• Journal of The Korean Society of Agricultural Engineers
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• v.62 no.2
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• pp.1-15
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• 2020

In this study, the characteristics of crop damage area by flooding for 113 middle range watersheds during 2000-2016 were analyzed and future crop damage area by flooding were analyzed using 13 GCM outputs such as hourly maximum rainfall, 10-min maximum rainfall, number of days of 80 mm/day, daily rainfall maximum, annual rainfall amount associated with RCP 4.5 and RCP 8.5 scenarios and watershed characteristic data such as DEM, urbanization ratio, population density, asset density, road improvement ratio, river improvement ratio, drainage system improvement ratio, pumping capacity, detention basin capacity, and crop damage area by flooding. A constrained multiple linear regression model was used to construct the relationships between the crop damage area by flooding and other variables. Future flood index related to crop damage may mainly increase in the Mankyung watershed, Southwest part of Youngsan and Sumjin river basin and Southern part of Nackdong river basin. Results are useful to identify watersheds which need to establish strategies for responding to future flood damage.

• Journal of Korea Water Resources Association
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• v.49 no.6
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• pp.459-467
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• 2016

LISFLOOD-FP model in which channel flows are resolved separately from the floodplain flows using either a kinematic or diffusive wave approximation has been used to analyze flooding behavior on the lower Mankyung River influenced by backwater. A calibration and validation process was applied using the previous flood events to assess the model performance. Sensitivity analysis was conducted for main calibrated parameters, such as Manning roughness coefficient and downstream boundary condition. Also, we examined the effect of warm-up for the initial conditions. The results show that the computed hydrograph is in good agreement with measured data on the study reach, even though it was a hydrologic kinematic wave model. The sensitive analysis show that the difference between the computed results may be greater depending on the used calibrated parameters and that the sufficient calibration/validation process against various flood events is necessary. If the flood inundation simulation is performed using the validated model, it is expected to be able to contribute about river planning and policy decision-making for flood damage reduction.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
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• v.8 no.2
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• pp.138-150
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• 2003

In the mid-west coast of Korea where Mankyung and Dongjin rivers discharge fresh water, Saemangeum tidal dyke of 33 km long is under construction to reclaim the very shallow estuary region of 41,000ha. Main source of freshwater in this coastal area is Keum River locating closely north of the dyke. At present, the dyke connected with Gogunsan-Gundo separates this area into three regions; northwestern, southwestern and eastern (Saemangeum) region of the dyke, and the water in Saemangeum region is exchanged through one gap in the northern dyke and two gaps in the southern dyke. We have observed distributions and structures of temperature and salinity to examine the summer circulation related with low-salinity water in this coastal area in 1998 and 1999. In the surface layer off the northern dyke a tongue-like distribution of low-salinity extends 60 km long from Keum River estuary mouth to the northwest, forming plume front bounded by offshore water. In the inner region of Saemangeum dykes salinity distributions show that two river waters are merged together and the low salinity water is deflected toward northern gap of the dyke. In the surface layer off the southern dyke we observed small tongue-like distribution of another low-salinity water extending to the north from Gomso Bay. Based on the analysis of distributions of low-salinity water and frontal structures, we can suggest an anticlockwise circulation of coastal water around the dyke, composed by the estuarine water outgoing from the inner region of the dyke through the northern dyke's gap and the inflow through two gaps of southern dyke from offshore. After completing the dyke construction, this coastal circulation around the dyke will be, however, changed because fresh water discharge of Mankyung and Dongjin rivers will be routed artificially and directly into the area offshore of the southern dyke.

• Journal of Korea Water Resources Association
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• v.47 no.4
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• pp.397-409
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• 2014

In this study, the assessment scheme has been developed to evaluate the ecological function of rivers which were changed by the river improvement project. The evaluating factors are composed of physical structure in river channels and ecological connectivity in river areas, and each value of the factors is quantified based on 4 and 2 variables, respectably. This scheme was applied to past (1918, before artificial river improvement) and present Mankyung River area. A GIS model was adopted for calculating, analysing, and presenting river ecological conditions using the 204 grids and 7 reaches in study area. Comparison results show that the evaluation grade was decreased in both factors after river improvement. The main causes of lower grade (from II to IV) for physical structure are the river straightening and crossing structures. The reduction (from II to III) in ecological connectivity grade effected by linear fragmentation due to roads and rails is found to be greater than areal fragmentation due to land-use. In particular, it is also found that a high degree of ecological connectivity in 1918 was distributed along the river, but that one in 2007 showed a tendency to scatter because of the construction of levee and increase of urbanized area.

• Journal of Korean Society on Water Environment
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• v.31 no.5
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• pp.507-522
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• 2015

In this study, some of the model verification results of STREAM (Spatio-Temporal River-basin Ecohydrology Analysis Model), a newly-developed hybrid watershed model, are presented for the runoff processes of nonpoint source pollution. For verification study of STREAM, the model was applied to a test watershed and a sensitivity analysis was also carried out for selected parameters. STREAM was applied to the Mankyung River Watershed to review the applicability of the model in the course of model calibration and validation against the stream flow discharge, suspended sediment discharge and some water quality items (TOC, TN, TP) measured at the watershed outlet. The model setup, simulation and data I/O modules worked as designed and both of the calibration and validation results showed good agreement between the simulated and the measured data sets: NSE over 0.7 and $R^2$ greater than 0.8. The simulation results also include the spatial distribution of runoff processes and watershed mass balance at the watershed scale. Additionally, the irrigation process of the model was examined in detail at reservoirs and paddy fields.

