• Journal of Forest and Environmental Science
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• 제30권1호
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• pp.76-84
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• 2014

This study was performed to monitor the effects of water level change on changes of landscape, vegetation community, and species diversity of riparian forest. Hantan river dam, study area, has been constructed in the area of Chansoo-myeon, Pocheon-si and Yeoncheon-eup, Yeoncheon-gun, Gyeonggi-do, which is a dam for flood control only in flooding season. Landscape changes were notable after the construction of coffer dam, and the changes were caused by water level increase in areas of riparian forests which consisted of mainly withered willow as a dominant species in the flooding season. It changed vegetation communities of riparian forest from Phragmites japonica and Salix koreensis to Phragmites japonica. Species diversity index was lowest in 2010 when the coffer dam was constructed and showed an increasing trend later. Thus, this study is well in agreement with a previous report that plants of the genus Salix wither by muddy water during flooding and also suggests, controlling water level of river and prediction of water level change's effects should be considered when any facilities are planned.

• 대한토목학회논문집
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• 제33권2호
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• pp.537-548
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• 2013

본 연구에서는 2006년 홍수시 충주댐 운영에 따른 댐 상 하류의 홍수위 상승영향을 정량적으로 분석하기 위하여 팔당댐 상류의 한강 본류에 위치한 충주댐을 기준으로 상류구간과 하류구간으로 구분하고, 1995년부터 2008년까지의 홍수사상을 대상으로 모형을 검보정함으로써 수리학적 모형을 구축하였다. 구축된 모형을 이용하여 충주댐의 유무를 가정하여 충주댐의 홍수조절효과를 검토하고, 방류량의 변화에 따른 상 하류 주요지점의 수위 상승영향을 정량적으로 분석하였다. 분석결과, 2006년 홍수시 충주댐의 운영이 비교적 적절하게 수행되었음을 확인하였으나, 충주댐의 홍수조절효과는 댐 하류구간에 집중되어 있어 댐 상류 홍수피해 저감을 위한 제도적 보완이 필요한 것으로 분석되었다. 이러한 문제점을 해결하기 위하여 기존 댐 배수구간 상류 하천의 기점수위 결정방법의 한계를 검토하였으며, 댐 배수구간과 상류 하천의 계획홍수량 불연속을 반영할 수 있는 기점수위 결정방법을 제안하였다. 제안된 방법은 댐 상류하천의 홍수피해 저감을 위한 설계 및 홍수피해 발생시 피해원인 분석에 활용될 수 있을 것이다.

• Korean Journal of Hydrosciences
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• 제5권
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• pp.17-31
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• 1994

Because of the Keumkangsan-Dam and the Peace-Dam constructed in recent years, it is expected that the peak flood discharge and the peak flood stage at the Hwachun-Dam site have been changed. In this study, two methods were used to simulate and compare the effects of the upstream dam construction on the change of the discharge and the stage. One is the storage function method widely used for the hydrological routing in the country. The other is the DWOPER(Dynamic Wave Operational Model) package conducted on four different scenarios: (1) before the construction of the Keumkangsan-Dam and the Peace-Dam; (2) the exclusion of the Keumkangsan-Dam watershed (before the construction of the Peace-Dam); (3) the exclusion of the Keumkangsan-Dam watershed (after the construction of the Peace-Dam) ; (4) the exclusion of the Peace-Dam watershed. The results of the four test cases from the two methods show that the peak flood discharge and the peak flood stage at the Hwachun-Dam site are reduced due to the construction of the Peace-Dam. From these findings, it is suggested that the operational criteria for the optimal dam-operation of the Hwachun-Dam need to be modified.

• Animal cells and systems
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• 제16권1호
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• pp.69-76
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• 2012

This study was conducted to examine how a low-head dam removal (partial removal) could affect benthic macroinvertebrate communities in a stream. Benthic macroinvertebrates and substrates were seasonally sampled before and after dam removal (March 2006-April 2007). Benthic macroinvertebrates and substrates were quantitatively sampled from immediately upstream (upper: pool) and downstream (lower: riffle) sites, the location of the dam itself (middle), and immediately above the impoundment (control: riffle). After the removal, species richness and density of benthic macroinvertebrates as well as the EPT group (Ephemeroptera, Plecoptera and Trichoptera) increased to higher levels than those before the removal, while functional feeding groups and habitat orientation groups changed more heterogeneously at the upper site. At the lower site, species richness and density decreased somewhat immediately after dam removal, which was associated with an increase of silt and sand, but recovered after monsoon floods which helped to enhance substrate diversity at the upper site. Decreased dominance index and increased diversity index in both the upper and lower sites are evidence of positive effects from the dam removal. In conclusion, we suggest that even a partial removal of a dam, resulting in increased substrate diversity in the upper site, could sufficiently help rehabilitate lost ecological integrity of streams without major habitat changes.

