A breakwater comprising a base member having an outer surface, and a plurality of elongate members is disclosed. An end region of each of the plurality of elongate members is coupled to the outer surface of the base member. The base member and/or at least one of the elongate members has a textured surface for the attachment of marine life. The breakwater may be located on a seabed, a riverbed, an ocean floor or a floor of a waterway, to protect a coast or riverbank from coastal erosion.

TECHNICAL FIELD

The present disclosure relates to breakwaters, in particular, but not exclusively to submerged breakwaters.

BACKGROUND

Coastal erosion, the removal of material from a coast, is a continuous process that is primarily caused by wave action and tidal (and other) currents. Generally, breakwaters are constructed along a coast to reduce or prevent coastal erosion. Breakwaters attenuate energy of waves and currents reaching the coast, subsequently protecting the coast from erosion.

However, breakwaters generally reflect and diffract energy from waves, rather than letting some wave energy through and reflecting and absorbing some wave energy, causing erosion elsewhere. Further, breakwaters typically appear above the surface of the water, causing an aesthetically displeasing sight on the shoreline. Submerged breakwaters attenuate wave energy reaching a coast without affecting the view of the shoreline. They can also act as artificial reefs to provide a habitat for fish, coral, plankton, kelp and other marine life. However, submerged breakwaters such as Reef Balls have limited surface area available for marine life to grow on. Further, they are generally not secured to the seabed and can therefore be dislocated from their intended location and orientation due to the effect of waves and currents.

Another form of erosion is hydrodynamic scour, the removal of sediment such as silt, sand and gravel from around the base of obstructions to water flow in the sea, rivers and canals such as the support structures of piers and bridges. This removal of sediment can cause scour holes to be formed, which often result in a lack of stability of the support structures and can ultimately lead to the failure of the foundations of the support structures and the bridge or pier itself.

The present disclosure has been devised to mitigate or overcome at least some of the above-mentioned problems.

SUMMARY

According to an aspect of the disclosure, there is provided a breakwater comprising a base member having an outer surface, and a plurality of elongate members. An end region of each of the plurality of elongate members is coupled to the outer surface of the base member. The base member and/or at least one of the elongate members has a textured surface for the attachment of marine life.

When in use, the breakwater may be located on a seabed, a riverbed, an ocean floor or a floor of a waterway, to protect a coast or riverbank from coastal erosion. The breakwater can also be used to protect offshore structures such as oil rigs, subsea structures, offshore wind turbine monopiles, piles and towers, as well as the support structures of piers and bridges from hydrodynamic scour. The breakwater induces a reduction in water velocity and water celerity, and creates a turbulent flow in water passing around and through the breakwater. The reduced water velocity and celerity and the turbulent flow leads to a reduction in the speed and energy of the water flow around the breakwater, thereby attenuating wave energy that would otherwise cause erosion. The attenuation of wave energy also aids the prevention and reversal of hydrodynamic scour by slowing down water flow around the breakwater, enabling sediment and soil deposition in the lee of the breakwater. This can provide additional sediment to build up to the seabed surrounding the breakwater.

The breakwater provides a substrate and habitat for marine life such as coral and kelp, the growth of which can compensate for wear-and-tear of the breakwater such that the breakwater may not need to be replaced. Advantageously, the elongated members of the breakwater may increase the surface area of the breakwater by at least 300 times that of the surface area of the base member alone. This substantially increases the substrate surface area available on which marine life can grow. This increased surface area acts to accelerate the rate at which the breakwater may be covered in marine life, as well as increasing the amount of marine life that can grow on the breakwater. The increased amount of marine life and increased rate of coverage by marine life may increase the longevity of the breakwater, for example by compensating for wear-and-tear. Accordingly, the (man-made) breakwater may become an integral part of the marine subsea life, so that decades after being installed, the breakwater may be completely over taken by the marine life, and a new coral reef or marine structure may be formed which can then continue to grow. The (man-made) breakwater thus becomes a reef forming a natural breakwater. This creates long term changes in the marine subsea lay-out and permanent protection against erosion.

