Seasonal, spring-neap, and tidal variation in cohesive sediment transport parameters in estuarine shallows

Journal of Geophysical Research: Oceans
By: , and 

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Abstract

Numerical models for predicting sediment concentrations and transport rely on parameters such as settling velocity and bed erodibility that describe sediment characteristics, yet these parameters are rarely probed directly. We investigated temporal and spatial variation in sediment parameters in the shallows of San Pablo Bay, CA. Flow, turbulence, and suspended sediment data were measured at sites located at 1 and 2 m below mean lower low water (MLLW) from November 2013 through April 2015, supplemented by monthlong periods in 2011, 2012, and 2016. Maximum current velocities were 0.40–0.47 m s-1 at these depths; the strongest currents decreased to 0.27–0.34 m s-1 during neap periods. Winters 2013–2014 and 2014–2015 experienced strong drought conditions, limiting the potential for seasonal impact on sediment conditions during this experiment. Despite this, the more storm‐influenced site showed clear changes during the winter: the roughness parameter decreased from 10−4 to 10−5 m, from hydrodynamically rough to smooth conditions, and bed erodibility increased by an order of magnitude. Median settling velocity was 2.05·10−4 m s-1; it varied twofold within a tidal cycle, decreasing as current velocity grew during flood and ebb. This tidal control on floc size affected settling velocity on the spring‐neap timescale, possibly driving a spring‐neap oscillation in erodibility. Our findings highlight variation in sediment dynamics that is commonly ignored in numerical models and the need for field observations to ground truth ongoing modeling efforts.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Seasonal, spring-neap, and tidal variation in cohesive sediment transport parameters in estuarine shallows
Series title Journal of Geophysical Research: Oceans
DOI 10.1029/2018JC014825
Volume 124
Issue 11
Year Published 2019
Language English
Publisher Wiley
Contributing office(s) Pacific Coastal and Marine Science Center
Description 20 p.
First page 7265
Last page 7284
Country United States
State California
Other Geospatial San Pablo Bay
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