San Francisco Bay

Scrutinizing the Delta Cross Channel

CALFED | June 1st, 2001

Sea level rise and the drivers of daily water levels in the Sacramento-San Joaquin Delta

Nature Portfolio (Springer Nature) | December 17th, 2023

Sea Level Rise Impacts on Wastewater Treatment Systems Along the U.S. Coasts

American Geophysical Union (AGU) | April 13th, 2018

Wastewater treatment plants are susceptible to flooding resulting from sea level rise. Previous estimates of wastewater exposure have only considered the impacts of mar

Wastewater treatment plants are susceptible to flooding resulting from sea level rise. Previous estimates of wastewater exposure have only considered the impacts of marine flooding at the local or regional scale. In this analysis, we quantify the exposure to marine flooding across the coastal United States and then consider the relative impacts of marine and groundwater flooding at the regional scale in the San Francisco Bay Area. We also estimate the number of people who may lose access to wastewater services if no actions are taken to prevent flooding at wastewater treatment plants. We find that the number of people impacted by sea level rise due to loss of wastewater services could be five times as high as previous predictions of the number of people who experience direct flooding of their homes or property. We also find that groundwater flooding poses a significant threat to wastewater plants in the San Francisco Bay region.

Sea Level Rise in California

Public Policy Institute of California (PPIC) | February 29th, 2024

Sea Level Variations of the United States 1854–2006

National Oceanic and Atmospheric Administration (NOAA) | December 19th, 2009

The United States National Water Level Network (NWLON) was established in the 19th Century to ensure the Nation’s nautical charts, shoreline maps, and elevations relat

The United States National Water Level Network (NWLON) was established in the 19th Century to ensure the Nation’s nautical charts, shoreline maps, and elevations relative to homes, levees, and other coastal infrastructure were accurately referenced to sea level. In support of this mission, NOAA’s Center for Operational Oceanographic Products and Services and its predecessors have determined sea level for the United States since the mid 19th Century. While climate change was not a concern during the mid-1800s, the accurate determination of sea level was critical for navigation and marine boundary determination. To meet these important requirements, technology, procedures, and processes were developed to the highest scientific and engineering standards. At the turn of the 20th Century it was realized that there was a need to account for a rise in sea level and the first National Tidal Datum Epoch was established. Today this Epoch is updated every 20 to 25 years. The Supreme Court recognized these standards and procedures in the landmark 1936 case of Borax, Ltd v. City of Los Angeles when legally defining sea level. Due to those initial efforts and the continued dedication of those charged with the responsibility for monitoring sea level for the United States, we can accurately determine relative (local) mean sea level along the Nation’s coastline today. These observations also play an important role in monitoring change in global sea level. As we monitor change in sea level into the 21st Century, the statement made by Alexander Dallas Bache, the Second Superintendent of the Coast Survey, is as relevant today as when it was stated more than 150 years ago, “It seems a very simple task to make correct tidal observations; but, in all my experience, I have found no observations which require such constant care and attention” (1854). Michael Szabados, Director, Center for Operational Oceanographic Products and Services

Sea-level rise and coastal groundwater inundation and shoaling at select sites in California, USA

Journal of Hydrology: Regional Studies (Elsevier) | January 5th, 2016

Study region: The study region spans coastal California, USA, and focuses on three primary sites: Arcata, Stinson Beach, and Malibu Lagoon. Study focus: 1m and 2m sea-

Study region: The study region spans coastal California, USA, and focuses on three primary sites: Arcata, Stinson Beach, and Malibu Lagoon. Study focus: 1m and 2m sea-level rise (SLR) projections were used to assess vulnerability to SLR-driven groundwater emergence and shoaling at select low-lying, coastal sites in California. Separate and combined inundation scenarios for SLR and groundwater emergence were developed using digital elevation models of study site topography and groundwater surfaces constructed from well data or published groundwater level contours. New hydrological insights for the region: SLR impacts are a serious concern in coastal California which has a long (∼1800km) and populous coastline. Information on the possible importance of SLR-driven groundwater inundation in California is limited. In this study,the potential for SLR-driven groundwater inundation at three sites (Arcata, Stinson Beach,and Malibu Lagoon) was investigated under 1m and 2m SLR scenarios. These sites provide insight into the vulnerability of Northern California coastal plains, coastal developments built on beach sand or sand spits, and developed areas around coastal lagoons associated with seasonal streams and berms. Northern California coastal plains with abundant shallow groundwater likely will see significant and widespread groundwater emergence, while impacts along the much drier central and southern California coast may be less severe due to the absence of shallow groundwater in many areas. Vulnerability analysis is hampered by the lack of data on shallow coastal aquifers, which commonly are not studied because they are not suitable for domestic or agricultural use. Shallow saline aquifers may be present in many areas along coastal California, which would dramatically increase vulnerability to SLR-driven groundwater emergence and shoaling. Improved understanding of the extent and response of California coastal aquifers to SLR will help in preparing for mitigation and adaptation.

