Geology part of a study [of] the California Coastal Zone : summary of the report, Coastal geology and geological hazards

[From the U.S. Government Printing Office, www.gpo.gov]

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GEOLOGY

Part of a Study the California Coastal Zone

Summary of the report: "ICoastal Geology and Geological Hazards",
compiled by State and Regional Coastal Zone Commission staff, with
extensive assistance from Ms. Elene Johnston and Mr. William Adent.
Regional information was prepared in cooperation with Dr. Ken Lajoie
and Dr. Gary Greene of the U.S. Geologic Survey, Menlo Park.

The California Coastal Zone Conservation Act of 1972, (Prop-
osition 20 at the election of November 7, 1972) created the
California Coastal Zone Conservation Commission and six Re-
gional Commissions, and directed them to prepare a comprehen-
.sive, enforceable plan for the preservation, protection,
restoration, and enhancement of the coastal zone.

This is one of a series of informational reports designed to
help the Central Coast Regional Commission carry out this
responsibility. Using these reports, the Regional Com-
mission will develop recommendations to the California Coast-
al Zone Conservation Commission on statewide policy to this
Region. These recommendations, together with the recommenda-
tions of the other five Regional Commissions, will be the
basic materials the State Commission will use in planning
the plan for the future of the California coast.

Each report focuses on a specific aspect of the Coastal Zone.
The relationship of this report to others in the series may
be seen at a glance on the next page.

This summary report was prepared by the Commission staff to
focus on the most important Coastal planning considerations
suggested by the more extensive technical report. Possible
planning recommendations based on this report are listed at
the end. These are only tentative, since the conclusions
based on this report will need to be considered later, after
other reports on different aspects of the Coastal Zone have
been completed.

Cover Photo: Jack Mclowell

CENTRAL COAST REGIONAL COMMISSION

SANTA CRUZ

April 1, 1974
U.- S - DEPARTMENT OF COMMERCE NOA A
COASTAL SERVICES CENTER
42234 SOUTH HOBSON AVENUE
Property of CSC Xsibrary CHARLESTON , SC 29405-2413

PREFACE

This report is the second of nine elements of the Coastal Plan
covering the following subjects:

1. Marine Environment
2. Geology
3. Coastal Land
4. Appearance and Design
5. Recreation
6. Energy
7. Transportation
8. Intensity of Development
9. Powers, Funding and Governmental Organization

The Central Coast Regional Commission is responsible for planning
the coastal region of San Mateo, Santa Cruz and Monterey Counties.
In order to encourage public participation, the Commission will hold
public meetings to discuss the implications of this report at:

Monterey Peninsula College Skyline College
Monterey County San Mateo County
Social Science 102 Building 2, Room 308
Friday - April 19, 1974 Friday - April 26, 1974
7:30 P.m. 7:30 p.m.

Board of Supervisors Chambers
Santa Cruz County Governmental Center
Monday - May 69 1974 (Formal Public Hearing)
7:30 p-m.

This summary is abstracted from an extensive technical report cover-
ing statewide and regional issues. Copies of the technical report are
available for review at the Commission office or at the following public
and school libraries:

San Jose State University University of California
Main Library Santa Cruz
125 - 7th Street Library
San Jose, California 95112 Santa Cruz, California

Cabrillo College Monterey Peninsula College
Library Library
6500 Soquel Drive 980 Fremont
Aptos, California Monterey, California

Hartnell College Skyline College
Library Library
156 Homestead Avenue 3300 College Drive
Salinas, California San Bruno, California

San Mateo County Library Monterey City Library
Central Branch Madison & Pacific Streets
25 Tower Road Monterey, California
Belmont, California

Santa Cruz Public Library Monterey County Public Library
Main Branch 26 Central Avenue
224 Church Street Salinas, California

Half Moon Bay Branch Pacific Grove Library
Public Library Central Avenue & Fountain Avenue
620 Correas Avenue Pacific Grove, California
Half Moon Bay, California

Emerson Branch Library Watsonville Public Library
Elm Avenue & Imperial 310 Union
Seaside, California Wat sonville, California

Daly City Public Library Pacifica Branch Public Library
Westlake Main Branch Hilton Way & Palmetto Avenue
275 Southgate Avenue Pacifica, California
Daly City, California

Harrison Memorial Public Library
Ocean Avenue & Lincoln
Carmel, California

See last page of this summary to obtain a copy of the technical report.

� Shattered windows, cracked walls? and debris covered
roads after a quake -

� Houses slipping hopelessly down a slope on a mud
slide-

* Whole sections of a coastal city battered by massive
sea waves-

* A favorite beach stripped of its sand, perhaps dumping
a nearby house into the ocean -

Earthquakes, landslides, tsunamis (earthquake-born sea waves)

and shoreline erosion - these are the four major geologic hazards of

California's Coastal Zone.

Most Californians have seen, or even experienced, the effects

of these dramatic natural forces. While these forces are largely

unpreventable, and are essential steps in the constant geologic

evolution of the earth, they need not exact extensive cost in lives,

injuries, and property damage. As more and more is learned about

these geologic processes? homes, roads, office buildings and other

construction in our urban civilization can be located in safer places,

and be constructed in order to withstand these natural forces.

With wise planning, major coastal geological hazards can be dealt

with in a way which will enable people to continue to enjoy working,

living, and -visiting along the beautiful California coast.

Earthquakes

California is earthquake country. Earthquake shaking is the most

widely experienced of all the State's geologic hazards. Most of the

time it does little damage because the vast majority of earthquakes

are small. In fact, California experiences literally thousands of

earthquakes every year, but most are too small to notice or cause

any noticeable damage.

The most noticeable effect of' small earthquakes is "creep" along

faults in the earth's crust, the best known of which is the San Andreas.

The periodic slow movement or "creep" is thought to relieve tensions

within the earth that might otherwise build up as huge blocks of the

crust move in opposite directions to one another. Creep may gradual ly

bend and damage structures that lie across the fault line.

Large damage from earthquakes occurs when movement along a fault is

sudden, rocking buildings on the fault itself, shaking surrounding areas,

triggering landslides on unstable slopes, and even liquefying certain

wet soils.

Earthquake damage varies according to the intensity and duration of

the shock, the type of soil affected, and how close cities are to the

earthquake center (epicenter). The last large California earthquakes

struck the San Fernando Valley in Southern California in 1971, with 58

people killed and much damage; a more recent earthquake hit Pt. Mugu in

February 1973 with relatively little damage, The California Division

of Mines and Geology estimates that earthquake shaking damage will reach

$21 billion throughout'the State of California between 1970 and 2000.

