scholarly journals Understanding Morphodynamic Changes of a Tidal River Confluence through Field Measurements and Numerical Modeling

Water ◽  
2018 ◽  
Vol 10 (10) ◽  
pp. 1424 ◽  
Author(s):  
Qiancheng Xie ◽  
James Yang ◽  
Staffan Lundström ◽  
Wenhong Dai
Keyword(s):  
Dominant Role ◽  
Tidal Flow ◽  
River Mouth ◽  
Field Measurements ◽  
Sediment Concentration ◽  
Suspended Load ◽  
Tidal River ◽  
Wet Season ◽  
Run Off ◽  
Tidal Flows

A confluence is a natural component in river and channel networks. This study deals, through field and numerical studies, with alluvial behaviors of a confluence affected by both river run-off and strong tides. Field measurements were conducted along the rivers including the confluence. Field data show that the changes in flow velocity and sediment concentration are not always in phase with each other. The concentration shows a general trend of decrease from the river mouth to the confluence. For a given location, the tides affect both the sediment concentration and transport. A two-dimensional hydrodynamic model of suspended load was set up to illustrate the combined effects of run-off and tidal flows. Modeled cases included the flood and ebb tides in a wet season. Typical features examined included tidal flow fields, bed shear stress, and scour evolution in the confluence. The confluence migration pattern of scour is dependent on the interaction between the river currents and tidal flows. The flood tides are attributable to the suspended load deposition in the confluence, while the ebb tides in combination with run-offs lead to erosion. The flood tides play a dominant role in the morphodynamic changes of the confluence.

scholarly journals Field Studies and 3D Modelling of Morphodynamics in a Meandering River Reach Dominated by Tides and Suspended Load

Fluids ◽  
2019 ◽  
Vol 4 (1) ◽  
pp. 15 ◽  
Author(s):  
Qiancheng Xie ◽  
James Yang ◽  
T. Lundström
Keyword(s):  
Fresh Water ◽  
Water Flow ◽  
Flow Direction ◽  
Tidal Flow ◽  
Field Measurements ◽  
Sediment Concentration ◽  
Suspended Load ◽  
Suspended Sediment Transport ◽  
Main Stream ◽  
Cross Sectional

Meandering is a common feature in natural alluvial streams. This study deals with alluvial behaviors of a meander reach subjected to both fresh-water flow and strong tides from the coast. Field measurements are carried out to obtain flow and sediment data. Approximately 95% of the sediment in the river is suspended load of silt and clay. The results indicate that, due to the tidal currents, the flow velocity and sediment concentration are always out of phase with each other. The cross-sectional asymmetry and bi-directional flow result in higher sediment concentration along inner banks than along outer banks of the main stream. For a given location, the near-bed concentration is 2−5 times the surface value. Based on Froude number, a sediment carrying capacity formula is derived for the flood and ebb tides. The tidal flow stirs the sediment and modifies its concentration and transport. A 3D hydrodynamic model of flow and suspended sediment transport is established to compute the flow patterns and morphology changes. Cross-sectional currents, bed shear stress and erosion-deposition patterns are discussed. The flow in cross-section exhibits significant stratification and even an opposite flow direction during the tidal rise and fall; the vertical velocity profile deviates from the logarithmic distribution. During the flow reversal between flood and ebb tides, sediment deposits, which is affected by slack-water durations. The bed deformation is dependent on the meander asymmetry and the interaction between the fresh water flow and tides. The flood tides are attributable to the deposition, while the ebb tides, together with run-offs, lead to slight erosion. The flood tides play a key role in the morphodynamic changes of the meander reach.

