Giulia Bossi

A web-based platform for automatic and continuous landslide monitoring: The Rotolon (Eastern Italian Alps) case study

In the Small Dolomites group (Eastern Italian Alps), the Rotolon catchment is affected by a landslide that historically threatened the nearby village of Recoaro Terme. After the last re-activation on November 2010, the need to deploy devices to monitor deformations on the unstable slope became of paramount importance. This paper deals with the methodology, the techniques and the integrated services adopted for the design and the realization of a web-based platform for automatic and continuous monitoring of the Rotolon landslide. The choice of a web environment simplifies data collection, while a remote control permits technical maintenance and calibration on instruments and sensors in the field. Data management is straightforward on a single server, with the dataset being continuously updated. There is a user-friendly web interface which allows a practical up-to-date solution for decision-makers. This web-based monitoring platform represents the first step in the implementation of a complete early warning system. We design a multi-source and web-based platform for automatic and continuous monitoring.A user-friendly web interface allows a practical up-to-date solution for decision-makers.A better knowledge of the processes improves the quality of research.The framework is open and supported for custom requests.

A Land-Use Perspective for Birdstrike Risk Assessment: The Attraction Risk Index

Collisions between aircraft and birds, birdstrikes, pose a serious threat to aviation safety. The occurrence of these events is influenced by land-uses in the surroundings of airports. Airports located in the same region might have different trends for birdstrike risk, due to differences in the surrounding habitats. Here we developed a quantitative tool that assesses the risk of birdstrike based on the habitats within a 13-km buffer from the airport. For this purpose, we developed Generalized Linear Models (GLMs) with binomial distribution to estimate the contribution of habitats to wildlife use of the study area, depending on season. These GLMs predictions were combined to the flight altitude of birds within the 13-km buffer, the airport traffic pattern and the severity indices associated with impacts. Our approach was developed at Venice Marco Polo International airport (VCE), located in northeast Italy and then tested at Treviso Antonio Canova International airport (TSF), which is 20 km inland. Results from the two airports revealed that both the surrounding habitats and the season had a significant influence to the pattern of risk. With regard to VCE, agricultural fields, wetlands and urban areas contributed most to the presence of birds in the study area. Furthermore, the key role of distance of land-uses from the airport on the probability of presence of birds was highlighted. The reliability of developed risk index was demonstrated since at VCE it was significantly correlated with bird strike rate. This study emphasizes the importance of the territory near airports and the wildlife use of its habitats, as factors in need of consideration for birdstrike risk assessment procedures. Information on the contribution of habitats in attracting birds, depending on season, can be used by airport managers and local authorities to plan specific interventions in the study area in order to lower the risk.

Evaluating data quality collected by volunteers for first-level inspection of hydraulic structures in mountain catchments

Volunteers have been trained to perform first-level inspections of hydraulic structures within campaigns promoted by civil protection of Friuli Venezia Giulia (Italy). Two inspection forms and a learning session were prepared to standardize data collection on the functional status of bridges and check dams. In all, 11 technicians and 25 volunteers inspected a maximum of six structures in Pontebba, a mountain community within the Fella Basin. Volunteers included civil-protection volunteers, geosciences and social sciences students. Some participants carried out the inspection without attending the learning session. Thus, we used the mode of technicians in the learning group to distinguish accuracy levels between volunteers and technicians. Data quality was assessed by their accuracy, precision and completeness. We assigned ordinal scores to the rating scales in order to get an indication of the structure status. We also considered performance and feedback of participants to identify corrective actions in survey procedures. Results showed that volunteers could perform comparably to technicians, but only with a given range in precision. However, a completeness ratio (question / parameter) was still needed any time volunteers used unspecified options. Then, volunteers’ ratings could be considered as preliminary assessments without replacing other procedures. Future research should consider advantages of mobile applications for data-collection methods.

A new data assimilation procedure to develop a debris flow run-out model

Parameter calibration is one of the most problematic phases of numerical modeling since the choice of parameters affects the model’s reliability as far as the physical problems being studied are concerned. In some cases, laboratory tests or physical models evaluating model parameters cannot be completed and other strategies must be adopted; numerical models reproducing debris flow propagation are one of these. Since scale problems affect the reproduction of real debris flows in the laboratory or specific tests used to determine rheological parameters, calibration is usually carried out by comparing in a subjective way only a few parameters, such as the heights of soil deposits calculated for some sections of the debris flows or the distance traveled by the debris flows using the values detected in situ after an event has occurred. Since no automatic or objective procedure has as yet been produced, this paper presents a numerical procedure based on the application of a statistical algorithm, which makes it possible to define, without ambiguities, the best parameter set. The procedure has been applied to a study case for which digital elevation models of both before and after an important event exist, implicating that a good database for applying the method was available. Its application has uncovered insights to better understand debris flows and related phenomena.

The Rotolon Catchment Early-Warning System

Severe instability processes have affected the Rotolon catchment (Eastern Italian Alps) for long time. The first written proof of a landslide occurrence dates back to 1798. The last re-activation occurred in November 2010 when, after a cumulative rainfall of 637 mm in 12 days, a mass of approximately 320,000 m3 detached from the unstable slope and evolved into a debris flow that ran for about 4 km along the channel, threatening the villages along the stream. Since then, the design and the implementation of an early-warning system was considered of primary importance, in order to mitigate the risk for the valley inhabitants. A monitoring network consisting of 42 topographic benchmarks and 6 wire extensometers was installed and a warning system was deployed along four sections of the channel. The latter consists of 3 pendulum sections and a trip-wire section. Alarm sirens installed near the settlements are activated when the warning system is triggered by a debris-flow event, guaranteeing some minutes lead time to the local population. In this way the inhabitants could evacuate in time and reach safe areas thus reducing the risk. A Decision Support System (DSS) is also integrated with the deployed sensors, therefore technicians may support crisis response with a user-friendly instrument.

