Draft Rockaway/Nedonna Beach foredune management study

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

DRAFT
ROCKAWAY/NEDONNA BEACH
FOREDUNE MANAGEMENT STUDY
FEBRUARY 1986

GB
454
.B3
D73
1986

COASTAL ZONE INFORMATION CENTER

Department of Land Conservation and Development

VICTOR ATIYEH
1175 COURT STREET N.E., SALEM, OREGON 97310-0590 PHONE (503) 378-4926

M E M 0 R A N D U M

February 20, 1986

U.S. DEPARTMENT OF COMMERCE NOAA

TO: Foredune Study Advisory Committee COASTAL SERVICE CENTER
Interested Persons 2234 SOUTH ROBSON AVENUE
CHARLESTON, SC 29405-2413
FROM: Bob Cortright
Dune Study Coordinator

SUBJECT: FINAL DRAFT FOREDUNE MANAGEMENT STUDY
DEADLINE FOR COMMENTS: MARCH 13, 1986
REVIEW MEETING: MARCH 13, 1986

Enclosed for your review and comment are copies of the almost final
products for the Rockaway Beach/Nedonna Beach Dunes Management Study. I
apologize that it has taken several months to revise earlier drafts of
the study and prepare a detailed grading plan. Funding and other
problems which we were unable to anticipate are responsible for the delay.

Several documents are enclosed for your review:
A Revised Technical Report -- The Technical Report has been vastly
reorganized and expanded from the original drafts you reviewed last
year. Information is now divided on an area by area basis.

The Nedonna Beach Grading Plan -- Wilbur Ternyik and FGA have drawn up a
detailed site specific grading plan for the Nedonna Beach area (from
Manhattan Beach Wayside to the South Jetty). The plan identifies
where grading can occur and where graded material may be placed. The
plan also recommends standards for placement of sand fencing,
fertilization and planting of beachgrass. The plan is intended to be
used to obtain County and state approva1s for qrading of the foredune

and implementation of other actions necessary to strengthen the
foredune. A rough drawing of the proposed grading plan map is also
enclosed. An existing conditions map will be provided with the final
document, but it is not ready at this time.

U.S. DEPARTMENT OF COMMERCE NOAA
COASTAL SERVICES CENTER
2234 SOUTH HOBSON AVENUE
CHARLESTON, SC 29405-2413

Property of CSC Library

-2-

A Revised Foredune Managemeht Plan -- Based on the Technical Report Wilbur
Ternyik and I have drafted detailed recommendations for the range of
human uses and activities which could affect stability of the
foredune. The Management Plan assesses the impacts of each major
type of alteration and provides specific management recommendations
to be implemented by the County and other units of government.

Tillamook County Beach and Dune Ordinance -- Deborah Brooker has drafted
amendments to Tillamook County's zonining ordinance to implement the
recommendations of the Grading Plan and the Management Plan.

Maps --The size of the Technical Report and Management Plan"maps
makes them to expensive to copy or reduce at this time. Copies of
the draft maps are available at the Department's office in-Salem and
through FGA in Portland.
A couple of no6s on the material. First, I appreciate the len'gth of the
material that we have sent out. I think you will find that the-imaterial
is well organized and fairly easy to read despite its length. 'If you
have limited time for review please focus your comments on the-grading
plan or areas of interest to you. Second, many of the illustrations
included with the documents are still'in draft form, so please@excuse any
inaccuracies. Also, please feel free to suggest changes to them.
Finally, if you have any questions orcannot prepare written comments-
please feel free to call.me or the other authors:

Bob Cortright DLCD 378-5453
Wilbur Ternyik Florence 997-2401
Roger Redfern Portland 233-2011
Deborah Brooker Tillamook 842-5511
Fred Glick Portland 242-1342

REVIEW MEETING

A review meeting is scheduled for March 13 in Salem at the DLCD offices.
(1175 Court Street NE) The meeting will begin at 1:30 p.m. .and run to
5:00 p.m.

BC:ps
7411D/5B

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TABLE OF CONTENTS

pagt

INTRODUCTION I
PROJECT AREA I
INVESTIGATION 3

COASTAL PROCESSES AND FEATURES 3
OFFSHORE PROCESSES 8
SAND SU PPLY 16
BEACH PROCESSES 20
FOREDUNE PROCESSES 26
FLOODING 32
SHORELINE EROSION AND ACCRETION 35
WIND EROSION AND DEPOSITION 37
CREEK OUTLET PROCESSES AND FEATURES 38
JETTIES 40

FOREDUNE MANAGEMENT UNIT DESCRIPTIONS AND
RECOMMENDATIONS 43
NEDONNA BEACH 44
-General 44
Vfgttation 46
Flooding--- 48
Erosion 49
Accre. tion 49
Present and Future Foredune Stability 50
--- ------ --------
LAKE, LYTLE OCEANFRONT MANAGEM-ENT UNIT 54
General 54
Y@gtt!@tion 55
Floodi g 56
Erosion 56
Accretion 57
Present and Future Foredune Stability 57
------ --- ------ -------- ---------
ROCKAWAY BEACH MANAGEMENT UNIT 58
General 58
Y@gttgtion 59
Flooding 60
Erosion 60
Accretion 61
Present and Future Foredune Stability 62
- --- ------ -----
ROCKAWAY SOUTH/TWIN ROCKS MANAGEMENT UNIT 63
General 63
Y@,gtj#tion 63
Flooding 64
Erosion 64
Accretion 65
Present and Future Foredune Stability 66

EASE

CREEK OUTLETS - DESCRIPTIONS AND RECOMMENDATIONS 67
CRESCENT LAKE OUTLET 67
General 67
ytgetation 68
f!229-i!!9 68
Erosion 69
Accretion 69
Present and Future Foredune and Shoreline Stability 70
ROCK CREEK 71
General 71
Yggetation 71
Flooding 72
Erosion 72
Accretion 73
Present and Future Foredune and Shoreline Stability 73
SALTAIR CREEK 74
General 74
ytgttation 74
Flooding 75
Erosion 76
Accretion 76
Present and Future Foredune and Shoreline Stability 77
SPRING LAKE OUTLET/WATSECO CREEK 78
General 78
ytgt1ation 79
Flooding 79
Erosion so
7
Accretion 81
Present and Future Foredune and Shoreline Stability 82

PHASE 2 DRAFT
TECHNICAL REPORT ON THE FOREDUNE MANAGEMENT STUDY
FOR-THE ROCKAWAY/NEDONNA BEACH AREA,
TILLAMOOK COUNTY, OREGON

INTRODUCTION

PROJECT AREA

This Investigation focuses on the Nedonna Beach,

Rockaway and Twin Rocks shoreline in northwest Tillamook

County (see Figure For the purpose of dune management

the study area extends from the south jetty at Nehalem Bay on

the north to the outlet of Spring Lake and Watseco Creek on

the south. To assure adequate consideration of shoreline

-processes portions of the technical investigation Included

the area from Cape Meares headland on the south to Neahkahnie

headland on the north. However, the focus of the technical

report is the area bounded on the north by the south jetty at

Nehalem Bay and on the south by the north jetty at Tillamook

Bay. The study area includes the beach on the west and the

lee slope of the foredune on the east.

The study area is approximately halfway between two

basalt headlands, Neahkahnie Mountain and Cape Meares.

The 17 miles of beach between the headlands is composed

mostly of medium sand. Boulder to pebble gravel and

coarse sand occur on the beach near the headlands. Between

the headlands the shoreline Is generally concave, and the

only major Interruptions are the Jetties at Nehalem Bay

-------------------------

A glossary of terms Is provided in Appendix 1.

Page 1

NEHALEM
BAY

BRIGHTON

@NANHATAN BEACH

*ROCKAWAY

#BARVIEW
GARIBALDI f COL

<
Lij
TiL LAMOOK 0
BAY TILLAMOOK SAY
PORTLAND

"CEANSIDE TILLAMOOK

NETARTS

NAO UINA SAY

NETARTS
SAY.

COOS BAY

COQUILLE R-

RIVER

OREGON
CALIFORNIA

Figure 1. Location Map.

and Tillamook Bay. The only other Interruptions to the

shoreline are several stream outlets. Except for local zones

of erosion the beach Is broad and gently sloping. The

majority of-this shoreline Is bordered by a foredune adjacent

to the beach.

Sand spits occur at Nehales and Tillamook Bays. Nehales

spit extends southerly from the mainland at Manzanita

and the Tillamook Spit (also known as Bayocean Peninsula and

Kincheloe Point) extends northerly from the mainland at Cape

Meares. Tillamook Spit was breached near its south end In

1952, and on the spit the Bayacean Resort development was

subject to severe erosion beginning about 1920 to 1925

(Dicken, 1961). The resort was eventually abandoned. The

breach In the spit was closed by a dike in 1955-1956.

This study is divided into two parts, a technical

Investigation and report and a management plan. The overall

objective is the preparation of a management plan for the

Rockaway/Nedonna Beach area which maintains and enhances

natural flood and erosion control functions of foredunes and

where appropriate allows gradingfor maintenance of views

from ocean front dwellings. It is the purpose of this

technical report to review, document and analyze the relevant

past, present and potential future physic-al conditions and

processes in the study area that would affect foredune

modification.

Page 2

INVESTIGATION

The investigation Included a literature review,

discussions with knowledgeable Individuals, Interpretation of

aerial photography, field investigation and mapping, and

analysis of the information collected. Important references

and personal communications are cited in this report and

listed at the end of the report. Aerial photography used in

the investigation is listed In Table 1. The upper edge of

t-he beach was plotted on the aerial photos and reproduced on

the Technical Report Map. Field Investigation results are

provided on the Technical Report Map and In the text of the

Technical Report.

COASTAL PROCESSES AND FEATURES

In order to set the stage for the foredune management

the nature of the hazardous conditions at Rockaway and

Nedonna Beach must be recognized. There also must be

recognition that without sound foredune management the

risk of severe damage from ocean storms is greatly increased.

Man has long had a love affair with the sea and its

beauty. However, there are Inherent dangers. This is very

apparent with most of the beach front homes and commercial

buildings in the Nedonna Beach/Rockaway study area. With few

exceptions, all of these structures were-built on or near

an unstable foredune system. (Foredunes subject to

continuing wave overtopping, ocean flooding, sand erosion,

and sand deposition.) One only needs to look at the past

historical erosion events to realize the seriousness of this

Page 3

Table A: Aerial Photos Used in the Rockaway/Nedonna Beach,Dune Management
Study

Date Photo Numbers Typel Scale Source2

4-28-39 39-1555 to 1567 B &W 1:10,200 Corps

8-20-64 64-2198 to 2203 B&W 1:10,000 Corps

8-17-66 66-2220 to 2223 B &W 1:30,000 Corps

5-17-69 TGI 1-16 to 18 B &W 1:45,000 ODOT

6-24-70 JIB 11-1-3 to 1-12 B&w 1:24,000 ODOT

7-25-73 OC-17-15-6 to 15-14 C 1:12,000 ODOT

7-25-73 OC-17--16-1 to 16-5 C 1:12,000 ODOT

12-26-77 77-2363 to 2368 B N 1:24,000 Corps

1B&W Black and White;
C - Color.
2corps U. S. Army Corps of Engineers;
ODOT Oregon Department of Transportation

problem.

On December 2 and 3. 1967:

"In Tillamook County, logs were washed a block behind
the oceanfront road at Manzanita. Nehalem faced Its
worst flooding since 1933 with nearly every business
building in the the main block being flooded. Waves
carried logs over the sand dune and blo.cked the parking
lot at the-north end of Nedonna Beach, and damaged homes
at Manhattan Beach. At Rockaway, the surge sent logs
over the railroad tracks and onto U.S. Highway 201,
damaging several houses, plugging the creek outlet and
causing local flooding. Logs damaged houses at Twin
Rocks and were carried across the railroad tracks to the
highway there. At Bar View In Garibaldi, logs washed
Into Highway 101. Flooding occurred near the Miami
River and some highway flooding occurred near Tillamook.
Logs were washed nearly two blocks back from the beach
at Cape Meares, and logs damaged homes, seawalls, and
riprap at Netarts. Picnic tables were washed away at
the county park at Sandlake, and logs were strewn across
the highway at Tierra Del Mar. Although many houses and
buildings In Pacific City and woods were surrounded by
water, no damage was reported. At Camp Winema, logs.
were washed high above the beach, but no damage was done
to the buildings; and at Neskowin, logs damaged
beachfront houses."

I
.'.Historically, one of the greatest ocean floodings in
Till.amook and Clatsop Counties occurred on January 3.
1939, when high tides and windswept waters caused
extensive damage over such of coastal Oregon. The
sandspits at Bayocean and Neskowin Ridge were breached
in several places, and surf-swept logs damaged dozens of
beachfront houses at Twin Rocks, Manhattan Beach, Tierra
del Mar. and other communities. South of Barview, 300
feet of Southern Pacific Railway track were carried
Inland over Highway 101. Waves splashed completely over
Twin Rocks, one-half mile offshore from the community of
Cape Meares. In calm weather, Twin Rocks and Pyramid
Rock stand 80 to 100 feet, respectively. above mean sea
level." (Schlicker and others, 1972, page 103)

Past storm events, such as those of 1967 and 1939,

Indicate the probability of future storm-induced erosion and

flooding.

Given the inevitability of future ocean flooding, it Is

imperative that appropriate measures be taken as soon as

Page 4

possible to strengthen natural storm wave defense systems in

developed areas. In numerous other parts of the world, there

is a clear recognition of the protective nature of foredune

areas as a buffer zone against attack by the sea. The

U. S. Army Corps of Engineers reports:

11while the sloping beach and beach berm are the outer
line of defense to absorb most of the wave energy, dunes
are the last zone of defense In absorbing the energy of
storm waves that overtop the berm. Although dunes erode
during severe storms, they are often substantial enough
to afford.complete protection to the land behind them.
Even when breached by waves of a severe storm. dunes may
gradually rebuild naturally to provide protection during
future storms. Continuing encroachment on the sea with
manmade development has often taken place without proper
regard for the protection provided by dunes. Large dune
areas have been leveled to make way for real estate
developments, or have been lowered to permit easy access
to the beach. Where there Is inadequate dune or similar
protection against storm waves, the storm waters may
wash over low lying land, moving or destroying
everything in their path.

"Gently sloping shores, whether beaches or wetlands, are
natural defenses against erosion. The slopes of the
foredune form a first line of defense, dissipating the
energy of breaking waves. The berm prevents normal high
water from reaching the backshore. Dunes and their
vegetation offer protection against storm-driven high
water and also provide a reservoir of sand for
rebuilding the beach. Wise management of shore areas
should include protection of these natural defenses
where they exist.

"Although erosion is essentially caused by natural
shoreline processes, its rate of seveity can be
intensifed by human activity. The shoreline and the
water are highly valued for recreational activities, but
heavy use and development may accelerate erosion. -Those
who build 'permanent' homes and recreation facilities
often Ignore the fact that the shoreline is being
constantly built up and worn away again. They may also
fall to take into account the periodic and unpredictable
effects of storms." (U.S. Army Corps of Engineers.
1975)

In Europe, where some dune areas have been intensively

managed for years, foredunes, referred to as barrier dunes.

Page 5

are given prime consideration' because of their protective

nature.

"On sandy coasts, the ridges of sand dunes are often the
natural protective structures against flooding the low-
lying land, the villages or towns during storm tides.
The strength and resistance of these barrier dunes,
which are-found just landward of the'beach, Is to be
estimated in consideration of the extent and the height
of the dunes as well as of the width, the height and the
stability of the beach. As in many cases on the beach
in consequence of altering sea and wave conditions and
different littoral drift, the supposition for erosion or
aggradation varies, dunes and beaches have to be
observed constantly. The beginning of a considerable
erosion of the dunes has to be seen In connection with
the development of the beach. A systematic research of
the reasons and the further development has to be done.
The research has to Include the total dune-beach-
profile." (Erchinger, Heie. Protection of Sandy Coasts
in 1974. Dependence of the Dune-Beach-Type)

In West Germany annual erosion of foredune foreslopes.is

repaired each season. Erchinger also speaks to repair of

eroded foreslope In the Netherlands on the Isle of Tuxel by

use of bulldozers followed by replanting of stabilizing

vegetation.

Grading the foredune for ocean viewing was the impetus

to cause this study to take place, but the ultimate benefit

will be strengthening the protective nature of the foredune

through Informed management.

Two concepts that are critical to foredune management

emerge from the national and International literature:

1. Sand In the nearshore, beach and foredune is part of

a dynamic, constantly changing system. Whether in the

offshore bar, nearshore slope, beach, beach berm, or

foredune, the sand is critical to the stability of the

Page 6

shoreline.

2. Typically the foredune is above the level of high tides

and most waves. The foredune is composed of sand in

storage; sand that is available to protect inland areas

from severe storm surges and storm waves.

Maintenance and enhancement of the for6dune and natural

beach-dune processes is critical because of the protective

function of this system against ocean flooding. If the

foredune is damaged or the natural system disrupted the

potential for flood damage to.beach front development is

Increased. The beach and foredune respond to ocean flooding

In a predictible way:

"The natural beach exists In a state of dynamic tension,
continually shifting in response to waves, winds, and
tide and continually adjusting back to equilibrium.
Long-term stability is gained.by holding the slope or
profile Intact through balancing the sand reserves held
.in various storage elements - dune, berm, offshore bar,
and so forth. Each component of the beach profile is
capable of receiving, storing, and giving sand,
depending on which of several constantly changing forces
Is dominant at the moment. Stability Is fostered by
Maintaining the storage capacity of each of the
components at the highest level.

"When storm waves carve away a beach, they are taking
sand out of storage. In the optimum natural state there
is enough sand storage capacity in the berm or dune to
replace the sand lost from the beach to storms.
Consequently, the effects are usually temporary, with
the dune or berm gradually building up again." (Clark,
1977.pp. 320-323)

Clark also explains the role of dunes in this protective

function:

"As the dune Is attacked by storm waves, erod-ed material
Is carried out and deposited offshore, where it alters
the underwater configuration of the beach. Accumulating
sand decreases the offshore beach slope (makes it more
nearly horizontal), thereby presenting a broader bottom

Page 7

surface to storm wave action. This surface absorbs or
dissipates through friction an Increasingly large amount
of destructive wave energy that would otherwise be
focused on the shoreline behind the barrier.

"The capacity of the dune for absorbing and moderating
wave energy is not dependent on any ability to
completely prevent breaching or flooding. Even in the
process of being inundated and destroyed, as many are by
hurricanes-, the dune moderates back beach storm damage.
This effect is less pronounced for low dunes,. but
nevertheless persists. Since storm resistance increases
with dune height, however, all human uses of the barrier
that devegetate, erode, or lower the dune expose the
shoreline behind the barrier to Increased storm damage."
(Clark, 1977, 67)

The effectiveness of unaltered dunes in providing

protection from flooding Is a principal reason for the

prohibition on building on undeveloped foredunes subject to

--ocean flooding or erosion. Although foredunes in the study

area have been altered their flood protection capability has

not been completely compromised. Several areas have eroded

or are eroding without imminent threat of damage to existing

homes. Nonetheless it is likely that some areas will

experience erosion that, if unchecked, will damage or destroy

structures. (North Nedonna Beach experienced this kind of

heavy erosion in 1970-71 and 1978-79.)

This section summarizes regional information relevant to

the study area. It is the purpose of this section to provide

the basis for the understanding site-specific Information

presented In the following sections.

OFFSHORE PROCESSES

The offshore processes, features and hazards that are

relevant to this area and study are tides and waves. offshore

bars, and nearshore current.

Page 8

Tides are an important shoreline altering process when

combined with storm surges, large waves, and rip-current

emb.ayments. Episodes of beach and foredune erosion occur in

periods of high tide particularly when combined with storm

surges and large waves. Figure illustrates the range of

tidal elevations on the Oregon Coast. The lowest estimated

tide that can occur is 3.5 feet below mean lower low water

(about 7.6 feet below mean sea level). The highest tide

predicted by tide tables is 10.3 feet above mean lower low

water (about 6.2 feet above mean sea level). The highest

tide projected to occur, the sum of the highest predicted

--tide and the highest recorded storm surge. is 14.5 feet above

mean lower low water (about 10.4 feet above mean sea level).

Waves provide the energy for.beach and nearshore sand

movement and for erosion of t-he beach and foredune. Waves
are gene-rated by winds and reflect seasonal variations in

weather patterns.

The nearest published wind rose diagram is for
Tillamook. Figure S shows wind roses for the typical winter

and summer months of January and July.. In January, the major

wind directions are from the south and southeast. but there

are also significant winds from the east. In July, the

majority of winds are from the northwest, but there are also

notable winds from the north and west.

In general, waves approach the Oregon Coast from the

southwest in the winter and from the northwest In the summer.

Wave period and breaker height vary seasonally; In both cases

Page 9

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SALEM

Newport I') LEGEND
Yaquona S@ALE' (I'N PERCENT OF TIMEJ
Bay I I f
19 1 0 25 50 75

THE LENGTH OF THE WIND ROSE SPEEO-.I.EITIO. BARI.
MEASURED By THE SCALE. INDICATES THE PERCENT Or
TIME WIND WAS FROM THE DIRECTION AND IN THE SPEED
CLASS REPRESENTED. AN EXCEPTION IS SPEEDS OF 3 MILES
PER HOUR OR LESS PERCENT OF SPEEDS IN THIS RANGE IS
SHOWN ELOW THE CIRCLE OF THE WIND ROSE. VARIOUS
EUGENE SOURCES" OF DATA MADE IT NECESSARY TO ASSIGN
SLIGHTLY DIFFERENT SPEED 0 A SES TO THE WIND ROSES.
THE FIGURE IN PARENTHESIS FOLLOWING THE STATION
NAME IS AN INDEX TO THE SPEED CLASS FOR THAT STATION
Reedspo-rl AND IS DEFINED BELOW

INDEX NUMBERS AND SPEED CLASSES(MPH)
SPEED
SYMBOL INDEX CLASS (MPH1 INDEX CLA SS (NIPW
Coos Say, 41) 4-15 (2) 4-12
11) 16-31 (2) 13-31
>Y@ North Bend (11 11) 32-47 (2) 32-46
17 Roseburg - 0) 48. (21 47-
5 FOR THIS CLASS ALL STATIONS HAVE
THE SAME RANGE OFO-3 MPH

JANUARY READINGS
A--, Bandon 0 JULY READINGS

MEDFORD

Brookings-(ti

52 18
Figure January and July wind roses for selected sites. This plate was provided
by the Portland District, U.S. Army Corps of engineers.

they are higher In the winter and lower In the summer.

Wind speed, wind duration and the extent of ocean

exposed to the wind Influence wave height and frequency. The

wind direction influences wave direction. Waves can be

generated by both local and distant storms. Wave conditions

have been studied by O'Brien (1951) on the Columbia River

lightship and studied on offshore oil drilling rigs by Rogers

(1966) and by Watts and Faulkner (1968). Offshore wave

heights of up to 58 feet were reported and one exceptional

wave was reported as 95 feet high. According to Komar and

-others (1976b): "The measurements of both Rogers (1966) and

..Watts and Faulkner (1968) do not represent average wave

conditions during the severe storms, but exceptional waves

produced by the chance constructive summation of several

large waves." On the shorellne, the constructive summation

of two or more waves can produce what is called a freak wave

or sneaker.

In 1971, a seismic recording system was installed at the

Marine Science Center at Newport. Komar and others (1976b)

present a summary description of the system and It.9

limitations and provide an analysis of recorded measurements
from November 1971 through.June 1975. Figure Z/ Illustrates

significant wave breaker heights from July 1972 through June

1973. This figure includes large storm waves produced In

December 1972 that resulted In significant erosion on the

shoreline. The maximum wave breaker height measured was 7

Page 10

12 WAVE PERIOD

10
Ir
9

JULY AUG SEPT OCT NOV OEC JAN FEB MAR APR MAY JUNE

7
BREAKER HEIGHTS

Is I

It%
M 3 %%1,

011
%%%

JAN
0 JULY AUG SEPT 19i72 OCT __N@TVDEC FEB. MAR 1973 APR MAY JUNE

Figure @6. Significant wave breaker heights and periods
measured at Newport during July 1972 through June 1973. Each
datum point gives the average for one-third month. The dashed
lines give the maximum and minimum breaker heights during those
one-third month intervals. Note the arrival of large storm waves
during the last part of December 1972. (From Komar, 1979).
,WAVE PERIOD

meters (23 feet). Average height of the larger breaking

waves was estimated by Komar (1979) as ab out 15 feet. He

also noted that heights of 23 feet are truly exceptional and

that similarly high breakers were recorded in December 1972,

October 1977 and February 1978 which were periods of severe

shoreline erosion. Similar extreme wave heights were

recorded more frequently for storms during the 1981 to 1984

El Nino episode. The evidence gives support to the somewhat

obvious observation that large waves, especially on high

tides, are largely responsible for shoreline erosion.

Another reasonable conclusion is that moderate-sized

breakers, days or weeks before a series of large breakers,

can set up conditions for severe erosion. (Note the November

breaker heights on Figure The first storm removes sand

from the beach and enlarges rip-current embayments. allowing

subsequent high tides and large breakers to come closer to

the backshore and foredune before breaking and losing energy.

The seasonal variation in wave conditions produces
changes in the nearshore zone and beach (Figure -5@). High

and frequent waves In winter months erode sand from the beach

and deposit the sand In offshore bars. In the summer months,

the sand In the offshore bars is moved back on to the beach.

Because this sand movement is controlled.by wave conditions,

this cycle is not strictly seasonal. Low waves during the

winter will move sand onshore.

Littoral currents are caused by waves that generally

approach the Rockaway/Nedonna shoreline from the northwest in

Page 11

swell (summer) profile
storm profile shoreline Sea
swell profile shoreline
berm Cliff
mean water level

bar
trough
bar
storm (winter) profile

Figure Schematic illustration of the beach profiles produced by
storms versus gentle swell waves. On the Oregon coast these profile
changes are approximately seasonal due to our storms occurring principally
during the winter months. (From Komar, 1979).
trou@h 'or
or
Lb storn

the summer months and from the southwest In the winter

months. Waves push sand up the beach and the retreating water

takes sand off the beach. The result Is net movement of sand

to the south in summer and to the north In winter. Aerial

photos, field evidence, and previous studies (Komar and

others, 1976a and Lizarraga-Arciniega and Komar, 1975)

indicate that this shoreline has both north and south

littoral transport but that the long-term sum of the

transport (net drift) Is zero or near zero.

Field evidence also indicates that there has been an

apparent short-term net northerly drift in the recent past

(at least in 1983,and 1984). The primary evidence of this is

shoreline erosion north of Cape Meares, north of the

Tillamook North Jetty, and north of the Nehalem North Jetty.

This evidence is not conclusive, but Increased sand on the

beach at.Neahkahnie, north of the study area, strongly

supports a short-term net northerly drift. Recent

reha bilitation of the Nehalem jetties and recent extension of

the south Jetty at Tillamook Bay could explain some of the

recent erosion but does not explain the accretion at

Neahkahnie.

Rehabilitation of the Nehalem jetties has c.aused

accretion adjacent to the jetties. Typically, the sand

supply loss related to jetties Is made up by nearby shoreline

erosion (Komar and others, 1976a). The accretion at Nehalem

Jetty has not caused any notable backshore or foredune

erosion in the study area, but comparison of 1978 and 1984

Page 12

aerial photos does indicate a reduction In beach width south

of the accretion area near Crescent Lake Outlet.

At Tillamook Bay, the extension of the south jetty was

followed by adjacent accretion. There has also been

substantial erosion north of the north jetty and moderate

erosion south of the accretion area. The erosion north of

the jetty could be related to blockage of northerly sand

movement around the newly extended south jetty In the winter.

However, some experts, including Komar (personal

communication) believe that there Is very little or no sand

transport around jetties.

We concur with Komar's theory that there is a net

northerly littoral drift associated with El Nino caused

changes in the number of large waves from the southw est. He

is investigating the.impacts of the recent El Nino. Komar

argues that accretion at the south jetties of Tillamook and

Nehalew Bays and at Neahkahnie (observed by the study team)

is evidence of net northerly drift caused by El Nino. He

also believes that since their construction the Tillamook and

Nehalem jetties and outflow from the bays has blocked

longshore transport, and the extension of the south jetty did

not cause t,he erosion to the north.

Rip currents do develop along the shoreline of the study

area and the embayments (cusps) that form are often related
to local shoreline erosion (Figure 6 ). Rip current channels

and embayments were observed on aerial photos and in field

investigations. The locations were transferred to the

Page 13

OCEAN

breoking woves

beach.edge

dune edge

11 El 13 D 1:1 13
I I I
SPIT endongered
homes

Figure A rip current flowing outward
across the beach hollowing out an embayment
into the beach and eventually into the foredunes
causing property losses. (From Komar, 1979).
CEA @N
be _ne
Ok.

be'Ch ed 9e

du ne 'dge

Technical Report Map to determine any patterns of rip current

reoccurrence. This evidence indicates that in some locations

rip currents can be somewhat stationary. Typically, rip

currents would be stationary adjacent to stationary shoreline

features such as jetties and the deltas at the mouths of

creeks. In other areas, the rip currents do not follow an

identifiable pattern.

Previous to the rehabilitation of the Nehalem jetties,

rip current embayments were common along the northern portion

of the Nedonna Beach area. In 1977 and 1978, two embayments

reduced the width of the beach and thereby contributed to

foredune erosion that threatened several homes located on the

backslope of the foredune. Emergency riprap was placed to

protect the homes (see Tecnical Report Map). Slightly north

of Rock Creek, a rip-current embayment appears to have

contributed to recent foredune erosion that was still evident

in 1985 as a large erosion escarpment. In the mid-196019, an

embayment slightly north of Saltair Creek appears to have

contributed to shoreline erosion that extended almost to the

1939 shoreline. Slightly north of Spring Lake Outlet an

embayment possibly contributed to foredune erosion in the

winter of 1982-83. Other specific erosion episodes could

probably be related to rip-current embaywents but the aerial

photo coverage of the study area Is only available for a

limited number of years (Table 1).

A tsunami is a wave or set of waves produced by a

submarine earthquake or volcanic eruption. The term "tidal

Page 14

wave" is sometimes Inappropriately used in reference to

tsunami. In recent history, the most common source of

tsunami waves on the Oregon Coast Is the Alaska area. The

most recent tsunami events affecting the Oregon Coast

occurred in 1964 and 1968 (Schatz and others, 1974 and Wilson
and Torum, 1968). Figure -7 illustrates maximum wave heights

at several locations on the Oregon Coast including Nehalem

and Tillamook Bays for the 1964 tsunami. The largest wave at

Nehales Bay was about 12 feet in height. The low wave

heights at the Tillamook River are Indicative of the loss of

wave energy as the tsunami passed through the broad and

shallow bay.

There is solid evidence of a slow, world-wide rise in

sea level. A change in sea level could have substantial

consequence on shoreline erosion and the long-term safety of

the study area. Evidence accumulated by Hicks (1972)

suggests that there was a rise In sea level of about 1.5 mm

(0.06 inch) per year in the 34 years of records analyzed.

However, these records indicate that the Oregon Coast may be

rising at about the same rate as the rise in sea level

(Figure Records at Astoria, Crescent City in California

and Friday Harbor In Washington show no apparent sea-level

changes (Hicks, 1972). Alaska is rising faster than the rise

in sea level.

