Rockfalls are one of the most common natural hazards in mountainous areas that pose high risk to people and their activities. Rockfall risk assessment is commonly performed with the use of models that can simulate the potential rockfall source, propagation and runout areas. The quality of the models can be improved by collecting data on past rockfall events. Mobile crowdsourcing is becoming a common approach for collecting field data by using smartphones, the main advantages of which are the use of a harmonised protocol, and the possibility of creating large datasets due to the simultaneous use by multiple users. This paper presents a new methodology for collecting past rockfall events with a mobile application, where the locations and attributes of rockfall source areas and rockfall deposits are collected, and the data are stored in an online database which can be accessed via the WebGIS platform. The methodology also presents an approach for calculating an actual source location based on viewshed analysis which greatly reduces the problem of field mapping of inaccessible source areas. Additionally, we present a rockfall database in the Alpine Space that has been created by the presented methodology, and an application of collected data for the calibration and validation of two rockfall models (CONEFALL and Rockyfor3D).
This article examines how digital terrain model (DTM) grid cell size influences rockfall modelling using a probabilistic process-based model, Rockyfor3D, while taking into account the effect of forest on rockfall propagation and runout area. Two rockfall sites in the Trenta valley, NW Slovenia, were chosen as a case study. The analysis included DTM square grid cell sizes of 1, 2, 5, and 10 m, which were extracted from LiDAR data. In the paper, we compared results of rockfall propagation and runout areas, maximum kinetic energy, and maximum passing height between different grid cell sizes and forest/no forest scenario, namely by using goodness-of-fit indices (average index, success index, distance to the perfect classification, true skill statistics). The results show that the accuracy of the modelled shape of rockfall propagation and runout area decreases with larger DTM grid cell sizes. The forest has the important effect of reducing the rockfall propagation only at DTM1 and DTM2 and only if the distance between the source area and forest is large enough. Higher deviations of the maximum kinetic energy are present at DTMs with larger grid cell size, while differences are smaller at more DTMs with smaller grid cell sizes. Maximum passing height varies the most at DTM1 in the forest scenario, while at other DTMs, it does not experience larger deviations in the two scenarios.
Abiotic and biotic disturbances in alpine forests can reduce forest cover or change the structure of the forest and consequently reduce the protective effect of forest against natural hazards such as avalanches and rockfalls. In this review article, the effect of the main abiotic (forest fire, windthrow, ice break, snow break, avalanche and rockfall) and biotic (insects and pathogens) disturbances in protection forests are presented along with their potential influence on the protective effect of forest against avalanches and rockfalls. In general, natural disturbances negatively affect the protective effect of forest, especially in the case of large-scale and severe events, which in alpine areas are mostly caused by storms, bark beetle outbreaks, avalanches and forest fires. Climate change induced interactions between disturbances are expected to present challenges in the management of protection forests in the future. key words: natural disturbances, natural hazards, abiotic disturbances, biotic disturbances, protection forests, protective effect, stand parameters, rockfall, avalanche izvleček V gozdovih alpskega prostora lahko abiotske in biotske motnje vplivajo na porazdelitev in strukturo gozdov do te mere, da jim zmanjšajo varovalni učinek pred naravnimi nevarnostnimi, kot so snežni plazovi in skalni podori. V članku je zato predstavljen pregled glavnih vplivov abiotskih (gozdni požari, vetrolom, snegolom, žled, snežni plazovi in skalni podori) in biotskih (insekti in patogeni) motenj na varovalno in zaščitno funkcijo gozdov pred snežnimi plazovi in skalnimi podori. Naravne motnje na splošno negativno vplivajo na varovalni učinek gozda pred naravnimi nevarnostmi, še posebej v primeru veliko-površinskih dogodkov z visoko jakostjo poškodovanosti. Slednje so v alpskem prostoru najpogosteje posledica neviht, napada podlubnikov, snežnih plazov in gozdnih požarov. Podnebne spremembe in njihov vpliv na naravne motnje bodo v bodoče postale pomemben izziv pri upravljanju z gozdovi, ki opravljajo varovalno in zaščitno funkcijo. ključne besede: naravna motnja, naravne nevarnosti, varovalna in zaščitna funkcija gozda, varovalni učinek, sestojni parametri, skalni podor, snežni plaz GDK 907.32:38:42(045)=163.6 Prispelo / Received: 11.
Trees represent an important archive that can be used to reconstruct the spatial and temporal patterns of rockfall events. Rockfall impacts can be recorded in the form of anomalies in tree rings and impact scars on the tree stem. In this paper we demonstrate the use of an approach based on counting scars for reconstructing the frequency and spatial pattern of past rockfalls. The approach was applied by counting the visible scars on the stem surface of 52 European beech trees (Fagus sylvatica L.) in the area of the Trenta Valley, Slovenia. The average number of impacts per trees was 7, and the impacts were mostly classified as old, indicating reduced rockfall activity in recent years. The average recurrence interval was 31.8 years, which was reduced by 1.2 years by the application of the conditional impact probability. The spatial pattern of rockfall impacts shows that rockfall activity is higher in the middle part of the studied slope. IZVLEČEKDrevesa so pomemben arhiv podatkov o preteklih dogodkih za rekonstrukcijo prostorske in časovne aktivnosti skalnih podorov, saj beležijo vplive skalnih podorov z anomalijami v rasti drevesnih branik ali prek vizualnih poškodb, vidnih na površju debel. V prispevku je predstavljena metodologija preučevanja skalnih podorov z analizo vidnih poškodb na deblu 52 dreves navadne bukve (Fagus sylvatica L.) na območju doline Trente v Sloveniji. Na podlagi analize smo ugotovili, da je povprečno število poškodb na posamezno drevo 7 ter da večinoma spadajo v kategorijo starih poškodb, kar kaže na manjšo aktivnost skalnih podorov v zadnjih letih. Povprečna povratna doba pojavljanja skalnih podorov je znašala 31,8 let; le-ta pa se skrajša za 1,2 leta, če upoštevamo pogojno verjetnost vpliva, da skale lahko zgrešijo drevesa. Prostorsko pojavljanje skalnih podorov kaže na večjo aktivnost v osrednjem delu preučevanega pobočja.Ključne besede: skalni podori, naravne nevarnosti, dendrogeomorfologija, drevesne branike, poškodbe debla, povratna doba GDK 384+585(497.4Trenta)(045)=111 Prispelo /
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