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| Titel |
Shallow landslide stability computation using a distributed transient response model for susceptibility assessment and validation. A case study from Ribeira Quente valley (S. Miguel island, Azores) |
| VerfasserIn |
P. Amaral, R. Marques, J. L. Zêzere, F. Marques, G. Queiroz |
| Konferenz |
EGU General Assembly 2009
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 11 (2009) |
| Datensatznummer |
250028677
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| Zusammenfassung |
| In the last 15 years, several heavy rainstorms have occurred in Povoação County (S. Miguel
Island, Azores), namely in the Ribeira Quente Valley. These rainfall events have triggered
hundreds of shallow landslides that killed tens of people and have been responsible for
direct and indirect damages amounting to tens of millions of Euros. On the 6th
March 2005 an intense rainfall episode, up to 160 mm of rain in less than 24 h,
triggered several shallow landslides that caused 3 victims and damaged/blocked
roads.
The Ribeira Quente Valley has an area of about 9.5 km2 and is mainly constituted by
pyroclastic materials (pumice ash and lapilli), that were produced by the Furnas Volcano
explosive eruptions.
To provide an assessment of slope-failure conditions for the 6th March 2005
rainfall event, it was applied a distributed transient response model for slope stability
analysis. The adopted methodology is a modified version of Iverson´s (2000) transient
response model, which couple an infinite slope stability analysis with an analytic
solution of the Richard‘s equation for vertical water infiltration in quasi-saturated
soil.
The validation was made on two different scales: (1) at a slope scale, using two distinct
test sites where landslides were triggered; and (2) at the basin scale, using the entire landslide
database and generalizing the modeling input parameters for the regional spatialization of
results. At the slope scale, the obtained results were very accurate, and it was possible to
predict the precise time of the slope failures. At the basin scale, the obtained results
were very conservative, even though the model predicted all the observed landslide
locations, in the 23.7% of the area classified as untable at the time of the slope
failures.
This methodology revealed to be a reasonable tool for landslide forecast for both temporal
and spatial distributions, on both slope and regional scales. In the future, the model
components will be integrated into a GIS based system that will publish the FS values to a
WebGIS platform, based on near real time ground-based rainfall monitoring. This application
will allow the evaluation of scenarios considering the variation of the pressure head response,
related to transient rainfall regime. The resultant computational platform combined with
regional empirical rainfall triggered landslides threshold (Marques et al. 2008) can be
incorporated in a common server with the Regional Civil Protection for emergency planning
purposes.
This work is part of the project VOLCSOILRISK (Volcanic Soils Geotechnical
Characterization for Landslide Risk Mitigation), supported by Direcção Regional da Ciência
e Tecnologia do Governo Regional dos Açores.
References:
IVERSON, R.M. (2000) - Landslide triggering by rain infiltration. Water Resources
Research 36, 1897–1910.
MARQUES, R., ZÊZERE, J.L., TRIGO, R., GASPAR, J.L., TRIGO, I. (2008) - Rainfall
patterns and critical values associated with landslides in Povoação County (São Miguel
Island, Azores): relationships with the North Atlantic Oscillation. Hydrol. Process. 22,
478-494. DOI: 10.1002/hyp.6879. |
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