Physical and bacterial processes affecting suspended particulate matter in a tidal river

1998 ◽  
Vol 38 (6) ◽  
pp. 327-335
Author(s):  
Yasunori Kozuki ◽  
Yoshihiko Hosoi ◽  
Hitoshi Murakami ◽  
Katuhiro Kawamoto
Keyword(s):  
Particle Size ◽  
Particulate Matter ◽  
Suspended Particulate Matter ◽  
River Mouth ◽  
Tidal River ◽  
Natural Soil ◽  
Size Change ◽  
Run Off ◽  
Suspended Particulate ◽  
And Behavior

In order to clarify the origin and behavior of suspended particulate matter (SPM) in a tidal river, variation of SPM in a tidal river was investigated with regard to its size and constituents. SPM was separated into three groups according to size. Change of contents of titanium and organic substances of each group of SPM was examined. SPM which was discharged by run-off was transported with decomposition and sedimentation in a tidal river. Concentration of SPM with a particle size greater than 0.45 μm increased due to resuspension in a tidal river. Origin of SPM with a size of less than 0.45 μm at upstream areas was from natural soil and most of such SPM which had been transported settled near a river mouth. It was determined from examination of the CN ratio and the ratio of the number of attached bacteria to free bacteria that SPM with a size greater than 1.0 μm at upstream areas was decomposing intensively. At the downstream areas, SPM with a size of less than 0.45 μm came from the sea. SPM with particle size greater than 1.0 μm consisted of plankton and substances which were decomposed sufficiently while flowing.

scholarly journals MODEL SEDERHANA 2-DIMENSI ARAH PERGERAKAN SEDIMEN DI SUNGAI PORONG JAWA TIMUR

2016 ◽  
Vol 9 (3) ◽  
pp. 175
Author(s):  
Huda Bachtiar ◽  
Franto Novico ◽  
Fitri Riandini
Keyword(s):  
Numerical Model ◽  
Water Level ◽  
River Mouth ◽  
Sediment Concentration ◽  
Dry Season ◽  
Observation Data ◽  
Wet Season ◽  
Level Data ◽  
Water Level Data ◽  
Mike 21

Model numerik MIKE 21 modul transport sedimen digunakan untuk mengetahui respon pergerakan lumpur Sidoarjo pada saat musim hujan dan musim kemarau dan pengaruh tanggul yang berada di muara Sungai Porong. Data yang digunakan adalah pasang surut muka air laut, kedalaman air, debit sungai, arus dan konsentrasi sedimen. Simulasi dilakukan dengan membuat dua skenario, yaitu pada saat kondisi musim hujan dan pada saat musim kemarau. Hasil simulasi model hidrodinamika di verifikasi dengan data lapangan untuk mendapatkan nilai korelasi. Verifikasi meliputi data muka air dan kecepatan arus baik arah –x maupun –y. Berdasarkan hasil verifikasi didapatkan nilai korelasi muka air sebesar 0.8641 sementara arus bernilai 0.1493 untuk sumbu –x dan 0.1917 untuk sumbu –y. Selanjutnya hasil simulasi model menunjukkan konsentrasi sedimen pada tanggal 27 November 2007 merupakan puncak tertinggi dengan nilai 3.2x10-3 kg/m3 untuk musim hujan sementara untuk musim kemarau konsentrasi sedimen bernilai 0.0x10-3 kg/m3. Kata kunci : Model Numerik, Pergerakan Lumpur, Sungai Porong. Numerical model of MIKE 21 sediment transport module was applied to recognize the response of mud flow respective in rainy and dry season and also to get information of dike effect at the river mouth. Data that used in this simulation was tide, water depth, river discharge, current and sediment concentration. The simulations were created for two scenarios, therefore dry season and wet season. The result of the simulation model verified with observation data to see the correlation value. The verification are covering water level data and current magnitude of –x and –y axis. Based on the verification result, the correlation value of water level has a value 0.8641 meanwhile for the current the correlation value have magnitude 0.1493 of x-axis and 0.1917of y-axis. Moreover, the maximum value of sediment concentration could be seen at November 27th 2007 with 3.2x10-3 kg/m3 at the wet season and 0.0x10-3 kg/m3 for dry season. Keywords: Numerical Model, Mud Movement, Porong River

Suspended-sediment concentration and calibre in relation to surface-flow structure in Squamish River estuary, southwestern British Columbia

