• Journal of Environmental Science International
• /
• v.11 no.3
• /
• pp.191-199
• /
• 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.

• KSCE Journal of Civil and Environmental Engineering Research
• /
• v.12 no.3
• /
• pp.115-125
• /
• 1992

The variation of flow pattern caused by the topographical change of Kwangyang bay, is analyzed using the numerical tidal model for the depth-integrated two- dimensional long wave equation. The results of study are as follows. Due to pier construction, the area of water surface is deceased and the water inflow into the Kwangyang bay is reduced. For this result, at the outer bay of Myo island, the tidal range is slightly increased. And at the inner bay, water level is dropped generally, and especially at the time of low water tide, the phenomena of water level drop obviously appears. According to the variation pattern, flow velocities is lower than those of non-construction condition over the Kwangyang bay. But at the channel(from Kwangyang east stream) flowing into the east Kwangyang bay, for the contraction of channel profile, flow velocity is increased. The study based on the 100 year frequency design flood discharge from Sueocheon(river) and Dongcheon(river) which are flowing into the bay and Seomjin River flowing along the boundary of the bay is also performed. During the spring tide condition, the results showed the rise of water level about 1.2 m at Seomjin River Estuary and 0.3 m at inner bay is occurred.

• Journal of The Geomorphological Association of Korea
• /
• v.27 no.1
• /
• pp.33-45
• /
• 2020

A number of unconsolidated deposits, consisting of a layer of gravels and silt, are found in Dangjeong-ri, Seocheon-gun in the western coast. From below in the stratigraphic sequence, the gravel layer ranging up to a maximum thickness of about 2 meters is interpreted as being formed by fluvial processes of an old channel (Dangjeong S.), and the overlying silt or sandy silt layer of 2 to 3 thickness meters is assumed to be emerged paleo-tidal sediments which was deposited in low tidal-energy environments. As the results of rock surface IRSL datings, the depositional ages of gravels are confirmed as ca. 78,000 ~ 83,000 years BP, indicating that the layer was formed in response to a high-stand sea level of MIS 5a along the Dangjeongcheon estuary. It is presumed that the relative height of 4.5 meter between the altitude of the stream bed (9.5 m) and the altitude of the bedrock boundary in the gravel layer (14 m) indicates the uplift amount since deposition. Paleo-sedimentary environments and an altitude of paleo-shoreline in the study area will be discussed with additional age dating focused on the silt layer.

• Journal of the Korean Society of Hazard Mitigation
• /
• v.9 no.1
• /
• pp.115-121
• /
• 2009

It is to use effectively for stream channel and watershed management as the prediction and the analysis of bed changes characteristics in the Seomjin river downstream. The necessary data (section, bed composition material, pivot point water elevation, coefficient of roughness) with regard to analysis of the bed changes characteristics were based upon the survey data and analysis results in the Seomjin river maintenance basic plan. The prediction of bed changes was also completed with HEC-6 model. The study results were summarized as follows: The main factor of bed changes in the Seomjin river downstream can be decided by extreme extraction of bed aggregate rather than the change of hydrological data. According to the analysis of bed stability based on the relation between friction velocity and representative grain size, and the relation between dimensionless tractive force and representative grain size, the Seomjin river downstream appears to be increased overall. The bed composition material in the stream channel of the Seomjin river of 2003 year shows higher composition rate of gravel and lower composition rate of sand as compared to those of 1989 year. According to result that the prediction of bed changes, it is estimated that the bed will be risen approximately 1.5 m to the place up to 9 km from the estuary, have been repetitively risen and fallen up to 1 m to the place between $9{\sim}21\;km$ section, and fallen about 0.5m to the place between $22{\sim}25\;km$ section. As a result, the bed of the Seomjin river downstream can be decided to be risen gradually. However, since the prediction of this study is based on the assumption that there will be no forced aggregate picking, the bed changes can be much greater than expected when there is a massive aggregate picking as it had happened before.

• Korean Journal of Environmental Biology
• /
• v.33 no.3
• /
• pp.314-329
• /
• 2015

The fish fauna was investigated from 2010 and 2013 at main stream and tributaries in the Seomjin River which has no estuary dike. The collected fishes were identified into 37,751 individuals of 107 species of 81 genera belonging to 41 families. Among the collected fishes the primary freshwater fishes were 57 species (Relative Abundance: 53.3%), the secondary fishes were 10 species (RA: 9.3%) and the marine fishes were 40 species (RA: 37.4%). The dominant species was Zacco platypus (RA: 28.7%), and the subdominant species was Zacco koreanus (RA: 15.0%). The endemic species were 21 species (RA: 31.3%). The endangered fishes were Acheilognathus somjinensis (Level I), Lampetra reissneri (Level II) and Microphysogobio koreensis (Level II). The exotic species were Carassius cuvieri, Lepomis macrochirus and Micropterus salmoides. We supposed that Odontobutis interrupta in the Seomjin River is translocated species.

• Ecology and Resilient Infrastructure
• /
• v.7 no.4
• /
• pp.353-365
• /
• 2020

In this study, the characteristics of bed elevation changes of the Nakdong River when weir gates are opened were analyzed using the Hydrologic Engineering Center-River Analysis System (HEC-RAS). The study area was 292.37 km downstream of the Gudam Bridge to the Nakdong estuary of the Nakdong River. The HEC-RAS program, which is a 1D numerical analysis model, was used to simulate bed elevation changes. Simulations were conducted under two scenarios from 2017 to 2019. Scenarios 1 and 2 were devised under the conditions of a fully opened gate and during gate installation, respectively. Results confirmed that, under the conditions of Scenario 1, deposition occurred in most sections from the Hapcheon-Changnyeong weir to the Changnyeong-Haman weir (a distance of approximately 40 km). In addition, it was predicted that the flow that included sediments in the main stream of the Nakdong River was not interrupted by the weir structure and regularly produced changes in the river bed.

