Protective forests as Ecosystem-based solution for Disaster Risk Reduction (ECO-DRR) [Working Title], 2021
In this chapter, we give a short overview of the protective effects of forests against snow avala... more In this chapter, we give a short overview of the protective effects of forests against snow avalanches, landslides and rockfall hazards in mountain areas. The overview is based on the protective mechanisms provided by forest and connects them to the effect-related indicators of forest structure from literature and European protective forest management guidelines. The thresholds of the effect-related indicators are hazard-related silvicultural targets for forest management and critical values for hazard risk assessment. The assessment of the protective effects of forests is a central part of natural hazard risk analysis and requires information on different spatial levels from single tree to slope-scale attributes. Forests are efficient in preventing snow avalanche and landslide initiation; however, they are usually unable to stop large masses of snow, soil and rock in motion. Therefore, guidelines on silvicultural targets and practices must focus on the mitigation of hazard onset pr...
Protective forests as Ecosystem-based solution for Disaster Risk Reduction (ECO-DRR) [Working Title], 2021
Mapping of protective functions and effects of forests is subject to geodata on 1) natural hazard... more Mapping of protective functions and effects of forests is subject to geodata on 1) natural hazard susceptibilities (hazard potential), 2) assets to be protected (damage potential), and 3) forest conditions, that is, forest use (legal extent) and cover (structure). Objectives in terms of legal definitions of assets and levels of risk acceptance (protection targets) as well as on the necessary and guaranteed reliability of the map products determine the mapping scale and the requirements for the methods and input data to be used. However, applied definitions of protection targets are often missing in the legislative bases and mapping approaches must rather be adapted to the existing geodata, their conceptual data model and quality, than simply using existing methods. Agreeing on the assets to be protected and the quality of their digital representation in terms of spatial resolution, positional accuracy, currentness, topological consistency, and entities is crucial for mapping object ...
Verbesserung der Erfassung der Schutzwaldkulisse für die forstliche Raumplanung. Methodik. Prozessmodellierung Steinschlag für die Kartierung von Wald mit Objektschutzfunktion
Mountain forests play an important role in the protection against rockfall events. Within the Int... more Mountain forests play an important role in the protection against rockfall events. Within the Interreg Alpine Space project RockTheAlps the focus is on how the protection effect can be quantified, allowing to establish a rockfall risk reduction (RRR) index for mountain forests. Based on multiple rockfall simulations on a virtual terrain, parameterized by real forest stand data, Dupire et al. (2016) presented three risk reduction indexes accounting for the protection effect of forests: 1. BARI(x) is an indicator of frequency reduction of the rock-fall hazard as it directly gives the percentage of rocks stopped due to the presence of forest on x m along the maximum slope direction. It is defined as:
Analyzing the influence of forests on rockfall events Elisabeth Laus (1), Frank Perzl (2), Andrea... more Analyzing the influence of forests on rockfall events Elisabeth Laus (1), Frank Perzl (2), Andreas Kofler (2), Karl Kleemayr (2), Roland Köck (3), and Christian Scheidl (1)
Digital maps of the snow depth are basis of the assessment of the avalanche release susceptibilit... more Digital maps of the snow depth are basis of the assessment of the avalanche release susceptibility and of the protection effect of forests and defence constructions. Climate scientists predict a decrease of snow accumulation and an increase of the proportion of fluid precipitation in the Austrian Alps as a response of climate change. This could lead to a change of avalanche danger. Because of their spatial resolution, presently available digital maps of recent snow depth result in insufficient avalanche susceptibility maps. These maps also may underestimate the snow depth of high altitudes as a consequence of the lack of meteorological stations in high altitudes and because of the derivation from the elevation only by linear extrapolation. There are clues to a non linear behaviour or a trend break of the gradient. Regardless of the uncertainties of predictions and modelling, avalanche risk adaptation strategies to climate change need an estimation of future average snow pack conditi...
Worldwide, mountain forests represent a significant factor in reducing rockfall risk over long pe... more Worldwide, mountain forests represent a significant factor in reducing rockfall risk over long periods of time on large potential disposition areas. While the economic value of technical protection measures against rockfall can be clearly determined and their benefits indicated, there is no general consensus on the quantification of the protective effect of forests. Experience shows that wherever there is forest, the implementation of technical measures to reduce risk of rockfall might often be dispensable or cheaper, and large deforestations (e.g. after windthrows, forest fires, clear-cuts) often show an increased incidence of rockfall events. This study focussed on how the protective effect of a forest against rockfall can be quantified on an alpine transregional scale. We therefore estimated the runout length, in terms of the angle of reach, of 700 individual rockfall trajectories from 39 release areas from Austria, Germany, Italy and Slovenia. All recorded rockfall events passed...
A multi-annual landslide inventory for the assessment of shallow landslide susceptibility – Two test cases in Vorarlberg, Austria
Geomorphology, 2016
Abstract Geomorphological landslide inventories provide crucial input data for any study on the a... more Abstract Geomorphological landslide inventories provide crucial input data for any study on the assessment of landslide susceptibility, hazard or risk. Several approaches for assessing landslide susceptibility have been proposed to identify areas particularly vulnerable to this natural hazard. What they have in common is the need for data of observed landslides. Therefore the first step of any study on landslide susceptibility is usually the compilation of a geomorphological landslide inventory using a geographical information system. Recent research has proved the feasibility of orthophoto interpretation for the preparation of an inventory aimed at the delineation of landslides with the use of distinctive signs in the imagery data. In this study a multi-annual landslide inventory focusing on shallow landslides (i.e. translational soil slides of 0–2 m in depth) was compiled for two study areas in Vorarlberg (Austria) from the interpretation of nine orthophoto series. In addition, derivatives of two generations of airborne laser scanning data aided the mapping procedure. Landslide scar areas were delineated on the basis of a high-resolution differential digital terrain model. The derivation of landslide volumes, depths and depth-to-length ratios are discussed. Results show that most mapped landslides meet the definition of a shallow landslide. The inventory therefore provides the data basis for the assessment of shallow landslide susceptibility and allows for the application of various modelling techniques.
International Snow Science Workshop Grenoble Chamonix Mont Blanc October 07 11 2013, Oct 7, 2013
This contribution describes the development of a model suitable for regional scale delineation of... more This contribution describes the development of a model suitable for regional scale delineation of zones potentially affected by gravitational mass movement processes (avalanches, rockfall). The model is subsequently used for the identification of forest areas with direct protective function against these processes. With respect to the practical application of the model over larger areas and the accompanying challenges (assessment of input-data, model calibration, computational time) a simple empirical, raster-based process model with limited input requirements is proposed. The model provides the functionality to identify objects in the process area and automatically discards parts of the process areas, which do not affect any objects (e.g. parts of avalanche tracks downslope of objects). Following this method, an intersection of the obtained process areas and a layer representing the forest coverage returns forest patches with a direct protection function against the modeled process. First applications of the developed model approach yield promising results. However, potential for optimization regarding the computational efficiency of the current model prototype and the development and integration of further approaches for runout length estimation and process propagation is identified.
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Papers by Frank Perzl