CROSS-REFERENCE TO RELATED APPLICATIONS

[0001] This international application claims the benefit under 35 U.S.C. §119(e) of Application Serial No. 63/280,961 filed on November 18, 2021 , entitled COASTAL PROTECTION USING ARTIFICAL REEF MADE OF OYSTER SHELLS IN BIODEGRADABLE MESHBAGS, the entire disclosure of which is incorporated by reference herein.

BACKGROUND OF THE INVENTION

1. FIELD OF INVENTION

[0002] This invention relates to coastal protection and more particularly to artificial reefs made from environmentally friendly materials.

2. DESCRIPTION OF RELATED ART

[0003] In coastal areas, coastal erosion can be a major issue affecting both beaches and marine life. Coastal erosion can occur when incoming waves constantly strike the land or rocks along the coastline, removing sand, soil, or rocks in the process. Coastal structures, such as the placement of artificial reefs, have become a useful tool used by environmentalists for beach protection and restoration.

[0004] The major problem with current coastal structures, namely artificial reefs, is the use of non-biodegradable and non-environmentally friendly materials. Such materials used include steel, concrete, used tires, rubber, construction debris, scuttling ships, etc. Over time, the saltwater from the ocean can corrode these types of materials, thus causing the materials to leach into the ocean. This result can cause marine pollution and prevent marine organisms from growing around the artificial reefs. Ideally, artificial reefs are made from environmentally friendly materials which are strong enough to protect the beach or shore from coastal erosion without contributing to marine pollution.

[0005] Prior attempts have been made to create artificial reefs for the use of coastal protection. For example, U.S. Pat. No. 9,403,287 discloses a process for forming an artificial reef using blockouts, concrete, and limestone. A pyramid-shaped form is shaped, then blocks and blockouts are applied to the form, then sprayable concrete is applied over the form, blockout, and at least part of the block. The structure in Hilton is made using concrete and therefore not made from biodegradable or environmentally friendly materials. [0006] U.S. Pub. No. 2017/0055502 discloses a shoreline restoration method utilizing a plurality of apparatuses facilitating formation of a vertical oyster reef using a frame formed of rod members with an inner frame and an outer frame. The rod members are steel reinforcing bars. The bags used for holding the oysters are made from plastic. Cultch material, which can be concrete, fills the bags. Steel, plastic, and concrete can all break down and leach into the ocean over time, contributing to marine pollution.

[0007] U.S. Pat. No. 5,269,254 discloses a method and apparatus for growing an oyster reef using water permeable panels for holding cultch material. The support members used to form the panels are constructed from materials such as plastic, metal, and concrete reinforcing rods. None of these materials are environmentally friendly and can contribute to marine pollution.

[0008] Despite the foregoing developments, there is still a need for systems and methods to prevent coastal erosion in a way that effectively protects shorelines, prevents marine pollution, and is environmentally friendly.

[0009] All references cited herein are incorporated herein by reference in their entireties.

BRIEF SUMMARY OF THE INVENTION

[00010] Accordingly, a first aspect of the invention is a module for building a reef including a receptacle for receiving oyster shells, wherein the receptacle comprises a biodegradable material and is water-permeable and sufficiently durable to securely retain the oyster shells therein when installed in the ocean.

[00011] In certain embodiments, the receptacle is a bag.

[00012] In certain embodiments, the biodegradable material is fabricated of sinamay. The biodegradable material can also be fabricated of a material selected from the group including but not limited to jute, coconut husk, cotton, manila hemp, sisal fiber, hay, straw, and dry stalks of wheat, rice, oats, barley, and rye.

[00013] In certain embodiments, the module includes a fastener configured to attach adjacent modules to each other. The fastener is preferably a tether, which is an extension of the bag. The fastener can also include strings, clips, or the like, preferably made from a biodegradable material. In certain examples, the fastener is simultaneously capable of tightening the receptacle opening and attaching the receptacle to adjacent modules.