Earthquakes are particularly damaging in the coastal zone because

of the large population centers along the coast. Both San Francisco

and Los Angeles are located near the San Andreas Fault, and many

other offshoot or "splinter" faults are near coastal cities. But the

hazard varies from region to region along the California coast and its

islands.

California recorded history of earthquakes is too short (barely

150 years) and spotty to give a complete picture of the earthquake

threat along the coast. Accurate equipment to measure the quakes'

location and intensity is still being refined, and mapping continues

in large areas of California thought to be earthquake prone. This

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research and mapping should be encouraged if California is to under-

stand and cope with the earthquakes and their effects.

The Alquist-Priolo Geologic Hazards Zones Act passed in 1972 calls

for extensive mapping and research of known and potentially active

fault areas. As this Act is implemented, earthquake risks in certain

areas will be better known and development can be guided accordingly.

For example, if a valley is known to have several earthquake faults,

it might be safe to use the land for farming, but not for building

a new factory.

The Joint Committee on Seismic Safety of the California Legislature

in 1972 recommended the strict enforcement throughout the State of the

Uniform Building Code to avoid shoddy construction and engineering

techniques. The Joint Committee also recommended expanding the Alquist-

Priolo Geologic Hazards Zones Act of 1972 to include all geologic

hazards beyond just earthquakes.

As the Joint Committee indicated there must be continued mapping

of fault zones and research into causes and prediction of earthquakes,

and also specific examination of pieces of land before development

begins.

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CENTRAL COAST REGIONAL SUPPLEMENT

Faults:

The San Andreas fault system is one of the largest and most seis-

mically active structures in the earth's crust. The Central Coastal

Region is transected at its northern extremity by the San Andreas

fault zone itself and by one of its main branches, the Seal Cove -

San Gregorio - Palo Colorado fault zone, throughout much of the region.

The San Andreas fault crosses the Central Coastal Zone in Daly City and

lies within 15 miles of the coastline north of Salinas and within 40

miles of the coastline from Salinas to the Monterey - San Luis Obispo

County line. Because of its close proximity and potential for gener-

ating large damaging earthquakes, the San Andreas fault presents the

source of seismic hazard in the Central Coastal Zone.

The Seal Cove - San Gregorio - Palo Colorado fault zone branches

off the San Andreas fault at Bolinas Lagoon in Marin County and extends

over 100 miles southeastward to the vicinity of the Monterey Peninsula

(Figure 9). Recent minor seismicity, young geomorphic fault features,

offsets of geologically young sedimentary deposits, and close relation-

ship to the San Andreas fault indicate that this is an active fault

zone. The length of this fault zone and its activity suggest that

earthquakes as large as magnitude 7O0.5 can be expected from movements

along this fault zone (Green, et. al, 1973).

Between Bolinas Lagoon and Moss Beach in northern San Mateo County

this fault zone lies offshore and was mapped by acoustic profiling

from a ship. Between Montara and Princeton at the north end of Half

Moon Bay the fault zone lies onshore and is expressed by a main strand

called the Seal Cove fault, which runs along the base of the high

linear ridge called the Seal Cove Bluffs west of the Half Moon Bay

Airport, and several minor strands to the east. Vertical displacement

-5-

of up to 150 feet on the Seal Cove fault has offset the lowest and

youngest emergent marine terrace in the region (the Half Moon Bay

terrace which is most likely 70,000 to 120,000 years old) and elevated

the block west of the fault to form the Seal Cove Bluffs. The linear

northeastern face of the Seal Cove Bluffs is therefore a fault scarp.

Displacements on secondary fault strands east of the Seal Cove fault

have offset several emergent marine terraces. Displacement on one

secondary strand which runs through a brussels sprout field east of the

Half Moon Bay Airport has offset a recent alluvial fan (less than

5,000 years old) and formed a westward facing scarp up to four feet

high.

Between Princeton and San Gregorio, 13 miles to the southeast, the

Seal Cove - San Gregorio - Palo Colorado fault zone again lies offshore.

The fault zone is expressed as a series of linear ridges on the ocean

floor across the mouth of Half Moon Bay but its location is not pre-

cisely known between Miramontes Point and San Gregorio.

Between San Gregorio and Point Ano Nuevo, 17 miles to the southeast,

the fault zone lies onshore and is expressed as a broad complex zone of

bedrock displacements, sag ponds, and linear ridges and valleys. The

Ano Nuevo terrace, the lowest and youngest marine terrace in this area,

(most likely between 70,000 and 120,000 years old) is offset and tilted

by displacements along several fault strands. Alluvial deposits about

10,000 years old have been offset by displacement on a fault strand

near the mouth of Ano Nuevo Creek.

Between Ano Nuevo Point and the vicinity of the Monterey Peninsula,

the fault zone lies offshore and was mapped by acoustic profiling from

ship-mounted equipment (Green, et. al., 1973). Displacements on fault

strands in this area have offset marine deposits less than 5,000 years

old and formed linear scarps on the ocean floor.

-6-

South of the Monterey Peninsula the fault zone comes ashore and is

represented by the Palo Colorado fault which was mapped primarily on

the basis of bedrock discontinuities.

In addition to the main coastal fault, the Seal Cove - San Gregorio -

Palo Colorado fault zonex there are several other faults which show

evidence of fairly recent geologic activity. Displacement on the

Pilarcitos fault which branches off the San Andreas fault near Palo Alto

has offset the lowest marine terrace (probably 70,000 to 120,000 years

old) north of Pedro Point. Displacement on several fault strands in

the broad Monterey Bay fault zone, which runs diagonally across the

floor of Monterey Bay, offset marine deposits less thani 5,000 years

old and have formed scarps on the ocean floor (Green, et. al., 1973).

Southeastward extensions of some of these fault strands offset young

marine terrace deposits (70,000 to 120,000 years old) east of the

Monterey Peninsula.

Seismicity:

The San Francisco Bay region is one of moderately high seismicity,

largely associated with the San Andreas fault. Three major earth-

quakes related to this fault have resulted in damage or potentially

damaging intensities on the coast between San Francisco and Santa

Cruz. Only one earthquake on the Hayward fault (in 1868) has similarly

affected the coast (Eppley, 1966). Seismicity on the San Andreas

fault on the San Francisco Peninsula takes the form of infrequent

large and small earthquakes, with apparently almost no intermediate

shocks (exception is the Daly City shock, M=5.7, of 1957).

Small earthquakes and microseisms during the past 30 years were

generally restricted to the San Andreas fault south of State Highway

152 between Gilroy and Watsonville but many occurred along faults through-

out a broad area along the entire coastal zone (Figure 9).

