• International conference on construction engineering and project management
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• 2009.05a
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• pp.285-291
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• 2009

Water is a strategic resource for Singapore due to its small land mass and more than half of the mainland serves as catchment for raw water, including construction sites. Construction site typically involves earthworks and in conjunction with the frequent and intense rainstorm in Singapore, produce runoff of high turbidity due to suspended sediments. The resulting high concentration of suspended sediment in construction site runoff very often leads to aesthetically unpleasant reservoirs and potentially increases the treatment cost of raw water. To mitigate this, the local standard requires the discharged concentration of total suspended solids of construction runoff leaving a construction site to be less than 50mg/l which is a very high standard. This paper will present, examine and discuss particular issues and practices of Singapore's construction industry in meeting this requirement. The focus will be on two areas: Government lead initiatives and industry practices. How the government agencies worked together with the industry professionals to develop a system to ensure meeting of the standard is discussed. In addition, the types of industry practices, including various Best Management Practice to reduce erosion in construction sites and implement effective sedimentation on construction sites are examined.

• Journal of Korean Society on Water Environment
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• v.28 no.3
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• pp.375-383
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• 2012

Soil erosion has been emphasized as serious environmental problem affecting water quality in the receiving waterbodies. Recently, Best Management Practices (BMPs) have been applied at a field to reduce soil erosion and its effectiveness in soil erosion reduction has been monitored with various methods. Although monitoring at fields/watershed outlets would be accurate way for these ends, it is not possible at some fields/watersheds due to various limitations in direct monitoring. Thus modeling has been suggested as an alternative way to evaluate effects of the BMPs. Most models, which have been used in evaluating hydrology and water quality at a watershed, could not reflect rainfall intensity in runoff generation and soil erosion processes. In addition, source codes of these models are not always public for modification/enhancement. Thus, runoff-sediment evaluation system using hourly rainfall data and vegetated filter strip (VFS) evaluation module at field level were developed using open source MapWindow GIS component in this study. This evaluation system was applied to Bangdongri, Chuncheonsi to evaluate its prediction ability and VFS module in this study. The NSE and $R^2$ values for runoff estimation were 0.86 and 0.91, respectively, and measured and simulated sediment yield were 15.2 kg and 16.5 kg indicating this system, developed in this study, can be used to simulate runoff and sediment yield with acceptable accuracies. Nine VFS scenarios were evaluated for effectiveness of soil erosion reduction. Reduction efficiency of the VFS was high when sediment inflow was small. As shown in this study, this evaluation system can be used for evaluation BMPs with local rainfall intensity and variations considered with ease-of-use GIS interface.

• Spatial Information Research
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• v.17 no.4
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• pp.431-443
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• 2009

Recently, turbidity problem is one of the hot issues in dam and reservoir management works. Main reason to bring about high density turbid water is sediment yield by rainfall intensity energy. Because existing researches didn't consider diverse types of crops, it was difficult to calculate more accurate soil erosion and sediment yield. This study was evaluated the reduction efficiency of soil erosion and sediment yield using ginseng layer extracted from IKONOS satellite image, and the area and the ratio of ginseng area represented $0.290km^2$ and 0.94%. The reduction efficiency of soil erosion considering ginseng area represented low value in 0.9% using GIS-based RUSLE model, because the area of ginseng was small compared to areas of other agricultural lands. To reflect future land use change, this study was calculated the reduction efficiency of soil erosion and sediment yield by considering many scenarios as kinds of crops of paddy, dry field, orchard, and other agricultural areas convert to the ginseng district. As result of analysis of them according to scenarios, scenario (1) in which dry field was converted to ginseng area and scenario (2) in which fully agricultural lands were converted to ginseng area showed high reduction efficiency as 31.3% and 34.8% respectively, compared to existing research which didn't consider ginseng area. Methodology suggested in this study will be very efficient tools to help reservoir management related to high density turbid water.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09a
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• pp.349-350
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• 2005

• Magazine of the Korean Society of Agricultural Engineers
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• v.44 no.7
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• pp.53-63
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• 2002

Runoff, sediments and nutrient losses were studied under different patterns of paddy field management: (1) fall and spring plowing (Plowing)i (2) fall plowing for half of plot and spring plowing (Semi-plowing); (3) no-till for fall and spring plowing (Un-plowing) during the non-cropping period in the southern Korea for two years. The runoff amount and initial abstract were significantly affected by plowing practices. Un-plowing plot showed the highest runoff amount among treatments. The concentrations of sediment from Plowing plot were much higher than those from Un-plowing plot, especially after (all plowing. Sediment losses from Plowing plot were 25% more than those from Un-plowing plot. There was significant difference in nutrient losses via runoff water and sediment according to plowing practice. Two-year average of losses of N from paddy field during non-cropping period were 9.42 kg ha$\^$-1/, 8.17kg ha$\^$-1/, and 7.76 kg ha$\^$-l/ for Un-plowing, Semi-plowing, and Plowing plot, respectively, while losses of P were 0.64 kg ha$\^$-1/, 0.58 kg ha$\^$-1/, and 0.58 kg ha$\^$-1/ for each tillage system. Losses of total-N, ammonia-N, nitrate-N, Total-P from Un-plowing plot was larger than those from Plowing and Semi-plowing plots during study period.

