Gravitational Natural Hazards Research Articles

ProForM: A simulation model for the management of mountain protection forests

Protection from gravitational natural hazards such as snow avalanches and rockfall is among the most important ecosystem services provided by forests in steep mountain terrain such as the European Alps. These so-called “protection forests” often have to be actively managed to ensure a sustainable ecosystem service provision in time and space. For studying these slowly developing ecosystems, dynamic forest models are important tools to assess the effect of management on the protective function. However, existing models focus on the current protective effect and in many cases neglect aspects of stand resistance and resilience to large disturbances, which are important factors for maintaining the long-term protective function. Therefore, we developed ProForM, a new dynamic forest model aimed at (1) reproducing stand dynamics of managed temperate mountain forests and (2) assessing their protective function in detail. ProForM is a structurally simple model that contains mechanistic formulations of basic demographic processes but was developed mainly with empirical data. It is spatially explicit and was developed with a focus on regeneration dynamics. The model is parameterized for four tree species (Picea abies, Abies alba, Fagus sylvatica, and Acer pseudoplatanus) and four elevational zones, ranging from mixed species submontane to spruce-dominated subalpine forests. ProForM was calibrated with and validated against independent data from long-term forest inventories from Switzerland. It exhibited a satisfactory performance in reproducing measured basal area, stem number, diameter distribution and mean crown ratio at the stand level, comparable to the performance of other, typically more complex models. Illustrative example simulations demonstrate the assessment of the protective function of a stand against gravitational hazards according to multiple criteria used in forestry practice in Alpine countries. ProForM is a valuable new tool to study the impacts of management on the protective effect of mountain forests, and to inform forest managers.

Assessing the interaction between mountain forests and snow avalanches at Nevados de Chillán, Chile and its implications for ecosystem-based disaster risk reduction

Abstract. Gravitational natural hazards such as snow avalanches, rockfalls, shallow landslides and volcanic activity represent a risk to mountain communities around the world. In particular, where documentary 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, tree-ring data and natural hazard process models. We used a combination of these methods in order to evaluate dynamics of natural hazards with a focus on snow avalanches at Valle 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 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 most important weather-related processes at respective tracks. A recent version of the model Rapid Mass MovementS (RAMMS), which includes influences of forest structure, was used to calculate different avalanche parameters such as runout distances and maximum pressures, taking into consideration the presence or absence of forest along the tracks as well as different modeled return periods. Our results show that local Nothofagus broadleaf forests contribute to a reduction of avalanche runout distances as well as impact pressure on present infrastructure, thus constituting a valuable ecosystem disaster risk reduction measure that can substitute or complement other traditional measures such as snow sheds.

A Topography-Informed Morphology Approach for Automatic Identification of Forest Gaps Critical to the Release of Avalanches

Human assets in Alpine regions are prone to gravitational natural hazards such as rock fall, shallow landslides and avalanches. Forests make up a substantial share in that landscape and can mitigate those hazards. Management of avalanche protection forests must cope with avalanches potentially released in forest gaps, which can damage downslope forests. The Swiss guidelines “Sustainability and success monitoring in protection forests” prescribe forest-gap extents in slope-line direction critical to the release of avalanches in forested areas. This article proposes a topography-informed morphology approach (TIMA) to automate the detection of critical gaps based on a digital terrain model and a canopy height model (CHM) derived from airborne LiDAR-data. TIMA uses complementary information about topography to probe forest gaps computed from the CHM with templates meeting critical-gap extents adjusted to local topography. The method was applied to a test site in Klosters-Serneus (Switzerland). The comparison of a critical-gap map with the results of a field assessment at 19 sample locations resulted in 84% overall accuracy. Moreover, plausibility of gap detection could be improved by including linear features forest roads and torrent channels in TIMA to account for decoupled snow layer resulting from abrupt breaks on the hillslope. If the TIMA concept can be successfully applied to the case of avalanches, this would encourage its use in assessing other gravitational natural hazard processes.

Fungi inhabiting fine roots of Pinus heldreichii in the Montenegrin montane forests

