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DESIGN FREQUENCY DECISION FOR HYDRAULIC STRUCTURES DUE TO HEAVY STORM
Choi, Ye-Hwan,Choi, Joong-Dae 江原大學校 附設 環境硏究所 2000 環境硏究 Vol.17 No.-
In considering the causes for the damage of winds and floods in Korea. there are two types. that is one of two reasons is known the shape of geomorphology and weather conditionas which are natural factors, the other is social factors that are due to increasing population, industrialization, urbanization and development of rivers. But in recently years according to destroy the global environment by human activity, weather conditions may be changed from expecting conditions to extraordinarty patterns such as Elni? and Lanina. As the result, there are much precipitation beyond the expecting values of annual recording data. When a heavy storm rainfall falls down much amount at a given watersheds area during short interval time, it may happen that inundation of rivers. destruction of banks and ruins of reservoirs. As the results, the damages bring a submersion of farm lands. farm lands of washing away by the floods and burying farm lands by floods. After the analyses of rainfall data including recent data of six points in Han River watershed such as Chunchon, Gapyeong and others. we must restablish the safety factors of river banks and probability exceedence rainfall with each return period for hydraulic structures such as river banks, reservoirs. inflowing weirs etc. in order to overwhelm the risk of agricultural hydraulic structures. The analysis metod that was chosen is the Extreme Type I and it is gotten the probability rainfalls of during 31 years except missing data.
THE ANALYSIS OF OBSERVED RAINFALL AND HEAVY STORM FOR THE HYDRAULIC STRUCTURE DESIGN
CHOI, Ye-Hwan,CHOI, Joong Dae 江原大學校 附設 環境硏究所 1999 環境硏究 Vol.16 No.-
The heavy storm which was happened in Chulwon and Yeonchon of middle north part of Korea on July 26th to 28th .1996. The former analysis of heavy rainfall with recorded data of return period are compared with the neighborhood area by Type I External distribution. As the results, it is reconsidered that the criterion design of hydraulic structures and river banks will be used in future in order to decrease the flood damages.
( Choi Ye Hwan ),( Saied Mostaghimi ) 한국농공학회 1990 韓國農工學會誌 : 전원과 자원 Vol.32 No.-
Over the last several decades, crop production in the United States increased largely due to the extensive use of animal waste and fertilizers as plant nutrient supplements, and pesticides for crops pests and weed control. Without the application of animal waste best management, the use of animal waste can result in nonpoint source pollution from agricultural land area. In order to increase nutrient levels and decrease contamination from agricultural lands, nonpoint source pollution is responsible for water quality degradation. Nonpoint source pollutants such as animal waste, ferilizers, and pesticides are transported primarily through runoff from agricultural areas. Nutrients, primarily nitrogen and phosphorus, can be a major water quality problem because they cause eutrophic algae growth. In 1985, it was presented that Watershed/Water Quality Monitoring for Evaluation BMP Effectiveness was implemented for Nomini Creek Watershed, located in Westmoreland County, Virginia. The watershed is predominantly agricultural and has an aerial extent of 1505 ha of land, with 43% under cropland, 54% under woodland, and 3% as homestead and roads. Rainfall data was collected at the watershed from raingages located at sites PNI through PN 7. Streams at stations QN I and QN2 were being measured with V-notch weirs. Water levels at the stream was measured using an FW-l Belfort (Friez FWl). The water quality monitoring system was designed to provide comprehensive assessment of the quality of storm runoff and baseflow as influenced by changes in landuse, agronomic, and cultural practices ill the watershed. As this study was concerned with the Nomini Creek Watershed, the separation of storm runoff and baseflow measured at QNI and QN2 was given by the master depletion curve method, and the loadings of baseflow and storm runoff for TN (Total Nitrogen) and TP (Total Phosphorus) were analyzed from 1987 through 1989. The results were studied for the best management practices to reduce contamination and loss of nutrients, (e.g., total nitrogen and total phosphorus) by nonpoint source pollution from agricultural lands.
CHANGE OF STREAM WATER QUALITY OF TWO SMALL AGRICULTURAL WATERSHEDS
Choi, Ye-Hwan,Choi, Joong-Dae 江原大學校 附設 環境硏究所 1997 環境硏究 Vol.14 No.-
Two traditional agricultural watershed water qualities and watershed characteristics were monitored between March and December, 1995. The soil texture of the watersheds was a sandy loam. About 52% of the households and animal feedlots did have drainage ditch and existing drainage ditches were observed dry during most of the year except transplanting and monsoon season. Because of the drainage system, pollutant inflow into the streams through surface flow were limited. Measured total coliform counts showed the differences conditions. BOD and SS concentrations were very low and showed no changes throughout the monitoring period in the streams. NO₃-N and TN concentrations showed a cleat changes with time. Both concentrations were low between January and May but high between June and December. It was thought that the difference was caused by groundwater discharges from the fields. It was concluded that stream water quality of the studied watersheds were largely affected by agricultural activities and groundwater flow.
( Choi Joong Dae ),( Shirmohammadi Adel ),( Ryu Neung Hwan ),( Choi Ye Hwan ) 한국농공학회 1992 韓國農工學會誌 : 전원과 자원 Vol.34 No.-
Increasing national concern on nonpoint source pollution of surface and ground water Systems has led researchers and policy makers to develop certain agricultural Best Management Practices. As an initial step of broad study program above mentioned, this study reflected the effects of different tillage practice on bulk density and degree of saturation on two regional soils, namely Tama silt loam and Catlin silt loam. Results may help to clarify some of the conflicting findings on the impact of tillage systems on these parameters and it may also explain some of the reasons for specific role that different tillage systems play regarding nonpoint source pollution from agricultural fields.