TECHNICAL FIELD

The disclosure relates to the field of artificial reefs, and more specifically to an artificial reef, an installation, methods, and a computer program for preventing or reducing coastal or river bank erosion.

BACKGROUND

In tropical, equatorial, and subtropical regions, mangroves are productive habitats that support many functions on which depend the local biodiversity (refuge, habitat, nursery, or spawning ground) and the surrounding populations through derived services (fisheries production, raw material, or coastal protection). Through their complex root systems, mangroves modify the physico-chemical conditions of the environment. For example, mangroves participate in the oxygenation of the substrate or in the creation of a low-energy environment by dissipating part of the incident wave energy and by slowing down the currents.

These species are known for their action on sediment dynamics. Indeed, they reduce sediment resuspension and promote sediment deposition. These different effects contribute to the stability of the substrate, an essential element for the sustainability of the mangrove. Thus, the physical interactions between mangroves and the environment create positive feedback loops that generate alternative stable states: the presence of mangroves catalyzes the installation of other mangroves and thus the progression of the mangrove, and vice versa in case of disturbance or degradation of these species.

With the intensification of the effects of climate change and human activities, mangroves play an essential role for local communities as they are natural coastal protections against erosion and marine submersion. However, mangroves are subject to an alarming regression. In this context, mangrove replanting programs have been implemented during the last decades. However, the survival rates of transplants are generally low for several reasons. These reasons include the use of inadequate planting methods, an insertion or reinsertion of inappropriate species or their establishment in hydro sedimentary contexts that have evolved and are no longer favorable to them.

Within this context, there is still a need for an improved solution for preventing or reducing coastal or river bank erosion.

SUMMARY

It is therefore provided an artificial reef for preventing or reducing coastal or river bank erosion. The artificial reef comprises means for anchoring the artificial reef to a water bottom. The artificial reef comprises elongated elements extending at least partially upward from the water bottom so as to form a porous barrier when the artificial reef is anchored to the water bottom. The artificial reef comprises a substantially plain base lying on the water bottom when the artificial reef is anchored to the water bottom.

The artificial reef may comprise one or more of the following: each elongated element has two ends, one of the two ends being attached to the base and another one of the two ends being free upward; the elongated elements have different lengths and/or apparent diameters; the elongated elements all have a same length and/or apparent diameter; the elongated elements are spaced apart from each other, the spacing between two adjacent elements being between 5 and 30 centimeters. the elongated elements have a length greater than 20 centimeters and/or lower than 100 centimeters; each elongated element is made of wood and/or 3D printed concrete; the base has a width greater than 0.5 meter and/or less than 3 meters; the base is made of concrete; the artificial reef is configured to anchor itself the water bottom by its own mass; the artificial reef has a mass greater than 30 kilograms; the base is flat-shaped and comprises a bottom surface, an upper surface, and an at least partially circular circumference between the bottom surface and the top surface, each elongated element passing through the upper surface of the base; the base comprises one or more cavities, each cavity opening onto the upper surface; one of the one or more cavities is configured for installation of an additional anchoring system; the base is totally plain; the upper surface and/or the circular circumference comprises a pattern; the upper surface comprises a circular pattern of bumps; the circular pattern of bumps comprises one or more concentric rows each composed of adjacent bumps; the circular circumference comprises irregularities; the base comprises one or more connecting means each configured for connecting the artificial reef with another artificial reef, the one or more connecting means being distributed over the circular circumference of the base; and/or each connecting means comprises at least one arm extending from the artificial reef, the arm being configured to attach with at least one other arm of the another artificial reef.

It is also provided an installation comprising one or more such artificial reefs. Each artificial reef is anchored to water bottom in a coastal, riverine or estuarine environment. The installation prevents or reduces coastal or river bank erosion of the coastal, riverine or estuarine environment.

It is also provided a computer-implemented method for simulating the prevention or reduction of coastal or river bank erosion of a real-world coastal, riverine or estuarine environment with such an installation. This method for simulating the prevention or reduction of coastal or river bank erosion may be referred to as "the simulation method." The simulation is performed on specifications of the installation and specifications of the real-world coastal, riverine or estuarine environment.

The simulation method may comprise setting the specifications of the installation. The setting may include selecting a type of artificial reef between a first type corresponding to the artificial reef and a second type of artificial reef. The selecting may depend on whether the real-world coastal, riverine or estuarine environment is or respectively is not a predominantly high current environment.

