• Journal of Korea Water Resources Association
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• v.49 no.12
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• pp.995-1006
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• 2016

According to 5th IPCC Climate Change Report, there is a very high likelihood that the frequency and intensity of extreme rainfall events will increase. In reality, flood damage has increased, and it is necessary to estimate the future probabilistic design rainfall amount that climate change is reflected. In this study, the future probabilistic design precipitation amount is estimated by analyzing trends of future annual maximum daily rainfall derived by RCP 8.5 scenarios and using the scale-invariance technique. In the first step, after reviewing the time-scale characteristics of annual maximum rainfall amounts for each duration observed from 60 sites operating in Korea Meterological Administration, the feasibility of the scale-invariance technique are examined using annual daily maximum rainfall time series simulated under the present climate condition. Then future probabilistic design rainfall amounts for several durations reflecting the effects of climate change are estimated by applying future annual maximum daily rainfall time series in the IDF curve equation derived by scale-invariance properties. It is shown that the increasing trend on the probabilistic design rainfall amount has resulted on most sites, but the decreasing trend in some regions has been projected.

• Journal of Korea Water Resources Association
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• v.43 no.5
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• pp.445-453
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• 2010

Energy loss at manholes, often exceeding friction loss of pipes under surcharged flow, is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze head losses at manholes, especially in case of surcharged flow. Hydraulic experimental apparatus which can change the manhole shape (square, circular) were installed for this study. In the experiments, two inflows ($Q_1,\;Q_2$) were varied from 0 to $4{\ell}$/sec and 15 combinations were tested in total. The flow ratios $Q_2/Q_3$ were varied from 0 to 1 for a total flow $Q_3$ ($Q_3=Q_1+Q_3$) of 2, 3, and $4{\ell}$/sec, respectively. The variation of head losses were strongly influenced by the lateral inflow because the head loss coefficient increases as the flow ratio $Q_2/Q_3$ increases. There was no significant difference of head loss between square manhole and circular one, and also no large variation of head loss as discharges change. The relation equations between K and $Q_2/Q_3$ were suggested in this paper.

• Journal of Korea Water Resources Association
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• v.41 no.3
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• pp.305-314
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• 2008

Urban sewer systems are designed to operate in open-channel flow regime and energy loss at circular manholes are usually not significant. However, the energy loss at manholes, often exceeding the friction loss of pipes under surcharge flow, is considered as one of the major causes of inundation in urban area. Therefore, it is necessary to analyze the head loss associated with manholes, especially in surcharge flow. Hydraulic experimental apparatus which can be changed the invert type(CASE A, B, C) and step height(CASE I, II, III) was installed for this study. The range of the experimental discharges were from $1.0{\ell}/sec$ to $5.6\;{\ell}/sec$. As the manhole diameter ratio($D_m/D_{in}$) increases, head loss coefficient increases due to strong horizontal swirl motion. Head loss coefficient was maximum because of strong oscillation of water surface when the range of manhole depth ratios($h_m/D_{in}$) were from 1.0 to 1.5. The average head loss coefficients for CASE A, B, and C were 0.45, 0.37, and 0.30, respectively. Accordingly, U-invert is most effective for energy loss reduction at circular manhole. This head loss coefficients could be available to design the urban sewer system with surcharge flow.

• Journal of the Korean Society of Hazard Mitigation
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• v.11 no.3
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• pp.143-150
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• 2011

Energy loss at manholes, often exceeding friction loss of pipes under surcharged flow, is considered as one of the major causes of inundation in urban area. Therefore, it is important to analyze the head losses at manholes, especially in case of surcharged flow. The stream characteristics were analyzed and head loss coefficients were estimated by using the computational fluid dynamics(CFD) model, FLUENT 6.3, at surcharged square manhole in this study. The CFD model was carefully assessed by comparing simulated results with the experimental ones. The study results indicate that there was good agreement between simulation model and experiment. The CFD model was proved to be capable of estimating the head loss coefficients at surcharged manholes. The head loss coefficients with variation of the ratio of manhole width(B) to inflow pipe diameter(d) and variation of the drop height at surcharged square manhole with a straight-path through were calculated using FLUENT 6.3. As the ratio of B/d increases, head loss coefficient increases. The depth and head loss coefficient at manhole were gradually increased when the drop height was more than 5cm. Therefore, the CFD model(Fluent 6.3) might be used as a tool to simulate the water depth, energy losses, and velocity distribution at surcharged square manhole.