The elongate members radiating outward from the base member of the breakwater may increase the effective substrate area and volume occupied by the breakwater whilst minimising the amount of material required, such as concrete, to provide a structure able to withstand storms and ocean currents. The increased amount of marine life and increased rate of coverage by marine life enabled by the increased surface area of the plurality of elongate members may increase the stability of the breakwater, for example as marine life may act to anchor the breakwater to the seabed as well as increasing the effective mass of the breakwater. The breakwater may be fully or partially submerged in use. For example, a portion of the breakwater may not be submerged during low tide, but the breakwater may be fully submerged during high tide. In other applications, a portion of the breakwater may permanently be above the surface of the water.

The base member may be solid or hollow. Beneficially, a hollow base member provides a shelter inside for marine life. A solid base member has more weight than a hollow base member of the same size, making a solid base member more resistant to movement by sliding or overturning. The base member may have a width of 1 to 10 metres, and a length of 1 to 20 metres, preferably 2 metres for ease of fabrication and handling and transport. Hollow base members may have a wall thickness of 0.1 to 1 metres.

The base member may have a cylindrical shape, or a prism having a regular or irregular polygonal cross section, for example, triangular, rectangular, hexagonal, octagonal, or decagonal cross sections. Advantageously, a triangular cross section provides stability for the base member on the seabed (or riverbed). In some embodiments, the shape of the base is, for example, a pyramid, a flat-bottomed ovoid, a frustum, or a dodecahedron.

Optionally, a plurality of flanges adjoin an edge of the base member, spaced apart from each other. The plurality of flanges are arranged to interlock with a corresponding plurality of flanges on an edge of another base member and enable a secure connection between base members. For example, the plurality of flanges may be a plurality of chevrons, each chevron having a triangular or trapezoidal shape and a base which adjoins the edge of the base member. In other examples, the plurality of flanges may each have a rectangular shape. The plurality of flanges may be attached to or integrally formed with the base member. A plurality of breakwaters can be arranged to protect a coast or offshore structure, either spaced apart from each other or connected to each other, for example by interlocking flanges.

The base member may be comprised of one or more of concrete, metal, plastic such as polyethylene, wood, and bamboo. Optionally, the surface of the base member is textured, rather than smooth, to encourage attachment of marine life.

The end region of an elongate member may include a region proximate to an end of the elongate member and/or the end of the elongate member. The elongate member may be coupled to the outer surface of the base member by using glue and/or fastening means such as bolts and nuts, screws and/or nails. Coupling between the elongate members and base member may be through flanges on the elongate members, and/or quick connect-disconnect systems. The base member may comprise a plurality of recesses into which respective elongate members are inserted for coupling. Additionally or alternatively, the base member may comprise a plurality of protrusions which may be each be inserted into respective hollow or partially-hollow elongate members for coupling.

One or more of the plurality of elongate members may be solid or hollow. Beneficially, a hollow elongate member provides shelter inside for marine life. One or more of the plurality of elongate members may have a width of 0.1 to 1 metres, and a length of 0.5 to 20 metres. In other words, the elongate members on a base member may have different widths and lengths. Hollow elongate members may have a wall thickness of 0.01 to 0.5 metres.

One or more of the plurality of elongate members may have a circular cross section, or a regular or irregular polygonal cross section, for example, triangular, rectangular, hexagonal, octagonal, or decagonal cross sections.

One or more of the plurality of elongate members may be comprised of one or more of concrete, metal, plastic such as polyethylene, wood, and bamboo. Optionally, the surface of one or more of the plurality of elongate members is textured, rather than smooth, to encourage attachment of marine life.

The plurality of elongate members may be integrally (ie monolithically) formed with the base member. For example, a base member and its plurality of elongate members may be cast together in plastic, metal or concrete, or fabricated from a single piece of wood or bamboo.

When the base member is hollow, the base member optionally comprises a plurality of apertures in the outer surface. These apertures enable marine life to pass into the centre of the base member for shelter. At least one of the plurality of elongate members may extend through a respective one of the plurality of apertures in the outer surface. There may be more apertures than elongate members such that even when all elongate members extend through a respective aperture, the base member comprises apertures that do not have an elongate member. Alternatively or additionally to fastening means, the coupling between the elongate members and the base member may be through an interference fit between an aperture of the base member and an end region of an elongate member. One or more of the elongate members may pass into the hollow centre of the base member.

