Examining the evolution of tidal creeks in the Huanghe River delta using multi-temporal Landsat images

Coastal tidal creeks are important channels for exchanges of material and energy between sea and land,and play an important role in the ecological protection of tidal flats.Although tidal creeks have evolved differently in various regions,the evolutionary process of tidal creeks in the Huanghe(Yellow)River delta of China,one of the most active deltas worldwide,is not entirely clear.Therefore,the evolution of tidal creeks in the delta from 1981 to 2021 was investigated by quantitatively analysing the tidal creeks and developing a standard for dividing their evolution periods.Visual interpretation and supervised classification methods were applied to the Landsat images to extract the tidal creek network,and 17 groups of tidal creek systems were selected.Results indicate that Creek S 1 was the most developed creek for having 113 tidal creeks totaling 65.8 km in length,while Creek E 3 had the fastest growth rate for having average annual increase of 1.9 km.Meanwhile,the level of tidal creeks increased,the average and median lengths of tidal creeks increased,and the number of tidal creeks decreased since 1981.The evolution of the tidal creek system could be divided into four stages,namely,rising,developing,stabilizing,and degrading.Analyses of a representative tidal creek show that there was no degenerated tidal creek during the rising period,with an increase in the number of 50 and a length increase of 57.9 km between 1981 and 1989.The proportion of new tidal creeks in the developing period was more than 50%and the new tidal creeks in the stabilizing period were equal to the degraded tidal creeks.Extinct tidal creeks were greater than 50%during the degrading period.There was no fixed order of tidal creek evolution in each period,and there may be a skip in evolution.Our findings provided a reference for studying the evolution of tidal creeks.

Level study on fractal characteristics of tidal creeks and information of seashell habitats in the Gaizhou Beach based on high-resolution satellite images

The fractal characteristics of tidal creeks in the Gaizhou Beach are analyzed based on high-resolution images fusionof Landsat TM and ERS2, and then the graphic models and characteristics of converse information tree of tidalcreeks in the Gaizhou Beach are established. A calculation model is established based on the above results, and at thesame time, quantitative calculation of the evolution characteristics and the diversity between the northern and thesouthern parts of the Gaizhou Beach is carried out. By the supervised classification of these images, distribution andareas of high tidal flats, middle tidal flats and low tidal flats in the Gaizhou Beach are studied quantitatively, and imagecharactistics of seashell habitats in the Gaizhou Beach and the correlation between mudflat distribution and seashellhabitats are studied. At last, the engineering problems in the Gaizhou Beach are discussed.

Spatiotemporal differentiation and development process of tidal creek network morphological characteristics in the Yellow River Delta

Tidal creeks are the main channels of land-sea ecosystem interactions,and their high dynamics are an important factor affecting the hydrological connectivity of tidal flats.Taking the Yellow River Delta as the research area,we selected remote sensing images obtained during five periods from 1998 to 2018 as the data sources.Based on the spatial analysis function in GIS,the typical morphological characteristics of tidal creeks,such as the level,length,density,curvature,bifurcation ratio,and overmarsh path length(OPL),were extracted to characterize the degree of development of the tidal creeks in the Yellow River Delta wetlands.The spatio-temporal evolution of the tidal creeks was studied,and the development process and the characteristics of the tidal creeks during the different stages of development were investigated.The results revealed that(1)The number,density,and bifurcation ratio of tidal creeks exhibit an increasing trend,but the growth of the trend is slowing.The number of tidal creeks increased by 44.9%from the initial stage of the Yellow River diversion to the late stage of the wetland restoration,but it only increased by 26.2%from the late stage of the wetland restoration to the slow expansion of the Spartina alterniflora.(2)The curvature of the tidal creeks on the landward side is greater than that on the seaward side.(3)The development degree of tidal creek has spatial heterogenetiy,which is AreaⅢ>AreaⅡ>AreaⅠ.(4)The drainage efficiency is significantly correlated with the tidal creak density and bifurcation ratio.Based on the analysis of the various morphological parameters and the drainage efficiency,it was found that after the rapid change in the tidal creek system in the early stage,the tidal creeks entered a state of slow change,and the development state of the tidal creeks tends to be in dynamic balance.The results of this study are expected to provide scientific support for the sustainable development and utilization of coastal tidal flats.

