• The Korean Journal of Quaternary Research
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• v.3 no.1
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• pp.87-101
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• 1989

The development of the Hantan river basin can be divided into three stages. The first stage include the ancient Hantan channel system prior to the Chongokni basalt which yield dates of about 0.6 mya from the K/Ar dating method. During this period the Baekuyri formation was formed. The Baekuyri formation is widely observed under the Chongokni basalt along the current river system. The second stage is the period when stream channels stayed on the top of the basalt plateau. Aggradation and deggradation were continued by meandering and braiding channel systems until major stream channel was formed. The currently remaining deposit on the top of the basalt was formed by lacustrine and fluvial systems in this period. During this period Pleistocene hominid was present on edge of water and flood plain and left Paleolithic material. This period was begun at the time of the final basalt flow dated about 300,000 BP. The third stage is designed for the time when the Hantan river channel was dropped down to a level from which the channel could not influence the top of the basalt any more No more deposit could be formed but erosion by surface water has been continued on the top of the basalt since then. The dropping of the Hantan river channel was probably not very long after the final flow of the basalt. Because of frost action and heavy concentrated precipitation in the basin area along with blocky and clumnar joint structure of the basalt, erosional process of the basalt is believed to have been carried out within a relatively short time. The lowering of the Hantan river channel was probably completed in a cycle of major fluctuation of world cimate. Also, the redclay on the top of the basalt is believed to have been formed during a warm period around 200,000 BP, which accords with the climatic change suggested above fair1y well. The Paleolithic materials in tile deposits fell accordingly into approximately same time period.

• Journal of Korea Water Resources Association
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• v.35 no.2
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• pp.137-148
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• 2002

The purpose of this study was to examine the effect of water quality improvement due to dredging the bottom deposit at the downstream of a urban river. The finite difference method was used to analyze the water quality variations caused by the depths of dredging and intercepting ratios of the goal years. 21 boring points were selected along the 11.2km river reach running through a metropolitan city. The pollution levels of the deposits from the bored Points were examined by the leaching test. The improvement effect of the water quality, measured as changes of COD, were carried at under drought, minimal, and normal flow. The result indicates that the dredging of the contaminated sludge contributes the improvement of the water quality.

• Journal of Environmental Science International
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• v.13 no.3
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• pp.263-277
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• 2004

The purpose of this study is to analyze the characteristics of riverbed variation due to the sediment protection weir located on the estuary of the main stream of Taehwa river using I-D finite difference model, HEC-6 model, and the followings are the results of estimating sediment transport rate, amount of scour or deposition, and accumulated amount of deposit according to before and after of the sediment protection weir removal with various flow rates in the channel. Ackers-White transport function produced the greatest sediment transport rate while Meyer-Peter showed the smallest sediment transport rate at the most down stream area of the watershed through the sediment transport rate analyses for various flow rates according to the existence or nonexistence of the sediment protection weir. Toffaleti's and Colby transport function were closest to the average value, and the difference among the results of the sediment transport functions showed up to 8～9 times. Duboy's transport function produced the greatest riverbed variation while Toffaleti's showed the smallest variation through the riverbed variation analyses according to the existence or nonexistence of the sediment protection weir. Yang's was closest to the average value, and the difference among the results of the riverbed variation analyses ranged from 1.4 times to 11 times. It is thought that a sediment transport function must be selected very carefully with respect to the criteria of sediment yield estimation because the analysis results of the sediment transport rate and riverbed variation according to flow rates showed significant differences among the sediment transport functions, and the differences of sediment transport rate and riverbed variation according to the various sediment transport functions decreased as the flow rate increased.

• Journal of Korean Society for Geospatial Information Science
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• v.15 no.2 s.40
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• pp.25-31
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• 2007

The recent frequent heavy rainfall has caused an increased in soil erosion and the soil drain which drained soil has caused decreased in channel radius and environmental problems by turbidity. In this study, the optimum size of the sediment basin was tested with soil erosion estimated from the Universal Soil Loss Equation (USLE) in the basin using by GIS data. The results show that the estimated soil erosion and the designed soil deposit are $72.1\;m^3$ and $85.0\;m^3$ respectively and the size of sediment basin is proper. In this study the water depth was calculated from the Hec-Ras model to test the stability of the bank and to prove submersion of the inside fields from stream overflow.

• Journal of the Korean association of regional geographers
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• v.14 no.1
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• pp.1-18
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• 2008

If there is no choice but to be urbanized, we should examine how human interference has had influences on the area to keep the river environment safe and stable. This study is aimed at finding improvement by examining the effect of human interference in Gapcheon river in Daejeon, which is developing fast. Distinctive features of human interference in Gapcheon river are followings. First, middle and upper reaches of Gapcheon river are being maintained and restored focusing on flood control but are scheduled to develop city and channel. Second, the rear area of middle and lower reaches of Gapcheon river is already developed into an urban district and solidified into artificial stream for leisure activities installing the artificial structure for fun. Third, lower reaches of Gapcheon river are in an unstable condition because of straightening waterway and developing rear area of river. Up to now, geographical features and bio-diversity of Gapcheon river has been ruined by the artificial management of river centered for technical engineering. From now on, followings should be considered for management of urban river. First, it is focused on maintaining eco system by itself than usage for human. Second, natural features of rear area of river should be taken into consideration and should be preserved before developing urban city and hills, back marsh, channel deposit and swamp to directly have an influence on river.