7 -

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Towns on the east side of the Peninsula were severely damaged

in the 1906 earthquake (VIII to IX intensity) (Lawson et al., pp. 246-

270) because they lie quite near the San Andreas fault and are partly

situated on soft ground, principally mud of San Francisco Bay. On

the coast, intensities ranged from V to X, depending on distance from

the fault and ground conditions. Between Lake Merced and a point

about one mile south of Mussel Rock, in the area now occupied by

Daly City and Edgemar, intensities were IX and X. From there to

San Pedro Point, including what is now Pacifica and Sharp Park, the

intensity was VIII; from San Pedro Point to Montara Point intensity

was VII. The Half Moon Bay area, from Moss Beach to Martin's Beach,

experienced intensities of VII to IX-, reflecting the softness of

Pleistocene marine terrace deposits there; the highest intensity

(VIII to IX-) occurred along four miles of coast west of and including

the town of Half Moon Bay. Intensity VII occurred in the San Gregorio

and Pescadero areas to the south, also due to soft ground. South of

Pescadero to Santa Cruz, intensities of V and VI prevailed, due

chiefly to the presence of older, moderately consolidated surfical

materials.

Landslides and rockslides were triggered by the 1906 earthquake

at numerous points on the coast between Mussel Rock and Half Moon

Bay, the largest of these occurring in the vicinity of Devil's Slide

(Figure 9).

The area just east of Monterey Bay displays high seismicity local-

ized on the San Andreas fault, which lies from 10 to 25 miles east of

the bay margin. Seismic activity takes the form of frequent (one

every 5 to 10 years) medium shocks of intensity VI to VII with nearby

epicenters, as well as infrequent (about 2 per century) major earth-

quakes with intensity of VIII to X centered on the San Andreas and

- 9 -

Hayward faults to the north (Figure 9).

Epicenters of the major earthquakes of 1868 and 1906, and probably

that of 1838, were on the San Andreas fault north of Monterey Bay.

Surface faulting extended southward at least to San Juan Bautista

in 1906, and probably as far as Santa Cruz in 1838 and 1868. This

southward extension of faulting towards Monterey Bay has resulted in

high seismic intensities in that area. In 1906, the bay margin from

Santa Cruz to a point about halfway between Moss Landing and Pacific

Grove experienced intensity VIII to IX-. Pacific Grove and Monterey,

which are founded on granite, had intensity VI (no structural damage);

the area with intensity IX- is underlain by the soft sediments of the

Salinas River and Pajaro River deltas. The recent river channel

deposits were subjected to extensive cracking, lurching, and settling

of as much as several feet, causing damage to roads, bridges, piers,

railroads, and other structures.

About 12 moderate shocks with maximum intensities of VII and

VIII have occurred within 25 miles of the Monterey Bay margin (Eppley,

1966, p. 6), a few of which have caused minor to moderate damage

there, but no damage in Monterey. The 1838 earthquake may have had

intensity VII in Monterey, which appears to be the greatest ever

experienced in that town (Figure 9).

The coastal region from Point Sur to Point Conception is one of

relatively low seismicity. The Nacimiento fault zone, which appears

to be one source, extends from a point 10 miles east of Lopez Point

to a point 15 miles north of Santa Barbara, and is located from 5

to 40 miles inland. The San Andreas fault, 40 to 60 miles inland,

is the locus of greater seismicity; but only a great earthquake on

it would cause damage at the coast (as did the 1857 event).

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EXPECTED SEISMIC EFFECTS

Seismicity:

It is expected that the coastal zones of San Mateo, Santa Cruz

and Monterey Counties will continue to experience damaging intensities

from earthquakes generated on faults outside the immediate area as

well as from local faults. Displacements on the San Andreas fault

can be expected to generate earthquakes of magnitude greater than

8.0 and those on the Hayward fault and the Seal Cove - San Gregorio-

Palo Colorado fault can be expected to generate earthquakes with

magnitudes between 7.0 and 8.0.

There is presently no way to determine how frequently large damaging

earthquakes will occur on these faults or where and when the next

major earthquake will take place. Unfortunately, recent seismicity is

not a reliable key to future activity. For example, the segment of

the San Andreas fault that generated the 1906 San Francisco earthquake

is seismically relatively quiet, although most earth scientists agree

that it will generate large earthquakes in the future.

Small and intermediate earthquakes capable of causing local damage

in the coastal zone can be expected from minor faults throughout the

coastal ranges of San Mateo, Santa Cruz, and Monterey Counties as

well as from the San Andreas, Seal Cove - San Gregorio - Palo Colorado,

and Monterey Bay faults. Historical records indicate that these

earthquakes will occur much more frequently than major earthquakes

but, again, there is presently no way to predict their frequency

and location.

Ground Shaking and Ground Failure:

By far the greatest potential hazards presented by earthquakes

effecting the coastal zone are high levels of ground shaking (high

intensities) and ground failure.

The highest intensities will occur close to the faults on which

earthquakes are generated, and in areas underlain by thick accumu-

lations of unconsolidated deposits which amplify seismic waves.

The regions most likely to experience seismic amplification are pri-

marily the Pajaro Valley, the Elkhorn Slough area, and the Salinas

River Valley, and secondarily the Half Moon Bay area, and the Santa

Cruz,- Capitola area.

Ground failure due to abrupt surface rupture along fault traces

will be restricted to fault zones and will most likely accompany only

large fault displacements, primarily along the San Andreas fault.

Ground failure due to slow fault creep has not been observed along

any of the faults in the coastal zone.

Ground failure due to seismic shaking will occur on unstable

hillslopes and coastal cliffs (landslides), and on low-lying flood-

plains (lateral spreading and subsidence primarily due to liquefaction).

Landslides will probably range from rotational slumps to mudflows

on steep to gentle slopes and will include blockfalls along steep sea

cliffs. New landslides will probably be triggered by earthquakes

and many old landslides may be reactivated. All types of slope failure

will be more severe if earthquakes of high intensities occur during

the rainy winter season when the ground is saturated. Seismically

induced slumps may also occur in Submarine Monterey Canyon and could

generate local tsunamis.

