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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Korea Water Resources Association
Journal Basic Information
Journal DOI :
Korea Water Resources Association
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Volume & Issues
Volume 45, Issue 12 - Dec 2012
Volume 45, Issue 11 - Nov 2012
Volume 45, Issue 10 - Oct 2012
Volume 45, Issue 9 - Sep 2012
Volume 45, Issue 8 - Aug 2012
Volume 45, Issue 7 - Jul 2012
Volume 45, Issue 6 - Jun 2012
Volume 45, Issue 5 - May 2012
Volume 45, Issue 4 - Apr 2012
Volume 45, Issue 3 - Mar 2012
Volume 45, Issue 2 - Feb 2012
Volume 45, Issue 1 - Jan 2012
Selecting the target year
Comparison of Annual Maximum Rainfall Series and Annual Maximum Independent Rainfall Event Series
Yoo, Chul-Sang ; Park, Cheol-Soon ;
Journal of Korea Water Resources Association, volume 45, issue 5, 2012, Pages 431~444
DOI : 10.3741/JKWRA.2012.45.5.431
This study investigated the differences between annual maximum series and annual maximum independent rainfall event series with relatively short and long rainfall durations. Annual maximum independent rainfall events were selected by applying various IETDs and thresholds to the hourly rainfall data in Seoul for the duration from 1961 to 2010. Annual maximum independent rainfall event series decided were then compared with the conventional annual maximum series. Summarizing the results is as follows. First, the effect of IETD and threshold was not beyond the expected level. For example, as the IETD increases, the frequencies of independent rainfall events decreased similarly in their rate for both with short and long durations. However, as the threshold increases, the frequency of those with rather long durations decreased much higher. Second, The mean rainfall intensity of the independent rainfall events was found to remain constant regardless of their duration. This indicates that the annual maximum rainfall intensity could be found in a rainfall event with longer durations. Lastly, the difference between the annual maximum rainfall series and the annual maximum independent rainfall event series with rather short rainfall durations was found significantly large, which decreases with longer durations. This result indicates that the conventional data analysis method, especially for small basins with short concentration time, could lead an unrealistic design rainfall with little possibility of occurrence.
Effects of Reduced Sediment Dynamics on Fluvial Channel Geomorphology in the Jiseok River
Ock, Gi-Young ; Lee, Sam-Hee ;
Journal of Korea Water Resources Association, volume 45, issue 5, 2012, Pages 445~454
DOI : 10.3741/JKWRA.2012.45.5.445
The present study aims to investigate the long-term channel morphological changes derived from channelization, embankment and levee construction works in unregulated fluvial channel of the Jiseock River. Analyses of aerial photographs taken past (Year 1966) and recent (Year 2002) showed the temporally remarkable changes in channel planform such as channel shape, bar migration, vegetation encroachment in bar. During the period, the natural single threading changed into braided types together with decreasing sinuosity by 9.2%, increasing vegetation occupied bar ranged 97% of total bars area. Because such channel morphological changes are closely similar to those in dam downstream channels, we assume that both/either flow regime alteration and/or sediment transport discontinuity may be critical for the fixed channel and spread of vegetated bars even in unregulated river without dam reservoir upstream. We found more reduced frequency and magnitude of flooding water level comparing with past, but no significant alteration of inter annual water level variation. Bed material has been coarsened by 4~5 times and the riverbed has been degraded in overall channel but aggraded locally in conjunction reach of tributaries. The results indicates that reduced sediment dynamics in fluvial channel which derived by bed material coarsening, river bed degradation and unbalanced sediment transport capacity between tributary and mainstem can be a causal factor to trigger channel morphological changes even in unregulated rivers.
Development of Discretized Combined Unsteady Friction Model for Pipeline Systems
Choi, Rak-Won ; Kim, Sang-Hyun ;
Journal of Korea Water Resources Association, volume 45, issue 5, 2012, Pages 455~464
DOI : 10.3741/JKWRA.2012.45.5.455
In this study, a combined unsteady friction model has been developed to simulate the waterhammer phenomenon for the pipeline system. The method of characteristics has been employed as the modeling platform for the integration of the acceleration based model and the frequency dependant model for unsteady friction. Both Zielke's model and Ramos model were also compared with pressure measurements of a pilot plant pipeline system. In order to validate the modeling approach, a pipeline system equipped with the high frequency pressure data acquisition system was fabricated. The time series of pressure, introduced by a sudden valve closure, were obtained for two Reynolds numbers. A trial and error method was used to calibrate parameters for unsteady friction model. The comparison between different unsteady friction contributions in pressure variation provided the comprehensive understanding in the pressure damping mechanism of waterhammer. The proper evaluation of unsteady friction impact is a critical factor for accurate simulation of hydraulic transient.
Investigation into the Range of Effect of the Tide Level of Oncheon River Using Delft-3D
Lee, Sang-Hwa ; Lee, Han-Seung ; Kim, Jae-Jung ; Park, Dong-Hun ;
Journal of Korea Water Resources Association, volume 45, issue 5, 2012, Pages 465~472
DOI : 10.3741/JKWRA.2012.45.5.465
Recently, as the development of water front and natural type river is gradually increasing, it is mostly the case in that the flow analysis is implemented by only the flood level of the starting point without the tidal effect when the flood water level of the starting point is highly estimated than the high tidal water level in the design of river adjacent to an estuary. This research has analyzed the variation of tidal current for Oncheon river in Busan using Delft-3D program, considering that the tidal effect can cause the change of the flood water level of the starting point although the flood water level is higher than the flood tide level. As a result, considering the tidal effect at downstream boundary condition, water level indicates a periodicity of tide in particular region and the fluctuation range of water level is extended to upstream.
