• Journal of Korean Society on Water Environment
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• v.27 no.2
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• pp.218-227
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• 2011

The objective approach for assessment of stream naturalness is an essential part of the stream restoration project. This study proposes the methodology for the assessment of stream naturalness considering physical, biological and chemical factors. Physical factors consists of riffle and pool, river bed material, bank protection, floodplain vegetation and levee materials; biological factors are benthic macroinvertebrate, KSI (Korean Saprobic Index), and IBI (Index of Biological Integrity) and chemical factors are pH, DO (dissolved oxygen), and TP (total phosphorus). This procedure is applied to the Mokgamcheon. As a result, the downstream of Mokgamcheon (zone I) needs the prompt improvement of stream naturalness, compared to the others (zone II and III). This evaluation technique will be an effective tool to quantify the stream naturalness and can be used to set the target of stream restoration project.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.2
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• pp.1-6
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• 2012

The objective of this study is to analyze the flood inundation in a low-lying rural area. The study watershed selected for this study includes the Il-Pae and Ahn-Gok watersheds. It is located in the Namyangju, Korea and encompasses $3.64km^2$. A major flood event that occurred in July 2011 was chosen as the case for the flood inundation analysis. The Hydrologic Engineering Center's Hydrologic Modeling System (HEC-HMS) and River Analysis System (HEC-RAS) were used to simulate flood runoff and water surface elevation at each cross-section, respectively. The watershed topographic, soil, and land use data were processed using the GIS (Geographic Information System) tool for the models. The contribution to the total flood volume was estimated based on the results simulated by HEC-HMS and HEC-RAS. The results showed that the overflow discharge from the Il-Pae stream constituted 80% of the total flood volume. The contributions of rainfall falling directly on the inundation area and overflow discharge from the Ahn-Gok stream were 15 % and 5 %, respectively. The simulation results in different levee scenarios for the Ahn-Gok stream were also compared. The results indicated that the levee could reduce the flood volume a little bit.

• Journal of the Korean Association of Geographic Information Studies
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• v.12 no.3
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• pp.88-100
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• 2009

An inundation analysis was performed on Hwapocheon, one of the tributaries of Nakdong River, which was inundated by heavy rain in August, 2002 with overtopping and levee break. The results of the developed model, 2D diffusion wave inundation analysis model, was compared with inundation trace map as well as inundation depth in terms of time and maximum inundated area calculated from FLUMEN model for the assessment of model applicability. The results from the developed model showed high fitness of 88.61% in comparison with observed data. Also maximum inundated area and spatial distribution of inundation zone were also found to be consistent with the results of FLUMEN model. Therefore, inundation zone and maximum inundation area calculated over a period of time by adopting 2D diffusion wave inundation analysis model can be used as a database for identifying high risk areas of inundation and establishing flood damage reduction measures.

• Ecology and Resilient Infrastructure
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• v.10 no.1
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• pp.1-10
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• 2023

Developmental technique is mixed bio-polymer and riprap to protect the breaking of a levee. Purpose of new technique is restraint from scour and failure of bankside. Technique of this research can apply shore protection and embankment overflow reinforcement works. Because This technique is easy for construction. In order to apply the technique in fields, It is need to conduct the test-bed or real scale experiment study for stability-guaranteed. In case of embankment overflow reinforcement works, It is difficult to conduct test bed in the field. Real scale experiment was conducted in River Experiment Center. Purpose of real scale experiment is to reappear disaster scene by embankment overflow and verify restraint from scour and failure about the technique. In this experiment results, We can find the strength effect of mixed bio-polymer and riprap.

• Journal of Korea Water Resources Association
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• v.41 no.6
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• pp.619-628
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• 2008

Bank protection is a structure constructed to protect directly embankment breakage and erosion by river flow. Traditionally, the type of bank protection has been decided by practitioner's subjective and empirical judgement, which often causes problems after construction. Recently, however, it becomes important to consider not only physical protection but also environment. Various types of bank protection for environment-friendly river are now available. Thus, there is a need for more objective and quantitative decision method for bank protection work. This study adopts the analytic hierarchy process (AHP) to improve the objectiveness in the decision of bank protection work. Criteria for stability, economy, construction, environment are identified and a standardized process is presented for field application. With the proposed method, one can prioritize various bank protection works and make the optimal decision. We believe that the method can serve as a useful tool for river engineers in practice.

