• Journal of The Korean Society of Agricultural Engineers
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• v.58 no.1
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• pp.11-17
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• 2016

Dredging and land reclamation works has actively carried out for the efficient use of land and secure of agricultural and industrial site. During the reclamation, a portion of landfills are lost from the desired location due to a variety of causes. However, these causes has been rarely studied, and water flow velocity has a great influence on the movement of landfills. For the economical and efficient reclamation, it is important to predict the movement of landfills in water. In this paper, an experimental study was carried out to investigate the deposition distance according to the flow velocity and soil grain size. We have made a large open-channel apparatus that can reproduce a laminar flow, and the deposition test was carried out on the four grain size (0.638, 1.425, 3.375, 7.125 mm) and four flow velocity (0.1, 0.3, 0.5, 0.67 m/s) with high definition video recording. As a results, average deposition distance increased with the flow velocity, and its relationship is shown linearly. For the grain size, the average deposition distance were drastically increased as the grain size becomes smaller.

• Journal of Korea Water Resources Association
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• v.38 no.3 s.152
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• pp.223-233
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• 2005

In this study, a two-dimensional model for identifying areas of erosion and deposition over a basin was developed based on the mass balance principle in a distributed model. The program consists of three steps: (a) estimation of soil erosion; (b) determination of flow amount and direction; and (c) estimation of mass balance. Soil erosion was estimated with USLE. A single-direction (SF) and a multi-direction flow algorithm (MF) were applied to estimate slope length (L). The Maximum Downhill Slope Method (MDS) and the Neighborhood Method (NBH) were used to estimate the slope degree (S). Sediment transport resulting from eroded soil was estimated using Ferro's (1998) and Swift's (2000) sediment delivery ratio (DR). The model was validated by comparing the predicted sediment yields for three basins with measured data. The developed algorithm showed that Ferro's DR method combined with the MDS and MF produced the best agreement with the dredging records of three agricultural reservoir basins in Korea.

• Journal of Wetlands Research
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• v.8 no.3
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• pp.67-77
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• 2006

Sedimentological investigations on surface and suspended sediments were performed in Masan Bay of the South Sea in order to reveal recent changes in depositional environments concerning anthropogenic influence. Surface sediments had been classified as 3 sediment facies: mud, slightly gravelly mud, and gravelly mud. In general, mud facies with more than 60% of silt is predominant and slightly gravelly mud facies occurs at the watercourse of bay's central area. The silt-dominant mud faices appears to be predominant before and after dredging. Temperature and salinity changes during one tidal cycle for each season suggest that water columns were stratified without vertical mixing regardless of the season due to weak intensity of tide from the effect of geographical features. The effect of freshwater discharge from the land seems to be insignificant. The strongest current was observed during ebb tide in spring and autumn while observed during flood tide in summer and winter. Net sediment flux (fs) and net suspended sediment transport (Qs) for suspended sediment were determined by remaining drift developed here. Net suspended sediment transport loads were seaward with $62.02{\times}10^3kgm^{-1}$, $31.84{\times}10^3kgm^{-1}$ in spring and fall, respectively, and landward with $18.23{\times}10^3kgm^{-1}$, $3.22{\times}10^3kgm^{-1}$ in summer and winter, respectively.

• Journal of the Korean Society of Marine Environment & Safety
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• v.15 no.4
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• pp.345-354
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• 2009

The review of statements and coastal development characteristics in South Korea were diagnosed by the consultation on the coastal area utilization in Korea. The occupation and the use of public water were dominated by installation of coastal structure and seawater supply and drainage whereas the reclamation areas were predominantly utilized for developing industrial complex, harbor, fishing port and road. The occupation and the use were dominant in western coast, but reclamation was dominant in southern coast of Korea. The number of utilization cases was particularly greater in Jeonnam, Gyeongnam, and Gyeonggi Province including Incheon. The number of the statements reviews increased by more than 200 cases in 2008 compared with 2007, and most of them were the simple statements. The statements related to ocean disposal of dredged sediment, reclamation, dredging sediment, seawater supply and drainage, and marine sand mining were submitted for review. Coastal utilization was especially active in the regions of seawater quality criteria I and II. In particular, special management sea areas designated under the relevant marine regulations were utilized mostly by reclamation for developing harbor, fishing port and coastal structure. Development activities in national parks comprised primarily structure installation and coastal maintenance. In the fisheries resources protection areas, 40% of the total cases accounted for coastal maintenance, 31% for structure installation, and 16% for seawater supply and drainage. In addition, alternative plans for the improvement in policies and system of marine environmental impact assessment were suggested to enhance the function and confidence of the consultation on the coastal area utilization in Korea.

• Journal of Korean Society of Environmental Engineers
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• v.34 no.9
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• pp.597-603
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• 2012

To investigate the effects of weir construction on sediment characteristics of river bed, we conducted sediments sampling on the 9 locations near the weir, Kangchun, Yuju and Ipo in Namhan-River. Physical and chemical characteristics of sediments were analyzed by measuring particle size distribution, water content, Ignition loss, COD (Chemical Oxyzen Demand), TOC (Total Organic Carbon), TP (Total Phosphorus), SRP (Soluble Reactive Phosphorus) and TN (Total Nitrogen). Particle classification of all three weir sediments showed sandy loam that was caused by the river bed dredging. Due to the presence of weir, Ignition loss, COD, TOC, TP, SRP and TN showed similar trend such as the concentrations of upward weir had higher than those of downward weir. For the case of SRP concentration and C/N ratio, however, there is not much difference in the sediment characteristics compared to the those of sediments before weir construction. Therefore, It can be predicted that there are little effects of weir construction on sediment characteristics. However, weir construction could influence water quality of the river by controlling the transport and the accumulation of suspended materials from rainfall. Therefore, more intensive monitoring is required to examine the magnitude and patterns of sediment accumulation which could influence overlying water quality.

