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

                          A System Of Classifying & Identifying
                          Oi'egonrs Coastal Beaches & Dunes

                                                                                             Z"', Ng

                                                                                            "'K
                                                                                                                                               @m4'k
                                                                                            "i"WIPAM
                                                                                            lzzg
                                                                Vy

                          @Iw

                                                                                                                                                       ',N

                              Z1,4A, A

                                                                                           p ga,
                                                                   W51- - @   - I             @5""i
                                                                                  owt
                          GB
                          454
                                                                    '77
                           B3
                                                                     77".,

                          C7
                          1979                                                     Oregon   Coastal    Z one  Management      Association,     I nc.

                This report was prepared as part of a larger document addressing various
                beach and dune planning and management considerations and techniques.
                Other segments of the document and additional materials are:

                      I. BACKGROUND ON BEACH AND DUNE PLANNING:
                         Background of the Study
                         An Introduction to Beach and Dune Physical and Biological Processes
                         Beach and Dune Planning and Management on the Oregon Coast: A
                         Summary of the State-of-the-Arts
                     II. BEACH AND DUNE IDENTIFICATION:
                         A System of Classifying and Identifying Oregon's Coastal Beaches
                         and Dunes

                    III. PHYSICAL AND BIOLOGICAL CONSIDERATIONS:
                         PhysicaZ Processes and Geologic Hazards on the Oregon Coast
                         Critical Species and Habitats of Oregon's Coastal Beaches and
                         Dunes

                     IV. MANAGEMENT CONSIDERATIONS:
                         Dune Groundwater Planning and Management Considerations for the
                         Oregon Coast
                         Off-road Vehicle Planning and Management on the Oregon Coast
                         Sand Removal Planning and Management Considerations for the
                         Oregon Coast
                         Oregon's Coastal Beaches and Dunes: Uses, Impacts and Management
                         Considerations

                         Dune Stabilization and Restoration: Methods and Criteria
                      V. IMPLEMENTATION TECHNIQUES:                           I
                         Beach and Dune Irtiplementation Techniques: Findings-of-Fact
                         Beach and Dune Implementation Techniques: Site Investigation
                         Reports
                         Beach and Dune Implementation Techniques: Model Ordinances*
                     VI. ANNOTATED BIBLIOGRAPHY:
                         Beach and Dune PZanning and Management: An Annotated Bibliography
                    VII. EDUCATIONAL MATERIALS:
                         Slide show: Managing Oregon's Beaches and Dunes
                         Brochure: Planning and Managing Oregon's Coastal Beaches and Dunes

                *Prepared under separate contract between Oregon Department of Land Conserva-
                tion and Development and the Bureau of Governmental Research, Eugene,
                         Illustrations prepared by Lorraine Morgan, Newport, Oregon
                         Cover photo by Christianna Crook, Newport, Oregon

                                                    ftoperty of CSC Library

                                    A SYSTEM OF CLASSIFYING AND IDENTIFYING,
                                                         L
                                       OREGON'S COASTAL BEACHES AND DUNES

                                                U - 3 . DEPARTMENT OF COMMERCE NOAA
                                                COASTAL SERVICES CENTER
                                                2234 SOUTH HOBSON AVENUE
                                                CHARLESTON I SC 29405-2413

                                                       by
                                         Christianna Stachelrodt Crook

                                              Research Associate
                                      OCZMA, Beaches and Dunes Study Team

                                           Kathy Bridges Fitzpatrick
                                       Editor and Project Administrator

                               Oregon Coastal Zone Management Association, Inc.
                                313 S. W. 2nd Street, Suite C   P.O. Box 1033
                                        Newport, Oregon    -    97365

                                                  June, 1979

                        Funding for this study was provided by the Office of Coastal Zone
                   Management, National Oceanic and Atmospheric Administration, under
                   Section 306 of the Coastal Zone Management Act through the Oregon
                   Department of Land Conservation and Development.

          rz
          @5

                                                   PREFACE

                        The following report presents the results of an in-depth analysis
                   of beach and dune identification and classification systems conducted
                   by the Oregon Coastal Zone Management Association, Inc. This report
                   constitutes one element of an overall analysis of planning for and
                   managing beaches and dunes as required by Oregon's Beaches and Dunes
                   Goal.

                        This report was prepared by Christianna Crook, OCZMA Beaches and
                   Dunes Study Team Research Associate, with assigtance from other Study
                   Team members composed of Carl Lindberg, Project Director, Wilbur
                   Ternyik, Project Coordinator, Arlys Bernard, Project Secretary, and
                   Kathy Fitzpatrick, Project Administrator.

                        in addition, valuable review and comments were made by the Beaches
                   and Dunes Steering Committee composed of:

                        R. A. Corthell, U.S. Soil Conservation Service
                        Steve Stevens, U.S. Army Corps of Engineers
                        Sam Allison, Oregon Department of Water Resources
                        Peter Bond and John Phillips, Oregon Department of Transportation,
                             Parks and Recreation Division
                        Bob Cortright, Oregon Department of Land Conservation and Development
                        Jim Lauman, Oregon Department of Fish and Wildlife
                        Jim Sternbridge, Oregon Department of Soil and Water Conservation
                        Steve Felkins, Port of Coos Bay
                        Rainmar Bartl, Clatsop-Tillamook Intergovernmental Council
                        Gary Darnielle, Lane Council of Governments
                        Cathy Mecone, Coos-Curry Council of Governments
                        Marilyn Adkins, City of Florence Planning Department
                        Phil Bredesen, Lane County Planning Department
                        Steve Goeckritz, Tillamook County Planning Department
                        Oscar Granger, Lincoln County Planning Department
                        Curt Schneider, Clatsop County Planning Department

                        Additionally, OCZMA extends special appreciation to the following
                   individuals for their valuable input and direction and for their signifi-
                   cant contributions to this report:

                        Bill Burley, Program Biologist, The Oregon Natural Heritage Program
                             of the Nature Conservancy
                        Don Leach, District Conservationist, U.S.D.A., Soil Conservation
                             Service

                         Dr. Paul Komar, Department of Oceanography, Oregon State University
                         Cathy Mecone, Planning Research Associate, Coos-Curry Council of
                              Governments
                         Dr. Leonard Palmer, Department of Earth Science, Portland State
                           @ University
                        'Dr-. James Stembridge, Coastal Resource Specialist, Oregon State
                              Soil and Water Conservation Commission, and
                         Wilbur Ternyik', Owner/Operator, Wave Beachgrass Nurser'y

                         Finally, OCZMA expresses its sincere appreciation to the University
                    of Washington Press for permission to reprint illustrations from
                    Vascular Plants of the Pacific Northwest by C. Leo Hitchcock, et. al.,
                    (1955-1969).

                                                    TABLE OF CONTENTS

                      Chapter                                                                   Page

                                Preface   ................................................         i
                                List of Figurgs    ........................................      iv
                          1.    Introduction    ...........................................        1

                         Ii.    Beach   ..................................................         1

                        III.    Foredune   ...............................................       10,

                         IV.    Interdune Forms    ........................................      26

                                A. Deflation Plain
                                B. Seasonally Wet Interdune Area
                          V.    Interior Dune Forms - Vegetated      ........................    46
                                A. Hummock Dunes
                                B. Surface Stabilized Dunes
                                C. Older Stable Dunes
                                D. Parallel-Ridge Dunes
                         Vi.    Interior Dunes - Nonvegetated      ..........................    73
                                A. Transverse-ridge Dunes
                                B. Oblique-ridge Dunes
                                C. Recently Reactivated Forms
                        Vii.    Glossary of Terms    ......................................      91

                                                      LIST OF FIGURES

                      Figure                                                                     La2e

                         1.      Steepened profile characteristic of an eroding
                                 beach   .................................................          2

                         2.      Beach cusps    ...........................................         3

                         3.      Sand deposition around a beach grass windbreak         ........  10

                         4.      As European beachgrass is buried, new shoot and
                                 root growth develops at the dune surface        ..............   11

                         5.      Beach,  foredune and deflation plain supply sand
                                 to interior open sand areas     ....................   I ......  73

                         6.      Transverse-ridge dunes form approximately
                                 perpendicular to northwest summer winds                  ......  74

                         7.      Oblique-ridge dunes form obliquely to both
                                 northwest and southwest dominant seasonal winds         .......  78

                         8.      Accumulation and advance of the oblique-ridge
                                 dune   ..................................................        79

                         9.      The ridge position of the oblique dune is modified
                                 by smonal winds       .....................................      79
                        10.      Transverse-ridge dunes riding up over the flanks
                                 of an oblique-ridge dune which terminates in a
                                 precipitation-ridge     ...................................      80

                        11.      Eastward expansion of deflation plain       .................    82

                        12.      Small blowout within beach grass environment        ..........   86

                        13.      Parabola blowout moving through forested dunes         ........  88

                                                               iv

                                                I. INTRODUCTION

                          Beaches and dunes are found on those accumulations of sand which
                    occur intermittently along  the Oregon coast. They range in size from
                    small pocket beaches between headlands to expansive dune sheets more
                    than twenty miles long and three to four miles wide. Varying combina-
                    tions of physical factors (e.g. wind, vegetation, and moisture, etc.)
                    are capable of producing widely diverse beach and dune landforms. Each
                    landform exhibits discrete physical capabilities as well as characteris-
                    tic sensitivies to man's activities.

