Sediment Transport Calculations Research Articles

Effect of Flow Discharge on Sedimentation in Paneki River

Introduction: Paneki River has the potential for sedimentation caused by flow discharge. The condition of the river is getting wider every day which will threaten the risk of flooding if there is heavy rain with high intensity. The purpose of this study is to determine the return time flood discharge and basic sediment transport discharge in the Paneki river which can be used as a reference in planning sediment control buildings. Method: This research method includes primary data collection and secondary data collection, data management including calculating width, slope, design rainfall, design flood discharge, sieve analysis, and specific gravity. Then proceed to calculate the return time flood discharge using the Nakayasu synthetic unit hydrograph method and basic sediment transport using the Meyer-Peter and Muller method. Results and Discussion: From this research, the result of the 2-year return time flood discharge is 121.306 m3/det, for 5-year return time flood discharge is 185.069 m3 /det, for 10-year return time flood discharge is 209.261 m3 /det, for 25-year return time flood discharge is 312.359 m3 /det, and for 50-year return time flood discharge is 373.566 m3 /det. The results of basic sediment transport discharge per cross-section ranged from 0.0000861 m3 /det to 0.005641775 m3 /det. Conclusion: The study shows that sedimentation is influenced by flow discharge. The results of the calculation of flow discharge (Q) and bottom sediment transport (Qs) in Paneki River using the Meyer-Peter and Muller method resulted in Qs varying from 0.0000861 m³/det to 0.016551197 m³/det, according to the measured flow discharge. The greater the flow discharge, the greater the sediment transport, indicating a direct relationship between flow discharge and sedimentation.

Measurement and Calculation of Sediment Transport on an Ephemeral Stream

Sediment transport remains a significant challenge for researchers due to the intricate nature of the physical processes involved and the diverse characteristics of watercourses worldwide. A type of watercourse that is of particular interest for study is the ephemeral streams, found primarily in semiarid and arid regions. Due to their unique nature, a new measurement algorithm was created and a modified bed load sampler was built. Measurement of the bed load transport rate and calculation of the water discharge were conducted in an ephemeral stream in Northeastern Greece, where the mean calculated streamflow rate ranged from 0.019 to 0.314 m3/s, and the measured sediment load transport rates per unit width varied from 0.00001 to 0.00213 kg/m/s. The sediment concentration was determined through various methods, including nonlinear regression equations and formulas developed by Yang, with the coefficients of these formulas calibrated accordingly. The results demonstrated that the equations derived from Yang’s multiple regression analysis offered a superior fit compared to the original equations. As a result, two modified versions of Yang’s stream sediment transport formulas were developed and are presented to the readership. To assess the accuracy of the modified formulas, a comparison was conducted between the calculated total sediment concentrations and the measured total sediment concentrations based on various statistical criteria. The analysis shows that none of Yang’s original formulas fit the available data well, but after optimization, both modified formulas can be applied to the specific ephemeral stream. The results indicate also that the formulas derived from the nonlinear regression can be successfully used for the determination of the total sediment concentration in the ephemeral stream and have a better fit compared to Yang’s formulas. The correlation from the nonlinear regression equations suggests that total sediment transport is primarily influenced by water discharge and rainfall intensity, with the latter showing a high correlation coefficient of 0.998.

Współczynnik erozji gleby przy użyciu wielospektralnych wskaźników roślinności: Przykład zlewni rzeki Sarayardere (wschodnie Rodopy, Bułgaria)Wpływ zmian klimatu na środowisko zbudowane

Land cover/land use is one of the main factors influencing the development of soil erosion. It has been included in the calculation and modelling of erosion and sediment transport in many studies. In the current research NDVI (normalized difference vegetation index) and NDRE (normalized difference red edge index) are used for quantifying the cover management factor (C-factor). They are calculated on the base of Sentinel 2 multispectral images. Taking into account the vegetation phenology two time points were analyzed: end of May - June – active vegetation and September (beginning of October) – late vegetation. The changes in the values of the indices were considered for 2018, 2021 and 2022. The study area is the watershed of the river Sarayardere, located in the southern part of Bulgaria. This is a hilly to low-mountain area, prone to erosion due to rare vegetation, high slope gradients and a relatively long dry period followed by intensive rainfall. The calculated values of the C-factor are indicators for higher susceptibility to erosion in September than it is in June. The spatial distribution of the C-factor shows different patterns. The results, received on the base of the image of September 2021, show increasing the areas with C-factor < 0.1 and these ones > 0.5, in comparison with the results of September 2018. C-factor values calculated on the image of October 2022 indicate the highest susceptibility to erosion. Using NDRE instead NDVI results in slightly higher values of the C-factor. The advantage of the NDRE index is that it provides information on the content of chlorophyll in the vegetation during the end of the vegetation period and allows a more accurate assessment of the state of the separate plants, regarding the determination of diseased or damaged plants. In addition to the vegetation indices, an expert evaluation of the state of vegetation was done. The results of the current study show that the watershed of the river Sarayardere is in a relatively good condition regarding the development of erosion processes. The attention should be directed to the possible increase of erosion on deforested slopes and the availability of loose materials, in case of intense rainfall.

