Skip to main content

Thank you for visiting You are using a browser version with limited support for CSS. To obtain the best experience, we recommend you use a more up to date browser (or turn off compatibility mode in Internet Explorer). In the meantime, to ensure continued support, we are displaying the site without styles and JavaScript.

Increasing threat of coastal groundwater hazards from sea-level rise in California


Projected sea-level rise will raise coastal water tables, resulting in groundwater hazards that threaten shallow infrastructure and coastal ecosystem resilience. Here we model a range of sea-level rise scenarios to assess the responses of water tables across the diverse topography and climates of the California coast. With 1 m of sea-level rise, areas flooded from below are predicted to expand ~50–130 m inland, and low-lying coastal communities such as those around San Francisco Bay are most at risk. Coastal topography is a controlling factor; long-term rising water tables will intercept low-elevation drainage features, allowing for groundwater discharge that damps the extent of shoaling in ~70% (68.9–82.2%) of California’s coastal water tables. Ignoring these topography-limited responses increases flooded-area forecasts by ~20% and substantially underestimates saltwater intrusion. All scenarios estimate that areas with shallow coastal water tables will shrink as they are inundated by overland flooding or are topographically limited from rising inland.

This is a preview of subscription content, access via your institution

Relevant articles

Open Access articles citing this article.

Access options

Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Fig. 1: California’s loss of shallow water tables with sea-level rise.
Fig. 2: Distribution of flux-controlled and topography-limited groundwater conditions along coastal California for higher sea levels.
Fig. 3: Saline groundwater wedge footprint in shallow coastal California groundwater.

Data availability

Derived model outputs that were merged across overlapping model boundaries and compiled to county boundaries are available to download at The available data include georeferenced rasters of hydraulic head (that is, water table elevation) and water table depth and georeferenced shapefiles of the water table depth categories. The saline groundwater wedge footprint shapefiles are available to download at The other MODFLOW input, output and derived datasets are available upon request. All other input datasets are available from the original sources.

Code availability

The relevant portions of the pre- and post-processing functions and scripts used to develop the figures and datasets in this study are available at All other codes are available upon request at the discretion of the authors.


  1. Nicholls, R. J. & Cazenave, A. Sea-level rise and its impact on coastal zones. Science 328, 1517–1520 (2010).

    CAS  Google Scholar 

  2. Bamber, J. L., Oppenheimer, M., Kopp, R. E., Aspinall, W. P. & Cooke, R. M. Ice sheet contributions to future sea-level rise from structured expert judgment. Proc. Natl Acad. Sci. USA 166, 11195–11200 (2019).

    Google Scholar 

  3. Spencer, T. et al. Global coastal wetland change under sea-level rise and related stresses: the DIVA wetland change model. Glob. Planet. Change 139, 15–30 (2016).

    Google Scholar 

  4. Moftakhari, H. R. et al. Increased nuisance flooding due to sea-level rise: past and future. Geophys. Res. Lett. 42, 9846–9852 (2015).

    Google Scholar 

  5. Vitousek, S. Doubling of coastal flooding frequency within decades due to sea-level rise. Sci. Rep. 7, 1399 (2017).

    Google Scholar 

  6. Church, J. A. et al. in Climate Change 2013: The Physical Science Basis (eds Stocker, T. F. et al.) 1137–1216 (IPCC, Cambridge Univ. Press, 2013).

  7. Neumann, B., Vafeidis, A. T., Zimmermann, J. & Nicholls, R. J. Future coastal population growth and exposure to sea-level rise and coastal flooding—a global assessment. PLoS ONE 10, e0118571 (2015).

    Google Scholar 

  8. Diaz, D. B. Estimating global damages from sea level rise with the Coastal Impact and Adaptation Model (CIAM). Clim. Change 137, 143–156 (2016).

    Google Scholar 

  9. Barnard, P. L. et al. Dynamic flood modeling essential to assess the coastal impacts of climate change. Sci. Rep. 9, 4309 (2019).

    Google Scholar 

  10. Rotzoll, K. & Fletcher, C. H. Assessment of groundwater inundation as a consequence of sea-level rise. Nat. Clim. Change 3, 477–481 (2013).

    Google Scholar 

  11. Webb, M. D. & Howard, K. W. F. Modeling the transient response of saline intrusion to rising sea-levels. Ground Water 49, 560–569 (2011).

    CAS  Google Scholar 

  12. Werner, A. D. & Simmons, C. T. Impact of sea-level rise on sea water intrusion in coastal aquifers. Ground Water 47, 197–204 (2009).

