San Francisco Bay Long-Term Management Strategy (LTMS) for Dredging and Disposal PDF Download
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Author: Allen M. Teeter
Publisher:
ISBN:
Category : Dredging
Languages : en
Pages : 100
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Book Description
Author: Allen M. Teeter
Publisher:
ISBN:
Category : Dredging
Languages : en
Pages : 100
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Book Description
Author: Sheung Yan Sueann Lee
Publisher:
ISBN:
Category :
Languages : en
Pages :
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Book Description
The long-term evolution of shallow intertidal zones is of particular interest in light of efforts to restore coastal marshes. Factors that affect that rate of accretion or erosion of a marsh include current speeds, wind waves, tides and sediment load. These forcings change with time and vary on different time scales, and for any particular marsh the importance of each forcing may be different. Observations indicate that shallow intertidal basins tend to be characterized by a bimodal distribution of water depths into higher marshplain and lower mudflats. For shallow intertidal marshes, wind waves and tidal currents would both affect the deposition and erosion of sediments. It is hypothesized that for a shallow intertidal marsh with significant wind effects, wind waves will cause increased turbulence that enhances resuspension of sediment, leading to lower mudflats rather than higher marshplains. In this project, an attempt is made to study the factors that affect sediment deposition and resuspension, and the variability of these factors with time. Field data was collected for two weeks at a tidal wetlands restoration site, the Sonoma Baylands, California. Two locations within the field site with different wind fetches are compared to show the impact of wind on turbidity. At each site, wind speed, current velocity, wave, and turbidity data was collected. Turbidity is used as a proxy for suspended sediment concentration. Relative wave height and wave shear stress were found to be most correlated with turbidity. At the site with shorter fetch, current shear stress was almost as important as wave shear stress, but it was not significantly correlated at the site with longer fetch and larger waves. The importance of wind waves for sediment will help develop understanding of the mechanisms and factors affecting the transition of a shallow coastal region into either a marshplain accreting to mean high-high water level, or eroding into mudflat. The results of this study will be useful in determining the importance of wind waves on sedimentation, thus helping in developing strategies for restoring or protecting tidal marshes. To further study the process of sediment transport in San Francisco Bay, a three-dimensional coupled hydrodynamic, wind wave and mud suspension model SUNTANS was developed. The model was calibrated to existing meteorological, current, salinity, wave and sediment conditions. The model was found to be in general agreement with existing patterns of salinity, wave and sediment distribution. Higher sediment concentrations were generally found in locations of higher wind, shallow depths, complicated bathymetry, and/or down wind locations, in line with the established understanding of wind-induced sediment resuspension together with current induced erosion and advective transport.
Author: California State Coastal Conservancy
Publisher:
ISBN:
Category : Hydrodynamics
Languages : en
Pages :
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Book Description
Recommended action: Authorization to disburse up to $293,000 to the Regents of University of California and $565,000 to Stanford University for the development of a San Francisco Bay hydrodynamic and sediment transport model and a modeling framework for San Francisco Bay.
Author: Megan Ann Lionberger
Publisher:
ISBN:
Category :
Languages : en
Pages : 220
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Book Description
Author: Megan A. Lionberger
Publisher:
ISBN:
Category : Sediment transport
Languages : en
Pages : 24
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 96
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Book Description
Field data analysis was used to examine suspended sediment transport in Central San Francisco Bay, and to develop and verify a two-dimensional numerical fine-grained sediment transport model. This study concerned the dispersion and fate of disposed dredged material in Central San Francisco Bay, California. The 1992 monitoring survey spanned a 2-week period in June, and used three boat-mounted acoustic Doppler current profiling (ADCP) systems to obtain repeated cross-sectional transects near the Golden Gate, the entrance to South Bay, and Richmond Point. Between acoustic transects, water samples were obtained over depth for salinity, total suspended material (TSM) concentration, and particle size determinations. Acoustic backscatter data were used to produce correlated suspended material concentration and flux fields. Discrete measurements were fit to empirical discharge and suspended flux models and integrated over a neap-spring-neap tidal sequence to estimate net transport. There was an observed net transport of suspended sediment seaward at the Golden Gate over the neap to spring sampling period. The total net transport was 188,000 metric tonnes seaward over 14 lunar days. Fluxes during the ebb flows averaged 44% greater than the flood flows, and instantaneous strong-ebb TSM fluxes were often more than twice those on flood tidal phases. Suspended sediment concentrations increased during the strongest part of the ebb at all Central Bay sampling ranges. Wind forcing did not appear imponant to this process. Suspended concentrations quickly returned to normal levels after the passage of peak ebb flows. Spatial variability in the TSM fields was relatively large. The ADCP backscatter intensity measurements correlated well with TSM especially on the Golden Gate range where a broadband unit was employed.
Author: Honghai Li
Publisher:
ISBN:
Category : Erosion
Languages : en
Pages : 12
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Book Description
Author: Virginia R. Pankow
Publisher:
ISBN:
Category : Dredging
Languages : en
Pages : 90
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Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 88
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Book Description
A combination of physical and numerical models was used to simulate the hydrodynamic, circulation, and sediment transport characteristics of San Francisco and San Pablo bays. This simulation was done in response to a request by the US Army Engineer District, San Francisco, to develop a modeling tool that can define the fate of dredged material disposed at the Alcatraz disposal site. Keywords: Computer simulation, Dredged material disposal models, Mathematical models, Dredged material management. (KT).
Author:
Publisher:
ISBN:
Category :
Languages : en
Pages : 124
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Book Description
Field data were collected on currents, salinities, and suspended sediments intensively over a lunar day and sporadically over a fortnight in September 1988 for the purpose of identifying transport processes and conditions in central San Francisco Bay and for numerical model verification. Conditions were typical of a low freshwater inflow summer season in this area. A two- dimensional horizontal finite element model was applied and verified to field and physical hydraulic model data. The model is intended for future long-term studies of the fate of dredged material dispersed from the Alcatraz disposal site. Keywords: Field tests; Currents/salinity; Transport properties; Water flow; Sediment transport; Mass flux; Numerical modeling; San Francisco Bay; Sedimentation/ deposition; Total suspended matter.
