• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.454-458
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• 2007

Nonpoint source (NPS) pollution is a serious problem causing the degradation of soil and water quality. Concentrated overland flow is the primary transport mechanism for a large amount of NPS pollutants from hillslope areas to downslope areas in a watershed. In this study, a soil erosion model, nLS model, to identify transitional overland flow regions (i.e., ephemeral gully head areas) was developed using the kinematic wave overland flow theory. Spatial data, including digital elevation models (DEMs), soil, and landcover, were used in the GIS-based model algorithm. The model was calibrated and validated using gully head locations in a large agricultural watershed, which were identified using 1-m aerial photography. The model performance was better than two previous approaches; the overall accuracy of the nLS model was 72 % to 87 % in one calibration subwatershed and the mean overall accuracy was 75 to 89 % in four validation subwatersheds, showing that the model well predicted potential transitional erosion areas at different watersheds. However, the user accuracy in calibration and validation was still low. To improve the user accuracy and study the effects of DEM resolution, finer resolution DEMs may be preferred because DEM grid is strongly sensitive to estimating model parameters. Information gained from this study can improve assessing soil erosion process due to concentrated overland flow as well as analyze the effect of microtopographic landscapes, such as riparian buffer areas, in NPS control.

• Journal of Wetlands Research
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• v.16 no.2
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• pp.221-233
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• 2014

Soil erosion, transportation, and sedimentation by water flow often occur in a stream. This excessive occurrence threatens the safety of hydraulic structures, and aggravates natural disasters like flood. To prevent soil disaster according to the soil erosion, it is necessary to predict accurate sediment outflow primarily. Besides, it is very important to choose appropriate models by basin characteristics, to estimate accurate quantity of related factors, and to acquire available hydrological data. Therefore, the purpose of this study is to estimate soil erosion amount and sediment amount according to rainfall-runoff by using rainfall, discharge, and sediment in the Seolmacheon experimental catchment. And, it proposed sediment delivery ratio of the Seolmacheon catchment by result of studying sediment delivery ratio. Hereafter, this study will estimate sediment delivery ratio by basin characteristics, and formulate the method of estimating soil erosion and sediment outflow in various conditions by applying the results in other catchments.

• Magazine of the Korean Society of Agricultural Engineers
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• v.39 no.4
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• pp.82-89
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• 1997

A physically-based soil-water erosion model with simple hydrology and Rose & Hairsine's erosion concept is described, and was implemented in the form of computer program. The model derived from the concept of stream power(Bagnold, 1977) considers settling velocity characteristics of the soil and distinguishes between the processes of entrainment and re-entrainment. It deals separately with rill flow and sheet flow, handles vegetation in terms of soil contact cover, and has the ability to simulate soil movement on nonuniform slopes. The model predicted sediment concentrations reasonably with the results of Mclsaac et al. (1990). It showed a capability to quantitatively predict the movement of soil on uniform and nonuniform slopes. Among the model parameters, soil depositability $({\phi})$ was the most sensitive from the sensitivity analysis.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.126-131
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• 2007

The Imha watershed is vulnerable to severe erosion due to the topographical characteristics such as mountainous steep slopes. The RUSLE model was combined with GIS techniques to analyze the mean annual erosion losses and the soil losses caused by typhoon "Maemi". The model is used to evaluate the spatial distribution of soil loss rates under different land uses. The mean annual soil loss rate and soil losses caused by typhoon "Maemi"were predicted as $3,450\;tons/km^2/year$ and $2,920\;ton/km^2/"Maemi"$, respectively. The sediment delivery ratio was determined to be about 25% from the mean annual soil loss rate and the surveyed sediment deposits in the Imha reservoir in 1997.

• Proceedings of the Korea Water Resources Association Conference
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• 2006.05a
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• pp.333-337
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• 2006

The purpose of this paper is to present a strategic approach to selecting prior areas of soil erosion to be examined for effective soil conservation planning and management, in conjunction with remote sensing data and GIS skill for surface characteristics. To do this, two basins are selected: Andong and Imha basin. Geographically one is in the vicinity of the other but turbidity in the main reservoir of each basin is quite different. it is important to clarify general behavior of soil erosion driven by rainfall event for both basins for further understanding and effective soil conservation planning and management. Also, Both basins are divided into several sub-basins and the severity of soil loss is intensively investigated to identify areas with high erosion potential for each sub-basin so that the efficiency of soil conservation program may increase. Especially, this study analyzed soil erodibility factor(K), topographic factor(LS), cover management factor(C) and soil erosion; 3 sub-basins for Andong basin (up-, mid-, downstream) and 6 sub-basins for Imha basin (up-, mid-, and downstream for two tributaries) because Imha basin consists of two tributaries (Banyeon and Yongjeon river). The approach suggested herein will provide a guideline for choosing prior areas to be examined and managed for soil conservation planning.

