Relationships Between Tidal Prism and Throat Area of Tidal Inlets Along Yellow Sea and Bohai Sea Coasts

The relationship between P (spring tidal prism) and A (throat area below mean sea level) is statistically analysed in terms of 29 tidal inlets or bays along the Huanghai Sea (Yellow Sea) and Bohai Sea coasts. For 15 of these tidal inlets, the best regression equation is A(km2) = 0.845 />(km3)1.20. The analysis shows that C and n are little different from those in the P-A relationship for the inlets of the South China Sea and East China Sea coasts. It is noted that the relationship between P and A is unstable because of the difference in sediment abundance. The study shows that a united P-A relationship can be obtained for the tidal inlets of lagoon type and bay-drowned-valley type, not containing some half-circle shape bays which confront deep water. These half-circle bays do not belong to tidal inlets because they do not have enough sediment abundance and are fairly open.

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.

Mean water level setup/setdown in the inlet-lagoon system induced by tidal action—a case study of Xincun Inlet,Hainan Island in China

With the tides propagating from the open sea to the lagoon, the mean water level （MWL） in the inlet and lagoon becomes different from that at the open sea, and a setup/setdown is generated. The change of MWL （setup/setdown） in the system imposes a great impact on regulating the development of tidal marshes, on determining the long-term water level for harbor maintenance, on the planning for the water front development with the flood control for the possible inundation, and on the interpretation of the historical sea level change when using tidal marsh peat deposits in the lagoon as the indicator for open sea＇ s sea level. In this case study on the mechanisms which control the setup/setdown in Xincun Inlet, Hainan in China, the 2-D barotropic mode of Eulerian - Lagrangian CIRCulation （ELCIRC） model was utilized. After model calibration and verification, a series of numerical experiments were conducted to examine the effects of bottom friction and advection terms, wetting and drying of intertidal areas, bathymetry and boundary conditions on the setup/setdown in the system. The modeling results show that setup occurs over the inlet and lagoon areas with an order of one tenth of the tide range at the entrance. The larger the bottom friction is, a larger setup is generated. Without the advection term, the setup is reduced clue to a decrease of water level gradient to compensate for the disappearance of the advection term. Even without overtides, a setup can still be developed in the system. Sea level rise and dredging in the inlet and tidal channel can cause a decrease of setup in the system, whereas shoaling of the system can increase the setup. The uniqueness of the Xincun Inlet with respect to MWL change is that there is no evident setdown in the inlet, which can be attributed to the complex geometry and bathymetry associated with the inlet system.

Weather induced subtidal flows through multiple inlets of an arctic microtidal lagoon

Estuarine processes in the arctic lagoons are among the least studied but important subjects, especially considering the rapid warming of arctic water which may change the length of ice-free period in the summer. In this paper, wind-driven exchange flows in the micro-tidal Elson Lagoon of northern Alaska with multiple inlets of contrasting widths and depths are studied with in situ observations, statistical analysis, numerical experiments, a regression model on the basis of dynamics, and remote sensing data. Water velocity profiles were obtained from a bottom deployed acoustic Doppler current profiler(ADCP) in the northwestern Eluitkak Pass connecting the Beaufort Sea to the Elson Lagoon during a 4.9 day ice-free period in the summer of 2013. The subtidal flow is found correlated with wind(R^2 value ～96%). Frequently occurring east, northeast and north winds from the arctic atmospheric high-and low-pressure systems push water from the Beaufort Sea into the lagoon through the wide inlets on the eastern side of the lagoon, resulting in an outward flow against the wind at the narrow northwestern inlet. The counter-wind flow is a result of an uneven wind forcing acting through the asymmetric inlets and depth,an effect of "torque" or vorticity. Under northwest wind, the exchange flow at the northwestern inlet reverses its direction, with inward flows through the upwind northwestern inlet and outward flows through the downwind eastern inlets. A regression model is established based on the momentum equations and Taylor series expansions. The model is used to predict flows in July and August of 2015 and July of 2017, supported by available Landsat satellite images. About 73%–80% of the time the flows at Eluitkak Pass are out of Elson Lagoon for the summer of 2015 and 2017. Numerical experiments are conducted to corroborate the findings and illustrate the effects under various wind conditions. A quasi-steady state balance between wind force and surface pressure gradient is confirmed.

