FIELD OF THE INVENTION

[0001 ] The present invention relates to the modification of wave-breaking characteristics and more specifically is related to an artificial reef to enhance waves for surfing and/or to modify waves to reduce beach erosion.

BACKGROUND TO THE INVENTION

[0002] There are known many forms of artificial reef to modify wave-breaking characteristics and/or to provide a sanctuary for marine life. Some are made from rigid material, but these are not well suited to recreational uses such as surfing, are difficult and expensive to install and difficult to relocate if in the wrong position or repair if damaged or moved by a storm. Others are resilient to prevent damage to boats and to prevent injury to people using the water.

[0003] Some resilient artificial reefs such as the invention disclosed in United States Patent Application Publication Number 2001/0014256 comprise multiple air compartments which makes them relatively complex to manufacture, install and maintain.

[0004] Similarly, Japanese Publication of Unexamined Patent Application Number S63-22909 discloses an artificial reef characterised by a bladder of flexible sheet-like material anchored to the sea bed and injected with fluid such as sea water and air. Diaphragms can be provided within the bladder to separate it into multiple chambers. Again the complexity of manufacture and maintenance is a disadvantage.

[0005] Also for all bag or bladder designs that contact the sea bed, marine life under the reef is detrimentally affected and the use of such artificial reefs over some sea bed features such as rocks and coral is undesirable or impractical because of risk of damage to the bladder from contact with the rocks or coral, particularly in rough sea conditions. Also if the lower side of the bag or bladder is in contact with the sea bed (or bed of any other body of water) like a ground sheet, it can damage or deter marine life living on the bed of the body of water.

[0006] GB 1 ,383,01 1 discloses an artificial reef manufactured from resilient or rigid sheets of material and supported at intervals along its length by inflatable bags in the form of balloons or hoses. The sheets of material are made up of multiple elongate strips of material impermeable to water and are arranged to make them permeable to a vertical flow of water and impermeable to horizontal flow to provide coastal protection against erosion. However such devices are still relatively complex to manufacture and maintain.

[0007] Other resilient artificial reefs are formed in the desired shape from thicker material which allows a simpler construction, but creates relatively rigid structures and increases the difficulty of installation.

[0008] Furthermore, all artificial reefs that utilise a bag, bladder or other closed volumes to contain sand or fluids are more likely to damage the

surrounding environment if those artificial reefs are damaged or dislodged due to rough weather or storms.

[0009] The present invention was developed with a view to providing an artificial reef which is of the resilient type and is relatively simple to manufacture and install.

SUMMARY OF THE INVENTION

[0010] According to a first aspect of the invention there is provided an artificial reef comprising an underwater sail and a plurality of anchor points, the

underwater sail including a plurality of tie-down points, wherein, in use

underwater: at least one of said tie-down points is connected to at least one of said plurality of anchor points by at least one tie-down link; and material or gas of lower density than the water is trapped under the underwater sail to provide an upwards force to expand or inflate the sail in an upwards direction.

[001 1 ] The material of the sail retains the low density material or gas in or under the sail to form a raised body of the reef which does not require any form of bag, balloon or bladder. For example using air under the sail can easily provide sufficient tension in the sail to expand or inflate it into the desired shape

(determined for example by the amount of inflation and sail design). The tension in the sail comes from buoyancy of the low density of the inflating material or gas under water and the reaction of the anchor points.

[0012] The underwater sail may be constructed from or include material that is impermeable to water or has a low permeability to water.

[0013] The at least one tie-down link may include a flexible tie such as a strap, rope or chain. Alternatively or additionally, the at least one tie-down link may include a rigid tie device such as a rod. Alternatively or additionally, the length of the tie-down link may be adjustable.

[001 ] The anchor points may be fixed relative to a bed or floor of a body of water to position and restrain the sail. The body of water may be a naturally occurring body of water such as the sea, a lake or a river, or it may be a man- made body of water such as a reservoir or wave pool.

[0015] The artificial reef may be installed in a flowing body of water (such as a river) to create a standing wave.

[0016] The sail may have edges between the plurality of tie-down points. At least one or more, or a portion, of said edges may be spaced above a bed or floor of a body of water to permit access (for example of marine life, people, or equipment) and/or flow (for example of water, silt or sand) under the sail. [0017] The sail may be circular in plan view. Alternatively, the sail may have other shapes. For example, the sail may be tear-drop shaped, triangular or boomerang shaped in plan view.

[0018] The sail may have a domed profile in side view when constraining the low density material, the profile having a high point and a similar curve sloping away from the high point on either side. Alternatively, the sail may have an asymmetric profile in side view, sloping away from a high point at a greater rate in one direction than in an opposite direction.