• Korean Journal of Ecology and Environment
• /
• v.38 no.spc
• /
• pp.44-53
• /
• 2005

The Nakdong River, which lies in a monsoon climate zone with warm rainy summers and cold dry winters, is a typical ecosystem showing the attributes of a regulated river. In 2003, the total annual rainfall (1,805 mm) was higher than the average of the past nine years from 1994 to 2002 (1,250 mm). In September a powerful typhoon, Maemi, caused a big impact on the limnology of the river for over two months. Among the limnological variables, turbidity in 2003 (37.4 ${\pm}$ 94.1 NTU, n = 54) was higher than the annual average for ten years (18.5 ${\pm}$ 2.3 NTU, n = 486) in the lower part of the river (Mulgum: RK 28). Furthermore, physical disturbance (e.g. stream bank erosion within channel) in the upstream of the Imha Dam (RK ca. 350; river distance in kilometer from the estuary barrage) in the upper part of the river was a source of high turbidity, and impacted on the limnological dynamics along a 350 km section of the middle to lower part of the river. After the typhoon, high turbidity persisted more than two months in the late autumn from September to November in 2003. Flow regulation and the extended duration of turbid water are superimposed on the template of existing main channel hydroecology, which may cause spatial changes in the population dynamics of plankton in the river.

• Journal of Wetlands Research
• /
• v.21 no.2
• /
• pp.102-113
• /
• 2019

Slack-tide sampling was carried out at 6 stations at high and low tide for a tidal cycle during spring tide of the early summer (June) and summer (July, August) of 2016 to determine the difference of water quality according to tide in Masan Bay, Korea. The mixing regime of all the water quality components investigated was well explained through the correlation with SAL. In the early summer and summer, TURB, DSi and NNN which mainly flow into the bay from the streams and SS, COD, AMN and $H_2S$ which mainly indicate the internal sink and source materials have a property of conservative mixing and non-conservative mixing, respectively. The conservative mixing showed a good linear relationship of the water quality between high and low tide, and the non-conservative mixing showed a variation of different pattern each other. Factor analysis performed on the concentration difference data sets between high and low tide helped in identifying the principal latent variables for them. In early summer, multiple effects (tidal action, natural influx and internal sinks and sources etc.) acted in combination for the differences to be distributed evenly in four factors (VF1~4), since there were few allochthonous inputs as a low-water season. On the contrary, in summer, the parameters showing large concentration difference at ST-1 affected by stream water were concentrated in one factor (VF1) and clearly distinguished from the parameters affected by the internal sinks and sources. In fact, there is no estuary (bay) that always maintains steady state flow conditions. The mixing regime of an estuary might be changed at any time due to the change of flushing time, and furthermore the change of end-member conditions due to the internal sinks and sources makes the occurrence of concentration difference inevitable. Therefore, when investigating the water quality of the estuary, it is necessary to take a sampling method considering the tide to obtain average water quality data.

• Journal of the Korean GEO-environmental Society
• /
• v.12 no.8
• /
• pp.51-57
• /
• 2011

Surface water at the lower part of the Seom-jin river has a high salinity because the erosion at river bottom has made sea water move upstream continuously since 1978. The effect of underground dam on the prevention of sea water intrusion was modelled in this study. Present chloride concentration in surface water decreases exponentially along a river and in groundwater is about one-tenth of surface water's. The finite element method model, FEFLOW, was conducted on the assumption that the underground dam with a height of 25m over a bedrock is located under a water surface at the site of 4.6km from an estuary. The result shows that the position with chloride concentration of 0.25psu moves downstream from the sites of 25km to 22km, if an enough sedimentation with 5m thickness happens in the upper reservoir of underground dam. On the other side, the underground dam is little effective for the prevention of sea water intrusion in case of non-sedimentation.

• Korean Journal of Ecology and Environment
• /
• v.44 no.3
• /
• pp.303-313
• /
• 2011

Field observations and culture experiments have been carried out during the rainy season (on the 6th, 8th and 27th July 2009) to examine changes in the primary productivity and associated plant pigments in the estuary of the Seom-jin River. Primary productivity was determined at four sampling stations along the salinity gradient. On 6th July (before heavy rain) primary productivity ranged from 689~1,169 mgC $m^{-2}$ $d^{-1}$. On the 8th, just after more than 216.5 mm of precipitation, euphotic layers at all stations were reduced to very shallow water because of the high concentration of suspended solids in the water. This resulted in dramatically decreased primary productivity down to as low as 12~32 mg C $m^{-2}$ $d^{-1}$. However, after the rain, primary productivity on the 27th ranged from 266~999 mgC $m^{-2}$ $d^{-1}$, demonstrating a fast recovery in the upper stream water to similar productivity levels to those before the rainy season. Concentration of fucoxanthin in the water was highest on the 6th July. Before the rain, concentration of the zeaxanthin, increased as the salinity decreased. Immediately after the heavy rain, the Chl b (Chlorophytes) concentration was higher at all sites than before the rainy season. The concentration of fucoxanthin decreased after the heavy rain. At the downstream site, peridinin (Dinoflagellates) were found. During the rainy season, the diatoms contributed to the primary productivity at all sites. However, after the rainy season, Chl b (Chlorophytes) and Peridinin (Dinoflagellates) increased, demonstrating the enhanced contribution of those species in addition to diatoms.