Composition of fish communities in an intertidal salt marsh creek in the Changjiang River estuary,China

Fish communities in a （third-order） intertidal creek in Dongtan marsh in the Changjiang （Yangtze） River estuary were investigated seasonally for one year. A total of 1 996 fish specimens （10 967.8 g） comprising 26 species and 15 families were collected. Abundances of fish communities in the intertidal salt marsh creek were primarily dominated by Boleophthalmus pectinirostris （19.8%）, Collichthys lucidus （18.6%）, Periophthalmus magnuspinnatus （18.2%）, Liza haematocheilus （17.9%）, and secondarily by Mugilogobius abel （8.5%）, L. carinatus （7.2%）, Odontamblyopus lacepedii （4.3%）, and Acanthogobius ommaturus （3.9%）; another 18 species were present only occasionally. Non-MDS ordination and SIMPER analysis indicated that there were two fish communities in the intertidal salt marsh creek. In spring, the communities were dominated by B. pectinirostris, P. magnuspinnatus, C. lucidus and M. abei; in summer, autumn, and winter by L. haematocheilus, L. carinatus, A. ommaturus and O. lacepedii. Some species showed strong habitat selection; L. carinatus and P magnuspinnatus were distributed mainly in the upper and middle creek, while B. pectinirostris, M. abei and O. lacepedii inhabited the middle and lower creek. The study indicated that the salt marshes of the Changjiang River estuary are an important nursery and feeding habitat for many fishes and should be protected.

Method for UAV-based 3D topography reconstruction of tidal creeks

It is common to obtain the topography of tidal flats by the Unmanned Aerial Vehicle(UAV)photogrammetry,but this method is not applicable in tidal creeks.The residual water will lead to inaccurate depth inversion results,and the topography of tidal creeks mainly depends on manual survey.The present study took the tidal creek of Chuandong port in Jiangsu Province,China,as the research area and used UAV oblique photogrammetry to reconstruct the topography of the exposed part above the water after the ebb tide.It also proposed a Trend Prediction Fitting(TPF)method for the topography of the unexposed part below the water to obtain a complete 3D topography.The topography above the water measured by UAV has the vertical precision of 12 cm.When the TPF method is used,the cross-section should be perpendicular the central axis of the tidal creek.A polynomial function can be adapted to most shape of sections,while a Fourier function obtains better results in asymmetrical sections.Compared with the two-order function,the three-order function lends itself to more complex sections.Generally,the TPF method is more suitable for small,straight tidal creeks with clear texture and no vegetation cover.

Geomorphic and hydrodynamic responses in salt marsh-tidal creek systems,Jiangsu,China

Salt marsh-tidal creek systems as a coastal geomorphological unit represent an important natural resource. The present study on Jiangsu salt marshes, eastern China, shows that variations in tidal current velocities in salt marsh creeks are controlled by the local tidal wave characteristics and the bed slope and elevation of the salt marshes and creeks. Likewise, the tidal currents modify the geomorphology of the salt marsh-tidal creek systems by transporting sediments and causing erosion/deposition. Storm events, which appear to have cyclical changes in their intensity relating to sunspot activities, can affect the geomorphic evolution of such systems. Further, in response to accelerated sea-level rise, accretional rates on salt marshes may increase. The tidal creeks have the function of transporting water and sediment onto the salt marsh surface; further, the energy of tidal currents and waves are dissipated within the salt marsh-tidal creek system. Hence, this coastal system has a potential value

