Figure 1. Summary of observed annual mean beach width change since 1998. Lines are linear best fit beach width trends between El Niño years for individual beaches. Beaches with negative trends between the 2016 and 2025 El Niños (upper panel) are grouped as currently eroding on a multi-year time scale. Beaches with 2016-2023 positive trends are grouped as currently accreting (lower panel).

San Diego County beach change over the last several decades can be conceptualized as the interplay between two primary variables:

• Available nearshore sand supply.


• Wave-driven beach erosion and accretion in response to the El Niño-Southern Oscillation (ENSO) climate pattern, with each multi-year period between El Niño winters being a distinct "beach recovery phase" (trend lines, Figure 1).

Unusually high winter waves and severe beach erosion are often associated with episodic El Niño winters, which typically occur every 2-7 years. Natural beach widening, or recovery from El Niños, happens more gradually over the course of the milder winter years between El Niño events.

During the recovery phase, the beach does not necessarily increase monotonically in annual width, because there is still a modest range of winter and summer wave variability from year to year. However, the net change, or trend, is typically positive over the recovery years assuming there is a sufficient supply of nearshore sand to migrate shoreward onto the subaerial beach during the summer high tides.

South Torrey Pines State Beach (yellow squares, upper panel) is considered the closest thing to a well-monitored "control beach" in the County. It is long (3.5km), wide (70m), and relatively stable. It hasn't been nourished directly, but is located at the southern boundary of the Oceanside Littoral Cell. As a result, the beach's sand supply is likely enhanced by the overall southward littoral drift in the Cell, and the beach remains mostly sandy year-round.

Prior to 2021, the last three ENSO beach recovery phases (post-1998, 2003, 2010, 2016 El Niños) at South Torrey Pines show a consistent pattern that begins with an El Niño winter erosion year of varying severity (2-10+ m), followed by multiple years of beach recovery with an average rate of approximately +1m/year (yellow trend line slopes between 2003 and 2015, upper panel, Fig. 1). It is a useful reference beach when interpreting the erosion-recovery phases of the other beaches in the County.

2024 was an El Niño year, marking the completion of the 2016-2023 ENSO "recovery" phase, which in the end was not a multi-year period of beach widening. Unlike the 3 previous recovery periods (1998-2002, 2003-2009, 2010-2015), the 2016-2023 period was negatively impacted by two atmospheric river winters (2017,2023) and an extreme wave event in January, 2021.

• 2025 is the first year of a new multi-year ENSO recovery phase, following the 2024 El Niño, and nearly all the San Diego County State Beaches have positive trends in annual beach width (+1m to +8m/year) (Accreting Beaches, lower panel, Fig. 1).


• San Elijo SB (orange triangles, lower panel) has the largest width gain in 2025 (+8m) owing to the southward migration of 2024 nourishment sand from Moonlight SB (+20m width increase in 2024, light blue diamonds, lower panel).
  


• The 2025-2026 Winter Waves and Beaches Outlook points to weak La Niña conditions with slightly above average waves and beach loss conditions. However, well above average winter beach loss is very unlikely and we anticipate a year of relatively stable annual mean beach widths in 2026, with only slight annual widening or narrowing relative to 2025.
  
  

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