Presenter/Author Information

B. Mazzorana
C. Scherer
N. Marangoni

Keywords

debris flow, natural hazard, object protection, risk analysis, torrent control

Start Date

1-7-2008 12:00 AM

Description

Recent extreme debris flow and hyper-concentrated flow events in the Alpine Regions have shown on the one hand the enormous destructive impact power on buildings, bridges and roads, and on the other hand, the limits of "classical" torrent control measures. Due to reliability constrained efficiency of consolidation protection measures with unsatisfactory performance in case of extreme events the sediment load volume is higher than expected due to remobilization phenomena. In many cases check dams with sediment retention or sorting function don't function properly and the openings are immediately obstructed. The results of an extended backward and forward oriented investigation clearly suggest a change of paradigm for the torrent control strategy at least where the possibility for hazard reduction is extremely limited, if pursuit with the construction of classical torrent control measures. This work suggests enlarging the toolkit for torrent control by going beyond "object protection" for buildings on the debris flow phenomena affected alluvial fans. The number of endangered objects located in the red, blue and yellow hazard zone has to be reduced to a minimum. Here we propose, starting from an in-depth understanding of the involved processes and overland flow dynamics, the construction of protection structures, the specific reinforcement and where necessary a functional reshaping of building's boundaries, terrain breaklines, and roads in order to obtain a maximum damage reduction diverting the flow towards sectors where the value at risk is lower. The goal is to identify the set of construction elements that minimizes the expected damage. It's an iterative procedure that involves a series of numerical simulations corresponding to each particular protection configuration. A simplifying graph theoretic schematization of the overland flow dynamics permits to identify suitable locations for the construction of these protection elements and to reduce the computational efforts reducing the number of simulations otherwise required. The procedure has been applied to a case study.

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Jul 1st, 12:00 AM

Additional torrent control strategies on debris flow alluvial fans with extremely high vulnerable settlements

Recent extreme debris flow and hyper-concentrated flow events in the Alpine Regions have shown on the one hand the enormous destructive impact power on buildings, bridges and roads, and on the other hand, the limits of "classical" torrent control measures. Due to reliability constrained efficiency of consolidation protection measures with unsatisfactory performance in case of extreme events the sediment load volume is higher than expected due to remobilization phenomena. In many cases check dams with sediment retention or sorting function don't function properly and the openings are immediately obstructed. The results of an extended backward and forward oriented investigation clearly suggest a change of paradigm for the torrent control strategy at least where the possibility for hazard reduction is extremely limited, if pursuit with the construction of classical torrent control measures. This work suggests enlarging the toolkit for torrent control by going beyond "object protection" for buildings on the debris flow phenomena affected alluvial fans. The number of endangered objects located in the red, blue and yellow hazard zone has to be reduced to a minimum. Here we propose, starting from an in-depth understanding of the involved processes and overland flow dynamics, the construction of protection structures, the specific reinforcement and where necessary a functional reshaping of building's boundaries, terrain breaklines, and roads in order to obtain a maximum damage reduction diverting the flow towards sectors where the value at risk is lower. The goal is to identify the set of construction elements that minimizes the expected damage. It's an iterative procedure that involves a series of numerical simulations corresponding to each particular protection configuration. A simplifying graph theoretic schematization of the overland flow dynamics permits to identify suitable locations for the construction of these protection elements and to reduce the computational efforts reducing the number of simulations otherwise required. The procedure has been applied to a case study.