Rates of Landsliding and Cliff Retreat Along the Big Sur 

Coast, California—Measuring a Crucial Baseline

SUPPORTING SOUND MANAGEMENT OF OUR COASTS AND SEAS

the rates and processes of erosion, 

transportation, and deposition of 

slope material to estimate the annual 

volume of sediment (sediment 

yield) that enters the MBNMS from 

landslides. This research aims to 

assist the efforts of Federal and 

State agencies in coastal planning.

Why Is the Big Sur Coast Prone to 

Landsliding?

In the Big Sur area, earthquakes 

can result in uplift of the Santa Lucia 

Mountains. Recurrent uplift, in combination with relentless erosion by ocean 

waves, creates extreme topography, 

making the area highly susceptible 

to landslides. Rocks that have been 

weakened through faulting and fracturing also help provide ideal conditions for large landslides. During the 

winter months, Big Sur receives both 

heavy rainfall (as much as 80 inches 

per year) and high wave energy. In 

summer and fall, occasional wildfires 

remove vegetation, making the area’s 

slopes more vulnerable to erosion. All 

these factors produce chronic landslides, such as those that block, undermine, or damage the Coast Highway. 

For example, a 1983 landslide near 

Julia Pfeiffer Burns State Park resulted 

in closure of the highway for more 

than a year. Subsequent repairs cost 

more than $7 million and generated 

nearly 3 million cubic yards of debris.

In all, more than 1,500 landslides 

have been mapped along the Big 

Sur coast. The most common type 

of landslide in this area is a rockslide, which is a slow-moving or 

Along central California’s 

Big Sur coast, the rugged Santa 

Lucia Mountains descend abruptly 

into the Pacific Ocean. Millions 

of visitors travel annually along 

the Coast Highway (California 

Highway 1) to explore the area’s 

dramatic topography, ancient 

redwood forests, and unique marine 

habitats, bringing many millions 

of dollars to the local economy.

Maintaining safe access along the 

Coast Highway is essential for both 

tourism and the livelihood of local 

residents. However, Big Sur’s extreme 

topography makes the area highly 

susceptible to landslides. Landslides 

frequently block the highway, and 

because disposal of landslide debris 

into the adjacent Monterey Bay 

National Marine Sanctuary (MBNMS) 

could damage critical marine 

habitats, maintenance of the highway 

is expensive and controversial.

U.S. Geological Survey 

(USGS) scientists are studying 

California Department of Transportation (Caltrans) crews work to reopen Highway 1 at Pitkins 

Curve during winter 2004. When this photograph was taken, one lane of the highway was still 

closed (note boulders at lower left behind the traffic barricade). This site is currently the most 

active landslide on the Big Sur coast. (USGS photograph by Cheryl J. Hapke.)

U.S. Department of the Interior

U.S. Geological Survey

USGS Fact Sheet 2004–3099

2005

Steep topography, active faults,  diverse geology, and 

seasonal storms combine to 

make the rugged Big Sur area 

one of the most landslide-prone 

stretches of the California 

coast. Landslides in Big Sur 

frequently damage the popular 

and economically essential 

Coast Highway and may impact 

nearshore marine life. To assist 

State and Federal agencies in 

managing this coastline, U.S. 

Geological Survey (USGS) 

scientists are studying the 

processes and effects of landsliding and coastal retreat in 

Big Sur.
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California’s Big Sur coast is characterized by 

several rock types, which greatly influence rates 

of coastal erosion. Important rock types include 

granitic rocks, sedimentary rocks, and melange 

(a jumbled mixture of tectonically broken and 

crushed rocks). This map shows the results of 

U.S. Geological Survey studies of rates of sediment-yield (outer color band) and cliff-retreat 

(inner color band) at nine sites along the Big Sur 

coast. The highest rates were found along the 

southern part of the coast, where the weakest 

rocks occur. In addition, three large landslides 

(red stars) were studied in much greater detail.

“creeping” landslide in weathered, 

fractured, or otherwise-weakened 

rock. Movement on deep-seated 

rockslides typically is only fractions of an inch per year; however, 

an increase in rainfall or slope instability can accelerate movement 

to several yards a minute or faster.

