Biologically symbiotic revetments and their construction methods

Abstract

This invention provides a bio-friendly seawall and a method for constructing it that effectively utilizes areas where the rate of subsidence over time is significant relative to the sea surface, while suppressing changes in the habitat of organisms over time. [Solution] A dock section 3 is formed at the seashore of the sinking region 2, the dock section 3 and the sea are separated by a partition wall 4, the upper end of the partition wall 4 is set higher than the sea surface, a water reservoir 5 is placed floating in the dock section 3 where seawater W is stored, seawater W is supplied from the water reservoir 5 by a seawater supply unit 9 to the dock section 3 and stored in the water reservoir 5 to a predetermined depth h, and seawater W is discharged from the dock section 3 into the sea and stored in the dock section 3 to a predetermined depth H, thereby maintaining the upper end of the partition wall 4, which sinks over time together with the sinking region 2, at a position higher than the sea surface.

Description

Technical Field

[0001] The present invention relates to a symbiotic revetment for organisms and a construction method thereof, and more particularly to a symbiotic revetment for organisms and a construction method thereof that can suppress temporal changes in the habitat environment for organisms while effectively utilizing a region having a large degree of temporal settlement relative to the sea level. Background Art

[0002] In reclaimed lands facing the sea and the like, there exist locations where temporal settlement progresses faster than in general ground. That is, a location where the amount of temporal ground subsidence and / or sea level rise is large becomes a region having a large degree of temporal settlement relative to the sea level. Such a region will eventually be submerged, so it is not suitable for constructing structures. Countermeasures such as pre-embankment (filling) are sometimes taken for such regions in anticipation of the degree of temporal settlement. Although embankment can extend the period until submergence, there is a problem that it will eventually be submerged. Once submerged, the region is left as it is, so ingenuity is required to effectively utilize the region.

[0003] By the way, various symbiotic revetments for organisms have been proposed to facilitate the inhabitation of diverse organisms in regions facing the sea (see, for example, Patent Documents 1, 2 and 3). In these proposed symbiotic revetments for organisms, organisms suitable for each flat site easily inhabit stepped flat sites installed along the seashore. Prior Art Documents Patent Documents

[0004] Patent Document 1 Japanese Unexamined Patent Publication No. 2010-65473 Patent Document 2 Japanese Unexamined Patent Publication No. 2004-308157 Patent Document 3 Japanese Unexamined Patent Publication No. 2004-68272 Summary of the Invention Problems to be Solved by the Invention

[0005] While constructing a bio-friendly seawall would lead to effective utilization of the area, areas that experience significant subsidence relative to the sea surface over time will eventually be submerged, as mentioned above. Therefore, even if a bio-friendly seawall with distinctive underwater environments, such as stepped flat areas, is constructed, there is a problem that the habitat of organisms will change as subsidence progresses over time. For example, as the water depth of flat areas increases, sunlight becomes less likely to reach them, making it difficult for photosynthetic organisms to survive. Thus, the object of the present invention is to provide a bio-friendly seawall and a method for constructing it that can effectively utilize areas that experience significant subsidence relative to the sea surface over time while suppressing changes in the habitat of organisms over time. [Means for solving the problem]

[0006] To achieve the above objective, the present invention provides a biologically symbiotic seawall constructed in a subsidence region where the rate of subsidence over time relative to the sea surface is greater than a predetermined value, comprising: a dock formed at the seashore of the subsidence region; a partition wall separating the dock from the sea; a water reservoir positioned floating on the seawater stored in the dock; and a seawater supply unit for supplying seawater, wherein the upper end of the partition wall is set higher than the sea surface, and seawater is supplied to the water reservoir by the seawater supply unit, causing seawater to flow out of the water reservoir into the dock, resulting in the storage of seawater to a predetermined depth in the water reservoir, and seawater to flow out of the dock into the sea, resulting in the storage of seawater to a predetermined depth in the dock.