[00014] A second aspect of the invention is a structure including more than one said module for building a reef including a receptacle for receiving oyster shells, wherein the receptacle comprises a biodegradable material and is water-permeable and sufficiently durable to securely retain the oyster shells therein when installed in the ocean.

[00015] In certain embodiments, the structure is a wall or pyramid shape. [00016] A third aspect of the invention is a method of coastal protection by creation of an artificial reef including: providing a receptacle for receiving oyster shells, wherein said receptacle is water- permeable and comprises a biodegradable material; providing oyster shells in said receptacle; and placing more than one said receptacle filled with oyster shells in a body of water to form the artificial reef structure.

[00017] In certain embodiments, the biodegradable material is preferably sinamay fabric. [00018] In certain embodiments, the fastener is a tether, which is an extension of the bag. The fastener can also include strings, clips, or the like, made from a biodegradable material.

BRIEF DESCRIPTION OF SEVERAL VIEWS OF THE DRAWINGS

[00019] The invention will be described in conjunction with the following drawings in which like reference numerals designate like elements and wherein:

[00020] Fig. 1 is an aerial view of an embodiment of the module including the receptacle filled with oyster shells.

[00021] Fig. 2 is a side view of the embodiment of Fig. 1 depicting the integration of a fastener in the form of a tether, which is an extension of the receptacle.

[00022] Fig. 3 is an aerial view of an embodiment of the receptacle, in the form of a bag, made from biodegradable material.

[00023] Fig. 4 is a side view showing an example of the oyster shells used to fill the receptacles.

[00024] Fig. 5 is a side view of an embodiment of the structure of the invention including more than one module, including a receptacle made from biodegradable material and oyster shells, positioned to form an artificial reef structure in a wall shape.

[00025] Fig. 6 is a schematic of the experimental setup depicted in Fig. 5.

[00026] Fig. 7 is a plot of the wave transmission coefficient for different wave steepness conditions for 30 cm water depth.

[00027] Fig. 8 is a plot of the wave transmission coefficient versus wave steepness for 29 cm water depth.

[00028] Fig. 9 is a plot of the wave transmission coefficient versus wave steepness for a 28 cm water depth.

[00029] Fig. 10 is an overhead view of the setup to check the rate of degradation of the biodegradable bags. [00030] Fig. 11 is an isometric view of the comparison between two modules kept under varying conditions.

[00031] Fig. 12 is a magnified view of the circled area of the Unit 1 module of Fig. 11.

[00032] Fig. 13 is a diagram of various ocean zones.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS OF THE INVENTION [00033] Coastal areas constantly subjected to the strike of waves or tidal forces may experience severe erosion. Coastal structures, such as artificial reefs, are effective in reducing wave heights, thereby protecting the beach or shore from erosion. The module, structure, and method of the invention uses receptacles including environmentally friendly material for receiving oyster shells 4 to form an artificial reef to protect the coastal area. In certain examples, the oyster shells 4 are the shells of live oysters. In other preferred examples, the oyster shells 4 are not from live oysters.

[00034] A first aspect of the invention includes a module 12 for building a reef including a receptacle 2 for receiving oyster shells 4, wherein the receptacle 2 comprises a biodegradable material and the receptacle 2 is water-permeable and sufficiently durable to securely retain the oyster shells 4 therein when installed in the ocean. The oyster shells 4 act as a natural breakwater, buffering incoming waves from eroding the shoreline. The oyster shells 4 additionally provide a natural habitat structure for surrounding life in the body of water. In examples of the invention using live oysters, the oysters additionally improve the quality of the surrounding water through their filter feeding mechanism. Further, as oysters have the ability to attach to hard substrates such as rock, oysters which are part of the reef of the invention can stabilize the reef over time as the colony of oysters is formed. In examples of the invention using non-live oysters, the weight of the individual module 12 decreases, reducing the risk of the biodegradable receptacle 2 being damaged due to the weight of the individual module 12. Additionally, empty oyster shells 4 from non-live oysters are often readily available from restaurants, reducing the cost of the individual module 12.