    CAS  Google Scholar 

  13. Michael, H. A., Russoniello, C. J. & Byron, L. A. Global assessment of vulnerability to sea-level rise in topography-limited and recharge-limited coastal groundwater systems. Water Resour. Res. 49, 2228–2240 (2013).

    Google Scholar 

  14. Masterson, J. P. et al. Effects of sea-level rise on barrier island groundwater system dynamics—ecohydrological implications. Ecohydrology 7, 1064–1071 (2014).

    Google Scholar 

  15. Kirwan, M. L. & Gedan, K. B. Sea-level driven land conversion and the formation of ghost forests. Nat. Clim. Change 9, 450–457 (2019).

    Google Scholar 

  16. Hummel, M. A., Berry, M. S. & Stacey, M. T. Sea level rise impacts on wastewater treatment systems along the U.S. coasts. Earth’s Future 6, 622–633 (2018).

    Google Scholar 

  17. Liu, T., Su, X. & Prigiobbe, V. Groundwater–sewer interaction in urban coastal areas. Water 10, 1774 (2018).

    CAS  Google Scholar 

  18. Knott, J. F., Daniel, J. S., Jacobs, J. M. & Kirshen, P. Adaptation planning to mitigate coastal-road pavement damage from groundwater rise caused by sea-level rise. Transp. Res. Rec. 2672, 11–22 (2018).

    Google Scholar 

  19. Myers, N. Environmental refugees: a growing phenomenon of the 21st century. Phil. Trans. R. Soc. Lond. B 357, 609–613 (2002).

    Google Scholar 

  20. Nicholls, R. J. et al. Sea-level rise and its possible impacts given a ‘beyond 4 °C world’ in the twenty-first century. Phil. Trans. R. Soc. A 369, 161–181 (2011).

    Google Scholar 

  21. Abarca, E., Karam, H., Hemond, H. F. & Harvey, C. F. Transient groundwater dynamics in a coastal aquifer: the effects of tides, the lunar cycle and the beach profile. Water Resour. Res. 49, 2473–2488 (2013).

    Google Scholar 

  22. Nielsen, P. Tidal dynamics of the water table in beaches. Water Resour. Res. 26, 2127–2134 (1990).

    Google Scholar 

  23. Ketabchi, H., Mahmoodzadeh, D., Ataie-Ashtiani, B. & Simmons, C. T. Sea-level rise impacts on seawater intrusion in coastal aquifers: review and integration. J. Hydrol. 535, 235–255 (2016).

    Google Scholar 

  24. Masterson, J. P. & Garabedian, S. P. Effects of sea-level rise on ground water flow in a coastal aquifer system. Ground Water 45, 209–217 (2007).

    CAS  Google Scholar 

  25. Werner, A. D. et al. Vulnerability indicators of sea water intrusion. Ground Water 50, 48–58 (2012).

    CAS  Google Scholar 

  26. Burnett, W. C., Bokuniewicz, H., Huettel, M., Moore, W. S. & Taniguchi, M. Groundwater and pore water inputs to the coastal zone. Biogeochemistry 66, 3–33 (2003).

    CAS  Google Scholar 

  27. Hoover, D. J., Odigie, K. O., Swarzenski, P. W. & Barnard, P. Sea-level rise and coastal groundwater inundation and shoaling at select sites in California, USA. J. Hydrol. Reg. Stud. 11, 234–249 (2017).

    Google Scholar 

  28. Plane, E., Hill, K. & May, C. A rapid assessment method to identify potential groundwater flooding hotspots as sea levels rise in coastal cities. Water 11, 2228 (2019).

    CAS  Google Scholar 

  29. Lu, C., Werner, A. D. & Simmons, C. T. Threats to coastal aquifers. Nat. Clim. Change 3, 605 (2013).

    Google Scholar 

  30. Harbaugh, A. W. MODFLOW-2005: The U.S. Geological Survey Modular Ground-Water Model—the Ground-Water Flow Process Techniques and Methods No. 6-A16 (US Geological Survey, 2005).

  31. Topologically Integrated Geographic Encoding and Referencing (TIGER) Database (US Census Bureau, 2016).

  32. Gleeson, T., Moosdorf, N., Hartmann, J. & van Beek, L. P. H. A glimpse beneath Earth’s surface: GLobal HYdrogeology MaPS (GLHYMPS) of permeability and porosity. Geophys. Res. Lett. 41, 3891–3898 (2014).