It is also provided a method for installing such an installation in a coastal, riverine or estuarine environment to prevent or reduce coastal or river bank erosion of the coastal, riverine or estuarine environment. This method for installing an installation may be referred to as "the installing method." The installing method comprises anchoring each artificial reef of the installation to water bottom in the coastal, riverine or estuarine environment.

The installing method may comprise one or more of the following: the coastal, riverine or estuarine environment is a predominantly high current environment; each artificial reef is anchored at a depth between 0 meter and 3 meters from the surface; the installation comprises at least two artificial reefs each comprising one or more connecting means, the method further comprising connecting the at least two artificial reefs to each other with the connecting means of the at least two artificial reefs; and/or the method further comprising, prior to the installing, performing the simulation method for simulating the prevention or reduction of coastal or river bank erosion of the coastal, riverine or estuarine environment induced by the installation.

It is also provided a computer program comprising instructions for performing the simulation method.

It is also provided a device comprising a data storage medium having recorded thereon the computer program. The device may form or serve as a non-transitory computer-readable medium, for example on a SaaS (Software as a service) or another server, or a cloud-based platform, or the like. The device may alternatively comprise a processor coupled to the data storage medium. The device may thus form a computer system in whole or in part (e.g., the device is a subsystem of the overall system). The system may further comprise a graphical user interface coupled to the processor.

BRIEF DESCRIPTION OF THE DRAWINGS

Non-limiting examples will now be described in reference to the accompanying drawings, where:

FIG.s 1 to 3 illustrate a first example of the artificial reef;

FIG.s 4 and 5 illustrate a second example of the artificial reef;

FIG.s 6 to 8 illustrate a third example of the artificial reef;

FIG 9 illustrates two artificial reefs connected together;

FIG.s 10 to 12 illustrate a fourth example of the artificial reef;

FIG.s 13 and 14 illustrate a fifth example of the artificial reef;

FIG. 15 illustrates a sixth example of the artificial reef; and

FIG. 16 shows an example of the system.

DETAILED DESCRIPTION

It is provided an artificial reef for preventing or reducing coastal or river bank erosion. The artificial reef comprises means for anchoring the artificial reef to a water bottom. The artificial reef comprises elongated elements extending at least partially upward from the water bottom so as to form a porous barrier when the artificial reef is anchored to the water bottom. The artificial reef comprises a substantially plain base lying on the water bottom when the artificial reef is anchored to the water bottom.

The artificial reef forms an improved solution for preventing or reducing coastal or river bank erosion.

Notably, the artificial reef allows imitating the role of the mangrove in the creation of a low-energy environment by dissipating a part of the incident wave and/or flow energy. Indeed, the porous barrier formed by the elongated elements allows slowing down the currents, in particular the currents near the water bottom, which allows preventing or reducing coastal or river bank erosion. The artificial reef thus reduces sediment resuspension and promotes sediment deposition, thus contributing to the stability of the substrate and restoring the erosion balance. The artificial reef slows down the current locally and allows the energy to be shifted upwards or on the sides (the current slows down at the bottom and accelerates at the surface or on the border of the structure), which preserves the sediment and favors the deposition of the sediment in the lowest water layer.

Moreover, the artificial reef allows stopping the regression of mangrove and/or helping its settlement. Indeed, the stability of the substrate and the reduction of hydrodynamics constraints induced by the artificial reef favors the installation of new mangroves and their growth, which in turn stabilizes the environment and thus favors the installation of other mangroves. The artificial reef therefore allows for the recolonization of the mangrove.

Moreover, by reproducing mangrove structural complexity, the artificial reef also supports similar ecological functionalities and ecosystem services. It supports nursery, habitat, substrate, spawning area or functions, hosts local life and helps species to settle and grow, supporting part of their lifecycle. It also supports production services, like fish or shell production. It also supports regulation services, as carbon capture and storage, by protecting soil carbon from remobilization through waves and flows, and helps mangrove settlement and growth.

Furthermore, the substantially plain base provides or at least participates to the anchoring, while the whole structure is simple to manufacture. The artificial reef allows high reproducibility and scalability, possible deployment with few resources, and it forms a resilient device in the medium term (e.g., five years). In particular, the structure of the artificial reef is well suited to a predominantly high current environment.