[00035] In certain embodiments, the receptacles 2 are bags 6. The bags 6 for receiving oyster shells 4 are made from a biodegradable material, preferably from sinamay fabric. Sinamay is a natural straw fabric made from Abaca fibers. Abaca is a kind of banana plant, and the sinamay bag made from this fabric is entirely biodegradable. The term “biodegradable” as used herein means capable of being broken down into basic substances through normal environmental processes. Other biodegradable materials suitable for use in the invention include but are not limited to jute, coconut husk, cotton, manila hemp, sisal fiber, hay, straw, and dry stalks of wheat, rice, oats, barley, and rye.

[00036] The bags 6 are partially or completely filled with oyster shells 4 and positioned together. In certain embodiments of the invention, the bags 6 of oyster shells 4 are attached together with fasteners 8. In certain examples, the fastener 8 is preferably a tether, which is an extension of the bag. In additional examples, the fastener includes strings, rope, or clips made from a biodegradable material.

[00037] In certain embodiments, the bags 6 of oyster shells 4 will be positioned together in a body of water such that the bags 6 form an artificial reef structure 10. This structure 10 preferably comprises at least two courses of bags 6 forming a pyramid shape. The artificial reef will then act as a means to reduce wave height and significantly reduce the energy of incoming waves. The artificial reefs can be placed in a desired area depending on the area of coastline to be protected. In order to blunt the force of waves, the artificial reef structure should be placed in a location inside or close to the ocean surf zone 28. The surf zone 28 is the relatively narrow strip of a body of water that borders the shore 36, and which contains waves 34 that are breaking due to the shallow water depth. The surf zone 28 is located between the breaker zone 26 and swash zone 30. The breaker zone 26 is the zone in which the waves 34 break. The swash zone 30 forms the land-ocean boundary at the landward edge of the surf zone 28, where waves 34 run up the beach face of the shore 36.

[00038] Once the bags 6 of oyster shells 4 have been placed, organisms within the body of water will start to attach to the bags 6 of oyster shells 4 and expand the artificial reef. The biodegradable bags 6 will degrade, leaving just the oyster shells 4. As the artificial reef structure grows and expands, the overall stability and lifespan of the reef will increase. The resulting reef absorbs some of the force of the waves, protecting the shoreline from erosion.

[00039] The invention will be illustrated in more detail with reference to the following Examples, but it should be understood that the present invention is not deemed to be limited thereto.

EXAMPLES

[00040] An experiment was conducted to demonstrate the effectiveness of receptacles and artificial reef structures of the invention in reducing the height of waves in a body of water. The artificial reef structure experimental set-up is shown in Fig. 5.

[00041] Referring to the Figures, Fig. 1 shows an exemplary individual module 12 of the invention. The module 12 includes a receptacle 2 for receiving oyster shells. In this nonlimiting example, the receptacle 2 is a biodegradable bag 6 made out of sinamay fabric. In other examples, the receptacle 2 is fabricated of a material including but not limited to jute, leaf, coconut husk, cotton, manila hemp, sisal fiber, hay, straw, and dry stalks of wheat, rice, oats, barley, and rye. The receptacle 2 should be fabricated out of a biodegradable material that is still permeable to water. The module 12 also further includes a fastener 8. In this nonlimiting example, the fastener 8 is a tether made of sinamay fabric. Fig. 1 in particular shows the fastener 8 before it is tightened or tied to an adjacent module. However, in other examples, the fastener 8 is made of a material including but not limited to strings, rope, clips, or clamps. The receptacle 2 is then filled with oyster shells 4. In certain preferred examples, the oyster shells 4 may be hollow, whereas live whole oysters may be used in other examples.

[00042] Fig. 2 is a side view of the embodiment of Fig. 1 depicting the integration of a fastener 8 in the form of a tether, which is an extension of the receptacle 2. The fastener 8, like the receptacle 2, is made of sinamay fabric and biodegradable. Here, the receptacle 2 is a bag 6 made of the sinamay fabric arranged in a net-like formation to permit the bag 6 to be water- permeable. The bag 6 is filled with oyster shells 4. In this example, the fastener 8 is a tether that is shown in a tightened position, closing the top of the bag 6 around the oyster shells 4.