Development and application of an integrated methodology for post‐disaster field investigation of debris floods

AbstractDebris floods commonly occur in steep channels with an abundant sediment supply, and they can cause significant damage, primarily due to their higher sediment concentrations and negative impacts upon bank erosion, deep scouring and aggradation. These key hazards pose challenges for traditional assessment methods, making quantification difficult. This became obvious during a recent catastrophic debris flood that occurred on July 12, 2022, in the Heishuigou catchment (102 km2), northern Sichuan Province, China. In this case study, we developed an integrated methodology for assessing this debris flood event by incorporating field surveys, hydrological and hydraulic modelling and sediment transport calculations. Detailed information such as topographic maps, photographs, deposits, grain size distributions and inundation depths was collected to analyse the material sources, validate the parameters and conduct model calculations. The peak debris flood discharge and the supra‐critical bed shear stress ratios, estimated from hydrological and dynamic models, were incorporated to analyse the debris flood's typology and characterize its destructive mechanisms. The regional frequency–volume relationship established through bedload transport calculations was calibrated using the volume of the deposits determined via field investigation. These methods not only contribute to a comprehensive understanding of debris floods but also provide valuable support for future risk assessments and mitigation designs.

Advp Measurements Of Flow Over Low-Angle Bedforms In A Laboratory Flume Setup

In many coastal and estuarine environments, bedforms develop due to the complex interactions between hydrodynamics, sediment transport and morphology which affect hydro-morphodynamic processes at various spatio-temporal scales. Furthermore, bedforms are considered main drivers of flow resistance via turbulence and affect near bottom processes such as bed roughness, bottom shear stress and turbulent structures. A detailed study and characterisation of flow over bedforms is therefore significant to many fundamental and engineering applications such as sediment transport calculation and prediction, channel managements, or burial of submarine cables. Asymmetric dunes with an angle-of-repose (30°) lee side have been well studied (Best, 2005; Venditti, 2013). They are representative of dunes commonly found in laboratory flumes and small rivers. Over such bedforms, flow is characterised by a permanent flow separation zone and intense turbulence over their lee side. Recently, it was shown that bedforms in large rivers are mainly low- to intermediate-angle dunes (mean lee side ca. 5-20°) having their steepest slope located close to the trough (Cisneros et al., 2020). Over such low- and intermediate-angle river dunes, flow separation is inexistent or intermittent and only little turbulence is generated (e.g. Kwoll et al., 2016; Lefebvre and Cisneros, 2023). Estuarine bedforms also possess mostly low- to intermediate-angle mean lee slopes between 5° and 20° (Dalrymple and Rhodes, 1995; Lefebvre et al., 2021). However, contrary to river bedforms, estuarine bedforms usually have a sharp pointed crest with the steepest slope situated near the crest and a relatively flat trough (Aliotta and Perillo, 1987; Lefebvre et al., 2021). It is not clear yet how much flow properties vary between high-angle flat-crested dunes and low-angle sharp-crested dunes. In particular, it is unknown whether a permanent or an intermittent flow separation can be observed over some segments of the lee side. Furthermore, the relation between the reversing tidal flow and natural estuarine morphology is not well understood yet. In this study, laboratory flume experiments will be conducted to measure the mean flow and turbulence over estuarine bedforms. Previous experiments performed by Carstensen and Holzwarth (2023) demonstrated the potential of high-resolution measurements over a large-scale estuarine dune in a laboratory flume. Building on this, experiments will be carried out over a fixed concrete low- and intermediate- angle estuarine bedform field. The results from this study can be used to characterise in detail the flow dynamics over estuarine bedforms.

