• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.6B
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• pp.597-603
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• 2006

The purpose of this study is to improve the short term rainfall forecast skill using neural network model that can deal with the non-linear behavior between satellite data and ground observation, and minimize the flood damage. To overcome the geographical limitation of Korean peninsula and get the long forecast lead time of 3 to 6 hour, the developed rainfall forecast model took satellite imageries and wide range AWS data. The architecture of neural network model is a multi-layer neural network which consists of one input layer, one hidden layer, and one output layer. Neural network is trained using a momentum back propagation algorithm. Flood was estimated using rainfall forecasts. We developed a dynamic flood inundation model which is associated with 1-dimensional flood routing model. Therefore the model can forecast flood aspect in a protected lowland by levee failure of river. In the case of multiple levee breaks at main stream and tributaries, the developed flood inundation model can estimate flood level in a river and inundation level and area in a protected lowland simultaneously.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.5B
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• pp.469-479
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• 2006

In order to investigate characteristics of the primary flow and the secondary currents in meandering channels, the laboratory experiments were conducted in S-curved channels with angle of bend, $150^{\circ}$, and sinuosity of 1.52. The experimental conditions was decided varying average depth and velocity. Under these experimental conditions, spatial variations of the secondary currents in multiple bends were observed. The experimental results revealed that the distribution of primary flow in straight section is symmetric without respect to the experimental condition and the maximum velocity line of the primary flow occurs along the shortest path in experimental channel, supporting the result of previous works. The secondary currents in second bend became more developed than those in first bend. Particularly, the outer bank cell developed distinctively and the secondary current intensity was low at the straight section and high at the bends, periodically. Also, the secondary current intensity at the bends was as twice to three times as that at the straight section, and has its maximum value at the second bend. The turbulent flow characteristics of meandering channel was investigated with turbulent intensity of the primary flow and Reynolds shear stress. It was observed that the turbulent intensity is increasing when the velocity deviation of the primary flow is large whereas Reynolds shear stress increases when both the velocity deviation of the primary flow and the secondary current are large.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.4B
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• pp.345-354
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• 2006

Drought brings on long term damage in contrast to flood, on economic loss in the region, and on ecologic and environmental disruptions. Drought is one of major natural disasters and gives a painful hardship to human beings. So we have tried to quantify the droughts for reducing drought damage and developed the drought indices for drought monitoring and management. The Palmer's drought severity index (PDSI) is widely used for the drought monitoring but it has the disadvanges and limitations in that the PDSI is estimated by considering just climate conditions as pointed out by many researchers. Thus this study uses the SWAT model which can consider soil conditions like soil type and land use in addition to climate conditions. We estimate soil water (SW) and soil moisture index (SMI) by SWAT which is a long term runoff simulation model. We apply the SWAT model to Soyang dam watershed for SMI estimation and compare SMI with PDSI for drought analysis. Say, we calibrate and validate the SWAT model by daily inflows of Soyang dam site and we estimate long term daily soil water. The estimated soil water is used for the computation of SMI based on the soil moisture deficit and we compare SMI with PDSI. As the results, we obtained the determination coefficient of 0.651 which means the SWAT model is applicable for drought monitoring and we can monitor drought in more high resolution by using GIS. So, we suggest that SMI based on the soil moisture deficit can be used for the drought monitoring and management.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2D
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• pp.299-309
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• 2006

Railway noise and vibration has been recognized as major problems with the speed-up of rolling stock. As a kind of solution to these problems, the decrease of stiffness of track pad have been tried. However, in this case, overturning of rail due to lateral force should be considered because it can have effect on the safety of running train. Therefore, above two things - decrease of stiffness of track pad and overturning of rail due to lateral force - should be considered simultaneously for the appropriate determination of spring coefficient of track pad. With this viewpoint, minimum spring coefficient of track pad is estimated through the comparison between the theoretical relationship about the overturning of rail and 3-dimensional FE analysis result. Two kinds of Lateral force and wheel load are used as input loads. Extracted values from the conventional estimation formula and the Shinkansen design loads are used. It is found that the overturning of rail changes corresponding to the change of the stiffness of track pad and the ratio of lateral force to wheel load. Moreover, it is found that the analysis model can have influence on the results. Through these procedure, minimum spring coefficient of track pad is estimated.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2C
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• pp.73-80
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• 2006

