• Journal of Environmental Science International
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• v.17 no.9
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• pp.957-968
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• 2008

The purpose of this study is to analyze the characteristics of hydraulic behavior of the natural channel flow according to the temporal classification mode, and thus propose the hydraulic analysis method for future channel design. For analysis, the temporal flow characteristics of the channel section was divided into the steady flow and the unsteady flow. For hydraulic analysis, the HEC-RAS model, which is a one-dimensional numerical analysis model, and the SMS-RAM2 model, which is a two-dimensional model, were used and the factors used for analysis of hydraulic characteristics were flood elevation and flow rate. The flow state was analyzed on the basis of the one-dimensional steady flow and unsteady flow for review. In the unsteady flow analysis the flow rate changed by $(-)0.16%{\sim}(+)0.26%$, and the flood elevation varied by $(-)0.35%{\sim}(+)0.51%$ as compared to the values in the steady flow analysis. Given these results, in the one-dimensional flow analysis based on the unsteady flow the flood elevation and flow rate were greater than when the analysis was done on the basis of the steady flow. The flow state was analyzed on the basis of the two-dimensional steady flow and unsteady flow. In the unsteady flow analysis the flow rate varied by $(-)0.16%{\sim}(+)1.08%$, and the flood elevation changed by $(-)0.24%{\sim}(+)0.41%$ as compared to the values in the steady flow analysis. Given these analysis results, in the two dimensional flow analysis based on the unsteady flow, the flood elevation and flow rate were greater than when the analysis was done on the basis of the steady flow.

• Magazine of the Korean Society of Agricultural Engineers
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• v.32 no.4
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• pp.81-88
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• 1990

The flow in a river reach where is influenced by tidal motion is characterized by unsteady flow. The flood analysis in the river reach needs depending upon the theory based on the complete unsteady flow equations. In this study the unsteady flow model which is called CRIUM (Channel Routing by Implicit Unsteady Flow Model) was developed and was applied to the Mankyong and Dongjin river in order to analyze the flood characteristics. The results, which were calibrated and verified by the flood records to be measured in the two rivers, show that unsteady flow mode] can be used for the derivation of the flood hydrograph. The peak flood discharges were estimated as 4,960 and $2,870m^3$/sec in 100 year frequency at the estuary of the Mankyong and Dongjin river, respectively. In addition, it was analyzed that the river reaches were not influenced by tidal motion when the discharge magnitude was larger than approximately $3,000m^3$/sec.

• 한국방재학회:학술대회논문집
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• 2007.02a
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• pp.599-602
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• 2007

Flood damage has been increased due to abnormal climate and extreme rainfall. Especially, the increase of impervious areas and the decrease of flow travel times due to the urbanization have been caused heavy division of flood with the recent rainfall characteristics. In this study, hydrodynamics flow analysis has been needed two dimensional numerical analysis for correct stream flow interpretations on bridges as hydraulic structures in rivers. Therefore, comparative analysis has been accomplished by using HEC-RAS model and SMS-RMA2 model for one and two dimensional flow. Also, flood characteristics have been analyzed in urban stream basin.

• Journal of Environmental Science International
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• v.33 no.7
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• pp.463-476
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• 2024

This study examined the effects of riverbed slope and roughness coefficient on flood level and flow velocity. A numerical experiment was conducted by installing HEC-RAS in the valley of a sub-basin in Geochang-gun, Gyeongsangnam-do. For each basin, three slopes of riverbeds (slopes-15.0%, 5.0%, and 1.0%) were chosen with different characteristics, and four coefficients of roughness were applied to each slope to parameterize the flow. Flow velocity and flood level were intensively investigated. It was found that in the cases of 15.0% and 5.0%, where the riverbed slopes are steep, the slope dominates the change in flow velocity and flood level, while in the case of 1%, where the riverbed slope is small, the change in flow velocity and flood level caused by changes in roughness coefficient is insignificant. Usually, the riverbed slope is large in the valley part of the watershed, so in this case, the slope will play a dominant role in the results of flow velocity and flood level when designing water-related structures.