Numerical Modeling of Sediment Transport and Bed Evolution in Nonuniform Open-Channel Flows

Abstract The shallow-water and multilayer hydrostatic models have been commonly used to analyze the problems of a sediment-laden, plane open-channel flow. The models are adequate to solve a quasi-hydrostatic flow problem, but their accuracy deteriorates as the e ects of the vertical acceleration gain in significance. Herein, a higher-order numerical model for treating the problems of unsteady, plane open-channel flow over a movable bed is proposed. In this model, the flow hydrodynamics is governed by the depth-averaged Boussinesq-type equations, and the bed morphodynamics is determined by an Exner-type equation and additional equations describing the non-equilibrium transports of suspended load and bed load. A hybrid finite-volume and finite-di erence scheme was used to discretize and solve the governing equations, yielding solutions that are in satisfactory agreement with the experimental data. Overall, the results of the proposed model for the temporal free-surface profile and bed evolution were fairly adequate. For the two particular cases considered, however, the quality of its results was moderately a ected by the e ects of the three-dimensional characteristics of the dam-break flow and the sliding of the dike body due to sub-surface flow. The results of this investigation highlight the importance of including a higher-order Boussinesq-type correction for refining sediment transport computations.

Angkutan Sedimen Total Saluran Pembawa Embung Rawasari menggunakan Metode Empiris dan Software HEC-RAS 6.0

The need for water will continue to increase, while the availability of water is limited; therefore, the provision of water must be pursued both by the government and independently. Rawasari Reservoir is one of the reservoirs in Tarakan City with a relatively stable volume and an effective storage capacity of 112,982 m3. The water source of Rawasari Reservoir comes from a channel that is a tributary experiencing sedimentation due to the sedimentation process. Based on this, the research team was interested in calculating sediment transport in the conveyance channel of Rawasari Reservoir using both empirical methods and the HEC-RAS 6.0 software. The methods used in this research are empirical using the Engelund Hansen and Laursen equations, as well as the use of HEC-RAS 6.0 software. Based on the analysis results, the sediment transport rate in the conveyance channel of Rawasari Reservoir calculated using the empirical method at STA 0+025 is 1,6427 x 10-9 ton/s for the Engelund Hansen method and 2,9898 x 10-9 ton/s for the Laursen method. The simulation of sediment transport in the bed of the conveyance channel of Rawasari Reservoir using the HEC-RAS 6.0 sediment transport model at STA 0+025 is 4,61x10-5 ton/s with the Engelund Hansen sediment transport function and 0,000306 ton/s using the Laursen sediment transport function.

Modeling Sediment Resuspension and Transport Processes Induced by Propeller Wash from Ship Traffic

Resuspension and redistribution of sediments induced by propeller wash may significantly influence aquatic ecosystems at contaminated sediment sites. This study describes a numerical modeling method developed to predict the sediment resuspension and subsequent transport processes resulting from ship traffic, with a fully coupled simulation of hydrodynamics, sediment transport, and propeller wash. By including propeller momentum effects in the flow field computation, the advection and dispersion of resuspended sediments are better represented than in previously available methods. To achieve this improvement, a computational algorithm was first developed to calculate the propeller wash effects from one or more ships (e.g., erosion rate and momentum flux); these results were then dynamically linked to a hydrodynamic and sediment transport computation using Environmental Fluid Dynamics Code Plus (EFDC+). This modeling framework was evaluated using a field experiment conducted by the US Navy. The model was calibrated with flow velocities and sediment erosion depths, and then validated with resuspended sediment concentrations in the water column. The model results reproduced the horizontal and vertical distributions of resuspended sediments better when the propeller-induced momentum was incorporated into the flow field computation. The sensitivity test indicated that the increased flow energy from propeller momentum resulted in significant dispersion of resuspended sediments in both longitudinal and lateral directions. The maximum scour was dependent on the propeller revolution speed, the ship engine power, and the distance between the propellers and the sediment bed.