The coastal regions most likely to experience liquefaction and

its related ground failures are those underlain by loose, water-

saturated alluvial deposits, the floodplains of Pescadero Creek, the

San Lorenzo River, the Pajaro River, Elkhorn Slough, the Salinas

River, the Carmel River, and numerous smaller coastal streams. The

high intensities attributed to these areas during the 1906 San Francisco

earthquake were probably due in part to the extensive ground failure

caused by liquefaction (Figure B). -12-

LIQUE.FACTION
* ROSSI-P9*k iltACLE

Landslides can be surprisingly destructive and fast moving such as

those in Big Sur Valley; fortunately, they are more predictable than

earthquakes. Most Californians have seen a home or road which has slipped

down a hill. Others have even waded through a street covered with mud

from a landslide. More often than not, these conditions could have been

avoided if landslide hazards had been known and acknowledged.

Landslides are an extreme form of a natural erosion process; the

down-slope movement of earth materials, primarily by gravity. W'hen

the earth material moves imperceptibly it is defined as "creep;" but

when movement is large and perceptible it is called a landslide.

The coastal zone of California may be somewhat more prone to

landslides than other areas of the State, due primarily to the

relative instability of coastal rock units and the additional periodic

fragmenting from earthquakes.

This is particularly true in seacliff areas, which are often battered

and undercut by ocean storm waves. The California Division of Mines

and Geology projects a total statewide property loss from landslides of

approximately $10 billion between 1970 and 2000. Much of this damage

will undoubtedly occur in the coastal zone.

Landslides can be classified according to type of movement, earth

material involved, and water content. All types of landslides occur

within the coastal zone and may in fact be more serious there because

of the many residential areas that continue to expand up hillsides and

perch on seacliffs, often without adequate pre-construiction analysis

of the land. Large storms, earthquakes, or accumulated ground water

can trigger a landslide, which has perhaps been camouflaged by vege-

tation or surface erosion.

-14-

The possibility of landsliding can often be determined before

it happens. Rock formations, soil types, water content, slopes, and

other factors can all be analyzed by geologists to identify potential

slide areas.* The results are compiled on "slope stability" maps.

Both the U. S. -Geological Survey and the California Division of Mines

and Geology have partially completed slope-stability maps for coastal

counties. Local governments may request these mapping projects, but

thus far the maps mainly cover areas of intense development.

The Joint Committee on Seismic Safety recommended strengt~hening the

Uniform Building Code to control construction in landslide-prone areas,

and also help local and county governments deal with landslide hazards.

If these recommendations were implemented, and followed-up by slope-

stability mapping and geologic analysis of property chosen for development,

the damages from landslides could be greatly reduced. (For example, proper

evaluation of landslide potential in Los Angeles County has virtually

eliminated damage from slides in areas developed under the new controls.)

Slope Stability in the Central Coast

Much of the Central Coast Region has experienced landslides, The

tenuous hold of Highway I through this Region is threatened by land-

slides in many sections. Aside from this graphic and costly example

of slope instability, many people are not aware of this hazard. In

the winter of 1968-1969, landslides caused. over 3--million dollars

damage in San Mateo County (U.S.G.S. Study by Taylor and Brabb).

Only San Mateo County has extensively mapped landslide potential

and used this information in their Planning policies. Their program

is a model not only for the Region but the State. Both Monterey and

Santa Cruz are compiling this information as part of their Seismic

Safety Elements of their General Plans.

-15 -

Tsunamis

Tsunamis (seismic sea waves) are caused by undersea earthquakes,

submarine volcanic eruptions or large underwater landslides. Tsunamis

can be terrifying natural forces, travelling at high speeds up to 400

miles per hour, with long periods (time interval between waves) and

huge breakers that form as the wave approaches shallow water. Coastal

cities bordering shallow water, such as Crescent City, are the most

unprotected from tsunamis. Seiches are shorter, lower energy waves

that form in smaller bodies of water such as bays and lakes.

Fortunately these seismic sea waves are rare events, and are

usually of tolerable heights. If they should coincide with high tides

or storm waves, however, their potential for damage in many coastal

areas is greatly increased. The California Division of Mines and

Geology has projected a tsunami damage of $41 million between 1970 and 2000.

There is no prevention of tsunamis, but their destructive impact

can be minimized by warning of their approach and wisely planning any

uses of tsunami runup areas. The National Oceanic and Atmospheric

Administration (NOAA) operates a successful tsunami warning system, and

the U. S. Army Corps of Engineers compiles tsunami runup maps for coastal

areas. These maps should be the difference between building anywhere

along the coast, and wisely avoiding the possible tragedy of seawater

flooding from a massive tsunami. These maps are being completed for all

coastal areas threatened by large waves, and can be further interpreted

with the aid of tsunami studies of local and State governments.

In the coastal zone of San Mateo, Santa Cruz, and Monterey Counties,

the areas most susceptable to tsunami innundation are the Southern

Pacifica area, the northern Half Moon Bay area, parts of the Santa Cruz

area, the lower reaches of Elkhorn Slough, parts of Monterey, and the

lower Carmel Valley (Figure A). A potential tsunami hazard also exists

where houses and other structures are built at the base of otherwise

protective cliffs, such as in the northern Monterey Bay region.
- 16-

Most tsunamis likely to effect this coastal area probably will be

generated in areas such as Alaska and South America. Tsunamis may also

be generated by sudden vertical displacements of the ocean floor

accompanying movements on local faults, or by submarine slumps in

Monterey Canyon.

Shoreline Erosion

Most Californians have noticed the loss of sand along a favorite

beach, or the more dramatic slippage of a cliff top home into the ocean.

Shoreline erosion is a natural process affecting all areas of the coast-

line, although at varying rates. Improper use of the shoreline may speed

up the erosion process, and result in damage to property that might have

been avoided.

Beach Erosion

Rivers and streams provide most of the sand to coastal beaches,

although cliff erosion accounts for most of the sand in isolated "pocket

beaches." Once the sand is deposited on beaches, it is transported on

and offshore by various sizes of waves, and alongshore by offshore

currents and the angling waves striking the beach. For example, the

large northern storm waves of winter remove sand from beaches and take

it out to sea and also push it south along the shore. In the summer,

the process is generally reversed, with sand once again being deposited

onshore, and being pushed north by southern waves. This seasonal

movement alongshore is called littoral drift.

Most beach sand moves along in distinct areas of the coast known

as "littoral cells." These areas usually receive their sand from a

river mouth toward the northern end of the cell, transport the sand

southward alongshore, until it is lost offshore into submarine canyons.

This cycle of sand deposition on beaches, alongshore transport, and

sand loss to the open sea is a constantly changing system.

Man-made obstacles such as breakwaters, groins, seawalls, and

harbor entrances impede the natural transport of' sand. It has been

learned that many facilities intended to retain sand in one place

often leads to accelerated erosion elsewhere and even to accelerated

loss of sand offshore so that beaches become permanently denuded.

