• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.8
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• pp.34-40
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• 2017

In recent years, global warming has caused abnormal weather phenomena. Unusually cold climates have occurred all around the world, including cold waves in the Northeastern United States, Beijing, China, Southern India, and Pakistan, as well as floods in Chile, Kazakhstan, and Vietnam. China has been experiencing a nationwide heat wave annually since the year 2013, especially in the southern region. In this study, we used Landsat 8 OLI TIRS sensor images from four periods to analyze the characteristics of abnormal high temperature phenomena in Cixi-si, China. Land cover classification was performed using 10 bands of satellite imagery, and the surface temperature was extracted using the 10th thermal band. The results of the land cover classification of the fourth period show the changes of the time series quantitatively. The results of the surface temperature calculation provided both the average overall temperature and the average temperature of individual items. The temperature was found to be highest for buildings, followed by grassland, forest, agricultural land, water systems, and tidal flats in the same period.

• Journal of Korean Society of Forest Science
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• v.63 no.1
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• pp.51-60
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• 1984

Analysing the reports of disaster-related, average annual death of lives due to the meteorological disasters amounted to be 250, of which about 90 were due to landslide. According to the last 10-year reports, the average area of landslide occurred reaches 275 hectares per year in Korea. The total cost for rehabilitation could annually require more than about 2 billion Won (about US$ 2.5 million). The basic countermeasure policy against such heavy disasters should be definitely taken on prevention rather than rehabilitation after being damaged. However, prevention countermeasures against landslide-related disasters have not been strengthened in Korea although being important. Areas of high landslide hazard must be designated with increase in number from current 10 (35 cities and counties) to 17 (68 cities and counties included : Table 3). Number of regional Erosion Control Stations taking full charge of rehabilitating works on the damaged land resulted from landslide disaster has to increase from currently 15 stations to 25. The stone buttressed terrace structures on the hillside slopes, being typical erosion control measures in Korea have been recently recognized as one of the most effective rehabilitation measures for the land damaged by landslides.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.147-151
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• 2007

인위적인 온실가스 증가의 영향으로 지구의 기온이 상승하고 있으며, 우리나라에서도 이러한 전 지구적인 온난화 추세를 상회하는 경향을 보이고 있다. 20세기 후반부터 기후변화에 따른 강수량 및 집중호우의 증가 추세가 보고되고 있으며, 이에 따른 피해 또한 증가하고 있다. 이러한 이상기후 현상이 전 세계적으로 빈번히 발생하여 가용 수자원의 변동이 커지고 있다. 추가적인 댐 건설이 어려운 상황이고, 댐 운영의 불확실성에 의한 현실적인 운영의 어려움으로 인하여 보수적인 댐 운영이 이루어지고 있는 실정이므로, 한정된 수자원의 효율적인 이용과 예측이 요구되고 있다. 본 연구에서는 기상연구소에서 개발된 A2, B2 기후변화 시나리오에 따른 다목적댐에서의 용수공급능력의 변화에 대한 평가를 수행하였다. 대규모 유역의 대표적인 다목적댐을 선정하고 기후변화 시나리오별 유입량을 분석하였으며, 이를 저수지 모의운영 기법을 이용하여 기후변화 시나리오에 따른 각 댐의 신뢰도 95% 용수공급능력과 예상발전량을 산정함으로써 가용수자원을 평가하였다. 또한 다목적댐의 과거 실적 유입량 자료를 이용한 모의운영 결과와 비교하여 제시하였다. 과거 실적에 의한 결과와 비교할 때, 기후변화 시나리오에 따른 향후 국내 가용 수자원량에도 큰 변화가 있을 것으로 예측되었다. 이로부터 댐 운영에 있어서 홍수기의 안정적인 댐관리와 갈수기의 적절한 수자원 분배를 위한 방향을 제시할 수 있다. 본 연구의 결과는 향후 기후변화에 따른 저수지의 효율적인 운영을 위한 유역의 수자원 영향 평가에 활용할 수 있을 것으로 기대된다.댐의 순기능에 대한 정량적인 분석을 수행하였다. 또한 댐별 방류량을 변동하여 하류 주요지점에 미치는 유황개선효과를 정량화하였다. 마지막으로 댐의 효율을 최대화한 하류확보가능하천유지유량을 월별평균량으로 산정하였다. 이는 향후 오염총량제 기준유량 및 환경용수의 법제화를 통한 하천유지용수의 증가시 비구조적 대책의 공급가능 최대량으로 활용가능할 것으로 사료된다.원에서 인위적으로 방류한 양이 많았기 때문으로 추정할 수 있다. 두 지점의 1월 유출이 100 % 이상인 것은 동절기 하천 결빙으로 인한 유량파악이 힘든 것으로 나타났다. 1월의 하천수위는 계측기에 기록된 수위값으로 유량을 산정한 것이다. 3월, 10월, 12월의 유출이 많은 것은 전월말 발생한 강우의 영향으로 크게 나타났다.다. 5. 초장의 절대치는 품종간에 차이는 있으나 비교적 조파구간에는 초장에 큰 변이가 없었고 파종기가 늦어짐에 따라 짧아졌다. 초장의 신장속도는 파종기가 늦어짐에 따라 현저하게 빨라지고 특히 조생종이 만생종보다 더욱 가속적인 경향이었다. 따라서 최고초장과 최저초장과의 절대치의 차이는 조생종일수록 적고 만생종일수록 큰 격차를 보이었다. 6. 간직경에 있어서도 만생종은 일반적으로 조기파종할수록 굵고, 조생종과 중생종은 4월 25일 파종기가 가장 굵은 편이며 이보다 파종기가 지연 가늘어지는 경향이었다. 7. 간중은 품종의 조만생에 따라 약간의 차이는 있으나 대체로 적기(4월 25일~5월 15일)보다 조기 혹은 만기 파종하면 작아지나 파종기 이동에 따른 간중의 변화는 품종의 조만성에 따라 양상을 달리하여 조생종은