                          Dune forms exhibit varying states of stability. Areas of open sand
                    occur where dune topography is controlled only by sand and wind. Lightly
                    vegetated areas are considered to be in an active state and are continu-
                    ously subject to erosion and accretion. Dunes are conditionally stabilized
                    when they have sufficient vegetative cover to withstand wind erosion.
                    Other dune forms can be surface stabilized or older (semi-cemented)
                    stable. That is, they may exhibit vegetation with a thin layer of soil,
                    or may have vegetation and extensive soil layer with semi-cemented
                    underlying sands.
                          This report classifies, describes and discusses the physical and
                    biological nature and general capabilities of coastal Oregon sand
                    landform types. In addition, a checklist of physical and biological
                    features characteristic of each type is included to assist with field
                    identification. A glossary of terms used in this report is presented
                    in the concluding section.

                                                    II. BEACH

                          A relatively narrow, sloping zone of unconsolidated materials
                          extending from the low tide line Landward to the uppermost
                          line of effective wave or tidal action.

                                                A. Geomorphology

                          Beach materials range in size from fine sand, to pebbles and even
                    small boulders and are supolied from the erosion of coastal cliffs, the
                    reworking of ancient and recent coastal sand deposits, and from riverine
                    sediment loads. Sand supply and beach formation processes occur in
                    seasonal cycles in which beaches commonly experience sand removal
                    during the winter and are rebuilt by the more gentle wave action
                    associated with summer weather activity. Beaches are the coastline's

                          1Illustrations indicate the degree of magnification or reduction.

                                                        2

                    primary defense against the erosive action of storm waves.

                         Sand dunes, cliffs and drift log accumulations may occur at the
                    landward side of beaches. Some parts of the coastline are repeatedly
                    interrupted with headlands, creating small pockets of cobble beaches.
                    Elsewhere the seaward margins of vast dune sheets create extensive
                    beaches.

                                              1. Stable beaches

                         In terms of sand availability, beaches may be stable, eroding or
                    accreting. A stable form is one which experiences neither a net loss
                    nor gain in beach materials on an annual basis. Gentle summer waves
                    replace the same amount of sand on the beach as was lost offshore during
                    winter storms. Beaches which are presently stable include Sand Lake in
                    Tillamook County and the region between the mouth of the Umpqua in
                    Douglas County and mouth of the Coquille River in Coos County.

                                              2. Eroding beaches

                         An eroding beach is one which annually experiences net sand loss.
                    This can result from continuous excessive erosion, diminishing beach
                    sand supplies, or both. Erosion occurs primarily during vigorous winter
                    storms and may be heightened by such factors as a high spring tide
                    which effectively increases wave height. A reduction in beach sand supply
                    may result from dams, riprap, jetties, commercial removal, or other
                    structures or activities which modify beach material transport or near
                    shore currents.

                         Eroding beaches can often be recognized in their earlier stages
                    by the development of a steeper than usual profile (Figure 1). Some

                                  Figure 1. Steepened profile characteristic of
                        an eroding beach.

                                                         3

                     eroding beaches may contain noticeable eroded embayments, or cusps,
                     which are the result of local rip currents carrying sand away from the
                     beach (Figure 2). Beaches presently in an eroding state include the
                     beach from Peter Iredale Park, north to the Columbia River south jetty
                     in Clatsop County and the area between Blacklock Point and Floras Lake
                     in Curry County.

                                                                          4

                                    Figure 2. Beach  cusps.

                                              3. Accreting.beaches

                          Any beach which has a low-tide margin experiencing net seaward
                     growth due to an annual increase in sand supply is considered to be
                     accreting. The development of small persistent dunes seaward of the
                     foredune is indicative of this sand accumulation process. With continued
                     accretion, the developing dunes will eventually grow and join to form a
                     new foredune seaward of the previous one. Accretion at a site may be
                     the result of escalated erosion elsewhere, beach or spit migration,
                     natural and/or induced changes in off-shore currents, or structures
                     and activities which modify beach material transport. To a limited
                     extent, a beach may experience accretion due to the sand-trapping
                     ability of dune grass. This is only likely to occur, however, when the
                     near shore environment already favors accretion. Examples of accreting
                     beaches include the area adjacent to the community of Surf Pines in
                     Clatsop County, the north end of South Beach in Lincoln County, and
                     just north of Gold Beach in Curry County.

                                                         4

                                                 B. Vegetation

                         High winds, waves. and cyclic tidal inundation'severely restrict
                    vegetative growth in the beach zone. However, many types of seeds
                    germinate easily in wet sand and a few hardy species may be found on
                    the higher beach slopes in the summer and fall.(Wiedeman, et. al.,
                    1974, P. 25Y. Such plants are not found growing in great profusion.
                    In fact, it may be that only one or two species, if any, will occur in
                    a given beach area. These may occur as isolated individuals, and will
                    commonly experience burial or destruction during the period of winter
                    storms.

                         Three species which occur most commonly on the beach include
                    American sea rocket (Cakile edentula), European sea rocket (Cakile
                    maritima) and honkenya                         Although not p'eculiar to
                                                                            h
                                                             arenaria), sea lyme-grass
                    beaches, European beachgrass Ammophila
                    (Elymus, mollis) and seashore bluegrass (Poa macrantha) are occasionally
                    found in this zone.

                                         C. Attractions and Limitations

                         The beach is a  highly attractive site for numerous recreational
                    activities ranging from beachcombing to operation of off-road vehicles.
                    It lends itself well to both solitary and group activities and, as a
                    geologic feature, seems to be relatively tolerant of most transient
                    activities. Management of this landform should consider such issues
                    as (1) the desirability of allowing vehicle traffic and significant
                    pedestrian use in the same areas, and (2) harrassment of shore bird
                    species by various recreational activities..

                                         .D. Identification Checklist

                         The beach  can be recognized by the following characteristics:'

                                                          5

                    1. The landward boundary of the beach may be characterized by one of
                         the following:
                         a. drift log accumulations,

                                                                     @7'
                                                        TRIM,     "'9'

                                                                         TZ"

                         b. foredune ridge, or

                                                             11
                                                        I'O'gPFI@"

                                                           M
                                                             AW
                                                            M MISR

                                                          6

                        C   Cliffs

                                                                                  VI-

                    2. Beaches may consist of fine to medium grained    sands and  exhi,bit a
                        relatively gentle  slope.

                                                                             Y@

                                                                               MM@,@

                                                              7

                      3. A steeper slope profile is exhibited by those beaches which consist
                          of pebbles and/or boulders.

                      4. Erosion is sometimes caused by stationary rip-currents which eat
                          embayments or cusps into the beach and foredune.

                                         @:@ . ... .......         MM@,

                                                                      ia 11 i I It!! i@,V
                                                                &

                                                          8

                     5. Accreting beaches may often be recognized by the development of
                         embryo dunes seaward of the foredune.

                            MAN"I'M

                                                                       'AIM 697,
                                                                           A,@

                                          M
                                            Z        W@k

                     6. The most commonly occurring beach vegetation includes the following:

                         a. American sea rocket (Cakile edentula),

                                                                                  flowers    purple
                                                                                     to white

                                                         9

                         b. European sea rocket (Cakile  maritima), similar to Cakile edentula
                             except for the fruit, and'

                                                          IAV
                                                          r-

                         c. Honkenya (Honkenya peploides).

                                                                               flowers
                                                                   ;71            greenish to
                                                                                  white

                                                       10

                                                III. FOREDUNE

                         First ridge of sand situated immediateZy above the high tide
                         tine and paratleZ to the beach.

                                               A. Geomorphology

                         The present day foredune of the Oregon coast has developed primarily
                    in the last forty years as a result of the introduction of European beach-
                    grass (Ammophila arenaria). First introduced for sand stabilization in
                    the Coos Bay area in 1910 and the Clatsop Plains in 1935, this species
                    became naturalized to the coastal sand areas. It spread along the
                    coast forming a nearly continuous barrier ridge along the shore. Euro-
                    pean beachgrass prefers sites of continuous sand deposition. It grows
                    seaward until it is halted by wave action at the high tide line. Embryo
                    dunes form here at the landward edge of the beach in conjunction with
                    vegetation and drift log accumulations where the velocity of the wind
                    decreases suddenly, depositing the sand load (Figure 3). Continued

                                          010

                                  Figure 3. Sand deposition around a beach grass
                             windbreak.

                    deposition may lead to the burial of the original obstacle. The driftlogs
                    remain buried forming the base of the foredune but European beachgrass
                    (Ammophila arenaria) can survive seasonal sand burial of up to three feet
                    and for that reason is the primary foredune building agent. As sand
                    builds up around the base of the plant, new roots and shoots grow

                     from the stem joints (Figure 4). This traps more wind-blown sand above,
                     while holding underlying sand within the complicated root network below.

                                   Figure 4. As European beachgrass is buried, new
                             .shoot and root growth develops at the dune 'surface.

                         The dune thus increases in height and width until it merges with
                     adjoining dunes to form a barrier ridge along the upper beach. This
                     dune-ridge area stops and holds most of the sand blowing in from the
                     beach and continues to grow until it reaches the maximum height
                     dictated by local conditions, usually up to twenty-five or thirty feet.
                     It may be bounded on the east by deflation plains, interior dunes,
                     cliffs, marshes, lakes or estuaries.