1989 ◽  
Vol 26 (10) ◽  
pp. 2172-2176 ◽  
Author(s):  
Kenneth M. Rood ◽  
Edward J. Hickin
Keyword(s):  
Dominant Role ◽  
Tidal Flow ◽  
River Estuary ◽  
Suspended Sediments ◽  
Sediment Concentration ◽  
Surface Flow ◽  
Particle Sizes ◽  
Background Flow ◽  
Grain Sizes ◽  
Tidal Phase

Surface grabs of suspended sediments from boils and the background flow in Squamish Estuary revealed strong differences between the two environments. Boils exhibit higher sediment concentrations and larger particle sizes than the background flow. The higher sediment concentrations and larger grain sizes in boils are related to tidal phase, with maximum concentrations and sediment sizes occurring in the early decelerating phase of the tidal flow. Sediment concentrations and grain sizes in the background flow are comparatively invariant with tidal phase. Boils appear to play an important, if not dominant, role in suspending and transporting sand-sized sediments in Squamish Estuary.

Crocodylus johnstoni and C. porosus Coexisting in a Tidal River

1983 ◽  
Vol 10 (3) ◽  
pp. 639 ◽  
Author(s):  
GJW Webb ◽  
SC Manolis ◽  
GC .Sack
Keyword(s):  
Competitive Exclusion ◽  
Dry Season ◽  
Tidal River ◽  
Main Stream ◽  
Wet Season ◽  
Seasonal Movements ◽  
Crocodylus Johnstoni ◽  
Seasonal Factors

A 52.5-km section of the Adelaide River, N.T. (12�13'S., 131�13'E.). was spotlight-surveyed 20 times between June 1979 and September 1981. C, johnstoni (15.3 � 9.2 sighted per survey) were less abundant than C. porosus (137.6 � 36.5 sighted per survey), and were mainly in the upstream 20 km of the survey route (96% of C. johnstoni sightings); here considered a zone of syntopy within the survey route. C. johnstoni congregate in the main stream during the dry season and disperse from it during the wet season, which parallels similar seasonal movements to and from dry-season refuges in non-tidal areas lacking C. porosus. As the dry season progresses, C. johnstoni are located further and further upstream, and this movement (or loss ofanimals) appears unrelated to changes in salinity. Numbers of C.johnstoni within the zone of syntopy are negatively correlated with numbers of C. porosus (r*2 = 0.50, P=0.005). and competitive exclusion may be occurring. Independent of seasonal factors, numbers of C. johnstoni within the zone of syntopy declined with consecutive month (1979-81: r*2=0.47, P= O.004), whereas numbers ofthe more recently protected C, porosus increased (r2 = 0.48, P= 0,006). The location of the syntopic zone was unchanged.

The Chao Phraya River Basin: water quality and anthropogenic influences

2018 ◽  
Vol 19 (5) ◽  
pp. 1287-1294 ◽  
Author(s):  
Nuanchan Singkran ◽  
Pitchaya Anantawong ◽  
Naree Intharawichian ◽  
Karika Kunta
Keyword(s):  
Water Quality ◽  
Land Use ◽  
River Basin ◽  
River Mouth ◽  
Oxygen Demand ◽  
Quality Parameters ◽  
Paddy Fields ◽  
Coliform Bacteria ◽  
Wet Season ◽  
Chao Phraya River

Abstract Land use influences and trends in water quality parameters were determined for the Chao Phraya River, Thailand. Dissolved oxygen (DO), biochemical oxygen demand (BOD), and nitrate-nitrogen (NO3-N) showed significant trends (R2 ≥ 0.5) across the year, while total phosphorus (TP) and faecal coliform bacteria (FCB) showed significant trends only in the wet season. DO increased, but BOD, NO3-N, and TP decreased, from the lower section (river kilometres (rkm) 7–58 from the river mouth) through the middle section (rkm 58–143) to the upper section (rkm 143–379) of the river. Lead and mercury showed weak/no trends (R2 < 0.5). Based on the river section, major land use groups were a combination of urban and built-up areas (43%) and aquaculture (21%) in the lower river basin, paddy fields (56%) and urban and built-up areas (21%) in the middle river basin, and paddy fields (44%) and other agricultural areas (34%) in the upper river basin. Most water quality and land use attributes had significantly positive or negative correlations (at P ≤ 0.05) among each other. The river was in crisis because of high FCB concentrations. Serious measures are suggested to manage FCB and relevant human activities in the river basin.

