• Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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• v.19 no.1
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• pp.27-37
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• 2001

Soil erosion by outflow of water or rainfall has caused many environmental problems as declining agricultural productivity, damaging pasture and preventing flow of water. As the interest in environment is increasing lately, soil erosion is considered as a serious problem, whereas the systematic regulation and analysis for that have not established yet. This research shows the method of extracting factor entered model which expects soil erosion by GSIS. There are several erosion model such as ANSWER, WEPP, RUSLE. The research used RUSLE erosion model which could expect general soil erosion connected easily with GSIS data. RUSLE's input factors are composed of rainfall runoff factor(R). soil erodibility factor(K), slope length factor(L), slope steepness factor(S), cover management factor(C) and support practice factor(P). The general equation used to extract L, S factor on the RUSLE to be oriented for agricultural area has some limitation to apply whole watershed. So, on this study we used a revised empirical equation applicable to the watershed by grid on the GSIS. Also, we analyzed RUSLE factors by watershed being analyzed with watershed extraction algorithm. Then we could calculate the minimum, maximum. mean and standard deviation of RUSLE factors by watershed.

• 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.

• Korean Chemical Engineering Research
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• v.43 no.3
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• pp.412-418
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• 2005

The tube thickness map of water wall has been measured in a commercial circulating fluidized bed combustor (200 ton steam/hr, $4.97{\times}9.90{\times}28.98m$ height) with ultrasonic method and tube erosion has been discussed. Severe tube erosion took place in the splash region on all waterwalls including wingwalls. Erosion on the lower part of front and rear walls, close to both side walls, was more serious than other places. Erosion of some tubes around the gas exit was found to be noticible. Tube erosion increased on the wingwall as the position of the tube become closer to the center of the combustor crosssection.

• Journal of Korean Society of Rural Planning
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• v.11 no.2 s.27
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• pp.51-57
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• 2005

It has been well known that soil erosion and sediments from alpine agricultural fields are causing severe water quality and turbidity problems in receiving waters. Also these result in the loss of money because farmers have to buy top soils to provide enough root zone in the following year. Thus, there have been needs to reduce soil erosion and sediment discharge into the stream networks. To accomplish this end, an effective erosion control plans should be developed based on scientific research, not by rule of thumb. The Universal Soil Loss Equation (USLE) has been widely used to estimate the soil erosion in many countries over the years. In this study, the USLE was used to estimate soil erosion potential under different cropping scenarios in HongCheon County, Kangwon. The soil erosion potential for continuous corn cropping was the highest compared with those from continuous potato find average cropping scenarios. This indicates the soil erosion plans need to be established considering cropping system in the field. The Unit Stream Power Erosion-Deposition (USPED) was applied for HongCheon County to estimate soil erosion and deposition areas. The USPED estimated results can be used to complement USLE results in developing effective erosion control plans.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.17-17
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• 2011

As a method of countermeasure to bed degradation and armoring phenomena of bed material in the downstream area of dam reservoirs, sediment augmentation (replenished sediment) has been carried out in many Japanese rivers. In general, bed of the replenished sediment site is composed of rocks, because the site is located in the downstream area of the dams and sediment supply is very small. Bed deformation process has been researched by many researchers. As a method of countermeasure to bed degradation and armoring phenomena of bed material in the downstream area of dam reservoirs, sediment augmentation (replenished sediment) has been carried out in many Japanese rivers. In general, bed of the replenished sediment site is composed of rocks, because the site is located in the downstream area of the dams and sediment supply is very small. Bed deformation process has been researched by many researchers. However, most of them can treat movable bed only and cannot be applied to the bed deformation process of sediment on rocks. If the friction angle between the sediment and the bed surface is assumed to be the same as the friction angle between the sediment and the sediment, sediment transport rate must be smaller without sediment deposition layer on the rocks. As a result, the reproduced bed geometry is affected very well. In this study, non-equilibrium transport process of non-cohesive sediment on rigid bed is introduced into the horizontal two dimensional bed deformation model and the model is applied to the erosion process of replenished sediment on rock in the Nakagawa, Japan. Here, the Japanese largest scale sediment augmentation has been performed in the Nakagawa. The results show that the amounts of the eroded sediment and the remained sediment reproduced by the developed numerical model are $56300m^3$ and $26800m^3$, respectively. On the other hand, the amounts of the eroded sediment and the remained sediment measured in the field after the floods are $56600m^3$ and $26500m^3$, respectively. The difference between the model and field data is very small. Furthermore, the bed geometry of the replenished sediment after the floods reproduced by the developed model has a good agreement with the measured bed geometry after the floods. These results indicate that the developed model is able to simulate the erosion process of replenished sediment on rocks very well. Furthermore, the erosion speed of the replenished sediment during the decreasing process of the water discharge is faster than that during the increasing process of the water discharge. The replenished sediment is eroded well, when the top of the replenished sediment is covered by the water. In general, water surface level is kept to be high during the decreasing process of the discharge during floods, because water surface level at the downstream end is high. Hence, it is considered that the high water surface level during the decreasing process of the water discharge affects on the fast erosion of the replenished sediment.

