Yellow River Mouth Research Articles

Dispersal pattern of suspended sediment in the shear frontal zone off the Huanghe (Yellow River) mouth

The in situ records of a cruise in September 1995 off the Huanghe mouth and laboratory measurements indicate that the shear front off the river mouth results from the phase difference between the nearshore and offshore tides and plays significant role in the river-laden sediment dispersal. Two types of shear front, identified from the behaviors of currents inside and outside the shear front, alternate over tidal cycle, each of which lasts for ∼2–3 h. The dispersal patterns of suspended sediment at the stations inside and outside the shear front are distinctly different from each other. In addition, the gravity-driven hyperpycnal flow generated near the mouth is terminated within shallow water due to the barrier effect of shear front. A dispersal pattern of river-laden suspended sediment in the shear frontal zone is proposed to interpret the difference of sediment transport inside and outside the shear front. The fresh and highly turbid river effluents discharge to the sea during ebb tides and are transported northwestwards inside the shear front under the combined impacts of northward ebb currents, down-slope transport of hyperpycnal flow and confining action of shear front; after partially mixing with the ambient seawater the river effluents are then transported southeastwards outside the shear front along the flood currents, causing the intermittent increase in suspended sediment concentration and corresponding decrease in salinity outside the shear front. Over annual time scale the subaqueous slope has a geomorphological response to the ephemeral shear front. Most of the river-laden sediment deposit inside the shear front with a high accumulation rate, while erosion is dominant outside the shear front due to the lack of sediment supply.

Distribution of biomass of heterotrophic bacterioplankton in the Bohai Sea

Distribution, variation and impact factors of biomass of bacterioplankton from April to May 1999 in Bohai Sea were studied in DAPI method with epifluorescence microscopy. The biomass in surface waters showed a small day-night variation, varying from 0.13 to 2.51 μg/dm3 with an average of 0.84 μg/dm3. The biomass in bottom waters showed, however, a large variation, changing from 0.15 to 4.18 μg/dm3 with an average of 1.36 μg/dm3. The peak values occurred at 5 and 11 a.m. The bottom water biomass showed a significant correlation with particulate organic carbon (r=0.639,P<0.05). Heterotrophic bacterioplankton biomass was high in nearshore waters and low in offshore areas with a high biomass zone around Huanghe (Yellow) River mouth, showing the same distribution of nutrients. In vertical distribution, heterotrophic bacteria biomass in bottom waters was higher than that in surface water.

Rapid shifts of the river plume pathway off the Huanghe (Yellow) River mouth in response to water-sediment regulation scheme in 2005

Freshwater plume represents a key passage for the river to deliver sediment to the coastal ocean. A water-sediment regulation scheme was implemented for the Huanghe River in 2005; in order to examine the effect of such an activity on the river plume dynamics, three cruises were carried out off the Huanghe River mouth. The preliminary results of the in-situ measurements suggested that the plume pathway shifted rapidly during the period of less than twenty days, which was confirmed by satellite remote sensing data in the same period. The rapid shifts were resulted from intensive interactions between river discharge and the varying bathymetry in the river mouth area. A large amount of river sediment was delivered to the coastal region during this period and mostly deposited in the mouth bar area due to jet-flow deceleration, forming a cluster of mouth bars across the river mouth, which caused the rapid shifts of the plume pathway.

On the Origin of the Radial Sand Ridges in the Southern Yellow Sea: Results from the Modeling of the Paleoradial Tidal Current Fields off the Paleo-Yangtze River Estuary and Northern Jiangsu Coast

The origin of the radial sand ridges (RSR) in the southern Yellow Sea has been a controversial problem since they were discovered. The key to solving this problem is to answer whether the radial tidal current field existed prior to the formation of the RSR. With a two-dimensional tide model over the Bohai Sea, the Yellow Sea, and most of the East China Sea, the M2 tides and tidal currents at around 7000 years BP, 6000 years BP, 3800 years BP, the 8th and 11th centuries AD are simulated. The model results show that, from 7000 years BP to 3800 years BP, tidal currents north of the major longitudinal axis of the Paleo-Yangtze River Estuary (PYRE) converged toward and diverged from the mouth of this river and the distribution pattern of the tidal current field was largely similar to that of the tidal current field over the southern Yellow Sea. Toward the 8th century AD, the PYRE became a delta. The Yangtze River mouth migrated southeastward considerably until the 11th century AD, and the shorelines of the Yangtze River mouth and northern Jiangsu were generally similar in geometry to the present ones. At these two stages (the 8th and the 11th centuries AD), the radial tidal current fields with a focal point in Dongtai area were evident, and the distribution patterns of tidal current fields were much similar than at present. After the 11th century AD, the northern Jiangsu shoreline evolved gradually to the present position under the influence of the shifting Yellow River mouth and the present radial tidal current field, with its focal point in the Qianggang area, was formed eventually over the southern Yellow Sea. In short, the radial tidal current field off the PYRE and northern Jiangsu coast has existed and its distribution pattern has been quite stable since around 7000 years BP, despite the shoreline evolution of the PYRE and northern Jiangsu coast. However, the convergent location of the tidal currents has shifted from the mouth of the PYRE to the Dongtai area and then to the present Qianggang area. This suggests that the radial tidal current field in the RSR area existed before the formation of these sand ridges, and the RSR in the southern Yellow Sea were formed and are maintained by radial tidal current fields with sufficient sediment supply.