Pinus heldreichii H. Christ. is a tertiary relict and endemic to the western Balkans and southern part of Apennine peninsula. It is an Oro-Mediterranean species occurring at altitudes between 1200 and 2000 m and primarily on calcareous soils. P. heldreichii forests are of key importance for nature conservation, protection against gravitational natural hazards, landscape conservation and recreation. However, these forests are currently highly fragmented and require the elaboration of guidelines for sustainable management and conservation that should be based on scientific knowledge. Ectomycorrhizal (ECM) fungi are important for successful regeneration, establishment and growth of P. heldreichii. The aim of this study was to investigate ECM and other fungal communities associated with fine roots of P. heldreichii at two different sites in Kuci Mountains, south-eastern Montenegro. Roots and soil were sampled from 70 trees. Soil was subjected to chemical analyses, fine roots were morphotyped and selected root morphotypes were Sanger sequenced using ITS rDNA as a marker. Sequencing resulted in 431 high-quality sequences representing 147 different fungal species including a large number of ECM species. The most common species were ECM fungi Lactarius sanguifluus (5.1%), Wilcoxina rehmii (4.2%) and Amphinema sp. KK28 (3.2%). Climatic factors were similar between the sites, but site size, inclination, elevation, tree age (old growth versus young trees), and some soil characteristics differed. The results demonstrate relatively high fungal diversity and site-specific effects on abundance and composition of fungal communities in fine roots of P. heldreichii growing in high-altitude marginal habitats.

Gravitational natural hazards: Valuing the protective function of Alpine forests

Forests produce significant non-market benefits by protecting residential and commercial real estate as well as all kinds of infrastructure (e.g. rail tracks, highways, power lines) against gravitational natural hazards such as avalanches, mudslides, and rockfall. The Austrian Federal Forests (Österreichische Bundesforste – ÖBf) recently commissioned a research project on the valuation of this ecosystem service by means of the replacement cost method and the hedonic pricing approach.Based on the international literature, this paper focuses on a careful and realistic design of the baseline scenario with which the “marginal change” in ecosystem services can be assessed and valued. While the (current) management scenario is rather clear and reflects the approach pursued by the ÖBf (reasonably labeled as multifunctional forestry), the design of the baseline scenario (intensified commercial forestry) assumes a reduced protective function of the forests which, however, would still have to be in line with strict legal frameworks such as the Austrian Forest Act or European nature conservation directives.Given these strict frameworks, the potential leeway for commercial forestry is rather limited; still, the current multifunctional forest management secures ecosystem services worth up to EUR 14.7m per year (valued at replacement costs of technical measures to substitute the protective function of forests), which corresponds to EUR 268 per hectare and year. The result of the hedonic pricing approach for property in hazard zones protected by forests is substantially lower: The ecosystem service is valued at EUR 2.9m per year (which corresponds to an annual per-hectare value of EUR 53). The results in general underline the importance of multifunctional forestry and of the ecosystem services function sustained especially in state-owned forests.

Rockfall hazard zones in Austria. Experience, problems and solutions in the development of a standardised procedure

AbstractThe Österreichische Raumordnungskonferenz (ÖROK) set up a partnership in 2011 to deal with ”Risk management for gravitational natural hazards in landuse planning“. As gravitational natural hazards have a decisive influence on development in the Alpine Region, standard procedures were developed for the assessment of the relevance of these processes for landuse planning. This paper describes the recommended procedure for the assessment of hazards affecting permanent settlements from rockfall in a top‐down approach. The first step to define potential conflicts between the maximum run‐out of rockfall processes and the presence of settlements is a conservative empirical assessment based on rock outcrops serving as potential detachment zones and the maximum reach of such rockfalls, leading to a hazard indication map. This approach is only based on existing cartographic information, field investigations are not necessarily involved at this stage. To ensure conservative results, the use of a high‐resolution 1 m ground model to identify rock outcrops is re commended. The next step includes a thorough examination of those areas in the hazard indication map with conflicts between the maximum reach/run‐out of falling blocks and settlements. This stage includes field investigations with mapping of maximum reach blocks, block size distributions, underground conditions of the transit zone and the condition of rock outcrops that act as potential detachment zones. All this information is subsequently integrated into a 3D rockfall simulation. As a result the modelling enables a delineation of areas out of reach (no rockfall hazard), areas with potential impact energies ≤ 100 kJ (low intensity) and areas with potential impact energies > 100 kJ (high intensity).

Impacts of business-as-usual management on ecosystem services in European mountain ranges under climate change

Mountain forests provide a multitude of services beyond timber production. In a large European project (ARANGE—Advanced multifunctional forest management in European mountain RANGEs), the impacts of climate change and forest management on ecosystem services (ES) were assessed. Here, we provide background information about the concept that was underlying the ARANGE project, and its main objectives, research questions, and methodological approaches are presented. The project focused on synergies and trade-offs among four key ES that are relevant in European mountain ranges: timber production, carbon storage, biodiversity conservation, and protection from gravitational natural hazards. We introduce the concept and selection of case study areas (CSAs) that were used in the project; we describe the concept of representative stand types that were developed to provide a harmonized representation of forest stands and forest management in the CSAs; we explain and discuss the climate data and climate change scenarios that were applied across the seven CSAs; and we introduce the linker functions that were developed to relate stand- and landscape-scale forest features from model simulations to ES provisioning in mountain forests. Finally, we provide a brief overview of the Special Feature, with an attempt to synthesize emerging response patterns across the CSAs.

