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Field observations on hyperconcentrated flows in mountain torrents
Author(s) -
Batalla R. J.,
De Jong C.,
Ergenzinger P.,
Sala M.
Publication year - 1999
Publication title -
earth surface processes and landforms
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.294
H-Index - 127
eISSN - 1096-9837
pISSN - 0197-9337
DOI - 10.1002/(sici)1096-9837(199903)24:3<247::aid-esp961>3.0.co;2-1
Subject(s) - hyperconcentrated flow , tributary , hydrology (agriculture) , geology , sediment , flood myth , alluvial fan , debris , bed load , debris flow , structural basin , stream power , sediment transport , alluvium , channel (broadcasting) , colluvium , geomorphology , geotechnical engineering , philosophy , oceanography , cartography , theology , engineering , geography , electrical engineering
Field observations on hydraulics and sediment dynamics during extreme floods in two mountain torrents show the influence of man‐made constructions such as bridges and check dams, in addition to the sediment supplied naturally by the basin and the channel network, on the formation of hyperconcentrated flows. In the Pyrenean Arás basin, hyperconcentrated flow occurred after collapse of a bridge, which in turn mobilized large volumes of sediment from the stream channel and, subsequently, destroyed a series of check dams. Boulders up to several metres in size were transported in a mixture of sand and fine material. A minimum of 1 tonnes of sediment were deposited on the alluvial fan during the event. Prior to bridge destruction, mean bedload transport rates had reached 0.4t m −1 s −1 upstream. In the alpine Lainbach basin, the flood was characterized by transportation of large amounts of slope material, including debris flows. Along its main tributary an intensive hyperconcentrated flow occurred during the rising stage, whereas in the main valley smaller flows occurred after failure of check dams. The depth of coarse material deposited reached 80 cm. The effectiveness of the Aràs and Lainbach floods was attained due to exceptional rates of energy expediture. Flood power ranged from 20000 W m −2 to 40000 W m −2 on average. Copyright © 1999 John Wiley & Sons, Ltd.