• Journal of Wetlands Research
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• v.16 no.2
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• pp.213-220
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• 2014

Recently, river maintenance is change due to concern for the environment increases. Thus, the river restoration and river environment is best part of river maintenance. In case of Korea, existing river is improvement straightly for flood control and transportation. When the stream channel is straightly, maintain stability is important. Thus, construction of levees along the river. The various river structures for the purpose of flood control and transportation are inhibit factors of longitudinal and lateral connectivity. Connectivity is defined as the maintenance of lateral, longitudinal, and vertical pathways for biological, hydrological, and physical processes. Long-term point of view, increased connectivity is very important for a healthy ecosystem composition. As the first step of river restoration, this study described theory and concept of river continuum and the numerical model was applied to a real topography to simulate the flow analysis with or without segregated and blocked space in the Mankyung river. The results of this study can be utilized to develop the watershed connectivity assessments methods in order to the river restoration.

• Journal of Korea Water Resources Association
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• v.31 no.4
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• pp.503-512
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• 1998

When various elements of water balance are displayed at several points of a river network, the runoff amounts at an estuary especially tidal influenced are affected from the elements. This problem can be solved by a model that can generalize and formulate the elements and simulate daily runoff and water requirement. The WWASS model was built using DIROM for the simulation of daily runoff and water requirement, and the water balance elements were modeled to be balanced at the each control point of river network. The model was calibrated, verified and applied to the watershed for the Saemankeum tidal land reclamation development project. It showed that the results from the streamflow simulation at the Mankyung and Dongjin estuary were acceptable for the design of the Saemankeum estuary reservoir.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 1999.10c
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• pp.155-161
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• 1999

The land reclamation area of Saemangeum(Kunsan) is located between 126$^{\circ}$10' E~126$^{\circ}$50' E and 35$^{\circ}$35' N~356$^{\circ}$05'N at the western coast of the Korean peninsula. The are many small islands including extensive areas of semi-diurnally flooded and dewatered tidal flats. The reclamation area of Saemangeum has a range of 5.6m spring tide and the maximum tidal current speed is about 1.41m s-1 in ordinary spring tide. Most of the sediments deposited on the tidal flats are transported from the Geum river, the Manjyung river and The Dongjin river. The soil in this area consists of silty sand with the depth of 10m to 30m . The wind in winter is strong from the direction of northwest. In the past twenty years, land reclamation projects for agricutural purpose or industrial cocmplex have been mostly implemented along the western coast of Korea. Saemangeum coastal area is being constructed the33km sea dike and 40, 100ha reclamation area. The purpose of this study is to find the residual circulations in four seasons after the dike construction by a robust diagnostic and prognostic numerical model. Heat flux at the sea surface in January ,May , August , October was asopted on the basis on the daily inflow of solar radiation at the earth surface, assuming an average atomospheric transmission and no clouds , as a function of latitude and time of year(George L.P.J.E William, 1990). The discharge from the Geum , the Mankyung and the Dongjin rivers was adopted on the basis of experience formula of river flow in January , May ,August, October (The M. of C.Korea, 1993) . Water temperature and salinity along the open boundaries are obtained from the results of field observation s.

• Journal of Korea Water Resources Association
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• v.52 no.spc2
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• pp.865-873
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• 2019

The purpose of this study is to develop and apply a river space restoration framework considering various functions of river basin system. In particular, we will present sustainable river basin management directions by quantifying the effect of improving the aquatic ecosystem through the restoration of river space. For this purpose, the present problems are derived from functional aspects of the river basin, and the river area restoration framework linked with the individual outcome indicators is constructed to evaluate the restoration effect by each function. The ecological impact of restoration of river area was quantitatively analyzed by introducing ecotope concept. As a result of the comparison of restoration effects by creating three kinds of river area restoration scenarios, the construction of suitable habitat such as backswamp in the expanded area has shown favorable results in expanding biodiversity. The diversity evaluation of ecotope in conjunction with the hydraulic and hydrological characteristics of the year will not only provide the expected effects of restoration of river space but will also serve as a criterion about post-project monitoring for outcome evaluation.

• Proceedings of the Korea Society of Environmental Toocicology Conference
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• 2001.05a
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• pp.130-130
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• 2001

산업사회의 발달로 말미암아 발생되는 여러 가지 문제 중 환경에 미치는 영향은 막대하다 하겠다. 특히 환경오염물질의 하수누출은 생태계뿐만 아니라 인간의 생명을 직접 혹은 간접적으로 위협하고 있다. 이러한 심각성을 인식하고 최근에 환경영향평가의 방법이 많이 개발되고 있다. 그러나 지금까지의 방법으로는 환경오염물질이 미치는 독성은 아직 미지수로 남아 있다. 이러한 분위기에 편승하여 환경독성 평가방법 중 어류 또는 포유류의 면역계에 대한 영향을 평가하는 방법을 개발하여 환경오염평가에 활용하고 있다. (중략)