Development of 2D Depth-Integrated Hydrodynamic and Transport Model Using a Compact Finite Volume Method
Kim, Dae-Hong ;
Journal of Korea Water Resources Association, volume 45, issue 5, 2012, Pages 473~480
DOI : 10.3741/JKWRA.2012.45.5.473
A two-dimensional depth-integrated hydrodynamic and a depth-averaged passive scalar transport models were developed by using a Compact Finite Volume Method (CFVM) which can assure a higher order accuracy. A typical wave current interaction experimental data set was compared with the computed results by the proposed CFVM model, and resonable agreements were observed from the comparisons. One and two dimensional scalar advection tests were conducted, and very close agreements were observed with very little numerical diffusion. Finally, a turbulent mixing simulation was done in an open channel flow, and a reasonable similarity with LES data was observed.
Assessing Sustained Drought Impacts on the Han River Basin Water Supply System Using Stochastic Streamflows
Cha, Hyeung-Sun ; Lee, Gwang-Man ; Jung, Kwan-Sue ;
Journal of Korea Water Resources Association, volume 45, issue 5, 2012, Pages 481~493
DOI : 10.3741/JKWRA.2012.45.5.481
The Uncertainty of drought events can be regarded as supernatural phenomena so that the uncertainty of water supply system will be also uncontrollable. Decision making for water supply system operation must be dealt with in consideration of hydrologic uncertainty conditions. When ultimate small quantity of precipitation or streamflow lasts, water supply system might be impacted as well as stream pollution, aqua- ecosystem degradation, reservoir dry-up and river aesthetic waste etc. In case of being incapable of supplying water owing to continuation of severe drought, it can make the damage very serious beyond our prediction. This study analyzes comprehensively sustained drought impacts on the Han River Basin Water Supply System. Drought scenarios consisted of several sustained times and return periods for 5 sub-watersheds are generated using a stochastic hydrologic time series model. The developed drought scenarios are applied to assess water supply performance at the Paldang Dam. The results show that multi-year drought events reflecting spatial hydrologic diversity need to be examined in order to recognize variation of the unexpected drought impacts.
Feasibility Analysis of HEC-RAS for Unsteady Flow Simulation in the Stream Channel with a Side-Weir Detention Basin
Kim, Seo-Jun ; Hong, Sang-Jin ; Yoon, Byung-Man ; Ji, Un ;
Journal of Korea Water Resources Association, volume 45, issue 5, 2012, Pages 495~503
DOI : 10.3741/JKWRA.2012.45.5.495
It is necessary to perform the precise analysis of unsteady flow for effective design of the side-weir detention basin installed in the river. Generally, the HEC-RAS program, which is a 1D unsteady numerical model, is mostly used to simulate the unsteady flow for rivers. However, it is difficult to have confidence of unsteady flow results simulated by HEC-RAS due to the lack of experimental data and field monitoring data for the channel with a side-weir detention basin. Therefore, the purpose of this study is to validate or verify the simulation results calculated by HEC-RAS through the experiments for the open channel with a side-weir detention basin using specially-designed unsteady discharge-supply system. The experimental cases included unsteady flows in the straight channel with and without a side-weir detention basin. Especially, for the case with a detention basin, the experiment was performed to consider only the free flow condition over the side-weir. The study results showed that values of water level and discharge obtained from HEC-RAS coincided reasonably with experimental results with the maximum error of 3% for water level and 1% for discharge in the case of the flow without the side-weir detention basin and 4% for water level and 2% for discharge with the side-weir detention basin.
Uncertainty Assessment of Single Event Rainfall-Runoff Model Using Bayesian Model
Kwon, Hyun-Han ; Kim, Jang-Gyeong ; Lee, Jong-Seok ; Na, Bong-Kil ;
Journal of Korea Water Resources Association, volume 45, issue 5, 2012, Pages 505~516
DOI : 10.3741/JKWRA.2012.45.5.505
The study applies a hydrologic simulation model, HEC-1 developed by Hydrologic Engineering Center to Daecheong dam watershed for modeling hourly inflows of Daecheong dam. Although the HEC-1 model provides an automatic optimization technique for some of the parameters, the built-in optimization model is not sufficient in estimating reliable parameters. In particular, the optimization model often fails to estimate the parameters when a large number of parameters exist. In this regard, a main objective of this study is to develop Bayesian Markov Chain Monte Carlo simulation based HEC-1 model (BHEC-1). The Clark IUH method for transformation of precipitation excess to runoff and the soil conservation service runoff curve method for abstractions were used in Bayesian Monte Carlo simulation. Simulations of runoff at the Daecheong station in the HEC-1 model under Bayesian optimization scheme allow the posterior probability distributions of the hydrograph thus providing uncertainties in rainfall-runoff process. The proposed model showed a powerful performance in terms of estimating model parameters and deriving full uncertainties so that the model can be applied to various hydrologic problems such as frequency curve derivation, dam risk analysis and climate change study.