• Ecology and Resilient Infrastructure
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• v.2 no.4
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• pp.324-329
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• 2015

For the restoration of lateral connectivity between rivers and floodplains, it is important to find the isolated former floodplain (IFF) and to characterize its land use in Korean rivers which were channelized by levee constructions for flood protection. The aim of this study is to map the IFF and to assess its land use pattern in the Nakdong River, Korea. The isolated former floodplain was explored by being overlapped on a digital elevation model (DEM), digital topographic map and design flood level using a geographical information system (GIS) in the Nakdong River basin. The land use of the identified IFF was classified by land-use map. The total number of IFFs was 384 and their total area was $291km^2$. While IFFs were usually surrounded by mountain forest in the upper river area, they tended to be located on wide plain areas in the downstream area of Nakdong River. The land use pattern of IFFs was mostly farmland (73.9%) and urban areas (12.7%) in the river. The results of delineation and land use analysis of isolated former floodplain in the Nakdong River will be used as a base line data for planning stream restoration.

• Ecology and Resilient Infrastructure
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• v.2 no.2
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• pp.128-136
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• 2015

River areas include channels, floodplains and all the areas affected by physical and ecological processes in river systems. It is noticeably different from present riparian zone which is bounded by dykes. In this study, two methods for delineation of a floodplain are proposed, which are used for evaluation of the function of a river. One of them is a geomorphology-based technique and the other is hydrology-based inundation analysis. For the Mankyung River, these two methods are applied to delineate the floodplain area. Areas delineated with both methods are mutually compared. The results show that the geomorphology-based method is suitable for the delineation of a valley bottom, including the floodplain in a broader sense, which is unlike an inundated area reflecting contemporary hydrologic conditions. Compared with other flood frequency areas, a 100-year flood inundation area was found reasonable to represent the spatial extent of a floodplain without regard to the longitudinal location along a river. However, it is necessary in certain rivers reach where the division of a channel exists to compare a geomorphological analysis on a valley bottom with an inundation area of different frequencies.

• Journal of Environmental Science International
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• v.13 no.1
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• pp.19-26
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• 2004

The purpose of the study was to construct a forecast system of flood inundation area at natural stream channels. The study built the system to interpret the flood inundation area in four stages ; constructing topography data around the stream channel, interpreting flood discharge, interpreting flood elevation in the stream channel, and interpreting the flood inundation and mapping. According to the result of the analysis, as for the characteristic of flood inundation around the area within the purview of this study, although there were areas where flood inundation over a bank caused a flooded area, the failure of the internal drainage in the ground lower than flood elevation caused more serious problems. Rather than the existing method where only the estimated flood elevation data is used based on the hydrographical stream channel trace model(such as the HEC-RAS model) to establish the flood inundation area, if the procedure introduced in this study was applied to interpret the floodplain, actual flood inundation area could be visibly confirmed.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.22 no.4
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• pp.25-36
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• 2021

This study analyzed the causes of flood accidents, such as isolation and lost footing accidents in Dorimcheon, to provide legal and institutional improvements. For cause analysis, Field Investigation, Stakeholder Interview, Report, manual, Law et al. Review, Analysis of water level change characteristics, automatic alarm issuance standard level analysis, and evacuation time according to river control were evaluated. Dorimcheon has the characteristics of a typical urban river, which is disadvantageous in terms of water control. In addition, the risk of flood accidents is high because the section where fatal accidents occur forms sharply curved channels. Tripping and isolation accidents occur in the floodplain watch and evacuation stage, which is the stage before the flood watch and warning is issued. Because floodplain evacuation is issued only when the water level rises to the floodplain, an immediate response according to the rainfall forecast is essential. Furthermore, considering that the rate of water level rise is up to 2.62 cm/min in Sillimgyo 3 and Gwanakdorimgyo, sufficient evacuation time is not secured after the floodplain watch is issued. Considering that fatal accidents occurred 0.46 m below the standard water level for the flood watch, complete control is very important, such as blocking the entry of rivers to prevent accidents. Based on these results, four improvement measures were suggested, and it is expected to contribute to the prevention of Tripping and Isolation Accidents occurring in rivers.

• The Korean Journal of Ecology
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• v.27 no.4
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• pp.211-216
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• 2004

The complex ecological researches were made in the broad-leaved forest zone of Central Europe in nature reserves and national parks located on the banks of the river (hydrology, vegetation, soils, unconfined ground waters). The natural conditions of terrestrial ecosystems and natural sites were compared along the course of the rivers. The significant negative influence of low-dammed (low-confined hydrotechnic) construction and small reservoirs on vegetation and soils of floodplain was revealed. On the basis of analysis of mean annual water level and flow trends on the multi-years series (60-100 years) of the hydrometric stations on the rivers under consideration the significant influence of natural long-term variability of watering on vegetation dynamics in the floodplains was revealed.

