Model-based interpretation of sediment concentration and vertical flux measurements in a shallow estuarine environment

Limnology and Oceanography
By: , and 

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Abstract

A one-dimensional numerical model describing tidally varying vertical mixing and settling was used to interpret sediment concentrations and vertical fluxes observed in the shoals of South San Francisco Bay by two acoustic Doppler velocimeters (ADVs) at elevations of 0.36 m and 0.72 m above bed. Measured sediment concentrations changed by up to 100 g m−3 over the semidiurnal tidal cycle. These dynamics were dominated by local resuspension and settling. Multiple particle class models suggested the existence of a class with fast settling velocities (ws of 9.0 × 10−4 m s−1 in spring and 5.8 × 10−4 m s−1 in fall) and a slowly settling particle fraction (ws of <1 × 10−7 m s−1 in spring and 1.4 × 10−5 m s−1 in fall). Modeled concentrations of slowly settling particles at 0.36 m were as high as 20 g m−3 during fall and varied with the spring-neap cycle while fine sediment concentrations in spring were constant around 5 g m−3. Analysis of in situ water column floc size distributions suggested that floc properties in the lower part of the water column were most likely governed by particle-size distribution on the bed and not by coagulation, validating our multiple particle size approach. A comparison of different sediment bed models with respect to model performance, sensitivity, and identifiability suggested that the use of a sediment erosion model linear in bottom shear stress τb (E = M (τb − τc)) was the most appropriate choice to describe the field observations when the critical shear stress τc and the proportionality factor M were kept constant.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Model-based interpretation of sediment concentration and vertical flux measurements in a shallow estuarine environment
Series title Limnology and Oceanography
DOI 10.1002/lno.10047
Volume 60
Issue 2
Year Published 2015
Language English
Publisher Wiley
Contributing office(s) Pacific Coastal and Marine Science Center
Description 19 p.
First page 463
Last page 481
Country United States
State California
Other Geospatial South San Francisco Bay
Online Only (Y/N) N
Additional Online Files (Y/N) N