                          The foredune is a naturally occurring geomorphic feature which, to
                     some degree, acts as a dike during ocean storms. It's function transcends
                     that of a simple barrier-wall because it has a sponge-like ability to
                     absorb and mute the force of storm waves. Hitting the foredune, wave
                     energy is dissipated over, around and, most critically into the dune.
                     However, while it can act as an effective shock absorber, the foredune
                     can occasionally sustain considerable damage during storms and may be
                     unable to provide sufficient storm protection to inland sites, thus
                     allowing adjacent deflation plains or hummock dunes to be exposed to
                     the full force of maritime storms. In such instances, the area of
                     potential hazard is extended beyond the foredune to include additional
                     inland sites. Any excavation into, or construction modification of
                     the foredune may increase this hazard potential.

                                                        12

                         Foredunes are among the most dynamic of landforms and will naturally
                    vacillate between periods of being active (subject to wind and wave
                    erosion and breaching) and being conditionally stable (wind stable but
                    subject to wave erosion and breaching).

                         The term "foredune" is applied to this dune ridge wherever it
                    occurs along the Oregon coast. This feature varies considerably in
                    appearance, however, and to some degree in function, between the north
                    coast (Clatsop County) and the central-south region.

                         The foredune ridge which occurs. in the central and southern counties
                    commonly varies between ten to thirty feet in height, is twenty to
                    fifty feet wide at the base and often appears as a distinctive sea-wall
                    ridge particularly when viewed from the beach. Storm hazard in this
                    area is primarily associated with erosive storm waves and wind, impact
                    from solid debris carried by the waves, and flooding of inland sites.

                         The foredune in the Clatsop area is commonly an extremely broad,
                    low appearing feature. While it may reach heights of more than twenty-
                    five feet, the gradient is so gentle, often five degrees or less, that it
                    has a less distinctive sea-wall appearance. Storm hazard on the north
                    coast (north of Seaside) is more commonly associated with inundation from
                    sand than from erosion or debris impact, Wave run-up may be considerably
                    reduced by the extensive traverse associated with the long, shallow,
                    off-shore area and the extreme width of the foredune. However, storm-
                    velocity winds are capable of transporting generous quantities of sand
                    available in this region considerably inland. The gentle gradient
                    common to Clatsop foredunes may also offer less obstruction to the wind.
                    Thus, the "functional" width of the foredune (or the area impacted by
                    maritime storms) in the Clatsop area can be as great as 800 feet
                    depending on local conditions (Leach, 1978). The "foredune" under this
                    designation, may contain more than one "ridge" so the term "foredune
                    area" may be more applicable (Ternyik, 1978). Furthermore, while storm
                    associated sand deposition can cause sand-blasting type damage and may
                    result in subsequent excavation costs, this activity may be more aptly
                    designated as "nuisance" rather than true "hazard" to life or property.

                                              1. Active foredunes

                         Sand dunes are in an active state when they possess insufficient
                    vegetative cover to retard wind erosion. In this condition the sand
                    dune is experiencing active accretion and/or erosion.

                         On a static or accreting beach, an active foredune will commonly
                    evolve towards the conditionally stable state. As the active foredune
                    grows in height (up to thirty feet), it becomes an increasingly effective
                    barrier and progressively less sand is deposited on the lee side of the
                    dune and other sites inland. This offers somewhat greater protection
                    from storm winds, but also seriously limits all fresh beach sand supplies
                    to interior open sand areas.

                                                        13

                         Active foredunes may be most numerous in central and north coast
                    areas. They occur, for example, in Clatsop County west of Slusher and
                    Sunset Lakes and in Tillamook County at Neskowin North.

                                      2. Conditionally stable foredunes'

                         When foredunes exhibit sufficient vegetative cover to retard the
                    erosive effects of the wind, they are termed conditionally stable,
                    Obviously, the stability of a given foredune is conditional u*Pon the
                    maintenance of the vegetative cover.

                         While the conditionally stable foredune may not have any greater
                    resistance to wave erosion than does an active foredune, it appears to
                    recover more quickly from wave overtopping (Ternyik, 1978). However,
                    any conditionally stable sand dune is prone to reactivation upon
                    disturbance of the vegetative cover.

                         Examples of conditionally stable foredunes presently occur between
                    Sunset beach and Gearhart in Clatsop County and at the community of
                    Bayshore in Lincoln County.

                                                 B .Vegetation

                                              1. Active foredunes

                         The active foredune  receives such a substantial sand supply that
                    it is occupied almost exclusively by European beachgrass (Ammophila
                    arenaria). Some native dune grasses such as sea lyme-grass (@@us
                    mollis) may be found here but occur less commonly as they are less
                    tolerant of continual sand burial.

                                      2. Conditionally stable foredunes

                         The increasing height of the conditionally stable foredune restricts
                    the inland passage of salt spray and sand. A new environment is thus
                    created on the crest and the lee side of the foredune which is reflected
                    in the vegetation at this site. European beachgrass (Ammophila arenaria),
                    the most significant species which occurs on the foredune, becomes less
                    important because it prefers the more fertile sites of sand deposition.
                    Other species less tolerant of salt spray and sand deposition become
                    established. The first to become established include, among others, such
                    herbs as beachpea (Lathyrus japonicus), coast strawberry (Fragaria
                    chiloensis) and seashore lupine (Lupinus littoralis), Later successional
                    species may include such woody shrubs as salal (Gaultheria shallon), or
                    kinnikinnick (Arctostaphylos uva-ursi) and an occasional shore pine
                    (Pinus contort-aT

                                                          14

                          The lee side of a foredune may exhibit vegetation characteristic
                     of conditional stabi'lity and yet be experiencing erosion and undercutting
                     on its windward side. Such circumstances indicate that the foredune was
                     formerly in a conditionally stable state long enough for some vegetative
                     succession to take place, and has only recently begun to experience
                     erosion. The remaining foredune ridge has apparently been able to
                     provide sufficient protection to the lee side to maintain existing
                     vegetation. Should the oceanward side experience temporary in-filling
                     with logs, sand and beach grass during the summer it could deceptively
                     give the appearance of a completely conditionally stable foredune.

                                          C. Attractions and Limitations

                          While the foredune may not be a primary recreational attraction in
                     itself, it nonetheless experiences moderate recreational traffic. This
                     is partially because it is a barrier which must be traversed in order to
                     reach the beach. It is also used as a sheltered 'base camp' from which
                     forays to the beach are made. However, because of its hummocky, semi-
                     stable surface and the sharp tips of the European beachgrass, pedestrian
                     traffic usually follows open pathways. This activity, referred to as
                     "trailing", results in the development of open mobile sand trails.
                     However, the continual replenishment of fresh sand in active dune areas
                     commonly maintains sufficient fertility for beach grass regeneration.
                     Thus, trailing is not necessarily a serious problem unless it is
                     desirable for the active foredune to become conditionally stable
                     (OCCOC, 1975). Conversely, the trailing which results from the
                     passage of motorbikes and other off-road vehicles inhibits beach      grass
                     regeneration and creates troughs from which blowouts can develop.

                          The proximity of this landform to the ocean renders it at once
                     highly attractive and yet extremely hazardous as a site for permanent
                     structures. Construction of permanent structures which either project
                     onto the beach or require any excavation of the foredune endangers the
                     site and adjacent areas. Erosion intensification, interruption of
                     natural sand movement, and wind-blown mobile sands are potential hazards
                     associated with such disturbance. Additionally, the installation of
                     riprap to protect structures impedes the natural flow of beach and
                     foredune materials, possibly resulting in beach starvation at the site
                     or elsewhere. Goal 18 specifically addresses the problem of development
                     on active and other foredunes. No active dune, by definition, should
                     harbor permanent structures as they may be subject to inundation or
                     undermining due to moving sand. Permanent structures should be reserved
                     for permanent landforms. Management of this landform should consider
                     the highly dynamic mobile nature of this land/sea interface area.

                                                       15

                                         D. Identification Checklist

                         The foredune can be identified by the following characteristics:

                    1. A sparsely or thickly vegetated sand dune ridge five to twenty-five
                        feet high, running parallel to the beach.

                    2. The foredune is bordered by the beach and possibly drift logs on the
                        west.

                          0,

                                                                                     VP

                                             "X

                                            n-@

                                                                16

                       3. It commonly occurs adjacent to:

                            a.  hummoc k dunes, or

                                                4-

                            b.   the deflation   plain  on the  east.

                                      4"X"@

                                                                    . .........

                                                               N

                                                                        A
                                     iv

                                                         17

                     4. The active foredune may exhibit storm surge cuts. Logs and debris
                         may be found here.

                                                                                    j,
                                                                              M,O'
                                                                                     MW

                                                              V""

                                                                 @'P

                     5. An eroding, formerly conditionally   stable foredune may continue to
                         exhibit vegetation characteristics  of its conditionally stable
                         state. (Coast strawberry is shown   on the eroding face of a
                         formerly conditionally stable foredune.)

                                         ........ ...

                                     OF
                                   M

                                                       18

                   6. Drift logs may be exposed at the base of the windward face of the
                       active foredune, particularly in the winter.

                                                       IM

                                              '-ft'M

                   7. The vegetative cover of   the active foredune is rather sparse and
                       consists almost exclusively of European beachgrass (Ammophila
                       arenaria).

                                                        19

                     8. The conditionally stable foredune exhibits a very dense vegetative
                         cover.

                     9. Sea lyme-grass (Elymus mollis) may also occur occasionally on the
                         foredune in lesser amounts.

                                                                           1/3

                                                       20

                    10. Species of the pioneer community found on the lee side of the
                         conditionally stable foredune include:

                         a. coast strawberry (Fragaria chiloensis),

                                                                           flowers   white to
                                                                              pinkish

                                                            V2

                        b.  beach morning-glory (Convolvulus soldanella),

                                                                                flowers   light pfnk
                                                              v                    to rose

                                           @2

                                                        21

                     c. beachpea (Lathyrus japonicus),  and

                                                             ;b

                                      flowers
                                          violet

                    d. gray beachpea (Lathyrus littoralis).

