Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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The Ryan Wave Reversing Break Wall:
A solution to shoreline degradation by wave damage.
Concept, design, models, testing and documentation by Patric Ryan and
Sophie Ryan. The Wave Reversing Break Wall is also known as the WRBW.
Specification:
This invention relates to marine, lake and riverine seawalls and break walls
employed to protect shoreline properties from wave damage. The Ryan WRBW
is a unique reinforced concrete or rotomoulded polyethylene unit, that, when
used in a conjunction with similar units, will protect shorelines from wave
damage by turning back the waves and absorbing their energy and in the process
preventing erosion, while rebuilding sand beaches.
How the WRBW works:
(1) The vertical, concave face l., (Figures 1 & 3), a chord of a circle, and
the gently sloping base 3., (Figures 2 & 4), absorb storm wave energy and curl
waves back on themselves, creating positive water turbulence in front of the
WRBW.
CA 02271580 1999-OS-14
(2) The positive turbulence creates friction, trips and slows down
succeeding waves.
(3) The positive turbulence reduces or breaks up backwash and rip
currents allowing moving sand to drop out of suspension to collect in front of
the
WRBWs. This drop out sand also builds up a wider beach, creating more
friction, slowing down incoming waves, further protecting the shoreline.
(4) The wide, sloping base 3., of the WRBW provides stability and ease of
installation.
(5) Size of WRBW units can be tailored to suit the shoreline, e.g. riverine
or inland lake break walls can be smaller in scale than marine application
WRBW
units.
(6) The size of individual WRBW units, equipped with lifting lugs, make
handling and installation easy for construction crews.
(7) The WRBW units lock together by a simple mortise and tenon system
to prevent units shifting out of position.
(8) The WRBW units can be back-filled with existing rubble or local
materials, and topped with soil and vegetation.
(9) The unique design of the WRBW will also protect endangered sand
dunes even beyond the reach of the waves by deflecting the wind, creating back
eddies, and allowing the sand to fill in behind the units.
The WRBW may be produced in two styles: the wide base (Figure 3
{2b}) and the narrow base (Figure 1 {2a}), to address physical features of the
installation site. As well there are angled base shapes of the wide or narrow
based units to accommodate shoreline contours, but the primary design features
will remain consistent; the sloping base and the concave face.
The idea for the WRBW came about as my daughter Sophie and I prepared
for a science fair. The beginning discussions were about tidal waves and
a.
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earthquakes and how to protect humans and habitations, but it was apparent
that
simulating earthquakes and tidal waves in our kitchen was a bit more than we
could manage. (One year we created miniature cyclones in our kitchen in a
cyclone generator, with some success, but ruined the tile floor.) My interest
in
storm wave damage spanned many years in the marine field as a commercial
diver and ship's o~cer, so I advanced, and steered, the topic from tidal waves
to
storm waves, tide surges, flood tides and wave damage to low lying marine and
lake shorelines. We discussed conventional break wall types, concluding that
conventional vertical bulkhead seawalls and sloping bean or rubble break walls
were inefficient at best in storm conditions and would not solve the problems
of
rising sea levels on marine coastal lowlands or the current erosion problems
on
rivers, inland lakes, and the Great Lakes shoreline. A new break wall design
was
needed. A new approach to the problem of counteracting wave damage.
I was raised on the Lake Erie north shore. For years we have watched the
North Shore of Lake Erie, from Holiday Beach in the west to Long Point and
beyond to Crystal Beach, being hammered and eroded by storms and changing
water levels. The governments and property owners along one stretch of beach
from Pointe aux Pins to Erieau and Erie Beach, tried everything, including the
kitchen sink, to stop the lake from taking their cottages, shoreline
properties and
the dike road. Cottages and retirement homes tumbled into the lake as
makeshift
and conventional break walls failed. Valuable reclaimed marsh crop lands
behind
the dikes are constantly threatened with flooding in high water years. The
once
wide beaches are littered with attempts to slow down the erosion. Point Pelee,
Pointe aux Pins and Long Point, all unstable sand bars and sand spits, move
and
shift at the whim of the waves and currents. Government and Public Works have
tried various ways to slow down the erosion. The Ryan WRBW would prevent
the erosion.
Bayfield is a small Ontario lakefront town, one of many communities on
Lake Huron currently battling shoreline erosion with a hodge podge of break
wall types. The town park, on a clay bank, is threatened. There are many miles
3.