广湛客专湛江湾海底隧道工程极限冲刷深度预测

湛江湾是在遂溪河谷基础上经海侵发育起来的潮汐汊道型溺谷海湾,湾内水深大,深槽内水流动力强,水流挟沙力大。基于河道地质条件、泥沙组成及水动力特征,利用水工模型试验手段,预测不利水文条件下隧址河段河床的最大冲刷深度。研究成果表明,以潮为主情况下,隧址河床未产生冲刷;以洪为主情况下,工程河段主槽冲刷后深泓线平面位置无变化,深泓冲深0.00~1.06 m。预测的极限冲刷深度可为过海隧道的科学埋设提供依据。

TYPES AND DISTRIBUTION PATTERNS OF MODERN TIDAL CHANNELS ALONG THE HUANGHE RIVER DELTA COAST

There are three major types of tidal channels along the coast of the Huanghe (Yellow) River Delta: tidal inlets, tidal creeks, and tidal channels developed from abandoned river channels. The tidal inlets develop mainly in two areas with weak erosion and barrier islands. The tidal channels formed from abandoned river channels mainly developed in the area of the new delta lobes formed since 1934. Tidal creeks developed in the intertidal zone and distributed along almost all parts of the Huanghe River Delta coast, but their scales and features are different.

双导堤工程下潮汐汊道与海岸潟湖地貌稳定性

以渤海湾沿岸具有双导堤工程的单一潮汐汊道的华北最大海岸潟湖—七里海潟湖为原型建立理想模型,通过设置包括临界侵蚀应力、临界淤积应力、泥沙沉速、初始床面高程和径流量等影响潟湖地貌演变的相关参数,得到理想模型达到稳定状态后的纳潮量P和潮汐汊道断面最大流量Q_(m)。分别建立其与潮汐汊道断面面积A的相关关系式以表征潮汐汊道稳定性。比较分析发现在表征潮汐汊道稳定性方面,Q_(m)‒A关系较P‒A关系的拟合效果更佳。分别利用Q_(m)‒A关系以及泥沙净冲淤量计算得到潮汐汊道和潟湖稳定所需时长,对比结果表明潟湖明显滞后于潮汐汊道达到稳定状态,临界侵蚀应力对潮汐汊道稳定性影响更大,而临界淤积应力、泥沙沉速和初始床面高程对潟湖稳定性影响尤为显著,径流量对潟湖和潮汐汊道稳定性的影响相当。

潮汐汊道水工建筑物与动力地貌相互作用的应用研究

随着滨水岸线资源的开发利用,水上人行栈桥平台成为亲水城市的一道亮丽风景线。潮汐汊道水域的波流特征复杂,特别是城市核心区的滨水空间,因受限于工作开展空间和工期持续时间等因素的综合制约,导致其建设难度较大。以海口湾畅通工程二期项目为例,本着便于施工的落脚点,开展了方案设计;通过建立流体动力与结构受力的单向耦合模型,在综合分析工程区域动力条件和结构受力情况的基础上优化了设计方案,总结了潮汐汊道人行栈桥平台的设计要点。经研究,发现本工程所处潮汐汊道内,常浪作用下动力条件对结构影响较小,设计结构稳定;但极端天气情况下由于风浪和增水的作用,汊道内栈道平台下的区域水深较浅,泥沙悬扬后存在泥沙骤淤风险,需加强开敞段北岸和束窄段等流速较大区域台风前后的汊道底床监测。

海南陵水新村潟湖口外滩槽演变分析

海南陵水新村潟湖口外滩槽稳定性差,制约了潟湖的整治和开发利用,为了研究潟湖口外滩槽的演变规律,结合潟湖的地形地貌、海岸动力和泥沙冲淤特点,通过对比潟湖近30 a的遥感影像资料,分析了潟湖口外海岸线、浅滩及深槽的冲淤变化,研究表明潟湖口外潮汐汊道深槽主轴线不稳定,周围岸滩亦存在强烈的冲淤变化,滩槽地貌一直处于单通道和双通道的相互演变之中,一个相对完整的演变期大约需要经历10~20 a左右的时间,波流作用下自东向西的沿岸输沙以及台风等极端事件影响是造成滩槽变化的重要原因。