                                                                               flowers   white
                                                                                  to pink or
                                                                                  purple

                                                       22

                    11.  Four species appearing later in succession include:

                         a. seashore lupine (Lupinus littoralis),

                                                                          flowers   purplish
                                                                              blue

                         b. seaside tansy (Tanacetum  douglasii),

                                                                          flowers   yellow

                                                         2/5

                                               3.2            3.2.

                                                       23

                     c. western bracken fern (Pteridium aquilinum)

                                          @20

                                                                     112

                     d. pearly everlasting (Anaphalis margaritacea)

                                                                      heads   white

                                                        24

                    12. By the time the later successional species appear, many of the
                         pioneer species are no longer apparent. The following shrub species
                         belong to this latter successional group:

                         a. salal (Gaultheria shallon

                                                  Ul@
                   fruit
                    dark purple
                    to black'                                                         flowers
                                                                                       white  to pink

                                    @2

                         b. evergreen  huckleberry  (Vaccinium ovatum),

                                                      @, 51i
                                                                                 flowers
                                                                                   white  to pink

                                                        25

                     c. kinnikinnick (Arctostaphylos uva-ursi)

                                                                                     flowers
                                                                                      white to
                                                                                      pink

                                              75

                    d. hairy manzanita (Arctostaphylos columbiana)

                                    112                         G;                 flowers white to
                                                                                     pale pink

                                                        17

                                                              1/2
                                  50          fl@

                                           fiPNI

                                                       26

                                             IV.  INTERDUNE FORMS

                         Interdune forms include those low areas between dunes which are
                    often subject to the controlling factors of wind action, and/or high
                    water table.

                                              A.  Deflation Plain

                         Eroad pLain which deveZops immediateZy inZand from the foredune
                         and is wind scoured to the ZeveZ of the summer water tabte.

                                               1. Geomorphology

                         A deflation plain is created by wind removal of dry sand particles
                    inland from the foredune. Sand is thus removed only down to the lowered
                    summer water table, because groundwater moisture binds sand particles
                    together at this level. This may result in standing water during the
                    winter when the water table is naturally higher. Sand transported inland
                    from the deflation plain is deposited in interior dune regions.
                    The best conditions for development of this landform probably occur
                    behind a conditionally stable foredune, where the inland flow  of sand,
                    which could otherwise contribute to dunal development at this  site, is
                    cut off and the wind has more available energy for transport. If an
                    active foredune exists, sand supplies are more readily passed  over the
                    ridge to form hummock dunes or open-sand dunes.

                         Examples of old, inactive deflation plains occur in some  areas
                    considerably inland from the foredune area. These are commonly
                    occupied by forest communities and the water table is still quite high.
                    These features probably developed adjacent to a foredune, but merged
                    inland by subsequent beach accretion.

                                                2. Vegetation

                         Components of the vegetation communities in the deflation plain
                    vary according to specific site factors and the stage of successional
                    development. In the early successional stages, grass, rush, and
                    sedge communities occupy progressively wetter sites. Later successional
                    stages are characterized by a low scattered shrub community, followed
                    by the development of tall shrub thickets and eventually a shore pine
                    forest (U.S.D.A., 1972, pp. 84-98). Water stands at, or near the surface
                    most of the year in these sites.

                         The grass community occurs where water stands on the surface for
                    two to three months of the year (vegetation covers about 80% of the
                    ground). A few scattered shrubs and dwarfed shore pine are occasionally
                    found in this community.

                                                        27

                         The rush community is found in sites where the water table stands
                    on the surface for three or four months of the year (vegetation covers
                    about 90% of the ground). Isolated shrub and tree seedlings also occur
                    here. Coast willow (Salix hookeriana) seedlings are the most numerous.

                         Water stands on the surfa ce of the sedge community for at least
                    six months of the year. Vegetation covers about 95% of the ground.

                                        3. Attractions and limitations

                         The primary attractions of the deflation plain appear to be the
                    viewing of waterfowl and, when drained, the development of housing.
                    Many deflation plain marsh communities provide habitat for a number of
                    waterfowl, which is lost when the site is developed. Even when drained,
                    the water table remains quite high and septic tanks, drainfields, and
                    other buried structures may not be appropriate. Flotation and failure
                    of such structures could occur with resulting pollution,

                                         4. Identification check-list

                         The deflation plain may be identified by the following features:

                    1. It is a low plain bordered on its ocean side by a foredune.

                                          44,

                                           0

                                              2

                                                                 28

                       2. The deflation plain may be bordered on the eastern boundary by:

                            a. hummock dunes or,

                            b. transverse-ridge      dunes.

                                                                          0
                                                                                   @'S

                                                                    ..........

                                                                                          "
                                                                                           J"'I"M11"IrIND TRIZZ"!
                                                                                           N'WN" ' ,                      I
                                                                                                  MI

                                                       29

                     3. It may contain standing water several months of the year.

                    4. Important species of the deflation plain grass community include:

                        a. European beachgrass (Ammophila arenaria),

                                                                 12
                                                               lodicu)es

                                                  "'10

                                                       30

                    b.  seashore lupine (Lupinus littoralis)

                                                                          flowers   purplis-h blue

                              V2

                    c. false dandelion (Hypochoeris radicata)

                                     1.6

                                                                                 flowers   yellow

                                                       31

                    d. coast strawberry (Fragaria chiloensis)

                                                                             flowers   white
                                                                               to pinkish
                                                            rXI

                                                                 "2

                    e. yellow-eyed grass (Sisyrinchium californicum)

                         flowers   yellow

                                                                                       1/3

                                                 1/3

                                                      32

                    5. The following plants are most common in the rush community:

                        a. spring-bank clover (Trifolium wormskjoldii).

                                                                      flowers - purplish-red
                                                                        often white-tipped

                                                         2.5

                        b. Rushes are important here. (They may be identified by a round
                            stem.)

                            (1) sickle-leaved rush (Juncus falcatus)

                                                                  - rI
                                          4
                                                                1
                                                                    20
                                                                1@", YS
                                                                wd

                                                                  1/3

                                                       33

                            (2) brown-headed rush (Juncus nevadensis)

                    6. The most important species of the sedge community are:
                        a. Sedges (which have stems with edges) are the most critical
                            species. They include:

                            (1) slough sedge (Carex obnupta)

                                                                                      1/3

                                                          34

                                                    indsi i
                      (2)   hindi s sedge (CaLe-x--hl 1

                                                               paci f i ca)
                     b    Pacific silver   weed (Pote  it i I I -a-P--(

                                                                                    flowers    bright yellow

                                                        35

                    C. creeping buttercup (Ranunculus  flammula)

                                                                                     flowers
                                                                                       yellow

                    d. king's gentium (Gentiana sceptrum)

                                                                           flowers   blue to
                                                                             pur.plish-blue

                                                 1.2

                                                       36

                    7. The low, scattered shrub community is characterized by the following
                        species up to six feet in height:

                        a. coast willow (Salix hookeriana) dominates,

                                                    V

                        b. salal (Gaultheria shallon),

                                             1

                                                                                   flowers
                                                                                    white to pink

                                   @2

                               41

                                                       37

                    c. evergreen huckleberry (Vaccinium ovatum),

                                                                             flowers - white
                                                                               to pink

                    d. wax myrtle (Myrica californica),  and

                                                                              fruit   reddish-
                                                                                 brown

                                                    "2

                                                        38

                         e. shorepine saplings (Pinus contorta).

                                                                                     V2

                     8.  The tall shrub thickets follow the low, scattered shrub association
                         and is composed of the foregoing shrubs and trees ranging in height
                         from s'ix to twenty feet.

                     9.  The next successional stage on the deflation plain is the shorepine
                         forest. The plant community includes the following:

                         a. shorepine dominates (Pinus contorta). See drawing above.

                                                        39

                    b. sitka spruce (Picea sitchensis)

                                                                    411

                                                      J,         14-             '12

                    c. occasionally trees of:

                         (1) wax myrtle (Myrica californica), and

                                                                   00"

                                                        40

                       (2) coast willow (Salix hookeriana)

                                                           C
                                                          J,

                    d. a sparce occurrence of shrubs:
                       (1) salal (Gaultheria shallon), and
                                           P
                                           VVJ
                                            -Y11
                                                                                    flowers
                                                                                     white to pink
                                                , wll@
                                            A

                                      IIt

                                                          41

                               evergreen huckleberry (Vaccinium ovatum)

                                                                                     white to
                                                                           flowers
                                                                                      pink

                                                 4,

                     e. slough sedge (Carex obnupta) is common.

                                                                            1/3
                                         b"

                                                        42

                                        B. Seasonally Wet   Interdune Area

                          Interdune sites which are commonZy occupied by standing water
                          onZy part of the year.

                                                1. Geomorphology

                          Low lying sites which contain surface water during some part of the
                     winter are found in association with many sand landform types. Swales
                     between oblique-ridge dunes, the basal area between hummock or trans-
                     verse-ridge dunes, and low areas within older stable dune units, all
                     provide examples of sites which may be wet part of the year. Water table
                     is probably high even during the summer when all trace of surface water
                     has disappeared.

