• Korean Journal of Environmental Agriculture
• /
• v.30 no.3
• /
• pp.268-274
• /
• 2011

BACKGROUND: A large scale of sediment load delivered from watershed causes substantial waterway damages and water quality degradation. Controlling sediment loading requires the knowledge of the soil erosion and sedimentation. The various factors such as watershed size, slope, climate, land use may affect sediment delivery processes. Traditionally sediment delivery ratio prediction equations have been developed by relating watershed characteristics to measured sediment yield divided by predicted gross erosion. However, sediment prediction equations have been developed for only a few regions because of limited sediment data. Besides, little research has been done on the prediction of sediment delivery ratio for asia monsoon period in mountainous watershed. METHODS AND RESULTS: In this study Tank model was expanded and applied for estimating sediment yield to Oship River of east coast. The rainfall-runoff in 2006 was verified using the Tank model and we derived good result between observed and calculated discharge in 2009 at the same conditions. In relation to sediment yield, the sediment delivery rate of 2006 was very high than 2009 regardless of methods for estimating sediment load. It was thought to be affected by heavy rainfall due to the typhoon. CONCLUSION(s): For estimating sediment volume from watershed, long-term monitoring data on discharge and sediment is needed. This model will be able to apply to predict discharge and sediment yield simultaneously in ungauged area. This approach is more effective and less expensive method than the traditional method which needs a lot of data collection.

• Economic and Environmental Geology
• /
• v.27 no.6
• /
• pp.579-592
• /
• 1994

A case study is presented where a fluvial system is modeled in three dimensions and compared to data gathered from a study of the Arkansas River. The data is unique in that it documents changes that affected a straight channel that was excavated within the river by the U.S. Army Corps of Engineers. Excavation plan maps and sequential aerial photographs show that the channel underwent massive deposition and channel migration as it returned to a more natural, meandering path. These records illustrate that stability of fluvial system can be disrupted either by catastrophic events such as floods or by subtle events such as the altering of a stream's equilibrium base level or sediment load. SEDSIM, Stanford's Sedimentary Basin Simulation Model, is modified and used to model the Arkansas River and the geologic processes that changed in response to changing hydraulic and geologic parameters resulting from the excavation of the channel. Geologic parameters such as fluid and sediment discharge, velocity, transport capacity, and sediment load are input into the model. These parameters regulate the frequency distribution and sizes of sediment grains that are eroded, transported and deposited. The experiments compare favorably with field data, recreating similar patterns of fluid flow and sedimentation. Therefore, simulations provide insight for understanding and spatial distribution of sediment bodies in fluvial deposits and the internal sedimentary structure of fluvial reservoirs. These techniques of graphic simulation can be contributed to support the development of the new design criteria compatible with natural stream processes, espacially drainage problem to minimize environmental disruption.

• Journal of Korean Society of Environmental Engineers
• /
• v.33 no.1
• /
• pp.9-15
• /
• 2011

The first objective of this study was to investigate water pollution status of Meejae Reservoir, Kunsan, irregularly receiving river water for agricultural and recreational purposes. The second objective of the study was to compare nutrient pollution loads of three nutrient sources: sediment leaching, non-point sources and the receiving water. Water analysis results showed that eutrophication was a concern especially in summer and the calculated TSI (secchi depth), TSI (chlorophyll-a), and TSI (TP) were 53.6, 57.7 and 56.7, respectively. Although there was no significant difference in seasonal mean values of sediment T-N, sediment T-P and sediment organic content, mean differences were found for sampling points. However, T-N and T-P sediment release flux showed seasonal mean differences, while showing no mean difference for sampling points. Water T-N data proportionally correlated with sediment T-N and sediment organic content data, while no statistical correlation was found for water T-P data. Comparison of nutrient loads calculated from three sources showed that the highest T-N load was occurred from the receiving (pumped) water while T-P loads of the receiving water and sediment release flux were similar. The first solution would be considered for the receiving water to improve the water quality of Meejae Reservoir. Reduction of nutrient flux from the sediment would be then tried as the second alternative solution.

• Journal of the Korean Association of Geographic Information Studies
• /
• v.12 no.2
• /
• pp.82-98
• /
• 2009

This study applied SWAT model to analyze suspended sediment load that is influence on the high density turbid water in Donghyang and Cheoncheon basin, which are located in the upstream of Yongdam Dam. GIS data such as DEM, land cover map and soil map, and meteorological data were used as the input data of SWAT model. And the rating curve equation and Q-SS equation of Donghyang and Cheoncheon gauge station were applied as the measured values of them. As the result of flowout, the coefficient of determination ($R^2$) and the Nash-Sutcliffe coefficient of efficiency (EI) of model calibration showed high as 0.87 and 0.87 at Donghyang gauge station, and the $R^2$ and EI of model validation were high as 0.95 at Cheoncheon gauge station. Also, as the result of suspended sediment load, the $R^2$ and EI of model calibration were high as 0.77 and 0.76 at Donghyang gauge station, and the $R^2$ and EI of model validation marked high as 0.867 and 0.80 at Cheoncheon gauge station. It is considered that the suspended sediment load of 2003 showed the highest due to rainfall amounts and rainfall intensity in using SWAT model. The results of suspended sediment modeled in this study can be applied to the decision-making support data for the evaluation of soil erosion possibility and turbid water potential in the management of reservoir.