There Is presently a controversy regarding an Increase

In the rate of world-wide sea level rise. Hicks (1978) has

updated his previous data, but he only reports on the average

Page 15

CAPE FLATTER 1240W 12120W 1200 At
V I C @!R ItA& FRIDAY HARBOR 2.3t R I
NEAN BA 4 7t R LEGEND
APPROX. LOCATION TIME
LAPUSH 5.3 1 R I OF TSUNAMI WAVE FRONT
% % VERETT APPROX. LOCATION & TIME 48ON
MOH R I OF CREST Of SPRING TIDE
SEATTLE 0.8 1, F) 2.3(R) FIGURES A)tE HEIGHTS (in fl)
BREMERTON OF MAXIMUM TSUNAMI WAVE
TAHOLAH 2 4 111 1 BASED ON RISE 1, It ) OR
WRECK CRrEK - 14 9(Ft FALL( F) ABOVE TIDE LEVEL
DATA FROM SPAETH AND
0 BERKMAN. 1967 -. SCHATZ.
OCEAN S-ORE5 -19'11R I of ai, 1964. MOGAN, at at, 1964
RAYS HARBOR WHIPPLE it LUNDY. 1964*.
U S. COAST GUARD

WILLAPA SAY
% r-r-r-_TIDE CREST
SEAVIEW-12-5JR I I WASHINGTON
0 0 0
ILWACO - 4@5 ( R I C
I 1 1) - .110
CAPE DISAPPOINTMENT C
OLUMBIA
5 7 RIVER WAVE HEIGHT ABOVE MEAN HIGH WATER
FEET
TSUNAMI
AST OR IA- 2 4 1 R) FRONT 10 46ON
T
R 0
TILLAMOOK %SAY to
I.- ITILLAMOOK TILLAMOOK R. 0
10
r
0 DEPOE DAY 0

10
NEWPORT
A DAY
0of TOLEDO YAOUIN
ALSEA SAY CORVALLIS
10
SIUSLAW R r 0
EUGENE
10
UMPOUA R. 440N
WINCHESTER SAY 0

-COOS SAY L 0

10
BANDON COQUILLE R. f I a IS 0
A !
CAPE to
BLANCO CHETCO R.
07 Do 09 10 it 12 13
TIME IN HOURS G-M-T. MARCH 26. 1964

OREGON

It 42ON
. I
RESCENT CITY
19.T ( R CALI
FORNIA

Figure,6. Maximum heights of tsunami waves recorded at tide
stations or by observations along the Washington-Oregon coast (from
Wilson and Torum, 1968).

time (years)

0 10 20 30 40 50
+20

S East Coast

0
Oregon Coast

-20 -

Alaska

-40

Figure Schematic of water level
changes on the Oregon coast as compared to
the East coast and the coast of Alaska, based
on the data of Hicks (1972). (From Komar,
1977).
East Coast

Orego'

0
_@Al skc

rise. Gornitz and others (1982) proposes that there is an

increase in the rate of sea level rise related to the

Greenhouse Effect. Barnett (1984) disagrees with Gornitz.

This controversy promises to continue. If the rate of sea

level rise is increasing and continues then Oregon's

shoreline will be affected at some time in the future.

Because the sea level rise will be initially very slow and

very small, there will be sufficient time to re-evaluate

foredune grading practices and to react to the growing threat

to low-lying coastal areas.

SAND SUPPLY

Information on nearshore bathymetry (water depth) of the

study area is limited to a navigation,chart produced by the

U.S. Department of Commerce, National Oceanic and Atmospheric

Administration, National Ocean Survey (1982). The chart,

reproduced In part in Figure shows water depths at the

time of sounding at the Nehalem Bay outlet in 1982, South of

the Nehalem bar area, the depths are from 1956 surveys.

Because the Information illustrates the depths at only the

time of the soundings, it is not possible to determine

seasonal changes of the offshore bottom or the changes over a

number of years.

The chart does Indicate the occurrence of sand bars at

the time of the soundings. At the mouth of the Nehalem, the

bar extends about 2,100 feet beyond the jetties and appears

to Influence the offshore area for about one mile north and

south. The shallow depths at the Nehalem bar (1 to 8 feet)

Page 16

indicate that some sand may have been able to bypass the

Jetties and the mouth before the rehabilitation of the

jetties. Increased scouring of the bar after jetty

rehabiliation has probably eliminated sand bypass.

South of the bar at the mouth of the Nehalem Bay. the

chart depicts sand bars as far south as the area offshore

from Lake Lytle. From there on south, there are no sand bars

sapped. It is not known whether the sand bars were not

present or had moved inland beyond the survey area. The

latter is more likely.

Factors of the littoral sediment budget are illustrated

in TableA. Littoral transport into the area is apparently

blocked by Cape Meares headland on the south and by

Neahkahnie headland on the north. Cape Meares is a headland

with a precipitous shoreline that extends over 200 feet west

of the sandy shoreline. The offshore depth Is shown as

rapidly dropping off to 18 feet on the U.S. Geologic Survey

topographic map. Neahkahnie headland has a precipitous

shoreline that extends over 5000 feet west of the sandy

shoreline. The jetties and channels at Tillamook and Nehalem

Bays apparently also block littoral drift. This creates a

pocket beach with a fixed sand budget. River and stream

transport from upland areas appears to be negligible or very

small (Kulm and Byrne, 1966). The streams do return wind-

transported sand to the beach and nearshore system. Some new

sand does come from the Astoria Formation sandstone on the

north side of Cape Meares headland but does not contribute

Page 17

Table,-f. The Budget of Littoral Sediments (Adapted from Komar, 1979)

Credit Debit Balance

Longshore Transport Longshore Transport Beach Deposition or

into Area Out of Area Erosion

River Transport Wind Transport Out

Shoreline Erosion Offshore Transport

Onshore Transport Deposition in Submarine

Canyons

Hydrogeneous Transport Solution and Abrasion

Wind Transport onto Mining

Beach

Beach Nourishment

24 -

sand to the study area because of the apparent blockage at

the Tillamook Bay Jetties. Onshore transport might occur

seasonally.

The amount of sand lost to offshore transport is not

known. Wind does transport some of the sand Inland to the

foredune. As the foredune continues to receive sand deposits

from the beach, there is a net temporary loss to the system.

There Is ocean wave erosion on the frontal area of the

f'oredune, but there is slow accretion. The amount lost to

solution and abrasion is not known, but it is probably very

small. The amount of sand removed in the past by mining Is

not known at this time, but it Is probably negligible.

The apparent stability of the central Rockaway shoreline

over the last 46 or more years indicates that there are no

large supply increases or losses. Our conclusion is that the

shoreline segment between the Tillamook and Nehalem Jetties

has had a roughly steady sand budget. There are no known

sources of new sand. A small amount of sand may be added to

the system by streams that do not flow through the lakes,

Watseco Creek and Rock Creek. There may be a net loss or

gain from onshore or offshore transportation, but further

detailed study of the offshore bar and sand supply over tine

Is needed to determine the dynamics of bar movement and the

volume of sand in relation to the rest of the shoreline

system.

Inland sand losses are more apparent. Accretion after

the construction of the Jetties removed a substantial volume

Page 18

of sand from the system. Slow accretion and foredune growth,

since at least 1939. has removed a such smaller amount of

sand from the active sand budget.

From the discussion It is evident that much more

information is needed on the sand budget in the study area.

The necessary information must be obtained through research

that is beyond the scope of this investigation. More

research Is needed on all aspects of the littoral sediment

budget. Even a qualitative evaluation on this shoreline is

limited by a lack of Information on the shoreline and

nearshore previous to the placement of Jetties at Tillamook

Bay and the Nehalem River.

The following is presented as a summary of the best

available information as applied to and In evidence In the

study area:

1. The condition of the study area shoreline before

construction of the Jetties at Tillamook and Nehalem

Bays is not known. It can be assumed that there was a

broad bay mouth at the approximate location of the

Jetties. It is also assumed that there was a broad

beach on the Rockaway shoreline that was backed on the

east side by a well vegetated barrier dune ridge, the

remnants of which are still present..

2. When the south jetty was constructed at Nehalem Bay in

1915 and the north jetty was constructed at Tillamook

Bay in 1912 there was accretion in the low-lying

embayments adjacent to the Jetties. The source of the

Page 19

sand needed to'rill thes.e embayments is not known. -It
must be assumed that the sand came from the shoreline

between the two bays (i.e. central Rockaway Beach)

and/or from the offshore bar.

3. After the accretion associated with the Jetty

construction the study area established 'a newt

equilibrium condition that, was subsequenttly disturbed by

the rapid deterioration of the Nehalem jetties.

4. The introduction of European beach grass in the 1930's

modified the shoreline character, but it did not

significantly alter the shoreline equilibrium. The

beach grass created a foredune ridge where previously

there had been a broad backshore area.

5. Since the introduction- of European beach grass there has

been.slow episodic accretion in all of the foredune

management units, but there has not been a consistent

pattern of accretion near the creek mouths.- In this

time period of slow accretion there has not been a

significant diminishing of the beach width. It Is not

known whether there has been a diminishment of the

nearshore,profile or offshore bar.

BEACH PROCESSES

Figure /0 Illustrates the typical features of a sand

beach and the names of the features. The offshore bar is not

illustrated.

"The natural beachfront exists In a state of dynamic

tension, continually shifting In respons e to waves, winds,

Page 20

COASTAL AREA

COAST BEACH OR SHORE NEARSHORE ZONE
BACKSHORE FORESHORE T INSHORE ZONE OFFSHORE
I

SURF ZONE BREAKER ZONE
LE T

Seactift. Berms
Dunes. E tc. I i
Breakers
H Water Level
Berm Edges- S40"' z-
e @ovv@-V@ae@ Le!Lel . . . . . .
Rip Feeder Channel
Low-T-de Terrace
Plunge Point

16
Figure Features of a typical sand beach. (From U. S. Army
Corps of Engineers, 1971).
7
S.-C
'-ftic- -- Berms
D u n e s \E,_lI
r

O'D

and tide and continually adjusting back to equilibrium."

(Clark, 1977, pp. 320) The components of the typical sand

shoreline store sand to defend against wave attack. Figure

shows sand removed from beach and foredune storage moves

to the nearshore and is stored there as nearshore accretion

and offshore bars. With the return of gentle swells. the

stored sand is then moved back on to the beach.

The energy used to move sand off the beach and out of

the foredune reduces the energy of the attacking waves.

Clark further describes the shoreline protective aspect of

this sand movement under wave attack:

"Eroded materials is carried out and deposited offshore
where it alters the beach's underwater configuration.
Accumulating sand decreases the offshore beach slope
(makes it more nearly horizontal), thereby presenting a
broader bottom surface to storm wave action. This
surface absorbs or dissipates through friction an
Increasingly large amount of destructive wave energy
which would otherwise be-focused on the shoreline behind
the barrier." (Clark, 1977, pp. 322)

'The offshore bar also provides protection from wave attack:

"Where the-land meets the ocean, nature has provided the
shore with a natural defense against the attack of the
waves. The first defense against the waves is the
sloping nearshore bottom which dissipates the energy or
weakens the force of the deepwater waves. Yet some
waves continue toward the shore with force and energy
still at tremendous levels until they near the beach.
There they break, and unleash most of their destructive
energy. This process of breaking often builds In front
of the beach another defense In the form of an offshore
bar which helps to trip following waves. The broken
waves reform to break again and say do this several
times more before finally rushing up the foreshore of
the beach. At the top of wave uprush a ridge of sand is
formed and serves as a defense against uprush of
following waves. Beyond this ridge, or crest of the
berm, lies the flat beach berm which is reached only by
higher storm waves." (U.S. Army Corps of Engineers,
1971, pp. 7)

Page 21

Duno Crest

Berm

M. M. W.

Prolile A Normal wave action

PA. L -W,

;zz
0 S 1 0 P,
M. H. W.

Profile 8 - Initial attack of
storm waves M. L.W.

ACCRETION
@P"fi'le A

Storm Tide
M. H. W.
0 S
0 IV

Crest
Lowering Profile C Storm wo-ve atic)ci*@"::-'::;:.:...,:.-.::,...,:@
i Crest of foredune 4..; M. L.W.
I Recess=
N4 ACCRETION
/P'onle A

0 'T
0
Af M H. W+

.00, L W
Profile 0 After storm wove Wock.
normal wave action
ACCRETION
,1P00rr00f1'iI'e* A

Figure Schematic diagram showing shoreline changes and
sand movement under storm wave attack. (From U.S. Army Corps of
Engineers, 1973).

if sand Is removed from this dynamic system, then there
will be an adjustment to the shoreline toward a new

equilibrium. This adjustment would be through shoreline

erosion, foredune er osion, and/or reduction In the volume of

offshore sand.

Winds bloW-ing across the beach move sand in a series of

hops and bounds. This method of particle movement in air

(and water) is known as saltation. The typical northwest and

southwest winds carry sand from the foreshore to the

backshore and from the backshore on to the foredune. Sand

that is blown Into the creeks can be carried back into the

ocean. Wind transportation of sand is an important part of

-the natural repair of foredunes eroded by storm waves.

During periods without storm waves and particularly

during the summer. the sand in bars is moved Inland by

relatively gentle waves and swells on to the beach where it

develops a wider beach and a berm (see Figures and The

widened beach renews protection for the foredune and upland

from wave action and provides a wider area for wind

transportation of sand.

Substantial deposits of logs were found south of Spring

Lake/Watseco Creek Outlet, at Spring Lake Outlet and slightly

south of Crescent Lake Outlet. Old aerial photos Indicate

that driftwood deposits have been common features at the

creek outlets and near the jetties over at least the last 46

years. The photos also Indicate logs behind the roredune

after major storm events. Drift logs are also exposed In

eroded foredunes.

Page 22

Aerial photos taken April 28, 1939, after a large storm

in January, show driftwood in almost all the creek outlets,

where it was wedged into the narrow landward part of the

outlet areas. The 1939 photos also show that the largest

concentrations of drift logs are near the mouth of Nehalem

and Tillamook Bays, the drift logs are mostly on low lying

land accreted as a result of jetty construction, and a large

number of drift logs had been tossed or floated over the then

low foredunes. Aerial photos taken in 1964 show a

substantial volume of driftwood near Crescent Lake outlet on

both the north and south. Photos taken In 1966 show the logs

-near Crescent Lake outlet and another large driftwood deposit

in an area slightly north of Saltair Creek. Some of these

logs were apparently tossed inland onto Highway 101 In a

storm in December 1967.

Natural deposits of drift logs that accumulate at the

south of streams have a positive value in protecting against

ocean erosion. The accumulation acts as an extension of the

foredune in reducing the velocity and impact of breaking

waves in large storm/high tide events. In an undeveloped

area, these are qualities worthy of protection.

In developed areas the accumulations of drift logs at

the south of streams can have negative values. Fresh and

marine flood waters drain from areas east of the logs at a

slower rate than through a clear channel. Outflow past the

logs can cause local scouring of stream banks. Driftwood at

the creeks can be moved by storm waves and freak waves to

Page 23

inland areas, damaging houses and blocking the highway and

railroad.

Driftwood removal has been occurring where accumulations

build up at the stream outlets, except at Spring Lake Outlet.

Removal in other beach and foredune areas is occurring but

currently appears to be only at a low level. A higher level

of removal is not feasible because of the sparse distribution

of driftwood, except in the Watseco Creek area.

There are presently no massive accumulations of

driftwood at the base of the foredune In the study area, but

there is a large accumulation at Watseco Creek In a former

--creek channel. The following narrative Is provided in

anticipation of future accumulations and In regard to the

accumulation near Watseco Creek.

-Driftwood deposits on the backshore can either be a

benefit or destructive force to the foredune. Massive

driftwood deposits that interlock provide excellent wave

protection by breaking up wave energy before it reaches the

foredune. They also collect wind-blown sand and can be the

start of new foredunes. Backshore deposits known to the

study team on other beaches are sometimes 50 to one 100

feet wide and a mile long. They tend to create a false

security for oceanfront proterty owners.

At Kla-he-nee Shores, north of Florence, Oregon, during

the El Nino waves of winter 1982-83, the entire driftwood

mass floated off the beach in less than three days. Wave

erosion was severe and emergency r1prap was permitted on

Page 24

2,200 feet of oceanfront. This same area had been stable for

twenty years due to the wave protection afforded by the

driftwood deposit. The same protection was afforded the sand

bluffs north of Siletz Bay from the bay to the Inn at Spanish

Head until beach logging was allowed in 1976. Severe wave

erosion followed the log removal, again resulting In

emergency riprap installation.

The partial removal of wood from Interlocked deposits

loosens the mass. Loose logs and stumps act as battering

rams, increasing erosion of the foredune and increasing

Inland structural damage. It appears that massive

-accumulations in backshore areas need to be evaluated and

either removed during summer or left Intact.

Driftwood should not be removed when it accumulates in

an eroded portion of a foredune because it aids the natural

repair of the foredune.

The accumulation of drift logs near Watseco Creek are

not well interlocked and could be pushed or floated further

inland where they could block Watseco Creek. As a result,

Watseco could move south and possibly endanger existing

development. However, the logs are now occupying a gap in

the foredune and will probably increase the rate of repair of

the foredune. The logs at Watseco Creek could also be washed

out and transported to other shoreline or stream south areas.

It is our opinion that the logs in the former foredune area

should remain to aid in the rebuilding of the foredune.

Page 25

FOREDUNE PROCESSES

"Previous to the introduction of European beachgrass
in Oregon in the late 1800's, the active foredune on
most shorelines was absent or was a relatively low,
discontinuous ridge composed mostly of remote to closely
spaced mounds., After European beachgrass colonized the
foredune.-the increased deposition of sand elevated the
ridge first as Isolated hummocks that coalesced and
resulted in a relatively continuous ridge." (U.S.
Department of Agriculture, Soil Conservation Service,
1975)

On much of the study area shoreline, an active foredune

occurs on the east side of the beach. The foredune is

susceptible to ocean flooding, ocean erosion, battering by

.wave carried logs, and wind erosion and deposition. To a

--limited extent, the foredune Is capable of acting like a dike

against ocean flooding and Is capable of dissipating wave

energy through erosion of the stored sand. However, ocean

flooding is still a hazard where the foredune is low In

elevation and thin enough to be breached by erosion. High

waves can erode through or overtop a foredune. The foredune

with European beachgrass reduces the sand transporting

capacity of wind. This results in deposition of sand on the

foredune instead of on inland areas. The beachgrass and

other foredune vegetation also reduces the capacity of wind

to transport sand off of the foredune (wind erosion). The

protective capability of the beach-foredune system is

enhanced by retaining sand in the foredune.

"Dunes are the final protection line against the
sea, and are also a savings bank for the storage of
sand against a stormy day.

"And stormy days do come. Strong winds blow high waves

Page 26

before them. These waves are so huge that the
nearshore slope weakens them only slightly. The thrust
of the wind and the waves toward the shore raises the
elevation of the sea and large waves pass over an
offshore bar without breaking. If the storm occurs at
high tide, the storm surge and the tide superelevate the
waves and some of them may break high on the beach or
even at the base of the dunes. After a storm or stormy
season, the natural defenses are again reformed by
normal wave And wind action." (U.S. Army Corps of
Engineers, 1971, page 7)

Snapshots dating In the early 1900's (Walker, 1983)

indicate that there was little or no active foredune

formation at that time In the central portion of the study

area. It is reasonable to assume that without a hardy

beachgrass and with repeated wave erosion, the only active

foredunes were isolated hummocks that developed on the

accreted lands adjacent to the jetties and on backshore

portions of the beach. Much of the central shoreline appears

in old photos as a broad, gently sloping beach leading Inland

to a relatively well vegetated stable dune ridge. This dune

is classified as a younger stabilized dune by the U.S.D.A.

Soil Conservation Service (1975). Remnants of this stable

foredune remain in the study area to the east of the 1939

shoreline mapped from aerial photographs in this report

(Technical Report Map). Remnants of the old foredune are

generally absent near the creek outlets. The highest

elevations on the old foredune are in the-Lake Lytle

area, and the highest elevation there Is 43 feet. The mature

vegetation and height of the old foredune Indicates that much

of the shoreline had been stable for at least 50 years. Th e

construction of the jetties and the introduction of European

Page 27

beachgrass altered that condition.

The date of the Introduction of European beachgrass in

the Nedonna/Rockaway area was not determined during this

Investigation. Some residents and publications identify the

1930's as the probable time. Aerial photos from 1939

indicate that the beachgrass was present at that time. Newly

accreted land near the jetties had a low, hummocky, active

foredune in 1939., The aerial photos were taken 3 or 4 months

a@fter a severe storm. This early predecessor of today's

active foredune had been severely eroded, breached and

overtopped by storm waves.

The foredune continued to increase in height and width

after the introduction of European beachgrass. The growth

has been episodic because of both local and wide-spread

wave erosion. Repeated episodes of erosion in some locations

has produced one or more remnant foredune ridges east of the

present foredune. These remnant ridges are evidence of the

episodic nature of accretion on this shoreline following the

introduction of European beachgrass. Repeated erosion and a

limited supply of wind-blown sand has resulted in poor

foredune development near stream outlets throughout the

history of active foredune development.

Variations in ocean erosion, wind deposition, and

grading has resulted in a complex and somewhat Irregular

active foredune. The foredune is illustrated on the

Technical Report Map. Figure /2-Is a generalized cross

section of a foredune. The unstable creek outlet areas are

Page 28

BEACH FORESLOPE CREST 'iBACKSLOPEi BACK AREA

Figure 12. Typical foredune cross section and classification of features.

treated separately.

The foreslope is the seaward side of the foredune. Most

foreslopes in the study area show evidence of past erosion.

Erosion in the past one or two years has left a nearly

vertical foreslope In some locations. After erosion of the

foreslope, wind transported sand, driftwood and European

beachgrass combine to repair the damage to the foredune. At

first the repaired foreslope has an uneven surface and an

uneven distribution of beachgrass. With more sand deposition

the foreslope eventually develops a relatively even slope and

coverage of beachgrass. Depending on the amount of foreslope

erosion, it can take two to over five years for the foreslope

repair to occur. Of course, further erosion can take place

before repair can be completed.

The foredune crest is the top of the foredune. The

shape, width and height of the crest, like the foreslope, is

dependent mostly on the past erosion history or the amount of

grading. Wave erosion can extend In to the crest or, in

extreme cases, all the way through the crest. Wind

transported sand and European beachgrass repair the erosion

damage over several years, similar to the natural repair of

foreslope damage. As a result, the crest varies in the study

area from very thin, low and irregular to broad, high and

relatively smooth.

The backslope Is inland of the crest. It Is relatively

smooth and evenly sloped where there are lowlands inland from

the foredune, such as in the Nedonna Beach area. In other

Page 29

areas backed by an older, stable foredune, such as the Lake

Lytle oceanfront area, continuous accretion and episodic

erosion has resulted In a condition where there is almost no

backslope. What backslope exists merges In a short distance

in to the back area.

The back area referred to in this study refers to the

conditionally stable and stable sand areas Inland from the

foredune backslope. In the Nedonna Beach, Saltair Creek,

a'nd Watseco Creek areas the back area is low lying land.

In the rest of the study area, the back area is composed of

remnants of older foredunes and stable dune ridges.

The protective capability of the foredune is primarily

a function of its bulk (height and width). The height is

protection from flooding and its overall bulk is protection

from eortion. European beachgrass Is Integral to the

protective ability of the foredune. The beachgrass helps to

build a high foredune and the roots bind the sand, thereby

Increasing resistance to wind and wave erosion. A gently

sloping foreslope is also protective In that the energy of

wave runup can be dissipated with a minimum amount of

erosion.

At this time there is no known optimum dune bulk. In

developed areas the optimum hiehgt is logically that

elevation necessary to adequately protect Inland areas from

probable levels of ocean flooding. In regards to width,

the wider the better because in a wide foredune there is more

sand in storage available to be eroded. In regard to the

Page 30

slope of the foreslope, the rule is the flatter the better,

but European beachgrass traps sand and builds up so rapidly

that maintining a low slope is unrealistic. A foreslope of

1:4 to 1:3 (25% to 33%) Is reasonably realistic and is the

range of managed f.o.redune foreslopes in Europe.

Page 31

FLOODING

Two type of flooding occur In the Rockaway/Nedonna area

-- fresh water and ocean flooding. Fresh-water flooding

is not a direct subject of this study, but driftwood and sand

block stream outlets and aggravates inland flooding. Ocean

flooding occurs when high tides combine with large storm

surges and/or large waves. Past ocean flooding has not been

as extensive as the flooding projected for the 100-year flood

(U.S. Department of Housing and Urban Development, 1978).

A comprehensive documentation of past ocean flooding in

the study area, as well as the rest of the Oregon Coast, was

compiled by Stembridge (1975).using newspaper accounts. it

was not possible or necessary within the limitations of the

Rockaway/Nedonna study to review newspaper reports specific

to the study area. The information from Stembridge has been

examined for specific information on the study area and was

combined with information provided by Schlicker and others

(1972), information from the tabloid (Memories of Rockaway,

Oregon) compiled by Rosemary Walker (1983), and from
3
Information provided by residents. Table A provides the

information compiled from these sources.

The U.S. Department of Housing and Urban Development

(HUD) (1978) and Federal Emergency Management Agency (FEMA)

(1982) have conducted studies and prepared maps of coastal

flooding for use in establishing flood hazard areas and flood

Insurance rates. This Is the only mapping of coastal flooding

for the study area. The regulatory flood Is the 100-year

Page 32

Table.7,. -Damaqing Events Affecting.the Rockaway/Nedonna Area
Feb. 1911 Breakers and drift logs over railroad.

Jan. 1914

Dec. 1931 Local flooding and logs tossed on Hwy. 101.

Oct. 1934 Local flooding and logs tossed on Hwy. 101.

Dec. 1935 Local flooding and logs tossed on Hwy. 101.

Jan. 1939 Local flooding and wave tossed-log damage to houses at Twin

Rocks and Manhattan Beach. Recurrence interval of 75 years.

Dec. 1940

Oct. 1941

Nov. 1948 Local flooding and-logs tossed inland

Jan. 1953 Local flooding and logs tossed inland. Shoreline erosion at

Nedonna Beach.

Apr. 1958 Local flooding and logs tossed inland.

Jan. 1960 Local flooding and logs tossed inland.

Feb. 1960 Local flooding and logs tossed inland.

Oct. 1960 Freak wave damaging houses at Saltair Creek and tossing logs

across Highway 101.

Spring 1962 Shoreline erosion at Rock Creek
1Q.1-
Dec. 1967 Local flooding and logs tossed over foredune at N/fdonna Beach,
and Manhattan Beach; logs tossed on Highway 101 at Rock Creek

and Saltair Creek.

Dec. 1972 Shoreline erosion.

Dec. 1974 Logs tossed inland.

Feb. 1976 Logs tossed inland. Recurrence interval of 10-15 years.

Oct. 1977 Shoreline erosion.

Feb. 1978 Shoreline erosion.

Winter 82/83 Shoreline erosion.

flood, a hypothetical flood with a statistical recurrence

Interval of once every 100 years (1% chance of occurrence In

any year). The mapping (reproduced on the Technical Report

Map) shows several classes of flooding. Of primary interest

in this study is the velocity flood area (area subject to

wave action) and the base flood elevations. In Inland areas,

the base flood elevations or depth of flood waters is

illustrated as well as the extent of areas prone to flooding.

Flooding extends Inland beyond the limit of the map. See the

flood mapping previously cited for more information.

The flood mapping is based on numerous hydrologic

and hydraulic factors. Consideration was given to tides,

storm surge, wave action, swell, offshore water depth,

effective beach slope, and other factors (U.S. Department of

Housing & Urban Development, 1978). Changes in offshore

depth and changes on the beach and foredune following the

mapping were not considered (Green, personal communication).

In fact, It is those variations In offshore and onshore

conditions that result in the differences in base flood

elevation from one shoreline reach to another shown on the

Technical Report Map.

"On the open coast, effective beach slope and storm wave
breaking height may vary dramatically In a relatively
short distance along the shoreline. Therefore, two
adjacent reaches may have 100-year flood elevations that
differ by more than I foot." (U.S. Department of Housing
and Urban Development, 1978)

The accuracy of the ocean flood hazard mapping is

dependent on how such change occurs over time. In the study

area, there have@been changes In foredune width and height

Page 33

and beach width and slope since the flood studies. Further

changes will occur through shoreline erosion, recovery fro&

the recent El Nino, and possibly from natural changes in the

offshore water depths (including seasonal changes).

The Tec.hni'dal Report Kap illustration of flood zones was

reproduced from HUD and FEMA flood insurance rate maps. The

original maps are at a scale of I Inch = 1000 feet and 1 inch

600 feet. The Information was transferred as accurately as

possible to the working map scale of I inch = 100 feet.

An attempt was made to Improve on this mapping by

transferring the base flood elevation to the working map

-using the much more accurate topography on that map. This

approach was found to be confusing by many persons

involved in this investigation. That Information has been

removed from the maps, but the elevation in feet above mean

lower low water is shown for the base flood.

The regulatory flood insurance mapping supercedes

natural and man-made changes in the elevation and

configuration of the land. Unfortunately this leaves a small

but significant discrepancy between the regulatory flood and

the real factors controlling shoreline flooding. This is one

of the reasons why foredune grading, allowable under

Goal 18 of the Statewide Planning Goals and Guildlines, Is

limited to an elevation of 4 feet above the base flood

elevation. The extra 4 feet is necessary to accommodate the

constantly changing nature of the shoreline and the

inflexible nature of flood plain regulation.

Page 34

SHORELINE EROSION AND ACCRETION

There is very little documentation of shoreline erosion

in the study area. The Oregon Department of Transportation

has a file on the 1977-78 erosion at Nedonna Beach.

Schlicker and others noted erosion near Watseco Creek in

1971-72. A publication by Terich and Komar (1974) on the

erosion at Bayocean Spit Included a diagram that inferred

that erosion occurred in the study area as a result of the

construction of the north jetty at Tillamook Bay. Erosion of

much of the foredune in the southern half of the study area

was noted in a study of the beaches and dunes of Oregon

(U.S.D.A. Soil Conservation Service and Oregon Coastal

Conservation and Development Commission, 1975).Further

information on shoreline erosion has been obtained by field

investigation, aerial photo interpretation, and information

supplied by residents and County Planning Department staff.

The lack of published documentation Is apparently the

result of the small amount of structural damage in the study

area that has been caused directly by erosion. There has

been severe local erosion, primarily.near the stream outlets

and near the jetties. Erosion by rip currents preceding

storm surges and large waves has Increased flood damage In

some locations. Examples of erosion events are presented but

do not represent all of the erosion that has occurred In the

recent past.

It appears that foredune erosion In the study area Is

similar to erosion events on other portions of the Oregon

Page 35

Coast. In the following quote Komar (1979) discusses the

erosion that took place on the Siletz spit in the 19501s,

early 1960's and In the winters of 1972-1973, 1975-1976, and

1977-1978.

"In each instance foredune erosion did not occur over
the entire-length of the spit. Instead, it was limited
to two or three zones, each some 200 feet of spit
length. This localization of dune erosion was governed
by the positions of rip currents as ...

"In summary, erosion of foredune areas can be very
rapid, removing some 100 feet of property in two or
three weeks. The erosion is mainly centered in the lee
of rip currents which hollow out embayments into the
beach. Maximum erosion occurs under large storm waves,
and is also aided by the high water levels of spring
tides. Following erosion the foredunes may be re-
established by beach sand washing and blowing into the
eroded zone; drift logs aid in dune reformation by
trapping the wind-blown sand." (Komar. 1979)

There is also little information on shoreline accretion

In the study area. Accretion on the shoreline south of the

Nehalem jetties was briefly acknowledged by the Corps (U.S.

Army Corps of Engineers, 1980). There are several reports

that refer to the accretion north of the Tillamook jetties

(Lizarraga-Arciniega and Komar, 1975; Komar and others.

1976a; and Komar, 1978). Cooper (1958) identified the study

area as progradational and noted widening of the beach

possibly as a result of construction of the north jetty at

Tillamook Bay. Dicken (1961) notes progradation at several

points in the study area determined from comparison of aerial

photographs taken in 1939 and 1960. Stembridge (1975) maps

the shoreline as prograding and notes that the least

accretion was 30 feet between 1939 and his Investigation.

The shoreline and accretion in the study area that has

Page 36

been documented in this investigation is illustrated on the

Technical Report Map and described in the descriptions of

each of the management units and stream areas in the study

area. Supposedly, accretion in the study area of the ocean

shoreline could be attributed to: 1) lowering of sea level,

2) increased sand supply, 3) construction of Jetties, or 4)

introduction of European beachgrass. The ultimate cause of

shoreline accretion in the study area is not known, but It is

probably because of the introduction of the Jetties and the

introduction of European beachgrass.

@WIND EROSION AND DEPOSITION

Wind erosion does not have a severe impact at this time.

Minor scouring of poorly vegetated foredune areas is

occurring in all management units. This tends to perpetuate

uneven foredune growth, but I-t does not present a direct

threat to inland properties. Wavecut escarpments in the

foredune are experiencing wind erosion, but this tends to

deposit sand at the base of the escarpment and promote repair

of the foredune foreslope.