• International Journal of Contents
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• v.8 no.3
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• pp.34-41
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• 2012

The concept of vegetation freeboard equivalence (VFE) is presented from the comparison between the rise in stage with/without vegetation and the freeboard height under design discharge conditions. In South Korea, the freeboard height of large, medium and small rivers is defined as a function of river discharge. Two models are used for this analysis of flood stage with and without vegetation: the 1-D model HEC-RAS and the 2-D model RMA-2. Both models are applied to three river study sites of the Geum River in South Korea as representative sites for a large, a medium and a small river. The analysis shows that without vegetation, both models provide comparable results and the calculated results are in very good agreement with the design configuration. The vegetation effects on the medium river are less significant, and the freeboard is adequate to contain the rise in stage from the added floodplain vegetation in large rivers. The concept of vegetation freeboard equivalence is therefore useful for the analysis of flood river stages after the restoration of channels with increased floodplain vegetation.

• Ecology and Resilient Infrastructure
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• v.4 no.2
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• pp.97-104
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• 2017

For the restoration of lateral connectivity between channel and floodplain, it is important to find the former floodplain and to characterize its land use in streams which were channelized by the levee construction for the flood protection. The aim of this study is to map the former floodplains and to assess its land use pattern in the Cheongmi-cheon Stream, Korea. The former floodplains were explored by being overlapped on a digital elevation model (DEM), digital topographic map and design flood level using a geographical information system (GIS) in the Cheongmi-cheon Stream basin. The land use of the identified former floodplains was classified by land-use map. The total number of the former floodplains was 104 and their total area was $11.9km^2$ in the Cheongmi-cheon Stream. The land use pattern of the former floodplains was mostly farmland (87.1%). The former floodplains were usually surrounded by mountain forest in the downstream of the Cheongmi-cheon Stream. These former floodplains are probably suitable for restoration of lateral connectivity because of lower ratio of urban area but higher ratio of farmland. The results of delineation and land use analysis of the former floodplain can be used as a baseline data for planning stream restoration in the Cheongmi-cheon Stream.

• Journal of The Geomorphological Association of Korea
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• v.23 no.3
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• pp.13-25
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• 2016

The purpose of this study is to investigate the location characteristics in which 'large Jar coffin' (hereinafter referred to as 'Jar coffin') distributed in the Yeongsan river basin area in Jeonnam province by means of topographic analysis. 75 Jar coffins (74.3%) in 19 relics (90.5% of total) were found in hill and 26 Jar coffins (25.7%) of two consumption relics (9.5%) were found in floodplain. Among them, 34 (45.3% of total) and 41 (54.7% of total) Jar coffins were found in the Crest surface and Sideslope of hills, respectively. In particular, 26 (34.7%) Jar coffins are mostly located in the Crest flat. This result implies that people at that might be consider the river inundation, and mostly choose hill rather than floodplain when building the Jar coffin. therefore amongtherefore among micro-landform units of the hill, it seems that the 'Crest flat' was the preferred place for the building the Jar coffin at that time.

• Journal of the Korean Society of Hazard Mitigation
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• v.5 no.3 s.18
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• pp.47-55
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• 2005

In order to design and manage the urban streams, the change of hydraulic characteristics by vegetation must be analyzed clearly. Planting criteria of vegetation in a urban stream were investigated and the design method of vegetation permission map was analyzed in this study. In addition, variations of water level due to vegetation are calculated by quasi two dimensional numerical model, HEC-RAS model and FESWMS model. Joongrang stream(Gunja bridge${\sim}$Jangan bridge reach) was selected as the case study stream. According to the criteria of vegetation, it is decided that vegetation density was $0.5{\sim}1.0$ tree/ha for selected tall tree in right floodplain and shrubs can be planted in the right and left floodplain area except the important hydraulic structures site. The selected shrubs planting simulations with three models show that water level in selected floodplain area increase approximately 12cm for the 100 year return period flood. The applicability of vegetation permission map in Korean urban stream was analyzed in this paper.

• Journal of the Korean Society of Industry Convergence
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• v.2 no.1
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• pp.35-43
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• 1999

The purpose of this study is to derive the optimal methodology estimating the changes of fluvial hydraulic characteristics due to semi-covering work of urban stream. First, after collecting the data of the daily maximum rainfall of Chungju gaging station, the frequency analysis was carried out with frequency factor method, which includes normal, two-parameter and three-parameter lognormal, Gumbel-Chow, pearson type III, log-pearson type III distribution, and the goodness of fit test was executed by $x^2$-test and Kormogorov-Smimov test. Using the SCS method, the effective rainfall was estimated and the peak flow was calculated by the area-routing method. The HEC-2 model was applied to calculate water surface profiles for steady, gradually varied flow at Kyohyun river system in Chungju city. The model was applied to floodplain and riverbed management to evaluate flood way encroachments and to delineate flood hazard by riverside roadway construction. The model also was used to evaluate effects on water surface profiles of river improvement and levees as well as the presence of bridges or other hydraulic structures in the floodplain.