• Journal of Korea Water Resources Association
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• v.55 no.10
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• pp.835-841
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• 2022

The water level of the dam reservoir is an important data in the operation of the dam. reservoir storage can be calculated by using water levels or prepared for disasters such as drought and floods. However, the water level is measured near the dam, making it difficult to represent a reservoir with a large area, and there is a high possibility that the water surface will be distorted due to discharge. Furthermore, the results of the survey showed that the water level of the reservoir is irregular rather than constant, and the water level of the reservoir is repeatedly falling and rising by section. In order to calculate such a complex and irregular representative water level, the water level observation density of the reservoir must be increased. In this study, we tried to derive the optimum water level observation density for Hwacheon Dam. A reasonable water level measurement density was derived by investigating the water level elevation of the reservoir and statistically analyzing it. The observation density may vary depending on the size of the reservoir, so the same analysis was conducted on the Goesan Dam and Boseonggang Dam. According to the results, four Hwacheon dams, three Goesan dams, and seven Boseong River dams are needed for observation density.

• Korean Journal of Remote Sensing
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• v.38 no.5_3
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• pp.901-912
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• 2022

The frequency of disasters is increasing due to global climate change, and unusual heavy rains and rainy seasons are occurring in Korea. Periodic monitoring and rapid detection are important because these weather conditions can lead to drought and flooding, causing secondary damage. Although research using optical images is continuously being conducted to determine the waterbody, there is a limitation in that it is difficult to detect due to the influence of clouds in order to detect floods that accompany heavy rain. Therefore, there is a need for research using synthetic aperture radar (SAR) that can be observed regardless of day or night in all weather. In this study, using Sentinel-1 SAR images that can be collected in near-real time as open data, the UNet model among deep learning algorithms that have recently been used in various fields was applied. In previous studies, waterbody detection studies using SAR images and deep learning algorithms are being conducted, but only a small number of studies have been conducted in Korea. In this study, to determine the applicability of deep learning of SAR images, UNet and the existing algorithm thresholding method were compared, and five indices and Sentinel-2 normalized difference water index (NDWI) were evaluated. As a result of evaluating the accuracy with intersect of union (IoU), it was confirmed that UNet has high accuracy with 0.894 for UNet and 0.699 for threshold method. Through this study, the applicability of deep learning-based SAR images was confirmed, and if high-resolution SAR images and deep learning algorithms are applied, it is expected that periodic and accurate waterbody change detection will be possible in Korea.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2B
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• pp.141-153
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• 2009

The occurrence causes of the extreme rainfall to happen in Korea can be distinguished with the typhoons and local downpours. The typhoon events attacked irregularly to induce the heavy rainfall, and the local downpour events mean a seasonal rain front and a local rainfall. Almost every year, the typhoons and local downpours that induced a heavy precipitation be generated extreme disasters like a flooding. Consequently, in this research, There were distinguished the causes of heavy rainfall events with the typhoons and the local downpours at Korea. Also, probability precipitation was computed according to the causes of the local downpour events. An evaluation of local downpours can be used for analysis of heavy rainfall event in short period like a flash flood. The methods of calculation of probability precipitation used the parametric frequency analysis and the Empirical Simulation Technique (EST). The correlation analysis was computed between annual maximum precipitation by local downpour events and sea surface temperature, moisture index for composition of input vectors. At the results of correlation analysis, there were revealed that the relations closely between annual maximum precipitation and sea surface temperature. Also, probability precipitation using EST are bigger than probability precipitation of frequency analysis on west-middle areas in Korea. Therefore, region of west-middle in Korea should prepare the extreme precipitation by local downpour events.

