A

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 026-00

2000

El Niño Storms Erode Beaches on Monterey Bay, California

REDUCING THE RISK FROM COASTAL GEOLOGIC HAZARDS

s recently as 1998, storms

generated by El Niños severely eroded beaches along

Monterey Bay, California. To

better understand the effects of

such storms, United States Geological Survey (USGS) scientists, in cooperation with the

California Department of Parks

and Recreation, have been actively monitoring changes in the

foreshore since the mid-1980’s.

The results of this study will

help protect coastal residents,

property, and environments and

are being used by the State of

California in guiding the management of public beaches.

Intense storms often produce abnormally high waves and elevated sea level,

causing extensive beach erosion and

shoreline retreat. The worst erosion generally occurs when multiple storms hit during periods of especially high tides. Several years may pass between storms

intense enough to cause shoreline erosion

that results in significant widespread damage. Although waves rebuild beaches after

such storms, this seaward accretion may

not return a beach to its pre-storm position,

requiring coastal-zone managers to consider

whether to take remedial measures.

During the winters of 1982-83 and

1997-98, two of the most severe El Niños

of the 20th century produced intense

storms that pounded central California.

These storms followed more southerly

tracks than usual and combined with periods of high tides to intensify the normal

winter erosional cycle, causing tens of

millions of dollars in damage along the

central California coast. On Monterey

Bay, coastal cliffs, dunes, and manmade

structures suffered serious damage, much

of it along the northern, most populated

part of the bay. To better understand the

effects of such storms, United States Geological Survey (USGS) scientists, in cooperation with the California Department of

Parks and Recreation (DPR), began actively monitoring changes at nine California State Beaches on Monterey Bay in

1983 and at four additional ones in 1985.

The extent of beach erosion or accretion

is measured by landward or seaward shifts

in the position of the shoreline at mean sea

level (MSL). Storm waves during the

1982-83 El Niño had stripped large volumes of sand from Monterey Bay beaches,

leaving beachfront 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 than before. For 2 years,

normal wave activity deposited sand, rebuilding the beaches. However, there is no

way of knowing whether the beaches returned to near their pre-El Niño states, because no data had been collected on their

profiles before 1983. In succeeding years,

the beaches went through several erosional

and depositional cycles. From 1985

through September 1997, all but two

Monterey Bay beaches remained stable

except for normal seasonal fluctuations.

During the 1997-98 El Niño, several intense winter storms from the south struck

the Monterey Bay coastline. However,

beach erosion along the bay was less than

in the 1982-83 El Niño, and not a single

Monterey Bay beach was eroded so severely in 1997-98. For example, at

Seacliff State Beach on the northeast

coast of the bay, which is most susceptible

Waves generated by severe winter storms

during the 1982-83 El Niño destroyed the

wooden seawall at Seacliff State Beach on

California’s Monterey Bay. The barrier of

large stones that had been emplaced

seaward of the wall was also scattered by

the waves (photo above). The photo at

right, taken 2 years after these storms,

shows the replacement seawall and rebuilt

beach. This seawall remained intact during

the 1997-98 El Niño.
Printed on recycled paper

John R. Dingler

Graphic design by

Susan Mayfield and Sara Boore

For more information contact:

U.S. Geological Survey, MS-999

345 Middlefield Road

Menlo Park, CA 94025

(650) 329-5042

http://marine.usgs.gov/

See also El Niño Sea-Level Rise Wreaks Havoc in California’s

San Francisco Bay Region (USGS Fact Sheet 175-99)

COOPERATING ORGANIZATION

California Department of

Parks and Recreation

to waves from the south, erosion during

the 1997-98 El Niño was no more severe

than during some non-El Niño years.

Only two beaches appear to have undergone net retreat since 1983. One, Moss

Landing State Beach, is adjacent to the

head of Monterey Submarine Canyon, a

factor that complicates interpretations of

long-term shoreline retreat because sand

eroded from the beach may move down

the canyon and be lost to the deep sea. The

other, Fort Ord Beach, is narrow and backed

by a high, but easily eroded, cliff. In most

years, winter storm waves erode the beach

to the extent that they can attack the cliff.

Consequently, the shoreline has retreated an

average of 1 to 2 yards (meters) per year

since USGS monitoring began in 1983.

However, the summer beach continues to

maintain nearly the same shape and width as

it migrates landward.

The cooperative efforts of USGS scientists and the DPR at Monterey Bay’s

beaches have led to a better understanding

of how these beaches change during both El

Niño and non-El Niño years. The results of

these ongoing studies are being used by the

DPR to help guide the management of public beaches along Monterey Bay. They will

also provide new insights into how beach

erosion occurs in other coastal areas. To improve that understanding further, the USGS

will continue to collect and analyze data

from these beaches. The work of USGS scientists in the area of Monterey Bay is only

part of the USGS Coastal and Marine Geology Program’s ongoing efforts to protect

people’s lives and property from geologic

and environmental hazards in the coastal

zones of the United States.

During 1982-83 El Niño storms, Seacliff State

Beach on California’s Monterey Bay was severely eroded. Cross-shore profiles obtained by

U.S. Geological Survey scientists show that

normal wave activity in succeeding years

deposited sand, rebuilding the beach. The first

profile (February 1983) was made at the same

time as the photograph on the front of this

sheet. Wave conditions governed the depth to

which the profiles extend below mean sea level

(MSL). Erosion at Seacliff State Beach during

the 1997-98 El Niño was no more severe than

during 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 measured

by landward or seaward shifts in the position of the

shoreline at mean sea level (MSL). Storm waves during

the 1982-83 El Niño had stripped large volumes of sand

from Monterey Bay beaches, leaving beachfront

9

Monterey Bay

State Beaches

(see map for locations)

8

7

6

5

4

3

2

1

YEAR

SHORELINE SHIFT AT MEAN SEA LEVEL

1984 1986 1988 1990 1992 1994 1996 1998

Building seaward

Eroding landward 100 METERS

CALIFORNIA

Area

of map

Seacliff State Beach New Brighton

State Beach

1

2

3

12

4

5

6

10

7

8

9

13

11

Manresa State Beach

Sunset State Beach

Zmudowski State Beach

Moss Landing State Beach

Salinas River

State Beach (north)

Salinas River

State Beach (mouth)

Marina State Beach

Fort Ord Beach

Sand City Beach

Pt Piños

500 m

100 m

Pt Santa Cruz

Del Monte Beach

First surveyed 2/83 Monterey State Beach

MONTEREY

SANTA

CRUZ

M O N T E R E Y

B

A

M

Y

ONTEREY CANYON

0 5 MILES

0 5 KILOMETERS

0 50

2

METERS

METERS

Mean sea level

Profiles of Seacliff State Beach

1983 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 than

before. U.S. Geological Survey scientists, in cooperation with the California Department of Parks and Recreation, began actively monitoring changes at nine

Monterey 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 eroded

beaches along the bay, though not as severely as the 1982-83 El Niño storms.