Landscape characters in estuarine regions generally controlled by tidal regimes and human activities like road construction.In this work,tidal channels and road construction in the Yellow River Delta(YRD)were extracte...Landscape characters in estuarine regions generally controlled by tidal regimes and human activities like road construction.In this work,tidal channels and road construction in the Yellow River Delta(YRD)were extracted by visual interpretation methods so as to decipher impacts of tidal channel development and road construction on landscape patch change during 1989–2016.Spatial distribution history of three wetlands,which covered by Phragmites australis(freshwater marsh,FM),Suaeda salsa(salt marsh,SM),and mudflats(MD)were also established.Results indicated that tidal channel,number,frequency,and fractal dimension were all the maximum in 2003,and the minimum in 1998,respectively.Road length,number,and density showed increasing trend during 1989–2016.MD were the predominant landscape type,followed by FM and SM during 1989-2016.Principal component analysis implied two extracted factors,F1 and F2,which could represent 91.93% of the total variations.F1 mainly proxied tidal channel development,while F2 represented road construction.A multiple linear regression analysis showed positive effects of both F1 and F2 on FM patch numbers and negative impacts on SM patch areaes with R^2 values of 0.416 and 0.599,respectively.Tidal channels were negatively related to MD patch numbers,while roads were positively related to that.In any case,road construction showed larger impacts on landscape type shifting than that of tidal channel development in the YRD.展开更多
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 mainl...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.展开更多
Silt deposition occurs in the downstream approach channel of the tidal lock as in a closed channel or excavated dock basin. It is often difficult to calculate or predict siltation because of complex flow and sediment ...Silt deposition occurs in the downstream approach channel of the tidal lock as in a closed channel or excavated dock basin. It is often difficult to calculate or predict siltation because of complex flow and sediment conditions and many other affecting factors. In this paper, the characteristics of flow movement in the approach channel (including its mouth) of the tidal lock are analyzed, the basic laws of sediment movement and siltation mechanism are investigated, the conditions for three types of siltation (circumfluence siltation, density flow siltation and slow flow siltation) are discussed, and corresponding calculating formulas are proposed. A practical example shows that the difference between measured and calculated results is small, indicating that the present calculating methods could be used in design and management of practical engineering projects.展开更多
Tidal flats and saltmarshes have been a long-standing research focus because of their high socio-economic and ecological values.The evolution of tidal flat-marsh systems is highly complex due to the intertwined proces...Tidal flats and saltmarshes have been a long-standing research focus because of their high socio-economic and ecological values.The evolution of tidal flat-marsh systems is highly complex due to the intertwined processes operating over a variety of spatial and temporal scales.As a traditional research highlight,the role of regular hydrodynamic processes such as tides,waves,and river flows have been explored comprehensively with fruitful outcomes.Over past decades,the changing environment(e.g.,sea level rise,increasing anthropogenic activities,and extreme weather conditions)has attracted more attention with many reported insightful results.More recent advances indicate that biological activities play a critical role in tidal flat-marsh morphodynamics but are still poorly understood.The field of research that connects the bio-logical and physical processes is commonly described as"biogeomorphology"and requires the joint efforts by scientists from multiple dis-ciplines ranging from hydraulics,ecology,and geography to sociology.This review aims to provide a synthesis of the current research status of tidal flat-marsh morphodynamics,with a particular emphasis on the understanding of various processes and feedbacks underlying the devel-opment of morphodynamic models.Some future research needs and challenges are identified to facilitate a more sustainable management strategy for tidal flats and saltmarshes under climate change.展开更多