[00043] Fig. 3 is an aerial view of an embodiment of the receptacle 2, in the form of a bag

6, made from biodegradable material. In this view, the bag 6 is not filled with oyster shells (Figs. 1-2), and the fastener 8 in the form of a sinamay fabric tether can be seen coupled to the bag 6.

[00044] Fig. 4 shows oyster shells used for the experiment. The size of oyster shells 4 used ranged from 3 inches to 4 inches. However, in other examples, larger or smaller oyster shells 4 are used.

[00045] Fig. 5 shows the experimental setup using a plurality of modules 12 to create an artificial reef structure 10. The artificial reef structure 10 was tested in a wave tank 14 and was a two-dimensional reef with length of crest 0.85 m and length of base of 1.10 m. The height of the artificial reef structure 10 was 0.25 m. The width of the artificial reef structure was 0.716 m. In this nonlimiting example, the artificial reef structure 10 was created using a plurality of modules 12 stacked in a trapezoidal arrangement. The wave tank 14 used in the experiment had a length of 7.57 m, width of 0.78 m and height of 0.762 m.

[00046] Fig. 6 shows a schematic of the experimental setup depicted in Fig. 5. The wave tank 14 (Fig. 5) was equipped with a flap-type wave maker 16 on one end of the tank and a wave absorber 18 on the other end of the tank to both create and absorb waves used to simulate natural ocean waves. The artificial reef structure 10 was arranged toward the center of the wave tank 14 (Fig. 5). Four wave gauges (20A-D) were equally distributed throughout the length of the wave tank 14 (Fig. 5) to measure the height of each wave at each of the four locations. Two wave gauges (20A-B) were placed between the wave maker 16 and the artificial reef structure 10, and two wave gauges (20C-D) were placed between the artificial reef structure 10 and the wave absorber 18.

[00047] The wave transmission coefficient was calculated for three water levels: 28 cm, 29 cm, and 30 cm under different wave conditions. The wave transmission coefficient is defined as the ratio of transmitted wave height to incident wave height. Here the wave transmission coefficient is calculated using wave gage 20C by using the ratio of wave height with the submerged oyster reef to the wave height without the oyster reef. [1-2] The properties of the individual module 12 (FIG. 1) are shown in Table 1.

Table 1. Properties of Individual Oyster Module

[00048] The wave parameters used for the study are described in Table 2.

Table 2. Wave parameters.

[00049] Fig. 7 shows the plot of wave transmission coefficient for different wave steepness conditions for 30 cm water depth. The wave transmission coefficient showed a decreasing trend for increasing wave steepness [3-4], The waves with higher steepness broke effectively over the artificial reef structure 10 (Fig.5) as opposed to the waves with lower wave steepness. At 30 cm water depth, the artificial reef structure 10 (Fig.5) was able to reduce the wave height by approximately 20 to 30 %. For wave steepness Hi/L < 0.08, the wave height reduction is approximately 20 %. For low values of wave transmission coefficient (Hi/L < 0.08), the wave transmission coefficient is in the range of 0.8 to 0.9. [00050] Fig. 8 shows the wave transmission coefficient versus wave steepness for 29 cm water depth. The wave transmission coefficient for 29 cm water depth was lower compared to the 30 cm water depth, as the submergence depth over the artificial reef structure 10 (Fig.5) also reduced. As the submergence depth reduced, the wave breaking became intense and more energy was released through wave breaking. For a water depth of 29 cm, the wave height reduction was around 20 to 40%. For wave steepness, Hi/L > 0.08, the wave height reduction was around 40 %. The wave transmission coefficient for the 29 cm water depth was in the range of 0.6 to 0.8, whereas for 30 cm water depth, it was in the range of 0.7 to 0.9.

