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REFERENCE LINKING PLATFORM OF KOREA S&T JOURNALS
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Journal of Korea Water Resources Association
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Journal DOI :
Korea Water Resources Association
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Volume & Issues
Volume 34, Issue 6 - Dec 2001
Volume 34, Issue 5 - Oct 2001
Volume 34, Issue 4 - Aug 2001
Volume 34, Issue 3 - Jun 2001
Volume 34, Issue 2 - Apr 2001
Volume 34, Issue 1 - Feb 2001
Selecting the target year
A Point Rainfal1 Model and Rainfall Intensity-Duration-Frequency Analysis
Yu, Cheol-Sang ; Kim, Nam-Won ; Jeong, Gwang-Sik ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 577~586
This study proposes a theoretical methodology for deriving a rainfall intensity-duration- frequency (I-D-F) curve using a simple rectangular pulses Poisson process model. As the I-D-F curve derived by considering the model structure is dependent on the rainfall model parameters estimated using the observed first and second order statistics, it becomes less sensitive to the unusual rainfall events than that derided using the annual maxima rainfall series. This study has been applied to the rainfall data at Seoul and Inchon stations to check its applicability by comparing the two I-D-F carves from the model and the data. The results obtained are as followed. (1) As the duration becomes longer, the overlap probability increases significantly. However, its contribution to the rainfall intensity decreases a little. (2) When considering the overlap of each rainfall event, especially for large duration and return period, we could see obvious increases of rainfall intensity. This result is normal as the rainfall intensity is calculated by considering both the overlap probability and return period. Also, the overlap effect for Seoul station is fecund much higher than that for Inchon station, which is mainly due to the different overlap probabilities calculated using different rainfall model parameter sets. (3) As the rectangular pulses Poisson processes model used in this study cannot consider the clustering characteristics of rainfall, the derived I-D-F curves show less rainfall intensities than those from the annual maxima series. However, overall pattern of both I-D-F curves are found very similar, and the difference is believed to be overcome by use of a rainfall model with the clustering consideration.
Design Technique of Rainwater Utilizing System
Jeon, In-Bae ; Song, Si-Hun ; Ji, Hong-Gi ; Lee, Sun-Tak ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 587~596
The purpose of this study is to improve inefficient use of rainwater in island area where it uses rainwater to supply the domestic water and to propose rainwater utilizing system that is most appropriate to the characteristics of precipitation in Korea. To accomplish these purposes, Cheju island was chosen as a study area and the design for the roof area and tank size of rainwater utilizing system was based on the result of the relationship between the actual precipitation and domestic water data which was used in the analysis by run theory to use run theory. Since the result of the analysis indicated that the designed rainwater catchment system was operated stably in Cheju island, the same result is expected in other island too. Therefore, if this system is executed together with the roof rehabilitation work of island area, it will bring positive effects on broth the improvement of residental environment and the security of domestic water.
Estimating the Variations of Tidal Flat Areas after the Seawall Construction from Topographic Maps, Hydrographic Charts, and Satellite Images
Gang, Mun-Seong ; Park, Seung-U ; Kim, Sang-Min ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 597~604
The objective of the paper was to estimate the changes in acreages of tidal flats after the seawall construction at the Asan Bay and the Chunsu Bay from topographic maps, hydrographic charts, and Landsat TM images. The tidal floats from topographic maps published in one year differ significantly from that in the other, which appears to be attributed to the tide levels at the time of photographing. The hydrographic charts showed that tidal flats increase at rates of 22.3 ha/yr at the Asan Bay and 56.6 ha/yr at the Chunsu Bay after the dike construction. Applying the ISODATA method of unsupervised classifications for the Landsat TM images, the tidal flats were identified, and the resulting acreages for each image estimated. The resulting tidal flats increased at the rates of 21.3 ha/yr at the Asan Bay and 47.3 ha/yr at the Chunsu Bay during twelve years after the dike construction. It was found that the rates of the annual increases from the two data are very close and the differences result from the coastal lines at the charts and the TM images.
