• Title/Summary/Keyword: Erosion and deposition distribution

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Sedimentologic Characteristics of Tidal Flat Sediments after the Construction of Sea Dyke in Kwangyang Bay, South Coast of Korea (호안 건설 후 광양만 조간대 퇴적물의 퇴적학적 특성)

  • Ryu, Sang-Ock;Sin, Yong-Sik
    • Journal of the Korean earth science society
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    • v.27 no.6
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    • pp.659-669
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    • 2006
  • In Kwangyang Bay, the south coast of Korea, surface sediments and sedimentation rates have been investigated to understand the distribution and variation of tidal flat sediments after the construction of sea dyke. The mean grain size of the surface sediments during autumn is coarser, and decrease from winter to summer except for temporarily coarsening in the early summer. The depositional processes are prevalent in spring, while erosional processes are dominant in summer and autumn. This seasonal variation of sedimentary processes show similar results monitored from 2001 to 2003 before the construction of sea dyke. In the northern area of the bay, net annual sedimentation rates show similar results monitored from 2001 to 2003 before the construction of sea dyke. However, in the western area of the bay, net annual sedimentation rates change from erosion-dominated to deposition-dominated environments. It is considered that the western area of the bay is changed to erosion-dominated environments, as a result of the changes of hydrodynamic conditions, caused by sea dyke construction.

Sediment Fluxes in Shelf Seas Modelling and Monitoring

  • Prandel, David
    • Journal of the korean society of oceanography
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    • v.37 no.3
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    • pp.144-153
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    • 2002
  • This is a review paper, assessing progress reported in a Special Issue (Prandle and Lane, 2000) of Coastal Engineering focusing on simulation of SPM in the North Sea, against issues over a diverse range of shelf seas and their coastal margins. The broad objectives of reproducing the characteristics of sediment fluxes off an open coast and relating these to tidal and wave forcing were achieved. However, accurate computation of these fluxes remains sensitive to largely empirical coefficients used in determining erosion and deposition rates. Bed roughness strongly influences both these coefficients and the associated near-bed current magnitudes (including wave impact thereon). Bed roughness can change significantly over a tidal cycle and dramatically over seasons or in the course of a major event. Accurate simulation of sediment fluxes on a day-to-day basis is constrained by dependency on the initial distribution of mobile sediments. The latter depends on rates and locations of original sources and the time history of preceding events. Remote sensing via aircraft could provide data for assimilation into such models to circumvent these constraints. The approaches described here can be readily applied to other coastal regions to indicate the likely distributions and pathways of known sediment sources. However quantitative simulations will require an associated observational programme. A subsequent stage is to understand the evolving balance between the forecasted sediment movement - the resulting morphological adjustments and thence modifications to the prevailing tidal current and wave regimes.

Derivation Method of Rating Curve and Relationships for Flow Discharge-Total Sediment at Small-Midium Streams in Agrarian Basin (농경유역 중소하천에서 유량과 총유사량의 관계식 유도방법)

  • Lee, Jong-Seok;Kim, Chi-Gon;You, Eui-Geen
    • The Journal of the Korea Contents Association
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    • v.15 no.8
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    • pp.544-555
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    • 2015
  • This study aims to derivate of the relationship and rating curve for the flow discharge-total sediment using the measured field data from the main points of small-medium stream reaches in agrarian basin. The total sediment of measured data are obtained by bed load added to suspended load which analyzed using the particle size distribution curve of sieve test and the dry or the filtration method from the collected samples by samplers (DH-48, D-74 and BLH-84, BL-84) at the stream bed and the depth-averaged concentration, respectively. These field data had been collected from August 2012 to September 2014 at the seven measuring stations of the national-local channel reaches of the four study streams in the Nonsan river systems of agrarian basin. As a result, the relationships and the rating curve for the flow discharge-total sediment are derived as a function pattern of power law by analyzing on a distribution characteristic of the database set and it will be used as a useful tool to analyze erosion, deposition, and transportation in theoretical research as well as in practical application of the hydraulic sedimentation engineering.