[00051] Fig. 9 shows the wave transmission coefficient versus wave steepness for a 28 cm water depth. The wave height reduction was maximum at 28 cm water depth. The wave height reduction was in the range of 30 to 50 %. As the submergence depth over the artificial reef structure 10 (Fig.5) reduced to 3 cm for 28 cm water depth, the wave breaking was intense, and more energy was released during the wave breaking. Therefore, the wave transmission coefficient was lowest for 28 cm water depth. For wave steepness, Hi/L > 0.08 the wave height reduction was around 50%.

[00052] The results from this experiment show that the incoming wave height was reduced significantly. The results also show that the lee side of the reef was protected effectively by the artificial reef.

[00053] As the water depth decreased from 30 cm to 28 cm, the submergence depth also decreased from 5 cm to 3 cm. The intensity of wave breaking and submergence depth have a direct dependence on the wave transmission coefficient. The intensity with which the wave broke increased as the submergence depth over the artificial reef structure 10 (Fig. 5) reduced. As the water depth or the submergence depth increased, the intensity of wave breaking was less, and the transmitted wave height was higher. As the transmitted wave height increased, the wave transmission coefficient also increased. Another parameter that influenced the wave transmission was the wave steepness. As the wave steepness increased, the wave transmission coefficient showed a decreasing trend. For waves with higher wave steepness, the wave breaking intensity was higher and more energy was released during wave breaking. Therefore, the wave transmission coefficient showed a decreasing trend with increasing wave steepness. [00054] As shown in Fig. 10, to check the rate of degradation of the sinamay biodegradable bags 6 (Fig. 1), two individual oyster modules 12 were kept inside a bucket 22 filled with tap water. Three buckets 22 filled with tap water were used to check the rate for degradation of the receptacles 2 (Fig. 1) for a duration of six months. Each of the three buckets 22 were filled with tap water, and two modules 12 were added each to the buckets 22. The buckets 22 were opened and checked during every 2 months to check the rate at which the receptacles 2 (Fig. 1) made of sinamay bags 6 (Fig. 1) were degrading.

[00055] Two individual modules 12 were placed inside the bucket 22 one on top of the other. The modules 12 were taken out from the bucket and thoroughly examined every 2 months. After two months, the first bucket 22 (Fig. 10) was opened to check the rate at which the Sinamay bag 6 enclosing the oyster shells are degrading. As shown in Fig. 11, Unit 1 is the individual module 12 which was kept in the bottom of the bucket 22 (Fig. 10) and Unit 2 is the individual module 12 which was placed on top. As shown by the circled area, some portions of the sinamay bag 6 of the Unit 1 module 12 which was located under the Unit 2 module 12 were broken. The weight of the Unit 2 module 12 was acting on the Unit 1 module 12, which exerted force on the sinamay bag 6 of the Unit 1 module 12.

[00056] Fig. 12 shows a magnified view of the circled area of the Unit 1 module 12 of Fig. 11. The module 12 is shown including a receptacle 2 in the form of a sinamay bag 6. The bag 6 is further filled with oyster shells 4 and further includes a fastener 8. Breakage is visible on the sinamay bag 6, indicating degradation had occurred after two months of placement in the water-filled bucket 22 (Fig. 10).

[00057] After 4 months, the second bucket 22 (Fig. 10) was opened to check the degradation of sinamay bags 6 (Fig. 1). Some of the portions of the bag 6 of the unit 2 module 12 (Fig. 11) which was placed on the top of the Unit 1 module 12 (Fig. 11) were also observed to be broken. The mesh portions of the sinamay bag 6 of the Unit 1 module 12 of the bucket 22 which were kept on bottom were broken and the oyster shells 4 (Fig. 12) fell into the bucket 22 upon removal.

[00058] Based on the study, it took approximately 4 months for a single sinamay bag 6 (Fig. 1) which contained oyster shells 4 (Fig. 12) to degrade under these conditions. As the sinamay bag 6 of the Unit 1 module 12 (Fig. 11) degraded after 4 months, resulting in the oyster shells 4 falling out of the bag 6, the third bucket 22 (Fig. 10) which was supposed to be opened after 6 months was discarded after 4 months. The degradation of the bag 6 encasing the individual reef module 12 can be controlled by increasing the number of receptacles 2 (Fig. 1) encasing an individual reef module 12.