Visualization of the Water Column Collapse by using SMAC Method
Kim, Nam-Hyeong ; Kim, Nam-Guk ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 605~615
SMAC method, one of the numerical simulation techniques, is modified from the original MAC method for the time-dependent variation of fluid flows. The Navier-Stokes equations for incompressible time-dependent viscous flow is applied, and marker particles which present the visualization of fluid flaws are used. In this study, two-dimensional numerical simulations of the water column collapse are carried out by SMAC method, and the simulation results are compared with Martin and Moyce's experimental data and result of the MPS method. A good results are obtained. This numerical simulation could also be applied to the breaking phenomenon of hydraulic structures such as dam break.
Identification of Expanding the Usability of the Water Resources in Hwacheon Dam System Due to the Flood Surcharging Effects of Peace Dam
Yu, Ju-Hwan ; Park, Chang-Geun ; Jo, Hyo-Seop ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 617~625
Peace dam constructed against the water attack had stopped in the first step, linked with Hwacheon dam through bypass tunnels and had an effect of flood surcharging in its pocket on Hwacheon dam downstream. To study the utility of Peace dam, the flood control effects of Peace dam and the restricted water level (RWL) in Hwacheon dam were reviewed and identified with operating Hwacheon dam system. Analysing the results the ideas of expanding the usability of the water resources in Hwacheon dam system were suggested. To do that, the criteria and the model of reservoir operation were established frist and the optimization of the operation have done. Based on the results the performance of the optimization was evaluated as an reference coefficient with relative value of the registered data to the optimized. And examining several alternatives for the RWL in Hwacheon reservoir operation made more feasible RWL suggested. And its economic benefit was also reckoned.
The Development of Synthetic Unit Hydrograph Suitable to the Hydrologic Characteristics in Korea
Jeong, Seong-Won ; Mun, Jang-Won ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 627~640
Generally, the synthetic unit hydrograph method is presented to estimate the design flood in the ungaged watershed. However, due to the lack of rainfall-runoff data, the models developed in other countries such as U.S.A. and Japan have been widely used in Korea. Therefore, it may be essential to develope the rainfall-runoff model suitable for the hydrological char-acteristics in Korea. In this study, the representative unit hydrographs are derived from rainfall-runoff data at 19 basins in Selma-Cheon and 3-IHP experimental watersheds using ridge-regression method and Nash model. And a new synthetic unit hydrograph for Korea is suggested by integrating the described results and previous studies on unit hydrograph. The newly developed method is represented as two regression forms with three independent variables of watershed area, channel length, and channel slope by multiple regression analysis is carried out for each watershed, the coefficients of determination are not improved in all cases compared out for each watershed, the coefficients of determination are not improved n all cased the synthetic unit hydrograph for each watershed. Therefore, when the new method is applied to some watersheds, the result analyzed for all data has to be used.
An Experimental Study on Local Scour Around Group Pile Foundation
Yun, Byeong-Man ; Seo, Jeong-Pil ; No, Yeong-Sin ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 641~649
This study analyzed the general scour characteristics around group pile foundations through laboratory experiments. The experiments were performed for the pile groups consisting of 4, 9, 15 and 35 piles to investigate the effects of pile number, mean velocity and the angle of attack on the scour hole shape, and the magnitude and the position of maximum scour depth. Results reveal that the maximum scour depth for 4 and 9 piles have almost same values with single pier case regardless of approach velocity. The scour depth for 15 and 35 piles, however, increases as the mean velocity increases and reaches up to 2.2 times of maximum scour depth for single pier case. As the number of piles increase, the single scour holes are superposed and the overall scour hole turned out to be rectangular shape. The experimental results for the case of 35 piles indicate that the scour depth has the maximum value at angle of attack of 35 degree and that the main scour hole is formed in diagonal direction.
