sediment

Seasonality of Retreat Rate of a Wave-Exposed Marsh Edge

ariela — Tue, 10 Sep 2024 22:59:06 +0000

Seasonality of Retreat Rate of a Wave-Exposed Marsh Edge ariela Tue, 09/10/2024 - 15:59

Document Category

Scientific Reports

Author(s)

Date

2024-07

Summary

Abstract

Wave-driven erosion of marsh boundaries is a major cause of marsh loss, but little research has captured the effect of seasonal differences on marsh-edge retreat rates to illuminate temporal patterns of when the majority of this erosion is occurring. Using five surface models captured over a study year of a marsh with a steep escarped boundary in South San Francisco Bay, we find a pronounced seasonal signal, where rapid marsh retreat in the spring and summer is driven by a strong sea breeze but little change is found in the marsh-edge position in the fall and winter. We found accretion in the mudflat transition region close to the marsh boundary in the calmer seasons however, suggesting intertwined morphodynamics of mudflats and the eroding marsh-scarp. We observed large spatial heterogeneity in retreat rates within seasons, but less on longer (annual and decadal) timescales. The relationship between marsh-edge retreat rates and properties of the wave field nearby is explored and contextualized against extant relationships, but our results speak to the difficulty in addressing spatial erosion/accretion variability on short (seasonal) timescales with simple models.

Key Points

A unique seasonal data set exposes strong seasonality in marsh-edge retreat, with rapid retreat during warm periods with strong sea breeze
There is large variation in retreat rates across the marsh seasonally but more uniform retreat rates on annual and decadal timescales
Digital surface models provide insight into erosion and accretion simultaneously across the marsh-mudflat system

Keywords

Pond Complex

Eden Landing

Content available here

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023JF007468

Continuous Suspended Sediment Monitoring in South and Lower South San Francisco Bay: Year Two (2023) Report

ariela — Thu, 08 Aug 2024 16:56:03 +0000

Continuous Suspended Sediment Monitoring in South and Lower South San Francisco Bay: Year Two (2023) Report ariela Thu, 08/08/2024 - 09:56

Document Category

Scientific Reports

Author(s)

San Francisco Estuary Institute

Date

2024-07

Summary

Executive Summary
This report provides a project update for year two of a three-year collaboration between the San
Francisco Bay Nutrient Management Strategy (NMS), San Francisco Bay Regional Monitoring Program,
and South Bay Salt Pond Restoration Project, to estimate high frequency suspended sediment
concentration (SSC) in San Francisco Bay (SFB). Through its role in monitoring water quality in SFB, the
NMS maintains an array of autonomous sondes that record high frequency (15-minute) water column
turbidity, amongst a suite of other environmental parameters. Turbidity data from these monitoring
sites was combined with discrete SSC samples to create a bay-wide turbidity-SSC calibration, allowing
for estimates of high frequency SSC. The calibration for 7 of these sites was performed using a linear
mixed effect model (LMM), which leverages similarities in the turbidity-SSC relationship between sites
while allowing for potential differences. An additional turbidity-only sensor was deployed at an 8th site
along with discrete SSC collection, with this calibration performed via least squares linear
regression. Both models showed reasonable agreement between turbidity and SSC, with R2 = 0.62 for
the LMM, and R2 = 0.72 for the regression performed at the turbidity-only site.
Using these calibrations, we created continuous 15-min SSC datasets at all 8 locations, representing 1
channel, 4 shoal, and 3 slough sites. These calibrations are considered preliminary and will be finalized
as part of the final year 3 report after SSC sample collection is completed. For these datasets, only
turbidity data less than 110% of the maximum calibration value were converted to SSC. In total, SSC
estimates were generated for ~90-99% of the data record at the water quality monitoring sites and 68%
of the record at the turbidity-only station.

This work was funded by the South Bay Salt Pond Restoration Project, the Regional Monitoring Program
for Water Quality in San Francisco Bay, and the San Francisco Bay Nutrient Management Strategy.

Suggested citation:
Mourier, L.; Montgomery, L.; Volaric, M.; Chelsky, A.; Senn, D. 2024. Continuous Suspended Sediment
Monitoring in South and Lower South San Francisco Bay: Year Two (2023) Report. SFEI Contribution No.
1188. San Francisco Estuary Institute: Richmond, CA

Keywords

Pond Complex

Alviso

Eden Landing

Ravenswood

Sediment deposition, erosion, and bathymetric change in San Francisco Bay, California, 1971–1990 and 1999–2020

ariela — Tue, 10 Oct 2023 21:59:54 +0000

Sediment deposition, erosion, and bathymetric change in San Francisco Bay, California, 1971–1990 and 1999–2020 ariela Tue, 10/10/2023 - 14:59

Document Category

Scientific Reports

Author(s)