Analisis Karakteristik Dan Laju Angkutan Sedimen Total Saluran Rawasari Indah Kota Tarakan

Embung as one of the waterworks that serves as a reservoir for water, Embung Rawasari Indah is one of the 5 reservoirs in Tarakan yann city currently experiencing silting due to sedimentation process, which causes the water discharge flowing towards the reservoir to be not optimal. The purpose of this study was to determine the characteristics and discharge of total sediment transport in Rawasari indah Channel and obtain a comparison of three methods of calculating the total sediment transport in Rawasari Indah Channel. Based on the results of laboratory tests sediment classification is dominated by fine sand, very fine sand and medium sand. The results of the study obtained the average value of sediment transport discharge on Engelund and Hansen's method is 1.382998513 tons/year, the method is 15.88046241 tons/year, Laursen method is 2.000124533 tons / year. Based on the calculation results with the largest value, the method chosen as a benchmark in the calculation of sediment transport.

Comparative Study of Sediment Transport using the Caldwell and Cerc Methods at the Donggala Fish Landing Base

Donggala Fish Landing Port (PPI) is a fish port located in Central Sulawesi, precisely in Labuan Bajo Village, Banawa District, Donggala Regency, which is located along the high seas coast. The change in shoreline at the Donggala Fish Landing Base is caused by sediment transport that occurs due to wind and incoming waves. This study aims to determine the sediment characteristics, the amount of longshore sediment transport that occurs per year, and the ratio of the amount of sediment transport for 10 years using the Caldwell method and the CERC method. Analysis of sediment characteristics was carried out by testing carried out in the laboratory with the analyzed parameters, namely: sediment density, sediment grain size distribution and sedimentation velocity. There are many methods that can be used to calculate sediment transport, including the Caldwell method and the CERC method. The results of the sedimentation analysis, it is found that the sediment fraction is sand with various diameters, namely ϕmin = 0.075 mm and ϕmax = 25 mm, sediment density γmin = 2,604 g/cm3 and γmax = 2,678 g/cm3 and sedimentation velocity Wmin = 0.251 m/s and Wmax = 9,946 m/s. From the calculation of sediment transport analysis using the Caldwell method, the maximum amount of sediment transport that occurred in 2009 was 0,956 m3/year and for the CERC method, the maximum amount of sediment transport occurred in 2009 was 0,210 m3/year. The calculation of sediment transport analysis that was reviewed for 10 years, the value obtained by the Caldwell method Qs = 3,353 m3/year, while the CERC method Qs = 0,705 m3/year so that the amount of sediment transport using the Caldwell method is greater than using the CERC method.

Application of Hydrological Modeling Related to the 2011 Disaster in the Mountainous Region of Rio De Janeiro, Brazil

Natural disasters have been responsible for thousands of deaths in recent decades that, added to the environmental, social and economic impacts, require the implementation of prevention strategies. The largest share of disasters is of hydrological origin. In this context, hydrological models are potential alternatives for monitoring and preventing events of this nature. The objective of this study was to analyze the applicability of the semi-distributed model SWAT (Soil and Water Assessment Tool) and the concentrated model SMAP (soil moisture accounting procedure) in predicting the extreme flood event that occurred in Brazil in the mountainous region of Rio de Janeiro in 2011. The results showed that the mean relative error in calibration and validation was 12% and 53% for SMAP, and 18.46% and 88.73% for SWAT, respectively. The better performance of SMAP in validation integrated with its ease of data collection, simplicity of execution and semi-automatic calibration included in its routine, allows for the conclusion that this model proved to be more suitable for hydrological monitoring. In this study, for the first time, a model of SWAT’s complexity was applied to a watershed located in the mountainous region of the state of Rio de Janeiro, a region that, unfortunately, has accounted for thousands of deaths over the past decades associated with mass movements and floods. The SWAT model, besides being able to predict the level and flow of the main course of the river and its tributaries, also enables the calculation of sediment transport in extreme events. Looking from an operational point of view, the work clearly shows how poor hydro-meteorological monitoring, as is the case in this region, makes a good quality prediction for extreme events impossible. It was demonstrated that under these conditions, a simpler and concentrated modeling approach, such as the SMAP model, is able to obtain better results than SWAT.