Long Waves Generated by Short Wave Groups over a Step: Governing Equations
Jo, Yong-Sik ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 651~657
The second-order long waves generated by short wave groups propagating over a step are theoretically investigated. The diffraction of short waves is firstly formulated and the governing equations of second-order long waves are then derived by using a multiple-scale perturbation method. It is observed that free and locked long waves are generated and propagated with different velocities.
The Comparison of Existing Synthetic Unit Hydrograph Method in Korea
Jeong, Seong-Won ; Mun, Jang-Won ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 659~672
Generally, design flood for a hydraulic structure is estimated using statistical analysis of runoff data. However, due to the lack of runoff data, it is difficult that the statistical method is applied for estimation of design flood. In this case, the synthetic unit hydrograph method is used generally and the models such as NYMO method, Snyder method, SCS method, and HYMO method have been widely used in Korea. In this study, these methods and KICT method, which is developed in year 2000, are compared and analyzed in 10 study areas. Firstly, peak flow and peak time of representative unit hydrograph and synthetic unit hydrograph in study area are compared, and secondly, the shape of unit hydrograph is compared using a root mean square error(RMSE). In Nakayasu method developed in Japan, synthetic unit hydrograph is very different from peak flow, peak time, and the shape of representative unit hydrograph, and KICT method(2000) is superior to others. Also, KICT method(2000) is superior to others in the aspects of using hydrologic and topographical data. Therefore, Nakayasu method is not a proper in hydrological practice. Moreover, it is considered that KICT model is a better method for the estimation of design flood. However, if other model, i.e. SCS method, Nakayasu method, and HYMO method, is used, parameters or regression equations must be adjusted by analysis of real data in Korea.
Estimation on Drought Indicator Using Various Time Series
Im, Gyeong-Jin ; Sim, Myeong-Pil ; Seong, Gi-Won ; Lee, Hyeon-Jae ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 673~685
In this study, the drought indicator is calculate from the rainfall, daily highest temperature, streamflow and Palmer Drought Severity Index(PDSI) for water plan and drought management in a relatively wide region. Three levels of drought severity, called drought watch, drought warning, and drought emergency, are established for these series which determine exceedance levels. The 25% nonexceedance level is used for drought watch, 10% for drought warning, and 5% for drought emergency to figure how well the drought indicators represent the past-drought and that those can be used for drought monitoring. As a result, 9-month and 12-month precipitation, and PDSI series shows the best consistency and high correlation indicate droughts. Because the results are based on the gauged data and simply calculated, the suggested indices can be used for basic data for drought monitoring system of a basin.
Development of Two-Dimensional Sediment Transport Model Using Observed Erosion Rate
Jeong, Tae-Seong ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 687~699
A 2-dimensional numerical sediment transport model has been developed by using erosion rates observed by SEDFLUME. The model un boundary-fitted coordinate can reduce inaccuracy of sediment model with accurate erosion data. Suspended transport and bed load transport are included in the model together. The model results gave good agreement with particle size distributions in 1-d channel and was more accurate than that of HIDAS of 1-dimensional model. The model applied to an enlarging channel to check model performance in 2-dimensional domain. Bed coarsening reduced erosion and deposition.
