• Journal of Wetlands Research
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• v.17 no.2
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• pp.146-154
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• 2015

Domestic railway industry has grown in numbers, scale of railway ndustrial and operation because was focused on an environmentally sustainable transportation. However, it is not enough to treat and prevent heavy metals which occur as the railway operation increases. The heavy metals occurred when the operating railway and it will be flow into water system with rainfall effluent during rainfall. will flow out along with the rainfall effluent when rainfall comes. In case of a railway bridge, In particular, heavy metals were flow into the water system without any treatment from railway bridges where located nearby rivers and lakes. So, rainfall effluent from railway facilities was occurred pollution of water system. For the prevent of heavy metal runoff during rainfall, the adsorptivity of material in railway roadbed is important.In this study, adsorptivity of gravel which is main gravel and blast-furnace slag were conducted adsorption test and deducted Freundlich's and Langmuir's isothermal adsorption equations. Safety as railway subbase course material was evaluated using modeling. As a result, absorption amount of slag, Cd and Cu, was shown higher than gravel and Pb along with Zn showed higher absorption amount of gravel. However, absorption amount of slag was shown higher than gravel used as railway subbase course material as time passes by. Absorption features had more suitable determination coefficient of heavy metals in warm absorption type such as Langnmuir compared to warm absorption type like Freundlich. To add, they showed less transformation by about 10% compared to gravel in safety evaluation through modeling. This is a railway subbase course material that prevents water outflow of heavy metal thus we can know slag is needed to be used.

• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.5
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• pp.89-99
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• 2014

The goal of this study was to evaluate sediment reduction effects of VFS (vegetative filter strip) applied for Iksan area in Saemangeum watershed. This study simulated runoff and sediment load from different types of uplands using VFSMOD-W. The general upland characteristics of the study area was investigated to build reasonable scenarios of the simulation. The simulation scenarios were designed by various areas, shapes, and slopes of uplands. Grass mixture was selected as VFS vegetation and the size of VFS was fixed as 10 % of uplands area. Additionally 50mm, 100mm, 150mm of daily rainfall were applied for the runoff and sediment simulation. As results, the calculated runoff and sediment loads were obtained $20.7{\sim}1,030.6m^3$ and 568.4~675,731.4 kg for the range of 0.1~1.0 ha of uplands with 7 % and 15 % slopes. The reduction effects on runoff and sediment were obtained 5~10 % and 21.0~47.7 % respectively from VFS applications. The VFSMOD-W simulations showed that runoff tended to increase as upland area and amount of rainfall increased while sediment increased when slope, length and area of uplands and amount of rainfall increased. These results indicated that rainfall amount and upland size are the critical factors for the generation of runoff and sediment load. In order to support this conclusion, further studies such as, long term monitoring, field experiments, and to calibrate and evaluate the model are necessary.

• Journal of Korean Society on Water Environment
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• v.27 no.6
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• pp.868-876
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• 2011

A five-year field monitoring was conducted to monitor characteristics of suspended solid (SS) export from paddy fields. The observed EMCs of SS ranged 1.2~517 mg/L (avg. 52.1 mg/L) during storm period. The concentration of SS during non-storm period were 1.1~349.5 mg/L (avg. 36.1 mg/L). Monthly load of SS was high during summer when rainfall amount was high. The load was higher than that of May when tillage effect is expected. There was no significant relationship between SS EMCs and rainfall or drainage amount. However, effects of rainfall and drainage were found to be significant for event load of SS. But, there was no apparent relationship between rainfall amount of cropping period and load of SS for that period. The observed SS load was 164.8~456.0 kg/ha (avg. 301.2 kg/ha) and mostly occurred during storm period. This study results also suggested that SS load estimation by USLE equation for paddy field could be overestimated, if not carefully handled. Monitoring studies for various climate, soil, and agricultural management are required to get better scope of SS export from paddy fields.

