• Magazine of the Korean Society of Agricultural Engineers
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• v.45 no.7
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• pp.49-56
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• 2003

Nonpoint source pollutant loading from watershed may cause a problem to the water quality of the reservoir and stream. The characteristics of stream flow and water quality were monitored to investigate the runoff loading of the Namdae-cheon watershed from May in 1999 to October in 2003. Stage-discharge rating curve at the stream gauging site was established, and annual stream runoff of the study watershed was estimated as 499.4∼1,330.8mm during four years. The concentrations of total-nitrogen and total-phosphorus of stream water quality ranged from 0.76 to 6.95mg/L and from 0.0010 to 0.2276 mg/L, respectively, where T-N was generally higher than the water quality standard 1.0 mg/L for agricultural water use. The loads by unit generation of pollutant mass with respect to population, livestock, land use in this watershed were calculated. The runoff pollutant loadings by concentrations of total-N and total-P were estimated during study period, where the annual runoff loading of total-P was much less than the load by pollutant mass unit generation. The relations between stream discharge and water quality were analysed, and there was a high correlation for total-N but low for total-P. These results will be used to develop the monitoring techniques and water quality management system of agricultural watershed.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.647-650
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• 2003

To provide the basic information for the water quality improvement of the Geumkang River Basin, the water qualities of the Namdae-cheon watershed were investigated from May in 1999 to September in 2003.

• Korean Journal of Environmental Agriculture
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• v.19 no.1
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• pp.26-31
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• 2000

This study was carried out to investigate the changes of water quality, the pollutant loading by population, livestock, and land use at the Namdae-cheon in Keum river districts. Water samples were taken at the four sites of watershed, the nutrients of which were analyzed periodically from July, 1995 to April, 1998. Content of nutrients in water samples ranged from 1.8 to 5.8 mg/L for total nitrogen, from 0.01 to 0.08 mg/L for total phosphorus and from 0 to 0.007 mg/L for ortho-phosphate respectively. Nitrogen loading by pollutant unit was investigated 550.4 ton/yr as 358.1 ton/yr by livestock, 129.3 ton/yr by land use and 63.0 ton/yr by population. Phosphorus loading by pollutant unit was investigated 79.1 ton/yr as 60.6 ton/yr by livestock, 5.2 ton/yr by land use and 13.3 ton/yr by population. The loading of measured pollutant was investigated 452.5 ton/yr of nitrogen and 5.4 ton/yr of phosphorus in Namdae-cheon watershed.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2003.10a
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• pp.75-78
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• 2003

This study is to present a method of land cover change detection by the typhoon RUSA (August 1 - September 4, 2002) using Landsat 7 ETM+ images. For the Namdae-cheon watershed in Gangreung, two images of Sept. 29, 2000 and Nov. 22, 2002 were prepared. To identify the damaged areas, firstly, the NDVI (Normalized Difference Vegetation Index) of each image was computed, secondly, the NDVI values were reclassified as two categories that the negative index values including zero are the one and the positive index values are the other, thirdly the reclassified image before typhoon is subtracted from the reclassified image after typhoon to get DNDVI (Differential NDVI). From the DNDVI image, the flooded and damaged areas could be extracted.

• Journal of Korea Water Resources Association
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• v.38 no.5 s.154
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• pp.391-399
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• 2005

The purpose of this study is to evaluate hydrological impact by the land cover change of typhoon damage. For the typhoon RUSA (rainfall 1,402 mm) occurred in 2002 (August $31\;{\sim}$ September 1), satellite images of Landsat 7 ETM+ of September 29, 2000 and Landsat 5 TM of September 11, 2002 were selected, and each land cover was classified for Namdae-cheon watershed $192.7km^2$ located in the middle-eastern part of Korea Peninsula. SCS unit hydrograph for watershed runoff and Muskingum for streamflow routing of WMS HEC-1 was adopted. 30m resolution DEM & hydrological soil group using 1:50,000 soil map were prepared. The model was calibrated using three available data of storm events of 1985 to 1988 based on 1985 land cover condition. To predict the streamflow change by damaged land cover condition, rainfall of 50 years to 500 years frequency were generated using 2nd quantile of Huff method. The damaged land cover condition treated as bare soil surface increased streamflow of $50.1\;m^3/sec$ for 50 years rainfall frequency and $67.6\;m^3/sec$ for 500 years rainfall frequency based on AMC-I condition. There may be some speedy treatment by the government for the next coming typhoon damage.

• Journal of the Korean Geographical Society
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• v.39 no.6 s.105
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• pp.833-844
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• 2004

In Chugaryeong rift valley, lava plateau formation by the fissure eruption had vanished original landforms and effected on drainage derangement and revision. 4 rivers including Namdae-cheon, Bukhan-gang, Imjin-gang and Hantan-gang watersheds have shared Cheolwon-Pyeonggang lava plateau, that is, ownerless watershed. Main agency of the dividing process are central-eruption volcanic peaks such as Orisan(453m) and 680 Peak. Especially, Orisan has played the role of divide point for 4 watersheds. In the lower-relief plateau zone, complex drainage system have caused continually river capture between neighboring watersheds. In more elevated range slope, river capture have proceeded to headward erosion. Hydrogeomorphologically, lava-filled valley has initiated decrease of the original size of flood plain, maybe, causing higher capability of inundation by heavy rains, and then more active dissection of lava plateau layer.