Background
USGS Western Ecological Research Center manages a decadal network of surface elevation table-marker horizon (SET-MH) plots throughout California, including San Francisco Bay. These plots provide data on elevation change and accretion in wetlands, which can be utilized to assess vulnerability to sea-level rise, restoration evolution, and manage for endangered species. New sites are regularly added to the network, spanning different land-uses and habitat types, from established older marshes to modern restorations. In 2023, SET-MH plots were installed at
Ravenswood Pond R4 prior to its breach to tidal waters to monitor the restoring wetland elevation and accretion change. This report summarizes the installations and subsequent SET-MH readings between December 2023 and December 2025, two years post-breach.
Summary
Visible and measurable change has occurred at Ravenswood Pond R4 since the site was breached to tidal waters. Elevation change across the site shows positive elevation gains in the western area of the site, and elevation loss near the breach, potentially caused by water velocites during breach or thereafter.
The restoration has a seasonal patterns of water salinity and tidal cycles.
Wetland vegetation is not present at SET-MH plots, but cyanobacteria have begun to colonize and is an indicator of succession and is an early colonizer for vegetation establishment.
USGS plans to re-install marker horizons and employ alternative methods if necessary in fall 2026.