[0019] At least one of the plurality of anchor points may include a sand anchor or helical anchor, such as a sand screw. Alternatively, at least one of the plurality of anchor points may include an eye bolt cemented/concreted in position.

[0020] An image may be formed into or onto a surface of the underwater sail. This could, for example, include a visible warning message or symbol, or a sponsor's image, a logo or an advertisement.

[0021] The sail may be constructed from material that is substantially impermeable or has a low permeability to air (or other gasses).

[0022] The sail may be a membrane as a sheet of material. The membrane may be formed of a single layer of material or of multiple laminates, or be formed by weaving and subsequently bonding the weave together and/or sealing or coating with a waterproof material.

[0023] A pipe, hose or other conduit may be included to supply compressed air under the sail to inflate it or to maintain or adjust a volume of relatively low density gas trapped under the sail. The conduit may have a buoyant device attached at or near a first end, the first end being under the sail. The second end of the conduit may selectively be vented to the atmosphere to enable the volume gas trapped under the sail to be reduced to deflate the sail. [0024] According to a second aspect of the invention there is provided a method of modifying wave characteristics in a body of water, the method including the steps of: locating a plurality of anchor points in a bed or floor of a body of water; providing a plurality of tie-down points around an edge of an underwater sail; connecting the sail to the bed or floor of the body of water using tie-down links between the anchor points and the tie-down points; and supplying gas of lower density than water under the sail to expand or inflate the sail in an upwards direction off the bed or floor of the body of water.

[0025] The method may include providing a conduit, a first end of the conduit being positioned under the sail.

[0026] The method may include the step of providing a buoyant device towards the first end of the conduit to thereby position the first end of the conduit in a volume of the gas under the sail.

[0027] The method may further include the step of selectively venting a second end of the conduit to atmosphere to thereby reduce the volume of gas under the sail or deflate the sail.

[0028] The method may further include the step of adding at least one additional underwater sail to further modify the wave characteristics.

[0029] Alternatively or additionally, the method may further include the step of choosing a location and/or profile for the underwater sail to increase wave peaks (to enhance the wave characteristics for surfing for example).

[0030] Alternatively or additionally, the method may further include the step of choosing a location and/or profile for the underwater sail to increase the distance from shore at which waves break, for example, to reduce beach erosion. [0031 ] According to a further aspect of the invention there is provided an artificial reef sail, the sail including a plurality of tie-down points. [0032] The sail may further include at least a portion of material that is substantially impermeable to air, at least when wet, such that it may be expanded or inflated by compressed air when under water.

[0033] The sail may further include at least a portion of material that has a low permeability to gas such that it may be expanded or inflated by gas when under water.

[0034] It will be convenient to further describe the present invention by reference to the accompanying drawings which illustrate preferred embodiments of the present invention. Other embodiments of the invention are possible and consequently particularity of the accompanying drawings is not to be understood as superseding the generality of the preceding description of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In the drawings:

[0036] Figure 1 is a side view of an artificial reef in accordance with an embodiment of the present invention.

[0037] Figure 2 is a side view of a modified or alternate artificial reef in accordance with an embodiment of the present invention.

[0038] Figure 3 is a plan view of the artificial reef of Figure 1 .

[0039] Figure 4 is a plan view of an alternate shape of artificial reef of an embodiment of the present invention. [0040] Figure 5 is a side view of the artificial reef of Figure 4.

[0041] Figure 6 is a diagrammatic plan view of a typical location and effect of artificial reefs according to an embodiment of the present invention.

DESCRIPTION OF PREFERRED EMBODIMENT

[0042] Referring initially to Figure 1 . there is shown a side view of an underwater sail 3 installed in a body of water 2, such as the sea or a lake, to form an artificial reef 1. In this description, the underwater sail will be described in an ocean installation. The sail 3 is anchored to the bed or floor 4 of the body of the water (i.e. the sea bed) at anchor points 5, such as the helical anchor 6 or the cemented eye 7 shown. The helical anchor or sand screw (6) provides a high anchoring force, is relatively easy to install in sandy sea beds for example and can be removed if required, such as when removing or repositioning the underwater sail installation. However, if the underwater sail is to be installed over rocks for example, an alternative form of anchor such as the cemented/concreted eye 7 is required. Over coral, a long narrow helical anchor may be used or again a cemented/concreted eye may be used which may minimise any damage to the coral and the use of the sail may be to protect the reef.

[0043] The line 8 shows the surface of the water, in this ocean application shown at an average mid-tide sea level.

[0044] The edge 9 of the sail 3 includes tie-down points 10, each of which is connected to at least one of the anchor points 5 by a tie down link 1 1 such as a strap or rope.

[0045] Preferably a gap 12 is present between at least a portion of the edge of the sail and the sea bed 4 to permit sand flow underneath and around the sail. Such a gap 12 can also allow access under the sail 3 and allow the sail to provide a refuge for marine life. The tie-down link 1 1 can be adjustable, which can for example make installation easier or allow the size of the gap 12 or the height of the sail to be adjusted.