scholarly journals CALCULATION OF THE RATE OF NET ON-OFFSHORE SEDIMENT TRANSPORT ON THE BASIS OF FLUX CONCEPT

1984 ◽  
Vol 1 (19) ◽  
pp. 91 ◽  
Author(s):  
Ichiro Deguchi ◽  
Toru Sawaragi
Keyword(s):  
Sediment Transport ◽  
Water Depth ◽  
Sediment Concentration ◽  
Suspended Load ◽  
Spatial Variations ◽  
Sediment Flux ◽  
Bed Load ◽  
Two Dimensional ◽  
Dimensional Model ◽  
Two Dimensional Model

Time and spatial variations of sediment concentration of both bed load and suspended load in the process of two-dimensional beach deformation were investigated experimentally. At the same time, the relation between the velocities of water-particle and sediment migration was analyzed theoretically. By using those results,a net rate of on-offshore sediment_ transport in the process of two-dimensional model beach deformation qf was calculated on the basis of sediment flux. It is found that Qf coincides fairly well with .the net rate of on-offshore sediment transport calculated from the change of water depth.

scholarly journals VARIATION OF SEDIMENT SUSPENSION IN OSCILLATORY FLOW

1984 ◽  
Vol 1 (19) ◽  
pp. 155 ◽  
Author(s):  
Carsten Staub ◽  
Ivar G. Jonsson ◽  
Ib A. Svendsen
Keyword(s):  
Oscillatory Flow ◽  
Sediment Concentration ◽  
Suspended Load ◽  
Water Tunnel ◽  
Sediment Suspension ◽  
Suction Tube ◽  
The Mean ◽  
Characteristic Features ◽  
Mean Concentration ◽  
Different Levels

Different syphon type suspended load probes were used together with a newly developed 'carousel' sampler for measurements of the instantaneous sediment concentration in turbulent oscillatory flow over a sand bed. Shields parameters were well above the rippled/flat bed transition region, resulting in intense sediment transport over a flat bed. The measurements were performed at different levels in a large oscillating water tunnel. They showed some characteristic features of the temporal concentration variation and of the variation with height of the mean concentration. Also a pronounced effect of the orientation of the suction tube relative to the flow was observed.

scholarly journals The erosion–deposition process and associated control mechanisms of the Nanliu River subaqueous delta, Southern China coast

2019 ◽  
Vol 2 (1) ◽  
pp. 171-192 ◽  
Author(s):  
Zhen-Kun Lin ◽  
Ai-Jun Wang ◽  
Xiang Ye
Keyword(s):  
Suspended Sediment ◽  
Southern China ◽  
Sediment Resuspension ◽  
Field Measurements ◽  
Deposition Process ◽  
Sediment Concentration ◽  
Control Mechanisms ◽  
Erosion Coefficient ◽  
Deposition Processes ◽  
Dimensional Simulation

Understanding the erosion–deposition process of sediments and the associated controlling mechanisms in subaqueous deltas is important for coastal environment protection. In this study, field observations and numerical simulations were performed for the Nanliu River subaqueous delta in Guangxi Province (Southern China) to investigate the sediment dynamic processes at the bottom boundary layer. The results show that the sediment resuspension mainly occurs during periods of spring tides and is mainly controlled by the wave action. When the seabed is free from erosion, suspended sediment settling caused by lateral transport is an important source of maintaining near bed suspended sediment concentration. It was also found that increasing the shear parameter could facilitate the formation of flocs, after which the small flocs tend to merge to large flocs. Finally, by performing a consistency analysis between the seabed erosion and deposition processes obtained from numerical simulation, and the changes of seabed level recorded by the equipment during the field observation, we determined that the local erosion coefficient was 5 × 10−5 kg/m2·s. The one-dimensional simulation is also capable of revealing the general trend at the seabed where it is first subjected to erosion and then deposition, as indicated during the field measurements.

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