• Journal of the Korean Geographical Society
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• v.31 no.3
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• pp.613-629
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• 1996

River terraces of glacial and interglacial periods are most developed in the Ungcheon River, midwestern coastal region of south Korea. Among these terraces, interglacial river terraces correspond to the thalassostatic terraces of eastern coastal region of Korea. Thus the former shoreline altitudes of the coastal region around Ungcheon River can be estimated by using relative heights of these interglacial thalassostatic terraces of Ungcheon River The former shoreline altitudes estimated from interglacial thalassostatic terraces of Ungcheon River are 80m, 50${\sim}$60m, 40${\sim}$45m, 30m, 25m(?), 15${\sim}$20m, and 10m. These estimates are almost identical with those of Quaternary sea levels of eastern coastal region. Among the above estimates of Ungcheon River, the former shoreline altituded of 15~20m and 10m correspond to the ancient sea levels of $\pm$18m and $\pm$10m of eastern coastal region which were injudged as the last interglacial culmination period and late warmer period of the last interglacia(5e and 5a substages of oxygen isotope stage), respectively. Therefore there is a possibility that the rest of the above former shoreline altitudes of the coastal region aroune Jngcheon River also correspond to those of eastern coastal region. On the basis of the above possibility it can be proposed that the eastern and western coastal region of Korean Peninsula have undergone tectonic uplift of equall amount since the middle Quaternary Period.

• Journal of Korea Water Resources Association
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• v.41 no.12
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• pp.1219-1230
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• 2008

Stream inflows induced by flood runoffs have a higher density than the ambient reservoir water because of a lower water temperature and elevated suspended sediment(SS) concentration. As the propagation of density currents that formed by density difference between inflow and ambient water affects reservoir water quality and ecosystem, an understanding of reservoir density current is essential for an optimization of filed monitoring, analysis and forecast of SS and nutrient transport, and their proper management and control. This study was aimed to quantify the characteristics of inflow density current including plunge depth($d_p$) and distance($X_p$), separation depth($d_s$), interflow thickness($h_i$), arrival time to dam($t_a$), reduction ratio(${\beta}$) of SS contained stream inflow for different flood magnitude in Daecheong Reservoir with a validated two-dimensional(2D) numerical model. 10 different flood scenarios corresponding to inflow densimetric Froude number($Fr_i$) range from 0.920 to 9.205 were set up based on the hydrograph obtained from June 13 to July 3, 2004. A fully developed stratification condition was assumed as an initial water temperature profile. Higher $Fr_i$(inertia-to-buoyancy ratio) resulted in a greater $d_p,\;X_p,\;d_s,\;h_i$, and faster propagation of interflow, while the effect of reservoir geometry on these characteristics was significant. The Hebbert equation that estimates $d_p$ assuming steady-state flow condition with triangular cross section substantially over-estimated the $d_p$ because it does not consider the spatial variation of reservoir geometry and water surface changes during flood events. The ${\beta}$ values between inflow and dam sites were decreased as $Fr_i$ increased, but reversed after $Fr_i$>9.0 because of turbulent mixing effect. The results provides a practical and effective prediction measures for reservoir operators to first capture the behavior of turbidity inflow.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.7
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• pp.495-503
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• 2012

The water quality of Gul-po Stream, the subject of this study, has been deteriorating because of the inflow of domestic sewage and the industrial wastewater due to industrialization and the problems relating to the structure of river including slow flow rate and the covering of river. In particular, the domestic sewage from small-medium sized factories by the river and large-scale industrial complex by the upper and middle streams of the river, and the domestic sewage from increasing population due to the regional development are the main pollution sources. Thus, this study aims to survey the water quality and the sediment affecting Gul-po Stream; monitor the state of pollution in water body; assess the yield of sediment and investigate the water quality of river and the problems arising from sediment; and then suggest reasonable ways to improve the situation. The findings from surveying pollution load shows the discharge increases up to average 72.8 times from the upper stream to the downstream of Gul-po Stream, and pollution load increases up to: SS 111 times, BOD 150 times, COD 145 times, the nutrient T-N 222 times and T-P 312 times on an average basis. As for the pollution concentration range, ignition loss is 1.29~12.43%; COD is 4,015~37,547 kg/day; T-N and T-P 94.8~352.5 kg/day and 81.8~372.3 kg/day, respectively. As for the releasing rate of sediment, T-N is -14.46~$156.61mg/m^2/day$; T-P is -11.53~$26.10mg/m^2/day$, indicating the likelihood of internal contamination due to the elution of sediment. This study is expected to be used as basic data to manage Gul-po Stream basin.

• Korean Journal of Agricultural Science
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• v.38 no.1
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• pp.163-172
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• 2011

To provide the operation rule curve for suppling instream flow to urban stream from reservoir, the Soho reservoir with watershed area of 7.4 $km^2$ and total water storage of 2.58 $Mm^3$ was planned at the headwaters of the Daejeoncheon. Daily streamflow was simulated and using the simulated streamflow and desired instream flow, the operation rule curve by Senga method was drawn and evaluated through reservoir operation. Senga method is derived by accumulating the differences between streamflow and desired instream flow adversely. Water storages were simulated on a daily basis to supply urban instream flow from Soho reservoir, but the amount of supplying instream flow to urban stream was not nearly increased comparing with that of normal operation that does not used the rule curve. Thereafter the new simulation-based operation rule curve was derived and applied to supply instream flow from Soho reservoir. In normal operation, the amount of instream flow was shown to 15,000 $m^3$/d, but it was increased to 27,700 $m^3$/d in withdrawal limited operation using the new derived rule curve, in which the applicability of this rule curve was proved. Also comparing with the flow duration curves at station just before urban Daejeoncheon stream without and with upstream Soho reservoir, the 95th flow was decreased from 1.64 mm/d to 1.51 mm/d, and the 355th flow was increased from 0.17 mm/d to 0.30 mm/d. Monthly streamflows during October to March were increased from 10.6~24.1 mm to 24.1~34.0 mm with the increasing rate of 141~227%.

