Determination of Settling Velocity of Suspended Sediment in Estuary

2014 ◽  
Vol 670-671 ◽  
pp. 805-808 ◽  
Author(s):  
Hui Ming Huang ◽  
Da Ke Chen ◽  
Wei Na Zhang ◽  
Cheng Chen
Keyword(s):  
Suspended Sediment ◽  
Settling Velocity ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
Cohesive Sediments ◽  
The Changjiang River ◽  
Sediment Particle Size ◽  
Logarithmic Distribution ◽  
Sediment Data

The settling velocity of sediment is a hot issue and a basic problem in study of sediment transport and estuarine engineering. According to field hydrodynamics and sediment data around the South Passage of the Changjiang River in China, this paper detected the characteristics of sediment particle size and vertical distribution pattern of suspended sediment concentration, and further estimated the settling velocity of suspended sediment in three methods. The results show that the sediments including suspended and bed load can be categorized into cohesive sediments and the sediment concentration profile agree well with logarithmic distribution. Furthermore, by comparison, it is found that the Rouse formula is more reasonable for estimating the settling velocity of fine sediment, but the Zhang Ruijin and Stokes formula obviously underestimate the values of settling velocity, caused by do not taking into account the flocculation of fine sediment in estuary.

scholarly journals Fine Sediment Modeling During Storm-Based Events in the River Bandon, Ireland

Water ◽  
2019 ◽  
Vol 11 (7) ◽  
pp. 1523 ◽  
Author(s):  
Juan T. García ◽  
Joseph R. Harrington
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Concentration ◽  
Fine Sediment ◽  
Storm Event ◽  
Storm Events ◽  
Event Scale ◽  
Model Based ◽  
Sediment Volume ◽  
Bed Erosion

The River Bandon located in County Cork (Ireland) has been time-continuously monitored by turbidity probes, as well as automatic and manual suspended sediment sampling. The current work evaluates three different models used to estimate the fine sediment concentration during storm-based events over a period of one year. The modeled suspended sediment concentration is compared with that measured at an event scale. Uncertainty indices are calculated and compared with those presented in the bibliography. An empirically-based model was used as a reference, as this model has been previously applied to evaluate sediment behavior over the same time period in the River Bandon. Three other models have been applied to the gathered data. First is an empirically-based storm events model, based on an exponential function for calculation of the sediment output from the bed. A statistically-based approach first developed for sewers was also evaluated. The third model evaluated was a shear stress erosion-based model based on one parameter. The importance of considering the fine sediment volume stored in the bed and its consolidation to predict the suspended sediment concentration during storm events is clearly evident. Taking into account dry weather periods and the bed erosion in previous events, knowledge on the eroded volume for each storm event is necessary to adjust the parameters for each model.

scholarly journals Comparison of Methods for Determining Erosion Threshold of Cohesive Sediments Using a Microcosm System

2021 ◽  
Vol 8 ◽  
Author(s):  
Hun Jun Ha ◽  
Ho Kyung Ha
Keyword(s):  
Suspended Sediment ◽  
Sediment Concentration ◽  
Surface Erosion ◽  
Intertidal Flat ◽  
Cohesive Sediments ◽  
Mean Values ◽  
Erosion Threshold ◽  
Mud Flat ◽  
Em Method ◽  
Tidal Emersion

Erosion of cohesive sediments is a ubiquitous phenomenon in estuarine and intertidal environments. Several methods have been proposed to determine the surface erosion threshold (τc0), which are still debatable because of the numerous and uncertain definitions. Based on erosion microcosm experiments, we have compared three different methods using (1) eroded mass (EM), (2) erosion rate (ER), and (3) suspended sediment concentration (SSC), and suggested a suitable method for revealing the variation of erodibility in intertidal sediments. Erosion experiments using a microcosm system were carried out in the Muuido tidal flat, west coast of South Korea. The mean values of τc0 for three methods were: 0.20 ± 0.08 Pa (EM); 0.18 ± 0.07 Pa (ER); and (3) 0.17 ± 0.09 Pa (SSC). The SSC method yielded the lowest τc0, due to the outflow of suspended sediment from the erosion chamber of the microcosm. This was because SSC gradually decreased with time after depleting the erodible sediment at a given bed shear stress (τb). Therefore, the regression between SSC and applied τb might skew an x-intercept, resulting in the underestimation (or “not-determined”) of τc0. The EM method yielded robust and accurate (within the range of τb step at which erosion begins) results. The EM method represents how the erodible depth thickens as τb increases and therefore seems better suited than the SSC and ER methods for representing depth-limited erosion of cohesive sediments. Furthermore, this study identified the spatiotemporal variations of τc0 by EM method in an intertidal flat. The τc0 in mud flat was about two times higher than that in mixed flat. Compared to the end of tidal emersion, the sediment was 10–40% more erodible at the beginning stage.

