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| Titel |
Using field data and HSR imagery to downscale vulnerability assessment of buildings and local infrastructure facing hazards from floods and hyperconcentrated flows |
| VerfasserIn |
Susanne Ettinger, Nélida Victoria Manrique Llerena, Jean-Claude Thouret |
| Konferenz |
EGU General Assembly 2014
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 16 (2014) |
| Datensatznummer |
250098311
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| Publikation (Nr.) |
 EGU/EGU2014-13978.pdf |
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| Zusammenfassung |
| The focus of this study is the analysis of post-flood conditions along the Venezuela channel in
the large city of Arequipa, south Peru, in order to identify the parameters determining
vulnerability of buildings and infrastructure. Two tributaries draining a c. 11.9 km2
large catchment feed the Venezuela channel. Before joining the main Rio Chili
valley to the West, it crosses the city from NE to SW. Over a total length of 5.2
km, channel depth ranges from 1.3 to 6.3 m and c. 40% of the channel sections do
not exceed 5 m in width. On 8 February 2013, 123 mm of rainfall within 3 hours
(monthly mean: 29.3 mm) triggered a flashflood inundating at least 0.4 km2 of
urban settlements along the channel. The flood damaged 14 buildings, 23 among 53
bridges, and led to the partial collapse of main road sections paralyzing central parts
of the city for at least one week. This research relies on (1) analyzing post-flood
conditions and assessing damage types caused by the 8 February 2013 flood; (2)
mapping of the channel characteristics (slope, wetted section, sinuosity, type of river
banks, bed roughness, etc.) and buildings, bridges, and contention walls potentially
exposed to inundation. Data collection and analysis have been based on high spatial
resolution (HSR) images (SPOT5 2007, Google Earth Pro and BINGMAP 2012,
PLEIADES 2012-2013). Field measurements (GPS, laser and geomorphologic
mapping) were used to ground truth channel width, depth, as well as building outlines,
contention walls and bridge characteristics (construction material, opening size, etc.). An
inventory of 25 city blocks (1500 to 20000 m2; 6 to 157 houses per block) has been
created in a GIS database in order to estimate their physical vulnerability. As many
as 717 buildings have been surveyed along the affected drainage and classified
according to four building types based on their structural characteristics. Output
vulnerability maps show that the varying channel characteristics, i.e. bank type, bed
roughness, and the variable width-depth ratio of rectangular or trapezoidal channel
sections determine in great part site-specific vulnerability. The sub-metric spatial
resolution and GIS data analysis using PLEIADES imagery has enabled vulnerability
assessment of individual features of few meters in size. However, this study shows that
fieldwork remains essential for (1) completing measurements in areas where channel
is < 5 m in width or partially hidden by 2-5-storey buildings; (2) assessing the
type and construction material of contention walls and thus their susceptibility
to fail after they are scoured; and (3) determining the opening height of bridges
potentially obstructing flow and leading to inundation as a consequence of overspill. |
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