                                                 2. Vegetation

                          Although the surface can range from bare sand through marsh associa-
                     tions to mature forest, some vegetative cover is most common. Any of
                     those communities occurring in the deflation plain may be found here.
                     Some sites may exhibit mottled clayey soils indicative of prolonged
                     saturation.

                                         3. Attractions and limitations

                          Characteristic attractions and limitations of these sites would
                     be similar to those of the deflation plain. Any development proposals
                     for occasionally wet areas in older stable dune forms should address
                     the potential water table limitations here.

                                          4. Identification check-list

                          Occasionally wet interdune sites may be identified by the following
                     characteristics:

                                                                                                43

                                 1. The site exhibits standing surface water during only                                                part of the

                                                                                                           -7-

                                                                                                                                           Mp,,@
                                                                                                                                                 54
                                                                                                                                              "Vv 'W
                                                                                                                                          j,"alp
                                                                                                                                                "N
                                                                                                                                                  a,

                                                                                                                                      IV
                                                       "I q

                                 2. Occasionally wet interdune areas                                may occur as follows:

                                        a. vegetated areas between open                             sand dune ridges,

                                                                                                    @7'7111_1 "I

                                                                 .. ... ..... M, l,'W
                                                                                                      . . . . . ......

                                                                                                   ;,77@

                                                                                                         Of

                                                                    J116

                                                      44

                   b. nonvegetated sites between open sand dune ridges, or

                                     "IN

                   c. swales between  parallel-ridge dunes,

                                                          45

                     d. low sites in older forested dunes (may   be affected by underlying
                          impermeable iron lenses), or

                     e. swales   between hummock dunes which may be a functional extension of
                         the adjacent deflation  plain.

                             W*

                                           N

                                                          46

                                      V. INTERIOR DUNE FORMS - VEGETATED

                                               A. Hummock Dunes

                         FieZds of vegetated sand dune mounds most commonZy occuring
                         inZand from the foredune or defZation pZain.

                                                1. Geomorphology

                         Hummock dunes, like the foredune, are primarily created by the
                     mound building activities of European beachgrass (Ammophila arenaria).
                     These dunes form as fields of hillocks rather than linear ridges because
                     there is no natural linear vegetation and sand accumulation boundary
                     (such as the beach), and sand supply and wind patterns are rendered
                     inconsistent and discontinuous by the foredune barrier ridge.

                         Hummock dunes most commonly occur either immediately inland from
                     the active foredune or inland from the deflation plain. Sand is supplied
                     from either or both of these source regions. Patches of hummock dunes
                     are also found within open sand areas on occasion. In general, hummock
                     dunes range from ten to thirty feet in height and twenty to thirty feet
                     at the base. In their active form they may be only sparcely vegetated
                     and thus actively migrating. Active hummock dunes occur in the south-
                     western region of Bayocean Spit in Tillamook County and west of Lily
                     Lake in Lane County. A vegetative cover sufficient to make hummock
                     dunes wind stable creates a conditionally stable form, examples of which
                     are found at the north end of Bayocean Spit in Tillamook County and at
                     South Beach in Lincoln County.

                                                2. Vegetati'on

                         The most prevalent vegetation found on hummock dunes is European
                     beachgrass (Ammophila arenaria). Other secondary components include
                     seashore lupine (Lupinus littoralis), seashore bluegrass (Poa macrantha),
                     and coast strawberry (Fragaria chiloensis). Later successional growth
                     is similar to that on the lee side of the conditionally stable foredune
                     and may frequently exhibit shrubs or dwarfed trees in the more protected
                     sites. The depressions in those hummock dune areas which have a high
                     winter water table may be occupied by marsh vegetation including sedges
                     and rushes.

                                        3. Attractions and limitations

                         This area has attractions to both pedestrian and off-road vehicle
                     recreation. Some areas have been used for home sites.

                                                         47

                         The proximity of active hummock dunes to the active foredune and
                    their natural interaction is of critical importance. Often one blends
                    into the other imperceptably and the boundary is somewhat hypothetical.
                    One cannot be managed in isolation from another.

                         Hummock areas are often used by off-road vehicle recreationalists
                    but limited visibility can create hazards, particularl for pedestrians.
                                                                          y

                         Those areas which have a high winter water table may develop
                    "quicksand-like" conditions in the low areas (U.S.D.A., 1972, p. 76).
                    High water table areas are also highly sensitive to development and
                    would be particularly unsuitable for either spotic tanks or buried
                    pipelines due to the possibility of structure flotation and failure
                    (Ibid, P. 83).

                         High wind scour and blowout potential also limit the development
                    possibilities of this dune landform. Stabilization planting should be
                    undertaken and consistently maintained during and after any construction.

                                         4. Identification check-list

                         Hummock dunes can be identified by the following characteristics:

                    1. Hummock dunes occur where clumps of vegetation cause deposition of
                        windblown sand

                                                            48

                     2. They occur as fields of individual, vegetated sand hummocks

                                                      ALAU.

                     3. Hummock dunes occur either:

                         a. leeward of an active foredune, or

                                                           M,

                                                           ........ ..

                                                                         49

                          b. inland     from the deflation plain,        or

                                                         At.

                                      @4'

                          c. in isolated hummock fields          within open sand areas.

                                                                               0, "POR
                                                                     6@'
                                                    "N"
                                                                        1411 "111,
                                                 @W&5111'
                                                                    @@Wgpgqi
                                                4p
                                                              , Y- "A
                                                               -vtM @!u
                                                                  0 NV

                                                        50

                   4. European beachgrass (Ammophila arenaria) forms the primary
                       component of the vegetation community of active hummocks.

                                                                          VA

                                                  12
                                                 lodicules

                                     '110

                                         A

                                                           51

                     5. Other species which may occur here include:               oft

                         a. sea lyme-grass (Elymus mollis)

                                    lo@
                                                                          113

                                                                              A
                                      'A

                                  20

                                     lodicules

                         b. seashore lupine (Lupinus littoralis)

                                               flowers
                                                   purD.l i sh-bl ue

                                '12

                                                        52

                   c. seashore bluegrass (Poa macrantha), and

                                    4

                                                                 1/3

                   d. coast strawberry (Fragaria chiloensis).

                                                                          flowers   white to
                                                                             pinkish

                                                                 V2

                                                         53

                        Hummock dune areas which have experienced prolonged successional
                        growth indicating conditional stability may display the following
                        species:

                        a. kinnikinnic (Arctostaphylos uva-ursi),

                                                                                   flowers
                                                                                    white to pink

                                            7.5                          @2

                        b. evergreen huckleberry (Vaccinium ovatum),

                                                                             flowers
                                                                              white to pink
                                50

                                                                                                54

                                  c. salal (Gaultheria shallon),

                                                                                                                                     flowers
                                                                                                                                        white to pink

                                                        Ix
                                                                          'k,@j z         '12
                                                         9                    6

                               d. shore         pine (Pinus contorta),                and

                                                   01

                                                                                                                         @2

                                                                                                            m -

                                                         55

                    e. sitka spruce (Picea sitchensis).

                                          B. Surface Stabilized Dunes

                        Dunes of any form which possess a weakZy developed thin soil
                        and underlying unconsolidated sands.

                                               1. Geomorphology

                        These dunes have been stabilized with vegetation long enough for
                    soil to begin forming. This process may have taken hundreds or possibly
                    a few thousand years.

                        Surface stable dunes are wind stable so long as the weakly developed
                    soil is not seriously disturbed. The underlying sand materials are prone
                    to reactivation, particularly if excavations are oriented toward pre-
                    vailing winds.  Parabola dunes commonly occur in this landform. Occasionally,
                    buried soils and iron bands may impede permeability. Surface stable
                    dunes occur in the central portion of the Tillamook Spit in Tillamook
                    County and are intersperced throughout the dune sheets in Lane, Douglas
                    and Coos Counties.

                                               2. Vegetation
                                                                                 2*

                        Forest associations occur most commonly in this unit although
                    meadow communities are not unknown. Native herbs, shrubs and trees, not

                    unlike the later successional species found on conditionally stable
                    foredunes, are found here although species proportions, size of
                    individuals and biomass density are considerably different, Because
                    of tho favorable environment provided by an abundance of moisture,
                    mild climates and surrounding forest productivity, coastal forests,
                    particularly the shrub layer, may be nearly impenetrable.

                                        3. Attractions and limitations

                         The forested surface-stabilized dunes offer attractive sites for a
                    number of man's activities because they are sheltered and somewhat more
                    stable than most other dune forms. Such reactional activities as camping
                    and picnicking, as well as the placement of dwellings and other structures,
                    are popular activities.

                         Caution must be used in developing these sites, however, because of
                    some inherent limitations. The dunes are only surface stabilized and are
                    prone to reactiviation if the surface vegetation and soil are disturbed.
                    Furthermore, windfallen trees are common along the edge of new clearings
                    posing potential hazard for develoPment.

                         Many surface stable dunes are underlain by older, buried soils and
                    iron lenses which restrict vertical permeability. This is typical of the
                    subsurface stratigraphy in open dune sand and older stable dunes as well.
                    Septic tank viability could be threatened by local high water due to these
                    impermeable lenses.

                         Water drawdown could also be a problem in this unit if stabilizing
                    vegetation is affected. Pollution of the groundwater is also a
                    potential problem for the development of this landform.

                                         4. Identification check-list

                         Surface-stable dunes can be identified by the following characteris-
                    tics:

                                                           57

                     1. Dunes having  a thin, weakly developed soil,

                                                                          -'F     -77

                     2. The sands underlying the soil   are unconsolidated and will  easily
                         reactivate with suffitient disturbance.

