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1.
曲流串沟型江心洲是现代河流水利学研究关注的重要河流要素,不同于曲流河点坝和辫状河心滩,但在油气储层沉积学研究中鲜有关注。选取现代松花江典型河段,开展基于水动力学的沉积数值模拟,恢复曲流串沟型江心洲的演化过程,建立了曲流串沟型江心洲演化模式。研究结果表明:1）洪水期曲流河发生漫滩冲刷,串沟发育扩张,截弯取直,形成分汊河道及江心洲地貌;2）分汊偏移角、相对梯度优势可用于预测短期汊道存在的稳定性;3）串沟型江心洲形成于曲流点坝残余沉积之上,发育洲头侵蚀、洲尾加积、翼部双侧积,但垂向加积主要发育在顶部,不构成沉积主体结构。通过上述研究建立了曲流江心洲沉积模式,揭示了曲流河江心洲内部结构及分汊河道水动力特征,对现代河流治理和地下河流沉积储层刻画有指导意义。 相似文献
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水库下游河道冲淤调整是一个长期复杂的过程, 对防洪、航运、生态等均会产生一定影响。为探究长江中游沙市—汉口河段演变趋势并为不利变化的防控提供参考, 分析了三峡建库后悬移质分组冲淤时空变化规律: 建库后, 沙市—监利河段各粒径组泥沙均发生冲刷, 沙市流量为10 000~25 000 m3/s时, 0.125~0.250 mm粒径组泥沙冲刷量最大; 以0.125 mm为粗细颗粒分界粒径, 监利—螺山段呈现汛期、蓄水期"粗淤"而枯水期、消落期"冲细"现象; 螺山—汉口段各粒径组泥沙均发生冲刷, 且流量越大冲刷量越大。在此基础上, 通过建立流量—分组输沙量关系并根据水流挟沙力公式, 发现建库后沙市—监利、螺山—汉口河段冲淤受泥沙、水力因素共同作用, 其中泥沙因素对沙市—监利河段影响大于螺山—汉口河段; 监利—螺山河段"淤粗冲细"主要受含沙量恢复程度的影响, 与上游河床冲刷补给及本河段粗、细颗粒泥沙交换有关, 反映了冲刷条件下河道通过水流挟沙能力级配调整加大输沙能力。 相似文献
3.
Impact assessment of Three Gorges Dam’s impoundment on river dynamics in the north branch of Yangtze River estuary,China 总被引：2，自引：0，他引：2
As one of the world’s largest hydropower projects, the Three Gorges Dam (TGD)’s 156–175 m height storing test in flood recession seasons during 2006–2011 has aroused international attention. The novel approaches of cross-wavelet transform and wavelet coherence were firstly introduced to reveal the significant coherence and time lag property in time–frequency space between river dynamics in hydrological stations along Yangtze River. Then, using the optimum lag time nodes, corresponding regression models between river dynamics in these stations were established and utilized to assess the river dynamics in stations downstream under the impact of TGD’s impoundment. Results showed that the average decrease ratio of 24.3 % in the Three-Gorge reservoir outflow was caused in TGD’s impounding periods during 2006–2011. The corresponding average decrease ratios of 25.1, 16.5 and 1.9 % in Yichang flow, Datong flow (with 6 days lag), and estuarine Santiao river stage (with 32 days lag), respectively, were caused by TGD’s impoundment during 2006–2011. In addition, the impact weights of multiple driving factors on estuarine river dynamics were discussed, and the main factor of the combined impacts of estuarine tidal fluctuation and sea level change while the secondary factor of the upper stream inflow were demonstrated. A further suggestion about the optimization design of TGD’s safety impounding scheme was proposed to prevent estuarine saline water intrusion by guaranteeing the average daily increase of Three Gorges reservoir water level lower than 1.11 m/day during TGD’s impounding period. 相似文献
4.
分汊河流的江心洲洲头是分汊河段分水分沙和泥沙冲淤的动态区域,其冲淤过程受来水来沙和地形条件变化呈现冲淤交替。通过几何概化洲头的浅滩逆坡和侧向顺坡,考虑逆坡促淤和顺坡分沙作用,建立洲头浅滩的推移质冲淤的概化模型,推导洲头由淤积转向冲刷的临界流量表达式。上游来流量增加,洲头淤积速率先增加到最大值后逐渐减少,直至达到临界流量,再转向冲刷。洲头淤积速率与上游水面纵比降和床沙粒径成正比,与浅滩逆坡、侧向水面比降与顺坡成反比。若其他条件相同,洲头浅滩形状越不对称和上游来沙量越小,越有利于冲刷。模型预测武汉河段天兴洲的临界流量范围与水文观测值较为接近,对其出现超过某个大临界流量仍出现淤积的特殊性,给出的新解释是天兴洲洲头的整治工程使得在大流量条件下洲头抵抗冲刷和阻挡作用促进泥沙淤积。 相似文献
5.
