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Titel |
Assessing the effects of check dams on sediment dynamics in a debris-flow catchment through SfM technique |
VerfasserIn |
Sara Cucchiaro, Alberto Beinat, Aleix Calsamiglia, Marco Cavalli, Federico Cazorzi, Stefano Crema, Lorenzo Marchi |
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 |
250137940
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Publikation (Nr.) |
EGU/EGU2017-815.pdf |
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Zusammenfassung |
The Moscardo Torrent (eastern Italian Alps) is a small rugged catchment (drainage area 4.1
km2, range in elevation between 890 and 2043 m) frequently affected by debris flows that
deliver large amounts of sediment to the receiving stream, and cause concerns for
infrastructures located on the alluvial fan and near the confluence.
Over the last decades, hydraulic control works were implemented in the main channel to
limit bed erosion and to stabilize channel banks. Although the objectives of training works
have been only partly achieved, check dams and hillslope stabilization works have
affected the sediment transfer from hillslopes to the channels and along the main
channel.
The effects of hydraulic control works were investigated by means of multi-temporal
Structure from Motion (SfM) surveys based on images taken from the ground and UAV. The
ground and air based surveys were carried out over a channel reach in which two check dams
have recently been built. SfM surveys were taken before and after three debris-flow events
(occurred between June and July 2016), allowing the generation of four high-resolution
Digital Elevation Models (DEMs).
Geomorphic changes caused by the debris-flow events have been assessed in order to
produce the DEM of Differences (DoDs with a 0.2 m spatial resolution) that allowed
estimating erosion and deposition volumes in the study area. Furthermore a debris-flow
monitoring system has been in operation in the Moscardo Torrent; the analysis of the videos
and of the hydrographs recorded by ultrasonic sensors permitted to assess the debris-flow
volumes. These estimates were used to characterize the magnitude of events in support of the
topographic analysis.
By examining the changing pattern of erosion and deposition over time it was possible to
understand the check dams’ effects on sediment dynamics. The results show that the new
check dams effectively stored sediment transported by the three debris flows. However, once
the check dams have been completely filled, they lost their functionality, letting sediment
flow downstream along paths drawn accidentally by the torrent control works and by the
morphology of debris-flow deposits. Moreover, debris-flow lobes deposited upstream of the
check dams could act as sediment sources further increasing downstream debris-flow
magnitude. |
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