生物膜对潮滩动力地貌演变影响的数值模拟研究

河口海岸潮滩湿地是一个复杂的生态系统,其地貌的形成和演变是水动力、泥沙输移和生物过程等多种因子相互作用的结果,特别是,探究潮滩生物过程并阐明其生物-物理效应是当前海洋科学领域研究的热点和难点。本文聚焦微生物生物膜,构建了耦合生物膜与水动力、沉积物输移、地貌演变的二维生物动力地貌模型,探究了生物膜在潮滩泥沙输移和地貌演变中发挥的作用。利用文献数据验证生物动力地貌模型,模型结果与文献数据吻合较好,表明所构建的模型可以较好地模拟出生物膜的增长规律及年际变化情况。结果表明,当水动力较弱时,在有生物膜作用的潮滩上,潮沟向陆侧延伸更充分,呈现出树杈状分布,潮间带区域的潮沟两侧分布有生物膜。通过对潮沟形态进行定量分析,发现生物膜的存在促进了潮沟数量增加,并向纵深方向发展,同时限制了其宽度的增加。相较于没有生物膜影响的潮滩,潮沟的平均深度增加,总面积减小,总长度增加,平均宽度减小,总体积增加。研究结果有助于加深对生物膜在潮滩地貌塑造中的作用机制认识,为海岸带保护与生态修复工程提供科学依据。

海南文昌清澜湾红树林潮沟地下水溶解碳通量的潮汐动态

海底地下水排泄(SGD)是陆地溶解碳向海洋输送的一个重要途径。以清澜湾潮沟为研究对象,以盐度为保守参数计算淡水SGD的占比为2.5%~22.7%,平均为13.0%;SGD净流量为0.86×10^(5) m^(3)/d。基于地下水溶解碳浓度,计算出该潮沟输出的溶解无机碳(DIC)和溶解有机碳(DOC)通量分别为5.78×10^(5)和0.10×10^(5) mol/d。其中,DIC是潮沟溶解碳输送的主要形式,占总溶解碳的98.3%。低潮时,DOC的49%来源于红树林植物碎屑,51%来源于SGD;DIC的78%来源于SGD,22%来源于红树林沉积物有机质。高潮时,DOC的44%来源于被污染的海水,56%来源于红树林植物碎屑;DIC的65%来源于海水,35%来源于孔隙水交换。红树林潮沟SGD向清澜湾输送了大量的溶解碳,其对近海水体碳酸盐平衡体系的影响需要进一步研究。

黄河三角洲典型潮沟发育演变过程分析

以黄河三角洲东部、侧弯丁坝北部为研究区域,基于1997—2021年内共8期Landsat系列遥感影像,采用目视解译的方法提取潮沟网络,通过分析不同时期潮沟数量、长度、密度等特征,揭示了潮沟阶段性演变规律。结果表明:潮沟的全生命周期可划分为幼年期、青年期、成熟期和退化期4个阶段,其中幼年期潮沟数量和长度增长率最大,是青年期的3倍以上;青年期潮沟数量和长度继续增加,但增长率明显降低,潮沟网络系统逐渐趋于稳定;成熟期潮沟系统发育基本完成,潮沟长度、数量、曲率等形态特征无明显变化;退化期部分潮沟萎缩、消亡、废弃,2005—2007年Ⅰ组潮沟每年消亡10.8%。

Spatial-temporal changes of tidal flats in the Huanghe River Delta using Landsat TM/ETM+ images

Integrating remote sensing, geographic information system (GIS) and fractal theory, change characteristics of tidal flats and tidal creeks in the Huanghe (Yellow) River Delta over the period of 1986-2001 were discussed. The results show that evolutions of tidal flats throughout the Huanghe River Delta are influenced by various factors, and that progressive succession and regression of tidal flats concur in different coastal segments of the delta. Human activities have played an increasingly important role in the succession process of tidal flats. Due to land reclamation in coastal zones of the delta in the last 15 years, lots of tidal flats were occupied, the artificial coastline migrated seaward (the maximum change rate was 0.8 kmyr-1) and tidal creeks became sparser (the highest decreasing rate of length of tidal creeks was 14.9 kmyr-1). Except for two coastal segments from the Tiaohe Estuary to the 106 Station and from the south of the Huanghe River mouth to the north of the Xiaodao River Estuary, fractal dimension values of tidal creeks in the remaining coastal segments of the delta decreased. In addition, the time dimension, sediment fluxes into the sea, waves and tidal-currents have profound influences on the evolution process of tidal flats. Four types of tidal flats-river-dominated tidal flats, tide-dominated tidal flats, wave-dominated tidal flats and man-dominated tidal flats can be identified. Owing to the intensification of human activities in coastal zones of the delta, man-dominated tidal flats have become the main kind of tidal flats.

