FS-019 (pg. 1 of 3)
OHIO SEA GRANT AND STONE LABORATORY
Lake Erie Shore Erosion
Just east of Painesville Township Park, Lake County, Ohio taken June 11, 2013. The edge of the cut grass delineates where the bluff is slumping and will eventually fall down
into Lake Erie.
OHSU-FS-019
Updated Feb. 3, 2014
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Ohio Sea Grant, based at The
Ohio State University, is one
of 33 state programs in the
National Sea Grant College
Program of the National
Oceanic and Atmospheric
Administration (NOAA),
Department of Commerce.
Ohio Sea Grant is supported
by the Ohio Board of Regents,
Ohio State University
Extension, other universities,
industries, and associations.
WAVE EROSION
Wave erosion is the primary coastal erosion process
at work on the Ohio shoreline. Wind blowing
across Lake Erie transfers energy to the water
and generates waves, and much of this energy is
released when the waves break on the shoreline.
Although waves come in all sizes, they all have
essentially the same characteristics. Every wave has
Just east of Painesville Township Park, Lake County, Ohio taken in
a top (crest) and a bottom (trough). The height of a
Spring of 2009. The edge of the grass delineates where the bluff
has slumped a foot or two lower than the stable part of the bluff.
wave is measured vertically from the wave’s crest to
The unstable section will eventually slide down into Lake Erie.
its trough. Wave length is measured from any point
on one wave to that same point on the next wave; for
example from the crest of one wave to the crest of the next wave, or from trough to trough. Wave period
(wave speed) is the time it takes a wave, trough to trough or crest to crest, to travel the distance equal to
one wave length. Waves with a short period are moving up and down very quickly, so the transition from
trough to crest to trough happens more quickly for a short-period wave than for a long-period wave.
D
EP
ER
Ohio Sea Grant
1314 Kinnear Road
Area 100
Columbus, OH 43212
614-292-8949
ohioseagrant.osu.edu
T
The two primary shore erosion processes at work along Ohio’s Lake Erie shoreline are wave erosion
(which removes material from the beach) and mass wasting (which removes material from an
adjacent bluff). Rates of erosion are highly variable and may range from as low as 1 foot per year to
as high as 5 to 15 feet per year (Carter et al. 1987). The lower rates are usually found where hard bedrock
meets the water, with higher rates where soft marsh and clay substrate form the lakeshore.
Many factors determine the rates of shoreline erosion. The weather influences the size and frequency
of waves striking the shoreline, and therefore the force directed against it. The physical setting – shore
orientation, presence or absence of a beach or man-made structures, coastal geology – also contribute to
the variability of shore erosion.
NATIONAL OC
EA
Frank R. Lichtkoppler
Extension Program
Coordinator
[email protected]
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Lake Erie Shore Erosion | 2014 Ohio Sea Grant and Stone Laboratory
FS-019 (pg. 2 of 3)
WAVE DEFINITIONS
A good rule of thumb is that a wave will break when the depth
of the water is four-thirds of the wave height. A one-foot wave
will break in 16 inches of water, while a three-foot wave will break
in water four feet deep. When waves break against the shore,
the amount of released energy is dependent upon the slope of
the bottom and the wave height: the steeper and smoother the
bottom slope, the more abruptly a wave will slow down and break,
thereby releasing more energy and causing greater damage.
The amount of energy in a wave is proportional to the square
of the wave height, and the higher the wave, the more energy
it contains. This means there is a four-fold increase in energy
for a two-fold increase in wave height. For example, a two-foot
wave with a period of five seconds between crests contains over
4,000 foot-pounds of energy per foot of wave crest. A four-foot
wave (two times the height) with the same period contains over
16,000 foot-pounds (four times the energy) of energy per foot of
wave crest.
A series of two-foot waves with a five-second period will
break upon the shoreline at a rate of 720 waves and a total of
over 2.9 million foot-pounds of energy per hour. In one 24-hour
day this adds up to 17,280 waves and more than 70.7 million
foot-pounds of energy per foot of shoreline. This uncontrolled
energy continuously erodes
material away from the shore,
transporting material along the
shoreline and cutting away at
the shore.
