• Journal of Korea Water Resources Association
• /
• v.49 no.2
• /
• pp.83-94
• /
• 2016

Geomorphological, bed material and hydraulic characteristics are basis informations for the planning, design and management of the river in the aspect of flood control and environmental conservation, and it is very important to use these informations for the design of stable channel. In this study, dominant discharge was selected, geomorphological and hydraulic characteristics were analyzed using that discharge and also the characteristics of bed materials distribution were analyzed and bed materials-flow resistance relationship was evaluated, for the upstream section of Namgang dam. The dominant discharge was estimated a return period of approximately 1.5 year and stream type were classified Segment 1 and Segment 2 in this stream. Also, the frequency of riffle-pool showed 4.4 because this study area has the characteristics of natural channel that have not channel-crossing structures. In dominant discharge, according to the results that analyzed relationship between $h/d_{50}$ and $V/u_*$ to calculate flow resistance by bed materials, Julian's formula showed to appropriate in channel where is relatively close to natural river and is predominantly consisted of gravel, cobble, boulder and rock in mountain, and it was confirmed that the image processing methodology will be easily applied to the analysis of bed materials distribution in future.

• Geomechanics and Engineering
• /
• v.23 no.1
• /
• pp.85-92
• /
• 2020

This study adopted soil test and laboratory physical model experiments to simulate the tailings impoundment accumulation process according to the principle of similarity. Relying on the practical engineering, it analyzed the tailings deposition characteristics on dry beach surface during the damming process, as well as the variation rules of dam saturation line. Results suggested that, the tailings particles gradually became finer along the dry beach surface to inside the impoundment. The particle size suddenly changed at the junction between the deposited beach and the water surface, which displayed an obvious coarsening phenomenon. Besides, the deposited beach exhibited the vertical feature of coarse upward and fine downward on the whole. Additionally, in the physical model, the saturation line elevated with the increase in dam height, and its amplitude was relatively obvious within the range of 1.0-4.5 m away from the initial dam. Under flood condition, the saturation line height was higher than that under normal condition on the whole, with the maximum height difference of 4 cm. This study could provide an important theoretical basis for further studies on dam failure experiments and the evolution rules of leaked tailings flow.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.65 no.5
• /
• pp.25-35
• /
• 2023

The estuary reservoir is a major source of agricultural water in Korea; for effective and sustainable water resource management of the estuary reservoir, it is crucial to comprehensively consider various water resource factors, including water supply, flood, and pollutant management, and analyze future runoff changes in consideration of environmental changes such as climate change. The objective of this study is to estimate the impact of future climate change on the runoff characteristics of an estuary reservoir watershed. Climate data on future Shared Socioeconomic Pathway (SSP) scenarios were derived from two Global Climate Models (GCMs) of the Coupled Model Intercomparison Project phase 6 (CMIP6). The Hydrological Simulation Program-Fortran (HSPF) was used to simulate past and future long-term runoff of the Ganwol estuary reservoir watershed. The findings showed that as the impact of climate change intensified, the average annual runoff in the future period was higher in the order of SSP5, SSP3, SSP1, and SSP2, and the ratio of runoff in July decreased while the ratio of runoff in October increased. Moreover, in terms of river flow regime, the SSP2 scenario was found to be the most advantageous and the SSP3 scenario was the most disadvantageous. The findings of this study can be used as basic data for developing sustainable water resource management plans and can be applied to estuary reservoir models to predict future environmental changes in estuary reservoirs.

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.30 no.3
• /
• pp.58-68
• /
• 1988

Most of the Korean watersheds are mountaineous and consist of various soil types and land uses And seldom watersheds are found to have long term hydrologic records. The SNUA, a hydrologic watershed model was developed to meet the unique characteristics of Korean watershed and simulate the storm hydrographs from a small mountaineous watershed. Also the applicability of the model was tested by comparing the simulated storm hydrographs and the observed from Dochuk watershed, Gwangjugun, Kyunggido The conclusions obtained in this study could be summarized as follows ; 1. The model includes the simulation of interception, evaporation and infiltration for land surface hydrologic cycle on the single storm basis and the flow routing features for both overland and channel systems. 2. Net rainfall is estimated from the continuous computation of water balance at the surface of interception storage accounting for the rainfall intensities and the evaporation losses at each time step. 3. Excess rainfall is calculated by the abstraction of infiltration loss estimated by the Green and Ainpt Model from the net rainfall. 4. A momentum equation in the form of kinematic wave representation is solved by the finite differential method to obtain the runoff rate at the exit of the watershed. 5. The developed SNUA Model is a type of distributed and event model that considers the spatial distribution of the watershed parameters and simulates the hydrograph on a single storm basis. 6. The results of verification test show that the simulated peak flows agree with the observed in the occurence time but have relative enors in the range of 5.4-40.6% in various flow rates and also show that the simulated total runoff have 6.9-32% of relative errors against the observed. 7. To improve the applicability of the model, it was thought that more studies like the application test to the other watersheds of various types or the addition of the other hydrologk components describing subsurface storages are needed.