[0046] Air is pumped under the sail to provide lift and inflate the sail 3. The air forms a large bubble or air pocket 13 under the sail, expanding it away from the sea bed 4. The edge of the air pocket 13 is represented by the dashed line 14 in Figure 1 . The quantity of air required to provide effective buoyancy under the sail and tension the sail upwards sufficiently for the artificial reef to provide the desired influence on the waves does not generally require an air pocket of great height. Therefore the edge of the air pocket is typically sufficiently above the edge of the sail to ensure the air remains captured under the sail when in operation.

[0047] The sail can be formed such that when inflated the side profile sail takes on a form from a variety of forms to provide the desired modification of the characteristics of .the wave passing over the sail. For example, in Figure 1 , the side profile of the sail in use is domed or convex, having a high point 15.

However, altering the bottom characteristics through the use of a steeper slope facing the on-coming wave can increase the breaking intensity of the wave, so the side profile of the sail can be designed to produce better surfing waves for example, increasing the wave peak characteristics or the length of ride.

[0048] Figure 2 shows a similar sail to Figure 1 , but having a different side profile. Throughout the Figures, similar or corresponding features are given like reference numerals. The sail in Figure 2 has a steeper slope 17 facing the oncoming swell and a lesser or relatively gentle slope 18 facing the shore.

[0049] Figure 3 shows the sail of Figures 1 or 2 in plan view. This example shows a sail of substantially circular shape in plan view. Using a circular shaped sail can be preferable where the direction of the swell is not fixed as it readily accommodates different directions of swell. However, if the swell direction is constant, for example in a recreational lake with a man-made wave generator, a sail having a tear-drop shape as shown in Figure 4 may be used.

[0050] The sail can be any shape in plan view, for example it may be lozenge or oval shaped in which case its major axis may extend parallel to the shore.

[0051] Different shape sails in plan view can also be suited to, or enhance the stability and effect of different side profiles of the sail. For example, the tear-drop shaped sail of Figure 4 in plan view is shown in side profile in Figure 5.

[0052] The portion of the sail 17 facing the on-coming swell in this example is the tail, so can provide a much more gradual slope up to the high point 15 which will provide a wave of increased height but mild breaking characteristic. The dotted line 20 shows a typical profile of a domed, round sail having a steeper slope facing the on-coming swell.

[0053] Other preferable shapes of the sail in plan view which can be used to improve wave shapes when the swell is in a regular direction are triangular or boomerang shapes. Figures 6 and 7 show a triangular sail in plan and side view, with the point facing out to sea and with the opposite side 24 preferably parallel to the shore to limit currents of water flowing along the shore displacing sand for example. If the high point 15 of the sail is towards the corner of the sail facing the on-coming swell, the sail can present a steep slope 17 facing the on-coming swell. This provides a high volume of air in the region of the air pocket (or bubble 13) under the sail 3 which bears the brunt of the wave forces. The function of the triangular sail provided by the relatively abrupt, steep angle of attack or slope 17 facing the on-coming swell can be further enhanced by providing a ridge 25 along the centre of the triangular sail, perpendicular to the shore and/or wave, with the lateral sides 26 gently sloping towards the sea floor 4. [0054] As with the other figures, a sample seam structure is shown, but this can be changed to tune the precise shape of the sail when inflated and the stiffness of the sail in different modes of deflection.

[0055] As discussed briefly above, the profile of the bed or floor of a body of water produces an effect on the waves passing overhead. For example, an increase in the height of the ocean floor, such as a bank or reef near the shore, reduces the water depth which causes waves to slow down, increase in height and change shape. Waves generally break when the water depth is less than 1.3 times the wave height (peak to trough). The gradient affects how the wave breaks, such as a spilling, plunging, collapsing or surging.

[0056] Figure 8 shows how one or more underwater sail type artificial reefs according to the present invention may be located and their effect on wave breaking. The incoming swell 31 travels towards the beach 32 and the waters edge 33. The swell would naturally slow and lift as the water depth reduces towards the shore, breaking in an area around the dashed line 34 denoting a natural rise in the ocean floor or the edge of a reef. Two similar underwater sails 3 and 3' are shown, positioned to move the wave peak and break point 35 of the swell further out around the region of each sail. Either side of each sail, the swell is slowed less until it travels further inshore, so the wave peak is angled and the linear swell fronts in the example become distorted, as shown by the swell lines 36 and 37. Typically, the sails 3 and 3' can be between 200 and 500 metres apart. If the sails are used further apart, or if only one sail is used, then around each sail, the swell peaks and breaks early and the further away from the sail along the line of swell, the less the swell is slowed early, so it crosses the natural rise or reef (at the dashed line 34) at an angle. The artificial reef 1 can protect the naturally existing reef around the area of the sail.