Theresa A. Fregoso

Amy C. Foxgrover

Bruce E. Jaffe

Date

March 31, 2023

Summary

Bathymetric change analyses document historical patterns of sediment deposition and erosion, providing valuable insight into the sediment dynamics of coastal systems, including pathways of sediment and sediment-bound contaminants. In 2014 and 2015, the Office for Coastal Management, in partnership with the National Oceanic and Atmospheric Administration (NOAA) Office of Coastal Management, provided funding for new bathymetric surveys of large portions of San Francisco Bay. A total of 93 bathymetric surveys were conducted during this 2-year period, using a combination of interferometric sidescan and multibeam sonar systems. These data, along with recent NOAA, U.S. Geological Survey (USGS), U.S. Army Corps of Engineers, and private contractor surveys collected from 1999 to 2020 (hereinafter referred to as 2010s), were used to create the most comprehensive bathymetric digital elevation models (DEMs) of San Francisco Bay since the 1980s. Comparing DEMs created from these 2010s surveys with USGS DEMs created from NOAA’s 1971–1990 (hereinafter referred to as 1980s) surveys provides information on the quantities and patterns of erosion and deposition in San Francisco Bay during the 9 to 47 years between surveys. This analysis reveals that in the areas surveyed in both the 1980s and 2010s, the bay floor lost about 34 million cubic meters of sediment since the 1980s. Results from this study can be used to assess how San Francisco Bay has responded to changes in the system, such as sea-level rise and variation in sediment supply from the Sacramento-San Joaquin Delta and local tributaries, and supports the creation of a new, system-wide sediment budget. This report provides data on the quantities and patterns of sediment volume change in San Francisco Bay for ecosystem managers that are pertinent to various sediment-related issues, including restoration of tidal marshes, exposure of legacy contaminated sediment, and strategies for the beneficial use of dredged sediment.

Keywords

Pond Complex

Alviso

Eden Landing

Ravenswood

Content available here

Open File Report webpage

South San Francisco Bay Salt Pond Restoration Project—A Synthesis of Phase-1 Mercury Studies

ariela — Wed, 15 Mar 2023 01:38:40 +0000

South San Francisco Bay Salt Pond Restoration Project—A Synthesis of Phase-1 Mercury Studies

Cover of publication

ariela Tue, 03/14/2023 - 18:38

Document Category

Scientific Reports

Author(s)

Mark Marvin-DiPasquale

Darrel Slotton

Joshua T. Ackerman

Maureen A. Downing-Kunz

Date

2023-03

Summary

Abstract

The South Bay Salt Pond Restoration Project (SBSPRP) encompasses over 6,000 hectares of former salt production ponds along the south edge of the San Francisco Bay and represents the largest wetland restoration effort on the west coast of North America. A series of studies associated with Phase 1 (2010–2018) restoration activities that are focused on a historically mercury contaminated slough and series of ponds within the restoration area have recently been completed.

This report brings together the key findings of these loosely coordinated studies and integrates the results into a more comprehensive and holistic product that informs future restoration activities associated with the SBSPRP and elsewhere. This report documents key findings associated with the breach of pond A6: (1) a short-term spike in slough fish (Mississippi silverside) total mercury concentration in lower Alviso Slough; (2) a short-term spike in surface-water particulate total mercury in lower Alviso Slough; (3) significant sediment scour in Alviso Slough adjacent to and downstream of the breach points; (4) a decrease in surface-sediment methylmercury (as a percentage of total mercury) in lower Alviso Slough; (5) the transport of 70 kilograms per year of sediment-associated total mercury into pond A6 during the first 2 years following the breach but with much of this coming from outside of Alviso Slough, presumably from the nearby shallows, Guadalupe Slough, and the larger southern San Francisco Bay area; and (6) a slowing of bed sediment erosion in lower Alviso Slough 3–5 years after the breaching of pond A6.

Although this report is not intended to be prescriptive in terms of the next steps the SBSPRP should or should not take, the totality of the findings presented provide critical process-level information regarding the extent and the duration of spikes in mercury levels in water, sediment, fish, and birds, which appeared to result from the two management actions under study. Thus, these results can be used to anticipate similar ecosystem responses associated with similar management actions that may be considered in the future. We also conclude this report by highlighting unanswered questions associated with mercury dynamics as it relates to the restoration project, and possible future directions for research.

Suggested Citation

Marvin-DiPasquale, M., Slotton, D., Ackerman, J.T., Downing-Kunz, M., Jaffe, B.E., Foxgrover, A.C., Achete, F., and van der Wegen, M., 2022, South San Francisco Bay Salt Pond Restoration Project—A synthesis of Phase-1 mercury studies, U.S. Geological Survey Scientific Investigations Report 2022-5113, 147 p., https://doi.org/10.3133/sir20225113.

First posted March 7, 2023

For additional information, contact:

Director,
Water Resources, Earth System Processes Division
U.S. Geological Survey
345 Middlefield Road
Menlo Park, California, 94025

Keywords

Pond Complex