Asian Horseshoe Crab Bycatch in Intertidal Zones of the Northern Beibu Gulf:Suggestions for Conservation Management

Bycatch poses a severe challenge to global fishery management.Although studies have focused on marine megafauna bycatch,research on relevant issues regarding invertebrates is limited,particularly for the threatened horseshoe crabs.In this study,the distribution of fishing gears and the bycatch intensity of Asian horseshoe crabs in the intertidal zones of the northern Beibu Gulf that harbors the most abundant juvenile Asian horseshoe crabs populations in China were evaluated.Seven intertidal nursery habitats for Tachypleus tridentatus and Carcinoscorpius rotundicauda were surveyed from May to July in 2021.A transect that crossed the tidal creeks and tidal flats between the high tide embankment/vegetation and low tide line of a given habitat was surveyed during the ebb tides.The type,number,and GPS of fishing gears were recorded when sighted,and the number and prosomal width of each horseshoe crab species were measured.Bycatch intensities differed among habitats,ranging from 0.3 to 18.4 and 1.2 to 22.7 individuals per kilometer of transect for T.tridentatus and C.rotundicauda,respectively.Among the three identified fishing gear types,ground cages and stick net sets caused a stronger bycatch pressure on these two species.Most T.tridentatus bycatch and C.rotundicauda bycatch were large individuals in late juvenile and adult stages.Therefore,the ground cages and stick net sets along/near the tidal creeks,mangrove fringe,and low tide line should be regulated and removed to ensure the functionality of the intertidal zone as the spawning corridor and nursery habitat of Asian horseshoe crabs.

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.

A Siltation Simulation and Desiltation Measurement Study Downstream of the Suzhou Creek Sluice, China

The Suzhou Creek Sluice is currently the largest underwater plain gate in the world, with a single span of 100 m. It is located in a tidal estuary at the junction of the Huangpu River and Suzhou Creek in Shanghai, China. In this study, physical and 2D vertical mathematical models were used to investigate and distinguish the mechanism of siltation downstream of an underwater plain gate from that of other gates types. According to quantitative data obtained by site investigation and the application of the physical hydrodynamic models, it was found that the characteristics of the tidal estuary as well as the fact that the sluice span is equal to the creek width are the major reasons contributing to siltation. A possible desiltation treatment system is proposed for the underwater plain gate. The system includes selection of a suitable location that allows the determination of a reasonable top elevation of the sluice floor, reserving sufficient space under the gate to accommodate siltation, setting up a mechanical desiltation system, and flushing silt along with overflow over the top of the gate. Furthermore, on-site hydraulic silt flushing experiments and a topography survey were conducted. These results showed that the measurement system is effective, and by maintaining this scheduled operation once a month, the downstream riverbed has been maintained in a good condition.