Monitoring the anthropogenic impact on the muddy coast by means of topographic and bathymetric surveys north of the Yellow River Mouth, China

The effects of the artificial-diversion of the Yellow River Mouth for extensive petroleum exploration beginning in August 1996 on the morphology of the mud flat coast are discussed. Changes in the morphology of the coastal zone were monitored during the period from 1996 to 2000. A Golden Software system was used to calculate the differential surfaces between the surveys in order to investigate the local patterns of accretion and erosion and to determine the volume changes between consecutive surveys. Volumetric studies showed that the net accretion in the study period was about 1.7×108m3. Between July 1996 and October 1996, a time interval characterized by intense runoff, an accumulation of about 4×108m3 occurred. In the period from October 1996 to October 1998, a period of diminution in runoff and sediment supply in the upstream, an erosion of 8.9×107m3 occurred, indicating sediment starvation of the area. Between October 1998 and October 2000, due to an inadequate supply of runoff and sediment, about 1.4×108m3 of sediments was eroded and transported offshore.

Comparison of summer thermohaline field and circulation structure of the Bohai Sea between 1958 and 2000

The analysis of observed salinity data over 35 years (1961–1996) at four stations around the Bohai Sea, i.e. Huludao, Qinhuangdao, Tanggu and Beihuangcheng, reveals that the salinity of the 4 observation stations has increased 1.1, 1.6, 1.9 and 0.4, respectively. The data also show that over the past 35 years, there have been at least 5 large salinity variation processes. The salinity data from two cruises of the Bohai Sea in August 1958 and 2000, show that the salinity pattern of the Bohai Sea has changed markedly. Low salinity in the sea surface layer around the old Yellow River mouth in August 1958 had been replaced by high salinity in August 2000 and the maximum variation of salinity is over 10.0. In addition, the values and distribution of salinity were almost the same from surface to bottom there in August 2000, but there existed significantly different salinity levels between the surface layer and the deep layer in August 1958. When a comparison is made between the salinity levels of the above-mentioned two years, it is found that the salinity in August 2000 is on average 2.0 higher than that of August 1958 in the main part of the Bohai Sea. The change of temperature and salinity field in the Bohai Sea leads to the change of the circulation. The numerical simulation shows that in comparison with the circulation structure of the Bohai Sea in August 1958, the circulation in August 2000 changes markedly. The significant changes of circulation appeared in Bohai Bay, Laizhou Bay and in the middle of the Bohai Sea. The clockwise current loop outside of the Bohai Bay and counterclockwise current loop outside of the Laizhou Bay in August 1958 disappeared in August 2000, and the counterclockwise current loop of the Bohai Bay migrated obviously outward. The flow direction in the Laizhou Bay turned 180° around. Corresponding to the variation of the Bohai Sea circulation, the amount of water exchange between the Bohai Sea and the Yellow Sea has also changed. The water exchange rate through the Bohai Strait decreases, on average, 0.7 ×104 m3/s in August 2000 in contrast to that of August 1958.

