• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.3 s.22
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• pp.69-76
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• 2006

An hydraulic and hydrologic analysis procedure was proposed to reduce the inundation damage of highway in urban stream, that could contribute the EAP and Traffic control planning of Dongbu highway in the Jungrang stream basin which is one of the representative urban area in Korea. We performed the HEC-HMS runoff analysis, and the UNET unsteady flow modeling to decide the inundation reaches and their characteristics. The high inundation risk areas were of Emoon railway bridge and the Wollueng bridge, which are inundated in the case of 10 year and 20 year frequency flood respectively. We also analyze the inundation characteristics under the various conditions of the accumulation rainfall and the duration. Flood elevation at the Wolgye-1 bridge exceed over Risk Flood Water Level(EL.17.84 m) when the accumulation rainfall is over 250 mm and shorter duration than 7 hr. When neglecting backwater effect from the Han river, inundation risk are highly at the reach C2(Wolgye-1 br. ${\sim}$Jungrang br., left bank), C1(Wolgye-1 br. ${\sim}$Jungrang br., right bank), D(Jungrang br. ${\sim}$Gunja br.) in order, but when consider the effect, the inundation risk are higher than the others at the reach D2(Jungrang br. ${\sim}$Gunja br., left bank) and E(Gunja br. ${\sim}$Yongbi br.), which are located downstream near confluence.

• Proceedings of the Korea Water Resources Association Conference
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• 2011.05a
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• pp.15-15
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• 2011

The radar observation system in Japan is operated by two governmental groups: Japan Meteorological Agency (JMA) and the Ministry of Land, Infrastructure, Transport and Tourism (MLIT) of Japan. The JMA radar observation network is comprised of 20 C-band radars (with a wavelength of 5.6 cm), which cover most of the Japan Islands and observe rainfall intensity and distribution. And the MLIT's radar observation system is composed of 26 C-band radars throughout Japan. The observed radar echo from each radar unit is first modified, and then sent to the National Bureau of Synthesis Process within the MLIT. Through several steps for homogenizing observation accuracy, including distance and elevation correction, synthesized rainfall intensity maps for the entire nation of Japan are generated every 5 minutes. The MLIT has recently launched a new radar observation network system designed for flash flood observation and forecasting in small river basins within urban areas. It is called the X-band multi parameter radar network, and is distinguished by its dual polarimetric wave pulses of short length (3cm). Attenuation problems resulting from the short wave length of radar echo are strengthened by polarimetric wavelengths and very dense radar networks. Currently, the network is established within four areas. Each area is observed using 3-4 X-band radars with very fine resolution in spatial (250 m) and temporal (1 minute intervals). This study provides a series of utilization procedures for the new input data into a real-time forecasting system. First of all, the accuracy of the X-band radar observation was determined by comparing its results with the rainfall intensities as observed by ground gauge stations. It was also compared with conventional C-band radar observation. The rainfall information from the new radar network was then provided to a distributed hydrologic model to simulate river discharges. The simulated river discharges were evaluated again using the observed river discharge to estimate the applicability of the new observation network in the context of operations regarding flood forecasting. It was able to determine that the newly equipped X-band polarimetric radar network shows somewhat improved observation accuracy compared to conventional C-band radar observation. However, it has a tendency to underestimate the rainfall, and the accuracy is not always superior to that of the C-band radar. The accuracy evaluation of the X-band radar observation in this study was conducted using only limited rainfall events, and more cases should be examined for developing a broader understanding of the general behavior of the X-band radar and for improving observation accuracy.

• Journal of Korea Water Resources Association
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• v.55 no.2
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• pp.135-145
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• 2022

This study aims to verify the Drone utilization and the accuracy of the global navigation satellite system (GNSS), Drone RGB (Photogrammetry) (D-RGB), and Drone LiDAR (D-LiDAR) surveying performance in the downstream reaches of the local stream. The results of the measurement of Ground Control Point (GCP) and Check Point (CP) coordinates confirmed the excellence. This study was carried out by comparing GNSS, D-RGB, and D-LiDAR with the values which the hydraulic characteristics calculated using HEC-RAS model. The accuracy of three survey methods was compared in the area of the study which is the ownership station, to 6 GCP and 3 CP were installed. The comparison results showed that the D-LiDAR survey was excellent. The 100-year frequency design flood discharge was applied in the channel sections of the small stream. As a result of D-RGB surveying 2.30 m and D-LiDAR 1.80 m in the average bed elevation, and D-RGB surveying 4.73 m and D-LiDAR 4.25 m in the average flood condition. It is recommended that the performance of D-LiDAR surveying is efficient method and useful as the surveying technique of the geospatial information using the drone equipment in stream channel.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.10
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• pp.509-516
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• 2020

Since the 1960s, many rivers have been polluted and destroyed due to river repair projects for economic development and the covering of small rivers due to urbanization. Many studies have analyzed rivers using measured river topographic factors, but surveying is not easy when the flow rate changes rapidly, such as during a flood. In addition, the previous research has been mainly about the cross section of a river, so information on the longitudinal profile is insufficient. This research used informational entropy theory to obtain an equation that can calculate the average river slope, river slope, and river longitudinal elevation for a river basin in real time. The applicability was analyzed through comparison with measured data of a river's characteristic factors obtained from a river plan. The parameters were calculated using informational entropy theory, nonlinear regression analysis, and actual data. The longitudinal elevation entropy equation for each stream was then calculated, and so was the average river slope. All of the values were over 0.96, so it seems that reliable results can be obtained when calculating river characteristic factors.