                                                 A-1

                                               A

                                                           58

                     3. Forests most commonly  cover the surface-stable dunes.

                                                                    '0 -20 _MN!

                                ir

                     4. The forested, surface-stable  dune  is characterized by the following
                         vegetation:
                         a. The understory may consist of,  W!
                             (1)  salal (Gaultheria          4
                                           shallon-)
                                                               /1
                              flowers - white
                                to pink

                                                  N, :?
                                                  @N

                                                    13          6

                                                                59
                                  western bracken fern (Pterldfum a Jflinum)

                                                      N    -@-Vlv

                                                         '-V KV@"""@

                                              @2 0

                                                                        '2
                         (3) tree 7UPine (Luoinus abore

                                                     flowers
                                         p                    yellow
                                                      rarely   white,
                                      Z5              b
                                                       luish or
                                                      Purp7ish

                                                                 I-N

                          2.5

                                 heel

                                                         60

                       (4) evergreen huckleberry (Vaccinium ovatum) and

                                                                           flowers   white to
                                                                              pink

                       (5) western  rhododendron (Rhododendron macrophyllum).

                                                                                flowers   pink
                                             1.2
                                                                                 to deep rose
                                                                                 rarely white

                                                         61

                       (6) The more open sites may contain kinnikinnick (Arctostaphylos
                            uva-ursi) and

                                                                                   flowers
                                                                                      white to pink

                                              T5                           @2

                       (7) hairy manzanita (Arctostaphylos columbiana).

                                                                        flowers   white to
                                                                              pale pink

                                                            62

                    b. The forest canopy consists primarily of shore pine (Pinus contorta)
                        but also may include:

                                                                P2

                                                                                 112

                       (1) Western hemlock (Tsuga heterophylla) in moist sites,

                                         IIM@ 'r,
                                                             017
                                                                        2
                                                      tl\

                                                                             i4

                                                       1/3

                                                          63

                      (2) sitka spruce (Picea sitchensis)

                                                                      40,

                       (3) douglas-fir (Pseudotsuga menziesii)

                                                              Xl@

                                                                             IZ

                                                         64

                      (4) western red cedar (Thuja plicata) and

                      (5) red alder (Alnus rubra)

                                                            A0.

                                                         65

                                            C. Older Stable Dunes

                       OZder sand dunes of any fo2wi which possess both a deep, weZZ-
                       deveZoped soit and moderateZy cemented underZying sand.

                                               1. Geomorphology

                       This dune type has bee'n stabilized with a vegetative cover long
                  enough for a relatively deep soil to develop and for the underlying
                  sands to acquire some stability. The sub-surface sands exhibit varying
                  degrees of cementation. The iron bands and buried soils which are found
                  in the surface stable dune occur more frequently here and are more
                  pervasive.

                       Although these sands will form a cliff where excavated, sloughing
                  and landsliding are common. This is often intensified when saturation
                  occurs due to subsurface impermeable iron lenses.

                       This landform may contain layers of loose sand overlyinq or underlyinq
                  the semi-cemented strata but it is wind stable throughout the cemented
                  layers.

                                                2. Vegetation

                       Forests, often the coastal climax forest, most commonly occur here
                  although natural grass areas may be found as well. The same species as
                  occur in the surface-stable dune classification also occur here. A
                  more even mixture of forest species is often found with less predominance
                  of shore pine, and the forest canopy may be more dense with a resulting
                  less dense shrub layer.

                                        3. Attractions and limitations

                       The older stable dune presents an attractive site for recreational
                  activities and residential development. The limitations associated with
                  mobile sands do not exist with this landform. When excavated, the
                  semi-cemented sands will maintain a cliff and are wind stable, However,
                  sloughing is common, particularly in the winter months. This tendency
                  is accentuated during groundwater recharge months by the impermeable iron
                  bands which commonly run horizontally through this unit. Infiltering
                  groundwater is concentrated above these bands, saturating the sands
                  causing collapse where cliffs exist. This same phenomenon, which forms
                  a perched water table, results in conditions highly unfavorable to
                  septic tank siting, consequently, septic tank failure is not uncommon in
                  this landforTn.

                                                         66

                                         4.  Identification check-list

                        Older stable dunes can be identified by the following characteristics:

                   1. The presence of a moderately well developed soil.

                                                   n1i,

                                                   "uM
                                              ..... ......

                                       5", Ri

                   2. The underlying sands are somewhat consolidated and often exhibit
                       horizontal iron bands which offer varying resistance to erosion and
                       impede vertical percolation of groundwater.

                                                         67

                   3. Underlying sands will form a cliff where cut, but sloughing is
                       common.

                  4.   Vegetation species which occur on the older-stable dune are essentially
                       the same as the surface-stable dune but species proportions vary.
                       Shore pine and salal are less dominant. The following species  are
                       common to this landform:

                       a. western rhododendron  (Rhododendron macrophyllum

                       flowers - pink to
                         deep rose, rarely white

                                                           68

                   b. western hemlock (Tsuqa heterophylla)

                    c. douglas-fir (Pseudotsuga menziesii)

                         AWK@-@
                                                     "Ali
                                                       IN

                                           1/3

                                                       69

                 d. sitka spruce (Picea sitchensis)

                                                                                     vm
                                                                                     W

                  e. -western red cedar (Thuga plicata)

                                                         '12

                                 V2

                                                          70

                                            D. Parallel-Ridge Dunes

                         AZtipZe sand dune ridges which occur more or Zess paraZleZ to,
                         and inZand from, the foredune.

                                                1. Geomorphology

                         Each ridge in a group of parallel-ridge dunes originally formed as a
                    foredune on an accreting beach. As the beach grew seaward, vegetation
                    advanced to keep pace with the upper beachline. New dune mounds and
                    eventually a new foredune developed oceanward of the previous one.
                    Continued accretion resulted in the eventual development of a series of
                    parallel ridges bordering the beach. The sand dunes of the Clatsop
                    Plains are classic examples of this type. Here the dunes are very broad,
                    gently sloping features aligned in a general north-south direction, paral-
                    lel to the beach. Other, often discontinuous examples occur in
                    association with accreting beach areas, such as in those areas of jetty
                    construction. Parallel-ridge dunes appear to be developing at the north
                    end of South Beach in Lincoln County. A very pronounced example of this
                    feature occurs adjacent to the north end of Heceta Beach in Lane County.
                    These are extremely steep ridges, unlike the Clatsop Plains variety.

                                                 2. Vegetation

                         Vegetation associations in parallel-ridge dunes become increasingly
                    diverse and mature progressing inland, and range from European beachgrass
                    (Ammophila arenaria) on the existing foredune, landward through native
                    herbs, shrubs and forest s.pecies, many of which have been planted through
                    sand stabilization projects (e.g. Clatsop Plains).

                                         3. Attractions and limitations

                         This landform probably has the same attractions and limitations as
                    conditionally sta-ble hummock dunes and surface stabilized dunes. Due
                    to reactivation of a major portion of the sand in the Clatsop Plains, most
                    examples of this landform are in a conditionally-stable state although
                    areas of surface-stabilized conditions do occur.

                                          4. Identification check-list

                         Parallel-ridge dunes can be identified by the following characteristics:

                                                                71

                     1. They occur in groups, running more or less parallel to the beach.

                                    'W

                                        Is

                     2. The Clatsop    Plains variety commonly possess a very     gentle angle of
                         slope, whereas limited occurrences on the central and south coast are
                         steeper.

                                "N."WENMR

                                                       "@Q
                                   ..........                                            S z"I",

                                                                                Ip J,
                                      'A 'Y    ... .....
                                ag

                                                            72

                     3. Because they occur in a region of accreting beaches, portions of a
                          newly forming foredune may occur seaward of the present foredune.

                         @Vwl
                                  IM

                                                                                        @'Tv

                                                            73

                                        VI. INTERIOR DUNES - NONVEGETATED

                         This category  includes those large areas of active sand which are
                    located primarily on the sand sheets (sand deposits of considerable depth
                    and breadth overlying subsurface coastal terraces) along the central
                    Oregon coast. These dunes are mostly vegetation free and therefore,
                    are formed primarily in response to wind and sand supply. Moisture and
                    topographic factors provide morphological controls of secondary importance.

                         The western boundary of open dune sand areas is generally located
                    east of the deflation plain, but is occasionally found immediately adjacent
                    to the foredune. The western section is essentially a nonvegetated
                    equivalent of the hummock dunes. Open sand areas derive their sand supply
                    from the deflation plain and foredune (Figure 5). However, open sand

                                   Figure 5. Beach, foredune and deflation plain supply
                               sand to interior open sand areas.

                    landforms  located downwind from conditionally stable foredunes or
                    vegetated  deflation plains could dwindle due to sand starvation because
                    little sand escapes beyond these well-vegetated landforms. Open sand
                    dunes move inland under the influence of onshore winds.while the sand
                    supply is.captured by the foredune. Consequently, open sand areas are
                    growing ever smaller, as increasingly large deflation plains are formed
                    in their wake.

                         The pattern of dune development and reactivation is nowhere more
                    complicated-than on the open sand sheets. Sand deposited in these areas
                    during Pleistocene and post-Pleistocene sea level fluctuations has been
                    "reworked" several times, varying from one area to another. Because
                    of this, buried soils, iron bands, islands of mature forest, and actively
                    eroding older dune strata are common features coexisting within active
                    sand areas.

                                                            74

                                            A. Transverse-ridge Dunes

                         Low northeast1southwest oriented, nonvegetated sand dune ridges
                         which most commonty migrate in a southeasterZy direction.

