Chapter 12 Field observation and modeling of suspended fine sediment load in Ariake Bay, Japan

Nakagawa, Yasuyuki; Yoshida, Hisafumi

doi:10.1016/s1568-2692(08)80014-9

Cited by 4 publications

(3 citation statements)

References 8 publications

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“…Also, gravitational circulation can contribute significantly to the tidally averaged transports, whereas near-bottom suspension layers can affect the transports through damping of the turbulence. The relative importance of these mechanisms in a number of estuaries has been discussed by many authors (Postma 1967;Van Leussen 1991;Le Hir et al 2001;Vinzon and Mehta 2001;Dyer et al 2002a;Bass et al 2005;Nakagawa and Yoshida 2008).…”

Section: Longitudinal Variations Of the Fine-grained Sediment Transportsmentioning

confidence: 99%

Macroflocs, fine-grained sediment transports, and their longitudinal variations in the Ems Estuary

Leussen

2011

Ocean Dynamics

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Field measurements have been carried out to obtain more quantitative knowledge on the longitudinal distribution of the fine-grained sediment dynamics in the Ems Estuary. Both the short-term (time scale < tidal period) and the long-term (tidally averaged) fine-grained sediment transports have been investigated. It is shown that the shortterm erosion/sedimentation cycles are most characteristic and are the building blocks for the ultimate long-term transports. Herein, the macroflocs play a key role. The macroflocs had sizes in the range of 200 to 700 μm, sometimes more than 1 mm, and survived high current velocities. The settling velocities were in the range of 0.5 to 8 mm/s. Turbulence intensities and suspended sediment concentration are of utmost importance for the settling properties of the sediment, but the "flocculation ability" of the suspended sediment is shown to be of equal importance. The suspended sediment concentration is only important at low levels of turbulence. At high levels of turbulence, the limiting properties of turbulence dominate. It is demonstrated that the surface properties of the suspended sediment particles are of prime importance for the flocculation ability of the water/sediment mixture, as do the sizes of the resuspended microflocs. Special attention is given to the longitudinal distribution of the sizes and settling properties of the macroflocs as well as of the sediment transports. The flocculation ability was shown to vary almost one order of magnitude along the estuary. These higher flocculation abilities in the direction of higher salinities are responsible for the increase of the sizes of the macroflocs in the seaward direction. Therefore, notwithstanding the low suspended sediment concentrations at the seaward boundary of the Ems Estuary, large macroflocs and corresponding high settling velocities were observed in this area. It explains that, in the Ems Estuary, no distinct effect was determined of the suspended sediment concentration on the settling properties of the suspended macroflocs.

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Section: Longitudinal Variations Of the Fine-grained Sediment Transportsmentioning

confidence: 99%

Macroflocs, fine-grained sediment transports, and their longitudinal variations in the Ems Estuary

Leussen

2011

Ocean Dynamics

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“…Model parameters for erosion and deposition processes are based on the study by Yano et al (2014) 11) . They used Nakagawa and Yoshida 13) values for the parameters: i.e., w=0.0018 m/s, M=3.3x10 4 kg/m 2 /s, and τcr,d =1.0 N/m 2 . They considered that re-suspension of bottom sediment occurs in Minamata Bay where tidal current is weak normally, so they set the τcr,e, in small value 0.001 N/m 2 .…”

Section: (3) Boundary Conditions and Model Parametersmentioning

confidence: 99%

Impact of Reclamation Project on Mercury-Contaminated Sediment Transport from Minamata Bay into the Yatsushiro Sea

Fathya

Yano²,

Matsuyama

et al. 2016

Journal of Japan Society of Civil Engineers, Ser. B2 (Coastal E

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Minamata Bay which suffered from a major disaster called "Minamata Disease" has already remediated from 1977 to 1990 by carried out highly mercury (Hg) contaminated sediment and reclaimed it in the bay area. Furthermore, many studies reported that the mercury has reached Yatsushiro Sea, the outer part of Minamata Bay. It can be assumed that the sediment transport still occurs from remaining Hg concentration even after the remediation project. In order to investigate it, we try to simulate the transport of sediment contaminated by Hg from Minamata Bay to the Yatsushiro Sea with different coastal morphology on before and after the reclamation projects.Sediment transport and tidal flow with rectangular variable grid both before and after reclamation conditions around the Yatsushiro Sea and Minamata Bay are simulated by DELFT3D. The initial bottom sediment thickness of 1m is set in the only inner side of the bay and six months simulation results for both before and after reclamation area are compared. The change of hydrodynamic condition inside Minamata Bay due to the remediation project gives a slight change in sediment transport pattern. It is estimated that after the reclamation, the sediment transport moves slower than before it due to the change of its magnitude of velocity above the seabed. As an important result, it is clarified that a change of the amount of bottom sediment which can be re-suspended in Minamata Bay caused by the topographical change can also affect the pattern. Also, this result suggests that the southern part of Yatsushiro Sea can be influenced by sediment contaminated by higher Hg included before the reclamation project.

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“…Typical values of E 0 range from 0.01 to 0.5 gm −2 s −1 [e.g. Winterwerp and Kesteren, 2004] and sometimes it was reported as small as 4.5× 10 −4 gm −2 s −1 [Nakagawa, 2005]. However, no universal formulation has yet been developed.…”

Section: Deposition and Resuspension Processesmentioning

confidence: 99%

Modeling of Mud Accumulation and Bed Characteristics in Tokyo Bay

Rasmeemasmuang

Sasaki

2008

Coastal Engineering Journal

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This paper presents the modeling of mud accumulation in Tokyo Bay. The model consists of hydrodynamic, wave hindcasting, bed shear stress and multi-class sediment sub-models in order to simulate the sediment associated processes both in the water body and bed layer. The present model accounts for sediment transport, settling, deposition, resuspension, accumulation and burial sedimentation processes, and it is capable to reproduce the accumulation of muddy sediments. Following the concept of multi-class particle model, the bed characteristics, i.e. the spatial distributions of particle size and the water content ratio in bed materials, were computed and qualitatively verified with field investigation data. The computed spatial variation in mud accumulation rate, particle size distribution and water content ratio were consistent with field data. Some discrepancies were identified and discussed.

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Chapter 12 Field observation and modeling of suspended fine sediment load in Ariake Bay, Japan

Cited by 4 publications

References 8 publications

Macroflocs, fine-grained sediment transports, and their longitudinal variations in the Ems Estuary

Macroflocs, fine-grained sediment transports, and their longitudinal variations in the Ems Estuary

Impact of Reclamation Project on Mercury-Contaminated Sediment Transport from Minamata Bay into the Yatsushiro Sea

Modeling of Mud Accumulation and Bed Characteristics in Tokyo Bay

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