Sea-Level Rise for the Coasts of California, Oregon, and Washington: Past, Present, and Future

National Academy of Sciences (NAS) | December 13th, 2012

Sea-level rise impacts on seawater intrusion in coastal aquifers: Review and integration

Journal of Hydrology (Elsevier) | February 6th, 2016

Sea-level rise (SLR) influences groundwater hydraulics and in particular seawater intrusion (SWI) in many coastal aquifers. The quantification of the combined and relativ

Sea-level rise (SLR) influences groundwater hydraulics and in particular seawater intrusion (SWI) in many coastal aquifers. The quantification of the combined and relative impacts of influential factors on SWI has not previously been considered in coastal aquifers. In the present study, a systematic review of the available literature on this topic is first provided. Then, the potential remaining challenges are scrutinized. Open questions on the effects of more realistic complexities such as gradual SLR, parameter uncertainties, and the associated influences in decision-making models are issues requiring further investigation. We assess and quantify the seawater toe location under the impacts of SLR in combination with recharge rate variations, land-surface inundation (LSI) due to SLR, aquifer bed slope variation, and changing landward boundary conditions (LWBCs). This is the first study to include all of these factors in a single analysis framework. Both analytical and numerical models are used for these sensitivity assessments. It is demonstrated that (1) LSI caused by SLR has a significant incremental impact on the seawater toe location, especially in the flatter coasts and the flux-controlled (FC) LWBCs, however this impact is less than the reported orders of magnitude differences which were estimated using only analytical solutions; (2) LWBCs significantly influence the SLR impacts under almost all conditions considered in this study; (3) The main controlling factors of seawater toe location are the magnitudes of fresh groundwater discharge to sea and recharge rate. Regional freshwater flux entering from the landward boundary and the groundwater hydraulic gradient are the major contributors of fresh groundwater discharge to sea for both FC and head-controlled (HC) systems, respectively; (4) A larger response of the aquifer and larger seawater toe location changes are demonstrable for a larger ratio of the aquifer thickness to the aquifer length particularly in the HC systems; (5) The lowest sensitivity of seawater toe location is found for the density difference ratio of the seawater and freshwater, and also for the aquifer bed slope; (6) The early-time observations show seawater fingers below the inundated lands due to SLR which are diminished and ultimately extinguished; and (7) A less than 2% reversal effect on the seawater toe location after overshoot mechanism is observed in the transient simulations which suggests that this mechanism is an insignificant and impractical factor compared to other more significant factors.

Seasonal non-tectonic loading inferred from GPS as a potential trigger for the M6.0 South Napa Earthquake

American Geophysical Union (AGU) | May 8th, 2018

It is well established that earthquakes occur on fault systems where stress has accumulated over periods of centuries to millennia. The specific factors that trigger indi

It is well established that earthquakes occur on fault systems where stress has accumulated over periods of centuries to millennia. The specific factors that trigger individual earthquakes are typically unknown, but researchers have recently found links between seasonal variations in earthquake occurrence and local changes in water storage and temperature. Using data from high-precision continuous GPS stations in Northern California, we observed a small 3 mm horizontal expansion of the Earth's crust prior to and in the vicinity of the August 2014 M6.0 South Napa earthquake. By analyzing the previous eight years of GPS data, we additionally found that a similar pattern of crustal motion repeats every summer. We have determined that this crustal expansion releases pressure on nearby faults, including those in the South Napa fault system, making them more likely to slip during the summer months. Large seasonal variability in the amount of groundwater in the Napa Valley and Sonoma subbasins may contribute to the observed changes.

Seasonality of Retreat Rate of a Wave-Exposed Marsh Edge

American Geophysical Union (AGU) | July 10th, 2024

Waves can cause destruction of marshlands when they collide with the boundary of the marsh area. We studied how the speed of marsh loss from waves can change between seas

Waves can cause destruction of marshlands when they collide with the boundary of the marsh area. We studied how the speed of marsh loss from waves can change between seasons with different climates. To do this we made five 3D models of a marsh in South San Francisco Bay over a single year and looked at their differences between summer/fall/winter/spring. We found fast marsh loss in the seasons where daily winds are common (spring/summer), and minor changes in seasons with storms but without daily winds (fall/winter). Across our entire marsh, we saw lots of variety in how much it was changing, including some addition (i.e., positive change) to the mudflats near the marsh in the fall/winter. When we compared the marsh loss over one year to what was lost between 2004 and 2019, the speeds were similar, so we believe our study period was similar to long‐term marsh dynamics. This work encourages incorporating different seasonal climates into expectations of how marshes evolve, and supports that we need to think about marshes and mudflats as connected in how they change over time.