When the base member is solid or hollow, the base member optionally comprises a plurality of recesses in the outer surface. At least one of the plurality of elongate members may extend into a respective one of the plurality of recesses in the outer surface. There may be more recesses than elongate members such that even when all elongate members extend into a respective recess, the base member comprises recesses that do not have an elongate member. Alternatively or additionally to fastening means, the coupling between the elongate members and the base member may be through an interference fit between an recess of the base member and an end region of an elongate member. These recesses may provide shelter for marine life.

Optionally, the plurality of elongate members are arranged in a plurality of rows along a length of the case member, a row being formed by at least two elongate members. A width of the elongate members in adjacent rows may be different.

Optionally, the outer surface of the base member comprises a first portion and a second portion. The plurality of elongate members may be coupled to the first portion, and no elongate members may be coupled to the second portion. For example, the second portion is a portion that would rest against the seabed or riverbed, and so it may be less desirable to have elongate members on the seabed or riverbed side of the base member. One or more of the elongate members on the first portion that are adjacent to the second portion may be stronger than other elongate members. Elongate members adjacent the second portion may rest against the seabed or riverbed, and so stronger elongate members adjacent the second portion advantageously act to anchor the breakwater and support it against lateral, longitudinal, twisting and overturning loads caused by waves and currents. For example, the stronger elongate members may wider, solid, and/or comprise a stronger material than other elongate members.

Elements in the figures are illustrated for simplicity and clarity and have not necessarily been drawn to scale. Like reference numerals have been included in the respective drawings to ease understanding.

DETAILED DESCRIPTION OF THE DRAWINGS

With reference toFIGS. 1(a), 1(b)and2, a breakwater100is arranged on a seabed102. The breakwater100comprises a base member110and a plurality of elongate members120. The base member110is tubular and has a circular cross section. In other examples, the cross section of the breakwater may be a prism having a regular or irregular polygonal cross section such as triangle, rectangle, hexagon, octagon, or decagon.

The base member110comprises a plurality of apertures112in its outer surface, ie through the wall of the base member, and a plurality of flanges114adjoining the edges of the base member110. The plurality of flanges114may be attached to or integrally formed with the base member110. In some examples, the breakwater may not comprise flanges114. The flanges114are spaced out around the edges of the base member110and each have a trapezoidal shape. In other examples, the flanges may have a triangular or rectangular shape. The spacing and shape of the flanges114is arranged such that the trapezoidal shapes tessellate with corresponding flanges on another base member, enabling the base members to interlock with each other.

Each of the plurality of elongate members120is tubular and has a circular cross section. The breakwater100comprises five different diameters of elongate member. In other examples, the cross section of the plurality of elongate members may be a prism having a regular or irregular polygonal cross section such as triangle, rectangle, hexagon, octagon, or decagon. In other examples, the diameters of all the elongate members may be the same, or there may be a plurality of different diameters of the elongate members on the breakwater.

An end region122of each elongate member120is coupled to the base member110on a portion of the base member110. The coupling between each end region122and the base member110may be use fasteners and/or through an interference fit (ie friction fit) between the outer diameter of the elongate member and the inner diameter of the respective aperture. A portion of one or more of the elongate members120may pass into the hollow centre of the base member110.

The portion of the base member110to which the elongate members120are coupled is not near the seabed102so that the base member110sits directly on the seabed102. The end region122of each elongate member120is located in a respective aperture112. The elongate members120closest to the seabed102contact the seabed102thereby anchoring the breakwater100. In addition, the base member110may be secured to the seabed102using anchoring means such as piles, pitons, chains, or anchors.

The base member110and the elongate members120may be comprised of one or more of concrete, metal, plastic such as polyethylene, wood, and bamboo. The surface of the base members and the elongate members may be textured, rather than smooth, to encourage attachment of marine life.