• The Journal of Engineering Geology
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• v.34 no.2
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• pp.279-294
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• 2024

Large-scale civil engineering structures such as dams require a systematic approach to jointed rock-mass grouting to prevent water leakage into the foundations and to ensure safe operation. In South Korea, rock grouting design often relies on the experience of field engineers that was gained in similar projects, highlighting the need for a more systematic and reliable approach. Rock-mass grouting is affected mainly by hydrogeology and the presence of discontinuities, involving factors such as the rock quality designation (RQD), joint spacing (Js), Lugeon value (Lu), and secondary permeability index (SPI). This study, based on data from field investigations of 14 domestic sites, analyzed the correlation between hydrogeological factors (Lu and SPI), discontinuity characteristics (RQD and Js), and grout take, and systematically established a design method for rock grouting. Analysis of correlation between the variables RQD, Js, Lu, and SPI yielded Pearson correlation (r) values as follows: Lu-SPI, 0.92; RQD-Lu, -0.75; RQD-Js, 0.69; RQD-SPI, -0.65; Js-Lu, -0.47; and SPI-Js, -0.41. The grout take increases with Lu and SPI values, but there is no significant correlation between RQD and Js. The proposed approach for grouting design based on SPI values was verified through analysis and comparison with actual curtain-grouting construction, and is expected to be useful in practical applications and future studies.

• Journal of the Korean Institute of Traditional Landscape Architecture
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• v.33 no.4
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• pp.99-111
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• 2015

The objectives of this study were to investigate the location, shape, environment, and vegetation of the Village Forest in Gyeonggi-do and to evaluate the ecological integration and changes of the Village Forests to figure out the measures for conservation and management. There were 23 Village Forests remain in Gyeonggi-do. Ten Village Forests were established based on Feng-shui background. Many of them were found in Yongin area and southeast of Icheon. The Village Forests were owned by local community at 9 village and privately owned at 8 villages. Most Village Forests were managed by local communities except for the two managed by private person. Fifty-two percent of the Village Forests were in strip shape, and most of them were established by Feng-shui background or for the prevention of disasters. The average size of the Village Forests was relatively small at 3,046m2. The most frequent tree species found at the Village Forest were Zelkova serrata and Pinus densiflora. Over half of the number of Village Forests showed vertical structure of overstory trees only or overstory-sub overstory combination, which seemed to be resulted from the loss of understory plants by the activities of local residents. The Village Forests that had over 30% of damaged trees were found at 7 villages. The damages were caused by the road construction close to the groves, soil compaction, and tree death by covering lower stem with soil. The vitality of the damaged trees seemed to be significantly low compared to that of the undamaged. There were factors that determined the changes in the Village Forests: community ritual, institutional protection, designation as a water resource protection district, road construction, land use change, windstorm hazards, and development of forest areas. In order to conserve and manage the Village Forests appropriately, it is necessary to limit excessive use of the grove areas and maintain proper tree growing conditions by improving the soil environment. The development of neighborhood areas need to be controlled and community activities should be encouraged to maintain or restore the original landscape of the groves. Protection measures and supporting policies need to be enforced to keep the Village Forests from disappearing in near future.

• Journal of Korean Society of Forest Science
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• v.81 no.4
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• pp.337-345
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• 1992

In this research, a kinematic wave model was applied for the runoff analysis, Regulation of streamflow was estimated by the calibration of roughness coefficient as a parameter. The data analyzed were obtained from Ananomiya and Shirasaka experimental basins at Tokyo University Forest in Aichi. Estimation methods and characteristics of roughness coefficient as a evaluation method of hydrological function of forest are summarized as follows ; 1. Roughness coefficient($N_s$) indicates the resistance of hillslope to the flowing water of surface runoff. There exists an hypothesis that resistance of hillslope to flowing water increase with the growth forest and development of the $A_o$ layer. 2. Roughness coefficient($N_s$) was estimated by the parameter when the stream direct runoff was calculated by using the kinematic wave. 3. Secular change of '$N_s$' in ananomiya has a curve which has an upper limit and increases exponentially near the limit. The curve quickly increased from 1935 to 1945 when results of afforestation for erosion control were thought to be effective. On the other hand, slight increase of '$N_s$' in Shirasaka indicates that there was not such a big change in the surface of soil layer. 4. The increase of '$N_s$' was related with decrease of direct runoff and increase of base flow. It was recognized that the rate of direct runoff decreased with the improvement of forest physiognomy and the rate of base flow was increased. But absolute value of water runoff per one storm decreased in chronological order.