[0007] The present invention relates to a method for constructing a biologically symbiotic seawall in a subsidence region where the rate of subsidence over time relative to the sea surface is greater than a predetermined value, characterized in that a dock section is formed at the seashore of the subsidence region, the dock section is separated from the sea by a partition wall, seawater is supplied to the dock section to store the seawater, a water reservoir is placed floating in the seawater stored in the dock section, seawater is supplied to the water reservoir, seawater is discharged from the water reservoir to the dock section to store seawater to a predetermined depth in the water reservoir, seawater is discharged from the dock section into the sea to store seawater to a predetermined depth in the dock section, the upper end of the partition wall is set higher than the sea surface, and the upper end of the partition wall, which subsides as the subsidence of the subsidence region over time, is maintained at a position higher than the sea surface. [Effects of the Invention]

[0008] According to the present invention, seawater is supplied to the reservoir by the seawater supply unit, and the seawater flows out to the dock, storing seawater to a predetermined depth. The reservoir is installed floating on the seawater stored in the dock. Therefore, the reservoir can cultivate desired organisms suitable for its predetermined depth without being affected by the time-dependent sinking of the sinking region relative to the sea surface. In the dock, where seawater flows out from the reservoir and into the sea, storing seawater to a predetermined depth, organisms suitable for this underwater environment can be cultivated. Since the upper end of the partition wall is set higher than the sea surface, it is possible to maintain the underwater environment in the dock even if the sinking region sinks relative to the sea surface over time. Furthermore, the organisms cultivated in the dock and the reservoir are at reduced risk of having their growth inhibited by organisms (natural enemies) inhabiting the sea area facing this symbiotic seawall. Therefore, it is advantageous to effectively utilize areas where the rate of subsidence over time is large relative to the sea surface, while suppressing the time-dependent changes in the habitat of organisms caused by this rate of subsidence. [Brief explanation of the drawing]

[0009] [Figure 1]This is an explanatory diagram illustrating an embodiment of a bio-symbiotic revetment in a plan view. [Figure 2] This is a cross-sectional view AA in Figure 1. [Figure 3] Figure 2 is an explanatory diagram illustrating the outflow section in a front view. [Figure 4] This is an explanatory diagram illustrating the water storage area in Figure 2 in an enlarged cross-sectional view. [Figure 5] Figure 4 is an explanatory diagram illustrating the outflow section for the water storage area in a plan view. [Figure 6] This is an explanatory diagram showing a modified example of the water storage section in Figure 4. [Figure 7] This is an explanatory diagram illustrating the state in which organisms are being cultivated in the reservoir section shown in Figure 4. [Figure 8] This is an explanatory diagram showing a modified example of the dog section in Figure 2. [Figure 9] This is an explanatory diagram illustrating the initial state of the subsidence region shown in Figure 1. [Figure 10] Figure 9 is an explanatory diagram illustrating the subsidence region in a side view. [Figure 11] Figure 9 is an explanatory diagram illustrating, in cross-sectional view, the process of constructing a bio-symbiotic revetment in the subsidence area. [Figure 12] Figure 2 is an explanatory diagram illustrating the state of a biologically symbiotic seawall that has subsided over time. [Figure 13] This is an explanatory diagram showing a modified example of the partition wall in Figure 2. [Figure 14] Figure 13 is an explanatory diagram illustrating the state in which the biological symbiotic revetment has subsided over time, resulting in the addition of a new partition wall. [Figure 15] This is an explanatory diagram illustrating another embodiment of a bio-symbiotic revetment in a plan view. [Modes for carrying out the invention]

[0010] The biologically symbiotic revetment and its construction method according to the present invention will be described below based on the embodiments shown in the figures.

[0011] The embodiment of the aquatic organism symbiosis revetment 1 (hereinafter referred to as revetment 1) illustrated in Figures 1 to 3 is constructed on a reclaimed land facing the sea, and this reclaimed land has a larger amount of ground subsidence than general ground. That is, the revetment 1 is constructed in a subsidence area 2 where the time-dependent subsidence relative to the sea surface is greater than a predetermined value X. Such a subsidence area 2 is not limited to an area with a large amount of time-dependent ground subsidence, but may be an area with a large amount of time-dependent sea level rise, or an area where the sum of the time-dependent ground subsidence amount and the time-dependent sea level rise amount is large.

[0012] The predetermined value X that defines the subsidence area 2 is the subsidence state of the subsidence area 2 relative to the annual average water level (WL) of the sea area faced by the subsidence area 2, and is, for example, 10 cm / year or 20 cm / year. The average water level (WL) is a water level calculated by averaging the syzygy average low water level (LWL) and the syzygy average high water level (HWL). As the predetermined value X, for example, an actual value grasped at the time of constructing the revetment 1, or a predicted value for the next 10 years estimated from this actual value is adopted. Therefore, based on the sea surface, the subsidence area 2 will subside by about 1 m to 2 m or more than 2 m after 10 years, and will subside by a similar amount further after 20 years.

