• Journal of The Korean Society of Agricultural Engineers
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• v.56 no.2
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• pp.1-9
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• 2014

A modeling system is constructed by integrating an one-dimensional unsteady flow simulation model and a hydrologic model to simulate flood flows in drainage channel networks of paddy field districts. The modeling system's applicability is validated by simulating flood discharges from a paddy field district, which consists of nine paddy fields and one drainage channel. The simulation results are in good agreement with the observed. Particularly, in the verification stage, the relative errors of peak flows and peak depths between the observed and simulated hydrographs range 8.96 to 10.26 % and -10.26 to 2.97 %, respectively. The modeling system's capability is compared with that of a water balance equation-based model; it is revealed that the modeling system's accuracy is superior to the other model. In addition, the simulations of flood discharges from large-sized paddy fields through drainage channels show that the flood discharge patterns are affected by drainage outlet management for paddy fields and physical characteristics of the drainage channels. Finally, it is concluded that to efficiently design drainage channel networks, it is necessary to analyze the results from simulating flood discharges of the drainage channel networks according to their physical characteristics and connectivities.

• Journal of Korea Water Resources Association
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• v.34 no.5
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• pp.543-549
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• 2001

This research estimated stream discharges indirectly by hydraulic channel routing. Only stage data from three stage stations and river cross section data were used to estimate Manning roughness coefficients and to compute stream discharges. When the discharges were estimated a stage-stage set of conditions was used for upstream-downstream boundary conditions. The research used the data from the upper Mississippi River. The hydraulic channel routings were performed by DWOPER (operational dynamic wave model). The global optimization program of SCE-UA was used to improve the roughness coefficient estimation module of the modified Newton-Raphson method in DWOPER. The results from SCE-US were better. For the case study of a flood, most estimated discharges except a few show errors within 10%.

• Journal of Korea Water Resources Association
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• v.36 no.5
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• pp.823-838
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• 2003

For many rivers and streams, it has been observed that a single representative discharge may be used to determine the hydraulic geometry of a stable channel. This representative channel forming discharge has been given several names by different researchers, including bankfull, specified recurrence interval, and effective discharge. Therefore, The purpose of this study is to estimate channel forming discharge for study areas using the hydrological characteristic parameters and recording data, and to determine the hydraulic geometry relationships for the relating bankfull dimensions to bankfull discharge. In the Munmak and Seomyun gauging stations, the estimated bankfull discharges are found to have a return period of 1.8 and 1.5 years on the maximum annual series, respectively. The estimated effective discharges at those stations are largely different from bankfull discharges. The hydraulic geometry relationships between bankfull discharge and bankfull width, bankfull depth, velocity, bed slope are established. But the statistical parameters, such as R2, are calculated lower.

• Proceedings of the Korean Society of Coastal and Ocean Engineers Conference
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• 2002.08a
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• pp.191-197
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• 2002

The prediction of the dynamic behaviors of buoyant water discharges into a large volume of water bodies, the flows of water accompanying the density differences due to temperature differences and sometimes also to salinity differences, have attracted great concern over several decades. Heated water surface discharges from power plants and freshwater discharges in estuaries are typical examples of the buoyant flows. (omitted)

• Journal of Korea Water Resources Association
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• v.39 no.6 s.167
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• pp.487-494
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• 2006

The flood discharge on the rising limb of a hydrograph at Hwawon station greatly differs from the flood discharge on the falling limb for the same stage. When there is such a big hysteresis, there can be a significant amount of errors in the rated discharge obtained from a simple rating curve. To reduce errors in rated discharges, a looped rating curve was established for Hwawon station in the Nakdong River. In order to compute the deviation between real discharges and simply rated discharges, a simple rating curve was established using the stage and discharge data from the results of a hydraulic channel routing. The relationship between the discharge deviation ${\Delta}Q$ and a product of B and ${\Delta}h/{\Delta}t$ was analysed, where B is the channel topwidth; ${\Delta}h$ is the stage increment; At is the time increment. Strong relation between ${\Delta}Q$ and $B{\Delta}h/{\Delta}t$ was found. The discharges calculated from the relationship show differences by 10 % or less for the 7 observations out of 11 observations in 1997 whose stages exceeds 7 m. The observed discharges for the stages over 9 m in 1998 also show small difference with the discharges estimated from the loop rating curve. Looped rating curve is recommended, instead of the simple rating curve to reduce the errors of rated discharges for gauging stations like Hwawon, which has relatively large loop width.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4B
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• pp.361-367
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• 2011

