Aims and activities
Debris flows have always been a danger for mountain territories with their small, steep, catchments in which they develop. They are composed of water- sediments mixture of very different sizes and route along channels incised on mountain slopes, sometimes covering great distances. Debris flows generally occur in summer and early autumn and they are triggered heavy precipitation events of short duration (10-20 minutes); debris flow are impulsive and they can cause massive damage to buildings, block of traffic circulation and loss of life. Their destructive strength, caused by high impact forces, results in connection with the exposure and vulnerability of objects to the hydrogeological risk. Climate change increase this risk for people and their settlements, due to the increase in frequency of debris flow events because of more intense rain events that generate them.
Furthermore, the expansion of socio-economic activities makes the territory and society itself even more vulnerable, because of a greater exposure to risk.
In particular, since 2009, various sites in the Boite valley (Belluno) record an increasing debris flow events that cause damage and victims. Similar the situation at the Gröbentalbach (Tyrol): increasing debris flow activity in the last years is observed and endanger infrastructure facilities. The exceptional meteoric event of October 2018 (storm VAIA – signed of 300-700 mm precipitation and wind storms), which affected large parts of the Interreg Italy-Austria area, northern Veneto, eastern Tyrol and south-east Carinzia, generated numerous debris flows events. The large number of potentially threatened sites, the lack of flexibility and the high costs of structural defense works, make to an attractive alternative to mitigate the risk of debris flow events.
Current early warning systems, based on sensors detecting the passage of the debris flow, allow short warning times, because debris flow propagation speed can reach up to 10 m/s. These time spans is enough to close a road, but not to evacuate people, especially at night. The aim of the project is to develop an Innovative early warning system for debris flow events based on nowcasting and phenomenology which aims to recognize debris flow events with greater time advances, linking nowcasting (1-3 hours) with hydrological and trigger models. Based on the forecast precipitation, as output of the high resolution mathematical physical model INCA, the surface runoff is calculated by the hydrological model ZEMOKOST. The triggering and propagation model estimates the corresponding volume of mobilizable debris: if this amount exceeds a critical value or threshold value, the early warning system is activated. INADEF aims to develop an EWS-prototype which predict the hydrogeological phenomenon before it occurs and more in advance, thus providing the alarm in adequate times to take actions and implement measures to safeguard public safety.
The project activity – coordinated by the Lead Partner University of Udine (UNIUD) – is dedicated to the optimal management, control and reporting of project activities and costs, monitoring compliance with the previsions of the Partnership Agreement and the ERDF Financing Agreement (Fund European Regional Development Authority) signed between the Lead Partner and the Managing Authority (this one represented by the office for European integration of the Autonomous Province of Bolzano), as well as the Interreg VA Italy-Austria Cooperation Program. The Lead Partner assumes overall administrative and financial responsibility for the implementation of the project, coordinating the Partners and collaborating with them in monitoring and verifying the periodic progress of the planned activities and expenses. Furthermore, this activity includes the effective management of the relations between the various Partners and with the Program Authorities and the initiation and maintenance of effective communication and data exchange flows between the beneficiaries of the initiative, as well as the operations functional to the timely project reporting of expenses to First Level Controllers (FLC – First Level Control) and to the Managing Authority, with the request to the Program for the payment of the contributions due on the basis of the costs incurred and validated.
ARPAV is the leader of this strategic project activity which concerns the dissemination of the project objectives and results. The project is aimed at two different types of audiences:
- experts for debris flow hazard defence and workers, to whom the project activities will be presented and the innovative alarm system proposed, the forecasting and warning criteria and the dynamics of debris flows reiterated;
- stakeholders, primarily municipal administrations and citizens, to whom the forecasting and warning criteria and the dynamics of debris flows will be presented.
During the meetings, the project website will also be presented, with its structure and expected contents.
At the end of the project, final meetings will be held with the local population and stakeholders and with the technicians responsible for the defense of the territory, to show the results of the project, differentiating the issues addressed. Participation in the meeting with the technicians responsible for the defense of the territory will be extended to the other regions of the Alps. The external meetings for the population will be publicized through notices and leaflets to be distributed in the settlements threatened by debris flow and in the neighboring ones, while the internal ones for the technicians responsible through official invitations of the territory to the alpine bodies of the whole area.
In this project activity, whose Leader is UNIUD, the webGIS integrates the information deriving from the various operating models on a platform in order to obtain a forecast of the magnitude (volume) of debris flows. In particular, the webGIS application is developed in such a way as to receive the precipitation forecast data arriving from INCA and subsequently run ZEMOKOST and the triggering and propagation model of debris flows. The different models need to be harmonized with respect to the format, so that the results of one model can be the input data of the next. In this case, the model output of the precipitation forecast will constitute the input of precipitation runoff and the results deriving from the modelling of the hydrological model will constitute the input data of the triggering and propagation model of the debris flows.
A fundamental activity of the project – coordinated by the University of Padua (UNIPD) which has a great and long field experience – is the monitoring of debris flows and the estimation of the volume of sediments they carry, in order to obtain the necessary data to test the proposed innovative alarm system. The basins of the Moscardo creek (Friuli), Rovina di Cancia and rio Rudan (Veneto), Bettelwurfmure and Gröbentalbach, frequently subject to debris flow phenomena, are the sites chosen for the monitoring activity in the field. This activity is carried out primarily in the measurement, with rain gauges, of the cumulative rainfall and the intensity of precipitation (or precipitation rate), in a defined time interval, capable of triggering the debris flow phenomenon. Then there are partly the sensors that measure the depth of the flow and sensors such as the tripwires that allow to detect the passage of a debris flow Other sensors are the geophones which have the advantage of not being in contact with the debris flow but they need to be properly calibrated. Furthermore, some video cameras are placed in the trigger area and in strategic points along debris flow channel, so as to be able to view the dynamics.
The monitoring activities are complemented by geological, topographic, morphological, sedimentological and land use surveys, necessary for the use of precipitation runoff and trigger models.
Topographic surveys are performed at the beginning and after each debris flow event to determine the volume of sediment mobilized and transported. Finally, data relating to historical events of debris flows (precipitation and volume of sediment transported) occurred in the basins are collected.
This activity, whose leader is BFW – Bundesforschungszentrum für Wald – concerns the testing of the webGIS application (or the new early warning system) at each test site using both the historical documentation and the data obtained from monitoring debris flow events during the project period. In particular, an evaluation matrix (alert/event) will be drawn up for all observed events. In addition, the timing of the events that occurred, the discharge observed before the generation of the debris flows and the volume of sediment transported will be compared with the results of the individual models for each debris flow event that occurred during the project and as far as possible also for the historical events with documentation. Based on these tests, efficiency of the entire system will be evaluated by seeking its optimization. The interface and data transfer from the external server on which run the nowcast model and the webGIS application together with the implementation of the precipitation runoff and triggering models will be evaluated based on the transfer times of the data and calculation. The results of the short-term precipitation forecast (1, 2 and 3 h) will be checked to determine an optimal warning timing that minimizes the number of false alarms and that is as extensive as possible because longer times allow a significant improvement in the management of civil protection actions. The results of the application will be further validated by comparison with an existing warning system based on a statistical approach developed by ZAMG. Last but not least, the possibility of operational use of the proposed system will be discussed and adapted through an iterative process that satisfy the requirements of the stakeholders.