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Changing debris flow activity after sudden sediment input: a case study from the Swiss Alps
Author(s) -
Baer Patrick,
Huggel Christian,
McArdell Brian W.,
Frank Florian
Publication year - 2017
Publication title -
geology today
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.188
H-Index - 17
eISSN - 1365-2451
pISSN - 0266-6979
DOI - 10.1111/gto.12211
Subject(s) - debris flow , debris , geology , sediment , hydrology (agriculture) , flow (mathematics) , magnitude (astronomy) , hyperconcentrated flow , period (music) , physical geography , geomorphology , sediment transport , oceanography , geotechnical engineering , geography , bed load , physics , geometry , mathematics , astronomy , acoustics
On 27 December 2011, a rock avalanche in the upper Val Bondasca in the southern Swiss Alps deposited 1.5–1.7 million m 3 of rock debris. The following summer, debris flow activity in Val Bondasca was unusually high with four events after a 90‐year period of debris flow inactivity. This was an exceptional situation for the valley. Analysing the 2012 events, the long‐term record of meteorological conditions such as rainfall intensity and duration, in comparison with debris flow activity, suggests that the meteorological conditions in summer 2012 would not have triggered the high intensity debris flow events without additional sediment input. Consequently, the suddenly increased debris availability can be considered a major factor in these events. Interestingly, rainfall events of similar magnitude in the subsequent years 2013–2015 did not trigger additional debris flow events, indicating that debris flow initiation thresholds are increasing again, back towards pre‐rock avalanche levels. This study aims to help in understanding the so far poorly understood temporal evolution of debris flow triggering thresholds and the effect of sudden changes in sediment availability.