湛江港潮汐汊道落潮三角洲沉积动力过程

湛江港是华南海岸规模最大的中潮溺谷湾型潮汐汊道港湾，口外发育规模巨大、形态典型的落潮三角洲。依据现场调查资料分析，落潮三角洲具有马蹄形浅滩包围中央深槽的地貌结构，由中心至周边为粗砂至极细砂同心半圆带状分布的表层沉积物分布，中央深槽落潮流动力为主，周边浅滩波浪动力和涨潮流动力为主的动力场结构。本文讨论了落潮三角洲沉积动力过程，包括落潮三角洲形成发育的动力条件与泥沙供应条件、落潮三角洲地貌结构、表层沉积物分布和动力场结构之间的一致性，以及落潮三角洲沉积物运移路径。

山东月湖的沉积物分布特征及搬运趋势

1998年 11～ 12月和 1999年 8～ 9月各一个月对月湖进行的野外工作 ,共取得表层沉积物样品 131个 ,应用激光粒度仪并结合传统的筛分法对这些样品进行粒度分析 ,进行矩法计算获得粒度参数。采用Gao命名方法 ,将沉积物划分出 5种主要类型。利用Gao -Collins粒径趋势分析模型 ,计算该区沉积物粒径趋势所显示的沉积物净搬运方向 ,结果表明 ,沉积物从四周向湖中心搬运 ,同时显示湾顶的西部和北部、涨潮三角洲以及湖心等地貌单元是沉积的优势区域。

渤海湾曹妃甸潮汐汊道系统的现代沉积作用

利用渤海湾曹妃甸近岸海域22个表层样的粒度测试数据,5个柱状样的210Pb测定数据,同时结合多年海底地形断面对比,对曹妃甸海域潮汐汊道系统的现代沉积环境进行分析。结果表明,曹妃甸西部双龙河口表层沉积物从近岸到远岸有总体变细的趋势,2008年这一区域的沉积物与2006年相比有明显细化趋势。10年尺度上曹妃甸东部海域主潮流通道——老龙沟深槽的冲刷强度为21.3cm/a,冲刷强度不大,基本处于稳定状态。从百年尺度来看,曹妃甸沿岸潮滩与近岸浅滩的淤积速率大约在0.9～1.5cm/a之间。曹妃甸近岸河口区域底质沉积物的细化很大程度上是由于挖泥造成的,适当控制人类活动强度势在必行。老龙沟深槽的维持得益于研究区广阔的纳潮水域,在港口设计规划中自觉维持纳潮量关系到整个潮汐汊道系统的稳定性。

曹妃甸老龙沟潮汐通道拦门沙演变机制

渤海湾曹妃甸老龙沟海区属于泻湖型潮汐通道体系,口门附近发育有大规模拦门沙浅滩。由于沿岸泥沙供给不足,近几十年来东坑坨等沙坝外侧海区整体呈侵蚀冲刷态势,等深线向陆蚀退。老龙沟西支深槽也以侵蚀作用为主,而拦门沙地区滩槽冲淤变化则与东坑坨演变密切相关。其中东槽冲刷发展主要是东坑坨西南尾端淤长压迫老龙沟口门,引起岬角效应增大、潮流动力增强所致,而西槽的摆动现象则主要与东槽发展所产生的挤压作用有关。由于泥沙供给不足,近年来东槽发展和西槽摆动的速度都有明显减缓。

胶东半岛南部典型海湾地貌过程对滩涂养殖的响应

应用3S技术和海湾涨/落潮不对称原理,研究了最近40年来胶东半岛南部四个典型潮汐汊道海湾的动力地貌演变,分析了大面积修建养殖池对海湾地貌过程的影响。结果表明,最近30年来4个海湾的海岸地貌类型面积、空间分布格局、地貌类型转换、地貌结构和地貌冲淤状态发生了显著改变。在大面积养殖池被围建以前的1960s年代末到1980s年代初,丁字湾处于涨潮不对称状态但不对称程度增高,乳山湾、五垒岛湾和靖海湾也处于涨潮不对称状态但不对称程度在降低。最近30年来的大面积滩涂养殖池修建,使丁字湾由不断增强的涨潮不对称向落潮不对称状态逆转,使五垒岛湾、靖海湾由涨潮不对称向落潮不对称状态的转化提前,使乳山湾由涨潮不对称向落潮不对称状态的转化延缓。

