The increasing intensity and frequency of extreme weather events in the Mediterranean region, presumably linked to climate change, threaten the most vulnerable environmental and socio-economic systems. Arpa Veneto, with the regional department for territorial security, is involved in an ambitious European project, TRANS-ALP, funded by the European Union program for prevention and
preparation in the field of civil protection and marine pollution. The overall objective of the project is to develop an integrated methodology for the multi-risk assessment following extreme weather phenomena and the prediction of their impact for mountainous regions on a cross-border scale, in order to further advance decision-making processes and support the transnational cooperation in the European Union during the natural disaster management cycle. The Austrian Central Institute of Meteorology and Geodynamics – ZAMG, the Austrian Forest Research Institute – BFW and the Vicenza-based European Project Consulting – EPC are partners of Trans-Alp.

Fig. 1 – an extreme meteorological phenomenon, such as the VAIA storm, creates a series of problems that can occur at different times: a) landslides and floods occur during or immediately after the meteorological phenomenon that caused them; b) the felling of trees by the wind can generate a series of new avalanche sites which in snowy winters can threaten homes and infrastructures; c) the vegetation on the ground facilitates the proliferation of the Bostrico Tipografo, an insect capable of killing entire portions of spruce plants forest.

The main results presented to the European Union in the first year of activity

Arpa Veneto in the first year of the project focused on the critical review of various multi-risk assessment methodologies used in the countries of the Alpine arc, to try to provide a conceptual methodology integrated into the management cycle of natural disasters.

Trigger rainwater thresholds.

Due to the high energy of the relief, due to its morphology and the various geological fragilities associated with the structure of the mountains, the alpine environment is subject to frequent instability phenomena such as landslides, avalanches and torrential floods. The experience of Arpa Veneto, gained in recent decades in civil protection procedures, has led to the awareness that an effective way to mitigate the hydrogeological risk is to improve the warning system based on triggering rain thresholds. As the studies of the scientific community in this sector show, in order to identify reliable rainfall thresholds it is necessary to know a considerable number of historical instability events such as to guarantee a solid statistical basis representative of the meteorological phenomenon. The databases a b c present on the national territory to date, first of all the Inventory of Italian Landslide Phenomena – IFFI, are rich in information on the correct location of landslides, but there is very little information relating to when these occurred, thus making the work of restitution of rainfall thresholds particularly difficult to carry out. In the TRANS-ALP project, a methodology that could overcome this limit was therefore developed and proposed to the Civil Protection System of the European Union. The proposed method, easy to apply, is based on the statistical analysis of the rainfall recorded by the automatic stations since they were installed in the mid-1980s. Once the maximum daily precipitation has been identified, the values ​​relating to the days in which precipitation was recorded equal to the 99th percentile with respect to the maximum precipitation are extrapolated. Having identified the potentially critical dates, the technicians of Arpa Veneto searched for possible effects on the ground in the historical archives of newspapers, in the reports of the Fire Brigade, in the technical reports of research and municipalities.
The results were encouraging, especially as regards the instability that responds to persistent rainfall characteristic of the autumn and winter seasons. The procedure led to the identification of numerous failures that were already known, but that had never been associated with a specific date in any official database. By expanding and refining the methodology, the number of reported damage events increased up to a significant number in order to statistically analyze rainfall, with the aim of identifying representative trigger thresholds for a given area.

Data collection on natural disasters and webgis.

In collaboration with the other project partners, Arpa Veneto conducted a critical analysis of how the various administrations responsible for collecting data relating to natural disasters operate in their respective countries. What has emerged is a great heterogeneity, at European level, in the management of these data. Among the few aspects that the different databases have in common is the use of webGIS generally open to the public for data sharing. Nevertheless, the webGIS themselves are organized in a non-uniform way in the representation of the data and hardly contain information on events that occurred before their publication. A virtuous example in this sense is the webGIS avalanche officially presented by the Avalanche Center of Arabba of Arpa Veneto in 2021.

Fig. 2 – The ARPAV avalanche webGIS . A virtuous example of a database that has been constantly updated since the mid-1980s


In fact, all the data relating to the constantly updated avalanche location map, the cadastre of the defense works, the Plans of the Areas Exposed to Avalanches and the technical reports with attached photographs of all the avalanche phenomena recorded by the technicians converge in the database of the Avalanche Center in over 30 years of activity. The report analyzed all the management and representation systems of data relating to natural disasters and highlighted the strengths and weaknesses of each system. Finally, guidelines were proposed for the collection and management of data in order to provide the member countries of the European Union with a methodology that is as uniform as possible also for easier sharing of information. The guidelines range from indications on the reference systems to be adopted during mapping, to the type of data to be recorded, but above all they contain the proposal to establish a common European-wide database of disasters connected to intense meteorological events. The TRANS-ALP project is, in fact,
focused on classifying the danger of what are defined chain effects resulting from intense meteorological phenomena. The VAIA storm certainly taught a lot in this sense: the mapping of landslides and flooded areas carried out close to the event was certainly not exhaustive of the effects on the ground that would have been recorded in subsequent years. In fact, the felled trees have generated numerous new avalanche sites, in many cases insisting on vulnerable elements such as houses and infrastructures. Just as the trees left on the ground in order to mitigate the avalanche risk up to the completion of the defense works have increased the risk of proliferation of the Spruce Bark beetle. In the coming weeks, an example of multi-risk classification that takes into account all the phenomena that may occur as a consequence of a storm will be published on the TRANS-ALP website, thanks to a webGIS viewer. Thanks to the experience of the EURAC research center gained in this sector, the above has been further represented thanks to the conceptual model of the impact chain methodology consisting of a multi-risk analysis model capable of describing the cause-effect relationship between all factors that constitute the vulnerability of a system and analyze the climatic signals that can lead to an increase in risk. The model is a useful analysis tool for the civil protection system.


Fig. 3 – the TRANS-ALP webGIS will soon give the possibility to visualize in a multi-risk perspective the various fragilities that can be linked following an intense meteorological phenomenon such as the VAIA storm

Simulation model of post-extreme instability.

Finally, a geostatistical model was developed by the technicians of Arpa Veneto capable of simulating the propensity for instability following an event, such as that of VAIA, capable of upsetting the morphological and forest cover balances of a given territory. The model, taking into account all the morphological characteristics and vegetation cover, thanks to a specific algorithm, returns the probability of triggering of an avalanche phenomenon. Once the trigger areas have been identified, the model automatically processes the release of avalanches and calculates their trajectory on a morphological basis, also indicating which vulnerable elements may be affected by the avalanche transit. This easy-to-use tool will be of great use in the first civil protection actions following the meteorological event, in order to identify intervention priorities for risk mitigation.



Fig. 4 – the model developed by the technicians of Arpa Veneto on the basis of some input data automatically calculates the trigger zones of the avalanches, the trajectory of the same and signals the vulnerable elements potentially affected by the phenomenon


Next Steps

Before the end of the project, the technicians of Arpa Veneto will develop a mathematical elaboration model capable of returning, following events such as VAIA, the height values ​​of the vegetation falled to the ground. The trees falled to the ground constitute, in fact, a first protection against the possibility of triggering of avalanches, therefore capable of mitigating the risk until the defense works are carried out; it is essential to know its height to understand how much snow must accumulate on the ground before creating a real problem for the towns below. This value then becomes the starting point in the application of the various civil protection procedures still in place today in the territories affected by VAIA. At the end of the project, an integrated tool will therefore be available capable of returning a multi-risk scenario following extreme meteorological phenomena and, at the same time, of providing tools of immediate use to support civil protection operations and procedures.