Clustering sediment connectivity maps to distinguish hillslope processes

The availability of increasingly higher resolution Digital Terrain Models (DTMs) allows to perform a detailed characterization of the morphological features on selected areas of interest. There is a growing interest, within the scientific community, for automatic DTM-based procedures to extract geomorphological features or to model surface processes. Among these, the Index of sediment Connectivity (IC), which estimates the degree of linkage that controls sediment fluxes throughout landscape, and, in particular, between sediment sources and downstream areas, has proved to be a powerful morphometric tool. In particular, IC may be used to better portray and highlight sediment dynamics and pathways at catchment scale. In this work, we compare IC maps for two alpine areas. The first area is a typical debris-flow catchment, while the second areais characterized by the presence of a large deep-seated gravitational slope deformation. Two types of numerical analysis are presented:i) the aggregation and normalization of the IC values and ii) cluster analysis. Our preliminary results show that the spatial information, which is maintained in the cluster analysis and lost in the aggregate procedure, is extremely valuable for the identification and the clustering of areas that are affected by the same predominant geomorphological process.

Applicability of Two Propagation Models to Simulate the Rotolon Earth-Flow Occurred in November 2010

Since 1920, recurrent collapses and earth-flows have interested the Rotolon torrent. The last one occurred in November 2010 when about 320,000 m3 detached in the triggering zone and flowed for more than 4 km. This paper deals with the calibration of two numerical models developed for the analysis of flow-like landslide propagation, both using SPH as computational method. For describing the flowing mass behavior it was adopted the Voellmy rheological model calibrated on the base of two LiDAR surveys captured just before and after the event.

Landslide monitoring with an integrated platform: methodology, design and case study

Landslide monitoring is usually linked to a complex physical system with several parameters and uncertainties. Different instruments are located and set up on field, but a simple, continuous and efficient integration is compulsory for an acceptable warning support.The South-East flank of Mount Carega (Eastern Italian Alps) is affected by a complex landslide that, since 1985, is threatening Recoaro Terme. After the last re-activation on November 2010 (637 mm of intense rainfall recorded in the 12 days prior the event), a mass of approximately 320.000 m3 detached from the flank of Mount Carega and evolved into a fast debris flow that ran for about 4 km along the stream bed.A real-time monitoring system was required to detect early indication of rapid movements, potentially saving lives and property. A web-based platform for automatic and continuous monitoring was designed as a first step in the implementation of an early-warning system. Measurements collected by the automated geotechnical and topographic instrumentation, deployed over the landslide body, are gathered in a central acquisition unit. After the calibration process, data are transmitted by web services on a local server, where graphs, maps, reports and alert announcement are automatically generated and updated. All the processed information is available by web browser with different access rights.

Alpine landslide risk scenario: run-out modelling using a 3D approach

Rockslides of considerable volume developing on the flanks of narrow alpine valleys represent a significant hazard for the potential of river damming and consequent sudden discharge of water.A limestone rock mass of about 650,000 m3 endangers a portion of the upper course of Tagliamento River valley in north-eastern Italy.This section of the valley is prone to detachment of rock landslides due to its structural setting and it has a history of landslide damming: in the literature two huge events are widely documented and a third event is identified and described in this paper. The ancient detachment crown and the corresponding deposit can be observed in the portion of slope adjacent to the unstable rock mass.This paper deals with the run-out model of the unstable rock mass using a Smoothed Particles Hydrodynamics (SPH) model implemented in the DAN3D code. In order to select the appropriatematerial parameters, the ancient rockslide was back-analysed. Subsequently, the parameters were applied to the present unstable portion of the slope to determine the location and dimensions of the deposit that could be formed.It is demonstrated that the deposit has the potential to create a natural dam across the Tagliamento River that would form a 500,000 m3 lake. Although the lake will have limited dimensions, this would represent a very high risk for the downstream villages and infrastructures in case of a sudden collapse of the natural dam.

Capabilities of Continuous and Discontinuous Modelling of a Complex, Structurally Controlled Landslide

In order to assess the stability of a landslide, continuous or discontinuous models have been proposed. Here, we compare the two methods in their capability to provide a reliable hazard assessment. Both models have been applied to long term monitoring data obtained from a landslide located in Passo della Morte (Eastern Italian Alps). The availability of accurate data obtained in a long-term campaign is a pre-requisite to correctly understand the dynamics of the process and to implement a sound numerical model. First, a detailed geological investigation located the different soil layers and rock formations with their distribution along the slope, allowing the identification of the structural controls of the unstable rock mass. Then, landslide long term monitoring data provided information on the type of failure mechanism. Both the continuous and discontinuous numerical solutions describe the kinematics for the landslide and allow to delineate a hazard assessment for the investigated area. The continuous model is better in delineating the development of the deep slip surface while the discontinuous allows to recreate the toppling phenomenon.