• Journal of Wetlands Research
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• v.15 no.3
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• pp.423-430
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• 2013

An algorithm to allow shoreline movement during numerical experiment on sediment transport, deposition or resuspension for general coastal morphology is proposed here. The bed slope near shoreline, i.e. mean sea level, is influenced by bed material, tidal current, waves, and wave-induced current, but has been reported to remain within a stable range. Its annual variation is not large, either. The algorithm is adjusting the bathymetry, if the largest bed slope within shoreline band exceeds a given bed slope due to continuous erosion at zones below the shoreline. This algorithm automatically describes retreat of shoreline caused by erosion, when used within a numerical system. The algorithm was tested to a situation which includes a continuous dredging at a point, and showed satisfactory development of concentric circle contours. Next, the algorithm was tested to another situation which includes sinking of eroded part of bed plate, and produced satisfactory results, too. Finally, the algorithm was tested to a movable-bed laboratory experimental conditions. The shoreline movement behind detached breakwater was reasonably reproduced with this algorithm.

• Journal of Korea Water Resources Association
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• v.52 no.2
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• pp.163-172
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• 2019

The linear and cross-sectional shapes of the natural river channel are subjected to continuous changes in time and space due to the interaction with the flow of water and sediment transport. This study aims to investigate the morphological characteristics and change patterns of river channel quantitatively for the middle reach of Nakdong River, which has undergone large scale riverbed dredging and construction work, as Four Major River Restoration Project. A series of bathymetry and near-river survey has been conducted to obtain the detailed terrain information for the study area. The properties related to the linear and cross-sectional characteristics of river channel have been calculated based on the filed survey data and analyzed with comparing the survey data obtained in 2012 for the project completion. Since there has not been enough time for meaningful terrain change to take place, it was not possible to extract special tendency in the degree and aspect of terrain change. However, it is necessary to make regular examinations to the patterns and degree of river channel change using the proposed methodology.

• Journal of the Korean Society of Marine Environment & Safety
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• v.20 no.2
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• pp.143-156
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• 2014

We reviewed investigation status on turbidity plume in the statement of marine environmental survey(2008 to 2012) associated with marine sand extraction projects. The survey statement from seven marine sand extraction sites (extraction area of Southern EEZ, extraction area of Western EEZ, relocation zone in the Western EEZ, sea area under jurisdiction of Taean-gun, sea area under jurisdiction of Ansan City, and two discrete sea areas under jurisdiction of Ongjin-gun) in the nearshore and offshore of Korea showed that in situ observations were carried out for the dispersion and transport of suspended sediments on two areas (One is a extraction area in the EEZs, the other is an area of coastal sites). However, sampling station and range have not been selected considering physical, geographical factors (tide, wave, stratification, water depth, etc.) and weather conditions (wind direction and velocity, fetch, duration, etc). Especially turbidity plumes originating from three sources, which include suspended sediments in overflow(or overspill) discharged from spillways and reject chutes of dredging vessel, and resuspended sediments from draghead at the seabed, may be transported to a far greater distance outside the boundary of the extraction site and have undesirable impacts on the marine environment and ecosystem. We address that behaviour of environmental pollutants such as suspended solids, nutrients, and metals should be extensively monitored and diagnosed during the dispersion and transport of the plume. Finally we suggest the necessity to supplement the current system of the sea area utilization consultation and establish the combined guidelines on marine sand extraction to collect basic data, to monitor cumulative effects, and to minimize environmental damages incurred by the aftermath of sand extraction.

• Journal of Environmental Impact Assessment
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• v.31 no.3
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• pp.141-160
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• 2022

The harbor construction projects can lead to various marine environmental problems including habitat degradation and loss, marine water pollution, change of flow patterns, erosion, scour, sedimentation, and so on. The EIA is a measure to prevent various environmental problems in advance from examining and minimizing the environmental impacts before the proposed developments are implemented. In addition, institutions reviewing EIA reports have made efforts to conduct scientific and standardized EIA by applying EIA guidelines for each project. This study aims to create a EIA guideline focusing on the harbor construction projects. Based on the review comments of the harbor construction EIA reports for the past 13 years (2009-2021) and the EIA guidelines of different types of projects, we identified the marine environmental problems and provided the appropriate guideline. This guideline summarizes and presents the contents which must be reviewed in the baseline condition survey, impact assessment, mitigation, and post-environmental impact investigation in the fields of marine fauna and flora, marine physics, and marine water and sediment quality. In the case of a baseline condition survey of marine fauna and flora, a method for selecting survey points considering the characteristics of sea area and project was presented. When estimating the impact of marine fauna and flora, we presented methods for predicting the impact on them due to the spread of suspended sediments and the damage to benthic habitats due to dredging and reclamation. In consideration of the characteristics of the sea area, we divided the survey items of the marine physics into essential items and supplementary items. In predicting the impact of marine physics, various methods for major issues such as seawater circulation, suspended sediment and bottom sediment transport, water temperature and salinity diffusion, seawater exchange, wave transformation, harbor tranquility, and shoreline change were presented. The research results will contribute to protect the marine environment by inducing more systematic and scientific surveys, impact assessments, and mitigation in the EIA process.