The current practice of uncontrolled foredune grading

now occurring In the Nedonna Beach and other sections is

causing minor wind erosion because of the exposure of sand

unprotected by beachgrass. Due to the shallow depths and

direction of the present grading cuts (east-west), most wind-

blown sand deposits are small and occur on the easterly

portions of the same lot. The beachgrass In the newly graded

areas generally recovers quickly because the excavations are

Page 37

shallow. Vegetation on adjoining lots has also prevented

major wind erosion problems.

CREEK OUTLET PROCESSES AND FEATURES

Shoreline processes at creek outlets are apparently

poorly understood. No published information was round In our

research. This section of the report presents conceptual

Information on shoreline processes analyzed in respect to the

observed features at creek outlets In the study area. The

format used here is to first describe the observed features,

second describe the potential processes, and third to attempt

to analyze the causes of the observed features.

Figure __ illustrates the typical features found at

creek mouths In the study area. The northern and southern

limits of the area of creek influence was determined from the

Inland curvature of the shoreline. Because the shoreline at

the creek areas has changed more radically over time than the

foredune areas (see Figures and __), the area of

creek influence was determined from historical shorelines, as

well as the present shoreline. Former shorelines were mapped

from historic aerial photos dating back to 1939. In some

cases the shoreline is further inland than In 1939, but In

most cases the shoreline Is further seaward than In 1939. In

the latter situation the area between-the former shoreline

and the present shoreline Is an area of dune hummocks, active

wind erosion and driftwood.

The present shoreline near the creeks Is

backed by a low, thin. poorly developed foredune or nor

Page 38

foredune at all. The presence of emerging foredune ridges

near creek outlets appears to be related to a recent history

of shoreline accretion, and shorelines recently subject to

erosion have little or no developing foredune.

Observations made during this study (April 1985 to

February 1986) indicates that wind and wave deposition of

sand in the creek outlet areas'occurs during periods of calm

seas and low creek flow. Erosion occurs during periods of

storm waves and high stream runoff. Erosion appears to

typically leave a beach excarpment or berm of a few Inches to

several feet in height on the beach. In some cases the

erosion extended to the vegetated shoreline and In to the

poorly developed foredune or to previously placed revetment.

The erosion appears In most cases to be caused by ocean

waves, but in one creek area (Spring Lake outlet) there was

testimony by one resident that the combined flow of Spring

Lake outlet and Watseco Creek caused shoreline rosion on the

north side of the area of creek Influence. This occurred

during the recent El Nino when there was a net northerly

littoral transport of sand that might have pushed the creek

flow northward against the former shoreline. The

configuration of shorelines at Rock Creek and Crescent Lake

outlet Indicate that stream erosion might have contributed to

shoreline retreat.

Review of historic aerial photos indicates that the

creeks migrate within the area of creek Influence. It is

logical that channel migration would occur as a result of

Page 39 -;

fluctuations in the creek flow and deposition,of sand by

waves, littoral transport and wind transport. Migrating

channels are characteristic of streams and rivers on deltas

and at their months where not controlled by jetties. Two

recent riverine examples are the mouth of the Necanicum River

at Seaside and the mouth of the Alsea River at Waldport. In

both of these situations shoreline erosion was related to

shifts in channel locations.

A stream delta was found to occur at all of the stream

outlets on aerial photos and in field investigation at low

tide. The delta is illustrated on Figure __ by the westerly

bulge in the low tide line. It is reasonable to assume that

these deltas form from stream transported sand. It is also

reasonable to assume that the deltas are constantly changing

In form and volume In response to stream flow, stream

location, littoral drift, ocean erosion, and wave deposition

of sand. It Is not known how such these deltas block or

alter littoral transport.

JETTIES

The Nehalem Bay jetties on the north and the Tillamook

Bay jetties on the south have had a profound effect on

beaches and dunes in the study area. Jetties are placed to

stabilize a river south at a particular location as it enters

the ocean. Without jetties, river mouths tend to migrate in

response to littoral movement of sand and offshore sandbars,

as well as In response to river flow, and river sediment

load, and changes in channel location in the estuary.

Page 40

Extensive studies of the effect of jetties on shorelines

along the Oregon Coast have been done by Dr. Paul Komar of

Oregon State University: Komar describes the process as

follows:

"It is seen that where two jetties are constructed,
there is beach sand accumulation both to the north and
south, immediately adjacent to the jetties. This
deposition and shoreline advance occurs because an
embayment Is formed between the newly constructed jetty
and the pre-jetty shoreline. Before jetty construction,
the shoreline curved Inward toward the inlet and was In
equilibrium with both the ocean waves and with the
currents coming in and out of the inlet. Jetty
construction eliminated the inlet currents acting on
that curved portion of shoreline, leaving only the
waves. The waves broke at angles to the curved
shoreline and so moved sand Into the embayment until it
completely filled with sand (Figure __). Once the
embayment filled and there was a smooth and nearly
straight shoreline parallel to the dominant waves, then
a zero net littoral drift once again prevailed. After
this stage is reached there are no additional large-
scale adjustments of the shoreline due to the presence
of the jetties. There a new equilibrium Is achieved,
and shoreline changes do not continue Indefinitely."
-(Komar, 1979, pp. 25-26)-

In fact, Nedonna Beach is such a filled embayment.

Prior to construction of the Nehalem jetties the Nedonna

Beach area was part of the river mouth and curved shoreline

re-entrant.

"The sand that fills the shoreline embayments produced
by jetty construction must come from somewhere, and most
of it comes from shoreline erosion at greater distances
from the jetties. Thus a symmetrical pattern of erosion
and deposition results with beach sand accumulation
immediately adjacent to the jetties. both to the north
and south, and with erosion at greater distances from
the jetties." (Komar, 1979, pp. 26)

"The amount of shoreline retreat produced by jetty
construction In areas, such as the Oregon coast where
there Is a zero net littoral drift. Is a function of the
size of the embayment to be filled adjacent to the Jetty
and the length of beach over which erosion occurs to
supply the sand." (Komar, 1979. pp. 27)

Page 41

"The shoreline affected by the Tillamook and Nehalem
jetties appear to be at or near equilibrium. However,
Bayocean Spit experienced dramatic erosion following
jetty construction and up to 1952 when the spit was
breached. Now that the embayment at the Jetty has
filled it Is reasonable to conclude that little.*If any,
Jetty-induced erosion will occur. Komar further notes
that once this equilibrium is established jetties can
subsequently be extended without producing additional
major shoreline readjustments and erosion." (Komar,
1979, pp. 28)

"The filled embayment areas to either side of Inlet
jetties are depandent upon the presence of the jetties.
If the jetties are allowed to degrade than there may be
some erosion of filled areas. Prior to rehabilitation
in 1980-81, the Nehalem jetties deteriorated to the
point that they were covered with water at high tide.
The shoreline at this time curved back Inward into the
inlet but.not as much as prior to jetty construction
meaning that without rehabilitation further erosion
might have been expected." (Komar, 1979, pp. 28)

Reconstruction of the Nehalem jetties was completed In

the fall of 1982. The rehabilitated jetties have, In concert

with the 1982-83 El Nino, resulted in substantial accretion

of the beach at the south jetty. Approximately 200 feet of

beach widening occurred in some locations from October 1978

to January 1984.

The jetties were rehabilitated to standards superior to

the original construction according to Tom Clapper and Harold

Herndon of the U.S. Army Corps of Engineers (personal

communications, 1986). The large, outer armoring stores were

carefully placed rather than randomly end-dumped and a core

of smaller store was placed. The jetties have an economic

life expectancy of 50 years, but maintenance will be requ-Ired

in 15 to 20 years (1997 to 2002).

Because there Is no absolute assurance of maintenance of

Page 42

the jetties or of the projected life expectancy, It is

recommended that no new development be allowed on lands at

the north end of Nedonna Beach between the existing foredune

and the jetty, the condition of the jetties be monitored and

newly accreted lands adjacent to the south jetty should be

developed because of the possibility of future erosion and

flooding as the jetties deteriorate.

FOREDUNE MANAGEMENT UNIT DESCRIPTIONS AND RECOMMENDATIONS

The shoreline ofthe study area has been divided into

fore foredune management units (See the Technical Report

Map). From the north to south, the units are:

1) Nedonna Beach - extending from the south jetty at
Nehalem Bay to Crescent Lake outlet,

2) Lake Lytle Oceanfront - extending from Crescent Lake
outlet to Rock Creek,

3) Rockaway Beach - extending from Rock Creek to Saltair
Creek, and

4) Rockaway South/Twin Rocks Beach - extending from
Saltair Creek to Spring Lake Outlet/Watseco Creek.

The shoreline was divided Into these four

landscape/management units based on an analysis of the

physical characteristics of the components of the shoreline

(beach, foredune and upland area). This analysis confirmed

our initial Impression. Each shoreline between the cre ek

mouths in the study area has consistent landscape

characteristics. However, it was the condition of the

foredune on the westerly facing shoreline and at the creek

mouth areas that necessitated the management unit divisions.

The physical processes and characteristics at the creek

Page 43

mouths have produced a foredune that curves Inland compared

to the rest of the shoreline and the foredune Is poorly

established or nearly non-existent at the creeks.

The following Is a description of the foredune

management units and recomendation for foredune management.

Descriptions and recommendations for creek outlet areas

follow the section on management units.

NEDONNA BEACH MANAGEMENT UNIT

General

This management unit extends from the recently

rehabilitated south Jetty at Nehalem Bay to the area of

Influence of the stream outlet of Crescent Lake, a shoreline

distance of about 5900 feet. (See the Techncial Report Map.)

The north end of Nedonna Beach is similar to stream

outlet areas in having a foredune that curves Inland, but

this area is not treated separately as are the creek outlets.

This Is because experience at other jetties indicates that

the area will develop a new foredune west of and connected to

the existing foredune as a result of rehabilitation of the

Nehalem jetties. Treatment of this area as a foredune Is

desirable at this time to promote inland protection from

ocean flooding and erosion. If the Jetty Is allowed to

deteriorate, then the area would need to be managed like the

unstable stream outlet areas.

. This foredune unit begins on the north on land that

accreted to the shoreline after the construction of t he

Nehalem jetties. The south Jetty was completed In 1915 (U.S.

Page 44

Army Corps of Engineers, 1980). The westerly extension of

shoreline adjacent to some jetties on the Oregon Coast have

been documented by Lizarraga-Arciniega and Komar (1975) and

summarized by Komar and others (1976a) and Komar (1978). The

initial accretion occurred rapidly following jetty

construction in 1915 until about 1920, but deterioration of

the jetties reversed the trend to one of shoreline erosion.

Erosion has occurred In this area but cycles of erosion and

foredune repair has resulted in a roughly stable, slowly

accreting shoreline with a foredune that is only 50 to 70

feet wide at some points. Recent rehabilitation of the

Nehalem jetties has resulted in increased accretion near the

jetties that will probably continue for several years and

will probably result in a new foredune west of the present

foredune.

The.middle portion of the Nedonna Beach area has been

subjected to less ocean erosion and more wind-blown sand

deposition compared to the northern portion. As a result,

the foredune locally over 200 feet in width and up to 32 feet

In hieght. There are also remnants of an older foredune

about 70 feet east of the present foredune. This slow

accretion does not mean that the area is free from future

ocean erosion. In 1977-78, this beach was subjected to

substantial erosion of the foredune.

In the southern portion of Nedonna Beach, the foredune

is 22 to 28 feet in elevation. The height decreases toward

Crescent Lake outlet on the south. Adjacent to the Manhattan

Page 45

Beach State Wayside, the present foredune is backed an the

east by an older, stable dune that Is less than 26 feet in

elevation.

ytgttation

The vegetation.line has been moving seaward on the

foreslope of this accreting beach. The dominant specie is

European beachgrass which is.in a vigorous state of growth

because of wind-blown sand deposition. There is less than 5%

sea lyme-grass. It is showing the same vigorous growth but

it is currently providing no competition for the European

beachgrass. American sea rocket Is growing sparingly at the

winter high tide line. However, its unburied condition

indicates a very mild spring and early summer this year
(1985) with little eolian (wind blown) sand deposition from is

prevailing northwest winds. The foreslope is the forward

slope of a very Irregular foredune. Large voids in the

vegetative cover cause severe hummocking that then result In

wind scour. West of the active foredune crest is a newly

forming foredune characterized by hummocks occupied primarily

by European beachgrass. Note: See Appendix -_ for more

Information on foredune vegetation.

The average width of the crest of the current active

foredune is shown on the Technical Report-Map. For the

purpose of this study, the sapped lines of the crest of the

foredune are only average. Mapping of all of the small

variations would not be feasible and would not be useful for

purposes of the management plan. One winter's southwest

Page 46

winds and waves would alter the small variations. On the

crest, the dominant species is European beachgrass In a

vigorous state of growth due to sand deposition from the

beach. Sea lyze-grass in small patches is holding Its own

and Is scattered throughout the crest area. In the central

portion of this management area the sea lyme-grass (a

secondary dune species) appears to be left over from the

early foredune that formed after the initial construction of

t'he south jetty at the mouth of the Nehalem River. Beach

pea, another secondary species, is present in the southern

two-thirds of this management unit. Again, this Is an

-indication of a foredune backslope species that is still

surviving on a new foredune crest. This current crest is

part of a natural erosion repair process by eolian deposits

of sand from the beach. The result is this mix of initial

(or pioneer) and secondary species. In addition, there is a

scattering of large headed sedge, Indicating the lessening

sand supply caused by the formation of the new foredune out

front. Grading (excavating) of the foredune crest has

occurred in this area, but there is no evidence of

substantial adverse impacts to the vegetative cover or as a

result of sand blown from the graded areas. This Is because

the majority of grading has not totally removed or destroyed

the roots of the beachgrass and the grass has recovered.

On the backslope of the Nedonna Beach foredune, vigorous

stands of European beachgrass still dominate. The upper half

of this backslope Is locally either European beachgrass, or

Page 47

lyme-grass with evidence of fertilization from eollan beach

sand deposition. Again, this stand is complemented by large

areas of beach pea. Graded areas have vigorous stands of

European beachgrass from recovery of old roots. The

beachgrass is of varying height and density, depending on

time of year of grading. The grass has not recovered after

grading only in two locations. Since they are both on the

north end, It is possible that they were unvegetated weak

spots before grading. However, herbicides may have been

used. The lower two-thirds of the backslope In the Manhatten

Beach Wayside area is a six of old lyme-grass stands and

scattered pockets of climax plants associated with dune areas

cut off from the beach sand supply. For more information on

plant species and plant succession on dunes, refer to Crook

(1979) and Appendix

The base flood elevation for the 100-year flood In this

management unit is 22 feet. The.foredune is over 32 feet in

elevation at its highest. At the County parking lot at the

north end of Nedonna Beach the foredune Is about 18 to 19

feet In elevation at its lowest. Northeast of the parking

lot the foredune curves Inland and drops in elevation. The

lowest foredune elevations are on the north and south ends of

this management unit. Grading has reduced some portions of

the foredune in elevation below the 22 foot base flood level.

The only documented flooding in this unit occurred at the

County parking lot In 19--.

Page 48

Erosion

This area accreted rapidly after the construction of the

jetties and apparently by 1938 had developed a low foredune.

A very severe storm in January 1939 eroded an unknown width

of the west side of the foredune and breached and overtopped

the foredune locally. In January 1953, there was shoreline

erosion at Nedonna Beach but the extent Is unknown. In the

winter of 1977-78, a rip current embayment resulted In

erosion on the northern end of Nedonna Beach. The shoreline

recession appears to have been about 100 feet. This erosion

threatened many homes and emergency riprap was placed to

reduce further erosion. The riprap Is illustrated on the

Technical Report Map, but it is now almost completely under

sand that has healed the washout of the foredune. There was

windspread shoreline erosion at the same time in Nedonna

Beach south of the rip current (see the 1970 and 1977

shorelines on the Technical Report Map), but the overall

erosion did not exceed 10 to 20 feet. The entire shoreline

has had minor erosion (in the tens of feet), but overall

there has been slow net accretion since 1939 on the

shoreline.

Accretion

After construction of the south jetty at Nehalem Bay in

1915, there was rapid accretion in the northern portion of

this unit. There are no records of the amount of accretion,

but 1939 aerial photos Indicate 1.200 feet or more of

accretion occurred. According to the U.S. Army Corps of

Page 49

Engineers (1980), the shoreline "built out rapidly until

about 1920, then began receding..." From 1915 to 1920 that

is 240 feet per year or more. The shoreline recession

was caused by the deterioration of the Nehalem jetties.

Rehabilitation of the jetties was completed in the fall of

1982. Accretion is now occurring near the south jetty.

Aerial photography indicates that there has been beach

accretion of 150 feet or more from 1978 to 1984, but the

accretion might be partially a result of the net northerly

littoral drift produced by the recent El Nino.

I The northern portion of this management unit has had net

accretion of up to 100 feet from 1939 to 1984 (an average of

about 2.2 feet per year). From 1939 to 1964, the shoreline

had accretion of up to about 100 feet. The extent of

intervening erosion during that time is not known. From 1964

to 1970 there was up to 80 feet of accretion. From 1970 to

1984 there was erosion caused shoreline retreat of up to 80

f e e t .

The central and southern portion of this unit had net

accretion of up to about 120 feet from 1939 to 1964. From

1964 to 1970 there was a maximum of about 40-feet of

accretion. From 1970 to 1984 the shoreline remained

somewhat stable with local erosion and accretion of a few

feet. For the peiod from 1939 to 1984 there was average

accretion of about 3.6 feet per year.

Present and Future Foredune Stability

The foredune at Nedonna Beach has generally demonstrated

Page 50

in stability since at least 1939 and can be expected to be at

least equally unstable for &similar or larger period Into

the future. From the completion of the south jetty In 1915

until about 1920 there was rapid accretion In the Nedonna

Beach area. The accretion was followed by an unknown total

amount of erosion resulting from the deterioration of the

jetties. The Corps of Engineers estimates an average of 5

feet per year. The aerial photos of 1939 are the earliest,

accurate Information available on the shoreline in Nedonna

Beach. From 1939 to the present there has been slow accretion

of the shoreline and growth of the foredune interrupted by

episodes of erosion.

There are documented erosion events in 1939, 1953, and

1977-78. These erosion events indicate that shoreline and

foredune erosion can be anticipated to be as great as 100

feet to 150 feet and to possibly breach the foredune locally.

Erosion that-has breached or nearly breached the foredune has

been generally limited to 1000 feet or less of shoreline

where a rip current embayment effectively concentrated the

foredune erosion. In 1977-78 the.foredune erosion was

concentrated on about 2000 feet of shoreline by two rip

current embayments. Widespread shoreline erosion has

occurred, but It has not been as damaging to the the foredune

and.has not threatened homes.

Eroded areas of the foredune have been naturally

repaired by wind and wave transported sand and then continued

to slowly accrete at an average rate of about 3.6 feet per

Page 52

year from 1939 to 1984.

An increase in the rate of foredune accretion is

expected to occur for several years following the

rehabilitation of the Nehalem jetties. The rate of accretion

will be greatest near the south jetty and smallest on the

south end of the Nedonna Beach Management Unit. There Is no

precedent on which to estimate the rate or total extent of

accretion. A new foredune will probably develop naturally to

the west of the present foredune from the south jetty to

about Riley Street. This new foredune will decrease the.

potential for ocean flood or erosion damage to existing

development in the Nedonna Beach area until the Nehalem

jetties deteriorate. If the jetties deteriorate the new

foredune will be eroded and the shoreline might return to the

condition previous to jetty rehabilitation, or there could be

further shoreline erosion and shoreline retreat.

South of about Riley Street there may be a short term

increase in the rate of accretion punctuated by episodes of

erosion. This will then be followed by a return to the

previous rate of slow accretion.

The south end of this management unit could experience

short term shoreline retreat if this area is a source of sand

for the new foredune near the jetty. Theie is no evidence

of substantial shoreline erosion in this area following jetty

construction, and there is a long shoreline area available to

supply sand for the accretion. To minimize the amount of

sand needed In the accretion area before an equilibrium

Page 52

condition is reached, it would be beneficial to promote

foredune development,in the accretion area by planting

European beachgrass or possibly by using sand fencing. This

would minimize the amount of sand blown inland behind the new

foredune and effectively taken out of the sand suppl.y-sand

storage system.

Portions of the Nedonna Beach Management Unit have

foredune crest heights in excess of that needed to protect

development from 100 year flood elevation (26 feet as

stipulated in Goal 18). There are also areas on the

foredune crest that are below this minimum level. Sand

excavated from crest areas above 26 feet elevation should be

first used to fill in crest areas that are below the minimum

height, thereby increasing the protective capability of the

foredune in the event of a flood with a recurrence interval

equal to or in excess of the regulatory 100-year flood.

Foredune management in this area should also promote widening

of the foredune to increase protection from ocean erosion.

Widening of the foredune increases the amount of sand in

storage in the foredune. the lands last.line of defense

against the ocean. The amount of widening that is practical

Is limited by existing development on the backslope of the

foredune and by the easterly limit of the beach. Because

there is no way to know how far westerly the foredune

can be extended It would be best to use excess sand from the

foredune crest to build up low and eroded segments of the

foreslope and not use excess sand to extend the foredune

Page 53

westerly until the other priority fill areas are satisfied.

Sand filling can occur where a new foredune Is actively

developing west of the existing foredune.

LAKE LYTLE OCEANFRONT MANAGEMENT UNIT

General

This section of shoreline is between the creek

influence areas at Crescent Lake outlet and Rock Creek, a

distance of about 6,800 feet. This Is the longest,

uninterrupted stretch of shoreline In the study area. Aerial

photos from 1939 show substantial development along the

shoreline. The photos also indicate damage to many

-structures in the storm of January 1939. The damaged homes

had been built west of the older, stable dune that is east of

Pacific Street. The Technical Report Map shows the shoreline

after the storm but does not--indicate the damage to inland

areas from flooding and wave tossed logs. Since 1939 the

shoreline has been slowly accreting, but there have been

periods of erosion alternating with accretion. Apparently

because of the alternating accretion and erosion, the

foredune is poorly developed. The average foredune crest

elevation is about 24 feet. The low and high points are

approximately 18 feet and 28 feet In elevation on the active

foredune crest. The base flood elevation ranges from 25 feet

on the north. 26 feet and 27 feet in the middle of the unit,

to 23 feet on the south end. Only a small area at the south

end of the management unit exceeds the minimum elevation for

grading. This unit is not suitable for dune grading. Dune

Page 54

management could Increase the flood protection ability of the

foredune.

Y@gttation

Seaward foreslope growth appears to have been limited

since at least 1939. While accretion is now taking place,

field information and aerial photographs suggest continuing

cycles of erosion and recovery. The dominant species Is

European beachgrass with about 30% to 50% coverage on the

foreslope at this time. All beachgrass is in a state of

vigorous growth due to deposition of sand from the beach.

-Because of the sparse grass cover, hummocks and wind scour

troughs exist now and will continue creating an unstable

foredune with low-lying weak spots. With minor surface

grading, beachgrass planting-of unvegetated areas, and a

fertilizer maintenance program, this foreslope area could

provide increased protection to Inland development, though

erosion will continue to occur periodically.

The crest section of the Lake Lytle Oceanfront foredune

system is in a state of natural recovery from past erosion.

The dominant species is European beachgrass showing vigorous

growth due to sand deposition. The conditions here are

similar to the foredune crest in the Nedonna Beach area. The

crest area Is uneven In height, and the vegetative cover is

weak.

In this management unit, the backslope area is very

short or indistinguishable from remnants of previous foredune

Page 55

crests. Vegetation consists mainly of old stands of European

beachgrass with a mix of climax plants such as coast

strawberry, seashore lupine, salal, and shore pine.

The Technical Report Map shows the base flood elevations

for portions of this management unit and the inland extent of

the 100-year coastal flood with velocity (wave action).

Inland of the velocity flood zone the map shows areas that

would experience shallow flooding (one foot deep on the

average), areas above the 100-year flood level but below the

500-year flood level, and areas of minimal flooding. This

information comes from the Firm Flood Insurance Rate Map

(Federal Emergency Management Agency, 1982).

There is very little documentation of flooding in this

unit. S.chlicker and others (1972) noted damage to beachfront

houses In the January 3, 1939 storm. That was a 75 year

storm according to the U.S. Department of Housing and Urban

Development (1978). They also mention damage in the December

1967 flood. In both cases the damage was attributed to surf-

swept logs.

Erosion

This area has had episodic min or erosion (tens of feet).

The erosional escarpment of recent erosion (probably the

winter of 1982-83) has healed in the central portion of the

management unit and Isalmost healed on the north end. This

erosion apparently effected the ent ire shoreline in this unit

Page 56

and resulted in about 5 to 20 feet of shoreline retreat. The

condition of the foredune suggests that widespread but minor

shoreline retreat.might be common in this unit. Local

erosion of the shoreline has also occurred where rip current

embayments have reduced the width of the beach.

Accretion

In 1920, the shoreline in this unit was apparently near

the present location of Pacific Street (Walker, 1983). By

1939 land had accreted west of Pacific Street and houses had

been built on-the new land. From 1920 to 1939 there nay have

been about 100 feet of accretion (over 5 feet per year).

Aerial photographs indicate that many homes built on the new

land experienced flood damage in the storm of January 1939.

The newly formed foredune survived the storm but was severely

erode d on the west side, and it was apparently overtopped

throughout the unit. From 1939 to 1964 there was an average

of 50 feet of accretion (2 feet per year). From 1964 to

1977, there was as average of about 30 feet of accretion (2.3

feet per year). The net affect of the erosion and accretion

In this unit is a narrow foredunewith relatively low relief.

After erosion episodes, there is an erosional escarpment.

The escarpment is healed by wind blown sand. and the

shoreline continues to slowly accrete.

Present and Future Foredune Stability

This foredune management unit has had slow accretion
0 Interrupted by minor erosion and shoreline retreat since
1939 and possibly since 1920. From 1920 to 1939 the

Page 57

accretion rate way have been In excess of 5 feet per year.

After 1939 the average accretion rate has been a little over

2 feet per year. 'There is no evidence that this trend will

stop or reverse In the foreseeable future. Erosion events

will occur in the future. Some will be local (about 200 to

1000 feet of shoreline) and widespread erosion will Involve

all or nearly all of the unit.' Maximum shoreline retreat

will generally be less than 30 feet. The unique coincidence

of two erosion events In one year could almost double this

rate of retreat. Eroded areas will repair naturally and then

continue to slowly accrete.

Flooding and damage to structures has occurred here and

will occur in the future. Eventhough this management unit

Is not suitable for foredune grading, management of the

foredune could decrease the potential for future flooding and

damage. The goal of the management would be to build up a

higher foredune to reduce wave overtopping. This may not be

desirable to many residents and businesses because of loss of

views. Management is recommended to Include minor grading to

smooth the foreslope and crest of the foredune, selective

planting of European beachgrass and fertilization of the

beachgrass.

ROCKAWAY BEACH MANAGEMENT UNIT

General

This management unit Is almost 1100 feet in length; the

shortest management unIt In the study area. It extends from

Page 58

the area of Influence of Rock Creek to the area of Saltair

Creek. The foredune Is relatively low and Irregular because

of episodic erosion and accretion, patchy vegetation, and

wind erosion. The unit is subject to ocean flooding because

of the low height-of the foredune. There has been local

shoreline erosion, mostly related to the occurrence of rip

current embayments. Since 1939 there has been accretion of

about 100 feet on the north end and about 350 feet on the

s"outh end. Foredune grading I not feasible In this unit
because the foredune is too lo:, but management in the form
of vegetation management and minor grading could increase
flood protection for some developed inland areas. However,
the amount of increased protection for existing development
would be small.

--y2g2tation

In this unit, the entire length of the foredune

foreslope area has experienced episodic accretion and

repeated wave erosion. As a--result, the vegetation line Is

very uneven with large gaps and wind scour troughs. This

problem is magnified by some grading and by heavy foot

traffic on the north portion. The present vegetation is

scattered clumps of European beachgrass down to the winter

high tide line.

As illustrated on the Technical Report Map, this

foredune crest area lacks any consistent height or width.

The present dominant plant species Is beachgrass, growing in

a series of hummocks. The condition of the grass varies in

relation to the eolian beach sand deposits that have moved

over the foredune.

Vegetation on the backslope In this area Is weak with

Page 59

old stands of European beachgrass scattered th roughout on

hummocks and remnants of older foredunes. The area's rough

nature, especially in the southern portion, Indicates past

cycles of severe erosion and recovery.

The 100-year base flood elevation In this unit Is 23

feet. Grading would be allowable on the foredune only if it

exceeded 27 feet in elevation. The highest foredune

elevations are at the south end of this unit. The highest

elevation is 23 feet. The lowest sapped foredune areas are

on the north end of his management unit (around 17 to 18 feet

-in elevation).

The foredune and the immediate inland area has been

flooded in the past and will flood again In the future.

There are no specific reports of ocean flooding in this area,

probably because the existing development is on a higher

stable dune east of the present foredune. Dwellings and

commercial structures are on or protected by land In excess

of 22.5 feet in elevation.

Erosion

Aerial photos and vegetation indicates that an unknown

but substantial amount of shoreline retreat has periodically

occurred in this management unit. The erosion appears to

have been related to rip current embayments and to'unit-

wide shoreline retreat. The north end of the unit appears to

have been particularly prone to rip current embayment

formation. The amount of shoreline retreat Is not evident

Page 60

an the Technical Report Map because of limited aerial photo

coverage. What Is evident from the aerial photo mapping of

shorelines is that from 1939 to 1966 there was less than 70

feet of shoreline accretion. What the shoreline mapping does

not show is shoreline retreat In January 1953 and In the

spring of 1962. From 1966 to 1970 there was little shoreline

erosion, and there was up to 150 feet of accretion. From

1970 to 1984 there was little accretion, probably because of

erosion in 1972, 1974, 1976, 1977, 1978, and the winter of

1982-83.

Accretion
----------

This management unit has had slow accretion, but ocean

erosion and wave overtopping has resulted in a very irregular

rate of accretion. From 1939 to 1977 there was about 130

feet of accretion on the nort-h end of the unit (about 3.4

feet per year). In the same period there was about 230 feet

of accretion at the south end of the unit (about 6 feet per

year). However, from 1939 to 1966 there was very little net

accretion (see the Technical Report Map). There had probably

been more accretion in the period from 1939 to 1966, but

apparently extensive shoreline retreat occurred In 1962.

From 1966 to 1970 there was very little erosion and the

shoreline accreted rapidly. From 1970 to 1977 there was only

a small net amount of accretion, probably because of

shoreline retreat in the storms of December 1972, February

1976 and October 1977. There has been little change In the

shoreline since 1977, probably because of shoreline erosion

Page 61

in February 1978 and in the El Nino period in 1982 and 1983.

Present and Future Foredune Stability

I As in the other management units previously discussed In

this report, there has been slow accretion in this foredune

management unit-area. However, the low and irregular

foredune and the evidence of extensive shoreline retreat

Indicates that the present foredune is unstable and subject

to ocean erosion and wave overtopping. The only stable

landforms are east of the 1939 shoreline shown on the

Technical Report Map.

Foredune grading is not feasible in this unit because of

-the low elevation of the foredune crest and because of the

potential for future shoreline retreat. Management of the

foredune by minor grading and Increased beachgrass coverage

would improve the ability of--the foredune to protect inland

areas from ocean flooding and erosion. However, there Is the

attendant danger of fostering new land development in low

elevation areas west of existing development. Further,

establishment of a higher and broader foredune Is limited by

a relatively short beach area available as a source of wind

transported sand for a foredune. If foredune management Is

attempted in this area It should only occur if there is an

effective restraint on land development west of the line of

existing development.

Page 62

ROCKAWAY SOUTH/TWIN ROCKS MANAGEMENT UNIT

General

This management unit extends from the area of influence

of Saltair Creek to the area of influence of the combined

Spring Lake Outlet and Watseco Creek, a shoreline distance of

about 1800 feet. The highest elevation on the foredune Is

about 23 feet. The lowest part of the foredune Is about 26

feet in elevation. The 100-year base flood elevation is 24

feet on the north end and 19 feet on the south end. The

.foredune is not high enough to allow foredune grading under

-Goal 18 provisions. Dwellings east of the foredune are only

subject to minor ocean flooding under existing conditions In

the event of an 100-year flood. Th'is unit has had slow

accretion since at least 1939. There have been periods of

local and unit-wide erosion but natural repair of the

foredune and accretion has followed the erosion events.

ytgetRtion

The vegetation in the foreslope area of the foredune Is

recovering from recent erosion. European beachgrass is the

dominant species, but coverage Is sparse. As a result of the

sparse beachgrass coverage and natural foredune recovery from

erosion, there Is some minor wind erosion, sand deposition,

and uneven development of the foredune.

