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Alluvial cutoffs as indicators of former channel conditions

 

作者: Wayne Erskine,   Christopher McFadden,   Paul Bishop,  

 

期刊: Earth Surface Processes and Landforms  (WILEY Available online 1992)
卷期: Volume 17, issue 1  

页码: 23-37

 

ISSN:0197-9337

 

年代: 1992

 

DOI:10.1002/esp.3290170103

 

出版商: John Wiley&Sons, Ltd

 

关键词: Alluvial cutoff;Floods;Australia;Fluvial geomorphology;Floodplain

 

数据来源: WILEY

 

摘要:

AbstractAlthough alluvial cutoffs record accurately the geometry, bedforms, and bed material of the channel when last active, few attempts have been made to use cutoffs in studies of channel changes. A detailed record of historical channel changes on the lower Hunter River in southeastern Australia has shown that this channel responds to naturally alternating periods of high and low flood activity, called flood‐ and drought‐dominated regimes respectively. Sinuosity decreased from 3·84 in 1870, to 2·66 in 1893 and to 1·38 in 1970 through the development of eight cutoffs. The channel also aggraded with medium sand burying the former bed material of mixed mud, coarse sand, and gravel. Channel straightening was a response to increased flood frequencies during the flood‐dominated regimes of the late 19th and 20th centuries, combined with localized river engineering works and increased sand load.Detailed stratigraphic studies were carried out on three neck cutoffs and one chute cutoff which were abandoned in 1890, 1950, 1952, and 1956. A comparison of former and present bed elevations and bed material size showed similar trends to those determined by the historical record, confirming the reliability of cutoffs as indicators of former channel conditions.The sedimentary infills of the cutoffs are not uniformly fine grained as recorded previously in the literature. Relatively thin, fine‐grained fills were deposited during the drought‐dominated regime of the first half of this century but thick, coarser‐grained fills were deposited after 1949 during the flood‐dominated regime. All fills fine upwards. Cutoff infills provide a record of changing flood activity an

 

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