Changes of Sedimentary Environments in the Southern Tidal Flat of Kanghwa Island (강화 남부 갯벌의 퇴적환경 변화)

  • Woo, Han-Jun;Je, Jong-Geel
    • Ocean and Polar Research
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    • v.24 no.4
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    • pp.331-343
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    • 2002
  • The southern tidal flat of Kanghwa Island with an area of approximately $90km^2$ is one of the biggest flats on the west coast of Korea. Surface sediments for sedimentary analyses were sampled at 83 stations in August 1997, September 1999 and August 2000. The very poorly-sorted mud sediments were predominant in the eastern part of the tidal flat, whereas the poorly-sorted sand-mud mixed sediments were dominant in the western part. The area of muddy sediment distribution diminished, but that of sandy mud sediment extended to southeastward tidal flat for three years. In the western part of tidal flat, deposition occurred during the period of spring to summer, whereas erosion occurred in winter. Sediment accumulation rates during three years indicated that the sediments deposited continuously in the eastern part of tidal flat, whereas eroded in the western part of tidal flat. Recently, construction of artificial structures such as new airport, island-connecting bridges and dikes near the tidal flat might change tidal current and river flow pattern. In order to reduce the ecological damage and to preserve tidal-flat environment, it is necessary to Investigate long-term impacts on sedimentary environment and ecology.

Morphologic Response of Gravel Beach to Typhoon Invasion - A Case Study of Gamji Beach Taejongdae in Busan (태풍 내습 시 자갈 해빈의 지형반응 - 부산 태종대 감지 해빈의 사례)

  • Lee, Young Yun;Chang, Tae Soo
    • Journal of the Korean earth science society
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    • v.41 no.1
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    • pp.19-30
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    • 2020
  • To understand the impact of typhoons on Gamji gravel beach Taejongdae in Busan, we carried out beach profiling using a VRS-GPS system and a Drone photogrammetry for the typhoons 'Kong-rey' invaded in October 2018 and 'Danas' in July 2019. In addition, grain sizes are analyzed to investigate the overall distribution pattern of gravels on the beach, and the beach topography is surveyed periodically to confirm the recovery rate of the beach. Grain-size analysis reveals that mean gravel sizes, in general, become finer from -6.2Φ to -5.4Φ towards the east in the seashore line direction. Variation in mean sizes is obviously observed in the cross-shore direction. Gravels in the swash zone are relatively fine about -4.5Φ in size and equant in shape, whereas the coarse and oblate gravels ranged from -5Φ to -6Φ are found in the berm. Gamji gravel beach particularly has two lines of berms: a lower berm situated facing beach and an upper berm about 10 m landward. After the typhoon Kong-rey passed by, about 1.4 m of severe erosion in upper berm occurred, and the berm eventually disappeared. On the backshore of the upper berm about 50 cm of erosion took place so that the elevation became lower. However, tangible erosion was not observed in the lower berm. When typhoon Danas hit, rated as mild storm, both upper and lower berm were eroded out. However, about 50 cm of deposition occurred only in the backshore. Only three days later, the new lower berm was formed, meaning that sedimentation rate must be high. This result indicates that Gamji gravel beach is recovered very fast from erosion caused by the typhoons when it is under the fair-weather condition even though beach morphology changes dramatically in a short period of time. Gravel beach is estimated to be or evaluated very resilient to typhoon erosion.

Measurement and Analysis of Bed Shear Stresses in Compound Open Channels using the Preston Tube (프레스톤튜브를 이용한 복단면 하도의 하상전단응력 측정 및 분석)