The artificial reef may be anchored to the water bottom by its own mass (also referred to as "weight" in the following). The mass of the artificial reef may be higher than 30 kilograms. For example, the means for anchoring the artificial reef to the water bottom may include the substantially plain base. The mass of the substantially plain base may constitute at least 75% of the whole mass of the artificial reef. By "substantially plain base", it is meant a base which comprises no through holes (i.e., a hole surrounded by material constitutive of the base), or a base which comprises one or more through holes defining altogether a total volume substantially lower than the total volume occupied by the material constitutive of the base, for example with a total volume of through holes lower than 25% of the total volume occupied by the material constitutive of the base. The base may be integrally formed.

The means for anchoring the artificial reef may comprise or consist of the base. The base may be made of a material with a density high enough to sink into water, e.g., such that the base remains in contact with the water bottom even in the presence of currents. For example, the base may be made of concrete material, from locally available concrete, possibly rudimentary, to technical ones as porous concrete, 3D printed or stamped concrete and/or concrete with inclusions like shell fragments. The use of concrete allows for an efficient local and sustainable manufacture of the artificial reef, as concrete may be poured into a substantially plain base shape, and the elongated elements may be added as the concrete is poured. The use of concrete also provides strength to the artificial reef.

Alternatively or additionally, the means for anchoring the artificial reef to the water bottom may comprise one or more connecting means each configured for connecting the artificial reef to another artificial reef. The connection means allow a network installation of several artificial reefs, which reinforces the anchoring and allows reducing even more the currents close to the water bottom. In addition, said other artificial reef may itself be anchored to the water bottom by other means.

Additionally or alternatively, the means for anchoring the artificial reef to the water bottom may comprise a structure which is anchored to the water bottom and/or connecting means each configured for connecting the artificial reef to such structure which is anchored to the water bottom. For example, the other structure may be a pillar which is stuck into the water bottom. The connecting means may comprise one or more holes passing through the base so as to stick the pillar therethrough.

Each elongated element may be attached to the base (e.g., may be connected to the base). For example, each elongated element may comprise a portion which is embedded in the base. For instance, the artificial reef may have been obtained by pouring concrete into a mold, and inserting a portion of the elongated elements thereinto before hardening of the concrete, such that after hardening the concrete fixedly embeds said portion of the elongated elements. Alternatively, one end of each elongated element may be fixed/anchored to the base, for example after hardening of the concrete. For example, the base may comprise, for each elongated element, a respective spike protruding upward out of the base and inserted into the end of the elongated element so as to attach the elongated element to the base. In yet another example, the base may comprise holes and the elongated elements may be press- fitted inside the holes.

Each elongated element extends at least partially upward from the water bottom when the artificial reef is anchored to the water bottom. The water bottom may be a sea bottom when the artificial reef is anchored in a coastal sea environment. Alternatively, the water bottom may be a lake bottom when the artificial reef is anchored in a coastal lake environment. Alternatively yet, the water bottom may be a river bottom (e.g., a river bank) when the artificial reef is anchored in a riverine or estuarine environment. Each elongated element may extend in a direction perpendicular to the water bottom, at least substantially. For example, the base may define a plane, and the plane of the base may be substantially parallel to the water bottom when the artificial reef is anchored to the water bottom. Each elongated element may be positioned relatively to the base such that the elongated element forms an acute angle with a direction normal to the plane of the base. The acute angle may be less than 45 degrees (e.g., less than 20 degrees). Each elongated element may be positioned vertically to the water bottom. In this case, the acute angle may be close to zero, for example less than 2 degrees.

The elongated elements may be positioned parallel to each other, at least substantially. Alternatively, at least one of the elongated elements may have a respective direction that differs from directions of other elongated elements. For example, the directions of the elongated elements may vary within a range of less than 45 degrees. The substantially plain base may comprise an upper surface. The upper surface may be substantially parallel to the water bottom when the artificial reef is anchored to the water bottom. The upper surface may be substantially convex and/or comprise a substantially convex portion on which the elongated elements may be arranged. For example, the elongated elements may be attached to the base on this portion. The portion of the upper surface may be a central portion of the upper surface. The artificial reef may have an occupancy rate of the elongated elements on the upper surface higher than 15%. The occupancy rate may be equal to the ratio of the area occupied by the elongated elements (i.e., the cross-sectional area of the elongated elements) to the total area of the upper surface. The artificial reef may have an occupancy rate in a range of 20-25%. Such an occupancy rate allows reducing the risk of breakage.

