• The Journal of the Korea Contents Association
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• v.7 no.11
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• pp.232-238
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• 2007

In this research, we constructed a 3D riverbed surveying system that is able to acquire the topographical information of a riverbed in real-time. The system consists of a RTK-GPS receiver and a echo sounder for collecting simultaneously the position and the water depth information of riverbed. A program for data composition and transformation was designed to generate the 3D coordinates by combining data of a GPS receiver and a echo sounder and made GIS database construction easy. We extracted TIN, digital elevation model and cross sectional maps of the riverbed by using GIS software from 3D data constructed through test surveying. It was shown that the accuracy of the result was RMS error of 0.069m when compared with the existing methods which use a total station and staffs. It is expected that the 3D riverbed surveying system wiil be able to be utilized to various surveying for water resources management in rivers, sea, dams, storing reservoirs and so forth.

• 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.56 no.12
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• pp.837-844
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• 2023

Small and medium-sized mountain rivers that flow through steep, confined valleys carry large amounts of coarse-grained sediment and woody debris during floods. It causes an increase in flood water level by aggrading the riverbed and the cross-section blockage due to driftwood accumulation during flooding. However, the existing flood level calculation in the river basic plan does not consider these changes. In this study, using the Typhoon Hinnamnor flood in September 2022 as an example, we performed numerical simulations using the HEC-RAS model, taking into account the blockage of a cross-section at the bridge and changes in riverbed elevation that occurred during floods, and analyzed the flood level to predict flood risk. This study's results show that flooding occurs if more than 30% of the cross-section is blocked. The rise of flood water levels corresponds to that of the riverbed due to sediment deposition. These results can be used as basic data to prevent and effectively manage flood damage and contribute to establishing flood defense measures that consider actual phenomena.

• Journal of the Korean Society of Hazard Mitigation
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• v.8 no.2
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• pp.119-127
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• 2008

The flow characteristics and the aspects of riverbed changes were analyzed for the upstream and downstream sections of Gongju Bridge. The upstream and downstream had complex topography, and the sections had the confluence of tributaries and several structures. In order to simulate the flow characteristics of the target sections, 1D HEC-RAS and 2D RMA2 were applied. As a result, the longitudinal water level of the target sections matched the results of simulated 1D and 2D samples. Also, 2D SED2D were applied to predict riverbed changes. As a result of the simulation, quantitative analysis was able to be performed for longitudinal riverbed changes from the sections of sudden change, bridges, the confluence of tributaries, and bends. Also, the distribution of riverbed changes on the main sections was in close relation to flow velocity. As a result of evaluating the sensitivity of SED2D, the concentration of suspended sediment, the thickness of sand beds, and the size of sand grains affected riverbed changes sensitively. These results will be used to apply the models of riverbed changes in the future.

• Journal of Environmental Science International
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• v.6 no.5
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• pp.513-520
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• 1997

This study was performed to investigate the riverbed structure and the pollution type in Nakdong River, Western Nakdong River. and Suyoung Stream. Sediment and water samples were collected at is in Nakdong River. in Western Nakdong River, and 8 states In Suyoung Stream from February 20, 1997 to June 15, 1997. The depth distributions of sampling sites in the three streams were measured and heavy metals(Cd, Pb, Cr, Cu) and pesticides in sediments and COD, BOD, and total nitrogen(T-N) in water samples were analysed. The deepest and the shallowest sites were strate 11(11.58m) and 9(3.35m) in Nakdong River, site 7(6.25m) and 4(2.06m) in Western Nakdong River, and site 8(2.89m) and 1(0. 61m) in Suyoung Stream , respectively. The mean concentration of Cd(45.79ppm) was higher In the sediment of Western Nakdong River than In other two streams and those of Pb(76.25ppm), Cr(48.13ppm), and Cu(77.50ppm) were higher in file sediment of Suyoung Stream than in other two streams. Pesticides(1 kind of organophosphorus and 3 kinds of organochlorine pesticide) were detected only in the sediment of Western Nakdong River. The mean concentrations of COD(20.26ppm), BOD(25.36ppm), and T-N(18.05ppm) were higher in the water sample of Suyoung Stream than In other two streams.