• Journal of the Korean Association of Geographic Information Studies
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• v.9 no.1
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• pp.34-45
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• 2006

In this study comparison estimates travel times with observed travel time. In generally, peak flood discharges decrease become travel times longer. It is closely related to storage constant for the watershed routing of a flood. There are so many empirical formulas available for the estimation of travel time, storage coefficients and lag time but results computed generally show great different depending on individual formulas. When calculated flood discharge depend on the travel times varying the discharge. In this study the Wichun travel time shorter optimization travel time than observed travel time for the rusa and memi. There are showed good results for flood discharges, water level and velocity of the memi at the Younggok.

• Journal of Korea Water Resources Association
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• v.49 no.6
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• pp.529-536
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• 2016

The existing methods to estimate the maximum scour depth in the bend of steep gravel bed channel have been evaluated by the hydraulic movable-bed experiments. In the $90^{\circ}$ bend steep-slope channel paved with the fluvial gravels which are uniform in size and have a mean diameter of 43mm, the maximum scour depths due to the flow discharge and the gradient of bed slope have been investigated and compared with the scour depth computed from the equations. The local scour has occurred in conditions that the bed slope is steeper than 0.02 and the $F_r$ is greater than 0.95. Except Lacey's equation and Zeller's equation, the existing methods computing the maximum scour depth overestimate the maximum scour depth in the steep channel with the very coarse gravel bed. However, Lacey's equation with the bed material size and Zeller's equation considering the approach channel gradient and the bend angle may be relatively used to estimate the scour depth in bend of the steep gravel-bed river.

• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.3
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• pp.1-12
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• 2016

The objective of this study is to analyze the relationship between stream water quality of TN (total nitrogen), TP (total phosphorus), and BOD (Biochemical Oxygen Demand) and TDI (Trophic Diatom Index) score determined by physico-chemical factors, biomass, and standing crops of epilithic diatoms, and to estimate the required amount of ecological streamflow for good water environment of Trophic Diatom. For the main stream of Chungju dam watershed of South Korea, total 100 field data of 3 years (2008~2010) measured in May and September were used to derive the relationship between water quality and TDI. Trophic Diatom had high correlation (0.55 determination coefficient) with TN. Using the relationship, the required streamflow was evaluated by using the Soil Water Assessment Tool (SWAT) for good Trophic Diatom water environment through T-N water quality maintenance. The SWAT simulated 8 years (2003~2010) stream discharges and T-N water quality along the main stream. From present garde C (score range: 30.0~45.0) to grade A (score above 60.0) of TDI, the May needs additional streamflow of $63.1m^3/sec$ (+36.7 % comparing with the present streamflow of $172.0m^3/sec$) at the watershed outlet.

• Journal of Korea Water Resources Association
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• v.41 no.7
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• pp.737-746
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• 2008

The purpose of developing a rainfall-runoff and reservoir model is to provide an analysis tool for hydrological engineers in order to forecast discharge of rivers and to accomplish reservoir operations easily and accurately. In this study, based on the short-term rainfall-runoff storage function model which has gained popularity for real time flood forecast in practical water management affairs, a long-term runoff model was developed for the improvement of the calculation method of effective rainfall and percolation at the infiltration area. Annual discharge was simulated for three dam watersheds(Andong, Hapcheon, Milyang) in Nakdong River basin to analyze the accuracy of the developed model and compare it to SSARR model, which is used as the long-term runoff model in current practical water management affairs. As the result of the comparison of hydrographs, SSARR model showed relatively better results. However, it is possible for the developed model to simulate reliable long-term runoff using relatively little available data and is useful for hydrological engineers in practical affairs.

• Journal of Korea Water Resources Association
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• v.36 no.3 s.134
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• pp.455-464
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• 2003

In this paper, the experiments with installing a rainfall storage tank in the sub-surface were conducted and the reduction rates of the total runoff volume were investigated. The analysis were conducted based upon the variations of the rainfall intensity, surface coverage and surface slope. The reduction rate of the runoff volume was varied from 42.3% to 52.9% with the soil in the bank of the Seung Gi stream. In the experiments, the rainfall intensities were varied from 40mm/hr to 100mm/hr and the results indicate that the direct runoff reduction can be obtained with the installation of the rainfall storage tank in the sub-surface. The variation of the stored volume in the tank is very large in the mild slope but very small in the steep slope with over 3% slope. With this results, the reduction of the direct runoff volume for the longtime flood is expected with the installation of the rainfall storage tank in the region haying the steep slope such as the mountain area.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.4 no.1
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• pp.79-92
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• 1984

The analysis of total load was carried out by using the theory of unit stseam power (USP). The dimensionless USP equation of $S_R$ which was the rate of suspended load and bed load was derived from the USP function by applying the Einstein's reference concentration and Stokes' fall velocity. And the R relationship between the water discharge and Reynolds number (Re) was discussed, and it was shown that USP was closely related with Re. The value of $S_R$ was determined from the experimental data of Han River downstream and Mantz. And it was tested to several observatories of Korean Rivers. A good correlation among USP, suspended load and $S_R$ was shown and USP was increased with the increment of the turbulent intensity. Judging from the above results, it is considered this study can be contributed to estimate the total load.