• Title/Summary/Keyword: bottom sediment

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An Experimental Study on The Uncertainty of Suspended Sediment Pickup on Slope by Solitary Wave (고립파에 의한 경사면에서의 부유사 제승의 불확실성에 관한 실험적 연구)

  • Cho, Jae Nam;Jeong, Seok Il;Lee, Seung Oh
    • Journal of the Korean Society of Safety
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    • v.32 no.6
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    • pp.61-67
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    • 2017
  • Suspended sediment transport plays principal roles in morphological process of natural coastals. It is needed to understand the reason why interaction characteristics of solitary wave and suspended sediment. The present study shows that suspended sediment pickup derived on solitary wave celerity. The 2D prismatic open channel length is 12 m, width is 0.8 m, height is 0.75 m and slope is 1/6. Generation of solitary wave is used by rapidly opening the sluice gate. Bottom surface sediments are laid movable slope section by 0.03 m thickness and experimental sediments are used anathracite and jumoonjin sand. Techniques of suspended sediment pickup rate are designed equipment ASC(Absorptive Suspended sediment Collector). It could directly absorb 5 points suspended sediment by channel water depth. Solitary wave celerity is measued by ADV(Acoustic Doppler Velocimeter). Mounted two video cameras(Model No. : Sony, HDR-XR550) are used to image processing of suspended sediment concentration and turbidity. Suspended sediment pikcup rate(Einstein, 1950) is analyzed to nondimensionalization based on solitary wave celerity. The suspended sediment pickup rate is suggested that more effective plunging breaking type than spilling. The results indicates fundamental suspended sediment transport mechanism between solitary wave celerity and suspended sediment pickup based on laboratory experiments. Finally, the present study suggests that suspended sediment pickup rate by solitary wave is used only characteristics of sediment and solitary wave celerity.

Coastal Circulation and Bottom Change due to Ocean Resort Complex Development

  • Kim, Pill-Sung;Lee, Joong-Woo;Kim, Jeong-Seok
    • Journal of Navigation and Port Research
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    • v.36 no.7
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    • pp.585-590
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    • 2012
  • On the basis of the potentials for the growth of local economy and the result of investigation of the ocean space development status, an ocean resort complex was proposed at the small harbor with a parallel beach in the east coast of Korea. As the development plan needs to reclaim the noticeable amount of coastal water area together with the applied shore facilities, it is necessary to analyze their impacts. Here, it was intended to analyze the coastal environment change such as water circulation and bottom change because of the development plan. A horizontal two-dimensional numerical model was applied to represent the combined impact of wind waves and tidal currents to sediment transport in that coastal region. Based on the result of 30 days tidal current simulations considering major four tidal components of $M_2$,$S_2$,$K_1$ and $O_1$ for the upper and lower boundaries and wind field data, bottom change was discussed. Flow velocities were not changed much at outer breakwater of Yangpo harbor. Bottom was eroded by maximum 1.7m after construction but some locations such as lee side of outer breakwater and some islets near the entrance shows isolated accretions. Although it needs more field observations for bottom change in the period of construction, the numerical calculation shows that there exist small impacts near the entrance area and coastal boundaries because of the development.

137Cs, 40K and 210Po in abiotic components of aquatic ecosystems two rivers in the Can Gio biosphere reserve, Vietnam

  • Ilya G. Sidorov ;Nataliya N. Tereshchenko ;Andrey A. Korotkov;Olga D. Chuzhikova-Proskurnina;Nguyen Trong Hiep ;Aleksandr V. Trapeznikov
    • Nuclear Engineering and Technology
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    • v.54 no.11
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    • pp.4265-4271
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    • 2022
  • Determination of 137Cs, 40K and 210Po in water, bottom sediments and suspended matter of river systems of the Can Gio Biosphere Reserve, Vietnam was carried out. The average activity concentration of 137Cs in waters of Ca Gau and Long Tau was 0.89 ± 0.14 and 1.08 ± 0.15 Bq m-3 and was comparable to the levels of this radioisotope in waters of the East Sea. The activity concentration of 137Cs in bottom sediments was 2.23 ± 0.81 and 3.63 ± 1.24 Bq kg-1. The activity concentration of 137Cs in water and bottom sediments could be characterized as low. So, the water areas of the Ca Gau and Long Tau rivers could be attributed to areas with insignificant pollution by technogenic radionuclides. The 210Po activity concentration in bottom sediments of the Ca Gau and Long Tau rivers ranged from 9.2 ± 1.2 to 25.5 ± 2.1 Bq kg-1, which is typical for river bottom sediments. Such values indicate the absence of anthropogenic enhancement of the entry of this radionuclide into the Can Gio river systems. The 40K activity concentration varied within 467 ± 42-651 ± 39 Bq kg-1 and represented typical values of potassium content in the bottom sediments of coastal water bodies, subject to a significant influence of the lithogenic component of suspended matter.