• Journal of Korea Water Resources Association
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• v.46 no.2
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• pp.195-204
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• 2013

As drought is phenomenon of nature with unavoidability and repeated characteristic, it is necessary to plan to respond to it in advance and construct drought management system to minimize its damage. This study suggested standard for classification of drought, which is appropriate for our nation to respond to drought by assessing drought severity in the regions for this study. For data collection, 61 locations were selected - the locations keep precipitation data over 30 years of observation. And data for monthly precipitation for 37 years from 1973 were used. Based on this, this study classified unified drought interval into four levels using drought situation phases which are used in government. For standard for classification of drought severity fit to our nation, status of main drought was referred and these are classified based on accumulated probability of drought - 98~100% Exceptional Drought, 94~98% Extreme Drought, 90~94% Severe Drought, 86~90% Moderate Drought. Drought index (SPI, PDSI) was made in descending order and quantitative value of drought index fit to standard of classification for drought severity was calculated. To compare classification results of drought severity of SPI and PDSI with actual drought, comparison by year and month unit were analyzed. As a result, in comparison by year and comparison by month unit of SPI, drought index of each location was mostly identical each other between actual records and analyzed value. But in comparison by month unit of PDSI for same period, actual records did not correspond to analyzed values. This means that further study about mutual supplement for these indexes is necessary.

• Journal of the Korea Institute of Building Construction
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• v.20 no.1
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• pp.83-91
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• 2020

The recent bridge construction projects is demanded more sophisticated risk management measures and loss forecasts to brace for risk losses from an increase in the trend of bridge construction. This study aims to analyze the risk factors that caused the loss of material in actual bridge construction and to develop a quantified predictive loss model, based on the past record of insurance payment by major domestic insurance companies for bridge construction projects. For the development of quantitative bridge construction loss model, the dependent variable was selected as the loss ratio, i.e., the ratio of insurance payout divided by the total project cost, while the independent variable adopted 1) Technical factors: superstructure type, foundation type, construction method, and bridge length 2) Natural hazards: typhoon and flood 3) Project information: construction period and total project cost. Among the selected independent variables, superstructure type, construction method, and project period were shown to affect the ratio of bridge construction losses. The results of this study can provide government agencies, bridge construction design and construction and insurance companies with the quantitative damage prediction and risk assessment services, using risk indicators and loss prediction functions derived from the findings of this study and can be used as a guideline for future basic bridge risk assessment development research.

• Journal of Korean Tunnelling and Underground Space Association
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• v.19 no.2
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• pp.161-177
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• 2017

This paper presents the design considerations and field applications on inflatable structure system to protect rapidly flooding damages in large section tunnel. This inflatable structure system is very valuably used to protect passively and rapidly the possibilities of tunnel damages by flooding threats and unusual leakage to be occurred during and after underground infrastructure. In particular, this system should be necessary in subsea tunnel. The predominant factors in the design of inflatable structure system are the leakage and friction characteristics between the inflater and tunnel liner. The analytical and experimental studies are performed to develop the design considerations and to examine the design parameters of the inflatable structure system. The analytical solutions are developed using membrane theory to suggest the design considerations. The relative friction tests of several fabric materials are also carried out to determine the friction characteristics according to the different friction conditions between inflater and tunnel surface. The test results show that the friction coefficients in wet surface condition are about 20% lower than the values in dry surface condition. In addition, virtual design of tunnel protection system for two virtual subsea tunnel sites which is under reviewing in Korea, is carried out based on this research. It is expected that the results of this research will be very useful to understand the inflater structure design and development the technology of tunnel protection structures in the future.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.545-553
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• 2021