The crest of the foredune Is Irregular because of the

repeated episodes of erosion and the resultant wind erosion,

sand deposition and uneven development of beachgrass

Page 63

coverage. The dominant vegetation on the crest Is European

beadhgrass.

This backslope area Is one of the most stable of the

management units. Species present, besides old nutrition

starved beachgrass,-are the typical climax dune species.

Surface grading in previous years appears to have caused no

severe or persistent vegetative problems, probably because of

the shallow depth of excavation.

E12291119

The base flood elevation is 24 feet in the northern

.portion of this unit and 19 feet on the south end. The

--foredune is only 16 to 23 feet in elevation and is subject to

overtopping in a major flood. Existing structures are on an

old and stable dune ridge about 250 to 400 feet east of the

active foredune. The structures are generally at an

elevation of 20 feet and many of the structures would be

subject to flooding in a 100-year flood. Much of the

flooding would be'shallow in depth, but those structures

subject to velocity flooding (wave action) could be damaged

by the wave action and surf-,swept drift logs.

Erosion

Overall this unit has accreted despite episodes of

erosion. Erosion has been both unit-wide and local. Local

erosion is typically related to the occurrence of rip current

embayments In the nearshore that narrows the width of the

beach. The Technical Report Map Illustrates shorelines

mapped from aerial photos, but photos are avilable for only a

Page 64

limited number of years.

The napped shorelines Indicate wide-spread erosion

between 1970 and 1977 and between 1977 and the mapping for

this study (1984). This unit-wide erosion probably occurred

In December 1972, February 1976, October 1977, February 1978

and in the winter of 1982/1983. Previous episodes of wide-

spread erosion undoubtably occurred but are Impossible to

document with the available information. Available

information indicates that wide-spread erosion has resulted

in shoreline retreat of 50 feet or less.

Rip current embayments have resulted in local shoreline

-erosion of about 500 feet in length and about 50 feet In

depth in the period from 1966 to 1984.

Accretion

-Overall there has been "t accretion of the shoreline in

this management unit since at least 1939. Aerial photos

taken in April 1939 indicate that this area experienced

accretion shortly after the completion of construction of the

north jetty at Tillamook Bay In 1912, but the onset of

accretion began at an unknown time. From 1939 to 1984 there

was net accretion of as little as 200 feet on the north end

of the unit and as such as 350 feet on the south end. This

translates to an average net accretion rate from over 4.4

feet per year to almost 7.8 feet per year. From 1966 to

1970, apparently a period of little ocean erosion. there was

an average rate of 20 feet of accretion per year. From 1970

to 1977, a period of time with many shoreline erosion events,

Page 65

there was no net accreti'on.

Present and Future Foredune Stabilltv

The foredune is insufficent in height to allow grading.

There has been accretion of the shoreline, but episodic local

and unit-wide ocean erosion combined with'wind erosion has

resulted in a foredune that is low and irregular in

elevation. Because there is no evidence of change in

shoreline processes we believe that the past process of slow

accretion will continue. It can also be assumed that

unmanaged future foredune development will continue to

produce a foredune that is low in elevation and irregular
I

.because of the ocean and wind erosion.

Vegetation management could produce a more stable

foredune with Increased prote.ction for existing ifiland

structures. However, management would necessarily include

monitoring of the foredune condition and periodic maintenance

of the foredune vegetation.

Presently, because of the probability of velocity

flooding behind the foredune, there should be no development

of structures west of the existing line of dwellings along

Breaker Avenue. Any development west of the existing line of

dwelli,ngs would be subject to the hazards of velocity

flooding, surf-swept driftwood, wind erosion, wind-blown

sand deposition, and shoreline retreat. Further development

in thi.s area should only be allowed If there is a plan for

perpetual foredune management, demonstration of long-term

stability of the managed foredune, and assurance of a future

Page 66

free from velocity flooding.

CREEK OUTLETS - DESCRIPTIONS AND RECOMMENDATIONS

CRESCENT LAKE OUTLET

General,

This shoreline area is illustrated on Figure

Crescent Lake outlet has influenced about 1650 feet of the

shoreline. Before the stream was constrained by a highway

and railroad bridge the creek probably migrated over a

shoreline area that extended further to the south. The

drainage area of this creek Includes Finney Creek,

Steinhilber Creek, Lake Lytle, and Crescent Lake.

The foredune in the creek area of influence is poorly

developed and low in elevation, typical of the area of

influence of creek outlets in the study area. As a result

the area behind the foredune Is prone to ocean flooding.

This creek outlet area also displays a trait

characteristic of other outlets in the study area: erosion

and accretion is larger and the area of influence is larger

north of the outlet than to the south. Presumably this is

because storm waves approach the shoreline and run up on the

shoreline from the southwest. Waves generated by

southwesterly winter storm winds are higher than northwestly

summer waves, and winter tides are generally higher than

summer tides. ks a result the northern shorelines. which

face winter waves tangentially, take the brunt of the energy

in the waves and In wave run-up. Accretion of the shoreline

Page 67

north of the creek outlets therefore might occur in periods

when winter storm driven waves do not coincide with high

tides. Unfortunately the aerial photos used In this study do

not confirm or disprove this hypothesis.

Mfgttation

The foredune and the European beachgrass present Is

poorly established on the north side of this creek outlet

area. The most northerly 340 feet of this unit has a very

thin active dune area with an older stable dune Immediately

adjacent on the east. Further south on the north

side there are foredune fragments up to about 19.5 feet in

elevation and dune hummocks but the average dune height is

less than 18 feet in elevation and the area is poorly

vegetated. Just north of Crescent Lake Outlet there Is an

erosion escarpment that is partially protected by a revetment

placed to protect the railroad tracks. The beachgrass Is

also sparse here.

South of Crescent Lake Outlet there,is a low foredune

that is very sparsely vegetated on the foreslope because of

recent erosion. Part of the crest and all of the backslope

area Is well colonized by beachgrass indicative of recent

stability, but the foredune is generally thin and largely

below 20 feet in elevation.

E!224ing

The base flood elevation for the 100-year flood Is 19

feet. Low spots In the foredune (about 16 feet elevation on

the north end and less than 16 feet on the south) would

Page 68

allow for flooding behind the foredune.

Erosion

The north side of Crescent Lake outlet has experienced

substantial erosion and retreat of the shoreline. From 1939

to 1964 there was over 200 feet of erosion. From 1939 to

1977 there has been as much as 230 feet of shoreline retreat.

There have been periods of shoreline accretion (1964 to 1979)

but erosion has dominated.

The south side of Crescent Lake outlet has been very

stationary in the period from 1964 to 1984. Observations

made in the field in 1985 indicate that this apparent

stability is the result of frequent erosion of the shoreline

and a slow rate of natural repair to the foreslope of the

shoreline.

Accretion

The northern half of this creek area has had more

erosion that accretion. There has been a small amount of

accretion on the northernmost end of the area of creek

influence. The accretion totaled about 90 feet from 1939 to

1970 (2.9 feet per year). There was then shoreline retreat

between 1970 and 1977. From 1977 to 1984 there was net

accretion. but the newly accreted shoreline area is a low

elevation foredune foreslope and is subject to renewed

erosion in the near future. From 1964 to 1970 there was

accretion north of Crescent Lake outlet of over 100 feet, but

between 1970 and 1977 there was a nearly equal amount of

Page 69

shoreline erosion.

The southern half of this creek outlet area had at least

150 feet of accretion since 1939, but since about 1964 there

has been a net balance of erosion and accretion and a

relatively stationary shoreline.

Prese"nt and Future Foredune and Shoreline Stabilltv

The northern portion of this area of influence of

Cresent Lake outlet has a low, poorly developed foredune.

The area has expeienced extensive erosion and moderate

accretion, and as a result has had a very unstable shoreline.

The low elevation of the foredune means that severe ocean

flooding will overtop the foredune and flood the State

Wayside area.

The south side of the creek area has been relatively

stationary since 1964 and this will probably continue.

This condition is partially the result of the fact that the

south side of creek outlets are not as prone to erosion from

winter storm waves-waves that approach from the southwest.

The southern shoreline will not experience substantial

accretion because this area is sheltered from wind-blown sand

deposition from southwest.winds by the Lake Lytle Oceanfront

shoreline and largely protected from northwest wind

transported sand by Crescent Lake Outlet.-

Page 70

ROCK CREEK

General

This shoreline segment is about 1500 feet in length.

About 66% of the shoreline is north of the creek outlet and

about 34% is south of the creek outlet. Elevation of the

foredune crest averages about 22 feet north of Rock Creek (16

feet to 28 feet is the range of elevations). South of Rock

Creek the crest elevations range from 16 feet to almost 22

feet. Commercial and residential structures behind the

foredune range from about 14 feet to over 25 feet In ground

elevation.

Most of the shoreline has accreted since 1939 but

shoreline advance has been interrupted periodically by

episodes of local erosion. As a result the foredune is

locally low in elevation and thin. The lowest elevations are

near Rock Creek and this is the area where there has been the

most damage from ocean flooding and surf-swept driftwood.

M@gttation

This shoreline segment is highly disturbed and this is

reflected by the sparse nature of the vegetation. The

domi.nant species along the shoreline is European beachgrass

but the distribution Is irregular because of heavy foot

traffic and past erosion. North of the creek outlet there is

a revetment that was placed to reduce shoreline retreat.

Further north is a shoreline foreslope that has experienced

repeated episodes of erosion. In this area the crest of the

active foredune has such better beachgrass coverage than the

Page 71

foreslope and there are secondary species, such as beach pea

present.

'South of Rock Creek the foredune is sparsely vegetated

because of heavy foot traffic, past grading, minor wind

erosion, and episodic ocean erosion. The parking lot Is

protected by a rock revetment, and there Is almost no

foredune. The foreslope, crest and backslope are hummocky

and sparsely vegetated with European beachgrass.

f122glng

.The base flood elevation Is 23 feet on the Rock Creek

shoreline. Only the northern third of the shoreline In the

area of creek influence is above this elevation. Foredune

elevations are about 16 feet near the channel of Rock Creek.

Even moderate flooding has been able to reach areas behind

the foredune and wave- tossed logs have been tossed on to and

across Highway 101.

Erosion

There has been net accretion of most of the shoreline

north and south of Rock Creek, but significant erosion has

resulted In only a small amount of total accretion (see

Figure Past erosion has resulted In the placement of

rock revetments on both the north and south shorelines, as

well as 200 feet of the channel of Rock Creek. Some of

this riprap is now partially buried under wind transported

sand.

Shorelines napped from aerial photos Indicate that there

was up to 40 feet of erosion north of Rock Creek sometime

Page 72

between June 1970 and December 1977, possibly in December

1972, December 1974, February 1976, and/or October 1977.

There Is no evidence of the amount of erosion that has

occurred south of Rock Creek, but vegetation, limited

accretion and the condition of the foredune indicates that

erosion of a few tens of feet has been common in the past.

Accretion

Most of the shoreline in the area of influence of Rock

Creek has had shoreline advance since 1939 (Figure __).

There was as much as 150 feet of accretion at the north edge

of the area of creek influence from 1939 to 1984 (over 3.3

feet per year). The amount of accretion diminishes to zero

near Rock Creek. The southern edge of the creek Influence

area has had as much as 170 feet of accretion between 1939

and 1984 (about 3.8 feet per year). The net amount of

accretion diminishes to zero near Rock Creek.

Present and Future Foredune and Shoreline Stability

The shoreline In the Rock Creek area of Influence has

experienced net accretion except near the creek channel.

This trend is expected to continue, but episodes of shoreline

erosion are also common in the past and will continue to

occur. Erosion will be most common north of Rock Creek.

Moderate ocean flood and erosion episodes have resulted in as

such as 40 feet of shoreline retreat. The maximum amount of

future shoreline retreat that should be anticipated is about

120 feet. This amount of erosion would occur from one severe

erosion event or several moderate erosion events In one or

Page 73

two years.

Inundation will continue to occur periodically near Rock

Creek and behind the foredune as a result of both fresh water

flooding and ocean flooding. ocean flooding could affect

areas behind the foredune as often as once every 10 years.

SALTAIR CREEK

General

Saltair Creek influences about 2100 feet of shoreline (Figure

About 60% of the affected shoreline Is north of the

creek and about 40% Is south of the creek. The elevation of

the foredune crest ranges from about 15 feet to almost 29

feet north of the creek and from about 14 feet to 23 feet

south of the creek. The foredune is relatively broad (about

150 wide at the widest) at the north end of the creek area of

influence, but the width and height diminishes toward the

creek. South of Saltair Creek there is almost no foredune.

Instead there is a broad, relatively flat topped sand ridge

that is up to 300 feet wide and about 20 to 22 feet in

elevation. Aerial photos and field evidence indicates that

this area has been graded flat. The grading combined with

periodic shoreline erosion and a limited amount of wind

transported sand has resulted In almost no foredune

development like at the other creek outlet areas.

ytgetation

The foreslope of the foredune In this creek influence

area is recovering from recent erosion. The vegetation line

Page 74

is uneven and European beachgrass occurs in clumps and

patche s separated by open sand areas of wind and ocean

erosion. North of Saltair Creek the crest and backslope

areas are mostly occupied by European beachgrass in stands of

various age. Old nutrition starved stands of beachgrass

occupy hummocks and intervening areas are occupied by

moderately dense to mostly sparse stands of younger

beachgrass and areas of open sand. The crest and backslope

areas south of Saltair Creek have been graded. European

beachgrass predominates but a lack of wind transpo rted sand

from the beach has resulted In a relatively unvlgorous stand.

In addition to grading there appears to have been some mowing

of beachgrass and some attempts to establish lawns.

Flooding

The base flood elevation for the 100-year flood Is 20

feet north of South 6th Avenue and 23 feet to the south.

Velocity flooding would affect several dwellings near Saltair

Creek in an 100-year flood (see Figure The area near

the creek, particularly north of the creek, has been subject

to velocity flooding, shallow flooding and wave-swept

driftwood in past storms in January 1953, October 1960 and

December 1967. Several houses were pushed off of their

foundations and one house was pushed on to the railroad

tracks In the October 1960 storm (Walkes, 1983). Cinder

block and concrete walls and a rubble rack dike now provide a

limited amount of protection to houses north of the creek.

Flooding has occurred here In the past and will occur In

Page 75

the future because of the low elevation of the foredune near

Saltair Creek. The base flood elevation for the 100-year

flood is 20 feet at the creek and the land adjacent to the

creek Is only 14 to 16 feet in elevation. Dwellings near the

creek and behind the foredune are about 14 feet to IS feet In

elevation at the ground level.

Erosion

The shoreline within the area of influence of Saltair

Creek has experienced slow accretion but there has been

periodic shoreline erosion. Between 1966 and 1970 and

between 1977 and 1984 there was about 40 feet of shoreline

retreat Just north of the creek. There Is evidence of

erosion between 1970 and 1977 of between 40 and 100 feet

further north on the shoreline. South of Saltair Creek there

was local erosion of 300 to 400 feet of shoreline between

1966 and 1970. Shoreline retreat appears to have been about

30 to 40 feet in that episode. A similar amount of erosion

occurred in the same location between 1977 and 1984. Natural

foreslope repair was still occurring In 1985.

Accretion

The area north of Saltair Creek has experienced up to

300 feet of accretion from 1939 to 1984 (6.7 feet per year).

According to aerial photos there was very-little accretion

from 1939 to 1953 or if there had been accretion It was

followed by shoreline retreat, possibly in the storm In

January 1953. Sometime between 1953 and 1966 a rubble rock

dike was built north of Saltair Creek. A similar structure

Page 76

on the south side of the creek was probably place at the saine

time. The dike might have contributed to the increased rate

of accretion up to about 1970. From 1966 to 1970 there was

200 feet of shoreline advance (about 50 feet per year). From

1970 to 1977 one area had 100 feet of accretion (up to 14.3

feet per year), but the average accretion was 40 feet (5.7

feet per year). From 1977 to 1984 there was almost no

accretion.

South of Saltair Creek there was almost no net accretion

near the creek between 1939 and 1966. Near the southern edge

of the creek influence area there was up to 70 feet of

accretion between 1939 and 1966 (2.6 feet per year). From

1966 to 1970 there was up to 30 feet of accretion (7.5 feet

per year). From 1970 to 1977 there was up to 40 feet of

accretion (5.7 feet per year).

Present and Future Foredune and Shoreline Stability

The shoreline influenced by Saltair Creek is notably

different north of the creek compared to south of the creek.

The northern area is similar to other creek outlets in that

the rates of erosion and accretion are higher than south of

the creek. Because the accretion occurred rapidly, the area

behind the foredune is low in elevation. The foredune

diminishes in height and width close to the creek. It is

subject to ocean erosion and flood overtopping.

The area north of Saltair Creek has demonstrated

progressive accretion, but there appears to have been periods

of extensive erosion and ocean flooding. The shoreline north

Page 77

of Saltair Creek must be considered as unstable and prone to

sudden shoreline retreat as well as ocean flooding. This Is

demonstrated by a breach in the foredune about 500 feet north

of the creek.

The shorel ine south of Saltair Creek has only a small

amount of total accretion, and near the creek the shoreline

has been eroded as much as it has accreted. Near the creek

this shoreline is subject to erosion that could exceed

historic amounts. Dwellings near the creek and behind the

foredune are subject to ocean flooding, perhaps as often as

once every 10 to 15 years. Further south from the creek the

foredune has been graded to an elevation of about 21 feet

where the 100-year base flood elevation is 23 feet. The area

Is subject to severe floods but the foredune area is broad

and more resistant to ocean erosion than thin foredunes.

The shoreline in this area should continue to accrete slowly

but could be subject to local shoreline erosion greater than

historic levels. Erosion could extend to the 1939 shoreline

within the next few decades.

SPRING LAKE OUTLET/WATSECO CREEK

General

This shoreline area is Influenced by two creeks: Spring

Lake Outlet on the north and Watseco Creek on the south.

Presently, Watseco Creek flows north for over 2200 feet

before joining Spring Lake Outlet and then flowing to the

ocean. In 1969 and 1970 the two creeks had separate channels

Page 78

to the ocean. In 1966 the creeks flowed similar to the

present. I'n 1960 they were in separate channels.

After the construction of the north jetty at Tillamook

In 1912 there was relatively rapid accretion in this

shoreline area. Accretion continued until about 1977. There

could have been erosion episodes during that time, but there

is no evidence. Wide-spread erosion has occurred since 1977.

Yggetation

European beachgrass is the dominant species in this area

but the coverage Is very sparse. The foredune foreslope is

mostly open sand because of recent erosion. North of Spring

Lake Outlet and at the south end of this shoreline unit the

foreslope of the foredune has been almost completely eroded

in 1983, 1984 and early 1985. The foredune crest north of

Spring Lake Outlet is fairly well vegetated with beachgrass

and some.secondary species. South of Spring Lake Outlet

for about 1600 feet there is mostly open sand and scattered

areas of beachgrass where there has been wave overwash.

This area has only the hummocky beginnings of a foredune.

Further south there is a low fordune area with a crest of

beachgrass and a small amount of open sand. The backslope in

this area is similarly vegetated. North of Spring Lake

Outlet the foredune backslope is mostly vegetated with
beachgrass but there are secondary species present. Near the

row of dwellings on the eastern edge of the backslope there

are many climax species such as Shore Pine.

Flooding

The 100 year base flood elevation Is 16 feet from

Page 79

slightly north of Spring Lake Outlet to the south end of this

shoreline area. North of Spring Lake Outlet the base flood

elevation is 20 feet, 24 feet and 19 feet (see Figure

North of Spring Lake Outlet the foredune is adequate In

height to resis-t all but the most severe ocean floods. The

land adjacent to Spring Lake Outlet is over 24 feet In

elevation and should be free of all but the most severe

floods. South of Spring Lake Outlet there Is much low lying

area that is subject to flooding, but all of the existing

dwellings are above the 16 foot base flood elevation for an

100-Vear flood.

-Erosion

The foredune north of Spring Lake Outlet has eroded

significantly since 1977. There was as much as 150 feet of

erosion of this high foredune between 1977 and 1984. This

erosion Involved about 600 feet of shoreline.

South of Spring Lake Outlet at the north end of Pacific

Street there is riprap. This was apparently placed in

response to shoreline erosion. This erosion could be related

to the meandering of Watseco Creek or to ocean wave erosion.

South of Spring Lake Outlet for about 1400 feet there

has been a large amount of shoreline fluctuation and erosion

as a result of the meandering of Watseco Creek. Further

south there has been erosion of the foredune in the period

from about 1983 to early 1985. This erosion appears to be

related to the El Nino of the same time that produced a net

northerly littoral transport of sand. Foredune erosion

Page 80

extended from this area south to the north Jetty at Tillamook

Bay. There might have been as much as 50 feet of shoreline

retreat as a result.

Accret.ion

There has-been extensive accretion In this area as a

result of construction of the north Jetty at Tillamook Bay.

There was as much as 900 feet of accretion from 1939 to 1977

on the south end of this shoreline area.

The central portion of this shoreline has had net

accretion, but the meandering of Watseco Creek and ocean

.erosion has resulted in no net accretion of lands free from

-.the hazards of ocean flooding and ocean erosion.

The northern portion of this creek influence area is

similar to the other creek areas to the north. From 1939 to

1966 there was as much as 24-0 feet of accretion (almost 8.9

feet per year). From.1966 to 1970 there was little or no

accretion near Spring Lake Outlet. Further north there as
up to 70 feet of accretion (17.5 feet per year). From 1:70

to 1977 there was minor erosion about 500 feet north of

Spring Lake Outlet, but the rest of this shoreline area

accreted about 40 feet (5.7 feet per year). After 1977 there

was mostly erosion in this shoreline segment.

The southern portion of the Spring Lake Oulet/Watseco

Creek shoreline area has had net accretion since 1939. There

was shoreline retreat probably beginning in 1983 that was

continuing during the field investigations for this report.

From 1939 to 1966 there was 500 feet to almost 700 feet of

Page 81

westerly accretion (18.5 to 25.9 feet per year) near the

southern limit of this shoreline unit. From 1966 to 1970

there was about 60 feet of westerly shoreline growth (15 feet

per year). There was also northerly growth 6f the shoreline

of up to 200 feet. From 1970 to 1977 there was about 90 feet

of westerly accretion (about 12.0 feet per year). In the

same time period there was northerly shoreline extention of

about 200 feet.

Present and Future Foredune and Shoreline Stability

This shoreline segment is the area of influence of two

streams Spring Lake Outlet and Watseco Creek. Overall this

.-shoreline must be considered as unstable, particularly the

central portion where Watseco Creek has meandered widely, and

there are low elevations and a very poorly evolved foredune.

The northern portion is the most stable segment@of this area.

The area of creek influence north of Spring Lake Outlet

has had up to 400 feet of accretion since construction of the

north jetty at Tillamook Bay In 1912. Net accretion

continued until 1966 but there may have been periods of

erosion. Better aerial photo coverage is available for the

period after 1966. The most significant erosion occurred

between 1977 and 1984 when up to 150 feet of erosion occurred

to a relatively high and broad foredune. Similar Instability

and even greater erosion could occur in the future.

The central portion of this shoreline segment has been

very unstable because of Its low 'elevation and the

instability of the channel of Watseco Creek. The future of

Page 82

this area Is impossible to predict. However, past trends

indicate that Watseco Creek will continue to meander over at

least 1500 feet of shoreline, but continued northerly

accretion of the shoreline south of Watseco Creek may

continue to force-the creek into a northerly flow to a

confluence with Spring Lake Outlet. It is also possible that

sand and driftwood deposition could block the current channel

of Watseco Creek forcing the creek to establish a new channel

further to the south.

As a result of the past instability of this area and

probable future instability, it is recommended that no

--development be allowed within the sapped setback line. Even

with this level of protection some existing development could

requ.ire structural protection, particularly the development

at the south edge of this sho@reline segment.

Page 83

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Nedonna Beach
Foredune Grading Plan

Introduction

Objectives and Expected Results

Subarea Analysis and Recommendations

Subarea A: South,Jetty Subarea
Subarea B: Jetty Parking lot Subarea
Subarea C: Park Street Subarea
Subarea D: Riley Street Subarea
Subarea E: Western Street - Sunset Street Subarea
Subarea F: Lark Street - Beach Street Subarea

Specifications

Sand fences
Accessways through sand fencing
Beachgrass planting
Secondary planting
Crest grading
Foreslope shaping

Tables

1. Transplans needed with varied spacing requirements
2. Recommended native plant for dune stabilization

-2-

Introduction

This plan provides detailed recommendations for grading and stabilizing
the foredune at Nedonna Beach, Oregon. The foredune is presently high
enough in front of most houses (i.e. more from four feet above the 100
year flood elevation) to qualify for grading under Statewide Planning
Goal 18 (Beaches and Dunes). Grading is being done to restore ocean and
beach views of. oceanfront homes whose views have been blocked by dune
accretion. Proper placement and stabilization of the graded sand will
also repair and strengthen the foredune; improving its function as a
buffer to ocean flooding for the entire area. While the recommendations
in this report are specific to Nedonna Beach, the recommended grading and
stabilization techniques may be applicable to other developed foredunes.
Readers should also consider the following:

- This plan is based on a careful evaluation of the sand system
for the entire Rockaway-Nedonna shoreline;

- A variety of other human activities can affect stability of the
foredune and stabilizing vegetation. An accompanying foredune
management plan recommends controls on these activities which
need to be followed if these measures are to be effective.

- Foredunes are inherently unstable areas. The grading and
vegetative stabilization measures recommended here should
improve protection the foredune provides from ocean flooding,
but these actions cannot and do not guarantee damage from ocean
flooding will be prevented.

-3-

OBJECTIVES, AND EXPECTED RESULTS

The overall purpose of this grading plan is to allow crest grading as
part of a total program that will strengthen the foredune. This will be
done by:

- creating a uniform crest at no lower than 26'. This will
involve building up low spots (through a combination of filling
and or planting or fertilizing) and limited grading of crest

areas.

- widening the foredune in most areas by

(1) placing excess graded sand from the foredune crest onto the
foreslope.

(2) smoothing the foreslope and fertilizing and planting
European beachgrass in poorly vegetated areas to enhance
even accretion of sand on the foreslope.

- promoting a new foredune from approximately Western Street to
the South jetty to provide a more continuous foredune throughout
this stretch of shoreline.

Specific problems for individual areas are described in the subarea
descriptions which follow. The Specifications section describes how
corrective actions should be undertaken. These recommendations should be
followed unless the subarea recommendations indicate otherwise.

The timing of each management measure is important because of the
potential for grading to reactivate sand movement which would destabilize
the foredune. Generally, management measures should be done in the
following sequence:

-4-

(During the dormant season for beachgrass -- generally
between October and March)

Year I Foredune crest grading should be done in qualified areas
(i.e., where foredune crest is more than 4 feet above the
100 year flood elevation).

-Asindicated in the specifications, graded sand should be
used to fill low'spots on adjacent lots. Portions of the
crest that are currently below the base flood elevation
should, at a minimum, be filled to the base flood
elevation. Crests that are between the base flood
elevation and the.4,feet above base flood elevation level,
should also be filled. However, these areas may instead be
replanted with European beach grass or fertilized if there
is an adequate stand of grass.

Any sand not used in filling the crest should be pushed
forward onto the foreslope. Further alteration of the
foreslope should not occur at this time. (Grading of both
areas in the same year will result in sand inundation in
the back area.)--

The graded area should be immediately fertilized or if the
area is poorly vegetated replanted with European beachgrass.

For the area north of Western Street, a "new" foredune
should be started by placement of sand fences. This is not
a prerequisite for grading but should be done as part of
the overall program to strengthen the foredune.

Year 2: Grade hummocky foreslope areas to create a more even
foreslope to enhance sand accretion. This should only be
done where crest vegetation is adequately established (or

recovered) to capture most windblown sand or where
temporary stabilization measures such as sand fences are
installed. Also no mowing should be done until the
foreslope vgetation has recovered from grading.

Areas with more than 50 % vegetative cover should be
fertilized.

Expected Resul ts

Year 1: Grading will temporarily result in more open sand in crest
areas since dune grass will be bladed off or buried by
placed sand. These areas should recover in one growing

season.

The crest will be of a more uniform height throughout.
However, the total amount of sand in the foredune should
not change since sand will simply be redistributed within
the foredune system.

Areas with sand fences will begin to accumulate sand, and
depending on wind and weather conditions should fill
entirely within the first year. The result will be a low
(4-5 foot) open sand ridge up to 45-50 feet wide
immediately in front of the present foredune. The sand
fence may fill at different rates and high winter storm
waves might erode a portion of the dune. (This should not
seriously affect the foredune, especially if promptly
repaired.)

Sand captured by the sand fences will be sand which would
otherwise have accumulated in the foredune or blown behind
the foredune or beyond the jetties. Consequently there may
be a slight reduction in the rate of sand accretion on the
existing foredune. However, sand will accrete at normal
rates once sand fences have filled.

-6-

End of Vegetation on graded areas should be substantially
Year 2: recovered or established. Overall the crest should have
more and thicker vegetative coverage than prior to
grading. Depending on the strength of winter winds the
crest may begin to receive some new sand accretion although
most new material should be trapped in sand fences or on
the foreslope (in ungraded areas).

After grading, reshaped foreslope areas will temporarily
have a reduced ability to trap windblown sand. This will
increase sand accumulation slightly on ungraded crests.
(Prompt replanting or fertilizing of-European beachgrass
will reduce this effect.)

Sand fenced areas will have been planted with European
beachgrass. In its first six months the new grass will
capture only a little sand. Six to twelve months ater
planting the grass should be well established enough to
capture sand at a rate equal to other areas.

End of Vegetation on graded crests should be fully recovered, and
Year 3: the entire cres-t-should be well vegetated. Mowing may
temporarily reduce height of the grass, but when done
during the summer season and properly fertilized, it should
grow back thicker. Crest areas should be receiving only
small amounts of sand accretion.

Foreslopes reshaped during the previous year should have
well-established vegetation that is trapping most of the
sand accretion occurring.

Vegetation in sand fenced areas should also be well
established except in isolated pockets of erosion (which
should be in various states of repair depending on how

-7-

recently they occurred). The "new" foredune should be
trapping most of the windblown sand. The sand fenced dune
should grow at a rate of 18 to 24" per year.

Years 5-10

Notwithstanding major flood events the foredune should
--continue to grow oceanward. If foreslope vegetation is
properly established and maintained throughout the Nedonna
area sand accretion at the crest should be very slight or
could be stopped altogether. Instead windblown sand will
be entirely trapped by the widening foreslope. The
foreslope should prograde slowly as accretion occurs.

In areas where the foredune is widened through placement of
a sand fence the existing foreslope and crest will receive
less and less windblown sand as the "new" foredune grows in
height. The.result will probably be a slight trough
between the "old" foreslope and the "new" crest (actually
an elongated foreslope). The new foredune should continue
to grow in height and may eventually (10 years or more) be
as high as the existing crest. (It would be appropriate to
allow some sand to fill in the "trough" area through
periodic mowing after the finew" foredune is well
established.)

Some foreslope areas will likely be eroded by ocean storm
waves. It is assumed that where more than 50% of the
foreslope is eroded that the eroded slope will fill
naturally or be shaped and replanted. These areas will
recover, albeit inconsistently with adjacent areas. While
these areas are recovering hummocks may develop on adjacent
foreslope areas as a result of the eroded area's reduced
abili ty to capture windblown sand.

-8-

SUBAREA ANALYSIS AND RECOMMENDATIONS

Subarea A: South Jetty Subarea

Setting The foredune in this subarea is virtually non-existent.
Prior to rehabilitation of the jetties in 1981-82, the
shoreline receded at a northeasterly angle from in front of
-the jetty parking lot to the jetty. There are a number of
small hummocks above the high tide line but most of this
area slopes gently to an open sand area at an elevation of
10-12 feet. The absence of a well-defined foredune and
stabilizing vegetation is probably the result of wave
action and a rip current in this area prior to jetty
reconstruction. Since jetty reconstruction, the beach has
accreted substantially. Sand that is accumulating is
widening the beach oceanward and the profile of the beach
appears to be flatter. Because of the absence of
stabilizing vegetation sand is being blown across this area
both into back areas and across the jetty into the Nehalem
River.