• Journal of Korean Society of Environmental Engineers
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• v.36 no.8
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• pp.521-527
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• 2014

The objectives of study are 1) to enhance the filed scale BMPs model of HRSM4BMP for simulation of watershed scale and 2) to evaluate the enhanced HRSM4BMP model. Thus pre-process and post-process module were developed and HRSM4BMP was linked to SWAT routing module. After enhancement of model, enhanced HRSM4BMP model was applied to Heaan watershed in Kangwon province with Vegetative filter strip (2 m) in subwatershed #14 and reduction of sediment load was evaluated by watershed scale in outlet. The results of simulation, sediment load was reduced by 4 percent during 3 years in outlet. The result of this study is expected to be used Long-term BMPs establishing plan in South Korea.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.1
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• pp.60-70
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• 2011

The sediment removal index derived from the chemical contaminants, $CI_{HC}$, is currently in use to identify and define the spatial extent of the contaminated sediments in the sea. In order to analyze the sensitivity of the ecological and human risk associated with contaminated sediment, we evaluated five hypothetical contaminated sediments, whose $CI_{HC}$ values are identical but consisted of different contaminant contents, using $TrophicTrace^{(R)}$ model dedicated to evaluate sediment risk, against the resident greenling (Hexagrammos otakii) and humans by calculating No-Observed-Adverse-Effect-Level based Toxicity Quotient (NOAEL TQ) and Lowest-Observed-Adverse-Effect-Level based Toxicity Quotient (LOAEL TQ), and cancer risks and hazard indices (HI), respectively, based on the site conceptual model and exposure assumptions of fish ingestion to human receptor populations. NOAEL and LOAEL TQ values varied as much as a factor of 2 among 5 hypothetical sediments. Chemical element specific contribution to the carcinogenic risk and HI varied also greatly in these sediments. The reason for this significant dissimilarity in ecological and human risk stems from the different risk of each contaminant to the resident fish and human receptor. When the conceptual food web model is constructed for the target biological species for a given site, the ecological and human risk analysis considering trophic transfer of contaminants will add a ecosystem based tool for the management of contaminated sediments.

• Journal of The Korean Society of Agricultural Engineers
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• v.55 no.2
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• pp.47-57
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• 2013

This study is to assess the reduction of non-point source pollution loads for rice straw mulching of upland crop cultivation at a watershed scale. For Byulmi-cheon watershed (1.21 $km^2$) located in the upstream of Gyeongan-cheon, the HSPF (Hydrological Simulation Program-Fortran) and SWAT (Soil and Water Assesment Tool), physically based distributed hydrological models were applied. Before evaluation, the model was calibrated and validated using 9 rainfall events. The Nash-Sutcliffe model efficiency (NSE) for streamflow using the HSPF was 0.62~0.76 and the determination coefficient ($R^2$) for water quality (sediment, total nitrogen T-N, and total phosphorus T-P) were 0.72, 0.62, and 0.63 respectively. The NSE for streamflow using the SWAT were 0.43~0.81 and the $R^2$ for water quality (sediment, T-N, and T-P) were 0.54, 0.87, and 0.64 respectively. From the field experiment of 16 rainfall events, the rice straw cover condition reduced surface runoff average 10.0 % compared to normal surface condition. By handling infiltration capacity (INFILT) in HSPF model, the value of 16.0 mm/hr was found to reduce about 10.0 % reduction of surface runoff. For this condition, the reduction effect of sediment, T-N, and T-P loads were 87.2, 28.5, and 85.1 % respectively. By handling soil hydraulic conductivity (SOL_K) in SWAT model, the value of 111.2 mm/hr was found to reduce about 10.0 point reduction of surface runoff. For this condition, the reduction effect of sediment, T-N, and T-P loads were 80.0, 83.2, and 78.7 % respectively. The rice straw surface covering was effective for removing surface runoff dependent loads such as sediment and T-P.

• Journal of the Korean Society for Marine Environment & Energy
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• v.8 no.3
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• pp.122-133
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• 2005

The change of surface sediment composition, shoreline and transection of geography were studied to investigate the Typhoon(Maemi) effect in Naa Beach located in the south area of East sea. In the backshore the volume of gravel is do creased, and increased in the volume of sand. The erosion in the sediment occurred to 4 m in the thickness and effected to 10 m in depth. And the coastline retreated to 12 m after typhoon. During typhoon conditions, higher amplitude waves deepen the wave base, causing much of the lower beach face and the offshore. The upper beach face is extensively eroded during typhoon and sand sediment is redeposited.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.1295-1299
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• 2008

Soil erosion is a natural process and has been occurring in most areas in the watershed. However, accelerated soil erosion rates have been causing numerous environmental impacts in recent years. To reduce soil erosion and sediment inflow into the water bodies, site-specific soil erosion best management practices (BMPs) need to be established and implemented. The most commonly used soil erosion model is the Universal Soil Loss Equation (USLE), which have been used in many countries over 30 years. The Sediment Assessment Tool for Effective Erosion Control (SATEEC) ArcView GIS system has been developed and enhanced to estimate the soil erosion and sediment yield from the watershed using the USLE input data. In the last decade, the Soil and Water Assessment Tool (SWAT) model also has been widely used to estimate soil erosion and sediment yield at a watershed scale. The SATEEC system estimates the LS factor using the equation suggested by Moore and Burch, while the SWAT model estimates the LS factor based on the relationship between sub watershed average slope and slope length. Thus the SATEEC and SWAT estimated soil erosion values were compared in this study. The differences in LS factor estimation methods in the SATEEC and SWAT caused significant difference in estimated soil erosion. In this study, the difference was -51.9%(default threshold)$\sim$-54.5%(min. threshold) between SATEEC and non-patched SWAT, and -7.8%(default threshold)$\sim$+3.8%(min. threshold) between SATEEC and patched SWAT estimated soil erosion.