                                                 1. Geomorphology

                         Transverse-ridge dunes are primarily features of the summer environ-
                    ment. They are undula  'ting, sinuous ridges which are formed essentially
                    perpendicular to the northwest winds of summer and which are greatly
                    modified in shape during winter storms. Their orientation is northeast/
                    southwest; migration takes place in semi-parallel ridges moving in a
                    southeasterly direction (Figure 6).

                                     SA

                                     Figure 6. Transverse-ridge dunes form  approximately
                              perpendicular to northwest summer winds.

                         Transverse-ridge dunes are a low relief feature,   five to twenty
                    feet high composed of a gentle sloping windward face   (five to twenty-five
                    degrees) and a relatively steeper slip face (sixty to seventy degrees).
                    The distance between crests is highly variable, but generally ranges
                    between seventy-five and 150 feet. Where breaches occur, these dunes
                    reveal a highly complex interior cross-bedding. This feature is produced
                    when layers of sand from an advancing dune are deposited obliquely on
                    the dune in its path.

                      @ Transverse-ridge dunes occur in groups. They are commonly found on
                    the eastern fringe of  the deflation plain. However, Lund (1973) reports
                    that thirty years ago  transverse dunes often extended from the beach east

                                                         75

                   into the lower part of the oblique-ridge dunes, This occurred prior
                   to the introduction of European beachgrass (Ammoghila arenaria).

                        A zone of seasonally wet transverse-ridge dunes is often found on
                   the eastern fringe of a deflation plain with a high winter water table.
                   Transverse-ridge dunes commonly extend from the eastern edge of the
                   deflation plain into the zone of the massive oblique-ridge dunes, often
                   "riding" up over the surface of the latter.

                        Transverse-ridge dunes occur in Lane County on the major open sand
                   strip between the Siuslaw and Siltcoos rivers and on the open sand areas
                   west,of north Ten Mile Lake in Coos County.

                                                2. Vegetation

                        Although transverse-ridge dunes comprise a basically open dune sand
                   unit, isolated areas of vegetation may occur in the depressions between
                   crests. These are primarily associated with the deflation plain and will
                   consist of the various plant types associated with that landform.

                                        3. Attractions and limitations

                        This unit appears to be highly attractive to off-road vehicle users
                   and, to a lesser extent, pedestrian traffic. It has a high tolerance
                   level to most recreational activities, however, facilities such as
                   parking lots and road construction are not suited to this formation.
                   (In some cases stabilization plantings could render such developments
                   feasible; however, these are commonly relatively infertile sand areas
                   (U.S.D.A., 1972, p. 105).

                        Factors which could create hazards are occasional areas of quicksand
                   in wet depressions between transverse dune ridges, poor visibility in an
                   area used by both off-road vehicle enthusiasts and pedestrians, and
                   inundation or-undermining of structures by moving sand.

                                         4. Identification check-list

                        Transverse dunes may be identified by the following features:

                                                           76

                    1. This dune form occurs as a low (five to twenty-five foot) sinuous
                        ridge with a gently sloping (five to twentyfive degree) windward
                        face and a steeper (sixty to seventy degree) lee face.

                                                                         PIP.

                                                                        zi

                                                                   '77- 7 7 ", @7

                    2. Transverse-ridge  dunes exhibit a northeast/southwest trend and occur
                        in groups on the large, open sand areas along the south central coast.

                                                            77

                    3. Transverse-ridge dunes often ride    up over the western flanks of the
                        massive oblique-ridge dunes.

                    4. Marsh-type vegetation may occur between ridges where these dunes
                        overlap onto the deflation plain.

                                         .. ........

                                        @7 o"I

                                                                                 Mr,

                                            7,

                                                          78

                                            B. Oblique-Ridge Dunes

                         Massive, generaZly easterZy trending and migrating, nonvegetated
                         ridge dunes found on centraZ Oregon coastaZ sand sheets.

                                                 1. Morphology

                         The most dominant and obvious dune form in the open sand is the
                     oblique-ridge type. Like the transverse-ridge, it is dynamic in nature.
                     However, unlike the transverse-ridge, which is produced by unidirectional
                     wind flow, the oblique dune is formed both by the northwest summer and
                     southwest winter winds, experiencing its most energetic movement during
                     winter storms (Ternyik, 1978). Its somewhat sinuous axis is oriented
                     at an angle (obliquely) to both dominant seasonal wind sources (Figure 7).
                     Primary controlling factors in the development of the oblique-ridge dune

                                   Figure 7. Oblique-ridge dunes form obliquely
                              to both northwest and southwest dominant seasonal winds.

                     are an abundant sand supply, nearly constant onshore winds and coastal
                     forests which act as wind breaks (Cooper, 1958).

                         Sands are moved inland by the onshore winds both in the summer
                     (northwest wind) and the winter (southwest wind). Coastal forests
                     which exist on the sand sheets break the flow of the low-level winds,

                                                         79

                    causing them to deposit their sand load at the forest margin. Sand is
                    thereby deposited at a site until the height of the dune thus produced
                    equals or exceeds that of the windbreak, Sand is then precipitated over
                    the eastern face of the dune (of the precipitation ridge) by onshore winds
                    (Figure 8). In this way, the dune moves slowly inland'inundatina the

                                                                   A
                                                                          N

                                                                               -N

                                  Figure 8. Accumulation and advance of the oblique-
                             ridge dune.

                    forest as it goes (Cooper, 11958). The ridge does not actually migrate,
                    but the ridge crest operates rather like a stationary transverse dune,
                    the upper lee face of which develops to the south in the summer and to
                    the north in the winter in response to dominant seasonal wind direction
                    (Figure 9). The windward face has a gentle slope (five to thirty degrees)

                                  Figure 9. The ridge position of the oblique dune
                             is modified by seasonal winds,

                                                         80

                    while the lee face is considerably steeper with a gradient of sixty to
                    seventy degrees.

                         The oblique dunes may reach heights of 180 feet along the eastern
                    edge and may occur in groups with 500 feet or more between ridges. They
                    attain great lengths, averaging over 3,000 feet while some are nearly
                    a mile long (Cooper, 1958). They are commonly bounded on their ocean-
                    ward side by transverse-ridge dune systems and often terminate at their
                    eastern extremity in a precipitation ridge, actively invading older
                    forested dunes (Figure 10), A system of oblique-ridge dunes may form a

                      goo

                                  Figure 10. Transverse-ridge dunes riding up over
                             the flanks of an oblique-ridge dune which terminates in
                             a precipitation ridge.

                    nearly continuous eastward advancing precipitation ridge, often called
                    the active ridge.

                         The world's distribution of the oblique-ridge dune is limited to
                    the central Oregon coast and occurs on the sand sheets of Lane,
                    Douglas and Coos Counties. Good examples are found between the
                    Siuslaw and Siltcoos Rivers in Lane County and just north and south
                    of the Douglas-Coos Counties boundary.

                                                2. Vegetation

                         Sparse, marsh-type vegetation may occasionally occur in the
                    depressions between ridges within this landform. These are areas of high
                    water table and are classified as occasionally wet interdune areas.
                    Isolated areas of hummock dunes may also occur on the surface of this
                    landform.

                                        3, Attractfons and limitations

                         Recreationalists use the oblique-ridge dunes on foot, on horseback
                    and in off-road vehicles., These dunes dominate the landscape and capture
                    the imagination of visitors. I'mpact of recreationalists on this landform
                    is reportedly negligible (U.S.D.A., 1972) although research on Atlantic
                    Coast dunes indicates that considerable sand transport can occur from
                    ORV traffic. This phenonemon would not commonly be considered a serious
                    problem in areas of open windblown sand, however, it could prove to
                    be a contributing factor to such problems as rapid dune advance on
                    interdune lakes, such as at Cleawox Lake in Lane County where ORV traffic
                    is quite heavy.

                         Oblique-ridge dunes do, however, pose potential hazards for
                    recreationalists from naturally camouflaged tree cast openings in the
                    ground.

                         Although the oblique-ridge dune is poorly suited to the development
                    of permanent structures (U.S.D.A., 1972), some development has occurred
                    here. Stabilization plantings, if carried out and maintained properly,
                    can alleviate potential development problems, A primary obstacle,
                    however, is that due to the oblique-ridge dunes' mobility and incompata-
                    bility with legal boundaries, access to key downwind sites for the
                    purpose of stabilization plantings may not be readily available to the
                    developer. Water table limitations mentioned in relation to the
                    surface stabilized and older stable dunes also apply to this dune form.

                         Recently, concern has been expressed for the survival of these
                    unique dune forms. It has been predicted that these features could
                    disappear within seventy-five years due to sand starvation (U,S.D.A.,
                    1972, p. 110). Those processes, both natural and man-induced which
                    threaten this feature include:

                    1.  The eastward expansion of the deflation plain due to foredune
                        stabilization which cuts off sand supply to the area (Figure 11).

                    2.  Stabilizatfon plantings for developmental and protec  tion purposes.

                    3.  Natural revegetation of the open dune sand areas. The sand sheets
                        of the central Oregon coast, on which these dunes occur have
                        experienced several periods of dune reactivation and subsequent
                        revegetation in the last few thousand years (Cooper, 1958). Sands
                        which were reactivated, probably by fires, experienced restabiliza-
                        tion through the natural readvance of indigenous species, This
                        pattern of revegetation could well repeat itself today.