As noted elsewhe-re maintenance of the jetties is critical
to the stability of the beach at this location. If the
jetties are not maintained their effect on ocean waves will
steadily lessen andthe area will likely erode back to its
pre-rehabilitation configuration.

The accreted'sand in this entire subarea (i.e. sand
accumulated since jetty rehabilitation) should be
considered a natural 'bank account' for the shoreline south
to Tillamook Bay. Much of the current accumulation is the
result of net northerly movement of sand from El Nino.
This sand may be eroded away as the beach system adjusts
back to the normal zero net drift pattern. This entire
0

open sand area is very unstable because it is subject to
ocean and river flooding or erosion and should not be
developed.

Absence of a foredune in this subarea means sand is being
blown over the jetty and to inland areas and lost to the
sand system. The absence of a foredune also creates a low
--opening for flooding into back areas.

Recommended Measures:

1. Steps should be taken to establish a new foredune in this area
to capture accreting sand and to provide improved flood
protection to back areas. The foredune should be extended due
north to the jetty from the existing foredune south of the jetty
parking lot. The foredune could be encouraged through plantings
of european beachgrass alone or by placement of sand fences
followed by beachgrass plantings once fences have filled.

2. This area does not qualify for crest grading because of its
elevation and the fact that there are no homes here. No other
grading appears to be appropriate here for the forseeable
future.

3. Emergency access across this area to the beach along South jetty
should be provided for. This can best be done by providing a
due east-west crossing wide enough for a single vehicle (10-12
feet). This should be located close to the jetty. The existing
access across the foredune at the jetty parking lot should be
fenced off.

4. The undeveloped area behind the vegetation line is subject to
ocean and riverine flooding. No development should occur in
this area unless there is a guarantee that the jetties will be
maintained for the life of the proposed development.

_10-

Subarea B: Jetty Parking Lot Subarea

Setting The foredune at the jetty parking lot has been seriously
damaged by the vehicle traffic and foot traffic across the
dune. Vegetation have been completely destroyed and the
foredune is much lower than the areas to the South. Access
-,at this location is needed for emergency vehicles to
conduct search and rescue at the south Jetty. The parking
lot is-also the only public access north of the Manhattan
Beach Wayside with off-street parking.

Recommended Measures

1. The foredune should be stablized to prevent sand deposition into
parking lot and to inland areas. Access for emergency vehicles
and pedestrians should be provided and designed to avoid harming
the foredune.

2. The foredune should be restored with a combination of sand
fences and dunegrass plantings. Fences should be placed to
widen the dune seawa-rd to provide increased erosion protection.

3. Sand fences should be constructed with openings to allow
pedestrian access across the foredune while sand is accreting.
These accesses should be oriented east-west to avoid wind and

erosion.

4. Once vegetation is well-established on the dune the access ways
should be fenced and revegetated and permanent accessways across
,the rehabilitated foredune should be opened.

5. The foredune crest is much to low to allow crest grading and
there are no oceanfront homes in this subarea. Grading in this
subarea should be limited to toreslope shaping necessary to
prepare the site for beachgrass plantings.

6. Vehicles should not cross the foredune at this location.
Instead they should travel due North of the end of Beach Drive
and cross the low beach or new foredune farther North closer to
the jetty. The access should be signe d "for emergency vehicles
only," to limit access to emergency, salvage and similar
operations. Where emergency access across the foredune is
necessary it can occur at the pedestrian accesses described
above.

Vehicle access at this location should be limited to search and
rescue at the jetty or on the beach. Vehicle access to the
beach for other purposes should occur at the south end of the
Manhattan Beach Wayside. The access there is much better
oriented and the dune is better developed to withstand vehicle
impacts.

Subarea C: Park Street Subarea

Setting This portion of the foredune has been developed with
homes. The foredune itself, is low (24-26 feet) and narrow
(averaging 130-170 feet in width). The foredune is poorly
to moderately vegetated. Cover in backslope areas is 100%
but crest areas are about 40-60% and some graded lots have
no cover. The foredune is narrowest and least well
vegetated on the north and gradually widens and is better
vegetated towards the south.

The condition of the foredune is a result of previous
erosion, grading and house construction. The four existing
homes north of Park Street are all located on the forward
portion of the crest. This has required grading to keep
the houses from being inundated with sand. The house
immediately north of the end of Park Street is lower than
the crest of the foredune on adjacent lands.

-12-

A rip-current centered near Park Street caused substantial A
erosion of this subarea in the winter of 1977 and 1978.
The foredune eroded back at this time. The foredune may
also have been graded to a slightly lower elevation as
rip-rap was installed. Virtually the entire shoreline was
rip-rapped at that time to prevent further erosion.
(Rip-rap was placed in an even line parallel to the shore
__20-40 feet in front of the homes). Since rip-rapping in
1978, the foredune has begun to recover and re-establish
itself. Except in two locations where view grading has
occurred the foredune now completely covers the 1978
erosion and rip-rap.

The pattern of hummocks and sparse vegetation indicate the
area has filled naturally, without man-made assistance.
(Property owners confirm this observation.) Presently, the
foredune expands 80 feet in front of the homes (varying
from 60 feet to 90 feet).

Management Recommendations

The foredune in this area need's to be stabilized through increased
vegetative cover and strengthened in both width and height. Several
specific steps are appropriate to accomplish this.

1. Plant open sand areas and areas with less than % cover with
European beachgrass per beachgrass planting instructions.
Plantings should be blended into the existing line of vegetation
or adjacent unplanted lots.

2. The foredune from Park Street North is too low to qualify for
grading of the foredune crest. Grading here should be limited
to smoothing the foreslope for planting of beachgrass.

-13-

3. Three of the eight houses south of Park Street qualify for some
grading of the foredune crest. The priority locations for
placement of graded material are low spots in adjacent crest
areas first and low or narrow portions of the foreslope second.
(see grading plan map)

(a) areas with 40 - 60% vegetative cover, should be replanted
-with European beachgrass per the specifications to provide
more uniform vegetative cover.

(b) low spots (i.e. below 26'), particularly graded areas or
breachs in the crest of the foredune should be stabilized
with parallel sand fences to promote even sand filling
followed by beachgrass plantings. Planting vegetation
alone is an acceptable alternative.

4. The new foredune to be created by sand fencing extends
throughout this area as shown on the maps.

Subarea D: Riley Street Subarea

Setting The foredune in this subarea is very similar to the Park
Street Subarea (Subarea C) with the following differences.

- The foreslope is noticeably wider (75-80 feet vs.
50-60 feet) and has slightly less beachgrass

cover.

- The crest has been recently graded (i.e. within
the last two years) in front of several houses in
this area. The crest is at approximately
24.5 feet or 1.5 feet below the approved grading
elevation.

-14-

The portion of the foreslope immediately forward
of the crest is steeper than the subarea to the
north, though both areas are characterized by
hummocky foreslopes.

Beachgrass in the graded areas is recovering well from
grading.

There is also a depression in the foredune north of the
northern house in this subarea apprently caused by vehicle
access. The depression may have been the result of use of
the site as a staging area for placement of rip-rap in 1978.

Management Recommendations

1. Crest grading is only appropriate for the southernmost house in
this subarea. Graded material from this lot should be used to
fill the crest on the adjacent lot to 26'. Alternatively, the
may be graded onto the foreslope if the adjacent area is
stabilized through beachgrass plantings and fertilization.

2. Foreslope grading is appropriate in this area and is needed to
create a more even slope. Foreslope grading will provide a
better slope for planting of beachgrass to enhance sand
accretion.

3. A new foredune should be constructed with sand fences in this
subarea in the locations shown on the map. The new foredune
should be tapered into the existing wider foredune to the north.

Subarea E: Western Street - Sunset Street

Setting The foredune in this subarea is wider, taller and better
vegetated than those to the north. The crest averages

-15-

50 feet in width and height varies from 25 to 30 feet. In
this subarea, the foredune is progressively wider and
better vegetated to the south.

The foredune in this subarea is in better condition than
the Riley Street subarea because homes are set back
slightly further, there has been less alteration of the
foredune and no recent ocean erosion. Actually the homes
are located on the crest of an 'older' foredune. There is
a slight trough in front of this "older" foredune and an
apparent, though poorly formed, crest and foreslope in
front of the trough. (See generalized cross section)

The 1977-78 erosion event appears to have tapered out at
the edge of this subarea; only the four houses north of
Western Street were rip-rapped at that time. Also the
Northernmost rip-rap is located 20-30 feet further west
than rip-rap on lots to the south suggesting less erosion
occurred here.

Much of this variation in the crest, which varies in height
from 25 to 30 feet, is the result of unevenness of a
naturally formed foredune. It is also the result of
grading of the foredune crest. ( of the built
lots in this.subarea have been graded.) The crest of the
foredune in the middle of this subarea (between cross
sections 23 and 24) occurs about 50 feet landward*of the
crest in the remainder of this area. This sinuous crest
creates an opportunity for both wind-blown sand and severe
ocean storm waves to,overtop the foredune at this location.

The foredune west of Western Street has been not fully recovered
from breaching that appears to have occurred in 1977-78 when it
was used as an access way for placing rip-rap. While the site
has covered with sand it is not vegetated and the crest is 6 to
8 feet lower than on adjacent lots north and south.

-16-

Public pedestrian access appears to have occurred west of the
end of Western Street. While the access point is lower than
surrounding areas, lowering may have been caused by access for
placement of rip-rap in 1978 and subsequent grading of the lot
immediately to the south rather than pedestrian use.
Nonetheless, the crest is bare for 25-40 feet in this area.

Management Recommendations

1. Low spots in the foredune should, at a minimum, be planted with
European beachgrass to encourage growth in the height of the
foredune in this area. In particular, the breach at the end of
Western Street should be planted, preferably after use of sand
fences to raise the elevation of the crest at that location.

2. Many of the lots in this area presently qualifies for some crest
grading. The amount of sand to be graded will not be adequate
to fill low spots up to the recommended crest elevation (26').
Consequently, lower crest lots that do not receive graded sand
should encourage crest growth by applicaton of fertilizer and
planting bare areas with european beachgrass.

-17-

Subarea F: Lark St. - Beach St. Subarea

Setting: This stretch of the foredune is consistently higher, wider
and better vegetated than the areas to the south. All of
the homes in this area are located 25-100 feet landward of
the crest. Most are located on an older foredune just west
of Beach Drive. These are generally the older oceanfront
--homes in this subarea, and were apparently built before the
present foredune accreted to its current height.

The backslope in this subarea is well vegetated. There is
a complete cover*of european beachgrass, with a mix of
secondary vegetation including some small shorepine. There
are alos several noticeable depressions in the foreslope.

The crest in this area is wide (100-125'), well -
vegetated, with an even low-relief characteruized by flat
areas and numerous low hummocks. The crest on many of the
lots has been graded or mowed but the entire area appears
to be at or above the recommended crest elevation and the
vegetation is in very good condition.

The foreslope, like that immediately to the North, is 50-75 feet
wide, with a gentle slope punctuated by a series of small
hummocks 0 to 2' in height). Vegetation cover varies from
25-50% with the southernmost area being better vegetated than
the area to the North.

Management Recommendations:

1. Crest grading in this area may involve substantial movements of
sand since the crest is two to five feet above the allowed
grading elevation. Also, there are few low spots in the crest
that need additional material. Consequently most of the graded
material should be pushed toward the foreslope further widening
the crest.

-18-

Specifications

Sand Fencing

Type of Fence: Four foot high, wooden lath snow fencing or plastic
fencing (such as Miraffl. (Green or tan is preferred
color for plastic fencing.)

Posts: Six foot heavy-duty steel posts.

Wire: 14 Gauge galvanized steel wire.

Placement: Fencing should be located as shown on the plan maps
for pl acement.

Fencing should be placed in two parallel rows 30-35
feet apart. Posts should be driven two feet into the
ground at 10 foot intervals. Fencing should be fi mly
attached to each post at the top, middle and bottom.
The fences shouldbe anchored with guy wires at 50 foot
intervals. End posts should be anchored in three
directions -at 20 foot intervals. Cover the base of
the fence with a,mat of rye-grass straw (not wheat
straw) 18" wide and 2" deep and cover the straw with
sand.

Timing: Fencing should be placed from November 15 to January 1.

Dunegrass Once the sand fences have filled or substantially
Plantings filled grass should be planted according to
specifications for dunegrass plantingfollowing surface
grading to provide an even surface for planting..
This should generally be done between January 15 and
March 15.

_19-

The foreslope (i.e. in front of the seaward sand
fence) to a width of approximately 35 feet should
be planted at eighteen inch centers.

The crest (between the parallel sand fences)
should be planted at 18 inch centers.

The back portion from the shoreward sand fence
approximately 24 feet should be planted on
18 inch centers.

Other: 1. Fences must be repaired if damaged by erosion or
vandalism.

2. Informational signs.should be placed at public
access points to explain the purpose of sand
fencing projects to encourage public cooperation.

Accessways through sand-fences

Pedestrian or vehicle access through sand fenced areas should be provided
according to the following specifications in locations identified on the
grading plan map.

- The parallel rows of sand fencing should be
dross-fenced at the access to keep pedestrians and
vehicles in the accessway and to capture sand.

- Pedestrian accesses should be four to five feet wide.

- Vehicle accesses should be 10-12 feet wide

- A third sand fence should be placed 10-12 feet seaward
of and parallel to the main sand fences in front of
the access opening. The fence should overlap the
opening by at least five feet on each end.

-20-

Accesses must be oriented directly east-west.

Public access ways should be signed both on the beach
and landward to encourage use and discourage crossing
the sand fence.

Once dune vegetation is well established on the
--stabilized dune the access way should be fenced and
stabilized and a new access established through a
vegetated portion of the dune.

European beachgrass should be used and all other
recommendations for planting should be followed.

-21-

Specifications for Planting European Beachgrassl

Planting stock: The stock to be planted is European Beachgrass
(Ammophilia Arenaria). The source and quality of the
planting stock should be approved by the Contracting
Officer or the authorized representative.

Digging, ...The plants should be thoroughly cleaned by shaking
Stripping and sand and silt from the roots. Dead stalks and trash
Trimming: should be removed from the culms by stripping. The
underground stems should be broken back so that one or
two nodes remain. The grass culms should be sorted
and tied into bundles weighing approximately 10
pounds; tops should be cut back so that the overall
length of the planting stock measures about 20 inches.

Storage: The planting stock should be planted within eight
hours of removal from the nursery areas or heeling-in
beds. The heeling-beds should be a well-drained damp
trench with the roots (nodes) covered to a depth of at
least eight inches. Stock should not be held in
heeling-in-beds for a period exceeding two weeks. The
supply of stock at the planting site must be kept in a
cool shady place or otherwise protected against damage
from excessive drying. Cold storage at 34-38 degrees
farenheit for periods of up to 2 months is also
acceptable.

Transportation
and
Handling: The planting stock should be handled and transported
by any method that does nbt damage the planting stock

or area.

-22-

Planting: 1. The grass is planted in hills with an average of
three live culms per hill but no less than two in
up to 10% of the hills.)

2. The spacing between hills should average 12
inches on the foreslope and 18 inches on the

crest.

3. The grass should be planted to a depth of 12
inches, with sand or silt for cover compacted to
exclude air from the roots (nodes). The top of
the plant should be upright and extend
approximatley eight inches above the ground.

4. No planting should be done on any area until the
moisture is within three inches of the ground
surface. Nor should any planting be done when
the temperature exceeds 60 degress F. or when
freezing conditions prevail.

5. All areas planted should be fertilized with
coarse particle ammonium sulfate commercial
fertilizer, applied at a rate of forty-two pounds
of available nitrogen per acre (one pound per
1000 square feet). Fertilizer should be applied
when the wind is calm and the rain is steady;
irrigation may be substituted for rain. The
fertilizer should be applied at the time directed
by the Contracting Officer of the authorized
representative.

Inspection: 1. Inspections should be made by the Contracting
Officer or his authorized representative. A
representative cross section of not less than 5%
of the planted areas should be inspected to
ensure compliance with the contract requirements.

-23-

2. Nonconformance with any specifications classifies
a plant hill as unsatisfactorily planted. A
tolerance of 5% or five unsatisfactory plant
hills per 100 is satisfactory. However, any
amount over 5% should be applied as an equal
percentage reduction of the acreage planted
(payments being made on the basis of net
acreage). When the deficiencies are 10% or over,
the contractor should be expected to take steps
to correct them.

I Specifications are also applicable to American beachgrass (Ammophila
breviligulata) and Sea Lyme-grass (Elymus mollis).

Adapted from Ternyik, 1979

Secondary Stabilization

Plantings of secondary stabilizing vegetation are appropriate in
well-vegetated backslope and back areas but not in the crest or foreslope.

The following plants are appropriate:

Salal (Gaultheria shallon)
Evergreen Huckleberry (Vaccinium ovatum)
Shore Pine (Pinus contorta)
Purple Beach Pea (Lathyrus japonicus)
Seashore Lupine (Lupinus littoralis)
Tree Lupine (Lupinus arboreas)..

Secondary stabilization should be done in' conformance with the
recommendations provided in Table 2.

-24-

Secondary stabilization should only be done when initial stabilizing
vegetation (i.e. European beachgrass) is well-established.

Method: Secondary plantings should occur directly in existing stands of
beachgrass. Beachgrass should not be destroyed or removed prior
to planting, so that it can continue to stabilize the area as
secondary plants are establishing themselves. Succession should
occur without destruction since beachgrass tends to thin out and
die where it is cut off from sand accretion.

-25-

Crest Grading

Limited grading of sand from crest areas above the 26 foot elevation is
allowed by this plan. These specifications should be followed carefully
to minimize damage to dune vegetation and stability of the foredune. If
done-improperly grading can destroy stabilizing vegetation, cause
unwanted sand accretion on adjacent lots and homes and substantially
increase potential for ocean flood damage.

Timing: Grading should only be done between November I and
March 15. Windblown movement of sand at this time of
the year is minimal.

Preconditions: The crest area to be graded must be more than 4 feet
above the 100 year flood elevation; in most of the
Nedonna area this is the 26 foot elevation (MSL).

Equipment: A bulldozer with size depending upon the extent of the
area to be graded.

Method: The area to be graded should be staked by an engineer
in advance-6f grading so that the operator knows the
limits on the area and the depth of grading to occur.
Depth of cut should not exceed 4 feet.

The management authority should be notified so that a
representative can view the staked area, the grading
operation and the completed grading.

The bulldozer should be access through the jetty
parking lot and travel along the beach. The bulldozer
should avoid transiting across the foreslope. Low
spots in the crest on the lot or adjacent lots (i.e.
below the 26 foot elevation) are the priority location

-26-

for graded material. The management authority should
identify spots on adjacent lots to be filled in its
issuance of a grading permit. The cat operator's
first passes should push sand to fill these low spots
to the 26 foot elevation. (This will result in a
crest 50-75' wide at a uniform 26' height, except in
Subarea E where the crest is 100-125' wide.)

Where the adjacent lots are at the minimum elevation
crest grading can be done in two ways:

(1) A series of short passes pushing sand directly
oceanward from the crest to the foreslope.

(2) One or several passes along the crest of the
foredune with the blade angled so that sand is
deposited on the foreslope.

In either case sand should simply be pushed onto the
foreslope. Where a substanital amount of sand is
placed on the foreslope it should be smoothed out to
create an even slope. If only a small amount of sand
is graded forward the bulldozer should not attempt to
smooth the sand forward on the foreslope.

Tapering: If the crest of adjacent ungraded lots is 4 feet
higher than graded lots the grading should taper the
crest into these areas rather than leave a right angle
cut at the lot line.

Minimum Area: Grading should be done over several lots at a time to
achieve a uniform crest height throughout. However
grading may be done on a lot-by-lot basis provided all
other specifications are met.

-27-

Fertilizing: Areas graded less than 3 feet should be promptly
fertilized per the fertilization recommendations for
Beachgrass plantings. Fertilizer should be applied to
graded sand placed on the crest and foreslope as well.

Planting Areas graded more than 3 feet in height should be
Beachgrass: replanted with European beachgrass at 18" spacing.
Any graded crest area with less than 30% vegetative
cover should also be replanted with European
beachgrass.

Inspection: The Management Authority should inspect the site
before and after grading to confirm that grading and
other measures have been done in compliance with
specifications here.

Permits for grading should be conditioned to require
reestablishment of vegetation on all areas affected by
grading or filling. The Management Authority s hould
inspect the graded area at 1, 3, 6, 9 and 12 months
after grading and recommend remedial measures at those
times. Failure to comply should provide for
Management Authority authorization to reestablish
vegetation at the permittee's expense.

Foreslope Shaping

Foreslope shaping is appropriate in very limited situations to establish
an even slope for maximum accretion of sand and foredune slope growth
shaping should only be done when the present foreslope is so uneven and
hummocky that it significantly impedes growth of the foredune.

Equipment: Lightest possible bulldozers should be used since less
sand will be moved than for crest grading.

-28-

Sl ope: Grading should attempt to establish an even slope at
an angle between to degree slope (between
I to 3 and 1 to 4) depending on the amount of sand
available.

Distribution: Unless sand is placed as a result of approved grading
elsewhere shaping should only re-distribute sand
--presently on the foreslope. Only sand from the,
foreslope should be moved. Grading.of sand from the
crest or the beach onto the foreslope is regulated
separately as grading or beach bulldozing and may be
appropriate to provide sand for grading-if there is a
surplus of sand in these areas.

Minimum Area: Shaping should occur over several lots at a time as
shown on the grading plan map.

Tapering: Shaped areas should be tapered into adjacent unshaped
areas.to avoid creating wind erosion or accretion
problems.

Method: Shaping should move as-little sand,as is possible to
establish an even slope (i.e. top off hummocks). The
operator should make as few passes as possible and
should avoid damaging vegetation on the crest of the
foredune.

Fertilization: Vegetated areas that are not seriously damaged or
buried more than 3 feet of sand should be immediately
fertilized.

Plantings: Unvegetated areas and areas covered by more than 3
feet of sand should be immediately replanted with
European Beachgrass according to planting
specifications.

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.21

MANAGEMENT PLAN
- I

ROCKAWAY/NEDONNA BEACH

BEACH AND DUNE MANAGEMENT PLAN

FOURTH DRAFT

15 FEBRUARY 1986

-2-

FOREDUNE ALTERATIONS

IMPACTS AND MANAGEMENT RECOMMENDATIONS

Introduction 5

Importance of the Foredune 9

Applicability to Other Areas 12

Shoreline Stabilization 15

Jetties. 15

Shorefront Protective Structures 16

Beach/Dune Alteration 23

Foredune Grading 24

Foredune Breaching . 31

Beach Nourishment . 32

Beach Bulldozing 34

Sand Mini ng/Removal . 36

Residential Development 37

Setback Line 40

Minor Structures 42

-3-

Vegetation Management 43

Planting European Beachgrass 44

Mowing Beachgrass 45

Application of Herbicides . 46

Non-Stabilizing Vegetation . 47

Firebreaks 48

Beach Access 50

Public Access o 50

Vehicle Access . 51

Private Access . 52

Other Dune Alterations 54

Motor Vehicle Operation 54

Fires 55

Creek Outlets/Embayments 56

Log Clearing 56

Stream Clearing 58

Embayment Stabilization 59

-4-

A endices

A. Definitions

B. State Laws and Administrative Rules

- Statewide Planning Goal 18 (Land Conservation and Development)

- Ocean Shore Rules (Parks Division)

- Removal-Fill Rules (Division of State Lands)

C. Revetment/Rip-Rap Specifications

D. References

-5-

Introduction

In order to set the stage for this plan the nature of hazardous
conditions at Rockaway and Nedonna Beach must be recognized. Similarly
it must be understood that without a sound foredune management plan the
risk of severe damage from ocean storms is greatly increased.

Man, since time began, has had a love affair with the sea and its
beauty. However, as in other situations, love can obscure good sense
about inherently dangerous situations. This is very apparent with most
of the beach front homes and commercial buildings in the Nedonna Beach/
Rockaway area. With few exceptions, all structures were built on or near
what is now classified as an unstable foredune. (These areas are subject
to wave overtopping, ocean flooding, sand erosion and deposition.) One
only needs consider historical erosion events to realize the gravity of
the problem.

In Tillamook County, logs were washed a block behind the oceanfront
road at Manzanita. Nehalem faced its worst flooding since 1933 with
nearly every business building in the main block being flooded.
Waves carried logs over the sand dune and blocked the parking lot at
the north end of Nedonna Beach, and damaged homes at Manhattan
Beach. At Rockaway, the surge sent logs over the railroad tracks and
onto U.S. Highway 101 damaging several houses, plugging the creek
outlet and causing local flooding. Logs damaged houses at Twin Rocks
and were carried accross the railroad tracks to the highway there.
At Barview in Garibaldi, logs washed into Highway 101. Flooding
occurred near the Miami River and some Highway flooding occurred near
Tillamook. Logs were washed nearly two blocks back from the beach at
Cape Meares, and logs damaged homes, seawalls, and riprap at
Netarts. Picnic tables were washed away at the county park at
Sandlake, and logs were strewn across the highway at Tierra Del Mar.
Although many houses and buildings in Pacific City and Woods were
surrounded by water, no damage was reported. At Camp Winema, logs
were washed high above the beach, but no damage was done to the
buildings; and at Neskowin, logs damaged beachfront houses.

-6-

Historically, one of the greatest ocean floodings in Tillamook and
Clatsop Counties occurred on January 3, 1939, when high tides and
windswept waters caused extensive damage over much of coastal
Oregon. The sandspits at Bayocean and Neskowin Ridge were breached
in several places and surf-swept logs damaged dozens of beachfront
houses at Twin Rocks, Manhattan Beach, Tierra del Mar and other
communities. South of Barview, 300 feet of Southern Pacific Railway
track was-carried inland over Highway 101. Waves splashed completely
over Twin Rocks, one-half mile offshore from the community of Cape
Meares. In calm weather, Twin Rocks and Pyramid Rock stand 80 and
100 feet, respectively, above mean sea level." (Environmental
Geology of the Coastal Region of Tillamook and Clatsop Counties,
Oregon, 1972, page 103).

In addition, several serious localized erosion events have taken place at
different times, usually related to influence at creek outlet embayments
or rip-current erosion points, In recent years, deterioration of the
Nehalem South Jetty coupled with a rip-current caused severe erosion on
the north end of Nedonna Beach in 1978.

Continuous patterns of erosion cycles described in the technical report
and shown on Technical report maps clearly indicate continual wave
erosion problems. In addition, the major storm erosion events of 1967
and 1939 indicate probability of future storm-induced erosion, flooding,
and sand deposition damage in the future.

Given this set of facts, it is imperative that appropriate measures be
taken as soon as possible to strengthen recognized natural storm wave
defense systems. In numerous other parts of the world, there is a clear
recognition of the protective nature of the foredune areas as a buffer
zone against attack by sea. The U.S. AroW Corps of Engineers reports:

"While the sloping beach and beach berm are the outer line of defense
to absorb most of the wave energy, dunes are the last zone of defense

-7-

in absorbing the energy of storm waves that overtop the berm.
Although dunes erode during severe storms, they are often substantial
enough to afford complete protection to the land behind them. Even
when breached by waves of a severe storm, dunes may gradually rebuild
naturally to provide protection during future storms. Continuing
encroachment on the sea with manmade development has often taken
place without proper regard for the protection provided by dunes.
Large dune areas have been leveled to make way for real estate
developments, or have been lowered to permit easy access to the
beach. Where there is inadequate dune or similar protection against
storm waves, the storm waters may wash over low lying land, moving or
destroying everything in their path.

"Gently sloping shores, whether beaches or wetlands, are natural
defenses against erosion. The slopes of the foredune form a first
line of defense, dissipating the energy of breaking waves. The berm
prevents normal high water from reaching the backshore. Dunes and
their vegetation offer protection against storm-driven high water and
also provide a reservoir of sand for rebuilding the beach. Wise
management of shore areas should include protection of these natural
defenses where they exist;

"Although erosion is essentially caused by natural shoreline
processes, its rate and severity can be intensified by human
activity. The shoreline and the water are highly valued for
recreational activities, but heavy use and development may accelerate
erosion. Those who build 'permanent' homes and recreation facilities
often ignore the fact that the shoreline is being constantly built up
and worn away again. They may also fail to take into account the
periodic and unpredictable affects of storms." (Shore Protection
Manual I, U.S. Army Corps of Engineers, 1975.)

In Europe, where some dune areas have been intensively managed for years,
foredunes referred to as barrier dunes are given prime consideration
because of their protective nature.

-8-

"On sandy coasts, the ridges of sand dunes are often the natural
protective structures against flooding the low-lying land, the
villages or towns during storm tides. The strength and resistance of
these barrier dunes., which are found just landward of the beach, is
to be estimated in consideration of the extent and the height of the
dunes as well as of the width, the height and the stability of the
beach. As in many cases on the beach in consequence of altering sea
and wave conditions and different littoral drift, the supposition for
erosion or aggradation varies, dunes and beaches have to be observed
constantly. The beginning of a considerable erosion of the dunes has
to be seen in connection with the development of the beach. A
systematical research of the reasons and the further development has
to be done. The research has to include the total
dune-beach-profile." (Erchinger, Heie. Protection of Sandy Coasts in
1974. Dependence of the Dune-Beach-Type)

In the section of West Germany referred to above, annual erosion of
foredune foreslopes is repaired each season. This same abstract by
Erchinger speaks to repair of eroded foreslope in the Netherlands on the
Isle of Tuxel by use of bulldozers, then replanting. Only on the West
Coast of the United States do-plans ignore or discourage foredune
modification or restoration. However, on the East Coast and in Europe,
total management plans are developed, rigid ordinances and rules protect
the natural and enhanced protective nature of the foredunes.

Through grading the foredune for ocean viewing caused this tudy to take
place, the ultimate more valuable result will be strengthening the
protective nature of the foredune by informed management.

The beach and foredune are critical to protecting backshore areas from
ocean flooding. Even so, foredunes are fragile landforms, easily damaged
or destroyed by human use or development. Extensive residential
development along the Rockaway Beach/Nedonna Beach shoreline and
associated activities and uses there have altered the shape and size of
the foredune. The result is that the foredune's flood protection ability
has been reduced.

-9-

This report assesses the effects of most of the uses and activities which
either have or could affect the stability of the foredune at Rockaway
Beach and Nedonna Beach. The report recommends limits on how, when and
where these activities should be conducted to minimize possible harm to
the foredune.

The report's recommendations will need to be carried out by local
governments, state agencies and property owners. Tillamook County and
the City of Rockaway Beach play a major role through their review of
permits for building and development. The State Parks Division and the
Division of State Lands should implement relevant recommendations through
their permits for beachfront development and alterations. Finally,
property owners have a critical role to play since many recommendations
deal with the day-to-day use of the foredune, such as beach access and
maintenance of beachgrass.

If this report's recommendations are carried out, then the foredune
should be strengthed and the potential for flood damage reduced. This
will be done by improving the ability of natural processes to build and
maintain the foredune. However, it must be stressed that these measures
will not guarantee freedom from ocean flooding or erosion. Foredunes are
inherently unstable areas and the dynamics of ocean flooding and erosion
in foredunes are simply too unpredictable to guarantee that ocean
flooding or damage will not occur. The recommended measures will simply
do what is possible to enhance the natural protection provided by the
foredune. The potential for catastrophic flooding and damage should be
an understood risk of owning oceanfront property.

Importance Of The Foredune

Maintenance and enhancement of the foredune and natural beach-dune
processes is'critical because of the protection this system provides
against ocean flooding. If the foredune is damaged or the natural system

_10-

disrupted, the potential for ocean flood and erosion damage to oceanfront
development is increased. The beach and foredune respond to ocean
flooding in a predictable way:

"As the dune is attacked by storm waves, eroded
material is carried out and deposited offshore, where
it alters the underwater configuration of the beach.
Accumulating sand decreases the offshore beach slope
(makes it more nearly horizontal), thereby presenting a
broader bottom surface to storm wave action. This
surface absorbs or dissipates through friction an
increasingly large amount of destructive wave energy
that would otherwise be focused on the shoreline behind
the barrier.

