• Journal of Korea Water Resources Association
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• v.31 no.5
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• pp.621-635
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• 1998

The feasibility of cloud seeding in Korea is presented from analyses of precipitation, cloud amount, satellite data, and upper air data. The daily mean precipitation over Dae-Kwan-Ryong is the largest(~4.5 mm/day), while the intensity of precipitation (amount of yearly rainfall divided by the frequency of rain days) over Southern area is above 14 mm/day, which shows the largest in Korea. Both the daily mean and the intensity of precipitation over Andong area are the smallest with values of ~2.7 mm/day and ~11 mm/day, respectively. In the meanwhile, the occurrence frequency of appropriate cloud top temperature (-10'~-30') for cloud seeding over the region has a large value (~130 days/year). The precipitation patterns of the region vary with wind direction and intensity calculated from 43 AWSs(Automatic Weather Station) and the additional 7 rain guages which were installed along Northern and Southern part of the Sobaek mountain. The Sc(Stratocumulus) cloud type over Andong is frequently observed, and Cirrus and Altostratus next. From the results, it is estimated that the feasibility of cloud seeding over the area would be high if a proper strategy of cloud seeding is set up. LCL (Lifting Condensation Level) and CCL (Convective Condensation Level) have the most frequency in 1000-950 hPa being occupied 4/9 of total analysis period and in 400-500 hPa, respectively, with both small variations from season to season. The correlation between vapor mixing ratio and CCL is the highest in Summer and the lowest in Winter. It means that the height of cumulus in Summer is high with an abundant water vapor but vice versa in Winter, and that the strategy of cloud seeding should be different with seasons.

• Magazine of the Korean Society of Agricultural Engineers
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• v.26 no.2
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• pp.47-58
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• 1984

The study results of the mosture consumption character and irrigation effect of tomato, red pepper and chinese cabbage, in case the soil moisture is kept with different moisture content by the soil properties(loam, sandy loam, sand), are summarized as follows: 1. The available rainfall under bare soil condition had an order of sand>sandy loam> loam and their average was 64.2%. 2. Total moisture consumption under bare soil condition had an order of loam>sandy loam>sand and their average was 4.2mm. 3. The amount of irrigated water to keep certain soil moisture under bare soil condition showed minimum in sand and maximum in loam. It is considered because the capillary phenomenon was more developed in loam. 4. Total moisture consumption of tomatoes under premature cultivation showed 925mm in maximum and had on order of loam>sandy loam>sand. In the aspect of re-irrigation point, it had an order of PF 1.5> PF 1.7>PF 2.1. In case the twenty years's drought frequency was taken into account, the target amount of irrigation water meeded for premature cultivation was 916mm and its average daily moisture consumption was 10.8mm. 5. Total moisture consumption of red pepper under open cultivation showed 1145mm in maximum and had an order of loam>Sandy loam>sand. In the aspect of re-irrigation frequency was taken into consideration the target amount of irrigation water was 1,174.8mm and its average daily moisture consumption was 8.0mm. 6. Total moisture consumption of autumn chinese cabbages was 349mm in maximum and had an order of loam>sandy loam>sand. In the aspect of re-irrigation point, it had an order of PF 1.5>PF 2.1>PF 2.7. In case the twenty year's drought frequency was taken into account, the target amount of irrigation water needed for chinese cabbage cultivation was 259.5mm and its average daily moisture consumption was 6.5mm. 7. It is effective to keep the soil moisture of tomato from PF 1.5 to PF 2.1 in loam and the soil moisture control was effective in sandy loam than red pepper and chinese cabbage. In sand, the production was severaly decreased and the re-irrigation point of PF 1.5 was effective.