  • Lee, Du Han;Kim, Myounghwan;Kim, Won;Seo, Il Won
    • Ecology and Resilient Infrastructure
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    • v.4 no.4
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    • pp.207-215
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    • 2017
  • Hydraulic issues such as flow resistance, side wall correction, sediment, erosion and deposition, and channel design have close relation with distribution of bed shear stresses but the measurement of the distribution of bed shear stresses is not easy. In this study the Preston tube which makes possible relatively simple measurement of bed shear stresses is used to analyze the characteristics of bed shear distribution in compound open channels with different depth ratio. The Preston tubes are made and calibrated to develop the calibration formula and then they are applied to measure bed shear stress distribution in 5 cases depth ratio condition of compound channels. The results are compared with former experiment data, and characteristics of bed shear stress distributions are studied with different channel scales and Reynolds numbers. Although bed shear distributions with depth ratio show overall agreement with former studies, some differences are verified in bed shear variation, formation of inflection point in main channel, and distribution near floodplain junction which are due to high Reynolds number. Through the study applicability of the Preston tubes are also verified and characteristics of bed shear distribution in compound channels are suggested with Reynolds number and depth ratio.

Vegetation structure and distribution characteristics of Symplocos prunifolia, a rare evergreen broad-leaved tree in Korea

  • Kim, Yangji;Song, Kukman;Yim, Eunyoung;Seo, Yeonok;Choi, Hyungsoon;Choi, Byoungki
    • Journal of Ecology and Environment
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    • v.44 no.4
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    • pp.275-285
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    • 2020
  • Background: In Korea, Symplocos prunifolia Siebold. & Zucc. is only found on Jeju Island. Conservation of the species is difficult because little is known about its distribution and natural habitat. The lack of research and survey data on the characteristics of native vegetation and distribution of this species means that there is insufficient information to guide the management and conservation of this species and related vegetation. Therefore, this study aims to identify the distribution and vegetation associated with S. prunifolia. Results: As a result of field investigations, it was confirmed that the native S. prunifolia communities were distributed in 4 areas located on the southern side of Mt. Halla and within the evergreen broad-leaved forest zones. Furthermore, these evergreen broad-leaved forest zones are themselves located in the warm temperate zone which are distributed along the valley sides at elevations between 318 and 461 m. S. prunifolia was only found on the south side of Mt. Halla, and mainly on south-facing slopes; however, small communities were found to be growing on northwest-facing slopes. It has been confirmed that S. prunifolia trees are rare but an important constituent species in the evergreen broad-leaved forest of Jeju. The mean importance percentage of S. prunifolia community was 48.84 for Castanopsis sieboldii, 17.79 for Quercus acuta, and 12.12 for Pinus thunbergii; S. prunifolia was the ninth most important species (2.6). Conclusions: S. prunifolia can be found growing along the natural streams of Jeju, where there is little anthropogenic influence and where the streams have caused soil disturbance through natural processes of erosion and deposition of sediments. Currently, the native area of S. prunifolia is about 3300 ㎡, which contains a confirmed population of 180 individual plants. As a result of these low population sizes, it places it in the category of an extremely endangered plant in Korea. In some native sites, the canopy of evergreen broad-leaved forest formed, but the frequency and coverage of species were not high. Negative factors that contributed to the low distribution of this species were factors such as lacking in shade tolerance, low fruiting rates, small native areas, and special habitats as well as requiring adequate stream disturbance. Presently, due to changes in climate, it is unclear whether this species will see an increase in its population and habitat area or whether it will remain as an endangered species within Korea. What is clear, however, is that the preservation of the present native habitats and population is extremely important if the population is to be maintained and expanded. It is also meaningful in terms of the stable conservation of biodiversity in Korea. Therefore, based on the results of this study, it is judged that a systematic evaluation for the preservation and conservation of the habitat and vegetation management method of S. prunifolia should be conducted.

