• Journal of The Korean Society of Agricultural Engineers
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• v.46 no.7
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• pp.3-12
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• 2004

The need to predict the rate of soil erosion, both under existing conditions and those expected to occur following soil conservation practice, has been led to the development of various models. In this study Morgan model especially developed for field-sized areas on hill slopes was applied to assess the rate of soil erosion using RS/GIS environment in the Dukchun river basin, one of two tributaries flowing into Jinyang lake. In order to run the model, land cover mapping was made by the supervised classification method with Landsat TM satellite image data, the digital soil map was generated from scanning and screen digitizing from the hard copy of soil maps, digital elevation map (DEM) in order to generate the slope map was made by the digital map (DM) produced by National Geographic Information Institute (NGII). Almost all model parameters were generated to the multiple raster data layers, and the map calculation was made by the raster based GIS software, IL WIS which was developed by ITC, the Netherlands. Model results show that the annual soil loss rates are 5.2, 18.4, 30.3, 58.2 and 60.2 ton/ha/year in forest, paddy fields, built-up area, bare soil, and upland fields respectively. The estimated rates seemed to be high under the normal climatic conditions because of exaggerated land slopes due to DEM generation using 100 m contour interval. However, the results were worthwhile to estimate soil loss in hilly areas and the more precise result could be expected when the more accurate slope data is available.

• Journal of the Korean Association of Geographic Information Studies
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• v.3 no.4
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• pp.63-72
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• 2000

The objective of this study was to identify the applicability of AGNPS(Agricultural Nonpoint Source Pollution) model using RS data; Landsat TM merged by KOMPSAT EOC and GIS data. AGNPS model which is well-known distributed nonpoint source pollution model was used as the assessment tool. This model has the capability to adjust the level of pollutant load from farmstead and the fertilization level of upland field. A small agricultural watershed($4.12km^2$) which has 20 livestock farmhouses located in Gosan-myun, Ansung-gun was selected. AGNPS data were prepared by using Arc/Info, GRASS, ER-Mapper and Idrisi. Four storm events in 1999 were used for runoff calibration, and 2 storm events which were measured in hourly-base at 4 locations along the stream were used for water quality(TN, TP) calibration.

• Journal of The Geomorphological Association of Korea
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• v.17 no.1
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• pp.1-14
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• 2010

This paper deals with the classification and distribution of geomorphic surfaces and analysis on effects of geomorphic processes on the landforms in the inaccessable DMZ (Demilitarized Zone) to Wonsan Bay of East Sea coast of Chugaryeong Rift Valley, Central Korea. DEM (Digital Elevation Model) and Landsat images are used for the above anlaysis. The geomorphic surfaces are classified by TPI (Topographical Position Index) for the analysis of the convexity and concavity calculated using topographical elements such as elevation, steepness, and relief. In the Chugayreong Valley, 10 geomorphic surfaces are classified as steep valley, shallow valley, upland drainage, U-shaped valley, plain, open slope, upper slope, local ridge, midslope ridge, and high ridge. Zonal Statistics presents average characteristics of geomorphological processes of surfaces by the relationships between bedrock and relief, surface and relief, and between surface and NDVI. So, these analysis can help to understand geomorphological process such as dissection of lava plateau and watershed divide evolution.

• Korean Journal of Soil Science and Fertilizer
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• v.43 no.6
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• pp.828-836
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• 2010