How does forest structure affect root reinforcement and susceptibility to shallow landslides?

AbstractForests can decrease the risk of shallow landslides by mechanically reinforcing the soil and positively influencing its water balance. However, little is known about the effect of different forest structures on slope stability. In the study area in St Antönien, Switzerland, we applied statistical prediction models and a physically‐based model for spatial distribution of root reinforcement in order to quantify the influence of forest structure on slope stability. We designed a generalized linear regression model and a random forest model including variables describing forest structure along with terrain parameters for a set of landslide and control points facing similar slope angle and tree coverage. The root distribution measured at regular distances from seven trees in the same study area was used to calibrate a root distribution model. The root reinforcement was calculated as a function of tree dimension and distance from tree with the root bundle model (RBMw). Based on the modelled values of root reinforcement, we introduced a proxy‐variable for root reinforcement of the nearest tree using a gamma distribution. The results of the statistical analysis show that variables related to forest structure significantly influence landslide susceptibility along with terrain parameters. Significant effects were found for gap length, the distance to the nearest trees and the proxy‐variable for root reinforcement of the nearest tree. Gaps longer than 20 m critically increased the susceptibility to landslides. Root reinforcement decreased with increasing distance from trees and is smaller in landslide plots compared to control plots. Furthermore, the influence of forest structure strongly depends on geomorphological and hydrological conditions. Our results enhance the quantitative knowledge about the influence of forest structure on root reinforcement and landslide susceptibility and support existing management recommendations for protection against gravitational natural hazards. Copyright © 2015 John Wiley & Sons, Ltd.

Using a novel assessment framework to evaluate protective functions and timber production in Austrian mountain forests under climate change

In Central European mountain forests, timber production and the protection of infrastructure and settlements against gravitational natural hazards are key forest ecosystem services (ES). The quantitative assessment of mountain forest ES for management planning and decision support is a particular challenge, due to manifold involved spatial scales from tree to slope and landscape level. We present an assessment framework to analyze and communicate the effect of management and climate change on the provision of selected ES in mountain forests. Core element is the spatially explicit hybrid forest ecosystem model PICUS. Remote sensing data and inventories are combined to generate realistic fine-grained forest landscapes with single tree resolution as input to PICUS. Landscape-level planning of silvicultural prescriptions employs geographic information systems functionalities (locate skyline corridors and treatment areas, prescribe silvicultural operations based on tree-level attributes) and produces management maps, which are interpreted by PICUS and executed in course of simulation runs. Model output is imported into a spatially explicit landscape assessment tool to assess the protective effect of vegetation. In a 250 ha case study in the Eastern Alps in Austria, the assessment framework is demonstrated to evaluate effects of climate change and management on timber production and protection against landslides and snow avalanche release. Climate change had, depending on climate and management scenario both, positive and negative impacts on desired ES. Key factor for ES provisioning in the case study was the interaction of bark beetle disturbances, legacies of past land-use practices and forest management.

Integrales Management von gravitativen Naturrisiken in der Schweiz

Integral management of gravitational natural hazards in Switzerland The management of gravitational natural hazards has undergone several fundamental changes in the past centuries. As late as the 17th century, natural catastrophes were considered to be strokes of fate or the expression of divine or satanic dealings. In the age of Enlightenment the comprehension of the processes involved in these dangers grew, together with the conviction that it was possible by technical means to protect oneself against them. A long way into the 20th century this concept of protection from danger had a large following. The natural catastrophes of the second half of the 20th century then showed ever more clearly the technical and financial limits of this concept. By the middle of the 1960s protection from natural hazards began to be considered within the context of overall land-use development. Nowadays integral risk management, which includes risk analysis, evaluation, and response, is well anchored in practice as regards gravitational natural hazards. Nonetheless, in order to make the best use of the potential of this approach, it is now necessary to improve certain basic politico-legal, organisational, and professional conditions.

Aménagement du territoire basé sur le risque dans le canton de Vaud: quelques réflexions | Risk-based land-use planning in the canton of Vaud: a few considerations

In land-use planning, taking natural hazards into account cannot be based uniquely on the degree of danger, as shown on natural hazards maps. The level of risk brought in by the different types of human activity in the areas exposed to these hazards must also be taken into consideration. The communes in canton Vaud will soon have completed the realisation of all gravitational natural hazards maps according to catchment area. Consequently, a cantonal and intercommunal strategy for integral risk management must be put in place. The implementation of this strategy requires some prerequisites such as: legislation based on risks, a definition of protection objectives, the organisation of a decision-making process involving all parties concerned, and which will make possible a comprehensive evaluation of land-use related interests. These reflections should result in a change of attitude when faced with the risks linked to natural hazards, and hence land-use adapted to these risks respecting the principles of precaution, equity and proportionality.