scholarly journals Sediment Dynamics in a Small, 2Nd Order Urban River Awba Catchment, Ibadan, Nigeria

2014 ◽  
Vol 7 (1-2) ◽  
pp. 23-28 ◽  
Author(s):  
Aderemi Adediji ◽  
Olutoyin A. Fashae
Keyword(s):  
Suspended Sediment ◽  
Suspended Sediment Concentration ◽  
Sediment Load ◽  
Sediment Concentration ◽  
Sediment Dynamics ◽  
Storm Flow ◽  
Weekly Sample ◽  
The University ◽  
Ibadan Nigeria

Abstract The sediment dynamics in a small 2nd order catchment of River Awba in the territory of the University of Ibadan, Nigeria was investigated between January and December 2012. The river was gauged by daily measurements of water level as well as sampling of water for determination of suspended sediment load. In this regard, apart from weekly sample, twelve (12) storm flow events which occurred during the day were sampled for determination of suspended sediment concentration. The results showed that during the storms the suspended sediment concentration varied between 636 mg/l in May and 3641.5 mg/l in September, with a mean of 2136.8 mg/l. Also, the value of monthly suspended sediment yield ranged from 10.85 kg in January to 288.4 kg in October with a mean of 89.5 kg. The variability in monthly sediment load closely followed the trend of monthly rainfall in the study area. However, in order to minimize the storm runoff and sediment load generated from the rainstorms events, the paved surfaces within the study catchment should be grassed with the planting of some few tree species. This could further reduce the rate of floods occurrence.

scholarly journals Unraveling the Essential Effects of Flocculation on Large-Scale Sediment Transport Patterns in a Tide-Dominated Estuary

2020 ◽  
Vol 50 (7) ◽  
pp. 1957-1981 ◽  
Author(s):  
Dante M. L. Horemans ◽  
Yoeri M. Dijkstra ◽  
Henk M. Schuttelaars ◽  
Patrick Meire ◽  
Tom J. S. Cox
Keyword(s):  
Sediment Transport ◽  
Suspended Sediment ◽  
Large Scale ◽  
Settling Velocity ◽  
Sediment Concentration ◽  
Order Effect ◽  
Temporal Variations ◽  
Small Scale ◽  
Estuarine Turbidity Maxima ◽  
The Impact

AbstractSediment transport in estuaries and the formation of estuarine turbidity maxima (ETM) highly depend on the ability of suspended particulate matter (SPM) to flocculate into larger aggregates. While most literature focuses on the small-scale impact of biological flocculants on the formation of larger aggregates, the influence of the flocculation process on large-scale estuarine SPM profiles is still largely unknown. In this paper, we study the impact of flocculation of SPM on the formation of ETM. For this, a semianalytical width-integrated model called iFlow is utilized and extended by a flocculation model. Starting from a complex one-class flocculation model, we show that flocculation may be described as a linear relation between settling velocity and suspended sediment concentration to capture its leading-order effect on the ETM formation. The model is applied to a winter case in the Scheldt estuary (Belgium, Netherlands) and calibrated to a unique, long-term, two-dimensional set of turbidity (cf. SPM) observations. First, model results with and without the effect of flocculation are compared, showing that the spatial and temporal variations of the settling velocity due to flocculation are essential to reproduce the observed magnitude of the suspended sediment concentrations and its dependence on river discharge. Second, flocculation results in tidally averaged land-inward sediment transport. Third, we conduct a sensitivity analysis of the freshwater discharge and floc breakup parameter, which shows that flocculation can cause additional estuarine turbidity maxima and can prevent flushing of the ETM for high freshwater inflow.

Application of Rouse Equation in Coastal Engineering

2013 ◽  
Vol 368-370 ◽  
pp. 1625-1628
Author(s):  
Cheng Chen ◽  
Yi Gang Wang ◽  
Hui Ming Huang ◽  
Qiong Pei Zeng ◽  
Chun Guang Yuan
Keyword(s):  
Water Depth ◽  
Vertical Profile ◽  
Settling Velocity ◽  
Sediment Concentration ◽  
Coastal Engineering ◽  
Two Dimensional ◽  
Constant Flow ◽  
Relative Water ◽  
Rouse Number ◽  
Sediment Data

The method to analysis the applicability of Rouse equation in Jiangsu coastal engineering is presented in this paper. The hydrological and sediment data in northern Jiangsu coastal area in August 2006 were adopted. Figure of sediment concentration changing with the relative water depth were made and analyzed. The result shows that the vertical profile of sediment concentration is similar with that under the conditions of equilibrium sediment transport in two-dimensional constant flow (exponential distribution). It can be concluded that the Rouse equation can be applied in the northern Jiangsu coastal engineering. In addition, the Rouse number and settling velocity are calculated in this paper.

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