This study was conducted to evaluate soil erosion risk with a standard unit watershed in the upper Han river basin using the spatial soil erosion map according to the change of landuse. The study area is 14,577 $km^2$, which consists of 10 subbasins, 107 standard unit watersheds. Total annual soil loss and soil loss per area estimated were $895{\times}10^4\;Mg\;yr^{-1}$ and 6.1 Mg $ha^{-1}\;yr^{-1}$, respectively. A result of analysis with a subbasin as a unit showed that annual soil losses and soil loss per area in Namhan river basins was more than in Bukhan river ones. Predicted annual soil loss according to the landuse ranked as Forest & Grassland > Upland ${\gg}$ Urban & Fallow area > Paddy field > Orchard. Upland area covered 6.2% of the study area, but the contribution of total annul soil loss was 40.6% and that of Forest & Grassland was 44.2%. As a evaluation of soil erosion risk using the spatial soil erosion map, we could precisely conformed the potential hazardous region of soil erosion in each unit watersheds. The ratio of regions, graded as higher "Moderate" for annual soil loss, were respectively 8.7%, 7.9% and 7.8% in 1001, 1002 and 1003 subbasins in Namhan river basin. Most landuse of these area was upland, and these area is necessary to establish soil conservation practices to reduce soil erosion based on the field observation.

• Journal of Wetlands Research
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• v.13 no.3
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• pp.535-545
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• 2011

This study was carried out to suggest the baseline data necessary for vegetation restoration by naturalness assessment of riverine wetland within stream corridor. We selected stream reach both of near nature and urbanized by Nonsan stream and Hongchun river as experimental site. Composition of vegetation community and land use pattern between two sites indicated considerable difference, which imply for many different watershed property and process disturbed each other at river ecosystem. Naturalness of the sampled reaches showed that near nature is in better condition for riverine wetland than urbanized of all two sites. However, the prevalence index of Hongchun river within its natural state was lower than that of Nonsan stream, because the index included some vegetation communities occurred at upland fringe and bank slope. In conclusion assessment system using prevalence index would be considered an effective method for evaluating of natural states of riverine wetland.

• Proceedings of the Korean Society of Environment and Ecology Conference
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• 2003.10a
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• pp.105-126
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• 2003

In Korea most of annual rainfall is concentrated in several episodic heavy rains during the season of summer monsoon and typhoon. Because of uneven rainfall distribution many dams have been constructed in order to secure water supply in dry seasons. The Han River system has the most dams among Korean rivers, and the river is a series of dams now. Reservoirs need different strategy of water quality control from river water. Autochthonous organic matter and phosphorus should be the major target to be controlled in lakes. In this Paper some problems are discussed that makes efforts of water quality improvement ineffective in lakes of Korea, even after the substantial investment to wastewater treatment facilities.1) Phosphorus is the key factor controlling eutrophication of lakes and the reduction ofphosphors should be the major target of water treatment. However, water quality management strategy in Korea is still stream-oriented, and focused on BOD removal from sewage. Phosphorus removal efficiency remains as low as 10-30%, because biological treatment is adopted for both secondary treatment and advanced treatment. The standard for TP concentration of the sewage treatment plant effluent is 6 mgP/l in most of regions, and 2 mg/l in enforced region near metropolitan water intake point. TP in the effluents of sewage treatment plants are usually 1-2 mg/1, and most of plants meet the effluent regulation without a further phosphorus removal process. The generous TP standard for effluents discourages further efforts to improve phosphorus removal efficiency of sewage treatment. Considering that TP standard for the effluent is below 0.1 mg/l in some countries, it should be amended to below 0.1 mg/l in Korea, especially in the watershed of large lakes.2) Urban runoff and combined sewer overflow are not treated, even though their total loading into lakes can be comparable to municipal sewage discharges on dry days. Chemical coagulation and rapid settling might be the solution to urban runoff in regard of intermittent operation on only rainy days.3) Aggregated precipitation in Korea that is concentrated on several episodic heavyrains per year causes a large amount of nonpoint source pollution loading into lakes. It makes the treatment of nonpoint source discharge by methods of other countries of even rain pattern, such as retention pond or artificial wetland, impractical in Korea.4) The application rate of fertilizers in Korea is ten times as high as the average ofOECD countries. The total manure discharge from animal farming is thought to be over the capacity of soil treatment in Korea. Even though large portion of manure is composted for organic fertilizer, a lot of nutrients and organic matter emanates from organic compost. The reduction of application rate and discharge rate of phosphorus from agricultural fields should be encouraged by incentives and regulations.5) There is a lot of vegetable fields with high slopes in the upstream region of the HanRiver. Soil erosion is severe due to high slopes, and fertilizer is discharged in the form of adsorbed phosphorus on clay surface. The reduction of soil erosion in the upland area should be the major preventive policy for eutrophication. Uplands of high slope must be recovered to forest, and eroded gullies should be reformed into grass-buffered natural streams which are wider and resistant to bank erosion.