The channel-forming discharge, which is a standard and single flow for the river maintenance and restoration project, should be estimated necessarily in the stable channel design. It is difficult to produce the specific pattern for the channel-forming discharge in the domestic rivers due to the insufficient researches and case studies. Also, it is improper to adopt the foreign cases for the domestic rivers and streams which have the high coefficients of river regime. Therefore, the channel-forming discharge possible to use for rivers with high coefficients of river regime is suggested in this study through analyzing the bankfull, specified recurrence interval, and effective discharges of Mangyeong River, Cheongmi Stream, and Hampyeong Stream for the abandoned channel restoration project. The bankfull discharge was calculated with geometric data using the HEC-RAS modeling and the flow, bed materials, and sediment data for the study reaches were used to estimate the specified recurrence interval and effective discharges. As a result for calculating the channel-forming discharge, the effective discharge was greater than the bankfull discharge in the river with high coefficient of river regime and the effective discharge was greater than the bankfull and there was no correlation between the coefficient of river regime and the characteristics of the specified recurrence interval discharges.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.1B
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• pp.63-70
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• 2011

To install the side weirs in inlet of washland construction, it is necessary to calculate more accurately the discharges over side weir. In this study, the hydraulic experiments were performed in broad crested side weirs that installed trapezoidal channel and that considered more applicable to the actual river. Upstream Froude number in the main channel and weir height, length, width and slope of main channel were considerd for estimation of discharge coefficient of broad crested side weir. Experimental results show that the discharge coefficient of broad crested side weir depend on, and. New estimated equation for the discharge coefficient are suggested through the multiple regression analysis and its applicability is confirmed by comparing estimated and measured discharges over side weirs.

• Journal of Environmental Science International
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• v.25 no.4
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• pp.491-504
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• 2016

This study, examines the flow characteristics of upstream channel depending on water gate operation of Nakdan Multi-fuctional weir. The specific purpose of this study are to simulate the variation of flow velocity depending on the operation of the weir using 1-dimensional hydraulic model, HEC-RAS, and compare it with observed velocity. For discharge conditions from $50m^3/s$ to $3,500m^3/s$, it is observed that the velocity of upstream channel is almost constant, whereas for probability flood discharge, the velocity and froude number are increased as the discharge values are increased. The velocity values for downstream boundary condition EL, 40.0 m are more decreased than those for EL. 40.5m. From comparison on the variation of water stage depending on water gate operation, it is observed that the stage values are almost constant for discharges below $300m^3/s$, whereas 5 cm to 20 cm for discharges over $700m^3/s$. Flow velocity at streamflow gauging station. Nakdong, is decreased by more than 875% after installing the weir. The results obtained from this study indicate that the velocity of upstream channel is decreased and the discharge and velocity of downstream channel are significantly varied after installing the weir.

• Korean Journal of Ecology and Environment
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• v.43 no.2
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• pp.183-189
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• 2010

In this study long term rainfall-runoff model, developed based on SSARR, was applied to Geum river basin and its simulation results of major control points were compared with the corresponding observed channel discharges. The validities of the simulation results were examined with re-measured discharges of those control points. From the above procedure the points showing the unreliable results were found out and its principal causes are analyzed through hydrological inspection of runoff characteristics of their circumstances. Finally the simulation results were modified by the consideration of the effects by small-scale hydraulic structures which could directly affect the channel discharges. As a result the annual runoff simulations of two major points in Geum river basin, Yongdam and Daecheong dam sites, work well. However the low flow simulation of the point located between them, Sutong station, showed more or less the unreliable result. Its causes are considered by means of the hydraulic/hydrological inspection of the corresponding point.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.23 no.1
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• pp.101-108
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• 2011

The purpose of salinity intrusion due to numerical simulation is analaysis for saline intrusion to the upstream channel in Nakdong River Estuary Barrage(NREB) to get enough fresh water. Conditions that occur salinity intrusion affect by tidal distribution at seas, so salinity concentration changes according to tidal phenomenon. Making this connection cleary can help preventing salinity intrusion. In this study, estimating salinity intrusion to the upstream channel in NREB using EOMSED model, we reexamine NREB's existence. Comparison is also made with observing data. In result, when inflow discharges at $75m^3/s$ is more similar with respect to observing data than $130m^3/s$ at ECOMSED model. Thus, estimations are more precise at little discharges than lots of discharges.