[0057] The number, position and shape of sails in an installation can be used to tune the wave characteristics, from creating better waves for surfing, to providing protection for reefs and the shoreline from damage such as erosion. [0058] Although the above description largely describes the use of the underwater sail of the present invention in an ocean installation, the underwater sail may be used in any natural or man made body of water including lakes, reservoirs and wave pools. When used to modify wave characteristics for surfers in a recreational lake for example, the lake may include at least one device or apparatus for generating waves. Alternatively, the underwater sail can be used in flowing water such as in a river or other naturally occurring or man-made channel, for example to create a standing wave in a river.

[0059] The underwater sail of the present invention can be used not only for creating rideable waves, but alternatively for reducing erosion in any body of water. Erosion can be an issue for the banks of rivers and lakes (due for example to waves created from recreational activities) as well as for the ocean shoreline. Artificial reefs to dissipate wave energy and thereby reduce erosion can be relatively long and thin in form (such as a sausage shape) in plan view.

[0060] The underwater sail type artificial reef of the present invention has a minimal environmental impact when compared to other types of artificial reef. It can use a low impact or removable anchoring system and is resilient so does not present a danger to swimmers or boats. It can be easily removed in case environmental issues become apparent and if damaged in a storm, the sail has little mass or volume so should not be destructive if it becomes detached from the anchors. The air (or other buoyant material) trapped under the sail will inherently be released with failure of the anchors or tie down links so only the flexible material of the sail remains, which is unlikely to cause any damage. This is in contrast to prior artificial reef systems utilising flexible material in which a bag, balloon or bladder is formed to contain or encapsulate sand, fluids or gasses, which maintain the volume of the reef should it break its anchors in a storm.

[0061 ] The sail can be made from or include various materials, e.g. PVC fabric, Kevlar or Mylar spinnaker material. In the latter case, a sail of twenty metre diameter may weigh only 4kg. The composition of the sail material needs to provide structural (tension) and membrane (low permeability) properties. For example the sail material can be a single fabric which is impermeable to water and has low or zero permeability to gases (such as those of which air is comprised). Alternatively the sail can include multiple layers or laminates such as a structural layer or element and a membrane layer or element. The sail can be a membrane formed by weaving and subsequently bonding the weave together and/or sealing or coating with a waterproof material or other sealing material (typically one that can form a flexible skin) .

[0062] Although environmental groups have questioned the net benefit of prior artificial reefs, the present invention negates the typical concerns of toxicity and damage to ecosystems potentially caused by prior artificial reef systems. The artificial reef of the present invention should emit or leach substantially no chemicals into the water. It does not smother the sea bed, only contacting the ground at the anchor points which themselves can be high strength, low environmental impact and removable screw type anchors and if damaged in a storm, the artificial reef of the present invention does not provide an enclosed volume, but collapses to a minimal volume and mass.

[0063] The sail can be inflated using any material having less density than water. A gas, such as compressed air, is preferred as it is readily supplied using either a gas bottle or a compressor connected to a pipe passed under the sail. The compressor and pipe may be used from a boat as an installation and maintenance tool, or more permanently installed for continual maintenance of the artificial reef installation.

[0064] Similarly, to deflate the sail, a hose (or other conduit) with a (for example buoyant) termination in the air pocket can be used to provide a path for the gas to escape. For example, a hose with a buoyant device near a first end can have that end passed under the edge of the sail, the second end being retained in a position (typically) at substantially atmospheric pressure, such as on the surface of the water, on the shore or on a boat. The buoyant device rises in the water under the sail and feeds the first end of the hose up to the air pocket under the sail, thus communicating the air pocket with the atmosphere. As the air pocket under the sail is pressurised by the head of water above the sail, the air in the bubble or pocket is at higher pressure than the pressure at the second end of the hose. If flow is permitted along the hose (i.e. if any valves present are open), the air in the pocket will flow along the hose and into the atmosphere, draining the pocket of air under the sail. In this way, the sail can for example be left tethered or otherwise attached to the ocean floor when a storm is expected, but deflated to reduce loads on the sail and the anchor points. Suction can also be employed by connecting the second end of the hose to a vacuum (or partial vacuum) as an option, if required.

[0065] The sail can be deflated using this same type of mechanism or method prior to removal or as part of maintenance procedures. The hose can be a permanent fixture, for example, being sewn to the sail (which can negate the use of the buoyant device), and used for control of both inflation and deflation of the sail.

[0066] An image can be formed into or onto the surface of the sail. For example, the sail can be printed with a warning or safety message, a sponsor's image, a logo or an advertisement to offset purchase cost or create on-going income.