Between reduction in the production of sand by coastal streams

due to dams and diversions (as discussed in the Coastal Land Environment

plan element) arid the premature loss of sand to the ocean because of

unanticipated effects of some shore protection works and channel dredging

projects, the Water Resources Council projects the annual loss due to

beach erosion in California to reach $15.7 million in 1980 and $26.7

million by 2000.

Other Shoreline Erosion

Beaches make up only 1/3 of California's coastline, with the re-

mainder comprised of cliffs, marshes, bluffs and other areas of varying

terrain and rock type. The continuous battering of waves against the

coastline erodes the land into an always changing shape. Some areas

erode very quickly, such as the 10 feet per year rate of erosion along

portions of San Mateo County's bluffs, and yet just a few miles away a

hard-rock headland will have negligible erosion.' Rainwater running off

the cliff also erodes the cliffs from the landward side, so that the

shoreline is assaulted from both directions. Ill-advised developments

along the shoreline often suffer the consequences of construction that

does not adequately anticipate local erosion problems,

Shoreline erosion processes are best left alone to constantly

alter the shoreline of California. These processes are not yet fully

understood; interference with them often cause s greater harm than

benefit.* The U. So* Army Corps of Engineers and the California Depart-

ment of Navigation and Ocean Development operate a cooperative program

-18 -

to study shoreline processes in areas of fast erosion. There are

also elaborate methods of reducing excessive erosion, such as sand

bypass systems, extensive dredging, and construction of improved shoreline

obstacles to control sand transport, but these tend to be prohibitively

expensive. The best way to maintain the sand supply is not to impair

natural shoreline processes. Coastline structures may impede local

sand supply and affect the entire littoral cell equilibrium so each

proposed project should be evaluated for its impact upon sand movement

in the whole cell, as well as for its effect on nearby areas.

Cliff Stability in the Central CoastRegion:

Coastal erosion is a dramatic process in the Central Coast

Region. The process of erosion is unrelenting; man may attempt to

prevent it, but his actions can only slow the process down. This

Region contains a variety of land formations on the oceanfront, and

the rate of cliff retreat varies from near zero to over ten feet a

years

A lack of measurable erosion does not tell the whole story.

Cliffs, beaches, and the sea exist in a delicate balance which can

be altered by covering or grading bluff tops, changing drainage

patterns, or removing the protective sand beach. When the balance

is broken, the sea traditionally advances on the land and cliff

retreat occurs. (See Figures D-FO

Since the erosion process itself is not completely understood,

efforts to control it often adversely affect surrounding features,

and may even increase erosion in some areas.

Seawalls of rip rap or concrete are the most common counter'-

measures used in the Central Coast Region. (See Figure C) These

structures deflect or defuse wave energy, but can also induce

-19 -

accelerated erosion on adjoining cliffs or loss of downd~rift beach

sand. In addition, they have a definite relationship to the issues

of recreational access and coastal aesthetics, for which future

Commission policies will be specifically developed.

The basic policy of this Commission should be that new develop-

ment will be designed with a bluff top set back far enough from the

cliff edge that no cliff protection will be required during an

economic life of 50 years. Cliff protection measures for existing

development will be considered on an individual basis. In both

cases the overriding concern is that development does not contribute

to the instability of any cliff or beach, and does not impose a

potential public hazard. The cliff stability maps and policy shall

serve as interim development guidelines. (See Figures I-M)

Steps Towards Reducing Geologic Hazards

The four geologic hazards of the coastal zone have one large

factor in common: earthquakes, landslides, tsunamis and shoreline

erosion destroy lives and property primarily because of inappropriate

uses of the land, The hazards are all natural processes. Research,

mapping, and changing government attitudes toward geologic hazards

are impairing man's ability to live with these phenomena.

Research and mapping of hazards - such as earthquake fault maps,

slope-stability maps for landslides, tsunami runup areas determined

by recurrence mapping, and erosion rate - allows the use of land to

be planned in a manner that minimizes avoidable risks. Also necessary,

however, is analysis of the specific site proposed for development.

In areas identified in any study as prone to geologic hazards a

geologic survey team including a design civil engineer, a soils

engineer, and an engineering geologist should analyze sites proposed

-20 -

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-21 -

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-27-

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-31 -

for any kind of construction and should prescribe site treatment

and building construction techniques capable of offsetting the hazard.

Where this has been done, damage has been reduced dramatically.

In addition the recommendations of the Joint Legislative

Committee on Seismic Safety should be implemented, key features of

which are to expend the provisions of the Alquist-Priolo Geologic

Hazards Act of 1972 to treat all geologic hazards, not simply earthquake

fault zones, through the mediumi of a Statewide Geologic Hazards Review

Board. The Uniform Building Code should also be enforced throughout

the State to ensure high quality construction capable of resisting

geologic hazards.

In the meantime, local governments that are not already doing so

and the Coast Commissions could improve the quality of their review

and approval of projects located in geologic hazard areas by employing

an advisory board composed of persons experienced in the several

disciplines that are concerned with aspects of geologic safety. To

adequately cover all the hazards, the board members should have expertise

in geology, geophysics, oceanography, soils engineering, engineering

geology? structural engineering, civil engineering and architecture.

For adequate project review and general advice concerning the four

hazards, an effective board should be empowered and staffed to carry out

with professional competence the following specific functions:

a. Re-view proposals for the adequacy of their specific earthquake

safety provisions, and make recommendations concerning these

provisions;

b. Establish and recommend earthquake safety criteria for structures;

c. Require installation and monitoring of such geophysical measuring

instruments as strong-motion accelerometers, seismographs? etc. on

any structure or urban development in the coastal zone to provide

vital new information on the effect of earthquakes on urban

developments. - 32-

d. Designate general types and causes of landslides and suggest

criteria for approval of construction;

e. Identify alluvial fan areas of particular hazard and suggest

appropriate development restrictions;*

�. Disseminate information regarding the nature and extent of

tsunami hazard to shoreline communities; and recommend standards

for marinas and harbors, including debris clearance, to reduce

damage from seismic waves;

g. Recommend a program for retention of a balanced sand supply for

California beaches, including criteria for shoreline structures

in view of their impact on wave currents and sand movement;

h. Develop guidelines for dredging of channel entrances to ensure

adequacy of their design to permit tidal scouring and avoid shoaling;

i. Suggest proposals for stabilization of coastal bluffs with special

consideration to the possible impact on beach erosion.