• Journal of Environmental Impact Assessment
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• v.20 no.6
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• pp.797-813
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• 2011

Frequently occurring flood and drought due to abnormal climate and global warming have increased the necessity of an effective water resources control and management of river flows. The various hydraulic structures are constructed in river as part of an effective water resources management. It is very important to analyse characteristics of flow according to installing hydraulic structures in this situations. The objective of this study is to investigate the hydraulic behaviors of flow considering affections of hydraulic structures using 2-D numerical model. To do this, both RMA-2 model and developed RAM2 model are used to analyse flow phenomena before and after installation of hydraulic structures in Nakdong river. As a result of, the water surface elevation at upstream regions increased about 22cm~66cm and the velocity around the structures sharply increased after installation of structures. The measures for the rise of water surface at upstream and local scour due to high velocity around the structures must be established when the structures is constructed.

• Journal of Industrial Technology
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• v.25 no.B
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• pp.19-25
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• 2005

To use land more efficiently under urbanization trend, Kangwon Province often covers open channels of creeks and uses them as parking lots or roads. A covered open channel section tends to form a rectangular culvert. Therefore, a creek with covered open channels can function as a storm drain. At the time of light rainfall, there are no significant differences except water flowing pattern between a creek with a covered open channel and a creek without it. Recently, however, the frequent occurrence of heavy rainfalls limited at a small, definite area has become problematic. When the heavy rainfall causes the carrying capacity of a creek to be exceeded,the creek with covered open channel has a more serious problem than the creek without it has. Therefore, we made an interpretation of data and conducted hydraulic model experiment to come up with economical solution to this problem.

• Water for future
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• v.26 no.4
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• pp.35-46
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• 1993

The variations of water surface elevation due to bridge are studied using one_dimensional dynamic wave equation. The preissmann scheme is used to solve the dynamic wave equation and the bridges was treated as internal boundary conditions. Main causes of bridge backwater are the proportion of the contracted area due to bridge, roughness coefficient and discharge coefficient. The effect of discharge coefficient in weir flow condition is comparatively small. This model is verified by applying to the Suyoung River. which suffered a severe damage by typoon Gladys. The rise of water level through bridge is 1.53-1.08m in the reach of 4.25-6.20km from the downstream of river. The simulation results of the model have good agreements with the observed data.

• Proceedings of the Korea Water Resources Association Conference
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• 2008.05a
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• pp.624-628
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• 2008

Two-dimensional flow analysis is a way to provide good estimates for complex flow features in flow around islands and obstructions, flow at confluence and flow in braided channel. One of difficult problems to develop a two-dimensional hydraulic model is to analyze dry and wet area in river channel. Dry/wet problem can be encountered in river and coastal engineering problems, such as flood propagation, dam break analysis, tidal processes and so on. The objective of this study is to develop an accurate and robust two-dimensional finite element method with dry/wet technique in complex natural rivers. The dry/wet technique with Deforming Grid Method was developed in this study. The Deforming Grid Method was used to construct new mesh by eliminating of dry nodes and elements. The eliminated nodes and elements were decided by considering of the rising/descending velocity of water surface elevation. Several numerical simulations were carried out to examine the performance of the Deforming Grid Method for the purpose of validation and verification of the model in rectangular and trapezoidal channel with partly dry side. The application results of the model were displayed reasonable flow distribution.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.28 no.5
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• pp.607-623
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• 1995

A numerical model of hydraulic resistance by hanging aquaculture facilities is developed and applied to a model basin and a field. A drag stress term formulated by the quadratic law of drag force is introduced Tn the equations of motion for a two-dimensional depth-averaged flow. In the model basin, numerical experiments ave tarried out for the various shape of obstructions, string density and layout of facilities etc.. The flow pattern around the facilities is affected sensitively by the density of string and the layout of facilities. On the other hand, the velocity decay due to the hanging oyster aquaculture facilities is observed in Kamak bay, where the maximum velcocity decay rate is $25\%$ in spring tide. The model is also applied to the field, Kamak bay. The velocity decay rate in the model is comparable with the field measurement data. The velocity decreases around the down-stream area of the facilities, .hut it increases in the other region. The water elevation decreases during the flood and it increases during the ebb.

• International Journal of Ocean System Engineering
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• v.2 no.1
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• pp.37-49
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• 2012

An analysis of potential flooding by storm surge and wave run-up and overtopping can be used to evaluate protection afforded by the existing storm protection system. The analysis procedure can also be used to evaluate various protection alternatives for providing typhoon flood protection. To determine risk, the storm surges for both historical and hypothetical are compiled with tide conditions to represent high, slack and low water for neap, spring and mid range tides to use with the statistical procedure known as the Empirical Simulations Technique (EST). The EST uses the historic and hypothetical events to generate a large population of life-cycle databases that are used to compute mean value maximum storm surge elevation frequency relationships. The frequency-of-occurrence relationship is determined for all relevant locations along the shoreline at appropriate locations to identify the effect using the Empirical Storm Simulation (EST). To assist with understanding the process, an example is presented for a study of storm surge analysis for Freeport, Texas. This location is in the Gulf of Mexico and is subject to hurricanes and other tropical storms that approach from the Atlantic Ocean.