there was no recent debris flow in the area for the appropriate back-analysis of these parameters, experience-and lab-based estimations were used. Several simulations have reached the road alignment, wherein a few imposed significant threats with respect to deposit height and velocity that require additional attention.