The frequency by water disaster in urban areas are increasing continuously due to climate change and urbanization. Countermeasures are being conducted to reduce the damage caused by water disasters. An analysis based on permeability, one of the parameters that affect runoff, is needed to predict quantitative runoff in urban watersheds and study runoff reduction. In this study, the SWAT model was simulated for the oncheon stream basin, a representative urban stream in Busan. The permeability map was prepared by calculating the CN values for each hydrologic response unit. Based on the permeability map prepared, EPA SWMM analyzed the effect of LID technology application on the water cycle in the basin for short-term rainfall events. The LID element technology applied to the oncheon stream basin was rooftop greening in the residential complex, and waterproof packaging was installed on the road. The land cover status of the land selected based on the permeability map and the application of LID technology reduced the outflow rate, peak flow rate, and outflow rate and increased the infiltration. Hence, LID technology has a positive effect on the water cycle in an urban basin.

• Journal of Wetlands Research
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• v.23 no.2
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• pp.154-162
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• 2021

The naturally opened Han river estuary is a place where the flows of the Han river, Imjin river, Yaesung river meet with West Sea of Korea, so the hydrodynamic mechanism(Impact-Response) structure of Han river estuary is complex. Continuous observation and measurement due to the morphological characteristics at the estuary are required to maintain the estuary environment and river management facilities. However, the Sannam wetland(the study area) is in the military operation area. Therefore, Sannam wetland has the limited access under the control from military office. In 2020, there had a natural disaster due to flooding in August and COVID-19, and it made a survey hard. The noncontact survey technique, the analysis of LANDSAT images at Sannam wetland, was applied to analyze riverbed fluctuation and morphological transformation around Sannam wetland. LANDSAT images obtained from EarthExplorer, USGS and analyzed by QGIS. The analysis was performed based on the area and the distance near Sannam wetland. As a result, an erosion was happened on the downstream of the study area, and the upstream of the study area did not have any serious sediment transport. Considering the resolution of LANDSAT images, this noncontect survey technique is applicable to manage the study area. From the analysis of LANDSAT images, it is assumed that the tidal effect is greater than the inflow from the upstream. The pattern change of tidal response causes the damage of the river facilities near the Hangang river estuary.

• Journal of the Korean Association of Geographic Information Studies
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• v.27 no.2
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• pp.34-44
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• 2024

Recently, due to abnormal climate caused by climate change, natural disasters such as floods, landslides, and soil outflows are rapidly increasing. In Korea, more than 63% of the land is vulnerable to slope disasters due to the geographical characteristics of mountainous areas, and in particular, Quarry mines soil and rocks, so there is a high risk of landslides not only inside the workplace but also outside.Accordingly, this study built a DEM using UAV and aviation LiDAR for monitoring the quarry, conducted a time series change analysis, and proposed an optimal DEM construction method for monitoring the soil collection site. For DEM construction, UAV and LiDAR-based Point Cloud were built, and the ground was extracted using three algorithms: Aggressive Classification (AC), Conservative Classification (CC), and Standard Classification (SC). UAV and LiDAR-based DEM constructed according to the algorithm evaluated accuracy through comparison with digital map-based DEM.

• Journal of Korea Water Resources Association
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• v.54 no.spc1
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• pp.1095-1105
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• 2021

The advancement of dam operation is further required due to the upcoming rainy season, typhoons, or torrential rains. Besides, physical models based on specific rules may sometimes have limitations in controlling the release discharge of dam due to inherent uncertainty and complex factors. This study aims to forecast the water level of the nearest station to the dam multi-timestep-ahead and evaluate the availability when it makes a decision for a release discharge of dam based on LSTM (Long Short-Term Memory) of deep learning. The LSTM model was trained and tested on eight data sets with a 1-hour temporal resolution, including primary data used in the dam operation and downstream water level station data about 13 years (2009~2021). The trained model forecasted the water level time series divided by the six lead times: 1, 3, 6, 9, 12, 18-hours, and compared and analyzed with the observed data. As a result, the prediction results of the 1-hour ahead exhibited the best performance for all cases with an average accuracy of MAE of 0.01m, RMSE of 0.015 m, and NSE of 0.99, respectively. In addition, as the lead time increases, the predictive performance of the model tends to decrease slightly. The model may similarly estimate and reliably predicts the temporal pattern of the observed water level. Thus, it is judged that the LSTM model could produce predictive data by extracting the characteristics of complex hydrological non-linear data and can be used to determine the amount of release discharge from the dam when simulating the operation of the dam.