Taking Yancheng Nature Reserve Salt Marsh as the research object,the remote sensing images from 2005 to 2020 were interpreted by using remote sensing and geographic information system technology.In this paper,the temp...Taking Yancheng Nature Reserve Salt Marsh as the research object,the remote sensing images from 2005 to 2020 were interpreted by using remote sensing and geographic information system technology.In this paper,the temporal and spatial variation characteristics of erosion and deposition in the front edge of salt marsh wetland were analyzed.The influence of sea level rise on the annual change of salt marsh area was analyzed.The characteristics of flow and sediment movement in salt marsh and the causes of erosion and deposition in front of salt marsh were analyzed.The results showed that:(1)During 2005-2007,the sea level was relatively low,and Spartina alterniflora in salt marsh expanded to the sea.Since 2007,the front edge of salt marsh wetland has coexisted with erosion and deposition.From 2008 to 2010,the front edge of salt marsh wetland once again showed a trend of comprehensive deposition to the sea side.From 2010 to 2012,the erosion of salt marsh wetland was serious.From 2012 to 2020,the front edge of salt marsh wetland in the range of 9 km south of Xinyang estuary was eroded.(2)The correlation analysis was carried out between the area of salt marsh wetland and sea level rise.Spartina alterniflora is easily affected by sea level change,owing to it having a low ecological niche.With the rise of sea level,the area of salt marsh has been decreasing since 2013.(3)In the front sea area of salt marsh wetland,the maximum velocity of the ebb and flood can reach the threshold velocity during the spring tide.The sediment starts to move at water depth of 10 m under wave actions.Owing to wave stirs up sediment and current transports the sediment,resuspended sediment causes the erosion of marsh-edge scarps.展开更多
Many phenomena in nature and technology are associated with the filtration of suspensions and colloids in porous media. Two main types of particle deposition,namely, cake filtration at the inlet and deep bed filtratio...Many phenomena in nature and technology are associated with the filtration of suspensions and colloids in porous media. Two main types of particle deposition,namely, cake filtration at the inlet and deep bed filtration throughout the entire porous medium, are studied by different models. A unified approach for the transport and deposition of particles based on the deep bed filtration model is proposed. A variable suspension flow rate, proportional to the number of free pores at the inlet of the porous medium, is considered. To model cake filtration, this flow rate is introduced into the mass balance equation of deep bed filtration. For the cake filtration without deposit erosion,the suspension flow rate decreases to zero, and the suspension does not penetrate deep into the porous medium. In the case of the cake filtration with erosion, the suspension flow rate is nonzero, and the deposit is distributed throughout the entire porous medium. An exact solution is obtained for a constant filtration function. The method of characteristics is used to construct the asymptotics of the concentration front of suspended and retained particles for a filtration function in a general form. Explicit formulae are obtained for a linear filtration function. The properties of these solutions are studied in detail.展开更多
An ideal nature system for the study of post-depositional submarine mass changing under wave loading was selected in the intertidal platform of the subaqueous Huanghe River Delta, a delta formed during period from 196...An ideal nature system for the study of post-depositional submarine mass changing under wave loading was selected in the intertidal platform of the subaqueous Huanghe River Delta, a delta formed during period from 1964 to 1976 as the Huanghe River discharged into the Bohai Gulf by Diaokou distributary. A road embankment constructed for petroleum recovery on the inter-tidal platform in 1995 induced the essential varieties of hydrodynamic conditions on the both sides of the road. With both sides sharing similarities in （1） initial sedimentary environment, （2） energetic wave loading, （3） differential hydrodynamic conditions in later stages, （4） enough long-range action, and （5） extreme shallow water inter-tidal platforms; the study is representative and feasible as well. Two study sites were selected on each side of the road, and a series of measurements, samplings, laboratory experiments have been carried out, including morphometry, hydrodynamic conditions, sediment properties, granularity composition, and fractal dimension calculation of the topography in the two adjacent areas. It was observed that in the outer zone, where wave loading with high magnitude prevailed, the tidal flat was bumpy and exhibited a high erosion rate and high fractal dimension. Further, the fractal dimension diminished quickly, keeping with the enlarging of calculative square size. However in the inner zone, where the hydrodynamic condition was weak, the tidal fiat was fiat and exhibited a low erosion rate and low fractal dimensions; the fractal dimension diminished with the enlarging of calcu- lative square size. The fractal dimensions in the different hydrodynamic areas equalized increasingly as the calculative square size accreted to threshold, indicating that the hydrodynamic condition plays a significant role in topography construction and submarine delta erosion process. Additionally, the later differentiation of sediment properties, granularity composition, microstructure characteristics, and mineral composition induced by the different hydrodynamic conditions can also contribute to the variation of topography and sea-bed erosion in the two adjacent areas.展开更多