[00059] Therefore, the artificial reef structure 10 (Fig. 5) made up of oyster shells 4 (Fig. 1) in biodegradable receptacles 2 (Fig. 1) protect a beach from incoming waves. In examples using live oysters, the oyster spat, otherwise known as oyster offspring, become attached to the existing oyster shells 4 and grow into living oysters. These oysters grow through the individual modules 12 (Fig. 1) and grow into a colony of oysters which increases the overall stability of the artificial reef structure 10 (Fig. 5). If the chances of oyster spat getting attached to the existing oyster shells 4 are scarce, then oyster spat can be provided artificially to the artificial reef structure 10.

[00060] Fig. 13 is a diagram of the various ocean zones. The diagram shows the various ocean zones which, from the land outward including the shore 36, run-up zone 32, swash zone 30, surf zone 28, breaker zone 26, and offshore zone 24. In order to blunt the force of waves 34, the artificial reef structure should be placed in a location inside or close to the surf zone 28. The surf zone 28 is the relatively narrow strip of a body of water that borders the shore 36, and which contains waves 34 that are breaking due to the shallow water depth. The surf zone 28 is located between the breaker zone 26 and swash zone 30. The breaker zone 26 is the zone in which the waves 34 break. The swash zone 30 forms the land-ocean boundary at the landward edge of the surf zone 28, where waves 34 runup the beach face of the shore 36.

[00061] Wave 34 transformation usually can start before the breaker zone 26. Deeper, the complexity in installation and cost of the submerged coastal structure begin to increase. The invention can be used as a coastal protection structure attached to the shore 36 and detached from the shore 36. Once the waves 34 are broken, secondary waves 38 are formed from the wave 34 breaking. If the coastal protection structure is placed farther away from the shore 36, the secondary waves 38 can undergo wave shoaling and increase the wave 34 height which will hit the shore 36 directly or break on the shore 36. This can cause beach erosion. This can be avoided by providing the reefs in series (along the direction of sea).

[00062] In conclusion, sustainable coastal protection structures are effective in protecting the shore from becoming eroded by waves without environmental pollution. Artificial reef structures made up of oyster shells in receptacles including but not limited to a biodegradable bag are effective in coastal protection without causing environmental pollution. Because the bags encasing the oyster shells are biodegradable, the artificial reef structure is environmentally friendly. The wave height attenuation by the artificial reef structure depends mainly on two parameters - submergence depth and wave steepness. When the submergence depth is kept constant, the wave transmission coefficient shows a decreasing trend with increasing wave steepness. As the wave steepness is increasing, the intensity of the wave breaking increases and the energy released during the wave breaking also increases. Therefore, the wave transmission coefficient for waves with higher steepness is lower. As the submergence depth of the artificial reef structure is reducing, the wave breaking over the reef becomes intense, and the transmitted wave height is less. The artificial reef structure considered in the above study reduced the wave height by around 50 %. Once the oyster reef is constructed, oyster spat are able to attach to the oyster shells and grow into living oysters. These living oysters will start to grow through the individual modules, increasing the overall stability of the artificial reef structure. If the chances of oyster spat becoming attached to the oyster shells naturally are scarce, then oyster spat can be provided artificially to the oyster reef. In the nonlimiting example discussed above, a single individual artificial reef module took approximately 4 months to degrade when kept inside a closed, water-filled bucket. The mesh portions of the sinamay bag were broken after 4 months. This is due to weight exerted by the individual unit module which is placed over the bottom unit module and degradation of portions of sinamay bag. However, it is to be understood that degradation may take more or less time depending on the surrounding environment and the biodegradable material used. The degradation of the bag encasing the individual reef module can be controlled by increasing the number of receptacles, or bags, encasing an individual reef module.

[00063] While the invention has been described in detail with reference to specific examples thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

REFERENCES

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[3] Dattatri, J., Raman, H., & Shankar, N. J. (1978). Performance characteristics of submerged breakwaters. Coastal Engineering Proceedings, (16), 130-130.

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