淤泥质潮流深槽最大冲刷深度的一个概念模型

以概念模式方法计算了淤泥质潮流深槽的最大深度,探讨了涨落潮流速、涨落潮历时、深槽淤泥质物质粒径、深槽顶底部原始深度、水道长度等因素对潮流深槽最大深度的影响。概念模式的假设条件是:(1)深槽形态为长方体,底部纵向坡度为0;(2)沉积物粒径无垂向变化;(3)只考虑潮流作用的影响,涨、落潮流速在时间序列上呈正弦分布;(4)不考虑细颗粒物质的粘性和絮凝作用。模拟结果显示:(1)涨、落潮历时对深槽最大深度的影响很小。(2)优势潮流流速与最大深槽深度之间存在着幂函数关系。(3)深槽的底质粒径、深槽的长度均与最大冲刷深度呈正相关关系。(4)深槽顶部水深与最大深度呈负相关关系。(5)由于潮汐水道深度与潮流流速和沉积物侵蚀强度之间具有负反馈关系,因此水道冲刷存在着一个极限,即最终可以达到均衡状态。潮流深槽的均衡态特征和达到均衡态所需的时间可运用沉积动力学方法来确定;同时,若应用深槽的真实参数,进一步减少模型的假设条件,可望使该模型具有实际的应用价值。     

山东荣成月湖潮汐汊道的时间-流速不对称特征

月湖是山东半岛东端的一个小型潮汐汊道.在月湖进行了潮位、潮汐观测及地形测量,运用两种方法从潮位记录推算出口门落潮主干道垂线平均流速和断面平均流速.发现除涨潮优势型和落潮优势型外,月湖还表现出另外两种时间-流速不对称,即涨潮历时大于落潮历时且涨潮流速大于落潮流速、涨潮历时小于落潮历时且涨潮流速小于落潮流速.月湖的时间-流速不对称特征与不规则潮汐、涨(落)潮的流速跟潮位的匹配关系、汊道口门的断面形态、口门特殊的水流结构及循环过程等因素有关.时间-流速不对称类型的研究,对于理解潮汐汊道系统的沉积动力行为及进行人工整治有一定意义.     

舟山本岛南部附近海域潮汐潮流特征分析

文章基于沈家门长期潮位站、长峙岛临时潮位站的观测资料和对舟山本岛南部海域多个站位实测的潮流基础数据,采用调和分析法对潮汐潮流进行特征分析。舟山本岛南部附近海域潮汐类型属于规则半日潮,潮差变化和日不等现象明显,有一定的潮汐浅海作用。潮流类型属于以往复流为主的规则半日浅海潮流,实测潮流中涨落潮流速不等、历时不等现象显著,最大流速、平均流速均是大潮大于小潮,涨潮流历时长于落潮流历时,潮流变化主要受协振波所控制,流向在涨落潮方向波动。     

珠江河口磨刀门水道枯季盐水入侵特性分析

为探讨磨刀门水道潮流和盐度的三维分布特性,本文建立了磨刀门水道的三维潮流和盐度数值模型,采用2009年枯季磨刀门水道实测潮流和盐度资料对模型参数进行率定和验证。结果显示,枯季由于上游径流量小,磨刀门水道总体涨、落潮流速都不大,表层总体涨潮平均流速都在0.5 m/s以内,总体落潮平均流速在0.8 m/s以内;底层总体涨落潮平均流速都在0.5 m/s以内;从盐度的平面分布来看,磨刀门水道近口门河段总体呈现涨潮时水道东侧盐度高于西侧,落潮时东侧盐度小于西侧的趋势。大潮和中潮期间,落潮时盐水向上游的入侵距离反而较涨潮时更远,主要原因是,落潮时的底层盐水向上游的补偿流动以及地形阻拦形成更为强烈的紊动扩散。潮汐动力弱(小潮)时,整个水道内水流流速很小,流态平缓,紊动较弱,总体仍呈现涨潮时入侵距离大于落潮,显示枯季磨刀门水道盐水入侵的主要影响因素取决于地形和潮动力。     

建立潮汐汊道P-A关系的沉积动力学方法

在均衡状态下，潮汐汉道系统的纳潮量(P)与口门面积(A)之间存在着较稳定的关系，通常用幂函数形式来表达。计算P-A关系的传统O’Brien方法因其统计性质无法给出单一潮汐汉道的P-A关系。根据沉积动力学原理，每个潮汐汉道的P-A关系都受涨落潮历时、断面平均流速、口门形态、纳潮量、淡水径流量、沿岸毛输沙量和沉积物粒度等因素的控制，对上述因素的每一种组合，都有对应的均衡态P-A关系。作者在前人工作的基础上，尝试着建立了计算单一潮汐汊道P-A关系的沉积动力学方法，并以山东半岛月湖为算例对该方法的应用进行了讨论。结果表明，均衡态潮汐汉道的P-A关系的指数n稳定在1．15左右，而系统C的变化较大。     