The estimation of underwater features of channel bed surfaces without the use of bathymetric sensors results in very high levels of uncertainty. A revised approach enabling an automatic extraction of the wet areas to ...The estimation of underwater features of channel bed surfaces without the use of bathymetric sensors results in very high levels of uncertainty. A revised approach enabling an automatic extraction of the wet areas to create more accurate and detailed Digital Terrain Models (DTMs) is here presented. LiDAR-derived elevations of dry surfaces, water depths of wetted areas derived from aerial photos and a predictive depth-colour relationship were adopted. This methodology was applied at two different reaches of a northeastern Italian gravel-bed river (Tagliamento) before and after two flood events occurred in November and December 2010. In-channel dGPS survey points were performed taking different depth levels and different colour scales of the river bed. More than 10,473 control points were acquired, 1107 in 2010 and 9366 in 2011 respectively. A regression model that calculates channel depths using the correct intensity of three colour bands (RGB) was implemented. LiDAR and water depth points were merged and interpolated into DTMs which features an average error, for the wet areas, of ±14 cm. The different number of calibration points obtained for 2010 and 2011 showed that the bathymetric error is also sensitive to the number of acquired calibration points. The morphological evolution calculated through a difference of DTMs shows a prevalence of deposition and erosion areas into the wet areas.展开更多
Very limited modeling studies were available of the wave-induced current under the complex hydrodynamic conditions in the South Yellow Sea Radial Sand Ridge area（SYSRSR）. Partly it is due to the difficulties in esti...Very limited modeling studies were available of the wave-induced current under the complex hydrodynamic conditions in the South Yellow Sea Radial Sand Ridge area（SYSRSR）. Partly it is due to the difficulties in estimating the influence of the waveinduced current in this area. In this study, a coupled 3-D storm-surge-wave model is built. In this model, the time-dependent varying Collins coefficient with the water level method（TCL） are used. The wave-flow environment in the Lanshayang Channel（LSYC） during the ＂Winnie＂ typhoon is successfully represented by this model. According to the modelling results, at a high water level（HWL）, the wave-induced current similar to the long-shore current will emerge in the shallow area of the ridges, and has two different motion trends correlated with the morphological characteristics of the ridges. The wave-induced current velocity could be as strong as 1 m/s, which is at the same magnitude as the tidal current. This result is verified by the bathymetric changes in the LSYC during the ＂Matsa＂ typhoon. Thus, the wave-induced current may be one of the driven force of the ridge erosion and channel deposition in the SYSRSR. These conclusions will help to further study the mechanism of the ridge erosion and channel deposition in the SYSRSR.展开更多
In this study,a two-dimensional hydrodynamic and sediment transport model is established to quantify the influences of sea level rise on sediment transport in the Yangtze River Estuary(YRE).After validation,the model ...In this study,a two-dimensional hydrodynamic and sediment transport model is established to quantify the influences of sea level rise on sediment transport in the Yangtze River Estuary(YRE).After validation,the model was employed to investigate the sediment transport and seabed evolution under four different scenarios of sea level rise,specifically,0,0.5,1 and 1.5 m.The results reveal that there exists a‘transition point(TP)'of SSC in each main channel of YRE.Upstream of the transition point,the suspended sediment concentration(SSC)increases along with the rise in sea level,while downstream of the transition point,SSC decreases as sea level rises.Similarly,there are also transition points for topography evolution.The maximum scouring rate upstream of the transition points exceeds 4.32% for a 1.5 m rise in sea level,while the maximum deposition rate downstream of the transition points is 2.48%.The sediment fluxes from upstream to downstream in the branches of YRE are enhanced by the rise in sea level.The direction of sediment flux in the North Branch reverses downstream as sea level rises.The sediment flux from the North Channel towards downstream increases significantly,while there is no significant change in sediment flux for South Channel.Sediment deposition in the North Passage is also accelerated by sea level rise.In addition,the sediment flux from YRE to northern Jiangsu and Hangzhou Bay is also weakened by the rise in sea level.展开更多
A set of new 2-D equations of interchange between suspended sediment and bed materials was serived by theoretical deduction based on the systematic summarization and assessment the previous studies of simulating the i...A set of new 2-D equations of interchange between suspended sediment and bed materials was serived by theoretical deduction based on the systematic summarization and assessment the previous studies of simulating the interchange between suspended sediment and bed materials in the Lower Yellow River. This model was used to simulate the erosion and deposition processes caused by the interchange between suspended sediment and bed materials in a sketch channel. The results show that these equations are well consistent with the laws of interchange between suspended sediment and bed materials. Furthermore, compared with previous models, it has important practical value not only because of strong theoretical foundation, but also for smaller amount of calculating work and convenient application in practice.展开更多
基金funded by Jiangsu Ocean University Graduate Research and Practice Innovation Program(KYCX2021-040).