The shear behavior of four different interfaces consisting of four types of geosynthetics was investigated, and both static and dynamic test for the geosynthetic interfaces were conducted. The monotonic shear experiments were performed by using an inclined board apparatus and large direct shear device. The interface shear strength obtained from the inclined board test was compared with calculated values from large direct shear tests. The comparison results indicated that direct shear tests show high possibility to over-predict the shear strength in the low normal stress range where direct shear tests are not performed. Curved failure envelopes were also obtained for interface cases where two static shear tests were conducted. By comparing the friction angles measured from three tests, i.e. direct shear, inclined board, and shaking table test, it was found that the friction angle might be different depending on the test method and normal stresses applied in the research. Therefore, it was concluded that the testing method should be determined carefully by considering the type of loads and the normal stress expected in the field with using the geosynthetic materials installed in the site.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1B
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• pp.39-50
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• 2006

The flood control offices of main rivers have used a storage function model to forecast flood stage in Korea and studies of flood forecasting actively have been done even now. On this account, the storage function model, which is used in flood control office, regression models and artificial neural network model are applied into flood forecasting of study watershed in this paper. The result obtained by each method are analyzed for the comparative study. In case of storage function model, this paper uses the representative parameters of the flood control offices and the optimized parameters. Regression coefficients are obtained by regression analysis and neural network is trained by backpropagation algorithm after selecting four events between 1995 to 2001. As a result of this study, it is shown that the optimized parameters are superior to the representative parameters for flood forecasting. The results obtained by multiple, robust, stepwise regression analysis, one of the regression methods, show very good forecasts. Although the artificial neural network model shows less exact results than the regression model, it can be efficient way to produce a good forecasts.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.2B
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• pp.219-231
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• 2010

The Reference Evapotranspiration Calculator Software (REF-ET) supports computational guidelines for the reference evapotranspiration using seventeen FAO Penman-Monteith (PM) equations simultaneously such as the ASCE and FAO standardized forms. The REF-ET can conveniently consider missing data predictions and regional site characterizations, when reference ET is computed on monthly, daily, and hourly time steps. The applicability of the REF-ET was estimated to simulate the reference ET using hourly weather data from Seoul weather station for 29 years. The result found that the FAO24-Rd and 1957-Makk equations closely concerned with solar radiation parameter which were the most highly correlated to reference ET computed by pan coefficient. In addition, the 1957-Makk equation was identified as the most correct computational method for reference ET by analysis of bias and root mean square error. The 1957-Makk equation could predict the reference ET within the error of less than 1.06 mm/day, though all the other equations tended toward overestimation of predicting the reference ET in comparison with refecence ET of pan. The results of this study suggest that the REF-ET will be applicable to support reference ET estimation for a variety of field condition and time-scale.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1C
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• pp.65-76
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• 2010

Recent earthquake events revealed that severe seismic damages were concentrated mostly at sites composed of soil sediments rather than firm rock. This indicates that the site effects inducing the amplification of earthquake ground motion are associated mainly with the spatial distribution and dynamic properties of the soils overlying bedrock. In this study, an integrated GIS-based information system for geotechnical data was constructed to establish a regional counterplan against ground motions at a representative metropolitan area, Seoul, in Korea. To implement the GIS-based geotechnical information system for the Seoul area, existing geotechnical investigation data were collected in and around the study area and additionally a walkover site survey was carried out to acquire surface geo-knowledge data. For practical application of the geotechnical information system used to estimate the site effects at the area of interest, seismic zoning maps of geotechnical earthquake engineering parameters, such as the depth to bedrock and the site period, were created and presented as regional synthetic strategy for earthquake-induced hazards prediction. In addition, seismic zonation of site classification was also performed to determine the site amplification coefficients for seismic design at any site and administrative sub-unit in the Seoul area. Based on the case study on seismic zonations for Seoul, it was verified that the GIS-based geotechnical information system was very useful for the regional prediction of seismic hazards and also the decision support for seismic hazard mitigation particularly at the metropolitan area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.29 no.2B
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• pp.193-205
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• 2009