Measurements were made of tidal currents, bed sediment particle sizes, and bedform dimensions at the South Branch and the
South Channel of the Changjiang estuary, China, during the dry season in 1997 and the flood season in 1998. The near bottom
current speed and direction were measured by a mechanical current meter for 10 h in 1997. The near surface current speed and
direction were measured by a Current Meter of Endeco/YSI Inc. 174 SSM for 14 h in 1997 and 1998. Nine bed sediment samples
were taken and their particle sizes were analyzed with sieves and siphons. The bedforms were nautically detected by an echo
sounder and a side scan sonar. Results show that the ebb tides had larger near-bottom and near-surface current speeds and
longer durations than the flood tides, in which the former occurred during the flood season in 1998 and not in the dry season
in 1997. The bed sediments were composed of coarse silts and very fine sands during the dry season but of fine sands during
the flood season. Bedforms were dominated by ebb tidal currents, the height∶length ratios of dunes and lee face angles were
low, and heights and lengths were larger during the flood season in 1998. The ebb and flood tidal currents, bed sediment sizes,
and dune morphology were largely controlled by the seasonal runoff variations. A new tentative boundary might be proposed
for natural dunes in very fine sand with the availability of additional field data in the future. 相似文献
6.
长江口表层沉积物粒度时空分布特征 总被引：16，自引：3，他引：16
结合近期长江口558个表层沉积物采样资料，分析了长江口表层沉积物时空分布特性，得到了近期长江口表层沉积物中值粒径和沉积物类型分布特征。横沙以上海域表层沉积物粒径洪枯季变化较小；浑浊带海域洪季粗，枯季细；口外海域则枯季粗，洪季细。横沙以上和口外海域沉积物类型洪枯季变化较小，浑浊带海域沉积物类型变化较复杂。无论洪枯季北港表层沉积物最粗，北槽次之，南槽最小。表层沉积物大小潮变化较小，两次采样平均差别为9.7％；沉积物年际变化随大通流量和输沙量的变化而变化。近十五年来，长江口表层沉积物类型变化较大的区域主要是北支上段、南北港分流口、北槽和南槽浑浊带海域，主要与河槽的自然演变和人类活动有关。结合Pejrup新三角图对长江口各沉积动力环境进行分区，对比各沉积环境亚区的粒度特征，并对黄河口、长江口、珠江口表层沉积物粒度参数进行对比。 相似文献
7.
曲流河是冲积平原河流中的重要河型之一,曲流河的河道演变对冲积平原的建设与演化起着非常重要的作用。地处江汉平原的长江中游藕池口至城陵矶段河道是最典型的曲流河段,其曲流河道的几何形态和变化过程较为复杂,对该段河道演化过程的研究在河流的开发利用及水利工程建设中具有很好的理论指导意义。本研究通过对历史资料和多期卫星遥感影像的解译与分析,表明长江中游藕池口至城陵矶河段的曲流河道演化在受自然和人类活动双重影响的情况下,该河段河道的演化仍然维持曲流河特征。受大洪水的切滩作用及松滋口、太平口和藕池口3个分流口对洞庭湖的分水分沙的影响,该段河道的演化过程较为复杂。自然裁弯取直和人工裁弯取直在一定程度上改变着河道演化的进程,但由裁弯取直及上游水利工程引起的纵坡降增加产生的冲淤变化将会维持河道的稳定,同时在该河段实施的护岸工程也会抑制河流的横向侵蚀,曲流河段河道演化进入自调整和自组织过程。 相似文献
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为探索三峡坝下游淤沙型浅滩冲淤特性突变的成因,结合芦家河河段较为系统的水沙输移和河床冲淤观测资料,从来水来沙变化、河势调整等多种角度,分析了多因素变化条件下的浅滩演变机理。结果显示:水库下游悬沙来量大幅减少导致分汊河道冲刷变形,促使洪水流路过流能力增强、浅滩冲淤转换的临界流量减小;三峡水库进入175 m运行期后,来流退水过程加快,泥沙输移更集中于汛期。以上变化更利于汛期浅滩淤积,不利于汛后浅滩冲刷,各种因素迭加作用下,导致浅滩条件在2008年前后发生阶段性变化。未来冲刷过程中,研究河段的浅滩淤积现象仍可能出现,类似问题在长江中下游其他的主流年内交替型汊道浅滩也同样值得注意。 相似文献
11.