Sediment budget of the Yellow River delta, China: the importance of dry bulk density and implications to understanding of sediment dispersal

This study constructs sediment budgets for the delta of the Yellow River, one of the world’s largest muddy rivers, and, based on these budgets, discusses the characteristics and related mechanisms of sediment dispersal at the river mouth. The sediment budgets are derived from quantifying deposits in the deltaic lobe formed at the Diaokouhe mouth of the river. A detailed investigation of the dry bulk density of deposits in the delta, which yields models of dry bulk density of deposits in the main depositional settings of the delta, guarantees the reliability of the sediment budgets. Results show that deposits behind the delta front of the Diaokouhe lobe over the period of 1965 to 1974 account for 73.5% of the incoming sediment. The constructed sediment budgets reveal that the proportions of the deposits accumulated behind the delta front vary considerably over time. The main factor responsible for the variations is the change in sediment discharge of the river. There is no evidence for the anticipated positive relationships between the proportion of sediment escaping from the delta and water discharge, clay content of incoming sediment, or mouth channel efficiency. The characteristics of sediment dispersal on the delta are related to the rapid extinction of sediment-charged hyperpycnal underflows, which are dominant in the plumes off the Yellow River mouth, and sediment deposition in the overbank flow on the delta plain because both of these processes trap a higher proportion of sediment at a higher sediment discharge.

Processes and mechanisms of dynamic channel adjustment to delta progradation: the case of the mouth channel of the Yellow River, China

AbstractThis paper analyses the processes and mechanisms of a three‐stage channel adjustment over a cycle of the Yellow River mouth channel extension based on data comprising hydrologic measurements and channel geometric surveys. Rapid siltation in the mouth channel takes place in the young stage when the channel is being built by deposits and in the old stage when the channel cannot further adjust itself to keep sediment transport in equilibrium. It is disclosed that the bankfull width–depth ratio, bed material size and slope decrease in the young and mature stages but do not change in the old stage. The reduction of bankfull width–depth ratio and bed material size during the young and mature stages is found to be able to offset the effect of the slope reduction on sediment transport due to continuous mouth progradation. They reach their limits in old stage, and a constant slope is kept by unceasing sediment accumulation. The grain size composition of incoming sediment and the fining mechanism are responsible for the occurrence of lower limit of bed material size. The reason for the existence of a limit of bankfull cross‐sectional shape is that the large flows can fully transport the sediment load they are carrying, and siltation in the channel in the old stage takes place mainly in the low flows. It is suggested that the bankfull discharge plays an important role in shaping the channel but that the entire channel form is the product of both the large and low flows plus the effects of interaction between them. Channel pattern change shows a process from a braided pattern in the young stage to a straight pattern in the mature and old stages, and the straight channel becomes gradually sinuous. The occurrence and transformation of the channel patterns are supported by two planform predictors, but are also facilitated by some other conditions. Copyright © 2003 John Wiley &amp; Sons, Ltd.

Growth of the yellow river delta over the past 800 years, as influenced by human activities

Based on measurements made over the past 50 years and data extracted from historical documents, a study has been made of the effect of human activities on the growth of the Yellow River delta over a time scale of 102‐103 years. During the period studied, the Yellow River emptied into the Yellow Sea and Bohai Sea, successively, and the deltas it created are known as the Abandoned and Modern Yellow River deltas. The growth of the Abandoned Yellow River delta can be divided into two stages. The first extended from AD 1194 to 1578, during which the growth was rather slow. The second extended from AD 1579 to 1855, when the growth was greatly accelerated. The curve showing the temporal variation of the growth of the Modern Yellow River mouth can be fitted by three straight lines with different slopes. Accordingly, its growth from 1855 to present can be divided into three stages, and the inflection points associated with three straight lines may be regarded as threshold points, reflecting marked changes in the nature and extent of human activities. On this basis, a three‐stage descriptive model has been proposed to describe the process of river mouth extension in response to changing human activities.

Dynamic Changes of Newly formed Wetlands in the Yellow River Mouth Based on GIS and Remote Sensing

The Yellow River delta is an important region where coastal and newly formed wetlands distribute in north China. Based on satellite remote sensing images and GIS techniques, this paper tends to delineate the dynamic changes of newly formed wetland in the Yellow River mouth from 1986.5 to 1996.10. Our results show that the newly formed wetland increased by 24.9 per year. Before 1990. 1 and it decreased by 2.40 per year after that. The northern and southwestern parts of the Yellow River mouth are main positions of decrease and the southern and the estuary parts are main positions of increase. The advancing rate of river mouth extending into the Bo Sea is decreasing obviously. The reason for that is the decreasing of water and sediments in the Yellow River, which caused by the increasing use of water and soil conservation on upper reach.