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of low lying beaches and clay cliff shorelines around the Great Lakes
suffering
similar fates as beaches change and clay cliffs erode due to wave damage at
their
base. Land is disappearing. The WRBW would reverse this trend.
The coastal lowlands of North America are under the added pressure of
rising sea levels. The oceans have risen lOcm in the last century. A further
rise
of 4cm to 8cm is predicted in the next 30 years due to thermal expansion
alone.
That is in addition to the forecast of melting continental ice fields. The
WRBW
could be the answer to marine communities faced with increasing wave damage.
As Global Warming changes weather patterns increasingly severe storms are
predicted.
Many sensitive shorelines cannot be protected for practical reasons, nor
should they be interfered with, for environmental reasons, but many
shorelines,
where development and investment is immense, must be protected because
economically there is no alternative. Smith Island in Chesapeake Bay, a
fishing
community of 400 people, is a low lying island which is slowing submerging due
to rising waters and constant wave action. Miami Beach cannot be moved inland
off its barrier island. The seas, in normal storm conditions, relentlessly
advance,
erode and undermine the conventional break walls and bulkheads offering
inadequate protection to the miles of expensive homes, resorts and
condominiums. Florida communities like Miami Beach, spend millions of dollars
annually importing sand to feed the ravenous ocean. WRBWs would prevent the
loss of sand and build up beaches, as well as protect property.
Cape Cod National Seashore is endangered. The Barrier Islands from Cape
Cod to Florida are being driven back on themselves. In most cases lowland
barrier islands, their lagoons and salt marshes should be left to their own
devices.
Nature must seek its balance, but some of that 2500 km stretch (or 25,000 kms
of
bays, coves, inlets and islands) is recreation land, homes, towns, harbours
and
irreplaceable national historic treasures. And then there's Chesapeake Bay
itself
with over 1350 kms of low shorelines with communities built when water levels
were lower. This past Atlantic and Gulf of Mexico hurricane season was the
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most destructive on record. Low lying developed areas can be protected by
Wave Reversing Break Walls designed and tailored to suit the conditions.
The WRBW will provide a system to stop the degradation by erosion and
battering and allow the shorelines to be cleaned up, the rubble now littering
the
beaches can be used as back fill behind the WRBWs.
"The embodiments of the invention in which an exclusive property or
privilege is claimed are defined as follows:"
Why the Wave Reversing Break Walls work:
List of drawings...In drawings which illustrate embodiments of the
invention, Figure 1 is an elevation of one embodiment (the short base WRBW
viewed from the left side), Figure 2 is a top view of this embodiment (the
short
base WRBW), Figure 3 is an elevation of the long base WRBW, and Figure 4 is a
plan view of the long base WRBW.
Figure 5 is a view of the WRBW showing sand buildup and back fill.
Photo Page shows five views of WRBW models in lake tests.
There are distinct differences between waves deflected by conventional
break walls or seawalls and waves curled back by the Ryan Wave Reversing
Break Wall. (see Photo Page) The energy of a wave striking a conventional
vertical break wall is deflected as a shock wave, transmitting a significant
amount
of energy in several directions, including up and over. The wave may be
interrupted but its energy is not dissipated.
However, the WRBW accepts the energy of waves and absorbs their power
by turning them back on themselves, not as deflected energy, but as collapsing
water. This collapsing water and resulting turbulence is a direct result of
the
design of the WRBW.
I have been watching break walls, bulkheads, breakwaters, beans, dikes
s.
CA 02271580 1999-OS-14
and seawalls for many years. As a former commercial diver I have assisted in
the building of breakwaters and beans, and repaired wave damage to docks and
bulkheads. A consistent problem with conventional attempts to stop or deflect
wave energy is that the device is most often a vertical wall section that
attempts to
resist the force of waves, or a sloped bean section, usually loose armour
stone,
rock rubble or rip rap, to dampen or absorb the waves with varying degrees of
success. But all conventional systems degrade or fail in time due to battering
or
erosion. There have been attempts to deflect or trick waves and currents using
projecting groins, solid piers, plastic sausages filled with sand and odd
shaped
structures, even floating mats of old tires. Most devices do not work in
extreme
conditions because they try to resist force instead of removing the force or
using
the force on itself. The Wave Reversing Break Wall is purposely designed
(Figures 1 & 3) to accept the incoming wave, presenting a gently sloped base
(3.)