• Proceedings of the Korea Water Resources Association Conference
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• 2021.06a
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• pp.120-120
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• 2021

2020년 8월 7일부터 8월 8일까지 호우는 용담댐, 섬진강댐, 합천댐 하류 유역의 막대한 침수피해를 일으켰다. 이들 다목적 댐 유입량의 신뢰도 높은 모의는 홍수기 댐 운영 및 하류하천의 홍수 해석에 필수다. 여기서는 일 유출 모의 기반으로 개발된 ONE 모형을 10분 단위, 1시간 단위로 적용한 결과를 제시하고자 한다. 보통 홍수모의는 사상별로 실시하지만, 여기서는 1월1일부터 12월 31일까지 연속으로 모의한 결과에서 해당 홍수사상 결과를 제시하였다. 3개 다목적 댐의 홍수사상은 8월6일부터 8월 10일까지 5일간으로 설정하였다. 유역면적은 용담댐, 섬진강댐, 합천댐, 각각 930km², 763km², 925km², 총강우량은 각각 490.7mm, 451.9mm, 452.4mm, 첨두유입량은 10분 단위는 각각 4,872.7m³/s, 3,533.7.0m³/s, 2,776.0m³/s, 1시간 단위는 각각 4,394.9m³/s, 3,401.8m³/s, 2,745.6m³/s, 총유입량은 각각 3억8,836만m³, 3억1,324만m³, 3억2,816만m³였다. 첨두유입량 상대오차가 0일 때의 매개변수로 모의한 결과를 제시하며, 총유입량 상대오차(Vq), R², RMSE, NSE 등으로 평가하였다. 용담댐 결과는 10분 단위 경우 최대면적강우량 7.3mm, 첨두유입량 4,872.4m³/s, 총유입량 3억 8,138만m³, Vq 1.9%, R² 0.968, RMSE 207.347, NSE 0.978였고, 1시간의 경우 최대면적강우량 29.6mm, 첨두유입량 4394.9m³/s, 총유입량 4억157만m³, Vq -8.4%, R² 0.970, RMSE 186.962, NSE 0.982였다. 섬진강댐 결과는 10분 단위 경우 최대면적강우량 9.2mm, 첨두유입량 3,533.3m³/s, 총유입량 2억7,223만m³, Vq 18.4%, R² 0.885, RMSE 808.296, NSE 0.925였고, 1시간의 경우 최대 면적강우량 37.9mm, 첨두유입량 3401.6m³/s, 총유입량 2억7,029만m³, Vq 13.7%, R² 0.907, RMSE 285.544, NSE 0.936였다. 합천댐 결과는 10분 단위 경우 최대면적강우량 5.5mm, 첨두유입량 2,776.2m³/s, 총유입량 3억3,667만m³, Vq -2.7%, R² 0.941, RMSE 191.896, NSE 0.965였고, 1시간의 경우 최대면적강우량 17.0mm, 첨두유입량 2,746.7m³/s, 총유입량 3억1,333만m³, Vq 4.5%, R² 0.965, RMSE 140.739, NSE 0.981였다. 이상 ONE 모형으로 10분, 1시간 단위의 댐 홍수 유입량 모의결과는 높은 신뢰도를 나타냈다.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.2B
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• pp.179-186
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• 2006

Effective interception area of street grate inlets was decreased by clogging with trash, debris, and sand. It also decreased the interception capability of grate inlets and increased the inundation area in street. Therefore, it is necessary to analyze the clogging characteristics and interception capability change by clogging for appropriate design and management of grate inlets. Hydraulic experimental apparatus which can be changed the gutter transverse slopes, longitudinal slopes of street and clogging condition of grate inlet ($40{\times}50cm$) was installed for this study. 81 total experiments were conducted with 8 different clogging condition. The interception capacities of grate inlets clogged curb direction are smaller than those of clogged flow direction. As the longitudinal slopes of street increase, the interception capacity of grate inlet decreases due to splash-over phenomena. This is also observed at grate inlets which has no clogging condition. In general, 50% of clogging factor was selected in design of grate inlet in foreign country. The clogging factor for same clogging condition are suggested 0.25~0.65 in domestic urban area.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.24 no.3
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• pp.27-34
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• 2024