Dissolved Oxygen at the Bottom Boundary Layer of the Ulleung Basin, East Sea (동해 울릉분지 해저 경계면의 용존산소)

  • Kang, Dong-Jin;Kim, Yun-Bae;Kim, Kyung-Ryul
    • Ocean and Polar Research
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    • v.32 no.4
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    • pp.439-448
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    • 2010
  • General consensus on typical vertical profile of dissolved oxygen in the Ulleung Basin is that dissolved oxygen concentration beyond 300 m decreases with increasing depth. However, the results of our observations in 2005 and 2006 revealed three different dissolved oxygen distribution types in the deep layer of the Ulleung Basin. The first type showed oxygen concentration decreasing with increasing depth (Type-1), the second showed oxygen concentration decreasing very sharply near the bottom boundary layer but constant in the bottom adiabatic layer (Type-2), the final was of the oxygen minimum layer above the bottom boundary layer (Type-3). Type-2 was the most common pattern in the Ulleung Basin. Type-1 was most common close to the Japan Basin, including the Ulleung Interplane Gap, while Type-3 was found around Dok do. Oxygen Consumption Rate (OCR) at surface sediment estimated using the dissolved oxygen distribution at the bottom boundary layer was $0.2{\sim}5.8\;mmol{\cdot}m^{-2}d^{-1}$, which coincided with OCR from direct sediment incubation. This implies that organic matter decomposition at surface sediment may play an important role in dissolved oxygen distribution patterns at the bottom boundary layer of the Ulleung Basin.

A Study on Geology and Sediment Characteristics in Danghang Bay Area, Gyeongnam (경남 당항만 해역의 지질 및 퇴적층 특성에 관한 연구)

  • Kim, Jin-Hoo;Kim, Sung-Bo;Lee, Young-Hyun;Kim, Chan-Soo;Ryu, Choon-Kil
    • Journal of Advanced Marine Engineering and Technology
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    • v.34 no.8
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    • pp.1203-1211
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    • 2010
  • In order to study geology and sediment characteristics in Danghang Bay area, surface geological survey, SBP (sub-bottom profiler) survey, and sediment analysis were conducted. Danghang Bay area has a closing coast surrounded by land, and surface layer are covered by mud and sandy mud. Sedimentary facies of the surface layer consists of Mm and Mms facies. A SBP seismic survey shows that gas bearing sediments might be spread throughout the sediment layers, so that it seems to be hard to find acoustic basement and gas seeps are easily found throughout the survey lines. The gas trapped in the sediments may be related to the high organic contents of the sediment, and the thick mud layer may restrain the gas from releasing.

Development of Calculation System of the Sediment for Efficient Management of the Reservoir (저수지의 효율적 관리를 위한 퇴적량 산출 시스템 개발)

  • Park, Joon-Kyu;Kang, Joon-Mook
    • Journal of the Korean Society of Surveying, Geodesy, Photogrammetry and Cartography
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    • v.26 no.3
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    • pp.285-292
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    • 2008
  • The establishment of the scheme which could be managed the national reservoir efficiently and consideration of a variable management scheme by the application of a new technique for it is very important for the improvement of national service quality and application of related techniques. In this study, sediment information which was accumulated in the reservoir for a long time and occasioned the decrease of pondage and increase of water pollution was constructed rapidly and accurately using GPS, sub bottom profiler and echo sounder. And the calculation system of sediment was efficiently designed through the applications of 2D and 3D spatial information processing techniques. As a results, the calculation system of sediment which was accomplished a various functions was developed and a basic information of management for the reservoir which was constructed quite a while ago was presented.

Variation of Physical Characteristic of Tidal Flat's Environment by Water Level Change (수위변동에 따른 갯벌의 물리적 환경특성의 변화)

  • Park, Jong-Hwa
    • Journal of the Korean Society of Environmental Restoration Technology
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    • v.2 no.3
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    • pp.1-9
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    • 1999
  • This paper described the results of the characteristics of the near-bottom flow and field analysis of the tidal flats sediment. It was the aim of this paper to grasp current flow of tidal flat's environment and influence factor for environmental change forecast of tidal flats. Field measurement of water velocity, water elevation, bed materials test, and temperature distribution of tidal flat were conducted. Thereafter, current flow, turbidity and temperature distribution of tidal flat sediment have been discussed. The field research results showed that the fluctuating velocity near the seabed before and after its appearance at low tide was strongly affected by the wind wave. The resuspension of the sea-bottom sediment took place with great intensity before and after the appearance of the seabed at low tide. Both the sea water level and the weather condition were a significant influential factors. Such as, temperature and turbidity just on the surface and the shallow layer of seabed sediments were varied largely with time and weather conditions, but that its deeper layers was almost constant. Temperature on the seabed sediments was strongly influenced by irradiance and water depth. The temperature variation of the tidal flat and the variation characteristics of the current flow and turbidity depend greatly on the inhabiting environment of the tidal flat benthic organism.