海南新村港潮汐汊道波流联合作用下的动力特征及其沉积动力学意义

基于ADCIRC与STWAVE模型,对海南新村港潮汐汊道的波浪-潮流联合作用进行了数值模拟,结果表明,S、SE向的平均浪与风暴浪在汊道近岸以产生西向沿岸流为主,SSW向平均浪与风暴浪作用时,在落潮主水道西侧形成东向沿岸流与西向沿岸流的交汇带。风暴浪作用下波生流与潮流的相互作用使瞬时流场与余流场均发生相应的变化。在平均浪作用时,汊道附近流速变化很小,而在风暴浪作用时流速增大,汊道内的涨、落潮流速不对称更为显著。在落潮主水道两侧由于波流联合作用产生涡漩,使动力减弱,从而造成泥沙落淤,而西向沿岸流的存在,使落潮主水道南侧边缘沙坝持续西移,泥沙沿落潮三角洲末端与冲流坝转运,导致新村港汊道口门西侧发育了规模较大的堆积地貌。

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。

江苏沿海大规模围垦对近海潮汐潮流的影响

基于江苏近海二维潮汐潮流预报数值模型,以2008年为基准水平年(现状),对江苏沿海滩涂围垦规划(2010—2020年)的3个阶段进行了数值模拟.从该海域主要分潮潮波分布、潮汐通道流速和单宽纳潮通量变化3个方面探讨了大规模滩涂围垦工程对江苏近海潮汐潮流的影响.数值模拟结果显示:3个阶段围垦工程实施后,M2分潮无潮点位置向东北方向略有平移,沿岸潮波传播速度加快,潮波辐聚有所增强;第1和第2阶段围垦工程实施后,西洋通道涨落潮单宽纳潮通量增幅超过10%,涨落急流速增幅20%左右,其他通道涨落潮单宽纳潮通量变化5%左右,涨落急流速变化不大;第3阶段围垦工程实施后,西洋通道涨落潮单宽纳潮通量和涨落急流速增幅均超过20%,小庙洪通道落潮单宽纳潮通量减幅超过20%,流速减幅10%左右.

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 。

乐清湾近期海岸演变研究

乐清湾是一个与东海相通的半封闭型强潮海湾。通过对1934,1968和1992年的海图对比研究表明:近期乐清湾各等深线所围水域面积持续减小。后一阶段,围垦使岸线推进速度加快,滩涂面积由前一阶段的不断增加转变为不断减小。1934到1968年,西南部最大潮滩华岐潮滩岸线和零米线平均外推速率分别为4.88m/a和13.24m/a;1968到1992年平均淤进速率分别为6.17m/a和8.08m/a。实地采样分析表明:表层水样平均悬沙浓度为0.1043kg/m3,从湾顶向湾口呈不断增加的趋势。悬沙浓度虽较低,但湾内处于低能动力沉积环境,有利于细颗粒沉积物落淤,这是湾内地貌演变的要因。长江入海南移和陆架区再悬浮的细颗粒物质是乐清湾主要的泥沙来源。泥沙自然淤积和人类活动影响是近期乐清湾大部分岸线处于淤进状态的原因。漩门二期工程前后乐清湾的纳潮量减小了5.73%,落潮流相对携沙能力降低为工程前的79%。而根据实测落潮平均流速计算得围垦后落潮流的相对携沙能力减弱为原来的54%。而从1934年到漩门二期围垦工程后,纳潮量减小了22.57%。开辟盐田和围垦造陆工程等人类活动,对海岸演变的影响显著。

基于EFDC模型研究文昌清澜潮汐汊道人类活动对水交换速率的影响

文中利用水龄浓度概念,结合计算水交换时间的水质模型公式,在 EFDC（环境流体动力学模型）水动力基础上,分别计算了1965年和2006年清澜潮汐汊道的海湾水交换时间。研究结果表明,2006年的平均水交换时间为107d,1965年的平均水交换时间为114d,发生变化的主要原因是清澜港航道被浚深至7-8m,潮汐动力显著增强,纳潮量增加了4.3%所致。