Trapping of suspended sediment by submerged aquatic vegetation in a tidal freshwater region: Field observations and long-term trends

Estuaries and Coasts
By: , and 

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Abstract

Widespread invasion by non-native, submerged aquatic vegetation (SAV) may modify the sediment budget of an estuary, reducing the availability of inorganic sediment required by marshes to maintain their position in the tidal frame. The instantaneous trapping rate of suspended sediment in SAV patches in an estuary has not previously been quantified via field observations. In this study, flows of water and suspended sediment through patches of invasive SAV were measured at three tidally forced, freshwater sites, all located within the Sacramento-San Joaquin Delta in California. An acoustic Doppler current profiler deployed from a roving vessel provided velocity and backscatter data used to quantify fluxes of both water and suspended sediment. Sediment trapping efficiency, defined as instantaneous net trapped flux divided by incident flux, was positive in 24 of 29 cases, averaging + 5%. Coupled with 3 years of measured sediment flux data at one site, this suggests that trapping averages 3.7 kg m−2 year−1. This estimate compares favorably with the mean mass accumulation rate of 3.8 kg m−2 year−1 estimated from dated sediment cores collected at the study sites. Long-term measurements made upstream reveal a strong negative trend (− 1.8% year−1) in suspended sediment concentration, and intra-annual changes in both suspended sediment concentration and percent fines. The large footprint and high spatial density of invasive SAV coupled with declining sediment supply are diminishing downstream suspended sediment concentrations, potentially reducing the resiliency of marshes in the Delta and lower estuary to future sea-level rise.

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Additional publication details

Publication type Article
Publication Subtype Journal Article
Title Trapping of suspended sediment by submerged aquatic vegetation in a tidal freshwater region: Field observations and long-term trends
Series title Estuaries and Coasts
DOI 10.1007/s12237-020-00799-w
Edition Online First
Year Published 2020
Language English
Publisher Springer
Contributing office(s) California Water Science Center
Country United States
State California
Other Geospatial Sacramento-San Joaquin River Delta
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