W~here specific policies or analysis of sites has warned prospective

builders of the geologic hazards of an area, and development proceeds

nonetheless, there should be no presumption of public liability for

private damage. That is, there should not be any public disaster loans

or grants afforded. in such case. Neither, as a practical matter, should

insurance be available if it is borne by other members of the public who

did not themselves undertake such risks.

Conclusion

Earthquakes, landslides, tsunamis, and shoreline erosion all pose

their separate dangers'to development in the coastal zone. By proper

analysis and precautions, damage from these hazards can be reduced

sharply. The coastal zone can be made a safer as well as attractive

place in which to live, work and play.

-33 -

Policies Checklist - Geology (Use back
Central Coast Regional Commission for
Comments)
California Coastal Zone Conservation Commission Commen
Strongly No Strongly
I would like to see: Agree Opinion Disagree

1. Geologic Safety Measures Necessary.

2. Safety of Projects Should be Individually Checked.

3. Statewide CGeologic Safety Measures Should be Upgraded.

4. Multi-Discipline Advisory Board Needed.

5. Interim Development Guidelines for Geologic Hazard Areas.

6. Interim Development Guidelines for Tsunami Runup Areas.

7- Interim Guidelines for Shoreline Protection and Channel Works.

8. Interim Coastal Erosion Guidelines.

9. Available Geologic Information Should be Fully Utilized.

10. Public Should Not Be Liable.

(Optional) Name Organization

Address

I wish to continue receiving Summary Reports. Yes No _

I wish to receive a copy of the Geology Technical Report. Yes No

Please clip and fold this page as directed on reverse side.

DRAFT
April 1, 1974

Tentative Findings and Policies to be Recommended by the Central

Coast Regional Commission to the California Coastal Zone Conservation

Commission, Based on the Report, Coastal Geology and Geological Hazards.

Findings

1.* Earthauake Hazard in the Coastal Zonee. Much earthquake activity
in California occurs within the coastal zone, which is part of the
earthquake-prone belt extending around the entire rim of the Pacific
Ocean. The coastal area contains many areas of highly complex
fault zones.

2. Unoredictability of Earthauakes. Every section of the coastal zone
has experienced earthquakes with various intensities. The
recorded history is too brief, however, for definitive assessment
of the earthquake frequency of any particular coastal section.
The absence of any high-intensity shock in an area in the past 175
years does not rule out the possibility, or at the same time give
reason to necessarily expect one.

3. Earthauake Research� Definitive studies of earthquake hazard and
probability are still sparse. The technology and volume of data
collecting is still in a state of development. Only the areas
of recent high-level earthquake activity have been intensively
studied. Instrumentation for detection and measurement is still
being developed or refined and seismic theory itself is in the
process of continual revision. Maps of earthquake faults only
indicate a portion of the quake-prone areas in the State.

4. Potential Earthauake Damage. The scale of earthquake shaking
hazard is indicated by the California Division of Mines and Geology
projection of $21 billion in damage statewide between 1970 and
2000. An uncertain amount of this damage would occur in the
coastal zone.

5, Legislation to Deal with Earthouakes. The Joint Legislative Com-
mittee on Seismic Safety has recommended broadening the provisions
of the Alquist-Priolo Act (which is limited to concern about con-
struction on or near fault traces) to encompass all geologic
hazards, and has further recommended the creation of a State
commission to establish and administer land use policies reflecting
geologic hazards. This proposed commission would not conduct
analysis of the geologic hazards of specific sites, however.

6. Landslide Hazard in the Coastal Zone. Much of the landsliding
activity in California occurs in the coastal zone, due to the
instability of the prevailing rock units and the steep-canyon
topography of the coastal ranges. Many types of landslides, both
ancient and recent, are observable, including rock falls, slides,
and slow and fast flows, but many have been obscured by erosion
and subsequent vegetation growth. Landslide causes include earth-
quake ground shaking, unstable rock formations, supersaturated
ground material due to sustained rainfall, and poorly planned
development of landslide-prone areas.

7. Problems of Flash Flood and Mudflows. A special problem in the
California coastal range is the potential for fast mudflows on canyon
walls and on the alluvial plain at canyon mouths. The potential for
these mudflows is greatly increased by sudden heavy precipitation
and by loss of ground cover, expecially from fire. Stabilization
of these flow-prone areas is virtually impossible, yet these sites
are often heavily developed, and suffer from later damage (i.eo,
Big Sur area in Central California).

8. Potential Landslide Damage. The California Division of Mines and
Geology projects a statewide loss of $10 billion due to landsliding
in the 30-year period after 1970, much of which will occur in the
coastal zone.

9 Necessity of Slope-Stability Determination. Landslide mapping is a
primary tool for assessing potential slope stability, while regula-
tion of land use and site preparation are the chief means of mini-
mizing slope stability hazards. At the present time, determination
of slope stability and related land use regulation are random and
imcomplete within the coastal counties. Mapping is normally under-
taken only when intensive development is contemplated and landslide
hazard is suspected. Regulation is normally adopted only after
damaging landslides occur.

10. Tsunami Hazard in the Coastal Zone. Large-scal� seismic sea waves
(tsunamis) in the Pacific Ocean Basin have caused some degree of
damage along much of the California coast, as with the great waves
that followed the 1964 Alaska earthquake.

11. Extraordinary Tsunamis. Nearshore earthquakes can generate localized
tsunamis, as with the Santa Barbara Channel event of 1812. That
great wave may have reached an estimated height of 50 feet at
Gaviota, the largest tsunami with some documentation on the California
coast. Slumping in Monterey Canyon is a potential source of local
tsunamis in the Central Coast Region.

12. Susceptibility to Tsunamis. Tsunami damage recurs in certain areas
of the California coast more than in others, generally where there
are shallow waters near the shore upon which waves can pile up.
Crescent City on the northern coast has been repeatedly damaged.
Various areas of the southern coast from Santa Barbara to San Diego
suffered damage from a 1960 tsunami caused by a Chilean earthquake,
and again from the great waves of 1964. Both these tsunamis struck
the southern coast at low tide; had high tide prevailed, damage
might have been much greater.

13. Coping with Tsunamis. Assessment of tsunami hazard on the California
coast is based on a brief and partial history. No such assessment
can anticipate future extraordinary events such as the Santa Barbara
.Channel earthquake and tsunami of 1812. Mapping of possible runup
limits now underway by the U. So Army Corps of Engineers for areas
of identified high tsunami risk can provide useful information for
land-use 'decisions in those areas; these maps can be augmented by
local and county studies.

14. Potential Tsunami Damage. The California Division of Mines and
Geology has projected a tsunami damage of $41 million between 1970
and 2000, based on present assumed hazards.