• Water for future
• /
• v.29 no.6
• /
• pp.167-178
• /
• 1996

The simulation techniques of hydrologic data series have been developed for the purposes of the design of water resources system, the optimization of reservoir operation, and the design of flood control of reservoir, etx. While the stochastic models are usually used in most analysis of water resources fields for the generation of data sequences, the indexed sequential modeling (ISM) method based on generation of a series of overlapping short-term flow sequences directly from the historical record has been used for the data generation in western USA since the early of 1980's. It was reported that the reliable results by ISM were obtained in practical applications. In this study, we generate annual inflow series at a location of Hong Cheon Dam site by using ISM method and first order autoregressive model (AR(1)), and estimate the drought characteristics for the comparison aim between ISM and AR(1).

• Journal of Korea Water Resources Association
• /
• v.45 no.3
• /
• pp.301-316
• /
• 2012

Two models, TANK and SWAT (Soil and Water Assessment Tool) were compared for simulating natural flows in the Paldang Dam upstream areas of the Han River basin in order to understand the limitations of TANK and to review the applicability and capability of SWAT. For comparison, simulation results from the previous research work were used. In the results for the calibrated watersheds (Chungju Dam and Soyanggang Dam), two models provided promising results for forecasting of daily flows with the Nash-Sutcliffe model efficiency of around 0.8. TANK simulated observations during some peak flood seasons better than SWAT, while it showed poor results during dry seasons, especially its simulations did not fall down under a certain value. It can be explained that TANK was calibrated for relatively larger flows than smaller ones. SWAT results showed a relatively good agreement with observed flows except some flood flows, and simulated inflows at the Paldang Dam considering discharges from upper dams coincided with observations with the model efficiency of around 0.9. This accounts for SWAT applicability with higher accuracy in predicting natural flows without dam operation or artificial water uses, and in assessing flow variations before and after dam development. Also, two model results were compared for other watersheds such as Pyeongchang-A, Dalcheon-B, Seomgang-B, Inbuk-A, Hangang-D, and Hongcheon-A to which calibrated TANK parameters were applied. The results were similar to the case of calibrated watersheds, that TANK simulated poor smaller flows except some flood flows and had same problem of keeping on over a certain value in dry seasons. This indicates that TANK application may have fatal uncertainties in estimating low flows used as an important index in water resources planning and management. Therefore, in order to reflect actually complex and complicated physical characteristics of Korean watersheds, and to manage efficiently water resources according to the land use and water use changes with urbanization or climate change in the future, it is necessary to utilize a physically based watershed model like SWAT rather than an existing conceptual lumped model like TANK.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.29 no.6
• /
• pp.279-285
• /
• 2017

In general, the power law and logarithmic profile are commonly used as flow vertical velocity profile model. However, since the parameters of profile vary with characteristics of coastal environment, it is necessary to estimate these values from measured data using regression analysis. In this paper, we estimated the power law exponent (n), friction velocity ($u^*$) and roughness length ($z_0$) of logarithmic profile by analyzing measured tidal current data that are averaged at a interval of 30 min. In the results of analysis, power law exponent (n) was estimated to be about 10.75 during flood and about 9.3 during ebb. Meanwhile, $u^*$ of logarithmic profile was estimated to be about 0.084 m/s, 0.105 m/s during flood and ebb, respectively. Also, $z_0$ was estimated to be 0.004 m and 0.006 m, respectively.