文摘Taking Yancheng Nature Reserve Salt Marsh as the research object,the remote sensing images from 2005 to 2020 were interpreted by using remote sensing and geographic information system technology.In this paper,the temporal and spatial variation characteristics of erosion and deposition in the front edge of salt marsh wetland were analyzed.The influence of sea level rise on the annual change of salt marsh area was analyzed.The characteristics of flow and sediment movement in salt marsh and the causes of erosion and deposition in front of salt marsh were analyzed.The results showed that:(1)During 2005-2007,the sea level was relatively low,and Spartina alterniflora in salt marsh expanded to the sea.Since 2007,the front edge of salt marsh wetland has coexisted with erosion and deposition.From 2008 to 2010,the front edge of salt marsh wetland once again showed a trend of comprehensive deposition to the sea side.From 2010 to 2012,the erosion of salt marsh wetland was serious.From 2012 to 2020,the front edge of salt marsh wetland in the range of 9 km south of Xinyang estuary was eroded.(2)The correlation analysis was carried out between the area of salt marsh wetland and sea level rise.Spartina alterniflora is easily affected by sea level change,owing to it having a low ecological niche.With the rise of sea level,the area of salt marsh has been decreasing since 2013.(3)In the front sea area of salt marsh wetland,the maximum velocity of the ebb and flood can reach the threshold velocity during the spring tide.The sediment starts to move at water depth of 10 m under wave actions.Owing to wave stirs up sediment and current transports the sediment,resuspended sediment causes the erosion of marsh-edge scarps.
文摘Many phenomena in nature and technology are associated with the filtration of suspensions and colloids in porous media. Two main types of particle deposition,namely, cake filtration at the inlet and deep bed filtration throughout the entire porous medium, are studied by different models. A unified approach for the transport and deposition of particles based on the deep bed filtration model is proposed. A variable suspension flow rate, proportional to the number of free pores at the inlet of the porous medium, is considered. To model cake filtration, this flow rate is introduced into the mass balance equation of deep bed filtration. For the cake filtration without deposit erosion,the suspension flow rate decreases to zero, and the suspension does not penetrate deep into the porous medium. In the case of the cake filtration with erosion, the suspension flow rate is nonzero, and the deposit is distributed throughout the entire porous medium. An exact solution is obtained for a constant filtration function. The method of characteristics is used to construct the asymptotics of the concentration front of suspended and retained particles for a filtration function in a general form. Explicit formulae are obtained for a linear filtration function. The properties of these solutions are studied in detail.
基金The National Natural Science Foundations of China under contract Nos 41372287 and 41272316the Comprehensive Investigation Plan of Marine Geology Security Engineering under contract No.GZH201100203
文摘An ideal nature system for the study of post-depositional submarine mass changing under wave loading was selected in the intertidal platform of the subaqueous Huanghe River Delta, a delta formed during period from 1964 to 1976 as the Huanghe River discharged into the Bohai Gulf by Diaokou distributary. A road embankment constructed for petroleum recovery on the inter-tidal platform in 1995 induced the essential varieties of hydrodynamic conditions on the both sides of the road. With both sides sharing similarities in （1） initial sedimentary environment, （2） energetic wave loading, （3） differential hydrodynamic conditions in later stages, （4） enough long-range action, and （5） extreme shallow water inter-tidal platforms; the study is representative and feasible as well. Two study sites were selected on each side of the road, and a series of measurements, samplings, laboratory experiments have been carried out, including morphometry, hydrodynamic conditions, sediment properties, granularity composition, and fractal dimension calculation of the topography in the two adjacent areas. It was observed that in the outer zone, where wave loading with high magnitude prevailed, the tidal flat was bumpy and exhibited a high erosion rate and high fractal dimension. Further, the fractal dimension diminished quickly, keeping with the enlarging of calculative square size. However in the inner zone, where the hydrodynamic condition was weak, the tidal fiat was fiat and exhibited a low erosion rate and low fractal dimensions; the fractal dimension diminished with the enlarging of calcu- lative square size. The fractal dimensions in the different hydrodynamic areas equalized increasingly as the calculative square size accreted to threshold, indicating that the hydrodynamic condition plays a significant role in topography construction and submarine delta erosion process. Additionally, the later differentiation of sediment properties, granularity composition, microstructure characteristics, and mineral composition induced by the different hydrodynamic conditions can also contribute to the variation of topography and sea-bed erosion in the two adjacent areas.