The direct and indirect damages caused by fires in underground utility tunnels have a great impact on society as a whole, so efforts are needed to prevent and manage them in advance. To this end, research is ongoing to prevent disasters such as fire flooding by applying digital twin technology to underground utility tunnels. A network is required to transmit the sensed signals from each sensor to the platform. In essence, it is necessary to analyze the application of wireless networks in the underground utility tunnel environments because the tunnel lacks the reception range of external wireless communication systems. Within the underground utility tunnels, electromagnetic interference caused by transmission and distribution cables, and diffuse reflection of signals from internal structures, obstacles, and metallic pipes such as water pipes can cause distortion or size reduction of wireless signals. To ensure real-time connectivity for remote surveillance and monitoring tasks through sensing, it is necessary to measure and analyze the wireless coverage in underground utility tunnels. Therefore, in order to build a wireless network environment in the underground utility tunnels. this study minimized the shaded area and measured the actual cavity environment so that there is no problem in connecting to the wireless environment inside the underground utility tunnels. We analyzed the data transmission rate, signal strength, and signal-to-noise ratio for each section of the terrain of the underground utility tunnels. The obtained results provide an appropriate wireless planning approach for installing wireless networks in underground utility tunnels.

• Journal of Korean Society of Disaster and Security
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• v.12 no.2
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• pp.73-82
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• 2019

Recently, as the occurrence frequency of sudden floods due to climate change increased, the flood damage on riverside social infrastructures was extended so that there has been a threat of overflow. Therefore, a rapid prediction of potential flooding in riverside social infrastructure is necessary for administrators. However, most current flood forecasting models including hydraulic model have limitations which are the high accuracy of numerical results but longer simulation time. To alleviate such limitation, data driven models using artificial neural network have been widely used. However, there is a limitation that the existing models can not consider the time-series parameters. In this study the water surface elevation of the Hangang River bridge was predicted using the NARX model considering the time-series parameter. And the results of the ANN and RNN models are compared with the NARX model to determine the suitability of NARX model. Using the 10-year hydrological data from 2009 to 2018, 70% of the hydrological data were used for learning and 15% was used for testing and evaluation respectively. As a result of predicting the water surface elevation after 3 hours from the Hangang River bridge in 2018, the ANN, RNN and NARX models for RMSE were 0.20 m, 0.11 m, and 0.09 m, respectively, and 0.12 m, 0.06 m, and 0.05 m for MAE, and 1.56 m, 0.55 m and 0.10 m for peak errors respectively. By analyzing the error of the prediction results considering the time-series parameters, the NARX model is most suitable for predicting water surface elevation. This is because the NARX model can learn the trend of the time series data and also can derive the accurate prediction value even in the high water surface elevation prediction by using the hyperbolic tangent and Rectified Linear Unit function as an activation function. However, the NARX model has a limit to generate a vanishing gradient as the sequence length becomes longer. In the future, the accuracy of the water surface elevation prediction will be examined by using the LSTM model.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.5
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• pp.137-145
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• 2008

In this study, to reduce the flood damage caused by flood discharge exceeding project flood, the primary technology was applied to determining the optimal location and size for underground sluiceway. The Jungrang Stream was selected for this study because the stream was overflowed and the embankment section of the stream was destroyed owing to localized torrential rainfall in 1998 and 2001. Considering 200-year frequency storm, the inlets of the underground discharge channel were located at Seoul City limits, the confluence of Danghyun Stream, Wolgye 1-gyo, and the confluence of Mukdong Stream. The outlets were located at the estuary of Jungrang Stream and rightbank of Banpo Bridge in Han River. The transverse discharge according to the variation of overflow depth at the inlet of underground discharge channel was estimated and the effect of inundation reduction was analyzed. To examine the appropriate scale of the underground discharge channel, the 8 operation methods for the management of outlet discharge were compared considering four rules (only storage, the constant discharge rate, the constant discharge volume, and the mixture of the constant discharge rate and discharge volume). As a result, the effect of inundation reduction was most significantly improved when the inlet was located at the confluence of Danghyun Stream. The appropriate size of underground sluiceway for 200-year frequency storm was studied, and as a result, the appropriate diameters of the underground discharge channel were 12 m in case of only storage(Rule D), 9m in 50% of discharge(Rule E), 8 m in constant discharge volume(Rule F), and 7 m in mixture method(Rule G). This investigation process can be applied to design the underground discharge channel when the inundation damage is significant in coastal area due to embankment overflow. The underground discharge channel in Jungrang Stream can also be used as an underground road to link Seoul City to Uijeongbu City during dry season.