• Journal of Wetlands Research
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• v.16 no.1
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• pp.19-32
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• 2014

The purpose of this paper is to obtain reliable rainfall data for runoff simulation and other hydrological analysis by the calibration of gauge rainfall. The calibrated gauge rainfall could be close to the actual value with rainfall on the ground. In order to analyze the wind effect of ground rain gauge, we selected the rain gauge sites with and without a windshield and standard rain gauge data from Chupungryeong weather station installed by standard of WMO. Simple linear regression model and artificial neural networks were used for the calibration of rainfalls, and we verified the reliability of the calibrated rainfalls through the runoff analysis using $Vflo^{TM}$. Rainfall calibrated by linear regression is higher amount of rainfall in 5%~18% than actual rainfall, and the wind remarkably affects the rainfall amount in the range of wind speed of 1.6~3.3m/s. It is hard to apply the linear regression model over 5.5m/s wind speed, because there is an insufficient wind speed data over 5.5m/s and there are also some outliers. On the other hand, rainfall calibrated by neural networks is estimated lower rainfall amount in 10~20% than actual rainfall. The results of the statistical evaluations are that neural networks model is more suitable for relatively big standard deviation and average rainfall. However, the linear regression model shows more suitable for extreme values. For getting more reliable rainfall data, we may need to select the suitable model for rainfall calibration. We expect the reliable hydrologic analysis could be performed by applying the calibration method suggested in this research.

• Journal of Korea Water Resources Association
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• v.32 no.6
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• pp.617-625
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• 1999

Global warming has begun since the industrial revolution and it is getting worse recently. Even though the increase of greenhouse gases such as $CO_2$ is thought to be the main cause for global warming, its impact on global climate has not been revealed clearly in rather quantitative manners. However, researches using General Circulation Models(GCMs) has shown the accumulation of greenhouse gases increases the global mean temperature, which in turn impacts on the global water circulation pattern. This changes in global water circulation pattern result in abnormal and more frequent meteorological events such as severe floods and droughts, generally more severe than the normal ones, which are now common around the world and is referred as a indirect proof of global warming. Korean peninsula also cannot be an exception and have had several extremes recently. The main objective of this research is to analyze the impact of global warming on the change of flood and drought frequency. Based on the assumption that now is a point in a continuously changing climate due to global warming, we analyzed the observed daily rainfall data to find out how the increase of annual rainfall amount affects the distribution of daily rainfall. Obviously, the more the annual rainfall depth, the more frequency of much daily rainfall, and vice versa. However, the analysis of the 17 points data of Keum river basin in Korea shows that especially the number of days of under 10mm or over 50mm daily rainfall depth is highly correlated with the amount of annual rainfall depth, not the number of dry days with their correlation coefficients quite high around 0.8 to 0.9.

• Journal of Applied Biological Chemistry
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• v.42 no.1
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• pp.29-33
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• 1999

The present study examined annual runoff loading of nitrogen and phosphorus in the paddy field from 1 May, 1997 to 30 April, 1998. In the investigated area, the amount of rainfall was 1,095.6 mm and 414.6 mm during cropping season and non-cropping season. The annual rainfall was 1,510.2 mm. The total amount of runoff water was 1,043.2 mm and 281.0mm during cropping season and non-cropping season, and the added total amount of runoff water during two seasons was 1,324.2 mm. The runoff loading of nutrients caused by runoff water was measured as follows. The total-N was 149.23 and $8.67kg\;ha^{-1}$ (total amount=$157.90kg^{-1}ha^{-1}yr^{-1}$), the ammonia-N 102.98 and $4.44kg\;ha^{-1}$ ($107.42kg^{-1}ha^{-1}yr^{-1}$), the nitrate-N 28.45 and $1.23kg\;ha^{-1}$ ($29.68kg^{-1}ha^{-1}yr^{-1}$), the total-P 4.16 and $0.38kg\;ha^{-1}$ ($4.54kg^{-1}ha^{-1}yr^{-1}$) during cropping and non-cropping season respectively. When the loss ratio was calculated based on amounts of chemical fertilizer, about 68.6% of nitrogen and 16.7% of phosphorus was lost by runoff from applied fertilizer amount.

• Journal of Korean Society for Geospatial Information Science
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• v.15 no.1 s.39
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• pp.39-46
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• 2007

Most areas in Kangwon Province are mountainous and vulnerable to landslide due to the rainy season in summer and the localized torrential downpour triggered by abnormal climate. In particular, the rainfall is one of direct reasons for landslide. In accordance with the analysis of the relevance between the landslide areas and the accumulated rainfall for four months, there are severe damages of landslide to the areas having more than 1,100 mm of rainfall during three(3) months. Further, it indicates that the more the accumulated rainfall is the greater the size of landslide. These analyses show that the rainfall causes the possible and potential landslide in the vulnerable areas. And also, it means that there exist strong possibilities of landslide even in the areas of lower vulnerability if the amount of rainfall is above certain standard level. Accordingly, in this study we stored the GIS database on the causes and factors of landslide in the southern parts of Kangwon province and conducted simulations on the change of distribution of vulnerable areas by varying the rainfall conditions and by using the evaluation data of landslide vulnerability. As such a result, we found that the landslide could potentially occur if the amount of rainfall is 200 mm and more.

