1,721,151 research outputs found
Landslide volumes and landslide mobilization rates in Umbria, central Italy
No full textA catalogue of 677 landslides of the slide type was selected from a global database of geometrical measurements of individual landslides, including landslide area (AL) and volume (VL). The measurements were used to establish an empirical relationship to link AL (in m2) to VL (in m3). The relationship takes the form of a power law with a scaling exponent α = 1.450, covers eight orders of magnitude of AL and twelve orders of magnitude of VL, and is in general agreement with existing relationships published in the literature. The reduced scatter of the experiential data around the dependency line, and the fact that the considered landslides occurred in multiple physiographic and climatic environments and were caused by different triggers, indicate that the relationship between VL and AL is largely independent of the physiographical setting. The new relationship was used to determine the volume of individual landslides of the slide type in the Collazzone area, central Italy, a 78.9 km2 area for which a multi-temporal landslide inventory covering the 69-year period from 1937 to 2005 is available. In the observation period, the total volume of landslide material was VLT = 4.78 × 107 m3, corresponding to an average rate of landslide mobilization φL = 8.8 mm yr− 1. Exploiting the temporal information in the landslide inventory, the volume of material produced during different periods by new and reactivated landslides was singled out. The wet period from 1937 to 1941 was recognized as an episode of accelerated landslide production. During this 5-year period, approximately 45% of the total landslide material inventoried in the Collazzone area was produced, corresponding to an average rate of landslide mobilization φL = 54 mm yr− 1, six times higher than the long term rate. The volume of landslide material in an event or period was used as a proxy for the magnitude of the event or period, defined as the logarithm (base 10) of the total landslide volume produced during the event, or period. With this respect, the new relationship to link AL and VL is a starting point for the adoption of a quantitative, process based landslide magnitude scale for landslide events
Remote sensing precipitation data to determine rainfall thresholds for the possible occurance of landslides in central Italy.
No full textWe defined rainfall thresholds for possible landslide occurrence in central Italy using remote sensing precipitation data. For the purpose, we used 3-hour cumulated rainfall on a 0.25° 0.25° grid provided by NASA. We compared the thresholds with thresholds defined for the same area using rainfall measurements obtained from a network of 154 rain gauges in central Italy. For each rainfall event that has resulted in one or more landslides in the period 2002-2010, we calculated the cumulated rainfall E (mm) and the duration D (h) of the rainfall event. We compiled two data sets of empirical rainfall conditions (D, E) obtained from the rain gauge measurements
and the remote sensing precipitation data. Using this information, we defined two different ED thresholds, for rain gauge measurements and for the remote sensing estimates. To define the thresholds, we adopted a Frequentist probabilistic method that assumes that the threshold curve is a power law E = D, where E is the cumulated
rainfall (mm), D is the duration of the rainfall event (h), is a scaling constant (the intercept), and is the slope of the power law curve. We defined rainfall thresholds corresponding to an exceedance probability of 5% for the remote sensing data T5S,and for the rain gauge measurements T5R. Inspection of the two thresholds shows that
the threshold curves have a similar scaling exponent, with T5S exhibiting a lower intercept . We conclude that, in the study area, the cumulated rainfall required to initiate landslides estimated using the remote sensing precipitation data is persistently lower than the cumulated rainfall measured by the rain gauges. The result is significant. The two thresholds have a similar slope and this suggests that remote sensing precipitation data can be used to obtain rainfall thresholds for the possible occurrence of landslides. This can be useful in areas where rain gauge measurements are insufficient, or inexistent
LEWS2020 workshop on regional Landslide Early Warning Systems – experiences, progresses and needs
No full textClimate anomalies associated with the occurrence of rockfalls at high-elevation in the Italian Alps
Full text linkClimate change is seriously affecting the cryosphere in
terms, for example, of permafrost thaw, alteration of rain ∕ snow ratio, and
glacier shrinkage. There is concern about the increasing number of rockfalls
at high elevation in the last decades. Nevertheless, the exact role of
climate parameters in slope instability at high elevation has not been fully
explored yet. In this paper, we investigate 41 rockfalls listed in different
sources (newspapers, technical reports, and CNR IRPI archive) in the
elevation range 1500–4200 m a.s.l. in the Italian Alps between 1997 and 2013
in the absence of an evident trigger. We apply and improve an existing
data-based statistical approach to detect the anomalies of climate
parameters (temperature and precipitation) associated with rockfall
occurrences. The identified climate anomalies have been related to the
spatiotemporal distribution of the events. Rockfalls occurred in
association with significant temperature anomalies in 83 % of our case
studies. Temperature represents a key factor contributing to slope failure
occurrence in different ways. As expected, warm temperatures accelerate
snowmelt and permafrost thaw; however, surprisingly, negative anomalies are
also often associated with slope failures. Interestingly, different regional
patterns emerge from the data: higher-than-average temperatures are often
associated with rockfalls in the Western Alps, while in the Eastern Alps slope
failures are mainly associated with colder-than-average temperatures
Rainfall thresholds for the initiation of landslides in central Italy using remote sensing precipitation data.
