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U.S. Department of the InteriorU.S. Geological Survey

USGS Fact Sheet 026-002000

El Niño Storms Erode Beaches on Monterey Bay, California

REDUCING THE RISK FROM COASTAL GEOLOGIC HAZARDS

s recently as 1998, stormsgenerated by El Niños se-

verely eroded beaches alongMonterey Bay, California. Tobetter understand the effects ofsuch storms, United States Geo-logical Survey (USGS) scien-tists, in cooperation with theCalifornia Department of Parksand Recreation, have been ac-tively monitoring changes in theforeshore since the mid-1980’s.The results of this study willhelp protect coastal residents,property, and environments andare being used by the State ofCalifornia in guiding the manag-ement of public beaches.

Intense storms often produce abnor-mally high waves and elevated sea level,causing extensive beach erosion andshoreline retreat. The worst erosion gener-ally occurs when multiple storms hit dur-ing periods of especially high tides. Sev-eral years may pass between stormsintense enough to cause shoreline erosionthat results in significant widespread dam-age. Although waves rebuild beaches aftersuch storms, this seaward accretion maynot return a beach to its pre-storm position,requiring coastal-zone managers to considerwhether to take remedial measures.

During the winters of 1982-83 and1997-98, two of the most severe El Niñosof the 20th century produced intensestorms that pounded central California.These storms followed more southerlytracks than usual and combined with peri-ods of high tides to intensify the normalwinter erosional cycle, causing tens ofmillions of dollars in damage along thecentral California coast. On MontereyBay, coastal cliffs, dunes, and manmadestructures suffered serious damage, much

of it along the northern, most populatedpart of the bay. To better understand theeffects of such storms, United States Geo-logical Survey (USGS) scientists, in coop-eration with the California Department ofParks and Recreation (DPR), began ac-tively monitoring changes at nine Califor-nia State Beaches on Monterey Bay in1983 and at four additional ones in 1985.

The extent of beach erosion or accretionis measured by landward or seaward shiftsin the position of the shoreline at mean sealevel (MSL). Storm waves during the1982-83 El Niño had stripped large vol-umes of sand from Monterey Bay beaches,leaving beachfront homes and coastalcliffs and dunes exposed to direct wave at-tack. By the end of the 1982-83 El Niñostorms, Monterey Bay beaches were dis-tinctly narrower than before. For 2 years,

normal wave activity deposited sand, re-building the beaches. However, there is noway of knowing whether the beaches re-turned to near their pre-El Niño states, be-cause no data had been collected on theirprofiles before 1983. In succeeding years,the beaches went through several erosionaland depositional cycles. From 1985through September 1997, all but twoMonterey Bay beaches remained stableexcept for normal seasonal fluctuations.

During the 1997-98 El Niño, several in-tense winter storms from the south struckthe Monterey Bay coastline. However,beach erosion along the bay was less thanin the 1982-83 El Niño, and not a singleMonterey Bay beach was eroded so se-verely in 1997-98. For example, atSeacliff State Beach on the northeastcoast of the bay, which is most susceptible

Waves generated by severe winter stormsduring the 1982-83 El Niño destroyed thewooden seawall at Seacliff State Beach onCalifornia’s Monterey Bay. The barrier oflarge stones that had been emplacedseaward of the wall was also scattered bythe waves (photo above). The photo atright, taken 2 years after these storms,shows the replacement seawall and rebuiltbeach. This seawall remained intact duringthe 1997-98 El Niño.

Printed on recycled paper

John R. Dingler

Graphic design bySusan Mayfield and Sara Boore

For more information contact:U.S. Geological Survey, MS-999

345 Middlefield RoadMenlo Park, CA 94025

(650) 329-5042http://marine.usgs.gov/

See also El Niño Sea-Level Rise Wreaks Havoc in California’sSan Francisco Bay Region (USGS Fact Sheet 175-99)

COOPERATING ORGANIZATIONCalifornia Department of

Parks and Recreation

to waves from the south, erosion duringthe 1997-98 El Niño was no more severethan during some non-El Niño years.

