Estuaries and Coasts

, Volume 39, Issue 6, pp 1571–1581 | Cite as

Tectonic Subsidence of California Estuaries Increases Forecasts of Relative Sea-Level Rise

  • Alexander SimmsEmail author
  • Laura C. Reynolds
  • Michael Bentz
  • Angela Roman
  • Thomas Rockwell
  • Robert Peters


Even along the generally uplifting coast of the Pacific US, local geologic structures can cause subsidence. In this study, we quantify Holocene-averaged subsidence rates in four estuaries (Carpinteria Slough, Goleta Slough, Campus Lagoon, and Morro Bay) along the southern and central California coast by comparing radiocarbon-dated estuarine material to a regional sea-level curve. Holocene-averaged rates of vertical motion range from subsidence of 1.4 ± 2.4, 1.2±0.4, and 0.4 ± 0.3 mm/year in Morro Bay, Carpinteria Slough, and Goleta Slough, respectively, to possible uplift in Campus Lagoon (−0.1 ± 0.9 mm/year). The calculated rates of subsidence are of the same magnitude as rates of relative sea-level rise experienced over the late Holocene and effectively double the ongoing rates of relative sea-level rise experienced over the last five decades on other parts of the coast. The difference in rates of vertical motion among these four estuaries is attributed to their geological settings. Estuaries developed in subsiding geological structures such as synclines and fault-bounded basins are subsiding at much higher rates than those developed within flooded river valleys incised into marine terraces. Restoration projects accounting for future sea-level rise must consider the geologic setting of the estuaries and, if applicable, include subsidence in future sea-level rise scenarios, even along the tectonically uplifting US Pacific Coast.


Estuary Marsh Sea level Compaction Lagoon Santa Barbara 



We would like to thank Johnathan Rice, Daniel Livsey, Lauren Simkins, and Elisabeth Steel for their help in the field. Gratitude is also expressed to Andrew Brooks of the Carpinteria Saltmarsh Reserve, Christine Thompson of the California Department of Fish and Wildlife, and Lisa Stratton from the Cheadle Center for Biodiversity and Ecological Restoration (CCBER) at UC-Santa Barbara for helping to facilitate permission to work in Carpinteria Slough, Goleta Slough, and Campus Lagoon, respectively. We also wish to thank John Southon of UC-Irvine for help with the 14C dating. Funding for this project was provided by the Santa Barbara Coastal Long-Term Ecological Research (LTER) program of the National Science Foundation. This research was also supported by the Southern California Earthquake Center (Contribution No. 6020). SCEC is funded by NSF Cooperative Agreement EAR-1033462 and USGS Cooperative Agreement G12AC20038.


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Copyright information

© Coastal and Estuarine Research Federation 2016

Authors and Affiliations

  • Alexander Simms
    • 1
    Email author
  • Laura C. Reynolds
    • 1
  • Michael Bentz
    • 1
  • Angela Roman
    • 1
  • Thomas Rockwell
    • 2
  • Robert Peters
    • 2
  1. 1.Department of Earth ScienceUniversity of California, Santa BarbaraSanta BarbaraUSA
  2. 2.Department of Geological SciencesSan Diego State UniversitySan DiegoUSA

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