Long-Term Rates of Landslide 

Movement

USGS studies of the rates of 

landslide movement along the Big 

Sur coast are providing data essential 

to effective management of the Coast 

Highway. For example, the longterm average annual sediment yield 

from movement on large landslides 

along the coast is approximately 

25,000 cubic yards per mile, a volume 

equivalent to more than 2,700 dumptruck loads. In addition to these high 

rates of material loss, cliff edges are 

retreating landward at an average rate 

of about 7 inches per year.

EROSION RATES AND ROCK TYPES ALONG THE BIG SUR COAST

Both sediment-yield and cliffretreat rates vary significantly along 

the Big Sur coast, partly because of 

its complex geology. Lower rates 

generally occur within granitic 

rocks, which are less faulted and 

fractured, whereas higher rates occur 

where weaker, sheared and fractured 

sedimentary and metamorphic 

rocks of the “Franciscan Complex” 

are dominant. In addition to rock 

strength and type, other factors also 

influence coastal-cliff erosion and 

movement on deep-seated landslides, 

including the previous history of 

slope disturbance (natural or human), 

the distribution and density of faults 

and fractures, variation in rainfall, 

and protection (or lack thereof) at the 

slope base by beaches or debris fans.

Although the average rates of 

sediment yield and cliff retreat are 

useful for long-term planning in 

coastal management, landslides 

are generally localized and highly 

episodic. In a single year, one large 

slope failure can account for most 

of the sediment yield or cliff retreat 

within a given area over a decade 

or longer. Owing to this episodic 

activity, average rates provide little 

information as to how much material 

may be eroded or deposited during 

any given year or even over the 

course of a decade.

Short-Term Rates of Landslide 

Movement

To better understand landslide 

rates and processes, as well as 

sediment yield, along the Big Sur 

coast, USGS scientists documented 

the short-term (decades long) rate of 

movement and the evolution of three 

large chronic landslides (Hurricane 

Point, Big Slide-Pitkins Curve, and 

Grayslip). The focus of this study was 

to quantify the variation in the rate 

of sediment input to MBNMS waters 

directly from coastal landslides, 
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Hurricane Point

landslide

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Big Slide

landslide

Pitkins Curve

landslide

Grayslip

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SITE-SPECIFIC ANALYSES OF CHRONIC LANDSLIDES

To better understand landslide processes along the Big 

Sur coast, U.S. Geological 

Survey scientists studied 

three chronic landslide 

areas—Hurricane Point, 

Big Slide-Pitkins Curve, and 

Grayslip. Using computer 

analysis of aerial photographs taken over three short 

time intervals (1976–86/87, 

1986/87–93, and 1993–2001), 

the scientists calculated 

vertical changes in topography, or “material-loss rate,” over time (for example, see 

Calculating Material-Loss Rates at right). 

The results indicate that net loss rates 

vary substantially along the coast. The bar 

graphs show that loss rates are lowest 

at Hurricane Point, which is within less 

fractured and faulted rocks. The graphs 

also show that in the interval containing 

the 1997–98 El Niño, loss rates at all three 

sites increased by an average of 5 inches 

per year from the preceding interval. 

(Photographs copyright by Kenneth Adelman, California Coastal Records Project, 

http://www.californiacoastline.org/.) 

and to characterize the processes 

responsible for sediment delivery.

For this study, three-dimensional 

topographic models were created 

from aerial photographs over three 

time intervals (1976–86/87, 1986/87–

93, and 1993–2001) spanning a total 

of 25 years. Computer analysis of 

these models using a geographic 

information system (GIS) showed 

that net short-term rates of material 

loss vary substantially along the 

coast, apparently in relation to 

both local rock types and climatic 

triggers. For example, the loss rates 

at Hurricane Point, which is within 

less fractured and faulted rocks, are 

the lowest of those at the three sites, 

whereas the loss rates within weak 

rocks at the central and southern 

sites (Big Slides-Pitkins Curve and 

Grayslip landslides, respectively) are 

the highest. 