• Proceedings of the Korea Water Resources Association Conference
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• 2017.05a
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• pp.188-188
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• 2017

Rainfall is an important input to hydrological models. The accuracy of hydrological studies for water resources and floods management depend primarily on the estimation of rainfall. Thailand is among the countries that have regularly affected by floods. Flood forecasting and warning are necessary to prevent or mitigate loss and damage. Merging near real time satellite-based precipitation estimation with relatively high spatial and temporal resolutions to ground gauged precipitation data could contribute to reducing uncertainty and increasing efficiency for flood forecasting application. This study tested the applicability of satellite-based rainfall for water resources management and flood forecasting. The objectives of the study are to assess uncertainty associated with satellite-based rainfall estimation, to perform bias correction for satellite-based rainfall products, and to evaluate the performance of the bias-corrected rainfall data for the prediction of flood events. This study was conducted using a case study of Thai catchments including the Chao Phraya, northeastern (Chi and Mun catchments), and the eastern catchments for the period of 2006-2015. Data used in the study included daily rainfall from ground gauges, telegauges, and near real time satellite-based rainfall products from TRMM, GSMaP and PERSIANN CCS. Uncertainty in satellite-based precipitation estimation was assessed using a set of indicators describing the capability to detect rainfall event and efficiency to capture rainfall pattern and amount. The results suggested that TRMM, GSMaP and PERSIANN CCS are potentially able to improve flood forecast especially after the process of bias correction. Recommendations for further study include extending the scope of the study from regional to national level, testing the model at finer spatial and temporal resolutions and assessing other bias correction methods.

• Journal of Korea Water Resources Association
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• v.35 no.5
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• pp.575-581
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• 2002

This study evaluates the variation of estimation error of area-average rainfall due to rainfall seasonality. Both the cases considering and not considering the spatial correlation are compared to derive the characteristics of estimation error. Similar cases with different accumulation time without considering the rainfall seasonality are also investigated. This study was applied to the Geum-river basin with total 28 rain gauge measurements haying more than 30 years of daily rainfall measurements. As results of the study we found that: (1) The absolute estimation error of monthly area-average rainfall show strong seasonality like the total rainfall amount. However, the relative estimation error normalized by its mean was estimated to have similar values about 5 to 8% except January and December. (2) The relative estimation error of annual area-average rainfall estimated was found to have the estimation error about 3% of its annual mean. (3) However, the relative estimation error normalized by the standard deviation remains almost the same for both monthly and annual rainfall amounts, which was estimated about 11% of its standard deviation. (4) Finally, the estimation error without considering the spatial correlation was found to become almost twice the estimation error with considering the spatial correlation.

• Journal of Environmental Science International
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• v.24 no.5
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• pp.601-613
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• 2015

On the study of the characteristics and life cycle of mesoscale convective band in type of airmass that occurred in the Honam area from June to September for only 4 years in the period of 2009~2012, 10 examples based on the amount of rainfall with AWS 24 hours/60 minutes rainfalls, Mt. Osung radar 1.5 km CAPPI/X-SECT images and KLAPS data for convective band with heavy rainfall event were selected. There were analyzed and classified by using the convective band with heavy rainfall occurred along the convergence line of sea wind in the form of individual multi-cellular cell and moving direction of convective band appeared in a variety of patterns; toward southwestern (2 cases), northeastern (4 cases), congesting (2 cases), and changing its moving direction (2 cases). The case study dated of the 17th Aug. 2012 was chosen and implemented by sequentially different evolution of its shape along the convergence line of sea wind cell and moving direction of convective band as equivalent potential temperatures at the lower layer have increased to the upper layer 500 hPa, that the individual cells were developed vertically and horizontally through their merger, but owing to divergence caused by weakened rainfall and descending air current, the growth of new cell was inhibited resulting in dissipation of convective cells.