The capacity of the dune for absorbing and moderating
wave energy is not dependent on any ability to
completely prevent breaching or flooding. Even in the
process of being inundated and destroyed, as many are
by hurricanes, the dune moderates back beach storm
damage. The effect is-less pronounced for low dunes,
but nevertheless persists. Since storm resistance
increases with dune height, however, all human uses of
the barrier that devegetate, erode, or lower the dune
expose the shoreline behind the barrier to increased
storm damage." (Clark, 1977, 267).

bulk - the more sand in a foredune the more wave energy will
be required to penetrate the dune.

height - A higher dune can withstand overtopping or breaching
that would flood back areas.

shape A smooth low sloping foreslope will direct waves up
the dune dissipating some of the wave energy. If the
foreslope is steep or vertical, more erosion will

occur.

vegetation- A well vegetated foredune will hold together better in
the face of attacking waves. Unvegetated sand will
break up more quickly by waves.

location A foredune fronted by a wide beach will receive less
wave attack compared to a foredune or a narrow beach.

Managing and enhancing the foredune to provide flood protection is not a
new technique. In Europe, foredunes, or barrier dunes, have been managed
for years to provide flood protection for inland area.

"The Dutch rely on the natural sand dunes as their
primary (or outer) defense against the sea, and on
dikes, which are actually substitute dunes, for their
secondary or inner defense ring. The manner of
construction and maintenance of these defenses is such
as to ensure their natural state, which is
sufficiently flexible and resilient to,absorb all but
the severest forces of wind and waves.

The key to Dutch success in maintaining their coastal
protection lies in the management of their dune and
dike system. Although intensive recreational usage is
permitted on the beach, absolutely no passage,
breaching, or building on the dunes is permitted.
Limited recreation and building are permitted in the
trough between the primary and the secondary dune (or
dike). The backdune area is recognized as the most
suitable for development. This strateg y of
encouraging the coastline to persist in its natural

-12-

state serves to maintain the optimum protection
afforded by nature." (Joseph M. Colonell, in Clark,
1977, p. 571)

Similarly in West Germany the foredune has been managed to provide flood
protection. In both cases much more information about the dune and
nearshore bar -- is-available. For example, foredunes in some areas have
beenImanaged for over three hundred years while in other areas the
offshore bars have been monitored and structurally diverted to enhance
beach stability.

APPLICABILITY TO OTHER AREAS

While this study has focused on the Nedonna Beach/Rockaway Beach
shoreline many of the managment recommendations can be applied to other
developed foredunes on the Oregon Coast. (These recommendations should
be limited to foredunes where extensive development has already
,occurred. Through Statewide Planning Goal 18 Oregon has prohibited
building on undeveloped foredunes because of the inherent instability of
these areas and the potential-for ocean flooding. This prohibition is
appropriate and should continue.)

Overall, management of foredune alterations should be viewed as necessary
in developed foredunes. Whether well advised or not foredunes have been
developed for long-term residential use. In turn the state, through its
coastal planning requirements has allowed building on developed foredunes
to continue. The management philosophy in these areas now should be to
provide as much protection as is possible without interfering with
natural processes or' harming adjacent areas. The management
recommendations provided here implement this philosophy: Activities
which would harm the foredune or interfere with natural accretion or
erosion of sand will be controlled; steps to strengthen the foredune's
ability to capture and stabilize sand and withstand flooding will be
encouraged.

The same philosophy and recommendations are generally applicable to other
developed foredune areas. However, there are clearly some limitations to
applying these recommendations to other developed foredune areas. Before
applying these recommendations in other areas local governments and
relevant state agencies should consider and evaluate the following
factors:

The Rockaway-Nedonna Beach shoreline is extensively
developed and does not appear to be subject to long-term
erosion at this time. If the shoreline was receding and
were less developed, prohibition of further development and
relocation of homes would be an appropriate alternative.

While there are many steps individual property owners can
take to strengthen the dune any major alterations such as
grading must be conducted as part of an areawide plan,
supported by appropriate technical analysis. Major
alterations for arbitrarily small streches of shoreline can
easily ignore nearby4features which could undermine the
foredune (such as a major breach) and are inappropriate.

The measures recommended in this report, while appropriate
to most developed foredune areas, are based on the
particular circumstances in Rockaway and Nedonna Beach.
Peculiarities of other areas should be considered through
professional review prior to applying these
recommendations. For example, erosion at the Alsea and
Necanicum River Spits over the last year demonstrates the
special hazard of development on foredunes near
unstabilized river mouths.

Crest grading is appropriate only where foredunes are well
established:

-14-

where the foredune is developed and the shoreline
demonstrates long-term stability with no known
reduction in shoreline sand supply.

where the foredune is well vegetated

where, per Goal 18, the foredune is mostly more
-than 4 feet above the 100-year flood level

-15-

SHORELINE STABILIZATION

The major effect of human development along the ocean shore is to attempt
to establish and maintain the shoreline at a particular location. A
variety of structures have been constructed to promote accretion and
prevent erosion so as to maintain a particular shoreline. Two types of
structures hav e been critical to protecting the shoreline in the study
area -- jetties at Nehalem and Tillamook Bays and, to a much lesser
extent, rip-rap or revetments in front of several oceanfront homes,
buildings and roads. This section assesses the impacts of these
"improvements."

Jetties

The Nehalem Bay jetties on the North and, to a lesser extent, the
Tillamook Bay jetties on the South have had a profound effect on the
shoreline in the study area. Jetties are placed to stabilize a river
mouth at a particular location as it enters the ocean. Without jetties,
river mouths tend to migrate in response to littoral movement of sand and
sandbars along shore.

The rehabilitated Nehalem Bay jetties have in concert with the 1982-83
El Nino resulted in substantial accretion at the south jetty. (There was
about 150 feet of accretion to the beach from 1978 to 1984). The
original jetties experienced serious degradation within twenty years of
their construction. (Corps of Engineers, Jetty EIS, 1980 p. 1-1). The
Corps expects the rehabilitated jetties to be effective for at least 50
years since they are better constructed with harder rock and a more
substantial core. Nonetheless, the condition of the jetties should be
monitered.

Maintenance of the jetties is permitted under the Statewide Planning
Goals, the County's Comprehensive Plan, and the State Removal-Fill Law.
It should be noted that future maintenance of the jetties is not

-16-

guaranteed. The recent rehabilitation was done as a result of special
congressional appropriation. Changes in federal policy on funding
navigation improvements, will probably require local cost-sharing which
may make future maintenance of the jetty an expensive if not uneconomical
proposition.

Management Rec ommendations:

1. The Nehalem Bay jetties, and the South Jetty in particular, should be
maintained in order to keep the shoreline at Nedonna Beach at or near
its present location.

2 The Corps of Engineers and the Port of Nehalem should periodically
monitor the condition of the jetties. Additional research is needed
to assess changes in the adjacent shoreline, and nearshore sand bars
and to evaluate the effect of the jetties in blocking littoral sand
movement.

3. The undeveloped shoreland area behind the jetties is dependent on the
continued maintenance of the jetties and should not be developed
- unless a guarantee is provided that the jetties will be maintained
for the life of the development.

Shorefront Protection Structures

Shoreline erosion is a recurring problem in the study area.
Rip-currents, El Nino events, and severe ocean storms have caused erosion
which has threatened oceanfront homes. In addition, experience in other
areas and the projected 100-year storm suggest that the shoreline
throughout the study area will be subject to erosion. The most likely
erosion events will be periodic episodes of erosion which affect short
stretches (200' to 1000') of shoreline (Komar). Such erosion is likely
to occur at rip-current embayments during winter storms. However, major
erosion is still possible throughout the study area as part of a major
prolonged ocean storm event. (Such as the January 1939 storm which had a
recurrence interval of 75 years.)

-17-

While the beach and foredune provide some protection their grade and mass
may not be completely sufficient to protect existing development from
damage. Where the natural system is inadequate some form of structural
protection will be needed to protect exsisting development.
Unfortunately, the need for protective structures for particular areas
will only be apparent, when development is threatened by an ongoing or
imminent erosion episode. For example, much of north Nedonna Beach was
rip-rapped in 1918 when a series of storms eroded the shoreline there
that coincided with a beach narrowed by rip currents.

Structural shoreline stabilization can include a variety of constructed
improvements or alterations intended to fix the shoreline at a particular
location (i.eJ. to prevent further landward movement of the beach).
Stabilization is usually done to protect existing homes from on-going or
imminent ocean wave erosion. Nationally, a wide variety of devices
placed on the shoreline, on the beach or in the nearshore ocea-n are used
to stabilize the shore. The most common means of stabilization on the
Oregon Coast are revetments made.of large stone (aka rip-rap). The State
has adopted several laws and rules which limit the construction of
shoreline stabilization structures and devices because of the adverse
effects that they can have on-the beach and neighboring properties.

Effects of Shoreline Stabilization Structures

This discussion only addresses structures constructed at or landward of
the shoreline since these are the only types commonly used or allowed in
Oregon. Structures located on the beach or in the water, such as groins
and breakwaters, are generally considered inappropriate for this
shoreline and inconsistent with the management of objective of preserving
the natural shoreline processes as much as possible.

The purpose of most stabilization structures is to prevent ocean wave
erosion of the shoreline. Properly located and constructed structures
have this effect. They can also have several other important effects on
the beach and the sand supply system. Structures placed on the shoreline

-18-

include seawalls, or bulkheads, as well as revetments. Bulkheads and
seawalls have some common effects on beach sand supply. The most
immediate of these is that the foredune behind the wall is cut off as a
source of sand to the beach. If a large stretch of shoreline is armored
the effect is to reduce the supply of sand available to the beach and for
accretion to nearby areas.

The ocean wave energy that would be absorbed through dune erosion is
instead partly absorbed and partly reflected off of the shoreline
structure. Reflected wave energy increases beach erosion.
Unfortunately, seawalls (including bulkheads and revetments) commonly
accelerate the loss of sand as the wall deflects wave forces downward
into the beach deposit. This causes the sand to erode away seaward of
the footing and the beach to dimish or dissappear. Often the seawall is
undermined and collapses. (Clark, 1977, p. 323). Over-time these two
effects--cutting off sand supply and reflecting wave energy to the
beach--can cause dramatic erosion of the beach.

The extent of beach loss over time is difficult to predict. Experience
at other shorelines around the country and the world suggest, such
structures are an important factor in loss of beaches. In many areas
much more expensive solutions, such as ongoing beach nourishment, have
been required to offset the effects of erosion.

The effect of particular types of structures varies. Vertical seawalls
and bulkheads reflect most of the wave energy back onto the beach
perpendicular to the structure. Properly sloped riprap revetments also
deflect some wave energy upward rather than back onto the beach.

Structural solutions should only be employed when it is clear that
natural processes will not provide adequate protection, and that
alterations should be the minimum necessary to correct the problem.

"...extensive areas of the coast are already occupied and
must somehow be maintained safely until setbacks and

_19-

other protective land-use plans can be implemented. Yet
even these systems.should be allowed to remain as close
to their natural dynamic states as possible." (Clark,
1977, 323)

"The natural forces at work are immense, and the power of
man to hold the beach at the higher than natural angle of
repose to protect property is limited. Structural
solutions are often ineffective and usually only
temporary.

There are two possible solutions that should be
considered together. First, permanent development should
be placed well inland of the active part of the shore,
including receding shores that would be expected to
become active in the future. Second, positive action
should be taken both to prevent the removal of sand from
any storage element and to prevent blocking the free
transport of sand from any one storage element into the
active part of the system." (Clark, 1977, 322).

Oregon has adopted three major sets of laws and rules controlling or
prohibiting shoreline protective structures. They include:

- The Ocean Shores Law, commonly known as the Beach Bill
(ORS 390.605-390.770). It sets in statute a public easement to the
beach up to the high tide line. Any interference with this public
easement is subject to state regulation. Placement of structures
requires permits from the State Parks Division which administers
this law.

- The Removal-F.ill Law (ORS 541.605-.695, 541.990), regulates removal
or filling within the bed and banks of waters of the state. On the
ocean beach this authority extends to the upland vegetation line.
Filling includes placement of shorefront protective structures.

-20-

- Statewide Planning Goals 17 and 18 (the Coastal Shorelands Goal and
the Beaches and Dunes Goal, respectively) set specific planning
requirements for siting of shoreline protective structures.

Goal 18 prohibits beachfront protective structures in areas that were not
built or physically improved for development on January 1, 1977.
Specifically, it requires:

11(5) Permits for beachfront protective structures
shall be issued only where development existed
on January 1, 1977. Local comprehensive plans
shall identify areas where development existed
on January 1, 1977. For the purposes of this
requirement and implementation Requirement 7
'development' means houses, commercial and
industrial buildings, and vacant subdivision
lots which are physically improved through
construction of streets and provision of
utilities to the lot and includes aras where
an exception to (2) above has been approved."

With only a few exceptions, most of the shoreline in the study area is
qualified for revetments under Goal 18 when such structures are shown to
be needed.

The remaining requirements of Goal 18 along with Goal 17, the
Removal-Fill Law, and the Beach Bill control how and where shoreline
structures can be constructed. Both DSL and MOT require permits for
most shoreline structures. DSL's jurisdiction extends to mean higher
high water (mhhw) or the vegetation line, whichever is higher. NOT
permits are required for structures located seaward of the surveyed beach
zone line. The Statewide Goal requirements are applied either by these
agencies during their review or through a separate local review. The
specific requirements of these laws and rules are provided in Appendix

-21-

These requirements limit shoreline protection to areas which were
developed on January 1, 1977 when they are threatened and then only where
no other method of erosion control will work. In addition, protective
measures must be properly installed and adequate to protect the property
without causing increased erosion or flooding on adjacent properties.
These requirements provide for the right of upland property owners to
protect their homes or property while minimizing adverse impacts of such
structures on adjacent properties and the public beach.

The tendency of revetments to increase erosion on surrounding unprotected
properties is an important consideration in deciding at what point a
foredune should be riprapped. Generally, erosion events attack a stretch
of shoreline uniformly--a group of lots will all experience roughly the
same amount of erosion. In these situations riprap should be placed in a
continuous line parallel to the retreating foredune. This way the
structure does not deflect wave energy to adjacent lots.

Management Recommendations

1. Because of cost and potential effects on shoreline stability and
adjacent properties structural shoreline protection should only be
permitted when erosion clearly threatens existing development.

2. Revetments should be located as far landward (i.e., close to existing
dwellings) as possible in order to avoid unnecessary construction of
structures and to minimize interference with natural sand movement as
part of the erosion and accretion process.

3. At this time riprap appears to be the only appropriate means of
structural shoreline protection in the study area. Breakwaters and
groins are inappropriate because they interfere with natural movement
of sand along the beach and in nearshore bars. Seawalls or bulkheads
are generally inappropriate because they may reflect wave energy
promoting beach erosion inconsistent with the objectives of this

-22-

plan. Riprap is appropriate because, where it is properly designed
and constructed, it provides shoreline protecion with minimum
disruption to natural processes.

4. Revetments shall be designed and constructed to meet at least the
minimum specifications set forth in Appendix C.

-23-

BEACH/DUNE ALTERATION

Beaches and dunes have been intentionally reshaped or altered b y man for
a variety of purposes. In some areas of the coast, beach sand has been
excavated for construction material or fill. The most common alteration
in the Nedonna-Rockaway area has been grading of the foredune. Crest
grading has beendone for a variety of purposes including site
preparation, view maintenance and to remove sand build-up around
structures. Other alterations that can or have occurred include: sand
placement, dune breaching, beach pushing, and beach nourishment.

"In most cases, removal or serious alteration to the protective
foredune will mean that substantial sand deposition damage will
result to man's existing developments and public works, lakes,
wildlife areas, agricultural land and forests. In other words, the
active foredunes or those foredunes conditionally stable provide a
protective wind barrier to what exists landward of them and the
removal of the barrier will increase wind erosion and sand deposition
in the landward area." (Soil Conservation Service, Beaches and Dunes
of the Oregon Coast, p. 137).

While foredune alteration is discouraged it is clear that some
alterations can be done without destabilizing the foredune. In fact,
some of the foredune is in such poor condition that additional alteration
is needed to strengthen it. For example, the foredune in several parts
of the study area is low, narrow or discontinuous. These parts of the
foredune provide an uneven barrier to windblown sand and ocean flooding.
Measures to increase the foredunes base width, foreslope angle and
vegetative cover are appropriate in such areas. However specific
corrective measures should only be done as part of a management plan for
a larger area.

Alterations to beaches and dunes are regulated at the local, state and
the federal level. Tillamook County and the City of Rockaway Beach
administer zoning and building requirements which implement local

-24-

requirements. These local permits are also used to carry out state
planning requirements (LCDC Goals) and federal floodplain management
requirements. The Parks Division regulates any alteration oceanward of
the surveyed beach zone line. The Division of State Lands exercises the
state's jurisdiction over beds and banks of public waters through the
Removal-Fill law, which covers up to the line of nonaquatic vegetation or
the highest hi gh tide. Finally, the Army Corps of Engineers has federal
jurisdiction comparable to that exercised by DSL.

Foredune Grading

As noted above, foredune grading is the most common alteration to the
foredune in the study area. Grading of foredune crest at Nedonna Beach
has been done to maintain ocean views of oceanfront homes. With few
exceptions grading has not seriously damaged the integrity of the
foredune. Damage from grading has been limited for several reasons:

- usually only a small amount of sand is moved, the top 1-3 feet of the
foredune is graded; the resulting foredune height is typically 1-2
feet above the 100 year flood level.

- sand is pushed forward onto the foreslope rather than pushed back or
removed altogether;

- stabilizing vegetation (beachgrass) while damaged is not destroyed or
removed, allowing it to reestablish-and restabilize the lowered
foredune; and,

- grading seems to have been done at times of the year when wind
transport of sand has been limited.

In some places, particularly the northern portions of Nedonna Beach,
grading and other alterations have either destroyed the foredune or
prevented it from becoming well established. The pattern of alteration
appears to have been more serious in these cases:

-25-

deeper cuts (i.e., more than 3 feet) have been made in the foredune.

vegetation has been destroyed or reduced to the point that
significant amounts of sand are blown inland rather than captured in
the foredune.

grading ha-s been done frequently so that vegetation has not been able
to re-establish the foredune.

The foredune at north Nedonna Beach is lower and narrower than the area
to the south for two other reasons. First, a 1500' area here experienced
severe erosion requiring riprap in 1978. The area has not fully
recovered (recovery has also been hampered by improper grading). Second,
the foredune next to the jetty parking lot has been breached by emergency
vehicle access across the foredune.

The most serious effect of grading in Nedonna Beach is increased
potential for floodwater overwash in places where the foredune has been
lowered to or below the-100-year flood level. The predicted heights for
100-year flooding in the Nedonna Beach area is 22 feet (HUD, Flood
Insurance Rate Map, 1978) while crest heights run from 17 to 30 feet,
with several graded sites at or below the 100-year flood level. Lowering
of dunes has created an opportunity for storm waves to overtop the
foredune resulting in more extensive flooding.

Not all grading increases potential flood damage. In fact some reshaping
and movement of sand may actually increase overall protection from
flooding (up to the 100-year flood level). For example, the-northern
portion of Nedonna Beach is characterized by a discontinuous foredune and
hummocks, both of varying width and height. The hummocks are probably
less effective than a uniform vegetated slope in blocking windblown sand
and dissipating ocean wave energy. Foredune management including
grading, shaping, and revegetation would increase protection. The
establishment of optimum orientation, slope and guan vegetative cover
will lead to self maintaining foredune.

-26-

Foredune grading is conditionally allowed by Statewide Planning Goal 18
(Beaches and Dunes). Grading is also regulated by local floodplain
ordinances and requires permits from DSL or Parks if the beach is
affected by grading. Goal 18 requires a management plan for a beach and
dune area to show the feasibility of grading and set limits on how and
where grading may occur. Specifically, the Goal requires:

"Grading or sand movement necessary to maintain views or
to prevent sand inundation may be allowed for structures
in foredune areas only if the area is comm itted to
development and only as part of an overall plan for
managing foredune grading. A foredune grading plan shall
include the following elements based on consideration of
factors affecting the stability of the shoreline to be
managed including sources of sand, ocean flooding, and
patterns of accretion and erosion (including wind
erosion), and effects of beachfront protective structures
and jetties. The plan shall:

a. Cover an entire beach and foredune area separated
from other areas by natural barriers, such as
rivers or large streams. Such plans should also
cover low-lying back areas subject to flooding if
the foredune fails.

b. Specify minimum foredune base, width, foreslope
angle, crest width and height goals. The minimum
height for flood protection under Statewide
Planning Goal 18 is 4 feet above the 100-year flood
elevation;

C. Identify and set priorities for low and narrow dune
areas which need to be built up;

-27-

d. Prescribe standards for redistribution of sand and
temporary and permanent stabilization measures
including the timing of these activities; and

e. Prohibit removal of sand from the beach-foredune
system."

This plan and the recommendations provided below are intended to
implement and satisfy these requirements.

Several factors led LCDC to require that foredunes be maintained at an
elevation higher than the 100-year flood level. Basically LCDC
stipulated a higher elevation to account for uncertainty in the
methodology in calculating flood heights and to provide an additional
safety factor against potential flood damage. FEMA and FIA 100-year
velocity ocean flooding levels are a statistical estimate. FEMA
(formerly FIA) use historic ocean storm conditions, tidal information,
and tsunami information to calculate an ocean storm which has a 1% chance
of occurring in any given year. This is a 100-year storm or flood
event. It is the basis for mapping floodplains and regulating floodplain
development throughout the country. However, there are several
limitations to using this elevation as a minimum height for foredune
elevation:

1. The methodology does not appear to account for foredune erosion,
especially during storm events. FEMA's projections of ocean flooding
for particular areas are based on offshore and nearshore bathymetry
and onshore topography. This information is used to calculate wave
direction and wave run up patterns on the beach, and ultimately the
height of ocean flooding on a particular stretch of beach. The
calculations assume that the slope and elevation of offshore and
onshore features are relatively fixed. FEMA does not appear to take
into consideration changes in the offshore underwater sandbars
protective nature in dissipating wave energy. The changes or
migration of sandbars has not been mapped here or anywhere else on

-28-

the Oregon Coast. The importance of these underwater sandbars should
be appreciated: They provide the first line of defense against sea
waves and provide a continuous sand supply to the beach system.
While this is true for more resistant landforms, like terrace cliffs
or basalt shorelines, it is not true for dunes. Over time, dunes
accrete and erode in ways that alter flooding patterns and to some
extent may alter flood heights. Foredunes also erode away as they
absorb th-e energy of ocean storm waves striking them. The result is
that some of a series of waves occurring during a 100-year storm may
penetrate beyond the 100-year velocity flooding areas mapped.

2. Floodwaters projected by FEMA will top the 100-year velocity flood
level. FEMA draws the limit of velocity flooding at the elevation
where it calculates that waves are breaking one foot above the crest
of the foredune. In these shallow flooding areas there is still wave
damage and erosion, although wave energy is much reduced.

3. FEMA's methodology for calculating flood levels in oceanfront areas
is less accurate than in riverine situations. 100-year flood
projections for riverine areas are based on much better information
about factors affecting fl ooding. Rainfall, basin capacity, and
other factors determining flood heights are much more accurately
measured. Offshore bathymetry changes over time and is not as
accurately measured as river channels. Also the magnitude of
potential storm events (and the factors that cause them) are not as
well understood in ocean settings. The result is there is less
confidence in FEMA's estimates of ocean flood heights.

4. Recent flood events suggest FEMA has underestimated the severity of
the 100-year flood event.

FEMA's calculation of the 100-year flood event implies a certain
likelihood of lesser flood events (i.e. 10 and 50-year storms).
Researchers advising LCDC observed that the frequency of severe
storms and flooding over the last 10-15 years suggest the 100-year
event is more severe than that estimated by FEMA.

-29-

These considerations were discussed with FEMA regional staff and the
authors of FEMA's flood study for the Rockaway and Nedonna areas prior to
establishing the four foot plus elevation. Overall, LCDC concluded that
some additional height should be added to provide a safety factor.
LCDC's selection of four feet was influenced by the fact that levee
structures are typically built two to four feet above expected flood
levels.

Several property owners and others have questioned the four foot plus
figure selected by LCDC. Further study of ocean flooding in foredune
areas is needed. As noted previously, dune height is one of several
factors which determine the foredunes ability to withstand flooding.
Maximum flood protection requires a foredune with a wide base, and a
gentle foreslope, as well as a particular height. The Commission can
consider any new evidence on these factors when it reviews application of
this goal requirement in 1987.

Management Recommendations

1. Limited grading of dune crests which are more than four feet above
the 100-year flood elevation is appropriate and permissible under
Statewide Planning Goal 18. Excavation of lower portions of the
foredune is not permitted by the goal. Grading may not lower the
foredune crest below the 100-year flood plus four foot elevation (per
Statewide Planning Goal 18). Applications for grading permits should
show existing and proposed elevations including the area for
placement of graded sand and the existing and proposed slopes.

2. Limited surface grading of some foreslope areas should be done to
encourage growth of a foredune that is more uniform in height and
width and thus more effective at both stabilizing windblown sand and
withstanding ocean flooding and wave erosion. This type of grading
is appropriate where the foreslope is characterized by a series of
hummocks or small discontinuous dune ridges. Grading of foreslopes
is

-30-

should be carefully blended into adjacent foreslope and crest areas.
Also grading should only reshape the foreslope. (This action may
require ODOT or DSL permits.)

3. Grading of foreslope areas should only be allowed when c
has sufficient vegetation to prevent sand intrusion to back areas.

4. Sand graded from foredune crests should be placed according to the
following priority, from highest to lowest:

a. inlow spots in the crest area of the foredune on the lot and
adjacent lots;

b. in low spots in the foreslope of the lot, when placement results
in a foreslope of more uniform height, smoothness, and slope;

C. in foreslope areas on adjacent lots to increase dune volume;

d. Surface grading of hummocks on the for6slope should be done to
provide an even foreslope to promote even accretion of sand.
(This will require revegetation to assure even growth.)

Material should only be placed in a lower priority location if a
higher priority location is not available. No graded material should
be placed landward of the crest.

5. The area and amount of grading need to be strictly limited so that
large areas of the dune are not destabilized at one time. An
areawide grading plan for Nedonna Beach specifies where and how
grading may occur.

6. Graded areas must be promptly restabilized by appropriate measures
including temporary stabilization, fertilization and planting of
European beachgrass.

-31-

7. FEMA should review its methodology for calculating ocean flood
elevations in general and the response of foredunes to ocean flooding
in particular. This should include reassessment of potential flood
elevations in the study area on a regular basis. LCDC should
consider this information when it evaluates the Goal provision for
foredune grading.

Foredune Breaching

Foredune breaching is the intentional or unintentional creation of a gap
in a foredune. Breaching is usually done on a temporary basis in an
emergency situation such as to allow floodwaters to escape from backdune
or inland areas or to conduct salvage operations on the beach. Breaches
allow sand which would otherwise be captured in the foredune to be blown
inland. Inland structures can be damaged or inundated by inland movement
of sand through a breach. Breaching can occur inadvertently when a
foredune is graded or when a revetment is installed. In either case, the
effect of a breach is to allow windblown sand or floodwater that would
otherwise be blocked by the foredune to pass through.

Temporary breaching of the foredune to allow backed up floodwaters to
escape from inland areas has been effective. When the foredune is
promptly restored this type of breaching appears to have minimal effect,
on foredune stability. Statewide Planning Goal 18 (Implementation
Requirement 6) allows temporary breaches in emergency situations such as
relief of backed up floodwater. Goal 18 also allows foredune breaching
for replenishment of sand supply to interdune areas. This provision was
intended for parts of the Coast with undeveloped foredunes fronting large
open large dune fields such as those at the Oregon Dunes National
Recreation Area. However, such dunes do not exist in or near the study
area. Breaching for this purpose in the study area would reduce sand
supply in the beach and foredune which is needed to protect existing
development from ocean flooding.

-32-

Management Recommendations

1. Breaching should only be permitted where it is necessary to alleviate
a clear and immediate emergency situation, such as drainage of flood
waters from low-lying back dune areas or for salvage operations.

2. Breaching should only be allowed if it is clear that it is not
reasonable to alleviate the emergency in some other way. For
example, directing floodwaters through an existing stream outlet.

3. Where breaches are permitted or occur illegally the person or
organization causing the breach shall take steps to assure that
minimal erosion to the beach and dune occurs as part of the breach,
including: (1) temporary placement of riprap in the breach, if
necessary; and (2) and that the breach is restored to its
pre-existing contours including planting of vegetation as soon as
feasible after the breach has occurred but no later than ten months
after the breach has been accomplished. Temporary stabilization
measures, such as the placement of straw mats or sand fences, shall
be taken if the area is considered subject to erosion prior to the
planting season for beach-grass.

4. Breaching of foredunes to provide sand supply in interdune areas is
clearly inappropriate in the Rockaway-Nedonna Beach area. The sand
is needed on the beach or in the foredune to protect existing
development. Inland movement of sand would be damaging to existing
structures.

Beach Nourishment

Although it has not been used on the Oregon Coast beach nourishment is an
accepted practice elsewhere in the world, especially on receding
coastlines. Basically beach,nourishment compensates for beach erosion by
adding new sand.to the-beach-dune-nearshore system. The effect of adding
new sand is obvious:

-33-

"...if the supply [of sand] is somehow enhanced, the
beach will widen (i.e., accrete) until equilibrium is
established once again. (Colonell, in Clark, 1977 p.

Artifical enhancement or beach nourishment is tremendously expensive ($50
to $400 per foot) and requires frequent maintenance (at I to 5 year
intervals). Clark, 1977, p. 331). Also sand must be imported from
outside the beach-dune-nearshore system to result in a net increase in
the size of the beach. Removal from another part of the beach-foredune
system will not enhance protection:

An erosion problem should not be solved by bringing sand from some
other part of the same beach. [TIhere are two appropriate sources of
supply for beach nourishment: (1) the open.ocean or broad
nonestuarine bays beyond a depth of about 40 feet (14 meters), or
(2) around inlets or other areas of accretion, where the supply is
constantly replenished by natural forces, particularly when
navigation dredging is being done." (Clark, 1977, 329).

While periodic navigation dredging occurs at the mouth of Tillamook Bay
(and is proposed for Nehalem Bay) no disposal has occurred inthe
beach-dune-nearshore system. Beach nourishment was proposed by
Stembridge in 1978 but was rejected because of concerns of resource
agencies that sand deposited in nearshore waters would smother nearshore
biological communities. Consequently, dredged material is instead
disposed further offshore (i.e., beyond the nearshore system) or on
upland sites.

Management Recommendations

The Corps of Engineers should re-evaluate nearshore or beach disposal of
dredged material to determine if beach nourishment can be accomplished in
an environmentally acceptable manner. This should include an assessment
of sediment suitability (i.e. sand grain size) and alternative disposal
techniques.

-34-

Beach Pushing

Beach pushing involves bulldozing large amounts of sand from the lower
beach onto or toward the foredune. Beach pushing has been used in other
states to rehabilitate eroded beaches and foredunes. Experience in North
Carolina concludes that there is no detailed scientific evidence on the
effectiveness of beach pushing, that it may increase storm damage if done
on a large scale, that it may have the same effect as a bulkhead if done
continuously, and that benefits are short term at best. (North Carolina,
Coastal Resource Commission, Outer Banks Erosion Task Force, July 1984,
pp. 11-12). While the North Carolina Coast is substantially different
from Oregon's the concerns about beach pushing there deserve
consideration.

Bulldozing of beach sand has been done on a very limited basis in
Oregon. One-time ."shaving" has been allowed to provide fill to properly
slope eroded banks for installation of revetments at Kla-ha-nie Shores in
Lane County fn 1983. Beach shaving was done at Siletz Spit-in 1973 to
provide sand to cover a revetment to enable dunegrass planting. In 1985,
limited shav-ing was allowed to rebuild an eroded dune in front of a low
marine terrace at the Sea Ridge development in Lincoln Beach. Each of
these examples is characterized by (1) limited removal, (2) one-time
excavation as part of a more-permanent stabilization effort and
(3) retention of sand in the beach, dune system (except at Kla-ha-nie
where sand was placed behind the riprap.)

Earlier stated facts on dune processes indicate the need to avoid
excessive alteration of the natural beach slope. As noted, beach slope
is a critical factor in dissipating wave energy, thus minimizing
shoreline erosion and flood damage. Sand shoved from the beach area
should be used to maintain the same slope angle into the foredune
foreslope area.