• Journal of Korean Society of Disaster and Security
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• v.14 no.2
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• pp.51-59
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• 2021

Due to recent climate change, the flood damage is becoming larger due to the development of localized heavy rains. 2020.12 The Ministry of Environment provides 100-year flood flood map, but in the case of small rivers, river structures are designed at 50-80 years frequency, making it difficult to predict damage and provide evacuation information. This study prepared flood map of Donamcheon district in Geumnam-myeon, Sejong Special Self-Governing Province, which is a small stream and habitual flood zone. The flood level was calculated using HEC-RAS and the flood area was visualized through HEC-GeoRAS. The analysis results showed that property damage such as special crops and roads occurred during the 30-80 year frequency rainfall, and it affected private houses such as general residential areas and public land when the frequency occurred for 100 years. The results of the comparison and analysis of the flood map provided by the Ministry of Environment and the results of the HEC-GeoRAS simulation showed that the flood map provided by the Ministry of Environment did not consider small streams. Further studies on flood flood maps considering the large and small stream are needed in the future.

• Journal of Wetlands Research
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• v.20 no.4
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• pp.314-321
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• 2018

In order to quantify nonpoint source pollution, it was proposed to sample at regular intervals of 1 hour for the first 24 hours of storm runoff process by National Institute of Environmental Research for the mixed landuse watershed. However, high frequency sampling requires intensive laboratory analysis and labor costs. In order to investigate the effect of longer sampling interval on the load estimation compared to the 1 hour sampling method, analysis was conducted using monitoring data from rural subwatershed, urban subwatershed, and outlet of the Pungyeongjeongcheon watershed. Statistical analysis revealed that mean of load estimation was not significantly different up to 4 hour sampling frequency. However, 3 hour sampling interval was found to be appropriate for the BOD and TP when it is judged that 10% or less of the difference in loading amount between the 1 hour and other sampling interval is reasonable. The results of this study can be used to conduct an effective monitoring system.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.6
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• pp.793-800
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• 2018

It is necessary to determine an optimal design frequency for establishing stable flood control against frequent flood disasters. Depending on the importance of river and regional characteristics, design return periods are suggested from at least 50 years up to 200 years for river design. However, due to the wide range of applications, it is not desirable to reflect the geographical and flood control characteristics of river. In this study, Bayes theory was applied to seven evaluation factors to determine the optimal design return period of rivers in Chungcheongnam-do; urbanization flooded area, watershed area, basin coefficient, slope, water system and stream order, range of backwater effect, abnormal rainfall occurrence frequency. The potential flood damage (PFD) capacity was estimated considering climate change and the appropriate design return period was determined by analyzing the capacity of each district. We compared the design return periods of 382 rivers in Chungcheongnam-do with the existing design return periods. The number of rivers that were upgraded from the existing return period were 65, which have relatively large flooding areas and have large PFDs. Whereas, the number of rivers that were downgraded were 169.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.25 no.6
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• pp.51-64
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• 2022

Along with the urbanization, the risk of urban flooding due to climate change is increasing. Flood regulation, one of the ecosystem services, is implemented in the different level of function of flood risk mitigation by the type of ecosystem such as forests, arable land, wetlands etc. Land use changes due to development pressures have become an important factor in increasing the vulnerability by flash flood. This study has conducted evaluating the urban flood regulation service using InVEST UFRM(Urban Flood Risk Model). As a result of the simulation, the potential water retention by ecosystem type in the event of a flash flood according to RCP 4.5(10 year frequency) scenario was 1,569,611 tons in urbanized/dried areas, 907,706 tons in agricultural areas, 1,496,105 tons in forested areas, 831,705 tons in grasslands, 1,021,742 tons in wetlands, and 206,709 tons in bare areas, the water bodies was estimated to be 38,087 tons. In the case of more severe 100-year rainfall, 1,808,376 tons in urbanized/dried areas, 1,172,505 tons in agricultural areas, 2,076,019 tons in forests, 1,021,742 tons in grasslands, 47,603 tons in wetlands, 238,363 tons in bare lands, and 52,985 tons in water bodies. The potential economic damage from flood runoff(100 years frequency) is 122,512,524 thousand won in residential areas, 512,382,410 thousand won in commercial areas, 50,414,646 thousand won in industrial areas, 2,927,508 thousand won in Infrastructure(road), 8,907 thousand won in agriculture, Total of assuming a runoff of 50 mm(100 year frequency) was estimated at 688,245,997 thousand won. In a conclusion. these results provided an overview of ecosystem functions and services in terms of flood control, and indirectly demonstrated the possibility of using the model as a tool for policy decision-making. Nevertheless, in future research, related issues such as application of models according to various spatial scales, verification of difference in result values due to differences in spatial resolution, improvement of CN(Curved Number) suitable for the research site conditions based on actual data, and development of flood damage factors suitable for domestic condition for the calculation of economic loss.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.28 no.1B
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• pp.55-64
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• 2008