    Google Scholar 

  33. Glover, R. E. The pattern of fresh-water flow in a coastal aquifer. J. Geophys. Res. 64, 457–459 (1959).

    Google Scholar 

  34. Kopp, R. E. et al. Probabilistic 21st and 22nd century sea-level projections at a global network of tide-gauge sites. Earth’s Future 2, 383–406 (2014).

    Google Scholar 

  35. Sweet, W. V. et al. Global and Regional Sea Level Rise Scenarios for the United States Technical Report NOS CO-OPS (NOAA, 2017).

  36. State of California Sea-Level Rise Guidance—2018 Update (California Ocean Protection Council, 2018).

  37. Duvall, A., Kirby, E. & Burbank, D. Tectonic and lithologic controls on bedrock channel profiles and processes in coastal California. J. Geophys. Res. 109, F03002 (2004).

    Google Scholar 

  38. Vitousek, S., Barnard, P. L., Limber, P., Erikson, L. & Cole, B. A model integrating longshore and cross-shore processes for predicting long-term shoreline response to climate change. J. Geophys. Res. Earth Surf. 122, 782–806 (2017).

    Google Scholar 

  39. Erikson, L. H., O’Neill, A., Barnard, P. L., Vitousek, S. & Limber, P. Climate change-driven cliff and beach evolution at decadal to centennial time scales. In Proc. Coastal Dynamics 2017 (eds Aagaard, T. et al.) 125–136 (2017).

  40. Limber, P. W., Barnard, P. L., Vitousek, S. & Erikson, L. H. A model ensemble for projecting multidecadal coastal cliff retreat during the 21st century. J. Geophys. Res. Earth Surf. 123, 1566–1589 (2018).

    Google Scholar 

  41. Knott, J. F., Elshaer, M., Daniel, J. S., Jacobs, J. M. & Kirshen, P. Assessing the effects of rising groundwater from sea level rise on the service life of pavements in coastal road infrastructure. Transp. Res. Rec. 2639, 1–10 (2017).

    Google Scholar 

  42. Habel, S., Fletcher, C. H., Rotzoll, K. & El-Kadi, A. I. Development of a model to simulate groundwater inundation induced by sea-level rise and high tides in Honolulu, Hawaii. Water Res. 114, 122–134 (2017).

    CAS  Google Scholar 

  43. Hughes, J. D. & White, J. T. Hydrologic Conditions in Urban Miami-Dade County, Florida, and the Effect of Groundwater Pumpage and Increased Sea Level on Canal Leakage and Regional Groundwater Flow Scientific Investigations Report No. 2014–5162 (US Geological Survey, 2014).

  44. Guha, H. & Panday, S. Impact of sea level rise on groundwater salinity in a coastal community of South Florida. J. Am. Water Resour. Assoc. 48, 510–529 (2012).

    Google Scholar 

  45. Sukop, M. C., Rogers, M., Guannel, G., Infanti, J. M. & Hagemann, K. High temporal resolution modeling of the impact of rain, tides, and sea level rise on water table flooding in the Arch Creek basin, Miami-Dade County Florida USA. Sci. Total Environ. 616–617, 1668–1688 (2018).

    Google Scholar 

  46. Bakker, M. et al. Scripting MODFLOW model development using Python and FloPy. Groundwater 54, 733–739 (2016).

    CAS  Google Scholar 

  47. Reitz, M., Sanford, W. E., Senay, G. B. & Cazenas, J. Annual Estimates of Recharge, Quick-Flow Runoff, and ET for the Contiguous US Using Empirical Regression Equations, 2000–2013 (US Geological Survey, 2017).

  48. Reitz, M., Sanford, W. E., Senay, G. B. & Cazenas, J. Annual estimates of recharge, quick-flow runoff, and evapotranspiration for the contiguous U.S. using empirical regression equations. J. Am. Water Resour. Assoc. 53, 961–983 (2017).

    Google Scholar 

  49. Hanson, R. T., Martin, P. & Koczot, K. M. Simulation of Ground-Water/Surface-Water Flow in the Santa Clara-Calleguas Ground-Water Basin, Ventura County, California Water-Resources Investigations Report No. 2002-4136 (US Geological Survey, 2003).

  50. Hanson, R. T., Schmid, W., Faunt, C. C., Lear, J. & Lockwood, B. Integrated Hydrologic Model of Pajaro Valley, Santa Cruz and Monterey Counties, California Scientific Investigations Report No. 2014-5111 (US Geological Survey, 2014).