15. Beach Erosion Hazard in the Coastal Zone. Ocean beaches are one
of the most highly valued features of the California's coastal
environment. Many of these beaches are being lost by erosion due
to man's activities in the coastal zone. A primary cause of
accelerated beach erosion is reduction of the supply of sand to the
shoreline. Most beach sand is generated inland and delivered to the
shoreline by coastal streams, a process detailed in the Coastal
Land Environment element. This continued supply of sand has been
greatly impaired by upstream development activity, most commonly
by structures within the stream channel that block the transport
of sand (e.g., the annual delivery of sediments to Imperial Beach
has now been reduced to 1809000 cubic yards from an estimated volume
under previous natural conditions of 660,000 cubic yards).

16. Shoreline Sand Supply. The shoreline sand supply is transported
by waves and wave currents in three kinds of movement-offshore,
onshore, and longshore. The sand moves laterally along the shore,
usually southward; as it is being transported offshore and returned
onshore. The sand movement along the shore occurs within sections
of the coast? referred to as "littoral cells." These extend from
the point where the sand supply is introduced, mostly by streams,
downdrift to the place where it is swept out to sea, often into
offshore canyons. There sometimes are small indentations in the
coast within cells, isolated from the sand movement system of the
rest of the cell by rocky headlands. Within these areas, cliff
erosion and onshore currents probably supply the sand to small
pocket beaches.

17. Man's Impact on Sand Sul. The stability of sand beach depends
on maintaining the equilibrium of a sand budget-a balance between
supply and removal (the loss of sand to wave action) within a cell
or pocket beach area. Man's activity has not only reduced the
supply, it has also increased the loss through faulty design of
groins, jetties, breakwaters and dredged channel entrances in
shoreline waters.

18. Potential Shoreline Erosion Damage Damage due to beach erosion in
California was approximately $10 million in 1965. The Water Resources
Council projects the annual loss to be $15.7 million in 1980 and
$26.7 million by 2000, unless large-scale preventive measures are
taken. These measures may cost over $1 million for a single beach
area.

19. Maintaining Sand Supoly. Several measures for increasing the sand
supply are:
a. Mining offshore submarine fans and canyon heads.
b. Placing harbor dredge material on beaches downdrift from the
harbor entrance.
c. Transporting material from behind inland dams and other inland
sand sources to depleted beaches by increasing dam release of
water and sediment by-pass, or by transportation to the affected
beach areas by truck. However, all these processes are extremely
expensive.
Among other methods for decreasing sand loss from beaches are:
a. Engineering structures such as riprap, seawalls, groins and
detached breakwaters.

b. Engineering devices such as created submerged reefs and perched
beaches (coarse sand placed atop an existing beach).
co Careful design of channel entrances to embayments to maintain
equilibrium between entrance size and tidal prism.

20. Erosion of Seacliffs. The breakdown of seacliffs by wave action
is a natural and constant process, the rate depending on the resis-
tance of the cliff material, the conformation of the shoreline and
the height of the cliff. These processes are extremely complex and
should not be tampered with unless irreplaceable coastal resources
are threatened.

21. Protection of Seacliffs. The best natural defense of seacliffs
against wave action is a fronting beach that is both high and wide.
Valuable areas of seacliff lacking natural protection can be
preserved by artificial means, which should be carefully engineered
to avoid beach erosion or shoaling. These protective measures
include (a) mechanical replacement of eroded beach material;
(b) construction of a bank of dunes between cliff and waveline
planted with native vegetation; and (c) construction of offshore
groins or breakwaters to reduce wave energy.

22. Runoff Erosion in the Coastal Zone. Erosion also results from storm
runoff, but poses a minor hazard under normal conditions. It be-
comes a major hazard only when man's activity alters the runoff
pattern and accelerates the erosional process, or when severe
natural erosion is disregarded.

23. Current Shoreline Protection Studies. The U. S. Army Corps of
Engineers and the California Department of Navigation and Ocean
Development operate a cooperative program to study shoreline
erosion. These studies are almost complete in Southern California
and are continuing in Northern areas. These research programs
only indicate broad erosion problems, however, and accurate
determination of erosion processes requires site-specific analysis
before construction proceeds.

24. Public Cost Burden. Development which interferes with natural
geologic processes may impose direct or indirect costs on the
public.

Policies

1. Geologic Safety Measures Necessary. Because many areas of the
California coastal zone exhibit various geologic instabilities-
earth-shaking, landsliding, tsunamis and shoreline erosion-and
because the possibilities of damage from geologic hazard along
many sections of the coast are great, measures to enure geologi-
cally safe land use within the coastal zone Are essential. The
local agency seismic safety elements now in preparation should
lead to definitive policies for application in land use programs.

2. Safety of Projects Should be Individually Checked. Since adequate
information about earthquake and other geologic hazards is incon-
sistently available for specific sites, the geologic data and
resulting engineering proposals for individual projects in the
coastal zone should be subject to review and approval to achieve
site stability and structural safety.

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LITTLE At 5

Statewide Geological Safety Measures Should be Uograded. In order
to achieve uniform compliance of local governments toward geologic
hazards, the Coastal Commission endorses the recommendations of
the Joint Committee on Seismic Safety, including its proposal to
establish a Geologic Hazards Review Board to deal with all geologic
risks. The Commission also encourages appropriate revisions of the
Uniform Building Code. Because of inadequate and sporadic appli-
cation of the Uniform Building Code in California's coastal zone,
enactment of the code needs to be strengthened by providing funds,
personnel, and training for vigorous enforcement. In addition,
the Uniform Building Code, 1970 Edition, should be upgraded rela-
tive to earthquake shaking forces.

4. Multi-Discipline Advisory Board Needed. Because consideration of
the several types of geologic hazard that exist in the coastal zone
encompasses a number of geologic and engineering disciplines, ade-
quate project review requires a statewide and six regional inter-
disciplinary advisory boards having expertise in geology, oceano-
graphy, soil engineering, engineering geology, structural engineering,
civil engineering and architecture, reflecting in large measure the
recommendations of the Joint Legislative Committee on Seismic Safety.
This group will review development proposals in the composite seismic
hazard area outlined on the attached map. Larger scale maps are
available in the Commission office. They will be revised based on
local agency's Seismic Safety elements.