However, wave energy
arriving at the shoreline is not
constant. Wind blows neither
continuously nor always
from the same direction, so
the supply of energy varies
from place to place along the
coast and with time at each
location. Wide beaches, shallow
nearshore slopes and nearshore
Poor construction and the pressure
bars all absorb incoming energy of the unstable bluff combined to
and reduce the amount of wave cause a catastrophic failure of a steel
sheet pile retaining wall at Painesville
energy that reaches the shore
Township Park, Lake County, Ohio.
Photo taken on June 13, 2013.
because shallow nearshore
slopes and nearshore bars cause large waves to break and
expend much of their energy offshore. The resulting smaller
waves reaching the shore then contain less energy and cause
less shoreline erosion.
Weather directly influences coastal erosion rates because it
affects the size of wave-related forces. Storm-generated winds
can increase erosion rates due to temporary high water levels
(storm surges) and large waves. For example, on November
12-13, 2003, westerly storm winds along the 242-mile length of
Lake Erie created a 13-14 foot difference in water levels when
measured simultaneously at Toledo, Ohio and Buffalo, New York.
These are some of the highest water level differences recorded
on Lake Erie. More erosion occurs during storms and high water
levels than at any other time.
Ice can have a moderating effect on erosion because it
protects the nearshore area from late winter storms and waves.
Nearshore ice eliminates waves reaching the shore as waves
from the open lake break on the off-shore ice, not the beach. A
solid sheet of ice covering the lake prevents wind from affecting
the surface of the water, thus preventing the formation of waves.
However, once the ice sheet has broken, this moderating effect
goes away. With a trend towards less ice on the Great Lakes , the
loss of the moderating effect of winter ice can lead to increased
erosion of the shoreline.
MASS WASTING (BLUFF SLUMPING)
Mass wasting, when large masses of the shoreline drop
down toward or into the lake as a single chunk of material, is
seen in northeastern Ohio, where erosion-prone bluffs meet
the lakeshore. This downward movement has various and
sometimes complex causes. Waves may erode the foot (also
called the base or toe) of a bluff, reducing the stability of the
material above. Surface water can compound the problem by
adding weight at the top, and by reducing the bluff’s resistance
to shear stress. Groundwater seepage (water within the bluff)
acts as a lubricant between sediment layers and further reduces
the stability of a bluff. When this occurs, the material in an upper
layer may slide downward in one mass. Rain saturating a bluff
can increase the rate of erosion in a similar fashion. Rain also
produces runoff that causes surface erosion, creates gullies and
ravines, and steepens bluffs.
FS-019 (pg. 3 of 3)
Lake Erie Shore Erosion | 2014 Ohio Sea Grant and Stone Laboratory
Erosion by mass wasting does not happen every year but it
may follow a specific sequence of events. Wave action removes
material from the toe (base) of the bluffs, steepening and eroding
the bluff face. Winter is a fairly static period because of freezing
temperatures and lakeshore ice. In the spring, frequent rains,
storm runoff, increased groundwater levels, storm waves and
increasing seasonal water levels cause already eroded bluffs to
become unstable, and mass wasting or slumping may occur.
As long as wave energy carries material away from the base
of a bluff and groundwater saturates the bluff material, the bluff
will continue to recede. The
rate of recession, however,
Surface and ground
water erosion of the
is not constant because of
shoreline is explained
several factors, one of which
in the ODNR Office of
may be that the amount of
Coastal management
wave energy reaching the
fact sheet Discover
shoreline is not constant, but
Lake Erie: Causes of
varies with the weather, lake
Erosion - Surface and
Groundwater. This
levels, and the physical setting
fact sheet may be
of the shoreline. Storms may
found at the ODNR
temporarily raise lake levels
Office of Coastal
and flood beaches, thus
Management web site
allowing large waves to reach
at: http://go.osu.edu/
ODNRerosion.
the shore and directly erode
the toe of a bluff. The nature
of the shoreline material being eroded (resistant rock, humanconstructed shore protection, movable sand etc.) is also a major
influence on how much and how fast the shoreline and/or the
bluff erode.