  51. Reichard, E. G. et al. Geohydrology, Geochemistry, and Ground-Water Simulation-Optimization of the Central and West Coast Basins, Los Angeles County, California Water-Resources Investigations Report No. 03-4065 (US Geological Survey, 2003).

  52. Nishikawa, T. A Simulation-Optimization Model for Water-Resources Management, Santa Barbara, California Water-Resources Investigations Report No. 97-4246 (US Geological Survey, 1998).

  53. Farrar, C. D., Metzger, L. F., Nishikawa, T., Koczot, K. M. & Reichard, E. G. Geohydrological Characterization, Water-Chemistry, and Ground-Water Flow Simulation Model of the Sonoma Valley Area, Sonoma County, California Scientific Investigations Report No. 2006-5092 (US Geological Survey, 2006).

  54. Bright, D. J., Nash, D. B. & Martin, P. Evaluation of Ground-Water Flow and Solute Transport in the Lompoc Area, Santa Barbara County, California Water-Resources Investigations Report No. 97-4056 (US Geological Survey, 1997).

  55. Knott, J. F., Jacobs, J. M., Daniel, J. S. & Kirshen, P. Modeling groundwater rise caused by sea-level rise in coastal New Hampshire. J. Coast. Res. 35, 143–157 (2019).

    Google Scholar 

  56. Huscroft, J., Gleeson, T., Hartmann, J. & Börker, J. Compiling and mapping global permeability of the unconsolidated and consolidated Earth: GLobal HYdrogeology MaPS 2.0 (GLHYMPS 2.0). Geophys. Res. Lett. 45, 1897–1904 (2018).

    Google Scholar 

  57. Gleeson, T. et al. Mapping permeability over the surface of the Earth. Geophys. Res. Lett. 38, L02401 (2011).

    Google Scholar 

  58. Zamrsky, D., Oude Essink, G. H. P. & Bierkens, M. F. P. Estimating the thickness of unconsolidated coastal aquifers along the global coastline. Earth Syst. Sci. Data 10, 1591–1603 (2018).

    Google Scholar 

  59. Tyler, D. J. & Danielson, J. J. Topobathymetric Model for the Southern Coast of California and the Channel Islands, 1930 to 2014 (US Geological Survey, 2018).

  60. Danielson, J. J. et al. Topobathymetric elevation model development using a new methodology: coastal national elevation. Database J. Coast. Res. 76, 75–89 (2016).

    Google Scholar 

  61. Tyler, D. J., Danielson, J. J., Poppenga, S. K. & Gesch, D. B. Topobathymetric Model for the Central Coast of California, 1929 to 2017 (US Geological Survey, 2018).

  62. Tarboton, D. G. Terrain Analysis Using Digital Elevation Models (TauDEM) (Utah State Univ., 2005).

  63. Estimation of Vertical Uncertainties in VDatum (National Oceanic and Atmospheric Administration, 2018).

  64. National Oceanic Data Center (Levitus) World Ocean Atlas (National Oceanic and Atmospheric Administration, 1994).

  65. Schraga, T. S. & Cloern, J. E. Water quality measurements in San Francisco Bay by the U.S. Geological Survey, 1969-2015. Sci. Data 4, 170098 (2017).

    CAS  Google Scholar 

  66. Post, V., Kooi, H. & Simmons, C. Using hydraulic head measurements in variable-density ground water flow analyses. Ground Water 45, 664–671 (2007).

    CAS  Google Scholar 

  67. Befus, K. M. kbefus/ca_gw_slr Zenodo (2020).

  68. Befus, K. M., Hoover, D., Barnard, P. L. & Erikson, L. H. California Coastal Groundwater Projected Response with Sea-Level Rise (US Geological Survey, 2020);

  69. Befus, K. M., Barnard, P. L., Hoover, D. J., Finzi Hart, J. A. & Voss C. California saline groundwater wedge footprint model results. HydroShare (2020).

  70. Badon Ghyben, W. Nota in Verband Met de Voorgenomen Putboring Nabil Amsterdam. Tijdschr. K. Inst. Ing. 9, 8–22 (1888).

    Google Scholar 

  71. Herzberg, A. Die wasserversorgung einiger Nordseebader. J. Gasbeleucht. Wasserversorg. 44, 815–819 (1901).

    Google Scholar 

  72. Feistel, R. A Gibbs function for seawater thermodynamics for −6 to 80 °C and salinity up to 120 g kg−1. Deep Sea Res. I 55, 1639–1671 (2008).