to allow the leading edge of the wave to run up quickly where a shallow lip
(9.)
below the entrance to the curved section (1.), initially trips the leading
edge of
the wave. Some sand drops out at the lip (9.). The wave, (which has already
been dampened somewhat by the positive turbulence of the previous wave) then
enters the curve (l.) of the WRBW unit, is redirected, curls upwards and is
propelled around the curved section. The wave flings itself outward until
gravity
pulls it down, collapsing in a welter of foam and turbulence. The wave has
encountered minimal resistance from the slope and curve of the WRBW and the
distance it hurls itself outward is a function of the speed and force of the
incoming wave. The resulting turbulence is important. The turbulence prevents
currents from forming, allowing sand to drop out.
In general on an open beach a wave striking the the fore shore runs up the
sand or gravel slope until it expends its energy on the upper beach, or
strikes a
barner. The wave's total volume of water then retreats down the beach,
creating
a significant rip current as it runs back out to sea. This repeated run-up and
retreat cycle creates strong currents. Sand is constantly on the move in the
direction of the currents. If the waves come in at an angle to the beach, the
sand
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is moved along the beach until deposited elsewhere. If there is a barrier on
the
beach, such as a vertical break wall, groin, bean or sea wall, the force of
the
wave is taken full on or deflected without being dissipated. Damage occurs
according to the size of the waves and the duration of the assault. But a
current is
still set up and the sand or gravel is scoured away from the sea wall,
bulkhead or
rubble berm, causing erosion that will eventually destroy or undercut the
conventional structures or batter them down, or both.
The WRBW avoids this damage because the units absorb the wave energy
by not offering resistance other than the slope of the base (3.), and the
design
curve,(1.). The wave's weight, which could be several thousand tons, is
countered by the weight of the water itself pressing down on the base (3.&2.),
the
weight of concrete or concrete filled rotomoulded polyethylene unit itself
and,
most importantly, by the back-fill, Figure 5 (13.) behind the WRBW units.
In critical situations WRBWs could also be used on top of existing vertical
break walls or piers, as sea levels rise, to protect property from storm waves
and
flood tide waves that overtop conventional break walls. The design principles
of
the WRBW would still apply, and the resulting turbulence created out in front
of
the bulkheads could effectively protect the existing vertical sea wall from
damage.
To accommodate shorelines with bends and curves, additional WRBW units
will be fabricated with one side angled a few degrees to create inside or
outside
curves.
In our model tests of the WRBW we have discovered some
interesting features.
I have described how the energy of the wave is absorbed and deflected by
the WRBW. Waves curling back from the WRBW collapse, tumble and splash
into the path of the next wave, and, just as important, the subsequent
positive
turbulence reduced the next wave's energy and height before it reached the
break
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wall units. Wave after wave charged at the WRBW only to be dampened by the
positive turbulence and what wave action did reach the WRBW was turned
harmlessly back.
We also watched for signs of erosion or weakness in the design. What we
observed was that after a short time the sand, Figure 5 (14.), rather than
being
eroded, as happens with most break walls or beans, actually built up a bar in
front of the WRBW units to the height of the slope face Figures 1,3 & 5 (4.).
We
observed that the current or rip tide usually associated with wave action was
stalled by the turbulence, allowing the suspended sand to drop out. This build
up
of sand protected the base of the units.
In addition we observed that the larger than average waves, called rogue
waves, even though they were higher than the WRBW units themselves, were
resisted, and only the shear volume of water sloshed over the top of the
WRBWs.
The spill-over flooding carried some sand out between the units. This problem
could be solved by using aggregate larger than the spaces between the units,
plus
using vegetation and non-woven erosion matting along the backs of the units to
hold the fill and aggregate in place. The larger rogue waves that did slop
over
the WRBW did no damage otherwise because the force had been taken away by
the reversing, energy absorbing action. The rogue waves were reduced to flow-
flooding rather than full force battering.
As well as the build up of the sand in front of the WRBWs, we observed
that the original beach drop-off line moved further out all along the line of
WRBW units as the sand built up. This was measured and documented on video
camera. Once established, the new beach drop-off line remained or increased,
further protecting the shoreline by making the beach wider, increasing the
area
where incoming waves would break and run. Waves were reduced by friction
and the positive turbulence caused by the preceding waves curling back and
collapsing. It means that the incoming waves brake sooner, and further out.