• Journal of Korean Society on Water Environment
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• v.22 no.5
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• pp.838-845
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• 2006

Characterization of sediment in the riverbed is of importance for effective water quality management, yet have not been monitored sufficiently. This paper reports monitoring results of nutrient concentrations of sediments. Surface waters and sediments were sampled four times during rainy season at five monitoring points. Organics of overlying water were increased after high flow condition followed by decreasing tendencies. Soluble phosphorus fraction among total phosphorus was increased after high flow condition while total phosphorus was in decreasing tendencies. Monitoring result suggested that more extended monitoring scheme for flow rate, scouring velocity, and suspended material is required for analyzing relationship between water quality and sediment.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.09b
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• pp.1451-1452
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• 2005

• Journal of the Korean Geophysical Society
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• v.9 no.2
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• pp.105-112
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• 2006

We intend to increase in eficiency of the topographic monitoring of seabed or riverbed by combinedwith DGPS, RTK GPS and echo sounder. For this study, we defined the error corection of the echo sounder with the experiment of water tank, which is considered the characteristic of estuary riverbedand then we developed the s/w for 3-dimensional monitoring of estuary riverbed and aplied the s/wto field test and improved the various problems. On analyzing topography of estuary riverbed by combinedby the movement of survey vessel to the end of the transducer was eliminated by geometrical rearangementand we defined the corection formula, . The sounding error about the echo sounder and characteristic of estuary riverbed was found by understanding the relation of average diameter and residual error and we defined corection formula, Y=-0.0474*ln(X) -0.045 by the regression analysis. and then we verified applicability of corection formula. This study that by Visual Basic must be useful applied in the topographic analysis of the estuary riverbed.

• Journal of Korean Society for Geospatial Information Science
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• v.11 no.3 s.26
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• pp.23-34
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• 2003

Currently, the efficiency of GPS has been increased in the various precise survey like as the control survey and the navigation etc. Also, it is widely used in the deformation analysis of the structure, the measurement of the marine tides, the measurement of the river level and the topographic monitoring of seabed or riverbed by combined the measurement equipment for depth. In this study, we intend to increase in efficiency of the topographic monitoring of seabed or riverbed by combined with DGPS, RTK GPS and echo sounder. For this study, we defined the error correction of the echo sounder with the experiment of water tank which is considered the characteristic of estuary riverbed and then we developed the s/w for 3-dimensional monitoring of estuary riverbed and applied the s/w to field test and improved the various problems. On analyzing topography of estuary riverbed by combined GPS with echo sounder, the draught error which is yielded to change of length from the water surface by the movement of survey vessel to the end of the transducer was eliminated by geometrical rearrangement and we defined the correction formula $z=BM+SAH-DBR_{(i)}-DRT-ED$. The sounding error about the echo sounder and characteristic of estuary riverbed was found by understanding the relation of average diameter ind residual error and we defined correction formula, $Y=0.00474{\ast}ln(X)-0.0045$ by the regression analysis. and then we verified applicability of correction formula.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.12 no.2
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• pp.101-108
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• 1992

A careful re-examination has been conducted on the applicability of the concept of equilibrium riverbed slope to river engineering practice and on the validity of Aki's and Mononobe's formulas that are widely used in Korea for determination of equilibrium riverbed slope. A stream in equilibrium is one in which, over a period of years, slope is naturally adjusted to provide, with available water discharge and with prevailing channel characteristics, just the velocity required for transportation of the sediment load supplied from the upstream. The equilibrium riverbed slope is the bed slope of such river. The present river engineering practice to analyze the riverbed characteristics by applying so called 'the equilibrium riverbed slope formula' to such rivers, therefore, should be avoided. Also, the validities of Aki's and Mononobe's formulas, that are presently used for determination of stable channel slope, are very dubious and should not be used in river engineering practice.