• The Journal of Engineering Geology
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• v.23 no.2
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• pp.161-170
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• 2013

We analyzed the effect of changing water level and turbidity on plants that serve to maintain slope stability on levees. In this experiment, soil collected from upstream of Imha Dam was placed in a water tank and planted with river plants of the Salix species: Salix gracilistyla, S. koreensis, and S. glanduosa. Plant regrowth was analyzed stage-by-stage during a recovery period. In addition, we assessed the tolerance of the plants to concentrated torrential rainfall and examined their recovery rates. The results indicate that in the case of these three Salix species, which are the most prevalent river plants in Korea, stem growth is arrested following serious damage and high turbidity. The possibility of regrowth was very low during the 20-day non-submerged recovery period. Although the number of leaves initially decreased during this period, subsequent regrowth was reasonably high: recovery in S. gracilistyla, S. koreensis, and S. glanduosa was up to 59.3%, 251.3%, and 148.4% respectively, compared with the initial condition.

• 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.

• 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 Wetlands Research
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• v.12 no.3
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• pp.21-37
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• 2010

The abiotic factors and the vegetation naturalness of the 13 tributary wetlands around Namgang-River were assessed to investigate the present state and to present the conservation counter plan for the wetland ecosystem of the tributaries. Assessment indices for the abiotic factors were estimated based on the dominant land use types of the riparian zone, ecological function of the upper levee, levee slope structure, artificiality and utilization intensity of the waterfront, artificiality of the revetment structure, diversity of the substrate, and severance of the transverse. The assessment index of Omi-cheon is the highest among 13 tributaries. The second was Banseong-cheon and third was Hyangyang-cheon, followed by Nabul-cheon and Yeongcheon-gang and Sugok-cheon, Jungchon- cheon, and Daegok-cheon in their order and Munsan-cheon got the lowest assessment index. Assessment indices for the vegetation naturalness were estimated based on the vegetation diversity, exotic species dominance, annual herb dominance, naturalness and peculiarity of the vegetation, and species diversity. The assessment index of Omi-cheon is the highest among 13 tributaries. The second was Sugok-cheon and third was Banseong-cheon, followed by Yeongcheon-gang, Jungchon- cheon, Jinae-cheon, Nabul-cheon, and Jisu-cheon in their order, and Yonga-cheon got the lowest assessment index. The grades of the stream naturalness were estimated based on the the naturalness indices for the abiotic factors and the vegetation naturalness. The grades of Omi-cheon is the highest among 13 tributaries as the grade I. Those of Banseong-cheon, Sugok-cheon, Yeongcheon-gang, Nabul-cheon and Jungchon-cheon, Hyangyang-cheon, Jinae-cheon, Jisu-cheon, Daegok-cheone, and Munsan-cheon and Doksan-cheon were grade II in their order, and Yonga-cheon got the lowest as the grade III. It was suggested that restoration of the simple and flat substrate, create the natural vegetation on the levee slope constructed with concrete or stone wall, and rehabilitation of the eco-bridge were demanded to improve the grades of the stream naturalness through the restoration of the tributaries for the diverse aquatic wildlife, high vegetation diversity and species diversity with the vegetation consisted of perennial herbs and trees.

• Journal of the Korean association of regional geographers
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• v.2 no.2
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• pp.197-204
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• 1996

We attempt to classifing method of micro-landform on the alluvial plain, such as natural-levee, backmarsh and alluvial fan, using false color composite of Landsat Thematic Mapper image. The study area is Kumho River Basin on the southeastern part of Korea peninsula. The most effective image for micro-landform classification is the false color composite of band 2, 3 and 4 with blue, green and red filtering. The most favorable time is the middle third of November, because of the density differentiation of green vegetation in most great. In this time the paddy field on the back-marsh is bare by rice harvesting. But on the natural levee the green vegetation, such as vegetables and lower herbs under fruit tree, remain relatively more. On the alluvial fan, the green vegetation condition is medium. For the verification of the micro-landform classification, we employed the field survey and grain size analysis of the deposition of each micro-landform on the sample area. It is clarified that the classification method of micro-landform on the alluvial plain using the Landsat TM image is relatively useful.