1980 Coastal L. Memo 1 (1980)

handle is hein.journals/ocoaslme1980 and id is 1 raw text is: 





Ocean  and  Coastal   Law  Center   * School  of  Law  * University of Oregon * Eugene 97403






        A Coastal Law memo


August  1980


COASTAL NATURAL HAZARDS MANAGEMENT


      Development in the coastal zone is exposed
to a variety of natural hazards. Development
often increases the risk of personal injury or
property damage.  Coastal land in Oregon is
threatened by geologic hazards such as earthquakes,
erosion, landslides, and land subsidence. This
Cuastal Law Memo will discudd how state and local
government in Oregon are attempting to mitigate
damage caused by coastal natural hazards.

               GEOLOGIC HAZARDS

      The most common geologic hazard in Oregon's
coastal zone is erosion.  Erosion is the removal
and transport of rocks or soil material by moving
water.  It is a vital process in the coastal zone
because it provides a source of sandy material for
the beach.  But as a seacliff erodes, clifftop
development may be threatened.

      Many alhorelinC crosion problcmn arc the
direct result of past unwise development de-
cisions and are made worse by inadequate resource
management.  Erosion damage is likely to increase
in the future.  While more beach and dune areas
are devoted to housing, the supply of new beach
sand is reduced by dredging and flood control
projects.  Narrowing beaches will result in flood-
ing and landslide damage.

      The 1976 amendments to the federal Coastal
Zone Management Act (CZMA) recognized the problem
of coastal erosion by requiring federally-funded
state coastal zone management programs to con-
tain a planning process for shoreline erosion
problems.  Oregon's federally approved coastal
program contains such a planning process as well
as specific rules with respect to shoreline ero-
sion management which are described later in this
memo.

      Landslides are often associated with erosion.
A landslide is a perceptible downward sliding or
falling of a mass of earth, rock, or a mixture of
the two.  It is nature's method of stabilizing a
slope.  Landslides may result from natural forces,
but are often caused by man. With many coastal
hillsides being developed, the risk of downslope
movement increases.  Development can increase the
water content of the soil and the amount of ground-


water in the system.  When this occurs the soil
becomes saturated and its weight increases.  In
addition, the weight of hillside structures in-
creases the downward force on the slope. These
factors increase the risk of a slide.  Conse-
quently, because of development, an area which
was free of problemo may end up with slope failures.

     Land subsidence occurs when surface material
is displaced vertically downward with little or
no horizontal movement.  Man can cause subsidence
by withdrawing large volumes of fluids from weakly
consolidated segments.  The loss of support causes
subsidence.  Unlike other coastal geologic hazards,
the major problem with subsidence is economic loss
rather than personal injury.  Solutions are gener-
ally expensive.

     An earthquake is the sudden release of stress
built up by tectonic forces in the earth's crust.
This stress release causes ground shaking, which
may result in landslides.  Many coastal areas are
exposed to moderate to high earthquake risk.  This
is especially true of the Pacific coast, primarily
because of two tectonic plates, the Pacific and
the North American plates, which meet in the San
Andreas Fault Zone.

               COMMON LAW PRINCIPLES

     Historically, the pattern of development in
coastal areas was relatively haphazard.  There
were no long-range comprehensive plans. As  a
result, disputes between coastal landowners, or
the government and coastal landowners over such
issues as liability for eroding land, protection
for eroding lands and use restrictions were often
resolved by the courts.

     Coastal property owners often desire to pro-
tect their land and improvements against damage
from coastal waters by constructing various shore-
line protective devices.  The crucial issue is the
degree of protective measures that a landowner
may take without incurring liability for damage
to neighboring lands.

     Although there has been no reported litiga-
tion on this issue in Oregon with respect to the
Pacific shoreline, decisions involving inland


Distributed by:  OSU Extension Service' Sea Grant Marine Advisory Program, Corvallis, OR 97331


Issue  1

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