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| Titel |
Integrated satellite InSAR and slope stability modeling to support hazard
assessment at the Safuna Alta glacial lake, Peru |
| VerfasserIn |
Alejo Cochachin, Holger Frey, Christian Huggel, Tazio Strozzi, Emanuel Büechi, Fanpeng Cui, Andrés Flores, Carlos Saito |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250150080
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| Publikation (Nr.) |
 EGU/EGU2017-14505.pdf |
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| Zusammenfassung |
| The Safuna glacial lakes (77˚ 37’ W, 08˚ 50’ S) are located in the headwater of the
Tayapampa catchment, in the northernmost part of the Cordillera Blanca, Peru. The upper
lake, Laguna Safuna Alta at 4354 m asl has formed in the 1960s behind a terminal moraine of
the retreating Pucajirca Glacier, named after the peak south of the lakes. Safuna Alta
currently has a volume of 15 x 106 m3.
In 2002 a rock fall of several million m3 from the proximal left lateral moraine hit the
Safuna Alta lake and triggered an impact wave which overtopped the moraine dam
and passed into the lower lake, Laguna Safuna Baja, which absorbed most of the
outburst flood from the upper lake, but nevertheless causing loss in cattle, degradation
of agricultural land downstream and damages to a hydroelectric power station in
Quitaracsa gorge. Event reconstructions showed that the impact wave in the Safuna
Alta lake had a runup height of 100 m or more, and weakened the moraine dam of
Safuna Alta. This fact, in combination with the large lake volumes and the continued
possibility for landslides from the left proximal moraine pose a considerable risk for the
downstream settlements as well as the recently completed Quitaracsa hydroelectric power
plant.
In the framework of a project funded by the European Space Agency (ESA), the hazard
situation at the Safuna Alta lake is assessed by a combination of satellite radar data analysis,
field investigations, and slope stability modeling. Interferometric analyses of the Synthetic
Aperture Radar (InSAR) of ALOS-1 Palsar-1, ALOS-2 Palsar-2 and Sentinel-1 data from
2016 reveal terrain displacements of 2 cm y−1 in the detachment zone of the 2002 rock
avalanche. More detailed insights into the characteristics of these terrain deformations are
gained by repeat surveys with differential GPS (DGPS) and tachymetric measurements. A
drone flight provides the information for the generation of a high-resolution digital
elevation model (DEM), which is used for the modeling of the geomechanical slope
stability using the W/Slope and UDEC models. Model application, however, is limited
due to data scarcity regarding geotechnical slope properties, which needed to be
estimated.
The combination of these data products, measurements and model results provide
important information for the estimation of potential source areas for future slope collapses
and involved volumes. Eventually, such information can be used for the definition of
possible rock avalanche scenarios and related chain reactions in order to elaborate
a hazard map for resulting lake outburst floods. At the same time, the potential
for an operational slope stability monitoring system at this site will be evaluated. |
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