Multi-scale debris flow vulnerability assessment and direct loss estimation of buildings in the Eastern Italian Alps

Many-objective optimization methods have proven successful in the integration of research attributes demanded for urban vulnerability assessment models. However, these techniques suffer from the curse of the dimensionality problem, producing an excessive burden in the decision-making process by compelling decision-makers to select alternatives among a large number of candidates. In other fields, this problem has been alleviated through cluster analysis, but there is still a lack in the application of such methods for urban vulnerability assessment purposes. This work addresses this gap by a novel combination of visual analytics and cluster analysis, enabling the decision-maker to select the set of indicators best representing urban vulnerability accordingly to three criteria: expert’s preferences, goodness of fit, and robustness. Based on an assessment framework previously developed, VisualUVAM affords an evaluation of urban vulnerability in Spain at regional, provincial, and municipal scales, whose results demonstrate the effect of the governmental structure of a territory over the vulnerability of the assessed entities.

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Vulnerability curves vs. vulnerability indicators: application of an indicator-based methodology for debris-flow hazards

Natural Hazards and Earth System Science ◽

10.5194/nhess-16-1771-2016 ◽

2016 ◽

Vol 16 (8) ◽

pp. 1771-1790 ◽

Cited By ~ 30

Author(s):

Maria Papathoma-Köhle

Keyword(s):

At Risk ◽

Debris Flow ◽

Vulnerability Assessment ◽

Structural Characteristics ◽

Physical Vulnerability ◽

Vulnerability Indicators ◽

Element At Risk ◽

Mountain Hazards ◽

Methodological Approaches

Abstract. The assessment of the physical vulnerability of elements at risk as part of the risk analysis is an essential aspect for the development of strategies and structural measures for risk reduction. Understanding, analysing and, if possible, quantifying physical vulnerability is a prerequisite for designing strategies and adopting tools for its reduction. The most common methods for assessing physical vulnerability are vulnerability matrices, vulnerability curves and vulnerability indicators; however, in most of the cases, these methods are used in a conflicting way rather than in combination. The article focuses on two of these methods: vulnerability curves and vulnerability indicators. Vulnerability curves express physical vulnerability as a function of the intensity of the process and the degree of loss, considering, in individual cases only, some structural characteristics of the affected buildings. However, a considerable amount of studies argue that vulnerability assessment should focus on the identification of these variables that influence the vulnerability of an element at risk (vulnerability indicators). In this study, an indicator-based methodology (IBM) for mountain hazards including debris flow (Kappes et al., 2012) is applied to a case study for debris flows in South Tyrol, where in the past a vulnerability curve has been developed. The relatively "new" indicator-based method is being scrutinised and recommendations for its improvement are outlined. The comparison of the two methodological approaches and their results is challenging since both methodological approaches deal with vulnerability in a different way. However, it is still possible to highlight their weaknesses and strengths, show clearly that both methodologies are necessary for the assessment of physical vulnerability and provide a preliminary "holistic methodological framework" for physical vulnerability assessment showing how the two approaches may be used in combination in the future.

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High-resolution seismic imaging of debris-flow fans, alluvial valley fills and hosting bedrock geometry in Vinschgau/Val Venosta, Eastern Italian Alps

Journal of Applied Geophysics ◽

10.1016/j.jappgeo.2018.07.001 ◽

2018 ◽

Vol 157 ◽

pp. 61-72 ◽

Cited By ~ 4

Author(s):

Stefano Maraio ◽

Pier Paolo G. Bruno ◽

Vincenzo Picotti ◽

Volkmar Mair ◽

Francesco Brardinoni

Keyword(s):

High Resolution ◽

Debris Flow ◽

Seismic Imaging ◽

Italian Alps ◽

Alluvial Valley ◽

Valley Fills

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Debris flow interaction with structures: challenges to traditional load models

10.5194/egusphere-egu2020-18157 ◽

2020 ◽

Author(s):

Alessandro Leonardi ◽

Andrea Pasqua ◽

Marina Pirulli

Keyword(s):