• Journal of Korea Water Resources Association
• /
• v.33 no.4
• /
• pp.461-469
• /
• 2000

An numerical analysis of sediment-laden flow is carried out, and results are compared with the experiments of Coleman(1981, 1986) that included the several cases varying sediment size and quantity in open channel flow. K-$\omega$ turbulence model is selected for the fully turbulent flow field, and the concentration equation considering the fall velocity is adopted for the concentration field. The model of Einstein and Chien(1955) is applied to couple the velocity field and the concentration field. Most of researches have been carried out without considering the bed-load thickness, but it is found that the bed-load thickness cannot be ignored in case of a large amount of sediment or a large size of it. The bed-load thickness and surface roughness are considered in this study. Here, $\beta$ value, which is defined by the reciprocal of turbulent Schmidt number and is related with the concentration profile, is found to be varied according to the sediment size and quantity. Even though most of researchers have insisted that $\beta$ had always larger than 1.0, it may be concluded that $\beta$ can have smaller value than 1.0, that is coincident with the report of recent research.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.25 no.6
• /
• pp.405-411
• /
• 2013

A sediment transport calculation considering cohesive force is proposed to deal with the transport phenomena of cohesive sediment. In the proposed calculation, each sand particle is assumed to be surrounded by a thin layer of mud. The critical Shields parameter and bed-load sediment transport rate are modified to include the cohesive force acting on the sand particle. The proposed calculation is incorporated into a two-way coupled fluid-structure-sediment interaction model, and applied to wave-induced topographic change of artificial shallows. Numerical results show that an increase in the content ratio of the mud, cohesive resistance force per unit surface area and water content cause increases in the critical Shields parameter and decreases in the bed-load sediment transport rate, reducing the topographic change of the shallow without changing its trend. This suggests that mixing mud in the pores of the sand particles can reduce the topographic change of shallows.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.56 no.5
• /
• pp.21-27
• /
• 2014

Sediment-laden water is problematic in aquatic ecosystem and for hydraulic structures in a watershed, and agriculture area in a watershed is one of source areas of nonpoint source (NPS), since soil surface typically exposures due to agricultural activities. Especially, severe sediment might flow into stream when agricultural area is located near stream like the Imha-dam watershed. Soil erosion is affected by precipitation, therefore there is a need to consider precipitation characteristics in soil erosion and best management practices (BMPs) simulation. The Web-based Spreadsheet Tool for the Estimation of Pollutant Load (STEPL WEB) allows estimating long-term sediment loads and the impact of best management practices to reduce sediment loads. STEPL WEB and predicted precipitation data by MIROC-ESM model was used to estimate sediment loads and its reduction by filter strip and conversion of agricultural area to forest in the future 30 years. The result indicates that approximately 70 % of agricultural area requires filter strip installation or that approximately 50 % of agricultural area needs to be converted to forest, for 41 % of sediment load reduction.

• Journal of Soil and Groundwater Environment
• /
• v.12 no.3
• /
• pp.1-9
• /
• 2007

As Total Maximum Daily Load program is being implemented, needs for the management and treatment of contaminated sediment are rising to attain cleaner water resources. In this paper, impacts and management methods of contaminated sediment were reviewed. Remediation technologies for contaminated sediment including dredging, natural attenuation, in situ solidification/stabilization, in situ biological remediation, in situ chemical remediation and capping were reviewed. Integrated remediation scheme was presented as well.

• Journal of Korean Society of Water and Wastewater
• /
• v.11 no.4
• /
• pp.99-109
• /
• 1997

To estimate the nutrients delivery characteristics of Chogang stream to Keum River, sediment and soil characteristics were analyzed in the stream and in the stream bank. Along the stream, soil samples from river sediment were collected and tested monthly for phosphorus and nitrogen concentrations. Nitrogen concentration in the sediment is much lower than that of soil in the river bank especially in summer presumably due to the high desorption characteristics of nitrogen by the increasing rainfall energy during summer. Instead, the concentrations of phosphorus were similar for the sediment and the soil in the river bank due to the strong adsorption characteristics of phosphorus. Batch tests were performed to evaluate the desorption potential of the sediments. Universal Soil Loss Equation (USLE) was applied to quantify soil erosion in each watershed due to rainfall. It was estimated that approximately 25% of total phosphorus by mass basis could be released from the sediment if the water was disturbed vigorously. The mass load of nitrogen and phosphorus into the Chogang Stream from the watershed were evaluated from the USLE and release ratio of phosphorus.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.7 no.3
• /
• pp.277-288
• /
• 1995

Prediction of turbidity due to fine-grained bed material load under wave action is critical to any assessment of anthropogenic impart on the coastal or lacustrine environment Waves tend to loosen mud deposits and generate steep suspension concentration gradients, such that the sediment load near the bottom is typically orders of magnitude higher than that near the surface. In a physically realistic but simplified manner, a simple mass conservation principle has been used to simulate the evolution of fine sediment concentration profiles and corresponding erodible bed depths under progressive, nonbreaking wave action over mud deposits. Prior field observations support the simulated trends. which reveal the genesis of a near-bed. high concentration fluidized mud layer coupled with very low surficial sediment concentrations. It is concluded that estimation of the depth of bottom erosion requires an understanding of mud dynamics and competent in situ sediment concentration profiling. Measurement of sediment concentration at the surface alone, without regard to the near-bed zone, can lead to gross underestimation of the erodible bed depth.