A systematic review of morphological models of salt marshes

Salt marshes are among the most important coastal wetlands and provide critical ecological services,including climate regulation,biodiversity maintenance,and blue carbon sequestration.However,most salt marshes worldwide are shrinking,owing to the effects of natural and human factors,such as climate change and artificial reclamation.Therefore,it is essential to understand the decline in the morphological processes of salt marshes,and accordingly,the likely evolution of these marshes,in order to enable measures to be taken to mitigate this decline.To this end,this study presented an extensive systematic review of the current state of morphological models and their application to salt marshes.The emergence of process-based(PB)and data-driven(DD)models has contributed to the development of morphological models.In morphodynamic simulations in PB models,multiple physical and biological factors(e.g.,the hydrodynamics of water bodies,sediment erosion,sediment deposition,and vegetation type)have been considered.The systematic review revealed that PB models have been extended to a broader interdisciplinary field.Further,most DD models are based on remote sensing database for the prediction of morphological characteristics with latent uncertainty.Compared to DD models,PB models are more transparent but can be complex and require a lot of computational power.Therefore,to make up for the shortcomings of each model,future studies could couple PB with DD models that consider vegetation,microorganisms,and benthic animals together to simulate or predict the biogeomorphology of salt marsh systems.Nevertheless,this review found that there is a lack of unified metrics to evaluate model performance,so it is important to define clear objectives,use multiple metrics,compare multiple models,incorporate uncertainty,and involve experts in the field to provide guidance in the further study.

互花米草入侵对盐城淤泥质潮滩湿地潮沟系统影响研究

潮沟既是滨海湿地特有的地貌因子,也是输送水分与盐分的重要通道,对植被的生长与空间分布有重要的影响。为探究互花米草入侵对盐城滨海湿地潮沟系统演变的影响,本文利用遥感与地理信息系统(Geographic Information System,GIS)技术,分析了1989年至2020年江苏盐城典型淤泥质潮滩湿地互花米草沼泽时空变化过程与潮沟系统演变特征。研究结果表明:①互花米草扩张经历了入侵初期的斑块阶段、中期连续带状分布阶段及现状阶段过程,入侵影响的景观类型也从光滩转变为碱蓬沼泽;②互花米草入侵过程对潮沟系统产生的影响主要表现为潮沟平均宽度与长度减小、互花米草内潮沟的数量与分支增多;③潮沟系统的变化与互花米草的平均面积、平均周长等存在较大的相关性,表明互花米草的入侵是潮沟系统变化的重要影响因素。

黄河三角洲典型潮沟系统水文连通性对大型底栖动物群落结构的影响

潮沟系统水文连通是滨海湿地的关键生态过程,也是维护和修复滨海湿地的重要途径。了解水文连通性如何影响生物在生境之间的扩散潜力,对于恢复和维持区域和局地生物多样性至关重要。分别于2021年春季(5月)和秋季(10月)对黄河三角洲湿地三条水文连通梯度明显的潮沟进行野外调查和原位观测,探讨不同水文连通梯度下大型底栖动物群落的时空变化特征及其影响因素。结果表明:调查共采集大型底栖动物50种,隶属4门8纲39科45属,包括环节动物23种、软体动物18种、节肢动物5种和纽形动物1种;大型底栖动物群落密度、生物量和多样性指数春季高于秋季,春季以体型小、适应能力较强的软甲类、多毛类和双壳类为主,秋季以活动能力较强的甲壳类、腹足类为主;大型底栖动物群落物种数、密度及生物量和多样性随水文连通性的升高有升高趋势,最高值出现在中等水文连通区域。研究表明潮沟系统水文连通性对大型底栖动物的栖息生境和群落结构及多样性均具有明显的影响,但群落结构及多样性随水文连通梯度的变动规律在季节间存在差异。研究结果有助于进一步了解滨海湿地水文连通对生物群落的影响机制,并为湿地环境保护和修复提供一定科学依据。