    Google Scholar 

  73. Kuan, W. K. et al. Tidal influence on seawater intrusion in unconfined coastal aquifers. Water Resour. Res. 48, W02502 (2012).

    Google Scholar 

  74. Ataie-Ashtiani, B., Volker, R. E. & Lockington, D. A. Tidal effects on sea water intrusion in unconfined aquifers. J. Hydrol. 216, 17–31 (1999).

    Google Scholar 

  75. Pool, M., Post, V. E. A. & Simmons, C. T. Effects of tidal fluctuations and spatial heterogeneity on mixing and spreading in spatially heterogeneous coastal aquifers. Water Resour. Res. 51, 1570–1585 (2015).

    Google Scholar 

  76. Werner, A. D. et al. Seawater intrusion processes, investigation and management: recent advances and future challenges. Adv. Water Res. 51, 3–26 (2013).

    Google Scholar 

  77. Yu, X. & Michael, H. A. Mechanisms, configuration typology, and vulnerability of pumping-induced seawater intrusion in heterogeneous aquifers. Adv. Water Resour. 128, 117–128 (2019).

    Google Scholar 

  78. Strack, O. D. L. & Ausk, B. K. A formulation for vertically integrated groundwater flow in a stratified coastal aquifer. Water Resour. Res. 51, 6756–6775 (2015).

    Google Scholar 

Download references


This project was funded by the California Safe Drinking Water, Water Quality and Supply, Flood Control, River and Coastal Protection Bond Act of 2006 (Proposition 84), the Ocean Protection Council and the USGS Coastal and Marine Hazards and Resources Program. NODC_WOA94 salinity data were provided by the NOAA/OAR/ESRL PSD from Any use of trade, firm or product names is for descriptive purposes only and does not imply endorsement by the US government.

Author information

Authors and Affiliations



All authors participated in conceiving the study, developing the analyses and writing the paper. K.M.B. performed the modelling and analyses with input from all authors.

Corresponding author

Correspondence to K. M. Befus.

Ethics declarations

Competing interests

The authors declare no competing interests.

Additional information

Peer review information Nature Climate Change thanks Chunhui Lu, Christine May and the other, anonymous, reviewer(s) for their contribution to the peer review of this work.

Publisher’s note Springer Nature remains neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Extended data

Extended Data Fig. 1 Difference in model water table response behavior.

Conceptual cross-section showing how the flux-controlled model can overpredict heads compared to the water tables that include the hydraulic conditions created by surface drains.

Extended Data Fig. 2 Distribution of flux-controlled (≤5%) and topography-limited (>5%) groundwater conditions along coastal California for higher sea levels.

The overprediction of the water table rise by the flux-controlled response was calculated for all K and tidal datum scenarios to 1 km inland with Methods Eq. 1.

Extended Data Fig. 3 Distribution of emergent groundwater, flux-controlled, and topography-limited conditions with increasing sea levels and varying the distance inland used in the analysis for the LMSL tidal datum scenarios.

The MHHW distributions showed very similar distributions and were visually indistinguishable from the LMSL distributions in this figure. Note the irregular spacing on the vertical axes.

Extended Data Fig. 4 Profile-based comparison with current analysis.

Spatial comparison between the overprediction calculated in this study (Eq. 1; LMSL + 1 m, K = 1 m/d, MODFLOW forecast) and the delineation of flux-controlled (that is, recharge-limited) and topography-limited profiles from the “base case” of Michael et al.13 for 1 m of sea-level rise.

Extended Data Fig. 5

Graphical definition of the saline groundwater wedge footprint and saltwater intrusion.

Extended Data Fig. 6

Growth of the saline groundwater wedge footprint across coastal California regions for the flux-controlled and MODFLOW model predictions.

Supplementary information

Supplementary Information

Supplementary Figs. 1–6, Tables 1–11 and Discussion 1.

Rights and permissions

Reprints and Permissions

About this article

Verify currency and authenticity via CrossMark

Cite this article

Befus, K.M., Barnard, P.L., Hoover, D.J. et al. Increasing threat of coastal groundwater hazards from sea-level rise in California. Nat. Clim. Chang. 10, 946–952 (2020).

Download citation

  • Received:

  • Accepted:

  • Published:

  • Issue Date:

  • DOI:

This article is cited by


Quick links

Nature Briefing

Sign up for the Nature Briefing newsletter — what matters in science, free to your inbox daily.

Get the most important science stories of the day, free in your inbox. Sign up for Nature Briefing