With reference to FIG.s 1 to 3, a first example of an artificial reef 100 is now discussed. FIG.s 2 and 3 are top and side views of the artificial reef 100 shown in FIG. 1.

The artificial reef 100 is shown as it would be anchored to a water bottom 130. The artificial reef 100 comprises elongated elements 110 extending at least partially upward from the water bottom 130 so as to form a porous barrier. The artificial reef 100 comprises a substantially plain base 120 lying on the water bottom 130. The base 120 is flat-shaped. The base 120 comprises a bottom surface 121, an upper surface 122, and an at least partially circular circumference 123 between the bottom surface 121 and the top surface 122. Each elongated element 110 passes through the upper surface 122 of the base 120. Each elongated element 110 has two ends 111, 112. One of the two ends 111 is embedded in the base and another one of the two ends 112 is free upward. Each elongated element 110 is positioned perpendicular to the upper surface 122 of the base 12O.The elongated elements 110 form a porous barrier. The elongated elements 110 with their free upward ends provide a bush-like structure to the artificial reef 100, making particularly suited to a predominantly high current environment. The elongated elements 110 are spaced apart from each other. The elongated elements 110 are distributed over the upper surface 122, e.g., substantially homogeneously distributed over the upper surface 122. The number of elongated elements 110 passing through the upper surface 122 per unit area (referred to as density) may be substantially constant. The density may be homogeneous over the upper surface 122. The spacing between the elongated elements may be less than a minimum distance. The spacing between two adjacent elements may be higher than 5 centimeters and/or lower than 30 centimeters. For example, the spacing may be higher than 20 centimeters when the apparent diameter of the elongated elements is higher than 100 millimeters. This spacing allows the passage of local fauna (e.g., fishes) while attenuating the currents. The artificial reef 100 has a bush-like structure. The upper surface 122 of the base 120 comprises a substantially convex portion to which the elongated elements 110 are attached, substantially everywhere on said portion.

The elongated elements 110 may be circular in cross-section (e.g., rod-shaped) or polygonal in cross-section (e.g., rectangular). In the example of the figure, the elongated elements 110 are all rod-shaped. In other examples, some (e.g., all) elongated elements 110 may be rectangular.

The elongated elements 110 may be made of wood. For example, the elongated elements 110 may be made of tree branches or machined wood pieces (e.g., trimmed to a size suitable for the artificial reef). Each elongated element 110 may have a generally circular cross section. The diameter of each elongated element may be in a range of values from 40 to 160 millimeters (e.g., from 40 to 140 millimeters). The elongated elements 110 may have homogeneous or heterogeneous diameters in this range of values.

The elongated elements 110 may have a length higher than 20 centimeters and/or lower than 100 centimeters. For example, the elongated elements 110 may have a length in a range of values from 20 to 100 centimeters. The elongated elements 110 may have homogeneous or heterogeneous lengths in this range of values. The artificial reef 100 may have a height between 35 and 120 centimeters (e.g., between 395 and 1185 millimeters).

The base 120 may have a width greater than 0.5 meter and/or less than

3 meters. For example, the base 120 may have a width between 0.8 and 2.8 meters (e.g., between 895 and 2685 millimeters). The number of elongated elements per unit area may be higher than 10 elongated elements per m ² and/or lower than 80 elongated elements per m ² (e.g., in a range of values from 10 to 80 elongated elements per m ² ). These ranges of values for the width of the base in relation to the numbers and dimensions of the elongated elements reduce the risk of non-stability of the artificial reef anchorage by its own mass.

The base comprises a number of (e.g., four) connecting means 140, 141, 142, 143 each configured for connecting the artificial reef 100 with another artificial reef. The connecting means 140, 141, 142, 143 are distributed over the circular circumference 123 of the base 120, and evenly spaced along the circular circumference 123 (with a quarter circle between each connecting means). The connecting means 140, 141, 142, 143 comprise a first type of connecting means 140, 142 arranged at respective ends of a first diameter segment of the circular circumference 123 and a second type of connecting means 141, 143, complementary to the first type, arranged at respective ends of a second diameter segment of the circular circumference 123, perpendicular to the first diameter segment. "Complementary" means that the connecting means of the first group and the connecting means of the second type are configured to connect together. For example, when a first artificial reef comprises connecting means of the first group and a second artificial reef comprises connecting means of the second group, the first artificial reef and the second artificial reef may be attached by connecting the first type connecting means of the first artificial reef and the second type connecting means of the second artificial reef.

