长江源曲麻莱段河床沉积物分布特征
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摘要
基于长江源通天河曲麻莱河段河床沉积物测量和分析,通过各参数的统计及对比,探讨沉积物粒度的基本特性及时空分布规律。结果表明:取样河段沉积物以沙砾石为主,由跃移质和悬移质成分组成,无滚动沉积,粒度参数和频率分布曲线特征显示长江源曲麻莱段河床沉积物分选较差,自然分布频率曲线多为双峰,是较典型的河流动力沉积物。而阶地沉积物则为多峰,分选差,应为河流与冰川共同作用的结果;同一断面河槽附近沉积物粒径较粗,与水流动力分布一致;洲滩沉积物粒径的垂向分布呈现粗细交替的基本规律,可反映不同历史时期河道水文节律以及青藏高原气候的定性变化。沉积物粒度的垂向分布可以为河流历史形态复原和水力反演提供基本数据。
The basic features and spatio-temporal distribution of grain size of sediment in Qumalai reach of the source region of Changjiang River are examined through measurements and comparisons. Research results indicate that: sand and gravel is the dominant sediment in the sampling reach, composing saltation load and suspended load with no rolling sediment. The natural frequency distribution curves are mostly of double peaks, implying that the bed sediment in Qumalai reach is of poor sorting resulting from river hydrodynamics; while the frequency distribution curves of terrace sediment are mostly of multiple peaks, also indicating poor sorting, which may be induced by both river dynamics and glacier dynamics. Sediments in the vicinity of river trough in a same section are coarse, which is consistent with flow dynamics. In addition, the grain size of shoal sediments changes alternately between coarse and fine in vertical direction, which could reflect the hydrological rhythm of rivers in different historical periods and the qualitative change of climate.The distribution of sediments in the vertical direction can supply basic data for river process analysis and hydraulic inversion.
The basic features and spatio-temporal distribution of grain size of sediment in Qumalai reach of the source region of Changjiang River are examined through measurements and comparisons. Research results indicate that: sand and gravel is the dominant sediment in the sampling reach, composing saltation load and suspended load with no rolling sediment. The natural frequency distribution curves are mostly of double peaks, implying that the bed sediment in Qumalai reach is of poor sorting resulting from river hydrodynamics; while the frequency distribution curves of terrace sediment are mostly of multiple peaks, also indicating poor sorting, which may be induced by both river dynamics and glacier dynamics. Sediments in the vicinity of river trough in a same section are coarse, which is consistent with flow dynamics. In addition, the grain size of shoal sediments changes alternately between coarse and fine in vertical direction, which could reflect the hydrological rhythm of rivers in different historical periods and the qualitative change of climate.The distribution of sediments in the vertical direction can supply basic data for river process analysis and hydraulic inversion.
引文
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[2] 潘庆燊. 长江中下游河道演变趋势及对策[J]. 人民长江, 1997,(5):22-24.
[3] 周银军,陈立, 欧阳娟,等. 三峡蓄水后典型河段分形维数的变化分析[J]. 水科学进展, 2010, 21(3):299-306.
[4] 夏细禾,余文畴. 长江中下游分汊河道稳定性与治理方略的探讨[J]. 人民长江, 1999, 30(9):21-22.
[5] 张玉柱,黄春长,庞奖励,等. 汉江与渭河大洪水滞流沉积物性质对比分析[J]. 水土保持学报, 2012, 26(1):101-105.
[6] 赵怡文,陈中原. 长江中下游河床沉积物分布特征[J]. 地理学报, 2003, 58(2):223-230.
[7] 李九发, 陈小华, 万新宁,等. 长江河口枯季河床沉积物与河床沙波现场观测研究[J]. 地理研究, 2003,22(4):513-519.
[8] PASSEGA R,BARINETTI V. Grain-size Image of Clastic Deposits[J]. Sedimentology, 1969,13(3/4): 233-252.
[9] 赵澄林. 沉积岩石学[M].北京:石油工业出版社,2001:7-71.
[10] 李晓刚,黄春长,庞奖励,等. 汉江上游白河段万年尺度洪水水文学研究[J] . 地理科学,2012, 32(8): 971-978.
[11] 蒋庆丰,刘兴起, 沈吉. 乌伦古湖沉积物粒度特征及其古气候环境意义[J]. 沉积学报, 2006, 24(6):877-882.