• Korean Journal of Fisheries and Aquatic Sciences
• /
• v.23 no.1
• /
• pp.25-39
• /
• 1990

The distributions of the temperature and salinity in Kamak bay which has two channels and three sea bottom topographic parts were studied by taking the detailed hydrographic data at the ebb and flood during four seasons from May, 1988 to Feb., 1989. The general pattern of the distributions of characteristics which the temperature and salinity has in Kamak bay is basically formed by the topography and sea water movement of the bay. The changes of these distributions by seasons mainly come from the heating and cooling of the sea surface and the increase of the run-off. The bay has three remarkable water masses and the their general characteristics are follows: the inner bay water has a stagnation character influenced by the inland and the concave of the sea bottom in the north west, Yosu harbor water has an estuary character of the low salinity caused by the run-off of Somjin river and Yon Tung brooklet in the north east, and the outer bay water has an out-sea character, as it is located near by the big mouth in the south of the bay. The distributions of those water masses at the ebb and flood show some different features due to the flow patterns, and the daily changes of oceanic conditions at the vicinity of Hangdae-ri are so big that it may influence the habitation and production of the living things in the bay.

• Journal of the Korean association of regional geographers
• /
• v.13 no.4
• /
• pp.409-421
• /
• 2007

The purpose of this paper is to consider the formation processes and depositional conditions of bars formed at the upper-stream part of Sayeon Dam since Sayeon Dam construction in 1964. Results of analyzing the shape characteristics of bars and their sediment grain size distribution are as follow: Firstly, bars are able to categorized as subaqueous bars (A, B), mid-channel bars(C, D), and tributary side-bars(E). Secondly, the outline of bars has longish along the flow path, and their height lowers more and more going towards downstream. Also the height of bar surface tend to heighten from flow path to mountain slope. However, the near part of A is comparatively higher than its distant part, A is defined as a subaqueous natural levee and back swamp. Thirdly, the average particle size of A and B become smaller toward mountain slope. In transportation style, ratio of suspended load become higher toward mountain slope. Fourthly, sorting is worse to very worse according with lake's random changable water level. Fifthly, bar A and B were formed by vertical sedimentation of sediments according as sediments transported along flow path in the subaqueous conditions were spreaded out of flow path. C and D were formed by bed load as flood level lowered. And E was formed by vertical sedimentation while stream flow stopped in tributary's mouth areas with the water level heightening.

• 한국해양학회지
• /
• v.7 no.1
• /
• pp.24-45
• /
• 1972

The Han River is an important water source in Seoul and neighbouring districts, for public and industrial supply, and for agriculture and fishery. Nowadays, more than six million inhabitants are supplied withe water from this river. The total length of the river is 470km, and has 17 10$\^$9/㎥ an average annual flow. The hydrographic characteristics at Seoul are 653㎥/sec in an average flow, 4,608㎥/sec in the maximum average flow, and 201㎥/sec in the minimum average flow. These are influenced in some degree by snowmelt in early spring, and greatly by the flood during summer. For the pollution problems, the periods of low flow are critical ones. As a rule they occur around the months November through June. Nowadays, most of the sewage from towns and industries is discharged untreated. Apart from domestic and industrial sewages, there are some discharges of mineral matter by mines in the upriver region. In general, water quality of the Han River is kept very clean and healthy until Kwangnaru of the upper region of Seoul. A large pollution, however, is received in the downstream by the domestic and industrial sewages of Seoul. It can be seen that dissolved oxygen, COD and BOD$\sub$5/ diminish markedly, and the intensity of almost every water parameter of the river continues to increase. Comparison of the figures for 1971 derived from a sampling point 40km downstream of Kwangnaru leads to the conclusion that hardness, Ca and Mg were no changed; alkalinity, Si and soluble- Fe were slightly increased; CO$\sub$2/, acidity, Cl, NO$\sub$2/-N, Cu, Zn and Al were increased in 2 and 3 times; total residue, total ignitious residue, COD, BOD$\sub$5/, NH$\sub$4/-N, PO$\sub$4/-P, Mn, Pb and total-Fe were increased in 4 to 7 times; and SO$\sub$4/, particulate-Fe and Cd were increased in 10 to 11 times. On the other hand, coliforms were increased in 650 times; fecal coliforms in 365 times; enterococci and total plate counts in 30 times, respectively. In view points of water quality standards, the down Han River water is now leveling out in Cd, coliforms and fecal coliforms for the agricultural use; in dissolved oxygen and some trace elements (Cu, Zn, Pb and Cd) for the fishery use; in ammonia, COD, BOD$\sub$5/, and Cd for the drinking use.