• 한국물환경학회지
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• 제28권3호
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• pp.418-425
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• 2012

Dam construction in a river can change its hydrological pattern and trap sediments, which results in ecological changes in the downstream. It is a common phenomenon in the downstream of dams to have decreased sediment flow and increased periphyton. Artificial floods and sediment application are suggested as mitigation practices in order to simulate natural process of flood; transporting sediment and sloughing periphyton off. In this study the effects of artificial floods on periphyton were examined by applying sand artificially and discharging water from a dam (Yangyang Dam, Korea). The study area has been suffering from turbidity problems caused by shore erosion of the dam. The accumulation of inorganic sediments and increase of periphyton on the river bottom are the major factors of habitat deterioration in the downstream reaches. Artificial flood and artificial addition of sand was performed in summer and the effects were measured. Piles of applied sands were washed off easily by discharge and it enhanced the periphyton sloughing effect. The removal efficiency of periphyton was 50 ~ 80% within the 2 km reach from the dam. In conclusion artificial floods and sand application can be a good mitigation measure for the habitat rehabilitation after a dam construction in streams.

• Water Engineering Research
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• 제3권4호
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• pp.215-234
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• 2002

Uncertainty in dam breach flood routing results was analyzed in order to provide the basis fer the investigation of their effects on the flood damage assessments and dam safety risk assessments. The Monte Carlo simulation based on Latin Hypercube Sampling technique was used to generate random values for two uncertain input parameters (i.e., dam breach parameters and Manning's n roughness coefficients) of a dam breach flood routing analysis model. The flood routing results without considering the uncertainty in two input parameters were compared with those with considering the uncertainty. This paper showed that dam breach flood routing results heavily depend on the two uncertain input parameters. This study indicated that the flood damage assessments in the downstream areas can be critical if uncertainty in dam breach flood routing results are considered in a reasonable manner.

• 한국지형학회지
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• 제24권1호
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• pp.13-24
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• 2017

This study analyzes altitude changes of riverbed at 6 bridges in the upper and lower reaches of Yeongju Dam in Naeseong River, from 2009 to 2016 just before and after the dam construction. For 5 years from November 2010 to December 2015 when the dam was under construction, approximately 0.091m of the riverbed altitude in average more than twice before the dam construction was lowered, because of the effects of riverbed excavation for riverside maintenance in the upper reaches and transport limitation of flow and sediment by the dam in the lower reaches. Between November 2009 and December 2016 when the dam was in pre-construction and post-construction stages, respectively, the most sites in this study in the upper and lower reaches showed lowering in the riverbed altitudes. On the other hand, the riverbed around Hoeryongpo closed to the river mouth seems to be influenced by channel changes in Nakdong River rather than by the dam construction.

• 한국수자원학회논문집
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• 제34권6호
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• pp.617-625
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• 2001

수공 방어용으로 건설된 평화의 댐은 화천댐과 연계되어 있고 배수 터널과 함께 1단계 준공 상태로서 화천댐 상류에 위치하여 댐 하류에 홍수지체 효과를 갖는다. 따라서 본 연구에서는 현 평화의 댐의 활용방안을 연구할 목적으로 화천댐 시스템 조작을 수행하여 평화의 댐 홍수조절효과와 화천댐의 홍수기 제한수위 등을 검토하고 평가하였다. 그리고 이 결과를 분석하여 화천댐 계통의 이수 증대 방안을 제시하였다. 이를 위해서 우선 저수지 조작 기준과 모형을 설정한 다음 저수지 조작의 최적화를 수행하였다. 이 결과를 바탕으로 최적치에 대한 실적치의 상대적인 값으로 조정계수를 평가하였다. 그리고 화천댐 제한수위의 몇가지 대안에 대하여 최적 저수지 조작을 수행하여 제한수위 적정 수준을 제시하고 경제적인 편익 또한 평가하였다.

• 한국지반공학회:학술대회논문집
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• 한국지반공학회 2008년도 추계 학술발표회
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• pp.854-859
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• 2008

This study describes the aging behavior of soils and its mechanism, which have been reported in the literatures mainly by Mitchell(1986) and Schmertmann(1991). It could be known that aging of soils has both positive and negative effects on mechanical properties of soils. In order to show aging effects on dam behavior, a parametric study was carried out based considering the presence of a weak area within clay core zone of the fill dam. From the comparison of results obtained from numerical analysis and filed investigation, age-softening phenomena occurred within core zone during about 30 years after its completion.

• Advances in concrete construction
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• 제6권3호
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• pp.269-283
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• 2018

This study presents the effects of geometrical dimensions of concrete gravity dams on the seismic response considering different base width/dam height (L/H) ratios. In the study, a concrete gravity dam with the height of 200 m is selected and finite element models of the dam are constituted including five different L/H ratios such as 0.25, 0.5, 0.75, 1.00, 1.25. All dams are modeled in ANSYS software considering dam-reservoir-foundation interaction. 1989 Loma Prieta earthquake records are applied to models in upstream-downstream direction and linear time history analyses are performed. Dynamic equilibrium equations of motions obtained from the finite element models of the coupled systems are solved by using Newmark time integration algorithm. The seismic response of the models is evaluated from analyses presenting natural frequencies, mode shapes, displacements and principal stresses. The results show that the L/H ratios considerably affect the seismic response of gravity dams. Also, the model where L/H ratio is 1.00 has more desirable results and most appropriate representation of the seismic response of gravity dams.