 |
| Titel |
Rockfall hazard and risk assessment in the Yosemite Valley, California, USA |
| VerfasserIn |
F. Guzzetti, P. Reichenbach, G. F. Wieczorek |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1561-8633
|
| Digitales Dokument |
URL |
| Erschienen |
In: Natural Hazards and Earth System Science ; 3, no. 6 ; Nr. 3, no. 6, S.491-503 |
| Datensatznummer |
250001306
|
| Publikation (Nr.) |
 copernicus.org/nhess-3-491-2003.pdf |
|
|
|
|
|
| Zusammenfassung |
| Rock slides and rock
falls are the most frequent types of slope movements in Yosemite National
Park, California. In historical time (1857–2002) 392 rock falls and rock
slides have been documented in the valley, and some of them have been
mapped in detail. We present the results of an attempt to assess rock fall
hazards in the Yosemite Valley. Spatial and temporal aspects of rock falls
hazard are considered. A detailed inventory of slope movements covering
the 145-year period from 1857 to 2002 is used to determine the
frequency-volume statistics of rock falls and to estimate the annual
frequency of rock falls, providing the temporal component of rock fall
hazard. The extent of the areas potentially subject to rock fall hazards
in the Yosemite Valley were obtained using STONE, a physically-based rock
fall simulation computer program. The software computes 3-dimensional rock
fall trajectories starting from a digital elevation model (DEM), the
location of rock fall release points, and maps of the dynamic rolling
friction coefficient and of the coefficients of normal and tangential
energy restitution. For each DEM cell the software calculates the number
of rock falls passing through the cell, the maximum rock fall velocity and
the maximum flying height. For the Yosemite Valley, a DEM with a ground
resolution of 10 × 10 m was prepared using topographic contour lines from
the U.S. Geological Survey 1:24 000-scale maps. Rock fall release points
were identified as DEM cells having a slope steeper than 60°,
an assumption based on the location of historical rock falls. Maps of the
normal and tangential energy restitution coefficients and of the rolling
friction coefficient were produced from a surficial geologic map. The
availability of historical rock falls mapped in detail allowed us to check
the computer program performance and to calibrate the model parameters.
Visual and statistical comparison of the model results with the mapped
rock falls confirmed the accuracy of the model. The model results are
compared with a previous map of rockfall talus and with a geomorphic
assessment of rock fall hazard based on potential energy referred to as a
shadow angle approach, recently completed for the Yosemite Valley. The
model results are then used to identify the roads and trails more subject
to rock fall hazard. Of the 166.5 km of roads and trails in the Yosemite
Valley 31.2% were found to be potentially subject to rock fall hazard, of
which 14% are subject to very high hazard. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|