• Journal of the Korean Association of Geographic Information Studies
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• v.17 no.4
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• pp.189-199
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• 2014

Floodplain is a flat plain between levees and rivers. This paper suggests a methodology for analyzing the land uses in the Nakdong River floodplain using the RapidEye imagery and the given LiDAR(LIght Detection And Ranging) DEM(Digital Elevation Models). First, the levee boundaries are generated using the LiDAR DEM, and the area of the floodplain is extracted from the given RapidEye imagery. The land uses in the floodplain are identified in the extracted RapidEye imagery by the ISODATA(Iterative Self-Organizing Data Analysis Technique Analysis) clustering. The overall accuracy of the identified land uses by the ISODATA clustering is 91%. Analysis of the identified land uses in the floodplain is implemented by counting the number of the pixels constituting the land cover clusters. The results of this research shows that the area of the river occupies 46%, the area of the bare soil occupies 36%, the area of the marsh occupies 11%, and the area of the grass occupies 7% in the identified floodplain.

• Proceedings of the Korea Water Resources Association Conference
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• 2010.05a
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• pp.798-802
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• 2010

The integration of GIS and fuzzy MCDA(Multi-Criteria Decision Analysis) allows the engineer to determine the preferred alternative for each spatial location in the study area. The next step is to recommend to the final decision makers a single flood management alternative for the entire region. Note that if the study area is large, it might be possible to use the kind of information to recommend different alternatives for different portions of the region. However, for this study it is assumed that only a single alternative will be used. In this study, a "cost of uniformity" metric is proposed that allows decision makers to compute the impact of selecting a single alternative for the entire floodplain. This metric represents the increase in the average distance metric value as compared to the spatially diverse solution from the MCDA and GIS analysis. The results could be applied to any region of the floodplain as desired. Whether the decision makers decide to apply these calculations to the entire floodplain or to specific important regions within the floodplain, an analysis of the increases in the cost of uniformity provides an integrated way for the decision maker to rank the alternatives. This should provide an improvement in their engineering analysis.

• Journal of Wetlands Research
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• v.19 no.3
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• pp.327-334
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• 2017

The flood pulse in streams enhances the biodiversity and ecosystem services of the channel-floodplain ecosystems by exchanging water, nutrients, sediments and organisms. However, the lateral connectivity in most streams of Korea has been disrupted by the levee constructions for the purpose of flood control and land use of floodplains. To compare the characteristics of floodplain vegetation according to existence of lateral connectivity in streams, we investigated the geomorphological and soil environmental factors and structures and distribution of vegetation in the floodplains connected and isolated by levee to the channel in Cheongmi Stream, Seom River, Hwangguji Stream, Mangyeong River, Gomakwon Stream, and Boseong River, Korea. In comparison of soil environments, moisture and clay contents were higher in the isolated floodplain than in the connected floodplain. According to the result of principal component analysis (PCA) using environmental data, the environments of the connected floodplain and the isolated floodplain were separated by soil moisture contents, soil texture and distribution altitude of the vegetation. The results of detrended correspondence analysis (DCA) using vegetation data showed that the isolated floodplain was dominated by the hydropythic communities of diverse life form and that the connected floodplain was dominated by the hygrophytic communities that endure disturbance. In conclusion, it is thought that the vegetation of the floodplain changed to the lentic wetland vegetation dominated by diverse hydrophytes as the floodplain was isolated from the channel by artificial levees.

• Journal of Korean Society of Environmental Engineers
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• v.31 no.1
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• pp.70-78
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• 2009

Floodplain areas of major South Korean rivers were determined by analyzing topographical maps and hydraulic properties of floodplain soil were measured using disc tension infiltrometer. To assess the possibility of treating secondary effluents of municipal wastewater with floodplain soil, a computer code for the analysis of unsaturated flow in soil was employed along with searches conducted in the literature. Based on the data generated, an estimate of total floodplain filtration capacity in Korea was obtained. The results of our study reveal that Korean floodplains have surface soil that is adequate for treating water. Moreover, the distributions of floodplains are substantial over the entire reaches of the rivers, indicating that the conditions are favorable for floodplain filtration as additional treatment of secondary effluent. The capacity of floodplain filtration in Korea is circa 182,000,000 $m^3$/day and most of the rivers are estimated to have enough capacity of floodplain filtration to meet all the secondary effluent, indicating that this technology may be expected to make further improvements on river water quality. Furthermore, this method may also be applied to better the source-water quality for drinking water.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.26 no.1B
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• pp.79-88
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• 2006

In this study, a methodology is developed for flood runoff analysis considering the interaction between interior floodplain and channel. Riparian lowland is modeled as storage areas by HEC-RAS and is connected with main channel through gravity drainage structure and pumping stations. As a result, we were able to compute the difference between runoff into the interior floodplain and delayed runoff to main channel from interior floodplain. This allowed us to compute the storage change in the interior floodplain and corresponding inundation areas. Furthermore, the levee is modeled as a lateral structure and the flood from the main channel to interior floodplain is modeled by installing a weir on top of it. In addition, levee breach is also modeled so that flooding from main channel to interior floodplain can be considered. Computed flooding depth in the storage areas are compared with elevation to identify the inundated areas and flood maps can then be produced for a desired time or for the extent of flooding given a flooding depth. Output from this modeling effort can provide many useful information for flood planning such as flow depth in main channel, flooding depth and area in interior floodplain. The method was applied to Sapgyo river basin and the comparison with observed flood events showed that it can reproduce the observation fairly well, hence proving the utility of the method.