• Journal of the Korean GEO-environmental Society
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• v.15 no.4
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• pp.13-27
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• 2014

Catchments soil erosion, one of the most serious problems in the mountainous environment of the world, consists of a complex phenomenon involving the detachment of individual soil particles from the soil mass and their transport, storage and overland flow of rainfall, and infiltration. Sediment size distribution during erosion processes appear to depend on many factors such as rainfall characteristics, vegetation cover, hydraulic flow, soil properties and slope. This study involved laboratory flume experiments carried out under simulated rainfall in a 3.0 m long ${\times}$ 0.8 m wide ${\times}$ 0.7 m deep flume, set at $17^{\circ}$ slope. Five experimental cases, consisting of twelve experiments using three different sediments with two different rainfall conditions, are reported. The experiments consisted of detailed observations of particle size distribution of the out-flow sediment. Sediment water mixture out-flow hydrograph and sediment mass out-flow rate over time, moisture profiles at different points within the soil domain, and seepage outflow were also reported. Moisture profiles, seepage outflow, and movement of overland flow were clearly found to be controlled by water retention function and hydraulic function of the soil. The difference of grain size distribution of original soil bed and the out-flow sediment was found to be insignificant in the cases of uniform sediment used experiments. However, in the cases of non-uniform sediment used experiments the outflow sediment was found to be coarser than the original soil domain. The results indicated that the sediment transport mechanism is the combination of particle segregation, suspension/saltation and rolling along the travel distance.

• Journal of Korean Society for Geospatial Information Science
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• v.15 no.2 s.40
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• pp.25-31
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• 2007

The recent frequent heavy rainfall has caused an increased in soil erosion and the soil drain which drained soil has caused decreased in channel radius and environmental problems by turbidity. In this study, the optimum size of the sediment basin was tested with soil erosion estimated from the Universal Soil Loss Equation (USLE) in the basin using by GIS data. The results show that the estimated soil erosion and the designed soil deposit are $72.1\;m^3$ and $85.0\;m^3$ respectively and the size of sediment basin is proper. In this study the water depth was calculated from the Hec-Ras model to test the stability of the bank and to prove submersion of the inside fields from stream overflow.

• Geomechanics and Engineering
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• v.25 no.1
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• pp.49-58
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• 2021

The resistance of soil to the tractive force of flowing water is one of the essential parameters for the stability of the soil when directly exposed to the movement of water such as in rivers and ocean beds. Biopolymers, which are new to sustainable geotechnical engineering practices, are known to enhance the mechanical properties of soil. This study addresses the surface erosion resistance of river-sand treated with several biopolymers that originated from micro-organisms, plants, and dairy products. We used a state-of-the-art erosion function apparatus with P-wave reflection monitoring. Experimental results have shown that biopolymers significantly improve the erosion resistance of soil surfaces. Specifically, the critical shear stress (i.e., the minimum shear stress needed to detach individual soil grains) of biopolymer-treated soils increased by 2 to 500 times. The erodibility coefficient (i.e., the rate of increase in erodibility as the shear stress increases) decreased following biopolymer treatment from 1 × 10-2 to 1 × 10-6 times compared to that of untreated river-sands. The scour prediction calculated using the SRICOS-EFA program has shown that a height of 14 m of an untreated surface is eroded during the ten years flow of the Nakdong River, while biopolymer treatment reduced this height to less than 2.5 m. The result of this study has demonstrated the possibility of cross-linked biopolymers for river-bed stabilization agents.

• Journal of Korea Water Resources Association
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• v.38 no.1
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• pp.59-71
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• 2005

Mountain watersheds are a lot of problems about soil erosion because of frequent wildfire occurrence. Runoff and soil erosion caused by the rain on a hillslope after wildfire are dependent on cover factor. And these has been a decrease by the cover factor recovery following time passage. The present paper defines the dynamic sensitivity of runoff and soil erosion that is the rate of runoff volume and soil erosion weight to rainfall energy and analyzes characteristics of the sensitivity for variation of cover factor, In according to the correlation analysis between other parameters and sensitivities, the sensitivity is the most dependent on the cover factor and the relation is exponential. The sensitivities after wildfire have suitable relation with treatment method for the mitigation of burnt forest and wildfire intensity. It was confirmed that the variation of soil erosion sensitivities come upon the range of stability in 5 years after wildfire.

• Proceedings of the Korean Geotechical Society Conference
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• 2004.03b
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• pp.533-537
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• 2004

The erodibility of soil is an important factor to scour, especially in fine-grained soils. In this study, the erosion characteristics of kaolinite are quantified through the scour rate tests using the Erosion Function Apparatus called EFA. The basic soil property tests are also performed. The kaolinite samples are prepared by mixing with distilled water and formed to the designed maximum consolidation pressure of 60, 110, 160, 240, 360kPa, respectively. The results of the scour rate tests are presented in a format of a plot showing the relationship between erosion rates and shear stresses. Erosion properties of kaolinite showed a striking contrast according to the maximum consolidation pressure, and a correlation was established between the erosion properties of kaolinite and the soil properties; water content, undrained shear strength, dry density.