While wide beaches always serve as protective barriers
against erosion, the same cannot be said of man-made
structures – even those built for that purpose. Many bulkheads
and seawalls do slow wave-based erosion, but others
can actually make the problem worse. Poor design and/or
construction of a shore protection structure may turn a minor
erosion problem into a severe one. A built structure may worsen
erosion problems at the site where it has been constructed, or it
may increase rates of erosion of a neighbor’s property. Vertical
seawalls may deflect erosive wave forces down, removing
beach material from in front of the seawall. Other structures
may trap sand in one area (protecting that location) but prevent
material from moving away, denying this protection to other
areas of the lakeshore.
A discussion of erosion is not complete without considering
the nature of the material being eroded. Softer, loose material
like clay, silt and sand erode more easily and quickly than more
durable materials like shale and limestone rock. Indeed, the
makeup of the shoreline is one of the most crucial variables
affecting erosion rates.
There are two key ideas in considering shoreline erosion:
1) along Lake Erie, shore erosion is very site-specific depending
on site conditions, and 2) highly variable depending on
Large waves are reaching the shore and breaking against shore erosion devices,
while smaller waves break on the sloping beach at Fairport Harbor Beach. Taken
looking east towards Painesville Township Park. Lake County, Ohio, during Super
Storm Sandy on October 30, 2012.
weather, lake levels, storms and other factors acting together to
influence shoreline erosion. These factors include the nature of
the material being eroded, the physical setting of the shore, the
presence or absence of protective beaches and/or man-made
shore protection devices, geographic shore line orientation and
its exposure to waves, lake levels, and the weather.
Many shoreline property owners are faced with erosion
problems and must make decisions concerning this issue.
Any effort to slow down and lessen the effects of this natural
process requires time, money, and effort, and providing shore
protection at one location may just move the problem downdrift
to the adjacent property. Thus it is particularly important for
coastal property owners to learn and understand as much about
shore erosion as possible. A good place to start is the ODNR–
Office of Coastal Management web site at:
http://www.dnr.state.oh.us/coastal.
FOR MORE INFORMATION ON EROSION, CONTACT:
ODNR Office of
Ohio Sea Grant Extension
Coastal Management
1314 Kinnear Rd.
105 West Shoreline Drive
Columbus, OH 43212
Sandusky OH 44870
614-292-8949
419-626-7980
ohioseagrant.osu.edu
1-888-OHIO-CMP (toll free)
[email protected]
coastal.ohiodnr.gov
References
Bascom, Willard. 1980. Waves and Beaches. New York, New York: Anchor Books
366 pp.
Carter, Charles H. Lake Erie Shore Erosion 1976, Lake County, Ohio : Setting,
Processes and Recession Rates from 1973 to 1976. Report of investigations
No.99, Ohio Geological Survey, Ohio Department of Natural Resources. 105 pp.
Carter, Charles H., Donald E. Guy, Jr. and Jonathan A. Fuller. 1981. Coastal
Geomorphology and the Geology of the Ohio Shore of Lake Erie. Geological
Soc. American, Cincinnati Field Trip Guidebook, American Geological institute,
Vol. 3 pp. 433-456.
Carter, Charles H., William J. Neil, William S. Haras, and Orrin H. Pilkey, Jr. 1987.
Living with the Lake Erie Shore. Duke University Press. Durham, North Carolina.
263 pp.
National Oceanic and Atmospheric Administration. Water Levels of Lake Erie
During the storm of April 6, 1979. Washington D.C.
Stewart, Steve. Great Lakes Storms Photo Gallery Great Lakes Storm Surges
November 12-13, 2003. Great Lakes Sea Grant Extension Office @ Great Lakes
Environmental Research Laboratory. Accessed June 2013 at: http://www.glerl.
noaa.gov/seagrant/glwlphotos/Seiche/1113Storm/November2003.html.