• Economic and Environmental Geology
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• v.38 no.3 s.172
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• pp.207-219
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• 2005

The physical and chemical characteristics of soils in a small watershed were investigated and the effect of geology and land use on soil quality were examined by using multivariate statistical methods, principal components analysis and discriminant analysis. The soil developed from andesite had finer texture and higher contents of water extractable inorganic components, clay, and mafic minerals than the soil developed from granite. It is considered that the accumulation of salts in the farmland soils indicated by electrical conductivity, contents of cations and anions and pH was caused by fertilizer input during cultivation. The low contents of organic matter in the farmland soils was due to the enhanced oxidation of organic matter by tillage and by the harvest of crops. The contents of inorganic components are increased as following order: upland > orchard > paddy field > forest. The high contents of water soluble $SO_4\;^{2-}$ of paddy soils is due to the oxidation of sulfides mineral formed during the flooding period during the air-dry and extraction. The results of principal components analysis show the difference of soil quality was controlled by geology and land use. PCI indicate the input of fertilizer, mineral weathering and ion exchange reaction by application of nitrogenous fertilizers. The results of two discriminant analyses using water extractable inorganic components and their ratios by land use were also clearly classified by discriminant function 1 and 2. In discriminant analysis by components, discriminant function 1 indicated the effect of fertilizer application and increased as following order: upland > orchard > paddy field > forest soil. The investigated and predicted data for land use from discriminant analysis showed similar results. The discriminant analysis can be used as a useful method certifying the change of land use.

• Korean Journal of Soil Science and Fertilizer
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• v.33 no.4
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• pp.234-241
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• 2000

Organic farming (OF) is regarded as alternative farming types against general farming system for sustainable agriculture, recently. However, there is little information on effects of OF on soil properties and watershed condition. In order to determine the effects of OF on soil properties, 36, 10 and 8 sites of organic farming (OF) fields of plastic film houses, paddy and orchard were selected in the national scale, respectively, to evaluate their chemical properties and phosphorus distributing characteristics. The average organic matter (OM) contents in organic farming fields were with $44g\;kg^{-1}$ in plastic film houses, $26g\;kg^{-1}$ in paddies and $39g\;kg^{-1}$ in orchard soils higher than the average OM contents in conventional farming (CF) soils. Available phosphates were accumulated to 986 in plastic film house soils and $754mg\;kg^{-1}$ in orchard soils, respectively, over the optimum range. Furthermore, total P (T-P) reached to $2.973mg\;kg^{-1}$ in plastic film houses and $2303mg\;kg^{-1}$ in orchards in OF soils. It could be attained by applying repeatedly low N/P ratio of manure-based compost. In two types of soils inorganic P was dominant with the ratio of 62~80% of T-P, and then residual and organic Ps followed. However. residual-P was dominant in paddy soils with the rate of 50% of T-P. Fractionation of soil extractable P showed that Ca-P was dominant with about $1,330mg\;kg^{-1}$ in upland soils in OF fields, which is affected by high soil pH of over 6.0. However. Fe-P of extractable P was dominant in paddy soils. Water-soluble P was very high with 65 and $26mg\;kg^{-1}$ in plastic film house and orchard soils in OF. From this results. OF regarded as an environment-friendly farming system may cause serious soil deterioration by accumulated phosphorus and may also cause water pollution.