辽河口潮滩潮沟形态特征与水文连通强度评价

为了解潮沟形态的空间变化特征,以辽河口潮滩为例,基于潮位校正原理精确划分潮区,采用半自动方法提取精细化线状潮沟图像,基于潮沟分级算法对潮滩潮沟进行分级,定量分析潮沟的形态特征参数,并对潮滩上潮沟网络连通度进行定性评价。结果表明:潮沟的级别与平均长度具有明显的空间异质性,随着潮沟级别增加,研究区域潮沟平均长度呈指数上升,潮沟数量呈指数下降(R 2>0.99);随着潮滩高程逐渐降低,潮沟总密度显著减小,随着潮沟级别增加,潮沟密度与频数均大幅下降;潮滩距离外海愈近,潮沟曲率愈低,高潮滩潮沟分汊率最高(Rb=3.54),潮沟最不稳定;辽河口潮沟网络连通度与潮沟总分汊率、环岛潮沟数量呈正相关,潮沟网络发育程度则主要由潮沟曲率和支潮沟的密度决定,其中,高潮滩潮沟网络水文连通度最好,潮上带潮沟网络发育程度及排水效率最高。研究表明,潮汐水动力对辽河口潮沟形态特征演变及水文连通强度影响较大,进一步加强辽河口潮沟网络的排水效率可有效缓解辽河口潮滩湿地退化进程,实现盐沼植被的生态修复。

基于能量耗散视角的红树林海岸沉积地貌学

能量耗散是海岸带沉积地貌学的重要研究方向。地貌系统中的能量耗散往往存在极值,但是关于地貌演化的能量耗散趋向是最大值还是最小值,一直存在争议。本文试图从文献梳理入手,回顾海岸带地貌过程中的能量耗散问题,并用阻抗匹配概念来解释能量耗散的极值问题:当地貌系统的机械储能效率最大而热力学耗散最小时,表现为“共振阻抗匹配”,反之则表现为“梯度阻抗匹配”。基于无量纲沉降速度Ω的海滩地貌分类体系,正是表现从“共振阻抗匹配”到“梯度阻抗匹配”的典型谱系。在此基础上,从能量耗散的视角,对红树林生态系统的沉积地貌过程进行了文献综述,总结了潮沟-潮滩-红树林界面上的阻抗匹配和能量耗散问题,讨论了界面能量耗散行为如何通过水动力学和热力学过程反馈到红树林的生长过程,指出了红树林生态系统中潮沟-潮滩三维地形结构的重要性,并建议在红树林生态修复工程中应用这种结构来更好地维持系统的稳定性。

基于无人机遥感的潮沟分异与植被及地形关系研究

潮沟作为陆海之间的重要物质、能量、信息交换通道,其发育情况将决定潮滩上植被群落生长和演替的方向,同时植被的生长也将影响潮沟的发育和地形的演变。为了研究江苏盐城滨海湿地潮滩植被类型分布和其对潮沟发育的影响,在无人机技术支持下,通过反演潮滩地形高程模型和提取植被信息,对条子泥南部潮滩进行了观测。结果表明:(1)随着互花米草群落的扩张,潮滩原有盐沼植被群落出现了斑块萎缩的现象;(2)随着潮沟向内陆延伸,其沟底逐渐被互花米草占据,互花米草呈现明显的沿潮沟分布;(3)潮沟两侧有沿岸堤出现,互花米草对潮沟及附近滩面的地形有抬升的作用。由此可以看出,潮沟的发育将加速互花米草的入侵,且其入侵可改变潮滩原有地形和植被类型组成。这有利于进一步认识潮沟在潮滩上发育时是如何影响植被种群分布状况,并展现了植被分布对于潮沟发育的反作用,为当地互花米草的治理和无人机技术在其中的运用提供一定参考意见。

粉砂淤泥质潮滩潮沟形态特征及发育演变过程研究现状

从潮沟分类、潮沟地貌形态特征及发育演变过程等方面回顾分析了潮沟系统的研究进展。认为Strahler在Horton分级方法基础上提出的潮沟分级模式相对更为合理;潮沟总长与潮盆集水面积之间存在正相关关系,潮差与潮沟密度间存在正相关关系,植被对潮沟密度的影响尚无一致结论;对于潮沟截面形态的研究主要集中于宽深比、不对称性以及沉积物和植被对其影响作用;潮沟发育演变动力机制的研究在定性层面的成果较多,定量研究成果相对较少。指出潮沟内复杂的水流结构、潮沟边壁稳定性,以及通过物理模型试验、数值模拟、遥感分析等综合性手段建立影响因素与潮沟形态特征的定量关系等是今后的研究热点。