Typhoons occurred in the tropical Pacific region, these might be affected the Korea moving toward north. The strong winds and the heavy rains by the typhoons caused a natural disaster in Korea. In the research, the heavy rainfall events based on typhoons were evaluated quantitative through various statistical techniques. First, probability precipitation and typhoon probability precipitation were compared using frequency analysis. Second, EST probability precipitation was calculated by Empirical Simulation Techniques (EST). Third, NL probability precipitation was estimated by coupled Nonparametric monte carlo simulation and Locally weighted polynomial regression. At the analysis results, the typhoons can be effected Gangneung and Mokpo stations more than other stations. Conversely, the typhoons can be effected Seoul and Inchen stations less than other stations. Also, EST and NL probability precipitation were estimated by the long-term simulation using observed data. Consequently, major hydrologic structures and regions where received the big typhoons impact should be review necessary. Also, EST and NL techniques can be used for climate change by the global warming. Because, these techniques used the relationship between the heavy rainfall events and the typhoons characteristics.

• Proceedings of the Korea Water Resources Association Conference
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• 2022.05a
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• pp.335-335
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• 2022

남한상세 기후변화 전망보고서(2021)는 2100년대 강원도 강수량이 현재보다 19% 증가하고, 평균기온이 현재보다 6.5℃ 상승할 것으로 공표했다. 강원도는 영동지역과 영서지역으로 분리돼 기후 차이가 분명하다. 기상청 ASOS 데이터(1986~2020)를 이용해 기후 특성을 확인한 결과 영동지역 강수량은 1,463mm, 평균기온은 10.5℃, 상대습도는 66%로 분석됐고, 영서지역 강수량은 1,307mm, 평균기온은 11℃, 상대습도는 68%로 분석됐다. 영동지역 강수량이 영서지역 강수량보다 약 156mm 더 많으며, 이는 영동지역에서 큰 규모의 우심 피해가 발생할 가능성이 존재함을 의미한다. 강원도 평년 우심 피해 현황을 살펴본 결과 영동지역은 5회(피해액: 62억 원), 영서지역은 24회(피해액: 62억원)가 발생했다. 이는 미래로 갈수록 더 심해질 것으로 판단되며, 이런 기상 재난을 객관적으로 판단할 수 있는 기준이 필요하다. 이에 본 연구에서는 기후변화에 따른 강원도 기후 재난취약성을 평가했다. 이를 위해 기후변화 위험성, 기후변화 민감도, 기후변화 적응능력 지표를 활용해 기후변화 취약성 지표를 선정했다. 기후변화 위험성 지표는 홍수(CWD, Rx5day, R30mm), 가뭄(CDD, SU, TX90p), 폭염(SU, TR, TN90p), 한파(ID, TX10p, FD)로 RCP 8.5 기후변화시나리오를 ETCCDI 지수에 적용했다. 기후변화 민감도와 기후변화 적응능력 지표는 국가통계포털, 강원통계정보, WAMIS에서 자료를 수집해 선정했다. 또한 재난취약성 지표를 4단계(Very Low, Low, High, Very High)로 구분했다. 홍수 취약성 평가 결과 2090년대 원주시, 춘천시, 횡성군이 Low에서 Very High로 단계가 격상됐다. 가뭄 취약성 평가 결과 2090년대 양양군, 영월군, 정선군이 Very Low에서 Very High로 단계가 격상됐다. 폭염 취약성 평가 결과 2090년대 삼척시, 태백시, 영월군이 Very Low에서 Very High로 단계가 격상됐다. 한파 취약성 평가 결과 삼척시, 태백시, 영월군이 High에서 Very Low로 단계가 격하됐다. 고로 강원도는 기후 재난취약성 평가 결과에 따른 미래 기후변화를 대비하고, 각 지역 특성에 맞는 복원력 관점 기후 재난 관리가 필요하다고 사료된다.