Care must be taken because extensive excavation of sand can steepen the
slope of the beach increasing potential wave run-up and beach erosion

-35-

during storms. As noted earlier, beach slope is a critical factor in
dissipating wave energy and minimizing shoreline erosion and flood
damage. Also bulldozed sand that is "mounded" into a dune, and then
vegetated provides less protection than a naturally-built dune. The
mounded dune will only be vegetatively stabilized near its surface. When
the top of the dune erodes the core of unstabilized sand is exposed and
rapidly erode s. -A naturally developed dune will have beachgrass 'roots'
extending throughout much of its height. Beachgrass 'roots' (actually
dormant parts of the plant) help hold the dune together even as it erodes.

Management Recommendations:

1. Beach bulldozing shall only be allowed as part of an overall dune
stabilization project whose principal purpose is to increase
protection provided by the foredune consistent with this plan and
where evidence is provided that there is a surplus of sand on the
beach. Sand moved from the beach shall only be used to repair
erosion of a foredune area, to promote growth of a new foredune or to
widen narrow and low spots in the foredune, to establish an
appropriate slope for riprap on a steeply eroded shoreline, or to
- cover revetment for the purpose of planting beachgrass.

2. Beach bulldozing shall remove only a thin layer of sand from the
beach. The amount of material removed shall not change the grade of
the beach (from the low tide line to the toe of the foredune) by more
than _%. Depth of excavation shall not exceed I foot below the
existing surface elevation. Sand shall be moved from the portion of
the beach immediately seaward of the site to be filled unless there
is a surplus of sand in the beach and dunes protecting adjacent areas.

3. Bulldozing of sand landward of the foredlune crest or out of the
vicinity of active rip currents shall not be permitted.

4. Dozed areas above the summer high tide line shall, as necessary, be
smoothed to conform to adjacent areas that have not been dozed and
revegetated.

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5. Beach bulldozing shall not be done to excavate sand from the beach
system for removal to a back area.

Sand Mining/Removal

While sand has not been mined or removed from the Nedonna-Rockaway area
this practice has occurred elsewhere on. the Oregon Coast. For example,
sand has been- cleared from in front of the Seaside Prom on an ongoing
basis to maintain an open sand beach there. Mining or removal of sand
from the dune-beach-nearshore system is inappropriate because it reduces
the amount of material available to absorb ocean wave energy. Further,
indiscriminate removal of sand (for mining or mineral extraction) can
disrupt the natural system and initiate or accelerate erosion.
(Lindberg, Uses, Impacts and Management Considerations in Beaches & Dunes
Handbook for the Oregon Coast, 1979, p. 5). Also sand mining at Lincoln
Beach may have contributed to the severity of erosion at Siletz Spit in
1972-73 (Komar, 1978).

The importance of sand supply to natural.dune processes causes le ading
experts to recommend that mining of dunes for sand should be banned
c-ompletely. (Clark, 1977, 332). Studies for the Oregon Coast suggest
that sand removal should only be permitted where:

- in-mi-grating sand is posing a threat to structures, habitat, land or
property [or]

- significant accretion is known to occur (however, due to a possible
zero net littoral drift and limited sources of new sand supplied to
Oregon's beaches, removal of sand even from areas of historic
accetion is not recommended.) (Lindberg, Sand Removal, Beaches and
Dunes Handbook for the Oregon Coast, 1979, pp. 17-18).

There is no evidence that substantial @mounts of new accretion are
occurring in the Rockaway-Nedonna Beach area which would justify sand
removal. (If substantial accretion did occur, efforts should be made to
stabilize it as part of a widened foredune.)

-37-

Sand removal from the beach requires permits from the Division of State
Lands, the State Parks and Recreation Division (oceanward of the beach
zone line) and from the Corps of Engineers. Implementation of Goal 18's
foredune grading provisions requires that removal of sand from the beach
foredune system be prohibited.

Management Recommendation

Mining or removal of sand from the beach and foredune system should be
prohibited.

RESIDENTIAL DEVELOPMENT

Permanent development on foredunes may cause major alterations to the
beach-dune system. This is particularly true if development is located
on portions of the foredune that are subject to long-term erosion or
ocean flooding.

As noted earlier the foredune is a dynamic landform continuously being
reshaped by ocean waves, storms, and currents. Development attempts to
fix the foredune in place and in essence, cuts off the foredune as a
reservoir of sand to the rest of the beach-dune system. If structures
are located too far forward, are unprotected or are inadequately
protected, ocean storms will erode the foredune and damage or destroy
homes. If seawalls or revetments are installed the natural system is
disrupted and beach erosion results.

The most dramatic examples of inappropriate foredune development in
Oregon are Bayocean Spit and Siletz Spit.

"During severe episodes of erosion of'Siletz Spit (in
1972-73), the foredunes were cut back some 100 feet
around the lengths of ocean-facing lots. Studies of
aerial photographs dating as early as 1939 show that
such erosion has occurred repeatedly-in the past, but,.-

-38-

that following the erosion, beach sand is washed and
blown into the eroded zone eventually rebuilding the
foredunes (Rea, 1975; Rea and Komar, 1975; Komar and
Rea, 1976b)." (Komar, 1979, p. 34)

"It would have been preferable if development on
Siletz Spit had been prohibited in the approximately
100-foot zone where foredunes are susceptible to rapid
wave undercutting and erosion. Then the natural cycle
of erosion followed by dune rebuilding could have
continued. Instead, the presence of the homes
necessitated the placement of huge quantities of
riprap." (Komar, 1979, p. 35)

While these two situations were both narrow sandspits rather than open
coastline, they still indicate the extent of erosion that can occur in
foredunes in a major flood or erosion event. Also the north end of
Nedonna experienced similar rates of erosion in 1977-78. For these
reasons residential development of all types is generally discouraged in
foredune areas. Statewide Planning Goal 18 (Beaches and Dunes) prohibits
new residential, commercial and industrial development on foredunes
subject to wave overtopping and ocean undercutting (i.e., erosion).
However, most of the study area is exempted from this prohibition because
it was either developed or committed to development prior to the
effective date of Statewide Planning Goal 18 (Beaches and Dunes).

New houses as well as remodeling and other improvements are allowed in
developed foredune areas. Nonetheless, the location of these
improvements can have an important influence on the stability of the
foredune. New or expanded structures or improvements in foredunes.can
also directly or indirectly damage the foredune or stabilizing vegetation.

"The construction of any development typically
requires.that the natural setting be modified in
preparing the site. When preparing a site on a sand

-39-

landform the actions involved often destroy the
stabilizing vegetative cover exposing the underlying
sand to the forces of erosion.

This erosion weakens the structure of the sand
landform and decreases its value as a sand reservoir
and buffer (Olsen and Grant, p. 31). Examples of
specific actions and impacts are:

(1) The lowering of foredune increases the washover
potential, salt spray kill-off and wind erosion;

(2) The disruption of dune vegetation can result in
destabilization and blow-outs.

(3) The construction on certain foundations in this
windblown environment may cause erosion/accretion
activities similar to those of jetties by having
sand accumulate on the lee side and eroded on the
windward side. Certain alignment of structures
may also alter wind flows causing simlar erosion/
-accretion activities in-the immediate vicinity."
(Lindberg, 1979, pp. 10, 11)

Most construction at Nedonna Beach, particularly recent construction, has
not seriously damaged or reduced foredune height. However, there are
other places on the Oregon Coast where foredunes have been improperly
graded thereby lowering the crest or destroying stabilizing vegetation
leading to the erosion problems described above.

Minor improvements or structures which have only minimal or negligible
impacts on dune stability and which do not commit the foredune to
structural protection are generally appropriate in forward (i.e.,
oceanward) portions of the foredune. This category includes minor
improvements like windbreaks or free standing decks which are neither
extensive nor involve much capital investment.

-40-

Ne w structures or large or extensive accessory structures, like an
addition or a garage, which do disturb a larger area and which involve a
substantial investment are appropriate only in back dune areas, away from
the area likely to be eroded.

Setback Line

Development in foredune areas should be set back well beyond the point of
the maximum probable erosion event. All building should be restricted to
the backslope with no encroachment on the crest area. In this way, the
beach and foredune can cycle through the natural process of erosion and
repair without the necessity of structural stabilization of the shoreline
to protect oceanfront homes. (Where the shoreline is retreating because
of long-term erosion the setback line should also consider the annual
rate of erosion and the life of the structure and replacement
structures.) Most residential development in Nedonna Beach and Rockaway
Beach appears to be set back far enough to withstand periodic episodes of
beach erosion. An examination of aerial photography shows that most
residences are located behind the 1939 shoreline location, which is the
maximum extent of ocean erosion in most of the study area over the last
50 years. Notwithstanding these facts, it is possible that major beach
erosion could occur anywhere in the study area. In fact several parcels
in the study area, including the northern portion of Nedonna Beach, were
riprapped in response to erosion events in 1977-78.

Most of the study area has suffered some erosion over the last 46 years.
However, the foredune has been of sufficient width and erosion events
have been modest enough so that existing homes have not been destroyed by
erosion. However, this condition may not continue. Based on historic
erosion events on this stretch of coast and on other parts of the Oregon
Coast it is reasonable to expect that 150 to 200 feet of erosion could
occur in any part of the study area. Consequently, a setback of 150 to
200 feet from the front of the foreslope for new residential development
would be advisable.

-41-

However, most of the study area existing residential development
encroaches on the recommended setback. In these areas a widened and
heightened foredune should be promoted. This would begin to provide
adequate protection from erosion and flooding. Also, the location of
existing dwellings relative to the shore should be used as a setback line
for new dwellings or improvements. This would require that new dwellings
be located in linewith existing adjacent buildings. (The City of
Rockaway Beach currently has such a requirement based on setbacks of
adjacent homes from the beach zone line.)

On-site waste disposal systems would be subject to the same erosion
hazards as other structures. Drainfields fertilize dune grass causing
denser growth which creates uneven dunes and an extreme fire hazard.
Also European beachgrass will create an extensive feeder root system (as
much as 50' in diameter) clogging the drainfield, thereby reducing or
destroying its effectiveness. Vegetation with less aggressive root
systems should be planted in drainfield areas.

Management Recommendations

1. New or expanded residential or commercial structures should be
located landward of the line of existing development. If so located
interference with dune processes or an earlier need for shoreline
protective structures might be avoided.

2. Site preparation, like residential development, is appropriate only
behind the line of existing development. Site preparation should be
done with care to avoid effects on adjacent foredune crest and
backslope areas. Excavated sand not used on site should be used to
fill in low spots in the foreslope and crest of the foredune on the
site or adjacent lots.

3. Remodeling which does not expand or relocate the structure oceanward
is appropriate. Such changes would not have important new effects on
the foredune which require additional regulation.

-42-

4. Accessory structures are major constructed improvements and, like
residences, are only appropriate landward of the existing setback
line.

5. Sewage disposal systems should be prohibited in all three parts of
the foredune (foreslope, crest, and backslope). On-site waste
disposal systems should be installed only in the back area suitable
under DEQ, County or City requirements with the condition that no
beach grass be planted over them.

Minor Structures

Other structures associated with residential use in dune areas include
windbreaks, decks, and small open sided shelters. While such structures
are rare in the study area, they may be proposed in the future. Minor
structures need to be properly sited and built because any structure in
the foredune has the potential to interfere with wind patterns or destroy
stabilizing vegetation. The foreslope is particularly sensitive to
alterations while the crest is less so.

Management Recommendations:

1. Minor structures built oceanward of existing homes should be limited.
in size and location so that they do not destroy needed stabilizing
vegetation or disrupt wind patterns across the foredune. Except for
pile supported boardwalks, no structures should be located on the
foreslope.

2. Minor structures such as boardwalks and freestanding decks should be
built on pilings and elevated above stabilizing vegetation.
Alteration of the foredune or movement of sand should be limited to
placing of piles.

-43-

VEGETATION MANAGEMENT

Vegetation, particularly European beachgrass, plays a critical role in
maintaining the stability of the foredune. The foredune has grown to its
present height, width, and shape largely because of the ability of
European beachgrass to trap and hold windblown sand. If the beachgrass
is damaged or destroyed, winds will literally blow the dune away. Inland
areas will be covered with sand, and flood protection provided by the
foredune will be compromised. Because of the importance of vegetation
and its sensitivity to damage, all man-caused changes to dune vegetation
should be controlled. Theseincludes planting, grazing, fertilizing,
mowing, and application of herbicides or other chemicals.

Management of vegetation includes both regulating and prohibiting actions
which would ham dunegrass and taking steps to encourage a well-vegetated
foredune. As noted elsewhere, the foredune in the study area has been
extensively altered and in many areas is too low and narrow to provide
effective protection from serious flooding events. Planting bare spots
and fertilizing existing European beach grass can help these sections of
the foredune heal.

Despite its importakce and effectiveness in stabilizing dunes, or perhaps
because of it, many oceanfront property owners have removed, destroyed or
altered stands of beachgrass. Most have cleared the grass to prevent
further sand accretion, while some simply consider dune grass a nuisance
or prefer open sand. Such alterations are generally not harmful in back
areas where beachgrass is often not needed for stabilization and may in
fact be a fire hazard. Unfortunately, many alterations have occurred in
the foreslope and crest where almost any alteration interferes with the
grasses stabilizing ability. The following secti ons describe how
particular activities can impact dune vegetation and how they ought to be
regulated.

Alterations to vegetation are typically not regulated by local
governments or state or federal agencies. Such regulation is limited

-44-

because it is considered an unnecessary infringement on the right to use
property. It is also quite difficult and expensive for government
agencies to administer such controls. However, vegetation plays so
critical a role to the stability of dunes and safety of oceanfront
development that additional regulation of changes to vegetation is
necessary.

Direct regulation of vegetative alteration (i.e. by permit) is considered
unworkable and unnecessary. Instead, an indirect system is recommended.
This would involve an educational program to inform properly owners of
the importance of vegetation and proper management techniques. The city
or county would periodically monitor the area to make sure vegetation is
being managed consistent with the recommendations noted above. Where a
recommendation has been violated the county would inform the property
owner and seek restoration. If the problem is not resolved the county
would cite the violator and conduct needed restoration activities.

Planting European Beachgrass

Planting of European beachgrass on the crest and foreslope will be
critical to strengthening the-foredune and repairing occasional damage.
As noted above, this grass has the ability to trap and sta6ilize large
amounts of wind blown sand. Established European beachgrass can survive
and stabilize sand accretion to the height of the grass (18'1-2411) per
year (and more if fertilized). European beachgrass is also the most
effective means of stabilizing recently filled or graded areas.

If improperly planted or damaged, beach grass will fail or create only
patchy coverage. Patchy survival will result in hummocks and
discontinuous rather than uniform dune growth. This results in less
protection against erosion and flooding than would be provided by a
uniform dune. Replanting to achieve uniform dune growth is advisable in
such situations.

-45-

Beach grass needs a continuing supply of fresh sand for fertilization.
For this reason it is inappropriate in back dune areas, where very little
new sand accumulates. The exception is the use of beach grass as an
initial stabilizer in open sand areas. Beach grass plantings in open
sand back areas should be followed quickly by introduction of climax
species to replace the beach grass. In addition, old stands of beach
grass are flammable and can be a fire hazard to nearby homes. Other
species of stabilizing vegetation are more appropriate in back dune
areas. For example, purple beach pea is an effective secondary
stabilizer and is extremely fire-resistant.

Management Recommendations:

I. Open sand areas in foredunes should be planted with European
beachgrass according to the specifications in the Grading Plan.

2. Any graded or filled area which is unlikely to re-establish dune
grass because of the absence of vegetation or the depth of grading or
fill (i.e., where grading removes more than 3' or where fill over a
vegetated area exceeds 3 feet) should be replanted according to the
specifications in the Grading Plan. (This includes areas of the
foreslope, the forward portion of the crest; the back portion of
crest and all open sand areas larger that 20 square feet.)

3. Fire-resistant species are the preferred stabilizing vegetation
within 25' of existing dwellings or structures. Where revegetation
is required within 25' of structures the initial or secondary
plantings, as appropriate, shall be to fire resistant vegetation,
such as purple beach pea. Rock blankets can also be an effective
firebreak around homes.

Mowing of Vegetation

Several homeowners have mowed beachgrass, usually to provide a better
view of the beach or ocean. The effects of mowing on the dune depend on

-46-

the time of year and the part of the dune that is mowed. European
beachgrass itself will survive and regrow after being cut. In fact, like
other grasses, European beachgrass will respond by putting out more
blades of grass per plant. Once cut, beachgrass loses most of its
ability to trap windblown sand. For this reason, mowing should never
occur on the foreslope since vegetation there is almost always receiving
some windblown sand.

Mowing of beach grass on the foreslope of the foredune allows free
passage of windblown sand to the crest and backslope areas. This tends
to build the height of the crest area and buries things located on the
backslope. Mowing beach grass on the crest area of the foredune allows
free passage of windblown sand from the beach if foreslope vegetation is
not sufficient to trap the sand. The result is buried structures and
destruction of climax vegetation. Mowing beach grass in backslope or
back areas has no impact on the stability of the foredune system and will
reduce the fire hazard caused by old, dry stands of starved beach grass.

ManagementRecommendations:

L Mowing of crest and backslopes should only be done between March and
October and then only if the foreslope area is sufficiently vegetated
to capture accreting sand.

2. All mowed areas shall be fertilized with 21-0-0 ammonium sulfate at a
ratio of 100 pounds per acre.

Application of Herbicides

Herbicides can destroy stabilizing dune vegetation. The first effect of
herbicides is a stand of dead, dry vegetation which is a severe fire
hazard. Eventually the vegetation decays and is removed or buried and an
open sand areas results. Sand movement is reactivated reducing the
height or width.of the foredune and resulting in reduced protection from
flooding and erosion. Use of herbicides can be appropriate in back dune

-47-

areas as part of a program to establish secondary stabilizing vegetation,
a yard, or a firebreak. Use of herbicides for these and similar purposes
needs to be carefully limited to assure that damage to the foreslope and
crest does not occur and that the back dune area is not reopened to wind
erosion.

Management Recommendations:

1. Use of herbicides to control or eliminate vegetation in back dune
areas (i.e., behind the backslope) should only occur where the
foredune in front of the area is functioning to block wind erosion
and sand accretion. Spraying should not occur when the wind is
blowing.

2. Herbicides should be applied with care so that vegetation on back
dune, crest or foreslope is not sprayed or affected. Vegetation in
crest and foreslope areas damaged or destroyed by application of
herbicides should be promptly restored with stabilizing vegetation.
All spraying of herbicides should be done following directives from
the County Extension agent or SCS technician.

3. Back dune areas should be promptly replanted or stabilized to avoid
wind erosion of open sand areas.

Nonstabilizing Vegetation

Homeowners have and will continue to landscape their property to improve
its aesthetic and economic value. Planting and propogation of
nonstabilizing vegetation in back dune areas (i.e., landward of the
backslope) is appropriate since such areas are not subje ct to continued
sand accretion. Planting of nonstabilizing-vegetation in foreslope,
crest and backslope areas is generally inappropriate. Such plantings
usually involve destruction of existing stabilizing vegetation and the
new vegetation is unable to withstand the accretion of sand.
Nonstabilizing vegetation eventually fails, reactivating the area to wind
movement and causing sand build-up in inland areas.

-48-

ManagementRecommendation

Non-stabilizing vegetation, including ornamental landscaping lawns, and
gardens, should bellocated in back areas only.

Firebreaks

Beachgrass and other herbaceous vegetation dry out during summer and fall
months and may create a fire hazard for some oceanfront dwellings because
fire can spread rapidly through dune grass. (Beachgrass will, however,
recover from fire.) Unvegetated firebreaks (i.e., open sand areas)
around houses are counterproductive in most dune areas because they can
result in blowouts around the foundation of the house. Certain types of
stabilizing vegetation, most notably purple beach pea, are fire-resistant
and can form an effective firebreak around oceanfront homes and reduce
the potential for blowouts in backslope and back dune areas.
Fire-resistant vegetation introduced into wind stable back dune areas
will generally succeed even healthy stands of beach grass through natural
competition.

Unvegetated firebreaks such as-rock blankets are an appropriate means of
providing protection to oceanfront homes.

Management Recommendations:

1. Fire-resistant vegetation should only be planted when the foreslope
and crest are adequately stabilized to prevent significant
accumulation of windblown sand.

2. Fire-resistant vegetation should not be planted in the foreslope.
Fire-resistant vegetation planted in the crest or back slope must be
able to withstand some sand accumulation; purple beach pea is
recommended.

-49-

3. Fire-resistant vegetation should be planted in existing stands of
beach grass. Where planting of fire-resistant vegetation involves
removal of existing stabilizing vegetation (i.e., beach grass) it
shall be done in areas of not greater than 500 square feet per year
in order to assure that new vegetation is properly established and
that open sand areas are not created.

4. Rock blankets may be used in backslope areas in place of stabilizing
vegetation where the foreslope and crest are adequately stabilized to
prevent significant accumulations of windblown sand.

_50-

BEACH ACCESS

Beach access includes both pedestrian and vehicular access from public
and private lands between back dune areas and the beach. Improperly
located or over-used accesses can destabilize the foredune by trampling
dunegrass and creating a low spot subject to wind scour. Some controls
are needed to ass ure that accesses are properly designed and maintained.

Public Access

Public pedestrian access is necessary to provide for public use and
enjoyment of public beach areas. Inadequate public access discourages
public.use of the beach and encourages trespassing across private
property. Improperly sited or over-used public access points can
destabilize the foredune by destroying vegetation leading to blowouts.
Dune vegetation is so sensitive to disturbance that even limited foot
traffic across the dune can lead to serious damage to the foredune. If
vegetation, particularly european beachgrass, is repeatedly trampled, it
dies and its sand trapping function ceases. If the pathway is oriented
into the prevailing winds, this can result in a blowout of the foredune.
Blowouts cause a loss of sand from the beach and dune to inland areas and
can provide an avenue for intrusion of ocean floodwaters to low lying
areas behind the foredune. Also, pathways once created tend to attract
use because of the inconvenience of walking through stands of
sharp-tipped dune grass.

Most public accesses in the study area have not harmed the foredune
because of.their size, orientation and limited use. Public accesses are
typically narrow pathways (up to three feet wide) running east-west,
which receive only low to moderate pedestrian use. This combination of
factors, particularly the orientation of accessways away from erosive
winds (northwest and southwest winds), has prevented blowouts. At the
jetty parking lot in Nedonna Beach indiscriminate vehicular access across
the foredune has either destroyed stabilizing'vegetation or prevented it
from being established.

Some public access points, particularly street ends are inadequately used
because they are not signed. This often leads to trespass across nearby
private property.

Management Recommendations:

1. Pathways from the back area to the beach should be located east-west.

2. Pathways shall not exceed four feet in width in order to maintain as
much vegetation as possible and to discourage vehicular use of
pedestrian praths.

3. Wher e blowouts occur at public access points they should be promptly
stabilized with beachgrass and, as appropriate, fenced and signed to
direct pedestrians to acceptable access points.

4. Signs should be placed on the foreslope and at landward entrance
points to public accesses to encourage use of established pathways
and discourage trespass across nearby private property.

Vehicle.Access

Vehicles, because of their size and weight can severely damage dune
vegetation with even very limited traffic. Use of the beach by private
vehicles throughout the study area is prohibited by the Oregon Department
of Transportation under the Beach Law. Vehicular access to the beach in
emergencies is allowed. Situations where vehicles may be appropriate on
the beach include Coast Guard Search and Rescue at the jetties, oil spill
clean-up, haul out of grounded boats, clean up of debris from barge or
ship sinking or access for construction equipment for shoreline
stabilization or other permitted beach/dune alterations.

The present vehicle access at the Jetty Parking lot at Nedonna Beach has
destabilized the foredune there. The result is a breach of the foredune

-52-

creating an opening for intrusion of windblown sand and ocean storm waves
to the parking lot and inland areas. The County Road Department has
periodically removed accumulated sand from the parking lot to keep it
clear.

Management Recommendations

1. Vehicular access points should be located only in dune areas where it
is possible to orient the access so that it does not cause a foredune
blowout.

2. Vehicular access shall be designed, constructed and maintained to
assure the foredune is not reduced in height.and that stabilizing
vegetation on either side of the access route is retained. Access
routes shall be as narrow as possible to permit use by emergency
vehicles (i.e., 10-12 feet wide). Fencing or signing may be.
necessary to assure routes are used and adjacent vegetation is
maintained.

3. ODOT's prohibition on vehicular use by the general public is
- appropriate and should be-continued because it would be difficult to
regulate or prevent traffic from damaging the foredune.

Private Access

Private pedestrian access routes, like other access routes across the
foredune, can result in trampling of stabilizing vegetation to the point
a blow-out is created. While private pedestrian routes have been a
problem on high traffic beaches, Rockaway Beach and Nedonna Beach appear
to receive light enough use that pedestrian access has not severely
damaged vegetation or created blowouts. Most private accesses are
located east-west, away from the direction of potentially erosive winds.
If this pattern of use changes, then some control over private accesses
may be appropriate. Some residents have expressed concern that the

-53-

foredune is a barrier to beach access by elderly and physically
handicapped persons. Boardwalks or hard surface pathways are the most
appropriate solution where this is a problem. The boardwalks should be
built on pilings and the walkway elevated above stabilizing vegetation.

Management Recommendation

Private pathways should be encouraged to follow the recommendations set
for public pathways, but regulation is unneccessary at this time.

-54-

OTHER ALTERATIONS

There.are a number of other of human activities which can adversely
affect dune stability but which fall outside of the categories listed
above. Most are usually not regulated by zoning ordinances or are
subject to only minimal requirements. However, because the foredune is
sensitive to virtually any alteration, some additional regulation of
these activities-is appropriate in theforedune. The specific
alterations discussed here include: windbreaks, open-sided shelters,
fences, operation of motor vehicles and fires.

Motor Vehicle Operation

Unregulated operation of motor vehicles (particularly off-road vehicles)
in vegetated dunes damages and can destroy stabilizing vegetation. At a
minimum, such activity impedes growth of the foredune. In contrast, the
beach can withstand substantial vehicle use. It is extremely difficult
to ensure that beach traffic does not spill over to dune areas. Despite
some reports of use by three-wheelers, single seat all-terrain vehi0es,
off-road vehicles do not appear to be a major problem in the area. This
is probably due in large part to the Department of Transportation's
current prohibition on operation of motor vehicles on the beach in this
area (except for emergency vehicles).

Access across the foredune by vehicles for emergency operations, such as
search and rescue, fishing boat removal or foredune grading, should cause
little impact on dune stability because such activities are infrequent,
and because they occur in selected locations where damage can be
minimized or mitigated.

Management Recommendation

ODOT should continue its prohibition on operation of motor vehicles on
beaches in the Rockaway/Nedonna Beach areas. City, County and State
agencies should monitor and vigorously enforce this prohibition.

_55-

Fi res

Open fires in vegetated dune areas are a major fire hazard to adjacent
homes and can threaten dune stability because of high winds and the
flammability of most stabilizing vegetation, particularly beach grass.
Even fires close to vegetated dunes are a hazard because of the potential
for wind-borne coals to start grass fires.

Fires on the beach which are properly set back from dune vegetation can
be conducted with little hazard to adjacent development. Camp stoves and
charcoal barbeques are preferable since they are more easily controlled
and less susceptible to winds.

Management Recommendations

1. Open fires in or near vegetated dune areas should be prohibited.
Open fires are appropriate on the beach or in back yards if they are
set away from flammable dune vegetation.

2. Oceanfront property owners should be encouraged to plant
- fire-resistant vegetation near their homes to serve as a fire-break.
If fires occur, burnt areas should be promptly restabilized by
fertilizing with 200 pounds of 21-0-0 ammonium sulfate during rain or
with irrigation.

-56-

CREEK OUTLETS/EMBAYMENTS

Three activities, riprap, stream clearing and log removal, have been
conducted in the past in stream embayment areas to protect existing uses
there. These are discussed below. Other uses and alterations are
generally inappropriate in stream embayment areas because of the
potential for adverse effects on other areas and the inadequate
information on the dynamics of these areas and the effects of physical
changes to them.

There has apparently been some discussion in the past by the community of
closing off or consolidation of the stream outlets as a long-term
solution of flooding and erosion caused by embayment areas. This would
involve linking two or more of the lakes together, and blocking off one
or move outlets and slightly enlarging another. A more dramatic proposal
would link all of the lakes between Nehalem Bay and Tillamook Bay
together and establish a combined outlet directly to one or both bays.
All of these propos als would require substantial geologic and engineering
investigation beyond the scope of this study. In addition, the cost of
carrying out such a scheme efforts is likely to be substantial; probably
greatly exceeding the benefits-of reduced flooding or erosion.

Most alterations of the stream embayment areas are regulated by the
Division of State Lands. The Removal-Fill Law, administered by DSL,
requires a permit for placement or movement of more than 50 cubic yards
of material on the beds or banks of a stream or the beach. This covers
virtually the entire embayment area and shoreline. The Beach Zone line
is generally located oceanward of the embayment shorelines so Parks and
DSL's jurisdiction is not coincident in these areas.

Log Clearing

Cutting of and removal of driftwood is an important source of fuel for
some residents in the area and has historically been allowed on a
noncommercial basis. The Oregon State Parks Division, regulates this
activity.

-57-

Large accumulations of driftwood (i.e., those wide enough to cover the
mouth of a stream outlet) in stream outlets can effectively dam the
creek, causing a rise in inland lake levels and flooding of low-lying
homes and properties around the lakes. These accumulations are usually
the result of ocean storms:

"...large storms and high tides deposit debris and sand
that block the stream outlets of Crescent Lake, Rock
Creek and Clear Lake. Heavy rainfall and the resulting
run-off then cause flooding adjacent to the lakes and
Rock Creek in the vicinity of B Street." (Flood
Insurance Administration, P. 4).

When these incidents have occurred in the past, stream outlets have been
cleared or partially cleared of driftwood and debris to reestablish
previous lake levels.

Large accumulations of driftwood at the mouth of stream outlets can also
be an effective barrier to ocean storm wave penetration. If driftwood
accumulations are interlocked, usually a result of natural accretion,
they can be an effective barr-ier to ocean storm waves. Improper removal
of logs for firewood or as part of a poorly conceived effort to relieve
stream blockage can breakdown the interlocking and thus, destroy the
ability of log accumulations to prevent ocean wave intrusion.

Small accumulations of driftwood or large poorly interlocked
accumulations can actually increase flood damage because as larger logs
are floated they become battering rams or missiles powered by ocean storm
waves. In the past such logs have caused serious erosion or damage to
oceanfront homes.

Management Recommendation:

Removal of log accumulations should be accomplished in a manner which
minimizes increased ocean flooding hazards. If the amount of log removal

-58-

that is required would eliminate the protective interlocking effect of a
driftwood accumulation, then most or all of the driftwood should be
removed.

Stream Clearing

Accumulations of material in stream mouths, outlets and embayments can
effectively da-m streams causing them to change their course across the
beach or causing flooding in upstream lakes. Lake flooding can and has
damaged lakefront homes and properties. Diversion of stream flow across
the beach can cause erosion of embayments, threatening oceanfront homes
with erosion and increasing the extent of ocean flooding.

Clearing streams of excessive amounts of debris to maintain streams in
their present course has been an effective means of mitigating, potential
erosion and lake flooding. Removal of more than 50 cubic yards of
material requiring a permit from the Division of State Lands.

Management Recommendations:

1. Stream clearing should only be permitted where it is clearly needed
to prevent imminent or existing flooding of lakefront areas or to
avoid a major natural relocation of a stream channel which would
cause erosion of the embayment shoreline.

2. Stream clearing to avoid a change in stream channel location should
only be permitted if it is clear that failure to maintain the stream
in its present location would create a greater erosion hazard to
existing development than relocating the stream outlet.

3. Where stream clearing is permitted the amount of material moved or
removed should be the minimum necessary to avoid flooding or
reestablish the stream in its existing location.

_59-

4. Sand cleared from stream channels should be either placed in eroding
-portions of the embayment, on nearby foredunes or smoothed evenly
across a portion of the embayment to reestablish or enhance the
natural beach profile. Sandshall not be removed from the
beach/foredune system.

Embayment Stab-ilization

Stream outlet channels and embayment areas are dynamic features subject
to accretion, erosion and ocean flooding. While these features generally
appear to be in equilibrium throughout the study area, the extent of
their dynamics and the effect of alterations on patterns of erosion and
flooding is not predictable.

