弯曲河流颈口裁弯模式与机理
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摘要
为了揭示弯曲河流颈口裁弯的各种不同模式与内在复杂性,通过判读正裁弯和已裁弯的大量河湾遥感影像,将颈口裁弯分为3种不同力学模式,即崩岸模式、冲切模式和串沟模式,运用力学分析的方法探讨了不同裁弯模式的形成条件、过程与机理。崩岸模式是相当窄的颈口两侧河岸发生崩岸或单侧崩岸引起颈口上下游水流贯通。冲切模式是最普遍的颈口裁弯方式,其过程分为漫滩水流表面冲刷、形成沟槽后集中冲刷和沟槽达到稳定。串沟模式是初次洪水漫滩冲刷形成串沟,后续洪水沿串沟继续冲刷,且以溯源冲刷为主,直至形成新河槽。
Neck cutoff is a sudden event occurring in meandering rivers which reduces the sinuosity and complexity of the morphology.The patterns and mechanisms for neck cutoffs were analyzed in remote sensing images of neck cutoffs to divide the cutoffs into bank collapse,cutting and erosion patterns to theoretically investigate the cutoff conditions,processes and mechanisms.The bank collapse pattern occurs on extremely narrow necks where the left and right banks simultaneously collapse or a single bank collapse which forces the flow through the neck.The cutting pattern is the most common neck cutoff mechanism when overflow surface scouring forms a new channel and intensively scours the new channel until creating a stable channel.The erosion pattern is the first flood scouring that forms a ditch,with subsequent floods along the ditch scouring with headward erosion until a new channel is completely formed.
Neck cutoff is a sudden event occurring in meandering rivers which reduces the sinuosity and complexity of the morphology.The patterns and mechanisms for neck cutoffs were analyzed in remote sensing images of neck cutoffs to divide the cutoffs into bank collapse,cutting and erosion patterns to theoretically investigate the cutoff conditions,processes and mechanisms.The bank collapse pattern occurs on extremely narrow necks where the left and right banks simultaneously collapse or a single bank collapse which forces the flow through the neck.The cutting pattern is the most common neck cutoff mechanism when overflow surface scouring forms a new channel and intensively scours the new channel until creating a stable channel.The erosion pattern is the first flood scouring that forms a ditch,with subsequent floods along the ditch scouring with headward erosion until a new channel is completely formed.
引文
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[15]庞炳东.兴建三门峡水库后渭河下游河道自然裁弯的研究[J].泥沙研究,1986(4):37-49.PANG Bingdong.An investigation about natural cutoffs onthe lower reaches of the Wei River after the construction ofthe Sanmenxia reservoir[J].Journal of Sediment Research,1986(4):37-49.(in Chinese)
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[18]彭润泽,常德礼,白荣隆,等.推移质三角洲溯湖冲刷计算公式[J].泥沙研究,1981(1):14-29.PENG Runze,CHANG Deli,BAI Ronglong,et al.Formulasfor calculating headward erosion on a bed load delta[J].Journal of Sediment Research,1981(1):14-29.(in Chinese)
[2]Stlum H H.River meandering as a self-organization process[J].Science,1996,271(5256):1710-1713.
[3]Gay G R,Gay H H,Gay W H,et al.Evolution of cutoffsacross meander necks in Power River,Montana,USA[J].Earth Surface Processes and Landforms,1998,23(7):651-662.
[4]Camporeale C,Perucca E,Ridolfi L.Significance of cutoff inmeandering river dynamics[J].Journal of GeophysicalResearch,2008,113,doi:10.1029/2006JF000694.
[5]Constantine J A,Dunne T.Meaner cutoff and the controls onthe production of oxbow lakes[J].Geology,2008,36(1):23-26.
[6]Frascati A,Lanzoni S.Morphodynamic regime and long-termevolution of meandering rivers[J].Journal of GeophysicalResearch,2009,114,doi:10.1029/2008JF001101.
[7]Pittaluga M B,Nobile G,Seminara G.A nonlinear model forriver meandering[J].Water Resources Research,2009,45(W04432),doi:10.1029/2008WR007298.
[8]假冬冬,邵学军,王虹,等.荆江典型河湾河势变化三维数值模型[J].水利学报,2010,41(12):1451-1460.JIA Dongdong,SHAO Xuejun,WANG Hong,et al.A threedimensional mathematical modeling for the Jingjiang River[J].Journal of Hydraulic Engineering,2010,41(12):1451-1460.(in Chinese)
[9]Braudrick C A,Dietrich W E,Leverich G T,et al.Experimental evidence for the conditions necessary to sustainmeandering in coarse-bedded rivers[J].PNAS,2009,106(40):16936-16941.
[10]Zinger J A,Rhoads B L,Best J L.Extreme sediment pulsesgenerated by bend cutoffs along a large meandering river[J].Nature Geoscience,2011,4(10):675-678,doi:10.1038/NGEO1260.
[11]Hooke J M.Cutoffs galore!:Occurrence and causes ofmultiple cutoffs on a meandering river[J].Geomorphology,2004,61(3-4):225-238.
[12]Micheli E R,Larsen E W.River channel cutoff dynamics,Sacramento River,California,USA[J].River Research andApplications,2011,27(3):328-344.
[13]Parker G,Shimizu Y,Wilkerson G V,et al.A newframework for modeling the migration of meandering rivers[J].Earth Surface Processes and Landforms,2011,36(1):70-86.
[14]李志威,王兆印,李文哲.冲积河湾裁弯形式与几何临界形态[J].四川大学学报:工程科学版,2012,44(1):82-87.LI Zhiwei,WANG Zhaoyin,LI Wenzhe.Types andgeometrical critical form of cutoffs in meandering rivers[J].Journal of Sichuan University:Engineering ScienceEdition,2012,44(1):82-87.(in Chinese)
[15]庞炳东.兴建三门峡水库后渭河下游河道自然裁弯的研究[J].泥沙研究,1986(4):37-49.PANG Bingdong.An investigation about natural cutoffs onthe lower reaches of the Wei River after the construction ofthe Sanmenxia reservoir[J].Journal of Sediment Research,1986(4):37-49.(in Chinese)
[16]Osman A M,Thorne C R.Riverbank stability analysis I:Theory[J].Journal of Hydraulic Engineering-ASCE,1988,114(2):134-150.
[17]WANG Zhaoyin,HUANG Jinchi,SU Dehui.Scour rateformula[J].International Journal of Sediment Research,1997,12(3):11-20.
[18]彭润泽,常德礼,白荣隆,等.推移质三角洲溯湖冲刷计算公式[J].泥沙研究,1981(1):14-29.PENG Runze,CHANG Deli,BAI Ronglong,et al.Formulasfor calculating headward erosion on a bed load delta[J].Journal of Sediment Research,1981(1):14-29.(in Chinese)