辽河口岸线变化对潮不对称影响的研究

受河口地形等因素的影响,潮汐潮流会出现涨落潮不对称现象,这种不对称对河口物质输运过程具有重要的影响.本研究采用流通量偏度和水位不对称度的统计方法研究辽河口岸线变化对潮波变形的影响.结果表明,辽河口潮汐潮流不对称性表现为涨潮主导型,岸线变化导致涨潮历时延长,落潮历时减小,不对称度缩减了0.007~0.071;岸线变化导致涨潮流速减小,落潮流速增大,流通量偏度缩减了0.000~0.248,岸线变化对潮流不对称的影响程度比对潮汐影响的程度大.     

江苏盐城近岸海域水动力特征

通过2018年对江苏盐城近岸海域(射阳港至大丰港之间)布设的4个测流站位夏冬两季连续25 h海流、悬沙浓度的观测资料,对该地区的水动力特征进行了初步分析,结果表明:新洋港到四卯酉河口沿岸的潮流主轴的方向基本与等深线走向一致,呈现明显的往复流特征,射阳港附近站位(JS-YWPY01站)涨潮流以SW向为主,落潮流以NNE向为主;JSYWPY02、JS-YWPY03和JS-YWPY04 3站涨潮流均以SE向为主,落潮流均以NW向为主,JS-YWPY03站和JS-YWPY04站涨潮流流速大于落潮流流速;25 h内出现2次涨落潮,落潮历时大于涨潮历时,而涨潮流速大于落潮流速,最大流速一般发生在中潮位时刻,最小流速均发生在高潮或低潮时刻,测区一带潮汐属于正规半日潮,潮流在观测周期内呈现显著的变化特征。     

山东荣成湾月湖口门落潮干道的推移质输运

改进了Gao等 ( 1 994)方法 ,并用以计算潮汐汊道口门落潮干道的垂线平均流速。利用月湖潮汐汊道系统冬、夏季各一个月的潮位资料 ,计算落潮干道的潮流流速和推移质输运率。结果表明 ,流速的计算值和实测值呈良好的相关性 ,落潮干道内落潮流的输沙能力高于涨潮流输沙能力     

钱塘江河势变迁与径潮流相互作用研究

基于平面二维水沙床耦合地貌模型,反演了1958年1月至1964年12月连续枯水年期间钱塘江尖山河段的主槽摆动过程,揭示了河势由顺直到弯曲的主要演变规律和内在机制.结果表明,在低径流和强潮流作用下,丰水年形成的北部落潮槽逐渐淤积形成浅滩,南部涨潮槽冲刷发展形成南、北两支,两槽间江心滩发育壮大,形成弯曲河势.河床冲淤主要集中在前两年内,潮汐周期内涨潮初期冲刷、涨憩和落潮初期淤积,区域淤积泥沙主要来源于下游杭州湾,北槽前期淤积为落潮型淤积,后期为涨潮型淤积.河势变化使得区域潮差增大潮动力增强,南槽涨落潮流速显著增大.顺直河势下,江心滩南北两侧分流比差异不大,涨潮期间南侧略高、落潮期间北槽略高.弯曲河势下,南槽水深和纳潮量增加,涨、落潮分流比均显著增大至75％以上.     

曹妃甸老龙沟动力地貌体系及演化

老龙沟为典型沙坝-泻湖型潮汐汊道,潮汐汊道地貌结构完整.老龙沟口门处潮流动力最强,发育-20m的深槽.口门内涨潮流三角洲上发育完整的多级水道体系.口门外落潮三角洲止于-11 m水深处.以突起的末端坝为地形标志,落潮主水道偏于落潮三角洲东侧发育,落潮三角洲西侧发育宽缓冲流平台.落潮主水道以落潮流为优势,冲流平台上潮流动力...     