Occasional episodes of erosion at stream outlets or at the shoreline edge
-of stream embayments has and can threaten existing oceanfront
development. Riprap or bulkheads constructed in response to this erosion
appears to have been effective in stopping further erosion generally with
minor impacts on adjoining properties. Fill of embayment areas appears
to have caused erosion of nearby areas due to reflected wave energy.

Riprap has generally had less adverse effect on erosion of adjacent
properties than seawalls or bulkheads because of its ability to absorb
wave energy or divert it upward rather than reflecting it directly back
on the beach. Bulkheads have been necessary for erosion control in some
stream outlets because the shoreline between the stream and adjacent
development is too narrow to allow proper sloping to place riprap.

Management Recommendations

1. Structural shoreline stabilization in embayment areas should only be
allowed where erosion-clearly or imminently threatens-existing
structures or developed areas.

-60-

2. Structural shoreline stabilization of embayment shoreline should only
be done by riprap which meets minimum design specifications
recommended in Appendix 6. Filling or riprapping of embayment are'as
should not be located seaward of the embayment shoreline because it
would probably interfere with natural erosion and accretion patterns
in the embayment area and would likely cause increased erosion in
other parts of the embayment.

3. Stabilization of creek outlets shall be by riprap unless the location
of existing structures or improvements adjacent to the outlet make it
impractical to construct riprap to the minimum design specifications
recommended in this plan. If riprap is impracticable, sheet or
timber pile bulkheads may be permitted.

BC:bc
4895D/34C
R2/13/86

Appendix A: Definitions

For the purposes of this study the terms listed below have the following
meanings:

Shoreline Stabilization

A constructed improvement or alterations attempting to fix the shoreline
at a particular location (i,e,)to permanently prevent further landward
movement of the ocean or be c . Stabilization is usually done to protect
existing homes from on-going or imminent ocean wave erosion.

Beach/Dune Alterations

Any activity which involves the placement, movement or removal of sand on
the beach or dune including the placement of structures which affects the
pattern of sand accretion. This includes sand removal, sand placement,
dune grading, foredune breaching, beach bulldozing, placement of sand
fences, beach nourishment and vegetative dune stabilization.

Sand Removal--the excavation of sand in a beach or dune area for any
purpose, usually done as site preparation, dune breaching, dune grading
or beach bulldozing.

Sand Placement--putting sand removed from one area into another area.
Placement is U'sually limited to movement within the beach and dune system
but may include movement of sand into the system from offshore, estuarine
or upland sources.

Foredune Breaching

Creation or enlargement of a gap in a foredune which has the effect of
allowing floodwaters or major amounts of sand to be moved by wind to or
from the beach. Breaching includes any dune alteration which reduces the
height of a foredune to the extent that 100 year velocity flood waters
could penetrate landward of velocity flood zones.

Beach Bulldozing

The grading or movement of a thin layer or layers (6 to 12") of sand from
near the low water line landward toward or to the seaward edge of the
foredune. Bulldozing is usually done for the purpose of repairing an
eroded foredune or to widen or raise the foredune area.

Dune Grading

Mechanical movement and placement of sand usually by a bulldozer which
changes the shape or height of a dune.

-2-

Residential Development

Any alterations or improvement necessary for or associated with
residential use, including home building and expansion, construction of
accessory buildings, fences and other minor structures like windbreaks,
excavation for site preparation, and placement of septic tanks or similar
waste di sposal- -systems.

Structure: A residence, commercial or industrial building or any
other built, attached or improvement, including decks and garages.
Expanded structure--an enlargement of an existing structure by
enclosure or additional floorspace oceanward of the existing building.
Site-Prgaration: Any alteration made to ready a building site for
construction of a structure including excavating, leveling, filling
of sand or removal of vegetation.

Remodeled Structure: Any modification to a structure which requires
a building Fe-r-mi't-'Fut does not increase the lot coverage of the
structure, or change the location of the structure.

Accessory Structure: A building or other constructed improvement
separate-fr-om But used in conjunction with a residential or
commercial structure such as a separate garage, a gazebo or a storage
building.

Wastewater Di@Rosal System: The excavation and placement of a tank
and effluenf-ii6es or similar facilities for the treatment and
dispersal of household, commercial or industrial wastewater.

Ktq(ttation Man@.@ent@

Any of a variety of man-caused changes to dune vegetation, including
destruction, alteration or enhancement of vegetation, planting of
vegetation, fertilizing, mowing, and application of herbicides or other
chemicals.

Planting Beach Grass: Planting of beach grass for the purpose of
stabilizing a dune or establishing vegetative cover.
Mowing of Vtp'tation: Cutting vegetation by hand or machine including
use of a sickle, lawn mower, weedeater or other means.
Application of Herbicides: Spraying or any other means of placing
herbicides or other chemicals which are intended to or are capable of
killing stabilizing vegetation.

Nonstabilizing Vegetation: The planting or propogation of vegetation
that is unable to withs nd accretion of sand typically occurring in
foredune areas.

-3-
legetation Management (continued)
Vegetated Firebreaks' An area covered by fire-resistant vegetation
between a structure and flammable vegetati.on established for the
purpose of preventing the spread of beach or dune grass fires to
nearby structures.

Beach Access

Access includes both pedestrian and vehicular access from public and
private lands between back dune areas and the beach.

Public Access: A pathway or boardwalk from public property, a public
road or a public easement to the beach which crosses public property
or travels along a public road, right-of-way or easement. Public
accesses do not include accesses across private property unless there
is a public right to access, such as an easement.

Vehicular Access: Access points or routes from public property,
including a road or parking lot, to the beach intended or designed to
allow access by vehicles to the beach.

Private Access: A pedestrian access route from an oceanfront
residence -or commercial establishment to the beach which is intended
primarily for use by residents and guests at that location.

Motor Vehicle Operation: Driving, riding other otherwise operating a car,
'6ff--roacT vehi le or motorized vehicle. This does not include use of
vehicles necessary for the con-duct of other permitted activities.

Fires: The starting, tending or maintaining of an open fire using
drifiwood, firewood or any other material, for any purpose including a
cook fire, a bonfire or trash burning. Not included in this category is
the use of small, self-contained campstoves or charcoal barbecues.

Creek Outlets/Stream EmbaXments

Stream Outlet -- That portion of the stream or creek which is
bordered onfined by the shoreline above the beach. Stream
outlets extend shoreward to Highway 101 and oceanward to the point
where the stream meets the open, relatively flat beach.

Stream Channel -- The portion of a stream which runs as open water on
the beach from the stream outlet to the Pacific Ocean. The channel
location may vary daily, seasonally and annually.
ER@yment Area -- The entire stretch of beach and shoreline subject
E6 r_kJ'-5-fI-ue-nce of a stream crossing the beach. This includes the
stream outlet, the stream channel and the beach to the embayment
shoreline. The extent of each embayment area along the shoreline is
defined by the limit of landward recession or erosion in the
shoreline associated with the stream channel. The embayment area
ends where this influence ends and a relatively continuous foredune,
parallel to the ocean shore begins. The emayments area of influence
may vary seasonally.

-4-

Creek Outlets/Stream_Embayments (continued)

Embayment Shoreline The landward limit of the beach associated
with a stream embayment. This shoreline is usually defined by a
current erosion scarp or a foredune in a state of natural repair with
little or no vegetation on the foreslope.

Log Clearing

The removal, excavation, movement or sawing of driftwood logs which has
accumulated on the beach or in stream outlets or embayments as a result
of ocean, storms, or waves, or current.

Stream Clearing

The movement or removal of accumulated logs, sand, stone or other
obstructions from the bed or banks of a creek outlet in order to allow
freer passage of the stream flow.

Riprap: A means of structural shoreline stabilization consisting of the
@Iacement of large, very hard rocks over smaller rocks and usually a
cloth filter blanket to provide protection from erosion.

Bulkhead: A vertical wall usually c onstructed of steel or treated
wood-beams to hold a shoreline in place and provide protection from ocean
or stream water erosion.

BC:cmV
6528D/

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F- i .
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LIST OF ILLUSTRATIONS

MANAGEMENT PLAN

Pocket Beach
Coastal Sediment Transport 1-2
Net v. Zero Littoral Transport 1-3
Changes in Sea Level 1-4
Sand System Cross-Section 1-5

Typical Foredune Cross-Section 1-6
Foredune Before and After Beachgrass 1-7
Rip-rap Design and Placement 1-8
Creek Outlets/Embayments 1-9

GRADING PLAN

Shoreline Changes at South Jetty I-10
Generalized Foredune Cross-Section Changes I-11
Shoreline Change (Plan View) 1-12
1978-84 Cross-Section 1-13
'Dual' Foredune at Section 23 1-14
How Beachgrass Collects Sand 1-15

Placement of Graded Sand 1-16
Clearing Sand Accumulations 1-17
Placement and Spacing of Sand Fences 1-18,
Accessways Through Sand Fencing 1-19

GRADING PLAN CROSS-SECTIONS

Generalized Subarea Cross-Sections 1-20 - 1-23

Site Specific Cross-Sections
-No. I - No. 7 South Jetty Subarea 1-24
-No. 8 - No. 9 Jetty Parking Lot Subarea 1-25
-No. 17 - No. 20 Riley St. Subarea 1-28
-No. 21 - No. 25 Western/Sunset Subarea 1-29
-No. 26 - No. 36 Lark St./Beach St. Subarea 1-30

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COASTAL SEDIMENT TRANSPORT

dunes
streambank:,-..
ocean and bed erosion
disposal

beach

dr 9 -.'surface*
f lood '.'--erosion
discharge C@l
tidal

.,removal
shoals rival

be
storm waves estuary
& rip currents sedimentation

dunes'-,.-

Cliff

..landslide.

NET VERSUS ZERO
LITTORAL TRANSPORT NEAR JETTIES

NET LITTORAL TRANSPORT
Ocean IV

Apt
Not littoral drift

Erosion

Harbor

ZERO NET TRANSPORT

Ocean

Wave crest

Deposition Deposition
Erosion Erosion

Harbor
0 on opol"t
F@7 7
D
---4
lp sit,

CHANGES IN SEA LEVEL

Time (years)
0 10 20 30 40 50
20 1 East Coast

Oregon Coast
0

-20

-40
Alaska

SAND SYSTEM CROSS-SECTION

Foredune Beach Bar

Sea level

Ocean
bottom

Harder rock earshore bottom
,Im-

TYPICAL FOREDUNE CROSS-SECTION

BEACH FORESLOP CREST BACK BACK AREA
SLOPE

1-7

FOREDUNE@ CROSS-SECTION:
BEFORE & AFTER EUROPEAN BEACHGRASS

Present
cross-section

1939
cross-section

Approximate location of
Present location of beach zone line before
beach zone line L introduction of beachgrass

RIP-RAP DESIGN & PLACEMENT

SAND COVER & BEACHGRASS

To re-establish dune after
SLOPE SURFACE flooding episode has passed
AT I TO 11 /2
To minimize
wave energy
LARGE, DURABLE ROCK
To withstand flood
wave energy
11/2

FILTER CLOTH OR
BLA14KET
To prevent sand
from washing out

TOE TRENCH
4-6' Excavation filled with rock to prevent failure
If beach Is eroded to lower level

CROSS-SECTION VIEW

CREEK OUTLETS/EMBAYMENTS

--Stream outlet,

04.
0
0 cc
0

Limit of
embayment Umit of
embayment

Embayment area

PLAN VIEW
1%

Jetty SHORELINE CHANGES SOUTH OF
NEHALEM BAY SOUTH JETTY

County Parking Lot
Beach Drive.
lip.

7,9

1939
1964
1970
1977
1984
Ocean
<NORTH PLAN VIEW

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M CID x F4
> m
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Wo
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0
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> CA

m
0
-4

60
0 0
ICL

to 40 (0

Ob -4

(0
4

ca
:r Riley
0

0
19-

CL
Ir

Western

COMPARISON OF 1978/1984
DUNE CROSS- SECTIONS

Sand accretion
to this level
by 1984 -30
::20
-10
-0
"'une configuration at the end
of 1977-78 erosion event
8 "s v 0'
0 t "'
'@b Y@l 9 8 4

CROSS-SECTION OF DUAL FOREDUNE
From cross-section *23

More Recent Foredune Older Foredune,

26
z1o
:: 0
Foreslope crest k_
slope Beach
Drive

Note that older foredune Is approximately
the same height as 'newer' foredune.

I-is

HOW BEACHGRA SS COLLECTS SAND

Sand deposition around a
beachgrass, windbreak.

As beachgrass Is buried,
new shoots and roots develop
at the dune surface.

PLACEMENT OF GRADED SAND

PRIORITY ONE: Fill In low spots In crest to
a minimum elevation of 26.0'

1effTTMrTMTMTh?11
L--J L-J "I fl-I @- 26.0'

FOREDUNE CREST PROFILE

Crest area* with excess
elevation. to.be. used as fill
Low. -Oarrow crest
Back Houses are.a needing fill
slope-

Crest

F
e
or
slope

PLAN VIEW Ocean

1-7

CLEARING OF SAND ACCUMULATIONS

BEFORE

beach foreslope crest backslope back area

NOTE: Only sand which Is blocking doors or windows or access may be removed.

AFTER 13

beach foreslope crest backelope back area

Graded material should be placed on foredune crest and stabilized.
Clearing sand from around structures does not Include
crest grading to create ocean views.

PLACEMENT & SPACING OF SAND FENCING

Place rye grass straw
at the base of fence
& weight with sand
Guy wire's are staked to prevent blowout
8' out.from fence

once posi.e
L ire drJyen
_30-,
2'@-.hytq-the iand:

Two rows of sand fence are placed 30' apart

CROSS-SECTION VIEW

Posts are spaced End posts should be
100 apart k
eta ed 3 wayi

7
Stake
r-5-
10

30'

C!
Fenco post

Feimce. imust be
-staked'
cr* a
09
'at 50' intervals
8,59,

< PLAN VIEW
Ocean

ACCESSWAYS THROUGH SAND.FENCING
Access sign CornerIa staking is also at an angle-
5' out from the main fence
NAN 40

------------

Guy wires are placed Cross fencing
at an angle, to restrict travel
stakes are 3' out to the accessway
from cross fencing & to catch sand

B A A

PLAN VIEW ,(-Additional seaward fence
to catch sand

Access sign
013*
A- Minimum clearance In accessway
4' for pedestrian ways
12' for auto/truck passages

B- Minimum overlap of 5' between
main fence & extra seaward fence

BEACH TO
ACCESS PARKING
LOT

"A" "B"
A

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m
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m

0
0 Foreslope

M m
x Crest
0

Backslope

Back Area

Beach Zone Line

230'
< .0@

-10

0
Beach Fore- Crest Back- Back Area.
slope slope
Beach
Drive
Existing Fokedune->l

GENERALIZED CROSS-SECTION: SUBUNIT C

Beach Zone Line
215'

0
Beach Foreslope Crest Back - Back,Area
slope
Beach
Drive
JE-Existi ng Foredune >1

GENERALIZED CROSS-SECTION: SUBUNIT D

100 25

200 so 0

Beach Zone Line

200'

More Recent Crest Older Crest

0
Beach Foreslope Crest Back - Back
slope Aria

Beach
Ex Isting Foredu no Drive

GENERALIZED CROSS-SECTION: SUBUNIT E

Beach Zone Line-,

.0@

-26

0
Beach Foreslope Crest Back-
slope

Beach
Drive
K Existing Foredune >

GENERALIZED CROSS SECTION: SUBUNIT F

100 25
Ell 111111111H1111111111 III
200 50 0

Jetty
Existing Faredune 30

Jetty Existing Foreclune

Jetty Existl ng Foredune'-
0

Proposed Foreclune Existing Foreclune
.30

Mot

brA (,Ft GRAPING PLAN (-`KO@@7-,6fCTIOW2
5 UA3AVC@-A A: :Soun-t -SE-7"

Proposed Existing
Foreclune Foreclune
v 30

NO,

Proposed Existing
Foreclune
Foreclune 30

Proposed
Foreclune Existing
Foreclune

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-PROPOSED FOREDUNE

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Z-7

PROP OSED FORiEDUNE

'PROPOSED FOREDUNE

N10. -L Lk C,-C- 50 - 0

rPROPOSED FOREDUME

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No. 35

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Section 3.085: BEACHES AND DUNES OVERLAY ZONE

1. PURPOSE: The intent qof this zone is to manage development uses
and activities in beach and dune areas in order to:

(1) ensure the protection, restoration, and conservation of beach
and dune natural resources;
(2) reduce the hazard to human life and property from natural
events or actions associated with reasonable development of these
areas;
(3) provide for dune grading or sand movement in foredune areas
where an overall plan for managing foredune grading can be
developed without reducing the capacity of these areas to provide
flood and erosion protection;
(4) establish clear guidelines and criteria by which the natural
hazards of beach and dune landforms can be assessed prior to
development.

II. AREAS INCLUDED: The Beaches and Dunes Overlay Zone applies to
the inventory of beach and dune landforms in Tillamook County,
prepared by the U.S. Department of Agriculture, Soil Conservation
Service and published in the 1979 report, Beaches and Dunes of
the Oregon Coast. The dune areas mapped in the inventory are
identified in the Goal 18 (Beaches and Dunes) Element of the
Comprehensive Plan.
This overlay zone includes beaches, active foredunes,
conditionally stable foredunes which are subject to ocean
undercutting or wave overtopping, interdune areas that are
subject to ocean flooding, deflation plains, younger and older
stabilized dunes, and conditionally stable open sand areas.

III. CATEGORIES: The results of the inventory cars be summarized
into three categories of beach and dune shorelands:

CATEGORY(I)- DEVELOPED BEACHFRONT AREAS: Active foredune areas
where an Exception to Goal 18 allows development on the active
foredune. These areas are described in Section 5 of the Beaches
and Dunes Element of the Comprehensive Plan.
CATEGORY (2)- FOREDUNE MANAGEMENT AREAS: Active foredune areas
where an Exception to Goal 18 allows development on the active
foredune and an overall management plan is approved to allow
foredune grading. The management plans for these areas are
contained in Section of the Goal 18 Element of the
Comprehensive Plan.
CATEGORY (3)- OTHER BEACH AND DUNE AREAS: Beach and active
foredune areas committed to resource protection or recreational
use, and stabilized inland dune areas suitable for development.

IV. ADMINISTRATIVE PROVISIONS: Uses within the Beaches and Dunes
Overlay Zone are subject to the provisions and standards of the
underlying zone and of this section. Where the standards of the
overlay zone and the underlying zone conflict, the more
restrictive provisions shall apply.

A. USES AND ACTIVITIES PERMITTED WITH STANDARDS

I. Residential and Commercial Development

(a) Residential development and commercial and industrial
buildings are permitted only on lots or parcels located in
Developed Beachfront and Foredune Management Areas.

(b) Oceanfront dwellings shall be-located as far landward of
the crest of the active foredurse as is physically or economically
feasible to achieve an ocean view. At a minimum, structures shall
be setback in.line with dwellings on adjoining lots or parcels.

(c) Residential structures in active foredune areas shall be
constructed to minimize future needs to remove inundating sand.

(d) Building heights shall be measured from the-existing
grade. Only in Foredune Management Areas shall additional fill be
a1lowed on an oceanfront lot, provided the applicant can
demonstrate that construction on the existing grade can not
provide art ocean view and the provisions of Section 3.060 (Flood
Hazard Overlay Zone) are met. The maximum amount of additional
fill allowed shall be determined on a case-by-case basis by
Tillamook County.

2. Private Beach Access

(a) Boardwalks and pedestrian footpaths to the beach-shall be
permitt ed in all dune areas, except where restricted in Foredune
Management Areas.

(b) Off-road recreational vehicle use in Foreduno Management
Areas shall be restricted to be ach areas. Access to the beach
across active dune areas by -recreational vehicles shall be
restricted to identified public or off-road recreational
vehicular access points.

(c) In Foredune Management Areas, where heavy use of public
easements or rights of way destablizes, dune areas or, adjoining
private property, signs may be placed at landward entrance points
to encourage the use of alternative public access points. Signage
shall be subject to review by the Foredune Management Authority
and Tillamook County.

3. Beachfront Protective Structures

(a) Beachfront protective structures (riprap and other
revetments) shall be allowed only in Developed Beachfront Areas
and Foredune Management Areas, or where "development" existed as
of January 1, 1977, or where beachfront protective structures are
authorized by an Exception to Goal IS..
(b) Proposals for beachfront protective structures shall
demonstrate that:
(1) The development is threatened by ocean erosion or

flooding;
(2) Non-structural solutions can not provide adequate
protection.
(3) The beachfront protective structure is placed as far
landward as possible;
(4) Negative impacts to adjoining properties are
minimized;
(5) Existing public access is preserved;
(6) Construction standards in Section 3.140 (17) are met.

For the purposes of this requirement, "development" means
houses, commercial and industrial buildings, and vacant
subdivision lots which are physically improved through the
construction of streets and provision of utilities to the lot.

Lots or parcels where development existed as of January 1, 1977,
are identified on the 1978 Oregon State Highway Ocean Shores
aerial photographs on file in Tillamook County.

c. The Oregon Parks and Recreation Division shall notify
Tillamook County of emergency requests for beach front protective
structures. Written or verbal approval for emergency requests
shall not be givers until both the Parks and Recreation Division
and the county have been consulted. Beachfront protective
structures placed for emergency purposes, shall be subject to the
construction standards in Section 3.140(17).

4. Foredune Breaching

a. Definition- In dune areas subject to coastal flooding,
excavating the crest of a foredune below one foot above the base
flood elevation constitutes foredune breaching. Lesser actions
over a larger dune area also constitutes foredune breaching if
the action increases the potential for ocean flooding in the
surrounding area.

b. Foredurse breaching shall be allowed in recreational beach
and dune areas only to replenish sand supply in interdune
recreational areas.

b. Foredune breaching shall be allowed in other areas on a
temporary basis in an emergency (fire control, alleviating flood
hazards or other diseaster conditions). For emergency vehicle
access, foredunes shall be breached only after a demonstration is
made that temporary access cannot be accomplished by the use of a
fabric ground cover in combination with a crushed rock overlay.

c. Foredune areas breached shall be restored immediately
following relief of emergency conditions and stabilized using
permanent dune stabilization techniques. At a minimum, foredunes
shall be restored to the pre-existing dune profile. Construction
materials (rock, fencing, etc.) placed to accommodate emergency
vehicle use or circumstances shall also be removed following
relief of emergency conditions.

5. Accessory Structures and Uses

a.'Accessory structures regulated by this section include, but
are not limited to towers for communication facilities, garages,
greenhouses, signs, boardwalks, windbreaks or other fences, and
solar energy or wind conversion systems.

b. Accessory structures %hall be placed either in locations
established by plans for Foredune Management Areas, or in
locations where there will be minimal interference to prevailing
wind and sand distribution patterns.

c. Accessory structures shall not be permitted on crest areas
of active foredunes, except for boardwalks which provide access
across active dune areas to the beach

Compliance with the provisions of Section 5.040 (Gerseral
Provisions Regarding Accessory Uses) shall also be met.

6. Temporary Structures

a. Temporary structures regulated by this section include, but
are not limited to boardwalks, windbreaks or other open-sided
structures, and cabanas or similar structures.

b. Except for sand fences or boardwalks, temporary structures
shall not be permitted in Foredune Management Areas where the
Foredune Management Authority is restoring or stabilizing dune
areas.

c. Compliance with the provisions of Section 5.150 (Temporary
Uses) shall also be met.

7. Drift Log Removal

a. Cutting of driftwood for non-commercial firewood or other
uses shall be restricted to identified areas, if required by a
Foredune Management Plan. Otherwise, the removal of, dr iftlogs
shall be allowed only where it will not increase flooding or
erosion hazards to existing development.

B. USES AND ACTIVITIES PERMITTED CONDITIONALLY

.1. Public Beach Access

a. New public beach access points shall be allowed where
identified in Tillamook County's Public Access Program to Coastal
Shorelands, contained in the GoAl 17 (Coastal Shorelands) Element
of the Comprehensive Plan.

2. Commercial Drift Log Removal

a. The removal of driftwood for commercial firewood or other
uses shall be allowed only if the removal will not result in
increased ocean flooding and erosion hazards to existing
development.
b. Permit approval shall be obtained from the Department of
Transportation, Parks and Recreation Division.

3. Sand Mining and Mineral Extraction

a. Sand mining and mineral extraction shall only be
permissible outside Developed Beachfront or Foredurse Management
Areas.

b. Sand mining shall be permitted in other beach and dune
areas only where a geological investigation establishes that a
historic surplus exists at the site and the mining will not
impair the natural functions of the dune system near the site,
including ground water circulation and littoral drift. Compliance
with ORS 390.725.shall also be required.

4. Dredged Material Disposal

a. Shoreland disposal of dredged material shall be allowed
only at approved sites identified in County Dredged Material
Disposal Plans, except if the disposal is part of an approved
ocean beach nourishment project.

b., Beach nourishment shall be designed to either offset the
effects of active erosion or maintain a stable beach profile.

c. Proposals for beach nourishment shall demonstrate that:
(1) no new buildable upland is created;
(2) the sediment size and chemical characteristics of the
material proposed for beach nourishment is substantially similar
to the substrate in the' beach nourishment a,v-ea; and
(3) erosion of dredged material from the beach nourishment
area does riot result in adverse impacts to nearby estuarine or
significant shoreland habitat areas.

C. SPECIAL ACTIVITIES PERMITTED WITH STANDARDS

1. Sand Stabilization

a . Definition- A program to stabilize a dune area, with
regard to wind or water erosion, by planting aand-stabilizing
vegetation either alone or in combination with the placement of
sand fences.

b..Durse areas excavated for residential and commercial site
development shall be stabilized within 9 months of the
termination of major construction. In dwelling setbacks, fire-
resistant vegetation, such as purple beach pea, shall be
recommended as preferred vegetation in order to minimize fire
hazards.

c. Mowing of beachgrass shall be permissible in all dune
areas, except in foreslope areas of active foredunes where the
foredune is actively accreting seaward.

d. Installing sand fences to build or restore foredunes shall
be permitted in Foredune Management Areas according to
specifications in Foredurse Management Plans. In other dune areas,
sand fences shall be allowed upon approval of Tillamook County
and the Oregon State Parks and Recreation Division.

2. Foredune Grading

a. Definition- The alteration of a foredune, by mechanical
redistribution or removal of sand, which results in a lower or
more uniform dune height. Foredurie grading actions, unlike
foredune breaching, do not increase the potential for ocean
flooding at the site.

b. Foredune grading shall be permitted only in Foredune
Management Areas or in Developed Beachfront Areas. In these
areas, grading shall be allowed only for siting a permitted use,
for removing sand that is inundating a structure allowed by the
underlying zone, or for dune restoration purposes where
recommeded in Foredune Management Plans. Sand graded from
foredune lots shall be relocated either on the beach, in low and
narrow dune areas on site, or off-site at alternative beach and
une areas.

c. Foredune grading to remove inundated sand shall be
permitted only if there is no feasible or reasonable alternative
method of sand removal. Inundated sand shall be disposed of
seaward of existing structures and distributed in a mariner that
shall not impact adjacent dwellings. Graded areas shall be
replanted within 29 months of grading activites, unless the graded
area naturally reestablishes plant cover within the 29 month time
period.

d. Grading to restore foredunes or to maintain ocean views
shall be permitted only in Foredune Management Areas, according
to Foredune Grading Plans included in the Goal 18 Element of the
Comprehensive Plan. Grading in foredune crest areas shall only be
allowed where the dune elevation is more than four feet above the
hundred year flood elevation. At a minimum, Foredune Grading
Plans shall describe standards for redistribution of graded sand
by identifying low and narrow dune areas suitable for dune
restoration, defining the appropriate timing of grading actions,
and outline requirements for future monitoring.

V. SITE DEVELOPMENT REQUIREMENTS: Applications for development
within the Beaches and Dunes Overlay zone shall comply with the
following standards and requirements.

A. General Development Criteria

1. Groundwater and Deflation Plain Areas:

(a) The filling or draining of deflation plains shall only
be permissible where a preliminary site report can demonstrate it
will not lead to the.loss of stabilizing vegetation., loss of
water quality, or irstrusiuore of salt water into water supplies.

(b) Prior to the approval of development using groundwater
sources, a preliminary site report shall demonstrate that
groundwater withdrawal will not lead to the loss.of stabilizing
vegetation, loss of water quality, or intrusion of salt water
into water supplies.

2. Land Grading Practices:

(a) All sidehill roads and driveways shall be bu.ilt entirely
in cut-no-fill unless adequate structuraI support is provided.

(b) Excavated, filled or graded slopes in dune areas shall
not exceed 30 degrees in slope. Surplus excavated material shall
be removed off-site to a location where it will riot constitute a
'hazard, unless low spots can be filled on site and adequately
compacted to accommodate proposed uses.

(c) Proposals for development sha 11 demonstrate that existing
cleared areas are unsuitable for development. The removal of
native vegetation shall be restricted to site preparation
activities for placement of approved buildings or where required
for the installatiion of utilities.

3. Drainage and-E-rosion:

(a) Temporary measures shall be takers to control runoff and
erosion of soils during all phases of construction. Interception
of storm water(roof and footing drains) shall be made in closed
conduits and directed into adjacent roadways or drainages with
adequate capacity to prevent flooding of adjacent or downstream
properties.

(b) Plans for temporary and permanent stabilization. programs,
and the planned ma-intersance of restabilized areas, shall be
provided by the applicant for areas disturbed during site
preparation. At a minimum, areas cleared of native vegetat-iors
shall be identified on building plans and replanted within 9
months of the termination of major construction activities.

B. Beach and Dunes Hazards Report

1. Except in areas identified as older stabilized durses, a
Hazards Report shall be required prior to the approval of
development within the Beaches and Dunes Overlay zone. The
Hazards Report shall include the results of a preliminary site
investi,gation and, where recommended in the preliminary report, a
detailed site investigation.

2. Preliminary Site Investigation

a.'The purpose of the preliminary site report is to identify
and describe existing or potential hazards in areas proposed for
development. The report shall be based on site inspections
conducted by a qualified geologist, engineering geologist or soil
scientist.

b. The preliminary. report shall include plan diagrams of the
general area, including legal descriptions and property
boundaries, and geographic information as required below::

(1) identification of each. dune landform (according to
either the Goal 18 or SCS system of classification);
(2) history of dune stabilization in the areal
(3) history of erosion or accretion in the area, including
long-term trends;
(4) general topography including spot elevations;
(5) base flood elevation and location of special flood
hazard area boundaries;.
(6) location of perennial streams or springs in the
vicinity;
(7) location of the state beach zone line;
(8) location of beachfront protective structures in the
vicinity;
(9) elevation and width'of the foredurse crest.

Elevations shall be reported in relation to the National
Geodetic Vertical Datum of 1929, NGVD.

b. The preliminary report shall either recommend that a more
detailed site investigation report is needed to fully disclose
the nature of on-site hazards or conclude that known hazards were
adequately investigated and state what development standards be
adopted for buildable areas.,

2. Detailed Site Investigation-

a. The purpose of the detailed site investigation is to fully
describe the extent and severity of identified hazards. A
detailed site investigation shall be required either where
recommended in the preliminary site report or when building
plans, including grading plans for site preparation, were not
available for review as part of the preliminary site
investigation. The detailed site report shall be based on site
inspections or other available information and prepared by a
registered civil engineer or engineering geologist.

b. The detailed site report shall recommend development
standards to assure that proposed alterations and structures are
properly designed to avoid or recognize hazards either identified
in the prelimimnary report or as the result of separate
investigations. The report should include standards for:

(1) development density and design;
(2) location and design of roads and driveways;
(3) Land grading practices, including standards for cuts and
fills and the proposed use and placement of excavated
material ;,
(4) vegetation removal and a revegetation plan;
(5) special foundation design (for example spread footings
with post.and piers), if required;
(6) management of storm water runoff during and after
construct ion.

3. Summary Findings and Conclusions-

The preliminary and detai.led site reports shall include the
following summary findings arid conclusion:

(a) The type of use proposed is reasonably protected from the
described hazards for the lifetime of the structure;
(b) The type of use proposed and the adverse effects it might
have on to life, property, and the natural environment;
(c) Measures necessary to protect the surrounding area from any
adverse effects of the proposed development;
(d) Per'iodic monitoring necessary to ensure recommended
development standards are implemented or monitoring necessary for
the long-term success of the development.

D.ATE DU"E

3 6668 14107 6499