• Journal of Korea Water Resources Association
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• v.45 no.11
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• pp.1107-1119
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• 2012

The objectives of this study are to develop the flow nomograph for real-time flood forecasting and to assess its applicability in restored Cheonggye stream. The Cheonggye stream basin has the high impermeability and short concentration time and complicated hydrological characteristics. Therefore, the flood prediction method using runoff model is ineffective due to the limit of forecast. Flow nomograph which is able to forecast flood only with rainfall information. To set the forecast criteria of flow nomograph at selected flood forecast points and calculated criterion flood water level for each point, and in order to reflect various flood events set up simulated rainfall scenario and calculated rainfall intensity and rainfall duration time for each condition of rainfall. Besides, using a rating curve, determined scope of flood discharge following criterion flood water level and using SWMM model calculated flood discharge for each forecasting point. Using rainfall information following rainfall scenario calculated above and flood discharge following criterion flood water level developed flow nomograph and evaluated it by applying it to real flood event. As a result of performing this study, the applicability of flow nomograph to the basin of Cheonggye stream appeared to be high. In the future, it is reckoned to have high applicability as a method of prediction of flood of urban stream basin like Cheonggye stream.

• 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 Environmental Science International
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• v.11 no.3
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• pp.191-199
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• 2002

In this study, water protection reservoir is selected as the target which is located at the estuary of Taehwa river to analyze and examine the effects of hydraulic structure on river environment. This study aims at the definition of factors which cause the change of ecological environment of river due to the effects of the sediment protection reservoir, and the proposal of the direction of environmental friendly river space development through the analysis and examination of stream variation conditions and riverbed variation characteristics among many effects of hydraulic structure on river environment before and after removal of the sediment protection reservoir when design flow is yielded. Firstly, in case of removal the existing sediment protection reservoir, the hydraulic variation characteristics like depth drop due to removal of the sediment protection reservoir are thought of little because it is examined that depths drop with about 0.01m and 0.01~0.56m when low flow is yielded and design flood yielded, respectively. Nextly, as the examination result of the variation characteristics of flow velocity in case of removal the existing sediment protection reservoir, it is thought that the concern about riverbed erosion is not serious according to the analyzed result as the mean velocity of the channel section where the velocity varies in case of removal the sediment protection reservoir is about 0.07~1.36m/s when low flow is yielded, and is about 1.02~2.41m/s when design flood is yielded despite riverbed erosion is concerned as it is examined that flow velocity is getting increase as about 0.01m/s when low flow is yielded and about 0.01~0.44m/s when design flood is yielded. Lastly, from the prediction result of riverbed variation for each flow amount condition before and after removal the sediment protection reservoir, it is known that the variation range of riverbed is nearly constant when flow amount of the channel exceeds a specific limit as it is analyzed that the more flow amount, the more erosion and sediment in the channel section of down stream part of the sediment protection reservoir and the sediment protection reservoir~Samho-gyo, and the variation ranges according to flow amount between flood condition and design flood condition have little difference in the channel section of the upstream of Samho-gyo.

• Journal of Korea Water Resources Association
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• v.40 no.4
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• pp.313-324
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• 2007

An irregular cell-based numerical model was developed to analyze underground space flooding. In this model, the flow characteristics in underground space were computed by link-node system. Also, the model can simulate the underground flood flow related to the influence of stairs and wall-structures. Empirical discharge formula were introduced to analyze weir-type flow for shopping mall, and channel-type flow for subway railroad respectively. The simulated results matched in reasonable range compared with the observed depth. The dual-drainage inundation analysis model and the underground space flood analysis model were integrated using visual basic application of ArcGIS system. The developed model can help the decision support system of flood control authority for redesigning and constructing flood prevention structures and making the potential inundation zone, and establishing flood-mitigation measures.

• Water for future
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• v.22 no.1
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• pp.99-107
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• 1989

KEUM River downstream has some characteristics in which the dowunstream is affected with tidal motion, the several tributaries are forming a dendritic river system, and the channel cross-sections are irregular. The flood in this downstream can now be analyzed by the hydrological flood routing methods and under the assumption regarding the dendritic river system as a single reach. In this study the river system was used for the flood routing. The flood records which were measured in 1978 and 1987 were applied for calibration and verification of the unsteady flow model respectively. The results show that the flood at KANG-KYONG station was not affected with the tidal motion when the discharge at KONG-JU station exceeded about 5, 000$m^3$/sec, and that the bottle neck at IP-PO station intercepted the tidal influences.

• Journal of Industrial Technology
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• v.19
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• pp.369-377
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• 1999

The determination of the design flood based on probabilistic concepts is one of the important matters of the general field of hydrology. Until now, Most of any existing formulas to predict the flood flow were estimated by very different values with each other when we applied these formulas to the small basin, in extreme case, which were estimated over top be 400% of a difference because these have been developed by foreigners or derived from the big basin. The objective of this thesis is to examine closely the characteristics of frequency flood flow for reliable prediction of the flood flow through the probabilistic method in hydrology and to develop the ($Q_T=27.74T^{0.178}A^{0.594}$) applicable to the river of Kangwon province.