Only two beaches appear to have under-gone net retreat since 1983. One, MossLanding State Beach, is adjacent to thehead of Monterey Submarine Canyon, afactor that complicates interpretations oflong-term shoreline retreat because sanderoded from the beach may move downthe canyon and be lost to the deep sea. Theother, Fort Ord Beach, is narrow and backedby a high, but easily eroded, cliff. In mostyears, winter storm waves erode the beachto the extent that they can attack the cliff.Consequently, the shoreline has retreated anaverage of 1 to 2 yards (meters) per yearsince USGS monitoring began in 1983.However, the summer beach continues tomaintain nearly the same shape and width asit migrates landward.

The cooperative efforts of USGS scien-tists and the DPR at Monterey Bay’sbeaches have led to a better understandingof how these beaches change during both ElNiño and non-El Niño years. The results ofthese ongoing studies are being used by the

DPR to help guide the management of pub-lic beaches along Monterey Bay. They willalso provide new insights into how beacherosion occurs in other coastal areas. To im-prove that understanding further, the USGSwill continue to collect and analyze datafrom these beaches. The work of USGS sci-entists in the area of Monterey Bay is onlypart of the USGS Coastal and Marine Geol-ogy Program’s ongoing efforts to protectpeople’s lives and property from geologicand environmental hazards in the coastalzones of the United States.

During 1982-83 El Niño storms, Seacliff StateBeach on California’s Monterey Bay was se-verely eroded. Cross-shore profiles obtained byU.S. Geological Survey scientists show thatnormal wave activity in succeeding yearsdeposited sand, rebuilding the beach. The firstprofile (February 1983) was made at the sametime as the photograph on the front of thissheet. Wave conditions governed the depth towhich the profiles extend below mean sea level(MSL). Erosion at Seacliff State Beach duringthe 1997-98 El Niño was no more severe thanduring some non-El Niño years.

MONTEREY BAY STATE BEACHES AND THE EXTENT OF EROSION AND ACCRETION DURING 1983 TO 1998

The extent of beach erosion or accretion is measuredby landward or seaward shifts in the position of theshoreline at mean sea level (MSL). Storm waves duringthe 1982-83 El Niño had stripped large volumes of sandfrom Monterey Bay beaches, leaving beachfront

9

Monterey BayState Beaches

(see map for locations)

8

7

6

5

4

3

2

1

YEAR

SHOR

ELIN

E SH

IFT

AT M

EAN

SEA

LEVE

L

1984 1986 1988 1990 1992 1994 1996 1998

Build

ing

seaw

ard

Erod

ing

land

war

d10

0 MET

ERS

CALIFORNIAAreaof map

Seacliff State BeachNew BrightonState Beach

1

2

3

12

4

5

6

10

7

89

13

11

Manresa State Beach

Sunset State Beach

Zmudowski State Beach

Moss Landing State Beach

Salinas RiverState Beach (north)

Salinas RiverState Beach (mouth)

Marina State Beach

Fort Ord Beach

Sand City BeachPt Piños

500 m

100 m

Pt Santa Cruz

Del Monte Beach

Monterey State BeachFirst surveyed 2/83

MONTEREY

SANTACRUZ

M

ON

TE

RE

Y

BA

YMONTEREY CANYON

5 MILES0

0 5 KILOMETERS

500

2

METERS

MET

ERS

Mean sea level

Profiles of Seacliff State Beach1983 to 1998

3/10/98

9/9/97

3/28/95

6/26/86

2/3/83

Top of rebuilt stairs

homes and coastal cliffs and dunes exposed to direct wave attack. By the end of the 1982-83 El Niño storms, Monterey Bay beaches were distinctly narrower thanbefore. U.S. Geological Survey scientists, in cooperation with the California Department of Parks and Recreation, began actively monitoring changes at nineMonterey Bay beaches in February 1983 and at four additional beaches along the bay in 1985. During the 1997-98 El Niño, several intense winter storms erodedbeaches along the bay, though not as severely as the 1982-83 El Niño storms.