• Journal of the Korean Association of Geographic Information Studies
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• v.6 no.1
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• pp.132-142
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• 2003

A significant deficiency of most computer models used for stream floodplain analysis, is that the locations of structures impacted by flood waters, such as roads, buildings, and bridges, cannot be effectively compared to the floodplain location. The purpose of this study is the integration of the HEC River Analysis System(HEC-RAS) with ArcView geographic information system to develop a regional model for floodplain determination and representation. Also this study presents to enable two- and three-dimensional floodplain mapping and analysis in the ArcView. The methodology is applied to a Yeoju of Kyunggi-do, located in South Han River Basin. A digital terrain model is synthesized from HEC-RAS cross-sectional data and a digital elevation model of the study area. The flood plain data developed in ArcView was imported into HEC-RAS where it was combined with the field surveyed channel data in order to construct full floodplain cross sections that reflected accurate channel and overbank data for the HEC-RAS model. The flood plain limits could be expressed more accurately on ArcView by using water level data to be computed in HEC-RAS program. The computed water surface elevations and information of cross-section must be manually plotted in order to delineate floodplains. The resulting of this study provided a good representation of the general landscape and contained additional detail within the stream channel. Overall, the results of the study indicate that GIS combined with HEC-RAS is proven to be very useful and efficient for the automatic generation of flood maps, and an effective environment for floodplain mapping and analysis.

• Journal of The Geomorphological Association of Korea
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• v.24 no.4
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• pp.1-12
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• 2017

This study tried to reconstruct paleovegetation environments during the late Holocene with pollen analysis from archeological trenches at the right bank of Geumgang in Sejong-si. The lower hills was dominantly covered with pine trees, while alder trees and hygrophytes extended on the floodplain since 2,000yr BP. The pollen composition of Alnus dominance in the floodplain during the times is different from the general charateristics of Korean peninsula. Such a phenomenon is thought to be influenced by the fluvial process on the floodplain in the middle reaches of Geumgang around Sejong-si. Mihocheon and some tributaries join to Geumgang around Sejong-si, and the channel of Geumgang becomes narrow around the boundary between Sejong-si and Gongju-si. This narrow channel could attribute to the formation of extensive floodplain around Sejong-si. Moreover, human impacts such as agriculture appear continuously since 1,800yr BP.

• Proceedings of the KSRS Conference
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• v.2
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• pp.764-767
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• 2006

It can be important framework data to monitor the change of land-use pattern of river boundary in design and management of river. This study analyzed the change of land-use pattern of Gab- and Yudeung River using time-series aerial images. To do this, we carried out radiation and geometric correction of image, and estimated land-use changes in inland and floodplain. As the analysis of inland, the ratio of residential, commercial, industrial, educational and public area, that is urbanized element, increases, but that of agricultural area shows a decline on the basis of 1990. Also, Minimum Distance Method, which is a kind of supervised classification method, is applied to extract water-body and sand bar layer in floodplain. As the analysis of land-use, the ratio of level-upped riverside land and water-body increases, but that of sand bar decreases. These time-series land use information can be important decision making data to evaluate the urbanization of river boundary, and especially it gives us goodness in river development project such as the composition of ecological habitat.

• Ecology and Resilient Infrastructure
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• v.8 no.4
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• pp.212-222
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• 2021

In this study, the flow resistance coefficient was calculated considering the physical properties and distribution characteristics of floodplain vegetation, and the effect of floodplain vegetation distribution on flow characteristics was analyzed by reflecting it in a two-dimensional numerical simulation. The three-dimensional point clouds of vegetation acquired using ground lidar were analyzed to apply floodplain vegetation's physical properties to the existing formula for vegetation flow resistance calculation. The floodplain vegetation distribution in the modeling was divided into locally distributed and fully distributed conditions in the floodplain. As a result of the simulation of the study site, the flow resistance coefficient of floodplain vegetation was found to have a value of about five times or more compared to the flow resistance coefficient of the main channel bed when the design flood occurs based on Manning's n coefficient. Also, it affected the hydraulic characteristics in the main channel and floodplain.

• Ecology and Resilient Infrastructure
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• v.5 no.4
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• pp.199-209
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• 2018

In river design, consideration of bed shear stresses is necessary to secure stability of levee and floodplain. In this study distributions of bed shear stresses in compound open channels are analyzed through numerical simulation for various width and depth. LES solver in OpenFOAM is applied to 12 cases of compound channel shapes considering secondary flow which effects distributions of bed shear stresses. By the results time averaged velocity distributions, secondary currents, and distributions of bed shear stresses are analyzed. Overall distributions of bed shears in floodplain show that higher shear stresses are seen in left of floodplain and the shears decrease toward right of floodplain. However, high local variations in shear stresses are shown due to the secondary flow effects. In shallow floodplain, bed shear stresses show low value below 0.8 times of averaged bed shear. In deep floodplain, bed shear stresses show high value over 1.2 - 1.4 times of averaged bed shear.