Water Quality Forecasting at Gongju station in Geum River using Neural Network Model
An, Sang-Jin ; Yeon, In-Seong ; Han, Yang-Su ; Lee, Jae-Gyeong ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 701~711
Forecasting of water quality variation is not an easy process due to the complicated nature of various water quality factors and their interrelationships. The objective of this study is to test the applicability of neural network models to the forecasting of the water quality at Gongju station in Geum River. This is done by forecasting monthly water qualities such as DO, BOD, and TN, and comparing with those obtained by ARIMA model. The neural network models of this study use BP(Back Propagation) algorithm for training. In order to improve the performance of the training, the models are tested in three different styles ; MANN model which uses the Moment-Adaptive learning rate method, LMNN model which uses the Levenberg-Marquardt method, and MNN model which separates the hidden layers for judgement factors from the hidden layers for water quality data. the results show that the forecasted water qualities are reasonably close to the observed data. And the MNN model shows the best results among the three models tested
A Study on Computation Methods of Monthly Runoff by Water Balance Method
Im, Dae-Sik ; Kim, Hyeong-Su ; Seo, Byeong-Ha ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 713~724
Hydrologists have tried to develop monthly runoff simulation models which are important factor in wafer resources planning. One of the models called Kajiyama formu]a is widely used for monthly runoff simulation in Korea. In recent work by Xiong and Guo (1999), they suggested Two-parameter monthly water balance model to simulate the runoff and showed that the model can be used for the water resources planning program and the climate impact studies. However, they estimated two parameters of transformation of time scale, c and of the field capacity, SC by the trial and error method. Therefore, the purpose of this study is to suggest the estimation methodologies of c and SC, and compare Kajiyama formula with a Two-parameter monthly water balance model to simulate the runoff in Han river and IHP representative basins in Korea. The c is estimated by using the relationship of actual and potential evaporations, and SC is estimated from association with CN. We show that the estimated c and SC can be used as the initial or optimal values in the model.
The Variation of the Residual Chlorine Concentration in a Distribution Reservoir
Lee, Sang-Jun ; Hyeon, In-Hwan ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 725~733
In this study, variation of effluent of residual chlorine concentration was estimated from bench scale distribution reservoir test according to variation of flow and baffle condition. According to the bench scale test results, when the flow rate was an unsteady state, difference between the case of no-baffle in the reservoir and the case of two-baffles in the reservoir became less than the condition when the effluent flow was in a steady state. Consequently, the results are caused by the flow rate variation. Thus, the baffle is less effective than a clearwell of steady state condition.
A Study of Runoff Curve Number Estimation Using Landsat Image
Jo, Hong-Je ; Kim, Gwang-Seop ; Lee, Chung-Hui ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 735~743
CN procedure has been proven to be useful method for evaluating the effects of changes in land-use and treatment on hydrology. In this study, the use of Landsat multi-spectral image was investigated for analyzing the land-use distribution. From the Landsat data, forest areas were classified according to the density of trees. Watershed CN's were calculated to analyze the effects of the density of trees and soil cover types on direct runoff. According to the results, the density of trees had a little effect while soil cover types had a large effect on CN, From the comparison of estimated runoffs from CN method with observed runoffs, detailed soil cover map provides improved results.
Fall Velocity Measurement in the Turbulent Flow Using Image Analysis Method
Yun, Sang-Hun ; Yu, Gwon-Gyu ; Yun, Byeong-Man ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 745~751
Fall velocities of sand particles in the turbulent flow are analyzed through measurements using PTV. PTV is believed to be the only instrument to measure the fall velocity in the turbulent flow, since it can trace the individual particle. The method is verified by comparison with existing formula for still-water case. The experimental results show that the fall velocity in the turbulent flow decreases compared with that in still water, and decreases by 40% as the turbulent intensity normalized by the friction velocity increases upto 1.
A formula for the Decision of the Riprap Size for the Local Scour Protection around Bridge Piers
Choe, Gye-Un ; Kim, Hyeon-Tae ; An, Gyeong-Su ;
Journal of Korea Water Resources Association, volume 34, issue 6, 2001, Pages 753~761
In this paper, the experiments to decide the riprap size for the local scour protection at bridge piers and the coefficients of attack angle were conducted. A formula for the decision of the riprap size and a figure for the coefficients of attack angle were suggested based upon the experimental results. The coefficients of attack angle indicate different values based on the variation of the length-width ratio of bridge pier and the coefficients are increased by the increment of the attack angle. In this paper, the experiments using the piers having the opening ratios of 90%, 92.86% and 95% were conducted. Also, the attack angles 0
as well as four different length-width ratios of the bridge pier were utilized. The suggested formula were compared with 6 different formulas and the riprap sizes calculated using the equation suggested in this paper indicate the similar patterns with the formula suggested by Richardson. The suggested formula in this paper can be widely applied in the riprap design for the local scour protection around the bridge pier with the consideration of the attack angle to the flow.