Historically, landslide activity 

greatly increases during large El 

Niño years (for example, 1940–41, 

1982–83, and 1997–98). The time 

intervals within this analysis that 

contain two of the largest recorded 

El Niño events also showed greatly 

This series of 

images of the 

Big Slide-Pitkins 

Curve landslide 

area shows where 

material has been 

eroded (red) or 

deposited (blue) 

owing to landslide 

movement during 

three time intervals 

from 1976 to 2001. 

Material-loss rates 

are derived by 

dividing the change 

in elevation in 

yards (DZ) by the 

number of years in 

the interval.

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Calculating Material-Loss Rates
Rocky substrates in the 

nearshore waters of 

Monterey Bay National 

Marine Sanctuary 

provide essential habitats for many marine 

species. Along the Big 

Sur coast, both natural 

landslides and human 

activities can introduce large volumes of 

sediment into sanctuary waters, potentially 

impacting these habitats. This may affect 

not only bottom-dwelling species—including 

anemones, starfish, 

and sea urchins—but 

also the animals that 

feed on them, such as 

the southern sea otter, 

a protected marine 

mammal.

protecting the natural resources 

along this evolving coastline. Such 

research is only one part of the 

USGS’ efforts to protect people’s 

lives and property from geologic 

and environmental hazards in the 

coastal zones of the United States.

For more information, contact:

U.S. Geological Survey

Western Coastal & Marine Geology

Pacific Science Center

400 Natural Bridges Dr.

Santa Cruz, CA 95060

(831) 427–4747

http://walrus.wr.usgs.gov/

This Fact Sheet and any updates to

it are available online at

http://pubs.usgs.gov/fs/2004/3099/

increased net material-loss rates, 

especially the interval containing 

the 1997–98 El Niño, when loss 

rates increased by 5 inches per 

year from the earlier non-El Niño 

interval (1986/87–93). At all three 

sites, movement on large creeping 

landslides mobilized material and 

deposited it on the lower slope or 

slope base. Subsequent smaller 

failures in the loose material, as well 

as wave erosion at the slope base, 

resulted in a net loss of material to 

the nearshore environment, ranging 

from about 4 to 7 inches per year.

Could Landslides Be Affecting 

Nearshore Marine Habitats?

Landslides and coastal-cliff 

erosion contribute material to 

adjacent ocean waters. Deposition 

of large amounts of sediment and 

increased suspended-sediment 

concentrations may pose a threat 

to some marine life. However, 

restricting sediment input could also 

harm the nearshore environment 

because debris from coastal erosion 

and landslide activity also supplies 

nutrients and provides a natural 

buffer to protect cliffs from erosion 

by wave attack.

By studying the volume of 

sediment that has historically entered 

MBNMS waters from landslide 

movement and coastal-cliff retreat, 

USGS scientists are providing a 

sediment-yield baseline against 

which the impact of human activities 

along the Big Sur coast can be 

evaluated by coastal planners. Before 

the MBNMS was established in 

1992, both natural landslide debris 

and excess material generated from 

efforts to stabilize slopes were 

sometimes deposited on the seaward 

side of the highway to clear it for 

traffic. This material could then 

be carried downslope and into the 

MBNMS, disrupting nearshore 

habitats. 

Coastal landslides continue 

to be problematic along the Big 

Sur coast and in other similar 

high-relief sections of the Pacific 

coast. USGS research will help in 

the development of new coastalmanagement practices designed to 

minimize environmental impacts, 

while preserving the beauty and 

Printed on recycled paper

Cheryl J. Hapke and Krystal R. Green

Edited by

George A. Havach, James W. Hendley II, 

and Peter H. Stauffer

Graphic design by

Susan Mayfield and Stephen L. Scott

COOPERATING ORGANIZATIONS

California Department of Transportation

Monterey Bay National Marine Sanctuary

University of California, Santa Cruz

BIG SUR LANDSLIDES MAY THREATEN NEARSHORE MARINE LIFE

Anemones and Starfish

Sea Otter

(USGS image)

(NOAA image)

(NOAA image)

Sea

Urchin