Details:

Journal Title:
Journal of Geophysical Research: Oceans
Personal Author:
Eidam, E. F. ; Sutherland, D. A. ; Ralston, D. K. ; Conroy, T. ; Dye, B.
Eidam, E. F. ; Sutherland, D. A. ; Ralston, D. K. ; Conroy, T. ; Dye, B. Less -
NOAA Program & Office:
NOS (National Ocean Service) ; OCM (Office for Coastal Management)
NOS (National Ocean Service) ; OCM (Office for Coastal Management) Less -
Description:
Estuaries worldwide have experienced modifications including channel deepening and intertidal reclamation over several centuries, resulting in altered fine sediment routing. Estuaries respond differently based on preexisting geometries, freshwater and sediment supplies, and extents and types of modification. The Coos Bay Estuary in Oregon is a relatively small estuary with complex geometry that has been extensively modified since 1865. A sediment transport model calibrated to modern conditions is used to assess the corresponding changes in sediment dynamics. Over ∼150 years, channel deepening (from ∼6.7 to 11 m), a 12% increase in area, and a 21% increase in volume have led to greater tidal amplitudes, salinity intrusion, and estuarine exchange flow. These changes have reduced current magnitudes, reduced bed stresses, and increased stratification, especially during rainy periods. Historically, fluvially derived sediment was dispersed across broad, deltaic-style flats and through small tidal channels. Now, river water and sediments are diverted into a dredged navigation channel where an estuarine turbidity maximum (ETM) forms, with modeled concentrations >50 mg/L and measured concentrations >100 mg/L during discharge events. This “new” ETM supplies sediment to proximal embayments in the middle estuary and the shallow flats. Overall, sediment trapping during winter (and high river discharges) has increased more than two-fold, owing to increased accommodation space, altered pathways of supply, and altered bed stresses and tidal asymmetries. In contrast to funnel-shaped estuaries with simpler geometries and river-channel transitions, these results highlight the importance of channel routing together with dredging in enhancing sediment retention and shifting pathways of sediment delivery.
Keywords:
[+]
Dredging Estuaries Sediments (Geology) Estuarine turibity maximum
Source:
Journal of Geophysical Research: Oceans, 126, e2020JC016771
DOI:
https://doi.org/10.1029/2020JC016771
Document Type:
Journal Article
Funding:
Grant no. NA14NOS4190145
Place as Subject:
Coos Bay Estuary (Or.)
Rights Information:
Other
Compliance:
Submitted
Main Document Checksum:
[+]
urn:sha256:786f17c2cd455ef0b5c338e3fc69f058c6d87c9423d394651952bbab88fb8596
Download URL:
https://repository.library.noaa.gov/view/noaa/34003/noaa_34003_DS1.pdf
File Type:

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