Study of Soil Erosion for Evaluation of Long-term Behavior of Radionuclides Deposited on Land (육상 침적 방사성 핵종의 장기 거동 평가를 위한 토사 침식 연구)

  • Min, Byung-Il;Yang, Byung-Mo;Kim, Jiyoon;Park, Kihyun;Kim, Sora;Lee, Jung Lyul;Suh, Kyung-Suk
    • Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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    • v.17 no.1
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    • pp.1-13
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    • 2019
  • The accident at the Fukushima Dai-ichi Nuclear Power Plant (FDNPP) resulted in the deposition of large quantities of radionuclides over parts of eastern Japan. Radioactive contaminants have been observed over a large area including forests, cities, rivers and lakes. Due to the strong adsorption of radioactive cesium by soil particles, radioactive cesium migrates with the eroded soil, follows the surface flow paths, and is delivered downstream of population-rich regions and eventually to coastal areas. In this study, we developed a model to simulate the transport of contaminated sediment in a watershed hydrological system and this model was compared with observation data from eroded soil observation instruments located at the Korea Atomic Energy Research Institute. Two methods were applied to analyze the soil particle size distribution of the collected soil samples, including standardized sieve analysis and image analysis methods. Numerical models were developed to simulate the movement of soil along with actual rainfall considering initial saturation, rainfall infiltration, multilayer and rain splash. In the 2019 study, a numerical model will be used to add rainfall shield effect by trees, evaporation effect and shield effects of surface water. An eroded soil observation instrument has been installed near the Wolsong nuclear power plant since 2018 and observation data are being continuously collected. Based on these observations data, we will develop the numerical model to analyze long-term behavior of radionuclides on land as they move from land to rivers, lakes and coastal areas.

Distribution Patterns and Provenance of Surficial Sediments from Ieodo and Adjacent Sea (이어도와 주변 해역의 표층퇴적물 분포와 퇴적물 기원지)

  • Chang, Tae Soo;Jeong, Jong Ok;Lee, Eunil;Byun, Do-Seong;Lee, HwaYoung;Son, Chang Soo
    • Journal of the Korean earth science society
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    • v.41 no.6
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    • pp.588-598
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    • 2020
  • The seafloor geology of Ieodo, a submerged volcanic island, has been poorly understood, although this place has gained considerable attention for ocean and climate studies. The main purpose of the study is to understand and elucidate types, distribution patterns and provenance of the surficial sediments in and around the Ieodo area. For this purpose, 25 seafloor sediments were collected using a box-corer, these having been analyzed for grain sizes. XRD (X-ray Diffraction) analysis of fine-grained sediments was conducted for characterizing clay minerals. The peak of Ieodo exists in the northern region, while in the southern area, shore platforms occur. The extensive platform in the south results from severe erosion by strong waves. However, the northern peak still survived from differential weathering. Grain size analyses indicated that gravels and gravelly sands with skeletons and shells were distributed predominantly on the volcanic apron and shore platform. Muddy sediments were found along the Ieodo and the adjacent deeper seafloor. Based on the analysis of clay mineral composition, illites were the most abundant in fine muds, followed by chlorites and kaolinites. The ratio plots of clay minerals for the provenance discrimination suggested that the Ieodo muds were likely to be derived from the Yangtze River (Changjiang River). As a consequence, gravels and gravelly sands with bioclastics may be supplied from the Ieodo volcanic apron by erosion processes. Wave activities might play a major role in transportation and sedimentation. In contrast, fine muds were assumed to be derived from the inflow of the Yangtze River, particularly in summer. Deposition in the Ieodo area is, therefore, probably controlled by the inflow from the Changjiang Dilute Water and summer typhoons from the south.

한강하류지형면의 분류와 지형발달에 대한 연구 (양수리에서 능곡까지)