Field surveys covering a spring-neap tidal period were conducted to investigate the characteristics of tidal dynamics within a curved channel in the southern Hangzhou Bay, China. The channel has a maximum depth of mor...Field surveys covering a spring-neap tidal period were conducted to investigate the characteristics of tidal dynamics within a curved channel in the southern Hangzhou Bay, China. The channel has a maximum depth of more than 100 m with an average tidal range of 2.5 m, serving as the main tidal passage in the southern part of the Hangzhou Bay. Water salinity, temperature and velocity data were collected from the ship-based transects and mooring measurements. During flood tide, the tidal current intrudes into the Hangzhou Bay through the northern side of the channel with a maximum velocity of about 2 m/s, while retreats through the southern side during ebb tide with a maximum velocity of 1.8 m/s. Due to the pressure, density gradients, the Coriolis force and centrifugal effect, a lateral exchange flow is generated as the tidal current relaxes from flood to ebb. Salinity and temperature data show that the water in the channel is weakly stratified during both spring and neap tides in summer time.However, mixing in the middle region will be enhanced by the lateral circulation. Mooring data indicate that the temperature and salinity are varying at a frequency similar to tidal current but higher than sea level oscillation.Our results support the hypothesis that the high frequency salinity and temperature variations could be generated by combination of the tidal current and the lateral exchanging flow.展开更多
Serious sediment deposition often occurs after the construction of tidal sluices in small or medium-sized tidal muddy estuaries, so desilting or dredging is needed to meet the demands of flood discharge, saltwater ret...Serious sediment deposition often occurs after the construction of tidal sluices in small or medium-sized tidal muddy estuaries, so desilting or dredging is needed to meet the demands of flood discharge, saltwater retaining, and navigation in those areas. In this paper, the problem of sediment deposition induced by construction of tidal sluices is analyzed. Different problems of silting near tidal sluices for different types of estuaries are summed up, at the same time, corresponding methods are given to solve these problems, and a few successful examples are also given. The idea of comprehensive regulation and utilization of estuaries is put forward, and some proposals for solution of sediment deposition in this kind of estuaries are made.展开更多
潮滩是全球固碳能力最高的生态系统之一,是缓解全球变暖的有效蓝色碳汇。针对潮滩碳汇功能,现有研究多关注生物作用下的碳输入过程,关于地貌演变,特别是潮沟曲流摆动引起的沉积物碳输出过程研究较少,因此无法准确评估潮滩碳汇功能的动...潮滩是全球固碳能力最高的生态系统之一,是缓解全球变暖的有效蓝色碳汇。针对潮滩碳汇功能,现有研究多关注生物作用下的碳输入过程,关于地貌演变,特别是潮沟曲流摆动引起的沉积物碳输出过程研究较少,因此无法准确评估潮滩碳汇功能的动态变化。研究结合野外观测、遥感反演与室内实验,探究了潮沟曲流摆动对潮滩沉积物碳输出过程的影响,从曲流摆动速率与有机碳空间分布特征两方面开展分析。研究结果表明:潮沟曲流摆动速率的空间差异可达数个量级,由粉砂滩的10^(-3) m/s锐减至互花米草盐沼滩的10^(-6) m/s;粉砂淤泥滩潮沟摆动速率存在显著的季节性差异,冬季摆动速率约为夏季的两倍;潮滩土壤有机碳含量呈海向递减趋势:互花米草盐沼滩(4.62 g/kg)>粉砂淤泥滩(2.61 g/kg)>粉砂滩(1.51 g/kg);综合考虑曲流摆动速率与土壤有机碳含量,发现粉砂滩沉积物碳输出速率显著高于互花米草盐沼滩,可达49.4 g C m^(-2) a^(-1),与该区域的碳埋藏速率相当。研究证实了潮沟曲流摆动对潮滩沉积物碳输出过程的重要性,为提升潮滩碳汇功能预测水平提供了重要的理论依据与数据支撑。展开更多
基金Under the auspices of National Key Research and Development Project(No.2017YFC0505901)
文摘Landscape characters in estuarine regions generally controlled by tidal regimes and human activities like road construction.In this work,tidal channels and road construction in the Yellow River Delta(YRD)were extracted by visual interpretation methods so as to decipher impacts of tidal channel development and road construction on landscape patch change during 1989–2016.Spatial distribution history of three wetlands,which covered by Phragmites australis(freshwater marsh,FM),Suaeda salsa(salt marsh,SM),and mudflats(MD)were also established.Results indicated that tidal channel,number,frequency,and fractal dimension were all the maximum in 2003,and the minimum in 1998,respectively.Road length,number,and density showed increasing trend during 1989–2016.MD were the predominant landscape type,followed by FM and SM during 1989-2016.Principal component analysis implied two extracted factors,F1 and F2,which could represent 91.93% of the total variations.F1 mainly proxied tidal channel development,while F2 represented road construction.A multiple linear regression analysis showed positive effects of both F1 and F2 on FM patch numbers and negative impacts on SM patch areaes with R^2 values of 0.416 and 0.599,respectively.Tidal channels were negatively related to MD patch numbers,while roads were positively related to that.In any case,road construction showed larger impacts on landscape type shifting than that of tidal channel development in the YRD.
文摘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.
文摘Silt deposition occurs in the downstream approach channel of the tidal lock as in a closed channel or excavated dock basin. It is often difficult to calculate or predict siltation because of complex flow and sediment conditions and many other affecting factors. In this paper, the characteristics of flow movement in the approach channel (including its mouth) of the tidal lock are analyzed, the basic laws of sediment movement and siltation mechanism are investigated, the conditions for three types of siltation (circumfluence siltation, density flow siltation and slow flow siltation) are discussed, and corresponding calculating formulas are proposed. A practical example shows that the difference between measured and calculated results is small, indicating that the present calculating methods could be used in design and management of practical engineering projects.
基金supported by the National Natural Science Foundation of China(Grants No.41976156 and 51925905)the Natural Science Foundation of Jiangsu Province(Grant No.BK20200077)+2 种基金the Nantong Science and Technology Bureau(Grant No.MS 12021083)the Marine Science and Technology Innovation Project of Jiangsu Province(Grant No.JSZRHYKJ202105)the Fundamental Research Funds for the Central Universities(Grant No.B210204022).