Transport of Sediment Mixtures in Steady Flow with an Extra Contribution of Their Finest Fractions: Laboratory Tests and Modeling

This paper presents the results of experimental studies on the transport of water-sandy mixtures with the content of very fine non-cohesive fractions in steady flow. The flow and shear velocity measurements as well as the measurements of sediment amount in the trap and control area were conducted. A theoretical model of the vertical structure of both velocity and concentration of sediment non-cohesive fractions as well as vertical mixing and sorting is presented here for transport calculations. The interaction effects between fractions are included, especially the influence of fine fractions in the mixture on transport of coarser fractions. The model provides an agreement between measurements and calculations of transport rate and grain size distributions of poorly sorted mixtures within plus/minus a coefficient of two. Further, the present model is used for calculating the limited contribution of very fine fractions in sediment due to deficit of those fractions in the bed. Again, the compliance of the calculations of sediment transport according to measurements is achieved. The satisfactory agreement between the calculations of grain size distributions and measurements is also found.

An Experimental Study on Progressive and Reverse Fluxes of Sediments with Fine Fractions in the Wave Motion over Sloped Bed

The purpose of the study was to collect experimental data on the vertical structure of sediment fluxes during the wave crest and trough phase over sloped bed. The first stage of the experimental work included measurements of these fluxes using the particle image method, while the second stage, measurements of sediment transport rates and granulometric distributions of sediments collected in the traps on both sides of the sloped initial area. The experimental data were compared both with the results collected previously over flat bed as well as with a theoretical analysis based on a three-layer model of graded sediment transport. This model does not take into account the effects related to the presence of fine and very fine fractions and neglects the effects related to the bed slope, i.e., to gravitational forces and to additional pressure gradients. Hence, a modification of this model is proposed that is based on four coefficients that corrected for sediment fluxes over sloped bed. The consistency of the sediment transport calculations according to the modified model with measurements was achieved within plus/minus a factor of 2 of the measurements.

Modeling of 1D sediment transport in the langat river using quasi-unsteady HEC-RAS

The primary goal of this research was to investigate the sediment transport characteristics of the Langat River. The Langat River is situated in the state of Selangor, Malaysia, and is prone to flooding on a regular basis. The River Analysis System tool from the Hydraulic Engineering Center (HEC-RAS) was used to determine the sediment transport capacity of the river. The sediment transport and hydraulic models were created using elevation and cross-sectional data in HEC-RAS. The sediment transport model employed several approaches to calculate sediment transport capacity. HEC-RAS contains some useful built-in functions which were used in this study to visualize the sediment transport, calibration and calculation of Manning’s roughness coefficients, and forecast changes in bed elevation. The investigation reveals that urban development has resulted in a large rise in riverbed depth, implying that is no difference in flooding pattern in the short period of time. This paper focuses only on bed load sediment. The results of three years of stream flow show that some areas have experienced silt transport and river deposition. The river had changed slightly after utilizing the Laursen-Copeland method in HEC-RAS. The simulation outcome shows the segment that experienced sediment transport at River Stations RS 12926 from Lui, RS 9362 from Langat upper reach, and RS 3730 from Langat Lower Reach are experiencing sediment deposition activities.

Parameter Calibration of Sediment Transport Capacity Formula of the Third Entrance of Xinqiman Reservoir in Tarim River Based on CCHE2D Model

In this study, sediment transport at the third entrance of the Xinqiman Reservoir in the Tarim River was simulated using the CCHE2D model. The flow conditions, the suspended sediment concentration of each grain size, and the boundary grain size of the wash load in the reach were determined. Regressions between the suspended sediment concentration, S, and flow condition, U3/gH, and flow-sediment factor, U3/Rω, were developed, which strongly adhered to the power law and Zhang Ruijin’s formula for the sediment transport capacity. The parameters in Zhang Ruijin’s formula for the target reach were determined. Under the defined flow and sediment conditions, sediment particles ≥0.091 mm and particles ≤0.061 can be regarded as the bed material and wash loads, respectively. Using multivariate linear regression, the sediment transport capacity coefficient (k0) and exponent (m) were determined to be 0.0197 and 0.928, respectively. These results can serve as an important theoretical reference for the calculation of sediment transport at the third entrance of the Xinqiman Reservoir in the Tarim River.

An Experimental Study on Progressive and Reverse Fluxes of Sediments with Fine Fractions in Wave Motion

The purpose of the study was to collect experimental data on the vertical structure of sediment fluxes during the wave crest and trough phase. The first stage of the experimental work included measurements of these fluxes using the particle image method, while in the second stage, measurements of sediment transport rates and granulometric distributions of sediments were collected in the traps on both sides of the initial area. The experimental data were compared with the results of a theoretical analysis based on a three-layer model of graded sediment transport. The comparison of the calculations with the measurements was conducted separately for fluxes of fine and very fine fractions in the diameter range di < 0.20 mm, coarse, and total fractions all outgoing in the crest and trough phase from the initial area and deposited in adjacent control areas. As this model did not take into account both the effects of vertical mixing and the phase-lag effects related to the presence of fine and very fine fractions, a modification of this model was proposed that was based on four coefficients that corrected for fluxes. The consistency of the sediment transport calculations according to the modified model with measurements was achieved within plus/minus a factor of 2 of the measurements.