Debris Flow ◽

Relative Size ◽

Nonlinear Function ◽

Field Measurements ◽

Italian Alps ◽

Load Model ◽

Flow Energy ◽

Load Models ◽

Maintenance Work ◽

Flow Through

Debris flow barriers often feature one or more filter elements, i.e. narrow outlets that induce deposition of the coarsest sediments, while allowing water and fines to filter through. Slit dams and steel nets are examples of this type of barriers. The design of the filter elements must balance the need to trap boulders and to dissipate the flow energy, while keeping maintenance work as low as possible.Filter barriers elude the traditional load model prescribed by guidelines. Under some conditions, the outlets can clog with large boulders. The time necessary for this to happen mainly depends on the relative size between boulder and outlet, and is a nonlinear function of the flow composition. In any case, the main clogging mechanism is the formation of granular arches. These can induce significant load also in directions different from the main direction of the incoming flow.Unless the barrier is specifically designed to withstand this type of load, granular arches, but also prolonged flow through the outlet, can induce deterioration and loss of functionality of the structure. In this work, we estimate these effects employing a combination of discrete- and continuum-based numerical methods. We evaluate the performance of two types of debris-resisting barriers, comparing the results with laboratory measurements and with the outcome of a monitoring campaign on a real barrier located in the Italian alps.&#160;&#160;References:Leonardi, A., Goodwin, G. R., & Pirulli, M. (2019). The force exerted by granular flows on slit dams. Acta Geotechnica, 14(6), 1949&#8211;1963.Leonardi, A., & Pirulli, M. (2020). Analysis of the load exerted by debris flows on filter barriers : Comparison between numerical results and field measurements. Computer & Geotechnics, 118, 103311.

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Multi-parametric observations of debris-flow initiation at the headwaters of the Gadria catchment (eastern Italian Alps)

10.5194/egusphere-egu2020-8720 ◽

2020 ◽

Author(s):

Velio Coviello ◽

Matteo Berti ◽

Lorenzo Marchi ◽

Francesco Comiti ◽

Giulia Marchetti ◽

...

Keyword(s):

Soil Moisture ◽

Debris Flow ◽

Early Warning ◽

Debris Flows ◽

Lead Time ◽

Early Warning Systems ◽

Force Balance ◽

Italian Alps ◽

Alarm Systems ◽

Debris Flow Initiation

The complete understanding of the mechanisms controlling debris-flow initiation is still an open challenge in landslide research. Most debris-flow models assume that motion suddenly begins when a large force imbalance is imposed by slope instabilities or the substrate saturation that causes the collapse of the channel sediment cover. In the real world, the initiation of debris flows usually results from the perturbation of the static force balance that retains sediment masses in steep channels. These perturbations are primarily generated by the increasing runoff and by the progressive erosion of the deposits. Therefore, great part of regional early warning systems for debris flows are based on critical rainfall thresholds. However, these systems are affected by large spatial-temporal uncertainties due to the inadequate number and distribution of rain gauges. In addition, rainfall analysis alone does not explain the dynamics of sediment fluxes at the catchment scale: short-term variations in the sediment sources strongly influence the triggering of debris flows, even in catchments characterized by unlimited sediment supply.In this work, we present multi-parametric observations of debris flows at the headwaters of the Gadria catchment (eastern Italian Alps). In 2018, we installed a monitoring network composed of geophones, three soil moisture probes, one tensiometer and two rain-triggered videocameras in a 30-m wide steep channel located at about 2200 m a.s.l. Most sensors lie on the lateral ridges of this channel, except for the tensiometer and the soil moisture probes that are installed in the channel bed at different depths. This network recorded four flow events in two years, two of which occurred at night. Specifically, the debris flows that occurred on 21 July 2018 and 26 July 2019 produced remarkable geomorphic changes in the monitored channel, with up to 1-m deep erosion. For all events, we measured peak values of soil water content that are far from saturation (<0.25 at -20 cm, <0.15 at -40 cm, <0.1 at -60 cm). We derived the time of occurrence and the duration of these events from the analysis of the seismic signals. Combining these pieces of information with data gathered at the monitoring station located about 2 km downstream, we could determine the flow kinematics along the main channel.These results, although still preliminary, show the relevance of a multi-parametric detection of debris-flow initiation processes and may have valuable implications for risk management. Alarm systems for debris flows are becoming more and more attractive due the continuous development of compact and low-cost distributed sensor networks. The main challenge for operational alarm systems is the short lead-time, which is few tens of seconds for closing a transportation route or tens of minutes for evacuating settlements. Lead-time would significantly increase installing a detection system in the upper part of a catchment, where the debris flow initiates. The combination of hydro-meteorological monitoring in the source areas and seismic detection of channelized flows may be a reliable approach for developing an integrated early warning - alarm system.

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