Observations and modeling of the braking effect of forests on small and medium avalanches

Feistl, Thomas; Bebi, Peter; Teich, Michaela; Bühler, Yves; Christen, Marc; Thuro, Kurosch; Bartelt, Perry

doi:10.3189/2014jog13j055

Cited by 49 publications

(80 citation statements)

References 32 publications

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“…Others have addressed the significance of interactions between forest and snow avalanches (e.g., Teich, 2013;Feistl et al, 2014) which can be accounted for by adjusting the Voellmy friction parameters for simulations. For the RAMMS-AV model, resistance parameters for forested areas of µ = 0.02 and ξ = 400 m s −2 for all magnitudes of avalanches can be found in the handbook (Bartelt et al, 2013a), but yet few suggestions are available for debris-flows.…”

Section: Discussionmentioning

confidence: 99%

Modeling debris-flow runout patterns on two alpine fans with different dynamic simulation models

Schraml

Thomschitz

McArdell

et al. 2015

Nat. Hazards Earth Syst. Sci.

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Abstract. Predicting potential deposition areas of future debris-flow events is important for engineering hazard assessment in alpine regions. To this end, numerical simulation models are commonly used tools. However, knowledge of appropriate model parameters is essential but often not available. In this study we use two numerical simulation models, RAMMS-DF (rapid mass movement system-debris-flow) and DAN3D (dynamic analysis of landslides in three dimensions), to back-calculate two well-documented debris-flow events in Austria and to compare the range and sensitivity of input parameters for the Voellmy flow model. All simulations are based on the same digital elevation models and similar boundary conditions. Our results show that observed deposition patterns are best matched with a parameter set of µ [-] and ξ [m s −2 ], ranging between 0.07 to 0.11 and 200 to 300 m s −2 , respectively, for RAMMS-DF, and between 0.07 to 0.08 and 300 to 400 m s −2 , respectively, for DAN3D. Sensitivity analysis shows a higher sensitivity of model parameters for the DAN3D model than for the RAMMS-DF model. This contributes to the evaluation of realistic model parameters for simulation of debris-flows in steep mountain catchments and highlights the sensitivity of the models.

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Section: Discussionmentioning

confidence: 99%

Modeling debris-flow runout patterns on two alpine fans with different dynamic simulation models

Schraml

Thomschitz

McArdell

et al. 2015

Nat. Hazards Earth Syst. Sci.

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show abstract

“…In this case, the avalanche is slowed down by the increased turbulent friction and the entrainment of the woody debris in this area (Bartelt and Stöckli, 2001). Detrainment of snow is dominant in areas where σ < σ and no destruction takes place (Feistl et al, 2014b).…”

Section: T Feistl Et Al: Forest Damage By Avalanchesmentioning

confidence: 99%

“…For the wet snow case p w , we assume that dynamic pressures are small in comparison to the static pressure arising from the weight of the snow that loads the tree. Our assumption is based on observations of wet snow avalanche deposits and levee formation (Bartelt et al, 2012b;Feistl et al, 2014b). Often wedges of snow pile up upstream of trees.…”

Section: Four Avalanche Flow Regimesmentioning

confidence: 99%

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Forest damage and snow avalanche flow regime

Feistl

Bebi²,

Christen³

et al. 2015

Nat. Hazards Earth Syst. Sci.

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Abstract. Snow avalanches break, uproot and overturn trees causing damage to forests. The extent of forest damage provides useful information on avalanche frequency and intensity. However, impact forces depend on avalanche flow regime. In this paper, we define avalanche loading cases representing four different avalanche flow regimes: powder, intermittent, dry and wet. Using a numerical model that simulates both powder and wet snow avalanches, we study documented events with forest damage. First we show that in the powder regime, although the applied impact pressures can be small, large bending moments in the tree stem can be produced due to the torque action of the blast. The impact area of the blast extends over the entire tree crown. We find that, powder clouds with velocities over 20 m s −1 can break tree stems. Second we demonstrate that intermittent granular loadings are equivalent to low-density uniform dry snow loadings under the assumption of homogeneous particle distributions. The intermittent regime seldom controls tree breakage. Third we calculate quasi-static pressures of wet snow avalanches and show that they can be much higher than pressures calculated using dynamic pressure formulas. Wet snow pressure depends both on avalanche volume and terrain features upstream of the tree.

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“…In the case of small to medium-scale snow avalanches (i.e., < ca. 10000 m 3 ), forests can also extract snow from the avalanche flow through deposition on 20 the upslope-facing part of tree stems and on other obstacles (Feistl et al, 2014). Forest parameters such as stand composition, stem density and terrain roughness have thus not only an effect on stabilizing the snowpack in potential release areas (Bebi et al, 2009;Viglietti et al, 2010), but may also influence the spatial extent of small and medium-sized avalanches .…”

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confidence: 99%

Assessing the interaction between mountain forests and natural hazards at Nevados de Chillán, Chile, and its implications for Ecosystem-based Disaster Risk Reduction

Casteller¹,

Häfelfinger²,

Donoso³

et al. 2017

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Abstract.Gravitational natural hazards such as snow avalanches, rockfalls, shallow landslides and volcanic activity represent a risk factor for mountain communities around the world. In particular where documentary 15 records about these processes are rare, decisions on risk management and land-use planning have to be based on a variety of other sources including vegetation and tree-ring data and natural hazard process models. We used a combination of these methods in order to evaluate dynamics of snow avalanches and other natural hazards at Valle de las Trancas, in the Biobío Region in Chile. Along this valley, natural hazards threaten not only the local human population, but also the numerous tourists attracted by outdoor recreational activities. Given the regional 20 scarcity of documentary records, tree-ring methods were applied in order to reconstruct the local history of snow avalanches and debris flow events, which are the more important weather-related processes at respective tracks.A recent version of the model Rapid Mass MovementS (RAMMS), that includes influences of forest structure, was used to calculate different avalanche parameters such as runout distances and maximum pressures, taking into consideration the presence/absence of forest along the tracks as well as different modelled return periods. 25Our results show that local Nothofagus broadleaved forests contribute to a reduction of avalanche runout distances as well as impact pressures on present infrastructure, thus constituting a valuable ecosystem disaster risk reduction measure that can substitute or complement other traditional measures such as sheds.

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Observations and modeling of the braking effect of forests on small and medium avalanches

Cited by 49 publications

References 32 publications

Modeling debris-flow runout patterns on two alpine fans with different dynamic simulation models

Modeling debris-flow runout patterns on two alpine fans with different dynamic simulation models

Forest damage and snow avalanche flow regime

Assessing the interaction between mountain forests and natural hazards at Nevados de Chillán, Chile, and its implications for Ecosystem-based Disaster Risk Reduction

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