No full textWe used remote sensing data to define new rainfall thresholds for the possible occurrence of landslides in Marche and Umbria regions, central Ital y. Remote sensing data are provided b y NASA and the estimated rainfall is cumulated every three hours in a regular grid of 0.25° × 0.25°. We exploited a catalogue of temporal and spatial information on landslides triggered by rainfall in the study area in the period 2002-2010. For each slope failure in the catalogue, we calculated the cumulated rainfall E (mm) and the duration D (h) of each rainfall event that triggered one or more landslide, using both remote sensing data and measurements obtained from a rain-gauge network. The rain-gauge network in the study area includes 123 stations and the rainfall is cumulated every hour. Finally, we obtained two data sets of empirical rainfall conditions (D, E) that triggered landslides and we defined the corresponding rainfall thresholds for remote sensing data and for rain gauge data. We used a Frequentist method and assumed that the threshold curve is a power law E =alfax D^gamma, where alfa is a scaling constant (the intercept) and gamma is the shape parameter that defines the slope of the power law curve. This method allows to define rainfall threshold corresponding to different exceedance probabilities. We observed that the threshold for remote sensing data is permanently lower than the threshold obtained with rain-gauge measurements. Finally, we found a relationship between the two thresholds. This is important because it permits the use of sensing precipitation data to obtain rainfall thresholds for the possible occurrence of landslides in those areas where rain gauge measurements are insufficient, or inexistent
Probabilistic clustering of rainfall condition for landslide triggering.
No full textHere we present a new fully automatic method to identify the probability of landslide occurrence associated to rainfall conditions characterized by measures of intensity or cumulative rainfall and rainfall duration. The method splits the rainfall events of the past in two groups: a group of events causing landslides and its complementary, then estimate their
probabilistic distributions.
The proposed approach can be conveniently integrated in existing early-warning system to improve the accuracy of the estimation of the real landslide occurrence probability associated to rainfall events and its uncertainty
A new landslide area-to-volume relationship, and its application to the evaluation of landslide volumes and to the evaluation of landslide volume rates.
No full textLandslides are complex phenomena influenced by multiple factors. Knowing the number, area, and volume of landslides is important to determine landslide hazard and risk and to evaluate the long-term evolution of landscapes dominated by mass-wasting processes. The number and area of individual landslides and the total landslide area in a region can be computed from accurate digital landslide inventory maps. Determining the volume of a landslide is a more difficult task that requires information on the surface geometry of the slope failure. Determining the volume of slope failures for large populations of landslides is an even more difficult task that can be achieved adopting empirical relationships to link the volume of individual landslides to geometrical measures of the landslides. A catalogue of 677 mass movements of the slide type, from a global database of geometrical measurements of individual landslides, including landslide area (AL) and volume (VL), were used to determine a relationship linking landslide area to landslide volume. The relationship takes the form of a power law with a scaling exponent α = 1.450. We exploited the relationship to evaluate the volume of landslide material produced in the Collazzone area, Central Italy, in the period from about 1937 to 2005. The study area extends for 78.9 square kilometres, and a detailed multi-temporal landslide inventory map of the area, covering the period 1937-2005, shows 2543 landslides, for a total mapped landslide area of 10.43*106 m2. Using the landslide information and the area-to-volume relationship, we calculated the volume of the single landslides, we evaluated the total volume of landslide material and the average rate of landslide mobilization and we exploited the temporal information in the landslide inventory to estimate the volume of material produced during different periods by new and reactivated landslides
Rainfall thresholds for the possible initiation of shallow landslides in the Italian Alps
No full textAbstract Rainfall-induced shallow landslides are frequent in the Italian Alps, where they cause severe economic damages and loss of life. The prediction of rainfall-induced slope failures is of utmost importance for civil protection purposes and relies upon the definition of physically based or empirical rainfall thresholds. Reliable empirical rainfall thresholds require a large amount of information on the geographical and temporal location of past rainfall events that caused the observed mass movements. We have compiled a catalogue listing 453 rainfall events that have triggered landslides in the Italian Alps in the 13-year period 2000-2012. For the purpose, we searched national and local newspapers, blogs, technical reports, historical databases, and scientific journals. In the catalogue, for each rainfall event that triggered one or more failures, the information includes: (i) landslide geographical position, (ii) date of the landslide occurrence, (iii) landslide type (if available from the source of information), and (iv) rainfall information. Using the available information, we calculated the cumulated amount (E) and the duration (D) of the rainfall that likely caused the documented slope failures. We exploited the catalogue to calculate new ED threshold curves and their associated uncertainties for the Italian Alps adopting a frequentist approach. To define seasonal rainfall thresholds, we also investigated the monthly distribution of the landslides. The new thresholds are compared with similar curves in the same general area. We expect the results of our study to improve the ability to forecast shallow landslides in the Italian Alps and, more generally, in the wider Alpine regio
Definition and performance of a threshold-based regional early warning model for rainfall-induced landslides
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