                         Due to the combination of foredune development and resulting
                    deflation plain advance, stabilization plantings and natural revegeta-
                    tion, the oblique-ridge dunes will almost certainly disappear in the
                    foreseeable future, unless man intervenes.

                                                          82

                                  Figure 11. Eastward expansion of deflation plain.
                             Sand supply is interrupted by the growing foredune.

                                         4. Identification check-list

                         The oblique-ridge dune can be identified by the following charac-
                    teristics:

                    1. The mas sive size of the oblique ridge dune is probably its most
                        distinctive characteristic.

                                              %
                                           IN
                                   M A"', A A

                                                   n b@@

                                                         83

                    2. It consists of:

                        a. a long, sinuous inland moving  ridge gently sloping on its wind-
                            ward flanks, and

                        b. very steeply sloping at its high eastern terminus where it may
                            be encroaching on older forested dunes.

                                                                           "@N

                                      is

                                      ,71

                                                                                                       84

                                   3. The slopes of this dynamic landform are most commonly vegetation-
                                          free.

                                                                              -41
                                                        I@k@-A @@A44
                                                         "ORR,

                                                                                              Q
                                                                                               I
                                                                                               JK,&
                                                                                                4W@

                                  4. The oblique dune landscape appears as a series of undulating waves
                                         of sand.

                                                                                                                                               @iJ
                                                                                                                                                  Wli,

                                                  W@-, 7",                                                                                          3'w

                                                                            .. ... ......
                                                                                                                                                    w
                                                                                                                                                  i14

                                                                                                                             M=11 ME

                                                         85

                    5. Passage of the precipitation ridge may leave  exhumed forests in its
                        wake.

                                                                         W

                                                                 sk,

                                                   @Na

                                           Mk

                    6. Islands of surface stable dunes are occasionally found within this
                        open sand landscape.

                                  MR

                                        C. Recently Reactivated Forms

                         Reactivation of active, conditionally stable and surface stable
                    dunes can occur when binding vegetation and/or the protective soil
                    layer is removed and the site is exposed to erosive winds. The amount
                    of disturbance required for reactivation varies from site to site.
                    Sensitivity to reactivation will depend upon those factors which influence
                    sand cohesiveness, including vegetative cover and cementation such
                    as that which often OCCUrs within the older stabilized dunes. The
                    orientation of the disturbed site to prevailing winds is also of critical
                    importance.

                                                  1. Blowout

                         LocaZized zone of moving sand within an otherwise vegetated area,
                         which forms a depression from wind erosion on its windward side
                         and an area of accumuZation at its terminus

                                               a. Geomorphology

                         A blowout is the result of wind scouring within an otherwise
                    conditionally stable or surface stable dune (Figure 12). A blowout

                                                                      <

                                                            Y
                                          U_

                                  Figure 12.  Small blowout within beach grass environ-
                             ment.

                    may breach the host dune and threaten others in its path, This feature
                    may be only a few feet across and several feet long in the early develop-
                    ment stages. However, it can develop into a landform hundreds of feet

                                                           87

                     across and more than a mile long (parabola dune). Smaller blowouts
                     are relatively common features of recently stabilized areas. Once a
                     blowout is begun, especially in the foredune, the trough created tends
                     to funnel the wind, increasing its velocity, and thereby enlarging the
                     blowout.

                                                  b. Vegetation

                          This is a vegetation free landform which is surrounded by vegetated
                     dunes on at least three sides.

                                         c. Attractions and limitations

                          This feature is probably not suitable for any particular activity
                     or structure.

                          The Dotential impacts of a blowout on downwind sites include sand
                     blasting, sand burial and/or heightened storm impact. Areas which may
                     be prone to blowout activity (i,e. recently planted sites or beach
                     grass areas which experience considerable use) should be carefully
                     watched particularly if significant impact inland is probable.

                                          d. Identification check-list

                          A blowout may be identified by the following features:

                     1. A blowout is a somewhat elongated, mobile sand landform which occurs
                         within otherwise surface stable or conditionally stable dunes.

                                                        88

                                              2. Parabola  Dune

                        Massive unidirectionaZ trough of def'Zation terminating in a
                        zone of accumuZation within an otherwise vegetated area.

                                              a. Geomorphology

                        A parabola is essentially a trough blowout of major size which is
                   enclosed on three sides by older vegetated dunes and on the fourth,
                   its source area, by open sand usually of the oblique-ridge type (Figure
                   13). The initial development of a parabola requires a stable vegetated

                               WL

                                 Figure 13. Parabola blowout moving through forested
                            dunes.

                   site downwind with a point of weakness for the moving sand to break
                   through, considerable volume of source sand, and a unidirectional wind
                   source. Parabolas move inland from their open sand source, through the
                   vegetated area, in a direction parallel to the unidirectional wind
                   source. They can be seen oriented either to the northwest winds of
                   summer or the southwest winds of winter. They may be a hundred feet or
                   more across and extend to nearly a mile in length. Parabolas are
                   named for the similarity that their perimenter bears to the parabolic
                   curve.

                                               b. Vegetation

                        This is essentially a vegetation free landform although less active
                   forms may exhibit occasional vegetated hummocks.

                                                         89

                                        c. Attracti,ons and limitations

                         Recreationalists are attracted to this landform for walking,
                    viewing, riding horses, and operating off-road vehicles. The only
                    limitations on these activities are the sensitivity of the fringe-areas'
                    vegetation to trampling and the possible nuisance of sand blasting.

                         Any development involving permanent structures would be subject to
                    the same limitations as those associated with the oblique-ridge dunes
                    although sand blasting may be a greater problem in this landform.

                                         d.  Identification check-list

                         A parabola dune may be identified by the following characteristics:

                    1. This feature creates an elongate finger of sand cutting through old
                        forested dunes.

                                                   A
                                                       , I PW

                                                        90

                   2. The terminus (advancing end) of well-developed parabola dunes
                       commonly creates a precipitation ridge advancing on older forested
                       dunes.

                                            Me
                                                  14,

                                                                 i, W
                                                      M,

                                                           91

                                            VII. GLOSSARY OF TERMS

                     Accretion:   Oceanward advancement of the beach through the ongoing.
                          accumulation of sand at its edge.

                     Active Dunes: Partially vegetated dunes that migrate, grow   and diminish
                          according to wind, sand supply and vegetation cover. (May apply to
                          the foredune or hummock dunes.)

                     Beach Cusps: Embayments of various widths and slopes cut into   the beach
                          by the cellular circulation of onshore and offshore currents.

                     Blowout: Localized zone of deflation within an otherwise vea.etated area.

                     "Conditionally Stable Dune: A dune which presently has sufficient
                          vegetation cover to retard wind erosion but whichIs vulnerable to
                          reactivation upon disturbance of this cover.

                     Deflation: The erosion of sand or soil by the wind.

                     Embryo Dune: Low, newly forming dune mounds.

                     Erosion:  To wear away @Uy the action of water, waves or wind.

                     Lee: The side that is sheltered from the wind.

                     Older Stable Dune: Dunes of any form which possess   both-a deep, well-
                          developed soil and semi-cemented underlying sand.

                     Onshore '14inds:'Winds which are moving toward or onto the shore from
                          open water.

                     Precipitation Ridge: High, steeply sloping slip face of large oblique-
                          ridge and paraGola dunes.

                     Rip Current: A strong relatively narrow current flowing outward from a
                          shore which results from the inland flow of waves and wind-driven
                          water.

                     Sandsheet: Sand deposits of considerable depth and breadth overlying
                          sursurface coastal terraces.

                     Surface Stabilized Dune: Commonly forested dunes which possess a thinly
                          developed soil and are underlain by loose unconsolidated sands.

                     Wind Stable Dune: Those dunes which possess sufficient vegetation and/or
                          soil cover to retard wind erosion.

                     Windward: The side or direction from which the wind is blowing.

                                                         92

                                               REFERENCES CITED

                    Cooper, William S. 1958. Coastal Sand Dunes of Oregon and Washington.
                         Geological Society of America, Memoir 72. New York, New York. 169 ppt

                    Leach, Don. Interview. 1978. U.S. Department -of Agriculture, Soil
                         Conservation Service, Astoria, Oregon.

                    Lund, Ernest H. 1973. "Oregon Coastal Dunes," The Ore Bin. State of
                         Oregon Department of Geology and Mineral Industries, Portland..
                         Oregon. 92 pp.

                    Ternyik, Wilbur. Personal Communication. October, 1978. Owner, Wave
                         Beachgrass Nursery, Florence, Oregon.

                    U.S. Department of Agriculture, Forest Service. 1972. Resource
                         Inventory Report for the Oregon Dunes National Recreation Area.
                         Siuslaw National Forest, Portland, Oregon. 294 pp.
                    U.S. Department of Agriculture, Soil Conservation Service and Oregon
                         Coastal Conservation and Development Commission. 1975. Beaches
                         and Dunes of the Oregon Coast. U.S. Department of Agriculture,
                         Soil Conservation Service, Portland, Oregon. 161 pp.
                    Weideman, Alfred M., LaRea J. Dennis, Frank H. Smith. 1974. Plants of
                         The Oregon Coastal Dunes. Oregon State University Press,-Corvallis,
                         Oregon. 117--pp.-

                                                                                               1,
                                                                                               t
                                                                                               ,i
                                                                                               I
                                                                                               I
                                                                                               I
                                                                                               I
                                                                                               I
                                                                                               I
                                                                                               I
     I
                                                                                               I
                                                                                               I

                                                            i
                                       I

                                       1 3 6668 00001 0993 @