• Asian Journal of Turfgrass Science
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• v.10 no.1
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• pp.21-29
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• 1996

The mathematical expression in the forest and grassland soils to express the general concepts involved in such terms "a soil erosion and soil renewal. " The net addition rate in the forest and grassland soils are represented by an equation of $(S_{rb}-S_{ra})-(S_{eb}-S_{ea})={\int}_a^bR(m, cl, re, b, t )dt-{\int}E(w, r, cl, re, ch, b, t)dt{\gtreqqless}0$ where $S_r$, is renewal soil, $S_e$ is soil erosion, and variable factors are m =parent material of soil, cl=climate, re=relief or topography, ch=soil characteristics, r=rain or water, w=wind, b=biota, and t = time.

• 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 on Water Environment
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• v.30 no.6
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• pp.638-646
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• 2014

Soil erosion from agricultural fields leads to various environmental problems weakening the capabilities of flood control and ecosystem in water bodies. Regarding these problems, Ministry of Environment of South-Korea prepared various structural and non-structural best management practices (BMPs) to control soil erosion. However, a lot of efforts are required to monitor and develop BMPs. Thus, modeling techniques have been developed and utilized for these issues. This study estimated the effectiveness of BMPs which are a vegetation mat with infiltration roll and Roll type vegetation channel using Soil and Water Assessment Tool (SWAT) model through the adjustment of the conservation practice factors, P factors, for Universal Soil Loss Equation which were calculated by monitoring data collected at the segment plots. Each BMP was applied to the areas with slopes ranged from 7% to 13% in the Haeanmyeon watershed. As a result of simulation, the vegetation mat with infiltration roll and Roll type vegetation channel showed 55% and 59% efficiency of soil erosion reduction, respectively. Also, Vegetation mat with infiltration roll and Roll type vegetation channel showed each 11.2% and 11.8% efficiency in reduction of sediment discharge. These roll type vegetation channel showed greater efficiency of soil erosion reduction and sediment discharge. Based on these results, if roll type vegetation channel is widely used in agricultural fields, reduction of soil erosion and sediment discharge of greater efficiency would be expected.

• Journal of Korea Water Resources Association
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• v.43 no.11
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• pp.995-1009
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• 2010

Accelerated soil erosion due to extreme climate change, such as increased rainfall intensity, and human-induced environmental changes, is a widely recognized problem. Existing soil erosion models are generally based on the gross erosion concept to compute annual upland soil loss in tons per acre per year. However, such models are not suitable for event-based simulations of erosion and deposition in time and space. Recent advances in computer geographic information system (GIS) technologies have allowed hydrologists to develop physically based models, and the trend in erosion prediction is towards process-based models, instead of conceptually lumped models. This study aims to propose an effective and robust distributed rainfall-sediment yield-runoff model consisting of basic element modules: a rainfall-runoff module based on the kinematic wave method for subsurface and surface flow, and a runoff-sediment yield-runoff model based on the unit stream power method. The model was tested on the Cheoncheon catchment, upstream of the Yongdam dam using hydrological data for three extreme flood events due to typhoons. The model provided acceptable simulation results with respect to both discharge and sediment discharge even though the simulated sedigraphs were underestimated, compared to observations. The spatial distribution of erosion and deposition demonstrated that eroded sediment loads were deposited in the cells along the channel network, which have a short overland flow length and a gentle local slope while the erosion rate increased as rainfall became larger. Additionally, spatially heterogeneous rainfall intensity, dependant on Thiessen polygons, led to spatially-distinct erosion and deposition patterns.

• Journal of Ocean Engineering and Technology
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• v.33 no.6
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• pp.526-534
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• 2019

The average coastline and the erosion control line introduced as the management coastline, and the average shoreline (MSL) was established from the observed coastline. Also, the median grain size and the wave height of 30-years return period were applied. The erosion control line (ECL) was established through the model, HaeSaBeeN. These two lines set the coastline for evaluation. Based on the observed monitoring data along the coastline, the 1-day variation according to the normal distribution was used to estimate the regional variation, and the width of the erosion was calculated by applying the median grain size (D₅₀) and the wave height of 30-years return period through the high-wave coastal erosion width model, i.e., HaeSaBeeN.