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Waves coming into the WRBW units from an angle spiralled harmlessly
away, running the length of the line of units and dissipating. Angled wave
action
on a normal sloped beach without protection scours the sand naturally and
moves
it along the beach to build up or erode depending on the physical structures
and
barners, such as groins and piers. Our research tells us that groins and
piers,
(which are both barriers thrusting out into the water), cause more problems
than
they solve by forcing the sand or gravel to build up too much on one side
while
robbing sand from the other. The WRBWs prevent this kind of erosion. Sand
appears to be distributed fairly evenly along the line of units.
What we observed with the WRBW was that the waves curled back on
themselves and collapsed in turbulence. We did not observe a current or a
direction. What we observed was confused water dampening or slowing down
the next wave, and so on.
An important consideration is the WRBWs resistance to ice damage. I
believe the shape of the units will be a big advantage as moving ice will
react
much the same as waves, fracturing, curling up and back continuously and
harmlessly. New ice in lakes and rivers is not a problem. New ice fractures
easily in wave action. When the ice builds up to large, thick flows they
ground
out in shallow water, building up higher as more ice is pushed in, to create
their
own protective barner, usually staying in place until spring breakup.
Important additional feature of the WRBWs: Another feature of
the WRBW is the protection of sand dune structure shorelines from wind
erosion.
When the waves aren't carving sand away from beaches and dunes, sea winds are
blowing them inland. If WRBWs are already in place to thwart encroaching
waves the same design principle of the curved face would also deflect wind up,
creating a wind buffer and back eddies behind the units, buffering the dunes
from
winds and allowing the sand to fill in behind the units. Wind deflection could
be
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as important to sandy shores and conservation as wave energy absorption.
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Appendix A
Measurements of the Long Base WRBW unit.
Base of long base WRBW in concrete or rotomoulded polyethelen unit:
* The Long Base WRBW unit is wider than it is long, 'length' being the face
opening to seaward or landward.
** Concrete and plastic moulded units vary in measurements by about one degree
to allow for mould release mechanics, not shown in drawings for clarity.
Plan view, Figure 4 shows the mortise and tenon locking system.
Length, along the outward face (4.) and along the back face (5.) - 183 cm.
Width, along the base sides (2b.) - 244 cm.
Top of unit seen in plan view. Length, along the outward face (4.) and
along the back face (5.) - 183 cm. Width of top (7.) - 45.7 cm.
Distance top face (6.), above the curve, is set back from base face (4.) in
plan view - 91.5 cm. Distance back face of top set back from back of base -
152.5 cm.
Figure 3 is an elevation view:
Base (2b.) to top of the face (4.) at the extreme forward of the fore slope
(3.) - 30.5 cm.
From the side. Base (2b) to extreme back of the fore slope (3.) (at the lip,
{ 9. } ) - 45.7 cm.
Lip (Q from slope to bottom edge of curve {1.) - 7.7 cm
From the side. Height of curve opening (1.) from lip to top face - 91.5
cm.
Depth of curved face ( 1.) from line drawn through upper and lower edge
(upper face to lip ) which is the cord of circle - 45.7 cm.
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From the side. Height of top face (6.) from top edge of curve opening (1.)
to top of unit (7.) - 30.5 cm.
From the side. Base (2b) to top of back vertical face (5.) - 30.5 cm
From the side. Base (2b.) to extreme height of back slope (12.) 45.7 cm.
Base (2b) to perpendicular height of unit at back edge of top (7.) 183 cm.
Mortise measurements: Fore edge of mortise (11.) begins 61 cm. in from
face on left side of unit when looking from seaward.
Depth of mortise. 29.1 cm.
Elevation of mortise. At the part nearest face (11.) - 35 cm
Elevation of mortise. From base (2b) to lip (9.), aft part of mortise (10.) -
45.7 cm
Tenonmeasurements: Fore face of tenon (11.) begins 61 cm in from base
face on right side of unit when looking from seaward.
Projection of tenon. 29.1 cm....
Elevation of tenon. At the projection (11.) nearest the face - 35 cm.
Elevation of tenon. Base (2b.) to lip (9.), aft part of mortise - 45.7 cm
Figures 1 & 2 (Drawings) show short base version of the
WRBW.
*The short base version is 61 cm shorter, measured from after face (5.)
forward. All other measurements of Figures 1 & 2 are the same as for the long
base version.