Distribution Characteristic and Assessment of Soil Organic Matter, Nitrogen and Phosphorus in Soils of New born River Mouth Wetlands

This paper investigates preliminarily spatial distribution soil organic matter (SOM), nitrogen (N) and phosphorus (P) and its environmental influence in wetland soil of different vegetation landscape in the Yellow River Mouth. The result shows the SOM and total nitrogen (TN), efficient N, efficient P in top layer soils of different vegetation district have significantly different content, The SOM is shown as Calamagrostis epigeios wetlands > Phragmites cmmunis wetlands > Tamarix chinensi wetlands above tidal > Suaeda salsa wetlands in high tidal > Tamarix chinensi wetlands in high tidal > tidal flats, the arrange of the TN and efficient N content is the same except that the content in Suaeda salsa wetlands in high tidal is heavier than Tamarix chinensi wetlands in high tidal. In different vegetation landscape wetland types the vertical change of soil nutrients are obvious except for p, gradually decrease from the upper to the lower. This case reflects the function of the vegetation on the wetland development of soil and proves the wetland soil has the characteristic of new born and bad degree of development. SOM, TN, efficient N and efficient P content in wetland soils have significantly positive correlation, but TP have no correlation with them but efficient p. The contents of TN in wetland soils range from 58~1480 mg/kg, total average content 408 mg/kg, average content of above 30 cm is 625 mg/kg. The range of TP content in the soil is 372~1042 mg/kg, total average is 569 mg/kg, average content of above 20 cm is 611 mg/kg. According the P it occurs mainly as calcium phosphates, and the validity is lower, therefore, N and P in the new born wetlands cannot produce serious impact on the environments at present.

Dynamic of China’s cultivated land and landcover changes of its typical regions based on remote sensing data

Using the multi-temporal Landsat data and survey data of national resources, the authors studied the dynamics of cultivated land and landcover changes of typical ecological regions in China. The results of investigation showed that the whole distribution of the cultivated land shifted to Northeast and Northwest China, and as a result, the ecological quality of cultivated land dropped down. The seacoast and cultivated land in the area of Yellow River Mouth expanded by an increasing rate of 0.73 km·a−1, with a depositing rate of 2.1 km·a−1. The desertification area of the dynamic of Horqin Sandy Land increased from 60.02% of the total land area in 1970s to 64.82% in 1980s but decreased to 54.90% in early 1990s. As to the change of North Tibet lakes, the water area of the Namu Lake decreased by 38.58 km2 from year 1970 to 1988, with a decreasing rate of 2.14 km2·a−1.

Analysis of corrosive environmental factors of seabed sediment

The corrosivity of seabed sediment at spots at different distances from seashore was studied based onin situ investigations in the northern sea area of the Yellow River mouth. The results show that there is close relation between distance from seashore and corrosivity of seabed sediment.

Sedimentation in the shear front off the Yellow River mouth

Based upon in-situ measurements and Landsat scanning images, spatial–temporal changes in the shear front and associated sedimentation in the subaqueous delta slope of the Yellow River have been studied. The results show that the shear front is an important dynamic factor in controlling rapid accretion at the Yellow River mouth. Suspended sediment converges and is deposited rapidly along the shear front zone; this is because a low-velocity zone is formed between two inverse flow bodies. Some small eddies occur in the shear front zone, shown on (method of concentration–temperature ratio) mapping; this is conducive to rapid convergence and accumulation of the suspended sediment in the shear front. At the same time, some hyperpycnal plumes and gravity-driven underflow may be formed; these move away from the shear front zone, due to the high sediment concentrations there. The shear front is formed firstly at the prodelta area; it then moves to the river mouth, in response to the flood or ebb tidal controls and deep sea influences. It moves along the subaqueous delta slope for 1 2 – 1 3 of the tidal cycle, during the river flood season. The shear front zone of low velocity forms a wall of water that prevents dispersal of the river outflow. The temperature image from TM6 shows that a river–sea interaction zone, a transition between the river and sea water temperatures, occurs around the mouth. The shear front is formed within this zone. A four-stage dynamic process, related to the shear front during the tidal cycle, is discussed. The results show that the shear front occurs twice during a tidal cycle.

Land Cover and Vegetation Change in the Yellow River Delta Nature Reserve Analyzed with Landsat Thematic Mapper Data

Coastal wetland is a major part of wetlands in the world. Land cover and vegetation mapping in a deltaic lowland environment is complicated by the rapid and significant changes of geomorphic forms. Remote sensing provides an important tool for coastal land cover classification and landscape analysis. The study site in this paper is the Yellow River Delta Nature Reserve (YRDNR) at the Yellow River mouth in Shangdong province, China. Yellow River Delta is one of the fastest growing deltas in the world. YRDNR was listed as a national level nature reserve in 1992. The objectives of this paper are two fold: to study the land cover status of YRDNR, and to examine the land cover change since it was declared as a nature reserve. Land cover and vegetation mapping in YRDNR was developed using multi‐spectral Landsat Thematic Mapper (TM) imagery acquired in 1995. Land cover and landscape characteristics were analyzed with the help of ancillary GIS. Land use investigation data in 1991 were used for comparison with Landsat classification map. Our results show that YRDNR has experienced significant landscape change and environmental improvement after 1992.