The connecting means 140, 141, 142, 143 each comprise at least one arm 144, 145 extending from the artificial reef 100, and outwards from the artificial reef 100. The connecting means 140, 142 of the first type each comprise a respective arm 145. The connecting means 141, 143 of the second type each comprise two respective arms 144 spaced apart such that a respective arm of connecting means of the first type of another artificial reef may fit between the two arms 144. Each arm 144, 145 comprises a hole perpendicular to a tangent of the circular circumference 123. The holes are aligned such that, when a first artificial reef comprises connecting means of the first group and a second artificial reef comprises connecting means of the second group, and when the respective arm of the connecting means of the first type fits between the two arms of the connecting means of the second type, the holes in each of the arms are co-axial and a rod may be placed inside the holes to hold the first reef attached to the second reef (such as the rod 146 illustrated in FIG. 2).

The base comprises four cavities 150. The cavities 150 are substantially circular in shape. Each cavity 150 opens onto the upper surface 122 of the base 120. Each cavity 150 may define a volume within an upper portion of the base and not extend to a lower portion of the base (i.e., be near the upper surface 122 only). Alternatively, each cavity 150 may define a volume passing entirely through the base (i.e., be a through hole). In that case, the cavities 150 are traversing the base. The four cavities 150 define altogether a total volume substantially lower than the total volume occupied by the material constitutive of the base. The opening of each cavity onto the upper surface 122 represents a respective substantially circular portion of the upper surface 122. The respective substantially circular portions of the four cavities 150 altogether represent less than half of the upper surface 122 (e.g., less than 25% or 20% of the upper surface 122). The remaining portion of the upper surface 122 (i.e., the upper surface without the respective substantially circular portions of the four cavities 150) may represent more than 80% of the upper surface 122. The elongated elements 110 may pass through the upper surface at said remaining portion. In other examples, the base may comprise another number of cavities, such as one to three cavities or more than four cavities. One of the cavities 150 is configured for installation of an additional anchoring system. For example, the additional anchoring system may itself be anchored to the water bottom and may be inserted within the cavity for holding the base of the artificial reef. This optional system may be a pious or an anchor (e.g. a screw anchor) guaranteeing the stability of the artificial reef 100 under constraining hydrodynamics. The cavities 150 may also be used as a habitat for marine wildlife. The cavities 150 allow lightening the artificial reef 100 and to facilitate its handling. The cavities 150 also allow limiting the surface occupied by an opaque system to the transfers between soil and water (i.e., the base). The cavities 150 also allow providing, in the center of the artificial reef 100, access areas to the sediment allowing germination and/or the installation of burrowing organisms.

The artificial reef 100 allows preventing coastal or river bank erosion and reproducing the mangrove when installed in a coastal, riverine or estuarine environment. The term "erosion" refers to the erosion of coasts, banks or other boundaries between land and water of the coastal sea or coastal lake or riverine environment. For example, the method may comprise installing the artificial reefs in one or more coasts of a sea or lake. In that case, the erosion may be the coastal erosion of the one or more coasts on which the artificial reefs are installed. Alternatively, the method may comprise installing the artificial reefs in one or more banks of a river. In that case, the erosion may be a river bank erosion of the one or more banks on which the artificial reefs are installed. The erosion may be a coastal erosion when the artificial reef 100 is anchored to a sea bottom or an erosion of river banks when the artificial reef 100 is anchored to a river bottom (e.g., in the river banks). Indeed, the bush-like structure reduces currents, promotes sedimentation and may be used by marine fauna. The artificial reef is thus particularly adapted for a predominately high current environment and allows reproducing mangrove ecological and hydrodynamics functionalities where mangrove cannot easily settle or being restored.