The evidence of changes in the climate system is obvious in the world. Nevertheless, at the current techniques for flood frequency analysis, the flood distribution can not reflect climate change or long-term climate cycles. Using a linear regression and a Mann-Kendall test, trends in annual maximum precipitation and flood data for several major gauging sites were evaluated. Moreover, this research considered incorporating flood trends by climate change effects in flood frequency analyses. For five rainfall gauging sites (Seoul, Incheon, Ulleungdo, Jeonju, and Gangneung), upward trends were observed in all gauged annual maximum precipitation records but they were not statistically significant. For three streamflow gauging sites (Andong Dam, Soyanggang Dam, and Daecheong Dam), upward trends were also observed in all gauged annual maximum flood records, but only the flood at Andong Dam was statistically significant. A log-normal trend model was introduced to reflect the observed linear trends in annual maximum flood series and applied to estimate flood frequency and risk for Andong Dam and Soyanggang Dam. As results, when the target year was 2005, 50-year floods of the log-normal trend model were 41% and 21% larger then those of a log-normal model for Andong Dam and Soyanggang Dam, respectively. Moreover, the estimated floods of the log-normal trend model increases as the target year increases.

• Journal of Korea Water Resources Association
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• v.40 no.10
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• pp.793-800
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• 2007

This research applied to Wavelet transform that have soft resolution time and frequency area for stage of Hadong2 station in order to extract to discharge component by rainfall and tidal level component by tide. Approximation component(A6) of last level for wavelet decomposition displayed the biggest energy value 87.77%, and detail component(D3) energy value was 10.70% with periodicity of semidiurnal tide type(about 12 hours). Also skewness, kurtosis values of D3 have similar to tidal level of Yeosu. Approximation component(A6), Detail component(D6, D5) for Hadong2 stage was runoff component, and detail component(D4, D3, D2) was tide component according to effect of tide.

• Journal of Korea Water Resources Association
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• v.40 no.10
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• pp.823-832
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• 2007

In this study, the separation of short and long durations for estimation the parameters of IDF curve is suggested by using Multi-Objective Genetic Algorithm (MOGA). Objective functions are to minimize root mean squared error (RMSE) and relative RMSE between observed and computed values. The criteria for separation are two; the first one is to estimate more precisely the parameters of IDF curve and the second is to make a single IDF curve without non-continuous duration point. For this purpose 22 rainfall recording gauges operated by Korea Meteorological Administration are selected and three IDF curves that are used generally in South Korea are tested. The result shows that the IDF curve developed by Heo et al. (1999) would be the best of three tested IDF curves, and the suggested parameter estimation method using MOGA can compute more reliable parameters compared with empirical regression analysis.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.32 no.3D
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• pp.213-222
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• 2012

After enforcing 2007 semi-public management system of intra-city bus, Busan city has tried to promote the bus utilization through bus service improvements. As an effort for this, we attempted to clarify the main factors affecting to bus service satisfaction targeting intra-city bus users. In this study, 20 subcategories of intra-city bus service were assorted into 6 factors: Basic Service, Safe Driving, Route Information, Comfort, Cleanliness and Facilities, then the preference for each detailed bus service were analyzed. And the effects for bus service satisfaction were shown under the various conditions according to the general characteristics of intra-city bus users (gender, age), behavioral traffic characteristics (frequency of use, boarding time) and transportation environments (temperature, rainfall). These results would be important basic data for decision-making in bus policy for climate change and establishment of operating plan for bus utilization.