Dynamic characteristics of the Yellow River mouth

The Yellow River delta is dynamic because the river carries a heavy sediment load and serious siltation occurs in the area. Massive sediment transport brings fertile soil to the river mouth leading to its expansion by 20–25 km2 per year. The dramatic reduction in runoff and sediment in the delta due to increasing water demand has extended the period of flow cut-off. The river changes its delta channel about once every ten years. The channel shifts affect the upstream flood stages. Since the river shifted to the present delta channel in 1976, the shape of the delta has changed remarkably. Sediment-laden flow has been building channels by depositing sediment in low velocity areas, and has extended the river mouth into the sea for more than 40 km. The velocity of sea currents is enhanced by the growth of the river mouth spit at a rate of 1 m s−1 per 10-km extension, which results in high capacity of sea currents carrying sediment away from the mouth. The new river mouth area was silted up by 14 m and the old river mouth area was eroded by 5 m. Siltation takes place in the low flow season and scouring occurs in the flood season; scouring occurs during the rising limb of a flood and siltation occurs during the receding limb of a flood. The roughness of the river changes largely following the increase in discharge. The minimum Manning roughness occurs at non-siltation and non-erosion discharge. Tidal influence in the river is restricted to a section extending over only a few kilometres. Unlike in many other coastal areas, the river water with its high sediment concentration develops into density current and flows underneath the seawater during flood. This mechanism contributes to sediment transportation in the delta. Copyright © 2000 John Wiley & Sons, Ltd.

Satellite tracking of the migration of the red‐crowned crane Grus japonensis

Autumn migration routes of red‐crowned cranes, Grus japonensis, from two continental east Asian sites were documented in detail by satellite tracking. Two routes were identified: a 2200 km western route from Russia's Khingansky Nature Reserve to coastal Jiangsu Province, China; and a 900 km eastern route from Lake Khanka (Russia) to the Korean Peninsula and the Demilitarized Zone. The most important rest‐sites were identified as Panjin Marsh (China), coastal mudflats south‐east of Tangshan City (China), the Yellow River mouth (China), Tumen River mouth (North Korea/China/Russia), Kumya (North Korea) and Cholwon (Korean DMZ). Movements within the wintering range were also recorded, including complex commuting between sites by individual cranes and patterns of daily movements within sites. These data should prove useful for conservation of the flyway.

Sedimentation in the Yellow River delta, part II: suspended sediment dispersal and deposition on the subaqueous delta

Rapid deposition and suspended sediment dispersal off the modern Yellow River mouth has been examined from the data of topographic maps (1 : 25,000), suspension and bed sediments, current and salinity, which were measured in the field. The results show that the sedimentation rate of the mouth bar is the highest of all the environments of deposition in the modern Yellow River delta. About 30–40% of the sediment that the river transports into the sea has been deposited within the mouth bar area. Rapid deposition of the mouth bar results mainly from kinetic energy dissipation of the river under the influence of three ambient mechanisms. These three mechanisms occur simultaneously as shear front movement, which obstructs the river's jet-like flow, small-scale circulations where large velocity gradients occur and the `bulldozer' effect of the tide sensitive zone in the estuary at ebb. Based on the analysis of morphologic changes, the mouth bar can be divided into two morphologic types: one is the double-lobe and single-channel type and the other double-channel and single-lobe type. Weak hyperpycnal plumes with small density differences between the river flow and ambient water dissipate rapidly and deposit about 20% of the river sediments on the delta front slope, while hyperpycnal underflows from the river mouth can go through the steep delta front slope to form a rise apron along the upper part of the prodelta. Grain size analysis of suspended sediment shows that the flow can be divided into three layers: a tide layer in the upper part, and a hyperpycnal layer in the lower part, (these two layers are normally graded), and a transition layer with inverse grading in the mid-part. The fine suspended sediments have been transported in the hypopycnal plume layer into the prodelta and deep sea, such as the North Huanghai Sea (North Yellow Sea). This study indicates that the tidal current field has dominated the distribution of deposition of sediment on the subaqueous delta and the movements of the river effluent and hyperpycnal underflows.