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Radiolarian Biostratigraphy and Paleoceanographic Study from the Northeast Equatorial Pacific (북동태평양지역의 방산충 생층서 및 고해양환경 연구)

  • Kim, Ki-Hyune;Park, Jeoung-Hee
    • Ocean and Polar Research
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    • v.21 no.2
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    • pp.127-136
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    • 1999
  • Radiolarian assemblages from KODOS area were analyzed in order to understand the biostratigraphy and paleoceanography of deep-sea sediment from the Northeast Equatorial Pacific. The sediment core was divided into two or three units on the basis of the chemical and physical properties. In the upper sediment, mixtures of Quaternary and Tertiary radiolarians are found indicating active reworking processes. Dissolution of radiolarians seem to increase with depth. Radiolarians are seldom in Unit III presumably due to dissolution and corrosion. The middle part of unit I appears to correspond to Collosphaera invaginata Zone (0.21 Ma). Unit II belongs to Collosphaera tuberosa Zone. Based on the absence of Stylatractus universus, we estimate its age to be younger than 0.42 Ma. Based on our analyses of radiolarians in Unit I and II, we estimated the age of unit III as Tertiary, particularly from Oligocene to Miocene. There may to be hiatuses of more than 3 My from late Miocene to Pliocene, which probably resulted from erosion and dissolution by the Antarctic Bottom Water Sedimentation rates during Quaternary range from 0.15 to 0.50 mm/ky with significant variabilities among stations. Radiolarians in the study area were mostly warm-water species.

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Development of Sedimentary Sequence in the Masan Bay, South Sea of Korea (마산만 퇴적층서 발달 특성)

  • Choi, Dong-Lim;Lee, Tae-Hee
    • Ocean and Polar Research
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    • v.29 no.4
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    • pp.411-418
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    • 2007
  • We studied the bottom morphology and sedimentary environments of the Masan Bay using high-resolution Chirp seismic profiles and sediments data. According to deep-drilled core samples (up to 20 m thick) penetrated into the weathered rock basement, the sediments consist largely of three sediment types: the lower sandy gravel facies (Unit I) of 1-4 m in thickness, the middle sandy mud and/or muddy sand facies(Unit II) of 1-2 m thick and the upper mudfacies (Unit III) of over 10 m in thickness. The sedimentary column above the acoustic basement can be divided into two major sequences by a relatively strong mid-reflector, which show the lower sedimentary sequenc e(T) with parallel to subparallel internal reflectors and the upper sedimentary sequence(H) with free acoustic patterns. Acoustic basement, the lower sedimentary sequence (T), and the upper sequence (H) are well correlated with poorly sorted massive sandy gravels (Unit I), the sand/mud-mixed sediment (Unit II), and the muddy facies(Unit III), respectively. The acoustic facies and sediment data suggest that the Masan bay is one of the most typical semi-enclosed coastal embayments developed during the Holocene sea-level changes. The area of the Masan Bay reduced from about $19\;km^2$ in 1964 to about $13\;km^2$ in 2005 by reclamation, and its bottom morphology changed as a result of dredging of about $2{\times}10^7\;m^3$.

3.5kHz seismic images of the gas-charged shallow sediment at Kwangyang Bay and the Yeosu Sound on the southern coast of Korea (광양만과 여수해만의 가스함유 표층퇴적물의 3.5kHz 탄성파 영상)

  • 오진용
    • Economic and Environmental Geology
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    • v.33 no.3
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    • pp.239-246
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    • 2000
  • The 3.5kHz sub-bottom profiling was carried out over both Gwangyang Bay and the Yeo Sound . High -resolution digital images of uppermost sediment layers are obtained from the field data which were originally recorded in analog mode. Most prominent feature along the acoustic profiles is the chaotic reflections which imply the presence of shallow gas within the silty sediments. In the western part of Gwangyang Bay, the gas-charged sediments are assoicated with the acoustic turbidity of the blanket type. Across the Seomjin Delta in the eastern part of Gwangyang Bay, the gas-charged seismic facies are observed just beneath the sea bottom. In the western Yeoul Sound , the gassy seiments occur widely , whereas it is rare in the eastern counterpart with the <30-m-deep channel. We postulate that this gas was biogenetically produced within the organic-rich deposits.

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