文摘Tidal flats and saltmarshes have been a long-standing research focus because of their high socio-economic and ecological values.The evolution of tidal flat-marsh systems is highly complex due to the intertwined processes operating over a variety of spatial and temporal scales.As a traditional research highlight,the role of regular hydrodynamic processes such as tides,waves,and river flows have been explored comprehensively with fruitful outcomes.Over past decades,the changing environment(e.g.,sea level rise,increasing anthropogenic activities,and extreme weather conditions)has attracted more attention with many reported insightful results.More recent advances indicate that biological activities play a critical role in tidal flat-marsh morphodynamics but are still poorly understood.The field of research that connects the bio-logical and physical processes is commonly described as"biogeomorphology"and requires the joint efforts by scientists from multiple dis-ciplines ranging from hydraulics,ecology,and geography to sociology.This review aims to provide a synthesis of the current research status of tidal flat-marsh morphodynamics,with a particular emphasis on the understanding of various processes and feedbacks underlying the devel-opment of morphodynamic models.Some future research needs and challenges are identified to facilitate a more sustainable management strategy for tidal flats and saltmarshes under climate change.
基金The National Natural Science Foundation of China under contract Nos 41376095 and 41206006the Zhejiang Provincial Natural Science Foundation under contract Nos LQ14D060005,Y5090084 and LR/6E090001the Zhejiang University Ocean Sciences Seed Grant under contract No.2012HY012B
文摘Field surveys covering a spring-neap tidal period were conducted to investigate the characteristics of tidal dynamics within a curved channel in the southern Hangzhou Bay, China. The channel has a maximum depth of more than 100 m with an average tidal range of 2.5 m, serving as the main tidal passage in the southern part of the Hangzhou Bay. Water salinity, temperature and velocity data were collected from the ship-based transects and mooring measurements. During flood tide, the tidal current intrudes into the Hangzhou Bay through the northern side of the channel with a maximum velocity of about 2 m/s, while retreats through the southern side during ebb tide with a maximum velocity of 1.8 m/s. Due to the pressure, density gradients, the Coriolis force and centrifugal effect, a lateral exchange flow is generated as the tidal current relaxes from flood to ebb. Salinity and temperature data show that the water in the channel is weakly stratified during both spring and neap tides in summer time.However, mixing in the middle region will be enhanced by the lateral circulation. Mooring data indicate that the temperature and salinity are varying at a frequency similar to tidal current but higher than sea level oscillation.Our results support the hypothesis that the high frequency salinity and temperature variations could be generated by combination of the tidal current and the lateral exchanging flow.
文摘Serious sediment deposition often occurs after the construction of tidal sluices in small or medium-sized tidal muddy estuaries, so desilting or dredging is needed to meet the demands of flood discharge, saltwater retaining, and navigation in those areas. In this paper, the problem of sediment deposition induced by construction of tidal sluices is analyzed. Different problems of silting near tidal sluices for different types of estuaries are summed up, at the same time, corresponding methods are given to solve these problems, and a few successful examples are also given. The idea of comprehensive regulation and utilization of estuaries is put forward, and some proposals for solution of sediment deposition in this kind of estuaries are made.
文摘潮滩是全球固碳能力最高的生态系统之一,是缓解全球变暖的有效蓝色碳汇。针对潮滩碳汇功能,现有研究多关注生物作用下的碳输入过程,关于地貌演变,特别是潮沟曲流摆动引起的沉积物碳输出过程研究较少,因此无法准确评估潮滩碳汇功能的动态变化。研究结合野外观测、遥感反演与室内实验,探究了潮沟曲流摆动对潮滩沉积物碳输出过程的影响,从曲流摆动速率与有机碳空间分布特征两方面开展分析。研究结果表明:潮沟曲流摆动速率的空间差异可达数个量级,由粉砂滩的10^(-3) m/s锐减至互花米草盐沼滩的10^(-6) m/s;粉砂淤泥滩潮沟摆动速率存在显著的季节性差异,冬季摆动速率约为夏季的两倍;潮滩土壤有机碳含量呈海向递减趋势:互花米草盐沼滩(4.62 g/kg)>粉砂淤泥滩(2.61 g/kg)>粉砂滩(1.51 g/kg);综合考虑曲流摆动速率与土壤有机碳含量,发现粉砂滩沉积物碳输出速率显著高于互花米草盐沼滩,可达49.4 g C m^(-2) a^(-1),与该区域的碳埋藏速率相当。研究证实了潮沟曲流摆动对潮滩沉积物碳输出过程的重要性,为提升潮滩碳汇功能预测水平提供了重要的理论依据与数据支撑。