FIG.s 4 and 5 illustrate a second example of artificial reef 200. The second example of artificial reef 200 differs from the first example of artificial reef 100 in that the elongated elements 210 have different diameters (or different apparent diameters). The elongated elements 210 may be wooden branches, and wooden branches of different diameters are used in this second example, which contributes to the simplicity of manufacture of the artificial reef 200. The heterogeneity of the diameters and lengths of the elongated elements 210 also contributes to reinforce the biomimicry with the locally representative mangroves, and thus to reinforce the coherence of the artificial reef 200 with the local context, and thus to improve the answer to the challenges of ecological and technical performance. Each elongated element 220 passes through the upper surface 222 of the base 220. The elongated elements 210 are spaced apart from each other and homogenously distributed over the upper surface 222, thereby providing a homogenous porous barrier of a bush-like structure enabled to attenuate the currents.

FIG.s 6 to 8 illustrate a third example of artificial reef 300. FIG.s 7 and 8 are top and side views of the artificial reef 300 shown in FIG. 6. The third example of artificial reef 300 comprises a substantially plain base 320 and elongated elements 310 embedded in the base 320. In this example, the elongated elements 310 have different diameters. The third example of artificial reef 300 differs from the first and second examples of artificial reefs 100, 200 in that the base 320 is totally plain (i.e., without cavities), thus particularly dense and thereby achieving a high anchoring capability, and particularly easy to manufacture (with a simplified mold). The third example of artificial reef 300 also differs from the first and second examples of artificial reefs 100, 200 in that the elongated elements 310 have different lengths. The heterogeneity of root lengths allows us to better reproduce the complexity of certain mangrove environments, particularly in terms of habitat and nursery. The length of each elongated element may be between 30 and 110 centimeters (e.g., between 340 and 1035 millimeters). The artificial reef may have a height between 40 and 140 centimeters (e.g., between 440 and 1320 millimeters). The elongated elements 210 may be wooden branches, and wooden branches of different diameters and lengths are used in this third example. The third example of artificial reef 300 is therefore particularly simple to manufacture.

FIG. 9 illustrate two artificial reefs 350, 350' connected together. The two artificial reefs 350, 350' differ from the first example of artificial reef 100 in that they each comprise lifting points 351 on the upper surface of the base. Each lifting point 351 consists of a loop-shaped metal rod extending from the upper surface, thus forming a handle. The lifting points 351 facilitate transportation and placement of the artificial reef 350, 350' at the water bottom. Each of the two artificial reefs 350, 350' comprises connecting means of the first type and connecting means of the second type. The connecting means 352 of the first type of the artificial reef 350 is connected to the connecting means 353 of the second type of the artificial reef 350'. The respective arm of the connecting means 352 of the first type of the artificial reef 350 fits between the two arms of the connecting means 353 of the second type of the artificial reef 350'. The connection of the two artificial reefs 350, 350' improves the anchoring of the two artificial reefs 350, 350'.

FIG.s 10 to 12 illustrate a fourth example of artificial reef 400. FIG.s 11 and 12 are top and side views of the artificial reef 400 shown in FIG. 10. The fourth example of artificial reef 400 comprises a substantially plain base 420 and elongated elements 410 embedded in the base 420. The fourth example of artificial reef 400 differs from the previous examples in that the upper surface and the circular circumference of the base 420 comprise a relief pattern, e.g., comprising one or more bumps. In particular, the upper surface comprises a circular pattern of bumps which comprises two concentric rows 423 each composed of adjacent bumps 424. In this example, the circular pattern comprises two concentric rows 423, but in other examples, the circular pattern of bumps may comprise another number of concentric rows, such as one concentric row or more than two concentric rows, or yet a non-circular pattern of bumps. The circular pattern of the bumps imitates a fish nest (e.g., the fish nest of the Torquigener sp.), and increases the ability of the artificial reef to redirect flows away from the center of the structure, since this pattern avoids the dispersion of eggs in case of mating. Indeed, the speed of water is less important in the center of the geometrical shape of the circular pattern. Additionally, the circular circumference comprises irregularities including several cavities 425. The circular pattern and the irregularities create roughness which increases friction and therefore the performance of the artificial reef in dissipating currents. Moreover, the circular pattern and the irregularities promote micro-complexity and thus promote ecological performance through the fixation of fixed fauna and the creation of habitat for small organisms.