With reference toFIG. 3, in use, the breakwater100is submerged near a coast302to protect the coast302from approaching waves by attenuating energy of the waves. A wave304approaches the coast302and as it approaches the breakwater100, the wave crests reduce in region306due to absorption and reflection of the energy of the wave304by the breakwater100. Energy and velocity of the wave304has an effect below the surface, and a subsurface part308of the wave304contacts the breakwater100, causing turbulent flow and dispersal of the energy of the subsurface part308. As a result, only a fraction of the energy of the wave304reaches the coast302. The wave energy may be attenuated from 20% to 90% with a corresponding loss in wave height by 20% to 60% depending on the depth of the water.

With reference toFIG. 4, a breakwater400is arranged on a seabed102. The breakwater400comprises a base member410and a plurality of elongate members420. The breakwater400is substantially the same as the breakwater100. However, the base member410of the breakwater400is a hollow prism with a substantially triangular cross section with a rounded upper vertex. The breakwater400may also comprise flanges on the edges of the base member410similar to the breakwater100.

With reference toFIG. 5, a breakwater500is arranged on a seabed102. The breakwater500comprises a base member510and a plurality of elongate members520. The breakwater500is substantially the same as the breakwater100. However, the base member510of the breakwater500is a hollow prism with a triangular cross section. The breakwater500may also comprise flanges on the edges of the base member510similar to the breakwater100.

With reference toFIGS. 6(a) and 6(b), a breakwater600is arranged on a seabed102. The breakwater600comprises a base member610and a plurality of elongate members620. The breakwater600is substantially the same as the breakwater100. However, the breakwater600is arranged to rest of the seabed102on an edge of the base member610and accordingly, the base member610of the breakwater600does not have flanges for interlocking with other breakwaters. In some examples, the base member610may comprise flanges on its edges, for example on the edge resting on the seabed102, to provide a more secure foundation with the seabed.

With reference toFIGS. 7(a) and 7(b), an anchor700for the breakwater600comprises a base portion702, a lower middle portion704, an upper middle portion706and a top portion708. The anchor700is arranged to slot into the base member610of the breakwater600, thereby securing it to the seabed. Note that inFIG. 7(b), the breakwater600is illustrated without the elongate member620.

The base portion702is arranged to be fastened to the seabed and has a disc or ring shape with a diameter that is approximately the same as the outer diameter of the tubular base member610. The base portion702also comprises feet for engagement with the seabed102. The lower middle portion704has a frustoconical shape in which the largest diameter is substantially the same as the inner diameter of the tubular base member610, in order to seat the base member100on the anchor700. The upper middle portion706has a cylindrical shape with a diameter that is smaller than the inner diameter of the tubular base member610. The top portion708has a frustoconical shape in which the largest diameter is the same as the diameter of the upper middle portion706. The top portion comprises an aperture710in the side for engagement by a lifting hook. The base portion702, the lower and upper middle portions704,706and the top portion708are integrally formed, and are coaxial.

The base members and elongate members of breakwaters100,400,500and600are hollow but the skilled person would recognise that they may also be solid. The base members of breakwaters100,400,500and600may have a width of 1 to 10 metres, and a length of 1 to 20 metres. The width and length may be increased for applications where breakwaters are fabricated in long sections. Hollow base members may have a wall thickness of 0.1 to 1 metres. The plurality of elongate members of breakwaters100,400,500and600may have a diameter of 0.1 to 1 metres, and a length of 0.5 to 20 metres. In other words, the elongate members on a base member may have different widths and lengths. Hollow elongate members may have a wall thickness of 0.01 to 0.5 metres.

The elongate members of breakwaters100,400,500and600are arranged in rows, but the skilled person would recognise that elongate members may be arranged in any pattern on a base member.

Breakwaters100,400,500and600are described as being arranged on a seabed102but the breakwaters100,400,500and600are also arrangeable on a riverbed, an ocean floor or a floor of a waterway in use.

Additionally, although individual features may be included in different claims, these may possibly be advantageously combined, and the inclusion in different claims does not imply that a combination of features is not feasible and/or advantageous. Also, the inclusion of a feature in one category of claims does not imply a limitation to this category, but rather indicates that the feature is equally applicable to other claim categories, as appropriate.