Morphodynamic modelling of open-sea tidal channels eroded into a sandy seabed, with reference to the channel systems on the China coast

In this contribution, the morphodynamics of open-sea tidal channels eroded into sandy seabed in regions of flow constriction is simulated by a one-dimensional model using the Bagnold formula for bedload transport rate, and accounting for the effect of bed slope. The results show that equilibrium conditions for such channels can be reached over a period of 10²–10³ years. Sediment eroded from the channel floor is transported in the direction of the dominant current, and deposited beyond the regions of flow constriction where the current looses competence due to spreading. In this way, the material remobilized from older strata in the channels is deposited in younger sand banks near the channel heads. Where several successive channels are incised along the current axis, they interact in their morphological evolution. The morphodynamic equilibrium of a tidal channel is reached once the combined interacting sedimentological and hydrodynamic factors, such as sediment particle diameter, tidal current velocity and flood/ebb dominance, are balanced. The model output shows that the equilibrium shape of the tidal channels appears to be related mainly to flow field characteristics and, to a lesser extent, to particle size. A positive correlation exists between the depth of the channels and their response times. The equilibrium water depths of the channels are more sensitive to current speed than to either particle size or the time–velocity asymmetry of the flow field. The response times for overall morphological equilibrium are sensitive to all of the above-mentioned parameters. In particular, sediment characteristics associated with critical current velocities have far-reaching effects on the morphodynamic behaviour of tidal channels.     

长江河口拦门沙河床淤积和泥沙再悬浮过程

利用近２０年来长江河口所观测的地形、水文、悬沙和河床沉积物资料,着重对１９８８、１９８９、１９９６和１９９７年最新观测资料进行计算分析。结果表明,长江河口航道拦门沙河段来水沙量大,潮流作用强,潮波变形明显,水流挟沙力强。该河段潮流速随时间和空间变化,又处在盐淡水交换地带,流域和海域来沙在此河率时淤时冲,悬沙与床沙交换频繁,表现在涨急、落急时可床淤积层泥沙再次起动悬浮,憩流时只河床,在一个潮周期中含     

Process-based modeling of morphodynamics of a tidal inlet system

The morphodynamic evolution of an idealized inlet system is investigated using a 2-D depthaveraged process-based model,incorporating the hydrodynamic equations,Englund-Hansen’s sediment transport formula and the mass conservation equation.The model has a fixed geometry,impermeable boundaries and uniform sediment grain size,and driven by shore-parallel tidal elevations.The results show that the model reproduces major elements of the inlet system,i.e.,flood and ebb tidal deltas,inlet channel.Equilibrium is reached after several years when the residual transport gradually decreases and eventually diminishes.At equilibrium,the flow field characteristics and morphological patterns agree with the schematized models proposed by O’Brien (1969) and Hayes (1980).The modeled minimum cross-sectional entrance area of the tidal inlet system is comparable with that calculated with the statistical P-A relationship for tidal inlets along the East China Sea coast.The morphological evolution of the inlet system is controlled by a negative feedback between hydrodynamics,sediment transport and bathymetric changes.The evolution rates decrease exponentially with time,i.e.,the system develops rapidly at an early stage while it slows down at later stages.Temporal changes in hydrodynamics occur in the system;for example,the flood velocity decreases while its duration increases,which weakens the flood domination patterns.The formation of the multi-channel system in the tidal basin can be divided into two stages;at the first stage the flood delta is formed and the water depth is reduced,and at the second stage the flood is dissected by a number of tidal channels in which the water depth increases in response to tidal scour.     

Modeling interrelationships between morphological evolution and grain-size trends in back-barrier tidal basins of the East Frisian Wadden Sea

In terms of grain size, surficial sediment distribution patterns in back-barrier tidal basins (e.g., the East Frisian Wadden Sea, Germany) often show a landward fining trend from the sea boundary to the mainland shore. In addition to the cross-shore patterns, there are lateral grain-size trends toward the watersheds of the basins and toward the watersheds of tidal flats bordered by tidal channels on either side. In the present study, interrelationships between morphological evolution and grain-size trends in the back-barrier tidal basins of the East Frisian Wadden Sea were simulated for a period of 60 years by a process-based forward modeling approach using the Delft3D system. The model outputs show that grain size displays a shoreward fining trend within the basin area, which is consistent with in situ observations; such a trend can be interpreted by the shoreward decrease in the cross-shore maximum velocity. Moreover, the model predicts lateral grain-size trends similar to those observed in the tidal basins: coarser sediment remains in the inlets and channels, while finer sediment settles at the tidal watersheds and on the tidal flats between channels. The spatial patterns of tidal flat sediment grain size within the tidal basins are thus related to the distance from the sea boundary and from the tidal channels. The modeling exercise also indicates that the development of the grain-size pattern observed in the East Frisian Wadden Sea is accomplished within a few decades, and that the time periods required to reach equilibrium are much shorter for grain size than for bed elevation. Evidently, spatial grain-size information can be used to assess sediment transport and morphological adaptation processes as, for example, attempted in sediment trend analysis procedures.     