Application of ROMS-SWAN coupled model to simulate hydrodynamic field in Hai Phong

ROMS and SWAN models have been used quite commonly in studying hydrodynamics. These are open-source models which are suitable for development research. However, using the ROMS-SWAN coupled model has not been studied and applied much in Vietnam. This paper presents the study and use of the ROMS-SWAN coupled model in the COAWST system to calculate the hydrodynamic field in Hai Phong at a primitive level. The calculation gives quite good results when compared with the measured data. The results of this study are the basis for the application of the COAWST model system to calculate sediment transport.

Bed Load Transport and Alternation of a Gravel-Bed River Morphology within a Vicinity of Block Ramp: Classical and Numerical Approach

In current river management, we very often use environment-friendly hydraulic structures when it is required for river bed or river bank protection due to erosion of a river channel. Block ramps are one of many methods used to stabilize river beds. They provide a semi-natural solution to certain river engineering problems in mountain streams. When building block ramps, one can use the dissipative behavior of large rock blocks or boulder elements randomly placed on the river bed to enhance fish migration in an upstream direction; thus, they can serve as fish passes. In this paper, we present the results of the numerical modelling of a bed load transport and the morphological changes of a river bed where a block ramp was designed and built. The main aim of the study was to investigate the difference of 2D modelling of a bed load transport along the mountain stream reach with boulder ramps in comparison to the classical methods of Hjulström, Shields, and Russian standard ST-24-2396. The work was carried out on the stream of one of the chosen low-head hydraulic structures, where 25 identical block ramps were constructed for river training reasons. The novel approach of our study is, for the first time in the field, to show a very detailed analysis of block ramp influence on sediment transport and river morphology changes compared to the classical understanding of those phenomena, as well as 2D model results to give hydraulic engineers an inside look into classical and modern approaches of bed load transport calculations. This might be helpful for designing such kinds of hydraulic structures in the future, in all regions where sediment transport calculations are important but do not always require sophisticated modelling.

Assessment of BSL kω Turbulence Model for Predicting Flow Characteristics in a Solitary Wave Motion

A deep understanding of boundary layer characteristics under wave motion, especially bottom shear stress on the seabed, is critical in sediment transport calculation and modeling. In this present study, boundary layer characteristics under solitary wave motion over the smooth bed are investigated through the Baseline (BSL) kω model. It will also consider the result of a laboratory experiment performed in a closed conduit generation system. The conclusion said that the BSL kω model can replicate well on horizontal and vertical velocity distribution at Reynolds number (Re) = 2.25 x 105. In addition, a turbulent spike which was occurred during decelerating phases of oscillatory motion can be predicted well also by the BSL kω model at Reynolds number (Re) = 6.06 x 105.

The Rapidly Evolving Fudu Estuary Sandbar Lagoon Landform on the East Coast of the Bohai Sea: Recent Changes and Mechanism

The Fudu Estuary Sandbar Lagoon is one of the most representative sandbar-lagoon landforms in China, and has undergone drastic evolution in recent years, accompanied by increased coastal engineering activities. The evolution process and its control factors are studied through remote sensing interpretation and coastal sediment transport calculations. During 2010–2021, the sandbar quickly extended at an average speed of 49.5 m/a, but the annual growth has shown a decreasing trend in both area and width, and the shoreline has retreated by 25–45 m. The recent changes are the result of the combined action of natural conditions and human activities. Coastal sediment transport from west to east under the action of W-oriented waves is the natural cause of extension. An estuary dam and artificial island block the sediment transport path, and the material for the new growth of the sandbar comes from the erosion of its west side, which has directly caused the retreat and narrowing of the sandbar. The reduction in sediments from the river further aggravates the shrinkage. It is predicted that the sandbar will continue its eastward extension to connect with the coast in about 2–3 years. The erosion status is unlikely to change before the sediment supply is restored. Measures such as dismantling the estuary dam are recommended.