Interim Development Guidelines for Geologic Hazard Areas. To reduce
potential damage from geologic hazards pending recommendations of an
interdisciplinary advisory board, no development should be allowed in:
a. Seismic hazard areas delineated on earthquake fault maps, soils
maps indicating materials prone to shaking or liquefaction, and
local and county seismic safety plans,
b. Landslide hazard areas delineated on slope-stability maps, and
local and county planning studies,
c. Ocean bluff and cliff areas, and
d. Areas specified in Composite Seismic Hazard Map (Figure A).
unless the proposed construction site has been analyzed by a survey
team including a design civil engineer, a soils engineer, and an
engineering geologist, all registered in the State of California;
and site treatment and building construction techniques adequate
to overcome the hazard have been approved by the team.

6. Interim Develovment Guidelines for Tsunami Runup Areas. To reduce
damage from seismic sea waves, no development should be allowed in
areas delineated in Figure A and in forthcoming U. S. Army Corps of
Engineers 100-year recurrence maps of tsunami runup, and other known
areas of tsunami risk, unless it is designed to withstand the force
of the waves and can sustain flooding. Under no circumstances
should hospitals, schools, emergency public services, or other
public buildings be constructed within these tsunami runup areas.

7. Interim Guidelines for Shoreline Protection and Channel Works. To
minimize beach erosion, developments such as revetments, breakwaters,
groins, harbor channels and other construction should not be allowed
unless the Army Corps of Engineers and the California Department of
Navigation and Ocean Development certify, on the basis of the best

information available, that the project will not impair the local
sand supply of an area or the longshore transport of sand within
littoral cells.
STABLE �
Interim CQastal Erosion Guidelines. TALE
A. Geology Stability
All developments within the immediate beach-
coastal bluff area of the Central Coast Region
must demonstrate geologic stability of the EA
structure for a 50-year period, must not con- * INOT KF-
tribute to instability of any cliff or beach, A�oEA 1QURING
and must be consistent with other policies of i>Eol-
the Coastal Zone Plan. T
The following definitions of coastal stability �!
shall apply to the Central Coastal Region: OCEAN
(See Figures I-M) -OCK
High stability areas A) less than 1 foot/year .. -:
historic cliff retreats
) inherently stable
cliff material, MODERNE
and () not dependent upon a
beach for its stability,
In high stability areas, any development pro-
posed within the area from the toe of the bluff AEA OF o
to a point on top of the bluff at a 1:1 (45�) 9E"n'nZ
slope from the toe must demonstrate stability as | X
defined above (with a geologic engineering rpt.)
Moderate stability areas i) less than I foot/year
historic cliff retreat, ./
() inherently unstable OCEAN� . G
cliff material, .. ..
and () may be dependent upon .4A�
a fronting beach for
stability. . - - ...
In moderate stability areas, any proposed devel- a
opment within the area of 2:1 (30 ) slope from � TMALEe
the toe to the top of the bluff must demonstrate
stability as defined above
Low stability areas A) greater than 1 foot/
year historic cliff
retreats o o
or () landslides or other
inherently unstable
material (such as beach I_
sand or active dunes).
In low stability areas, any proposed develop- 4 uff
ment must be excluded from the area of 1:1 (450) OCEAN ;K
slope from toe to top of bluff, and from the 43. 0
area of active movement, and stability must be ..,U e:
demonstrated for a 50 year economic life within .-u
the remaining area of 2:1 (30�) slope.

Areas currently considered to be stable, moderately stable, and
unstable are indicated on the accompanying maps. Designation of
these areas may change as additional technical information becomes
available. The geologic engineering report to be reviewed by the
Geologic Hazard Advisory Board should include:
an evaluation of the base erosion
the geometry of the cliff
the geologic conditions
the characteristics of the soil and rock materials
the various forces acting on the cliffs

B. Shoreline Protection
All development within the coastal erosion zone shall be planned
so as not to require future shoreline protection measures.
Since developments currently exist in unstable geologic areas
and areas of active coastal erosion, and individual instances of
cliff fall-off or beach loss must be anticipated, shoreline
protection measures must have a direct relationship to the protec-
tion of existing development and the hazard must be demonstrated.
Shoreline protection measures shall not contribute to instability
of any cliff, beach or coastal frontage.
Since shoreline protection devices have impacts beyond erosion
control, proposed seawalls and other devices will also require
particular conformance to policies on appearance and design,
access to beaches and the high tide line, and other pertinent
policies.

Available Geologic Information Should Be Fully Utilized. To reduce
loss of life and property damage from geological processes as quickly
as possible, the large amount of pertinent data on geologic hazards
being assembled by such agencies at the California Division of Mines
and Geology, the U. S. Geological Survey, the National Ocean Survey,
the U. S. Army Corps of Engineers, the Seismological Laboratory of
California Institute of Technology, tec., should be fully utilized
in all land use planning and development evaluations. The accelerated
accumulation of necessary geologic data should be encouraged.

10. Public Should Not Be Liable. In areas where geologic hazards recur
or are identified and development proceeds with knowledge of these
but without the appropriate precautions, there should be no presump-
tion of public liability for property loss (disaster loans, or forms
of insurance borne by the general public, etc.).

4AN MATEO COUNTY

RALF MvjOON BAY Q)

ICOAZ~AL ~fAP11Y
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STATE OF CALIFORNIA RONALD REAGAN, Governor

CALIFORNIA COASTAL ZONE CONSERVATION COMMISSION
CENTRAL COAST REGIONAL COMMISSION
701 OCEAN STREET, ROOM 300
SANTA CRUZ, CALIFORNIA 95060
PHONE: (408) 426-7390
April 8, 1974

Please find enclosed a copy of the summary report "Geology." We
especially direct your attention to the proposed findings and policies.
They are based on an extensive technical report which is available in our
office and at the libraries listed in the preface.

The Central Coast Regional Commission is committed to maximizing public
input into our planning process. To facilitate your contribution to this
effort, we have scheduled the following public discussion meetings:

Friday, April 19, 1974 Friday, April 26, 1974
Monterey Peninsula College Skyline College
Social Science 102 Building 2, Room 308
Monterey County San Mateo County
7:30 p.m. 7:30 p-m.

Monday, May 6, 1974
Board of Supervisors Chambers
Santa Cruz County
(Time to be announced)
(Formal Public Hearing)

Any person or organization can make a statement at these meetings.
Written comments received before May 1, 1974, will be incorporated into the
revised findings and policies for Commission action in May.

If you have any questions regarding this procedure or the report's
contents, please call Don Neuwirth, on our staff at (408) 426-7390- We are
sure you realize the importance of the coastal planning effort in complying
with the voter's mandate of Proposition 20, and appreciate your time and
effort in reviewing this document.

Thank you very much.

Sincerely,

Edward Y. Brown
Executive Director

EYB:pas

Enclosures