长江口北港口门海域悬沙输运机制分析

根据2012年10月24日至11月1日在长江口北港口门海域获取的沉积动力学数据,采用输运通量分解方法分析水沙输运机制。结果表明,长江口北港口门附近海域涨、落潮期间底部悬沙浓度与近底部流速呈显著线性相关,存在显著的再悬浮作用;潮周期内的悬沙输运具不对称特征,涨潮悬沙浓度大于落潮悬沙浓度,悬浮泥沙有向陆输运的趋势。拉格朗日平流输运是影响悬沙输运的主要贡献项;潮泵效应(尤其是潮汐捕捉效应)以及河口垂向环流作用是两个次要影响因素,在影响程度上前者比后者略大。观测发现,长江口北港口门海域潮流除了具有涨落潮流速、历时等不对称现象外,还具有流速结构不对称的特征,进而导致涨、落潮底部湍流混合程度不对称与输沙不对称,这可能是造成悬沙向河口内输运形成最大浑浊带的重要因素。     

近期长江河口南汇南滩水域水沙变化特征

基于南汇南滩水域2011年12月和2012年6月洪、枯季大潮的现场水文观测资料及2003年2月枯季大潮、2004年9月洪季大潮的历史观测资料,分析潮流历时、流速、优势流和含沙量等水沙现状和变化特征,探讨近年来该水域水沙变化的主要影响因素。结果表明:(1)目前,南汇南滩水域洪季大潮落潮流占主导优势,枯季大潮涨潮流占主导优势;(2)东海大桥及其周边促淤围垦工程后,洪季大潮落潮优势增强,涨潮垂线平均含沙量减少,落潮垂线平均含沙量增多;枯季大潮落潮优势减弱,涨、落潮垂线平均含沙量均减少;(3)近岸工程建设是南汇南滩水域洪季落潮优势增强、枯季落潮优势减弱的主要影响因素;涨、落潮垂线平均含沙量的变化主要与工程建设、流域来沙量减少、近岸沙体变迁等作用有关。可为河口河槽治理提供理论依据。     

河口涨潮槽的演变及治理

根据长江口１９５８－１９８７年的地形、水文测量资料和研究成果，对河口涨潮槽的形态特征、水文泥沙特性、形成原因与演变规律作较系统的分析研究。结果表明，涨潮槽呈上口窄下口宽的喇叭形，延伸方向受口外潮波传播方向制约，潮波更多地呈现驻波性质；涨潮流起主导作用，余流方向指向上游，涨潮期含沙量大于落潮期；涨潮槽的水文泥沙特性有明显的大小潮，洪枯季和年际变化，其分布可从口外海滨－直延伸到潮流界；按成因涨潮槽可分     

桐花树红树林潮滩近底层悬沙浓度垂向剖面变化特征分析*

观测红树林潮滩在波浪和潮流作用下的近底层垂向剖面悬沙浓度变化过程, 对理解海岸带植被的消能促淤机制和滨海湿地生态修复工程有着重要作用。本文以北部湾七星岛岛尾桐花树红树林潮滩为例, 基于剖面流速仪HR、声学多普勒单点流速仪ADV、浪潮仪T-wave及剖面浊度仪ASM, 获取了研究区域2019年夏季大潮连续3天的水文数据, 同时结合桐花树典型植株实测参数, 分析了潮周期内红树林潮滩近底层垂向剖面悬沙响应波浪、潮流作用及桐花树空间结构的运动过程。结果表明: 1) 桐花树潮滩近底层悬沙浓度和悬沙通量具有涨潮明显大于落潮的潮汐不对称现象, 剖面垂向高悬沙浓度区域在涨潮初期—涨急由距底部0.1~0.37m转变为距底部0.5~0.67m, 落急—落潮末期则由上部转变为下部; 2) 潮周期内悬沙起动和再悬浮阶段发生在以波浪作用主导的涨潮初期和落潮末期, 平流和沉降发生在以潮流作用为主的涨急至落急整个阶段; 3) 涨潮阶段桐花树冠层的茂密枝叶通过减缓流速拦截多于冠层上部40%以上的悬沙, 落潮水体则挟沙自陆向海经过桐花树群落, 使得悬沙浓度下降超过71%。该不对称涨、落潮动力沉积机制有利于悬沙向岸输运, 促进潮滩扩张过程。