The new study addresses this gap with time-series measurements of sediment movement, paired with long-term data from elevation surveys and sediment cores.

The study, which focused on a 20-hectare marsh within Eden Landing Ecological Reserve in Hayward, CA, found that the most pronounced period of sediment buildup, or accretion, occurred early in the restoration process, which began in the 1990s. The highest accretion estimate during that period was 2.6 centimeters per year, which eventually slowed to the modern estimated rate of 0.9 cm/year.

“Our goal was to look at how the marsh is evolving from a physical standpoint: how channels form, how the marsh surface accretes vertically, how new marsh vegetation emerges as the land surface evolves,” said Dan Nowacki, USGS Oceanographer and lead author of the study. “And we looked at this physical evolution across a variety of time scales, from individual tidal cycles, to weeks, to seasons, to years, and then decades.”

The study notes that accelerated sea-level rise, combined with a drop in the availability of suspended sediment in the Bay, could threaten ongoing and future restoration efforts, particularly as restored marshes mature beyond the initial, higher-sedimentation stages. Early restoration gains don’t guarantee long-term survival without sustained sediment supply and consideration of future sea-level projections.