FIG 13 illustrates a fifth example of artificial reef 500 which differs from the first example 100 in that the circular circumference comprises irregularities including vertical notches 525. The vertical notches 525 increases the performance of the artificial reef in dissipating currents and promote ecological performance. The fifth example of artificial reef 500 also differs from the first example 100 in that the connecting means 541 each comprise one arm consisting of a loop-shaped metal rod. The loop-shaped metal rod is configured to attach with at least one other arm of the another artificial reef, as illustrated in FIG 14. An artificial reef 501 comprising loopshaped metal rods is attached with another artificial reef 501' similar to the artificial reef 501. One of the loop-shaped metal rods of the artificial reef 501 is attached to another one of the loop-shaped metal rods of the artificial reef 501' based on a rod 530 inserted inside each of the two loop-shaped metal rods. The attachment of the artificial reef 501 with the artificial reef 501' is performed by inserting the rod 530 inside each of the two loop-shaped metal rods.

FIG. 15 illustrates a sixth example of artificial reef 600 which differs from the fifth example 500 in that the elongated elements 610 are made of concrete (e.g., 3D printed concrete). The circumference of the base 620 is substantially circular in shape with an undulating form and comprises irregularities including cavities 625. The upper surface of the base 620 also comprises cavities 626 and, for each cavity 626, a respective elongated element is positioned on the upper surface at the cavity 626.

It is also provided an installation comprising one or more artificial reefs. Each artificial reef is anchored to water bottom in a coastal, riverine or estuarine environment. The coastal environment may be a coastal sea environment or a coastal lake environment. When the installation comprises several artificial reefs, the artificial reefs may be positioned relative to each other to form a pattern on the water bottom. The location of the artificial reefs and/or the design of the pattern may be such that the installation achieves a certain performance in terms of preventing or reducing coastal or river bank erosion, and creating appropriate conditions for sediment stabilization and/or mangrove settlement and growth. When the artificial reefs comprise connecting means, the artificial reefs may be positioned relative to each other based on these connecting means. The artificial reefs may be positioned relative to each other in line or according to a checkerboard pattern.

It is also provided a computer-implemented method for simulating the prevention or reduction of coastal or river bank erosion of a real-world coastal, riverine or estuarine environment with the installation (referred to as "the simulation method"). The simulation is performed based on specifications of the installation and specifications of the real-world coastal, riverine or estuarine environment. The specifications of the installation may comprise the number of artificial reef of the installation, the respective position of each artificial reef (e.g., the pattern formed) or specifications of each artificial reef (e.g., the width or height of the artificial reef or the number/density of elongated elements).The specifications of the real-world coastal, riverine or estuarine environment may comprise quantities distributed on a surface representing the real-world coastal, riverine or estuarine environment (e.g., water height, soil type and/or gradient values or current values).

The simulation method may comprise setting the specifications of the installation, including selecting a type of artificial reef between a first type of artificial reef and a second type of artificial reef, depending on whether the real-world coastal, riverine or estuarine environment is or respectively is not a predominantly high current environment. The first type of artificial reef may correspond to the artificial reef as previously discussed. The second type of artificial reef may correspond to another type of artificial reef, for example an artificial reef comprising horizontal structural elements maintaining the elongated elements and wherein the porous barrier formed by the elongated elements presents a substantially constant density vertically. For example, the simulation method may comprise selecting the first type when the real-world coastal, riverine or estuarine environment is a predominantly high current environment and the second type otherwise.

The simulation method is computer-implemented. This means that steps (or substantially all the steps) of the simulation method are executed by at least one computer, or any system alike. Thus, steps of the simulation method are performed by the computer, possibly fully automatically, or, semi-automatically. In examples, the triggering of at least some of the steps of the simulation method may be performed through user-computer interaction. The level of user-computer interaction required may depend on the level of automatism foreseen and put in balance with the need to implement user's wishes. In examples, this level may be user-defined and/or pre-defined.

A typical example of computer-implementation of a simulation method is to perform the simulation method with a system adapted for this purpose. The system may comprise a processor coupled to a memory and a graphical user interface (GUI), the memory having recorded thereon a computer program comprising instructions for performing the simulation method. The memory may also store a database. The memory is any hardware adapted for such storage, possibly comprising several physical distinct parts (e.g., one for the program, and possibly one for the database).

FIG. 16 shows an example of the system, wherein the system is a client computer system, e.g., a workstation of a user.