文摘The estimation of underwater features of channel bed surfaces without the use of bathymetric sensors results in very high levels of uncertainty. A revised approach enabling an automatic extraction of the wet areas to create more accurate and detailed Digital Terrain Models (DTMs) is here presented. LiDAR-derived elevations of dry surfaces, water depths of wetted areas derived from aerial photos and a predictive depth-colour relationship were adopted. This methodology was applied at two different reaches of a northeastern Italian gravel-bed river (Tagliamento) before and after two flood events occurred in November and December 2010. In-channel dGPS survey points were performed taking different depth levels and different colour scales of the river bed. More than 10,473 control points were acquired, 1107 in 2010 and 9366 in 2011 respectively. A regression model that calculates channel depths using the correct intensity of three colour bands (RGB) was implemented. LiDAR and water depth points were merged and interpolated into DTMs which features an average error, for the wet areas, of ±14 cm. The different number of calibration points obtained for 2010 and 2011 showed that the bathymetric error is also sensitive to the number of acquired calibration points. The morphological evolution calculated through a difference of DTMs shows a prevalence of deposition and erosion areas into the wet areas.
基金Project supported by the National High Technology Research and Development Program of China(863 Program,Grant No.2012AA112509)the National Natural Science Fundation of China(Grant No.41373112)
文摘Very limited modeling studies were available of the wave-induced current under the complex hydrodynamic conditions in the South Yellow Sea Radial Sand Ridge area（SYSRSR）. Partly it is due to the difficulties in estimating the influence of the waveinduced current in this area. In this study, a coupled 3-D storm-surge-wave model is built. In this model, the time-dependent varying Collins coefficient with the water level method（TCL） are used. The wave-flow environment in the Lanshayang Channel（LSYC） during the ＂Winnie＂ typhoon is successfully represented by this model. According to the modelling results, at a high water level（HWL）, the wave-induced current similar to the long-shore current will emerge in the shallow area of the ridges, and has two different motion trends correlated with the morphological characteristics of the ridges. The wave-induced current velocity could be as strong as 1 m/s, which is at the same magnitude as the tidal current. This result is verified by the bathymetric changes in the LSYC during the ＂Matsa＂ typhoon. Thus, the wave-induced current may be one of the driven force of the ridge erosion and channel deposition in the SYSRSR. These conclusions will help to further study the mechanism of the ridge erosion and channel deposition in the SYSRSR.
基金funded by the Key Laboratory of Ocean Space Resource Management Technology,MNR(No.KF-2021-106)the National Natural Science Foundation of China(No.42006143)+1 种基金the Natural Science Foundation of Zhejiang Province(No.LY22E090011)the Open Research Fund Program of Marine Ecological Restoration and Smart Ocean Engineering Research Center of Hebei Province(No.HBMESO2312)。
文摘In this study,a two-dimensional hydrodynamic and sediment transport model is established to quantify the influences of sea level rise on sediment transport in the Yangtze River Estuary(YRE).After validation,the model was employed to investigate the sediment transport and seabed evolution under four different scenarios of sea level rise,specifically,0,0.5,1 and 1.5 m.The results reveal that there exists a‘transition point(TP)'of SSC in each main channel of YRE.Upstream of the transition point,the suspended sediment concentration(SSC)increases along with the rise in sea level,while downstream of the transition point,SSC decreases as sea level rises.Similarly,there are also transition points for topography evolution.The maximum scouring rate upstream of the transition points exceeds 4.32% for a 1.5 m rise in sea level,while the maximum deposition rate downstream of the transition points is 2.48%.The sediment fluxes from upstream to downstream in the branches of YRE are enhanced by the rise in sea level.The direction of sediment flux in the North Branch reverses downstream as sea level rises.The sediment flux from the North Channel towards downstream increases significantly,while there is no significant change in sediment flux for South Channel.Sediment deposition in the North Passage is also accelerated by sea level rise.In addition,the sediment flux from YRE to northern Jiangsu and Hangzhou Bay is also weakened by the rise in sea level.
基金the National Natural Science Foundation of Chinathe Yellow River Conservancy Commission (Grant No. 50339020).
文摘A set of new 2-D equations of interchange between suspended sediment and bed materials was serived by theoretical deduction based on the systematic summarization and assessment the previous studies of simulating the interchange between suspended sediment and bed materials in the Lower Yellow River. This model was used to simulate the erosion and deposition processes caused by the interchange between suspended sediment and bed materials in a sketch channel. The results show that these equations are well consistent with the laws of interchange between suspended sediment and bed materials. Furthermore, compared with previous models, it has important practical value not only because of strong theoretical foundation, but also for smaller amount of calculating work and convenient application in practice.