根据黄河下游1950年以来的水沙、河道冲淤及洪水观测资料,系统分析了黄河下游主要控制站输沙水量与来沙量、洪水量级、水沙搭配、区间引水引沙及河道允许淤积度等因子间的相互关系。在探讨泥沙输移规律和机理的基础上,引入水沙搭配参数,建立了适用于黄河下游主要控制站汛期及洪水期计算输沙水量的数学表达式,量化了水沙条件及河道允许淤积度变化对河道输沙水量的影响程度。该研究对维持黄河健康生命及黄河水资源的规划利用具有重要的理论和实际意义。 相似文献
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《China Geology》2019,2(3):325-332
Based on the 39 surface sediment samples collected in the flood season and the dry season in 2012 respectively and the measured hydrological data in October 2012, the sediment grain size characteristics has been analyzed and the response mechanism of surface sediments to estuarine hydrodynamics was revealed by calculating the range of waves and tidal currents. The results show that: (1) The grain size of the surface sediment samples decreased gradually from land to sea in the flood season. The fine sediment was redistributed under marine hydrodynamics in the dry season and the sediments showed coarser tendency ingeneral; (2) tidal current stirring sediment was very obvious in Dagu River estuary area, and wave stirring sediments mainly occurred in the tidal flat area and estuary sand bar area; (3) in the flood season, surface sediment sat the estuary were transported towards south and southeast. In the dry season, surface sediments were transported towards southwest at the north area of Jiaozhou Bay Bridge, and sediments were transported towards northeast area at the south of Jiaozhou Bay Bridge. 相似文献
14.
三峡大坝建成后长江输沙量的减少及其对长江三角洲的影响 总被引：3，自引：1，他引：3
三峡大坝建成之后,大量泥沙滞留于库区,出库泥沙量减少,坝下河床冲刷而提供相当数量的泥沙,支流湖泊供沙也发生变化,这将使进入河口地区的泥沙有所减少。三峡大坝以上长江干流和支流建设新的大坝,南水北调、封山育林、退耕还林以及减少水土流失都将进一步减少长江进入河口地区的泥沙。由此估计,三峡大坝建成后的百年内长江输入河口地区的泥沙约为2.0×108～2.5×108t/a;冰后期长江三角洲形成和发育期间的长江年均输沙量为1.84×108～2.28×108t。二者的数值相当接近,然而与近50年的观测(4.33×108t/a)相差甚远,长江流域的气候变化和人类活动可能是造成这一现象的原因。文章着重说明中国和长江上游人口的增长、种植作物的改变可能是水土流失、长江泥沙量增长的主要原因。 相似文献
15.
对输沙水量的计算方法,黄河下游汛期、非汛期输沙水量的研究现状,水库对输沙水量的影响,输沙用水总量的研究现状等方面分别作了回顾。分析指出,输沙水量与来水含沙量、来水流量、河道冲淤、河床前期条件等有关。黄河下游各时期输沙水量不同,汛期最小,其余依次为非汛期、冬三月、凌汛期。水库调水调沙的同时也改变着黄河下游的输沙水量。利用水库群调水调沙,使小浪底水库以造床流量、高含沙水流输沙,是目前推荐的黄河下游节水减淤高效输沙入海的主要方式。提出了一些有待进一步研究的问题。 相似文献
16.
三峡大坝建成后长江输沙量的减少及其对长江三角洲的影响 总被引：19，自引：6，他引：13
三峡大坝建成之后,大量泥沙滞留于库区,出库泥沙量减少,坝下河床冲刷而提供相当数量的泥沙,支流湖泊供沙也发生变化,这将使进入河口地区的泥沙有所减少。三峡大坝以上长江干流和支流建设新的大坝,南水北调、封山育林、退耕还林以及减少水土流失都将进一步减少长江进入河口地区的泥沙。由此估计,三峡大坝建成后的百年内长江输入河口地区的泥沙约为2.0×108～2.5×108t/a;冰后期长江三角洲形成和发育期间的长江年均输沙量为1.84×108～2.28×108t。二者的数值相当接近,然而与近50年的观测(4.33×108t/a)相差甚远,长江流域的气候变化和人类活动可能是造成这一现象的原因。文章着重说明中国和长江上游人口的增长、种植作物的改变可能是水土流失、长江泥沙量增长的主要原因。 相似文献
17.