The client computer of the example comprises a central processing unit (CPU) 1010 connected to an internal communication BUS 1000, a random-access memory (RAM) 1070 also connected to the BUS. The client computer is further provided with a graphical processing unit (GPU) 1110 which is associated with a video random access memory 1100 connected to the BUS. Video RAM 1100 is also known in the art as frame buffer. A mass storage device controller 1020 manages accesses to a mass memory device, such as hard drive 1030. Mass memory devices suitable for tangibly embodying computer program instructions and data include all forms of nonvolatile memory, including by way of example semiconductor memory devices, such as EPROM, EEPROM, and flash memory devices; magnetic disks such as internal hard disks and removable disks; magneto-optical disks. Any of the foregoing may be supplemented by, or incorporated in, specially designed ASICs (application-specific integrated circuits). A network adapter 1050 manages accesses to a network 1060. The client computer may also include a haptic device 1090 such as cursor control device, a keyboard, or the like. A cursor control device is used in the client computer to permit the user to selectively position a cursor at any desired location on display 1080. In addition, the cursor control device allows the user to select various commands, and input control signals. The cursor control device includes a number of signal generation devices for input control signals to system. Typically, a cursor control device may be a mouse, the button of the mouse being used to generate the signals. Alternatively or additionally, the client computer system may comprise a sensitive pad, and/or a sensitive screen.

The computer program may comprise instructions executable by a computer, the instructions comprising means for causing the above system to perform the simulation method. The program may be recordable on any data storage medium, including the memory of the system. The program may for example be implemented in digital electronic circuitry, or in computer hardware, firmware, software, or in combinations of them. The program may be implemented as an apparatus, for example a product tangibly embodied in a machine-readable storage device for execution by a programmable processor. The steps of the simulation method may be performed by a programmable processor executing a program of instructions to perform functions of the simulation method by operating on input data and generating output. The processor may thus be programmable and coupled to receive data and instructions from, and to transmit data and instructions to, a data storage system, at least one input device, and at least one output device. The application program may be implemented in a high-level procedural or object-oriented programming language, or in assembly or machine language if desired. In any case, the language may be a compiled or interpreted language. The program may be a full installation program or an update program. Application of the program on the system results in any case in instructions for performing the simulation method. The computer program may alternatively be stored and executed on a server of a cloud computing environment, the server being in communication across a network with one or more clients. In such a case a processing unit executes the instructions comprised by the program, thereby causing the simulation method to be performed on the cloud computing environment.

It is also provided a method for installing the installation in a coastal, riverine or estuarine environment to prevent or reduce coastal or river bank erosion of the coastal, riverine or estuarine environment or of the river banks (referred to as the installing method). The environment may be a typical mangrove environment, e.g., a littoral or a river bank in which the mangrove is disappearing, has disappeared or could settle. The installation may prevent this disappearance of the mangrove or help its recovery. The installing method comprises anchoring each artificial reef of the installation to water bottom in the coastal, riverine or estuarine environment. For example, the installing method may comprise positioning the one or more artificial reefs relative to each other to form the pattern on the water bottom (e.g., in line or according to a checkerboard pattern, following a regular or discontinuous layout). The coastal, riverine or estuarine environment may be a predominantly high current environment. For example, the average current over one year may be higher than 0.3 m.s ¹ , and the maximum current velocity may reach several m.s ^-1 (e.g., 3 m.s ¹ ). Flow may be the dominating hydrodynamics constraint over waves. Each artificial reef may be anchored at a depth from 0 to 3 meters, according to local conditions (flow, tide, slope or substrate). The distance from the artificial reefs to the sea shore or river bank may depend on the slope, flow velocity and performance objectives. The artificial reef may be emerging substantially most of the time (e.g. the artificial reef may be partially emerged or fully emerging in low tide conditions).

When the installation comprises at least two artificial reefs, the method may further comprise connecting the at least two artificial reefs to each other with the connecting means of the at least two artificial reefs.

The installing method may further comprise, prior to the installing, performing the simulation method for simulating the prevention or reduction of coastal or river bank erosion of the coastal, riverine or estuarine environment induced by the installation. The performing of the simulation method may set the specifications of the installation to be installed, including selecting a type of artificial reef between the first type of artificial reef and the second type of artificial reef for the installation. The selection may depend on whether the real-world coastal, riverine or estuarine environment is or respectively is not a predominantly high current environment. The performing of the simulation method may also set other specifications of the installation. For example, the performing of the simulation method may set the number of artificial reefs of the installation, the respective position of each artificial reef and/or the specifications of each artificial reef.