  • Park, No-Sik
    • Journal of the Speleological Society of Korea
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    • no.68
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    • pp.23-73
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    • 2005
  • Purpose of study; The purpose of this study is specifically classified as two parts. The one is to attempt the chronological annals of Quaternary topographic surface through the study over the formation process of alluvial surfaces in our country, setting forth the alluvial surfaces lower-parts of Han River area, as the basic deposit, and comparing it to the marginal landform surfaces. The other is to attempt the classification of micro morphology based on the and condition premising the land use as a link for the regional development in the lower-parts of Han river area. Reasons why selected the Lower-parts of Han river area as study objects: 1. The change of river course in this area is very serve both in vertical and horizontal sides. With a situation it is very easy to know about the old geography related to the formation process of topography. 2. The component materials of gravel, sand, silt and clay are deposited in this area. Making it the available data, it is possible to consider about not oかy the formation process of topography but alsoon the development history to some extent. 3. The earthen vessel, a fossil shell fish, bone, cnarcoal and sea-weed are included in the alluvial deposition in this area. These can be also valuable data related to the chronological annals. 4. The bottom set conglometate beds is also included in the alluvial deposits. This can be also valuable data related to the research of geomorphological development. 5. Around of this area the medium landform surface, lower landform surface, pediment and basin, are existed, and these enable the comparison between the erosion surfaces and the alluvial surfaces. Approach : 1. Referring to the change of river beds, I have calculated the vertical and horizontal differences comparing the topographic map published in 1916 with that published in 1966 and through the field work 2. In classifying the landform, I have applied the method of micro morphological classification in accordance with the synthetic index based upon the land conditions, and furthermore used the classification method comparing the topographic map published in 1916 and in that of 1966. 3. I have accorded this classification with the classification by mapping through appliying the method of classification in the development history for the field work making the component materials as the available data. 4. I have used the component materials, which were picked up form the outcrop of 10 places and bored at 5 places, as the available data. 5. I have referred to Hydrological survey data of the ministry of Construction (since 1916) on the overflow of Han-river, and used geologic map of Seoul metropolitan area. Survey Data, and general map published in 1916 by the Japanese Army Survbey Dept., and map published in 1966 by the Construction Research Laboratory and ROK Army Survey Dept., respectively. Conclusion: 1. Classification of Morphology: I have added the historical consideration for development, making the component materials and fossil as the data, to the typical consideration in accordance with the map of summit level, reliefe and slope distribution. In connection with the erosion surface, I have divided into three classification such as high, medium and low-,level landform surfaces which were classified as high and low level landform surfaces in past. furthermore I have divided the low level landform surface two parts, namely upper-parts(200-300m) and bellow-parts(${\pm}100m$). Accordingly, we can recognize the three-parts of erosion surface including the medium level landform surface (500-600m) in this area. (see table 22). In condition with the alluvial surfaces I have classified as two landform surfaces (old and new) which was regarded as one face in past. Meamwhile, under the premise of land use, the synthetic, micro morphological classification based upon the land condition is as per the draw No. 19-1. This is the quite new method of classification which was at first attempted in this country. 2. I have learned that the change of river was most severe at seeing the river meandering rate from Dangjung-ni to Nanjido. As you seee the table and the vertical and horizontal change of river beds is justly proportionable to the river meandering rate. 3. It can be learned at seeing the analysis of component materials of alluvial deposits that the component from each other by areas, however, in the deposits relationship upper stream, and between upper parts and below parts I couldn't always find out the regular ones. 4. Having earthern vessel, shell bone, fossil charcoal and and seaweeds includen in the component materials such as gravel, clay, sand and silt in Dukso and Songpa deposits area. I have become to attempt the compilation of chronicle as yon see in the table 22. 5. In according to hearing of basemen excavation, the bottom set conglomerate beds of Dukso beds of Dukso-beds is 7m and Songpa-beds is 10m. In according to information of dredger it is approx. 20m in the down stream. 6. Making these two beds as the standard beds, I have compared it to other beds. 7 The coarse sand beds which is covering the clay-beds of Dukso-beds and Nanjidobeds is shown the existence of so-called erosion period which formed the gap among the alluvial deposits of stratum. The former has been proved by the sorting, bedding and roundness which was supplied by the main stream and later by the branch stream, respectively. 8. If the clay-beds of Dukeo-bed and Songpa-bed is called as being transgressive overlap, by the Eustatic movement after glacial age, the bottom set conglomerate beds shall be called as being regressive overlap at the holocene. This has the closest relationship with the basin formation movement of Seoul besides the Eustatic movement. 9. The silt-beds which is the main component of deposits of flood plain, is regarded as being deposited at the Holocene in the comb ceramic and plain pottery ages. This has the closest relationship with the change of river course and river beds.