San Diego Beach Report

State Beach:   Border Field  •  Silver Strand  •  Torrey Pines  •  Cardiff  •  San Elijo  •  Moonlight  •  Leucadia  •  South Carlsbad  •  Carlsbad



Introduction


The San Diego County State Beach Report is an annual update of the physical condition of nine California State Park beaches in the County. In addition, an UPCOMING WINTER WAVES AND BEACH EROSION OUTLOOK is provided during the fall months of each year.

The report “Beach Years” begin October 1 of the previous calendar year to best capture a full annual winter (erosion) and summer (accretion) cycle. This 2020 Beach Year Report is based on observations from Oct 1, 2019 to Sep 30, 2020.

Select one of the State Beaches from the menu above to view individual beach survey products.


Overview

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

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

The last three beach recovery phases (post-2003,2010,2016 El Ninos) at South Torrey Pines show a consistent pattern that begins with an El Nino 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, lower panel, Fig. 1). It is a useful reference beach when interpreting the erosion-recovery phases of the other beaches in the County.


2020 Executive Summary



References

B.C. Ludka, A.P. Young, R.T. Guza, W.C. O’Reilly, M.A. Merrifield, 2020 (submitted). Nourishing an erosion hotspot. Geophysical Research Letters.