潮流界变动段的边滩与浅滩演变关联性强，同时受径潮流水动力、供沙来源及人类活动等多重影响，是航道治理与疏浚维护的重点河段。通过对三益桥河段1976—2017年期间河床冲淤、汊道分流比、三益桥边滩及浅滩演变过程的分析，明确三益桥边滩及浅滩演变的驱动机制。2012年以来三益桥边滩12.5 m水深以浅滩体体积为增大态势，大水年份边滩以淤积为主，设计航槽及深槽以冲刷为主，中水年份边滩淤积厚度小于深槽。上游五峰山弯道河势稳定，具有阻隔上游和畅洲河段河势、汊道分流比调整等传递作用，三益桥边滩淤涨（长）与上游和畅洲河段河势及汊道分流比调整的关系不显著，主要与流域来流流量大小及过程、上游河道冲刷供沙等相关。洪季三益桥上浅区碍航程度大于枯季，汛前中水流量（大通水文站流量介于26 000~34 000 m3/s之间）持续天数长的年份碍航程度大于大洪水年份同时期；因此，流量过程决定边滩与浅滩的冲淤分布，中水流量持续时间长短及供沙量大小决定三益桥边滩淤积量及浅滩碍航淤积量。 相似文献
18.
潮流界变动段的边滩与浅滩演变关联性强，同时受径潮流水动力、供沙来源及人类活动等多重影响，是航道治理与疏浚维护的重点河段。通过对三益桥河段1976—2017年期间河床冲淤、汊道分流比、三益桥边滩及浅滩演变过程的分析，明确三益桥边滩及浅滩演变的驱动机制。2012年以来三益桥边滩12.5 m水深以浅滩体体积为增大态势，大水年份边滩以淤积为主，设计航槽及深槽以冲刷为主，中水年份边滩淤积厚度小于深槽。上游五峰山弯道河势稳定，具有阻隔上游和畅洲河段河势、汊道分流比调整等传递作用，三益桥边滩淤涨（长）与上游和畅洲河段河势及汊道分流比调整的关系不显著，主要与流域来流流量大小及过程、上游河道冲刷供沙等相关。洪季三益桥上浅区碍航程度大于枯季，汛前中水流量（大通水文站流量介于26 000~34 000 m3/s之间）持续天数长的年份碍航程度大于大洪水年份同时期；因此，流量过程决定边滩与浅滩的冲淤分布，中水流量持续时间长短及供沙量大小决定三益桥边滩淤积量及浅滩碍航淤积量。 相似文献
19.
Jianyu Chen Delu Pan Mingliang Liu Zhihua Mao Qiankun Zhu Ninghua Chen Xiaoyu Zhang Bangyi Tao 《Estuaries and Coasts》2017,40(4):1055-1065
The Changjiang Estuary is one of the largest estuaries in the world, where hypoxia frequently occurs during the summer season. Recent routine surveys in the observed area found that the low dissolved oxygen (DO) in the summer bottom water was not rapidly expanding with increasing nutrient loads in Changjiang diluted waters. Based on the remote sensing data and in situ data, we examined the historic seasonal hypoxia observations for the bottom waters of the Changjiang Estuary and investigated the short- and long-term effects that runoff had on variations in DO and chlorophyll-a (Chl-a). Our analysis indicated that the recent areal variation in hypoxia was due to the changing Chl-a distribution and stratification conditions. The correspondence between hypoxia and surface Chl-a concentration showed that remotely sensed Chl-a larger than 3.0 mg L?1 was an essential condition for the formation of hypoxia off the Changjiang Estuary. The trend of Chl-a concentration was significantly impacted by the Three Gorges Dam (TGD), and the inter-annual variation of Chl-a was weakly affected by global-scale climate variability. After the TGD impoundment, the sediment loading in the Changjiang runoff and suspended sediments in Changjiang Estuary in August decreased, and the high Chl-a concentration moved landward. These shifted the hypoxia from its optimal forming conditions. 相似文献
20.
三峡水库蓄水运用后,泥沙淤积主要分布在常年库区的宽谷和弯道,峡谷则无累积性淤积。基于实测资料计算了三峡成库前（2001年）和成库后（2003-2011年）的挟沙力,结果表明挟沙力随着不同运行阶段坝前水位的抬高而逐步降低,宽谷河段降低幅度较大,峡谷河段降低幅度较小,泥沙淤积比率逐步增大。宽谷河段挟沙力普遍降至含沙量以下而发生淤积,峡谷河段挟沙力仍大于含沙量而无累积性淤积。流量越大,宽谷河段的挟沙力越小于含沙量,而峡谷河段的挟沙力越大于含沙量,表明宽谷河段淤积主要发生在汛期,而峡谷河段汛期以冲刷为主。由于细颗粒泥沙絮凝沉降以及黏性淤积物难以冲刷,恢复饱和系数淤积取1、冲刷取0.01得到的沿程淤积量计算值与实测值吻合较好。弯道河段计算的淤积量与实测值差异较大,表明弯道河段二维特征明显,利用一维的挟沙力计算淤积量不能适用。 相似文献