[0013] The revetment 1 includes a dock portion 3 formed at the seaside of the subsidence area 2, a partition wall 4 that blocks the dock portion 3 from the sea, water storage portions 5 (5a, 5b) arranged in a state of floating on seawater W stored in the dock portion 3, and a seawater supply portion 9. The seawater supply portion 9 supplies seawater W to the water storage portions 5 and the dock portion 3. Since the revetment 1 is constructed at the corner of the subsidence area 2, the partition wall 4 is L-shaped in plan view, and the dock portion 3 is quadrangular. Arrows X, Y, and Z in the figures respectively indicate the longitudinal direction, the width direction, and the height direction of the subsidence area 2, which are directions orthogonal to each other. In Figures 1, 9, 10, and 15, the sea (sea area) is indicated by broken lines.

[0014] The dock section 3 is enclosed and partitioned by a wall formed by the ground of the subsidence area 2 and a partition wall 4. The shape of the dock section 3 in plan view is not limited to a rectangle, but can be any desired shape. Seawater W is stored in the dock section 3 at a predetermined depth H. This predetermined depth H is, for example, about 3m to 10m. In this embodiment, the bottom surface 3a of the dock section 3 is flat and at the same height level throughout, but the height position of the bottom surface 3a can be made to be at multiple different levels.

[0015] Installation objects R are installed inside the dock section 3. In this embodiment, numerous installation objects R are stacked on the bottom surface 3a of the dock section 3, and installation objects R protrude from the surface of the partition wall 4. As installation objects R, stones or blocks of any desired shape can be used. By installing installation objects R on the bottom surface 3a, desired undulations and gaps can be formed. The installation objects R installed on the surface of the partition wall 4 should be placed at a water depth where sufficient sunlight can reach them. The presence of installation objects R makes it easier for algae and other organisms to live, and consequently, the underwater environment becomes more suitable for plankton that inhabit algae, fish and shellfish eggs and larvae, and small fish.

[0016] The upper end of the partition wall 4 is always above sea level, except in abnormal situations such as typhoons. Therefore, the partition wall 4 effectively prevents seawater from this area from flowing directly into the dock section 3. The upper end of this partition wall 4 is above the water level of the seawater stored in the dock section 3. In addition, the water level of the seawater W stored in the dock section 3 is above sea level.

[0017] As illustrated in Figure 3, an outflow section 4a is formed in this partition wall 4. Seawater W stored in the dock section 3 flows out into the sea through the outflow section 4a. In this embodiment, a notch is formed at a position midway along the width direction (Y direction) of the partition wall 4, extending along the entire length in the vertical direction (Z direction), and this notch functions as the outflow section 4a. Multiple water level regulating bodies 4b are stacked and installed to block the outflow section 4a. The water level regulating bodies 4b are not limited to impermeable walls (concrete, iron, etc.), but can also be permeable walls (stone, blocks, pipes), or a combination of these.

[0018] In this embodiment, an impermeable water level regulator 4b is employed, and if the water level of the seawater W stored in the dock section 3 is higher than the sea surface, the seawater W stored in the dock section 3 will flow out into the sea over the water level regulator 4b located in the outlet section 4a. Therefore, the predetermined depth H (upper limit) of the seawater W stored in the dock section 3 is determined according to the number (height) of stacked water level regulators 4b. That is, by changing the number (height) of stacked water level regulators 4b, the height at which the seawater W flows out of the outlet section 4a becomes variable, and the seawater W stored in the dock section 3 can be set to a desired predetermined depth H. It is also possible to set the water level of the seawater W stored in the dock section 3 to a position lower than the sea surface, but if the water level of the seawater W stored in the dock section 3 is higher than the sea surface, the seawater W stored in the dock section 3 can be flowed out into the sea without any special power.

[0019] The outflow section 4a can be formed at any desired position relative to the width direction of the partition wall 4, and can be formed in multiple locations, not just one. Furthermore, the lower end position of the outflow section 4a can be set to any desired position.

[0020] To vary the height at which seawater W flows out of the outflow section 4a, various structures can be employed, not limited to the structure exemplified in this embodiment. For example, a weir can be provided that protrudes upward from the lower end of the outflow section 4a, and the amount of upward protrusion of this weir can be varied. Since the seawater W flows over this weir, the predetermined depth H of the seawater W stored in the dock section 3 is determined according to the amount of upward protrusion of this weir. Alternatively, multiple through-holes can be formed at intervals in the height direction of the partition wall 4, and plugs can be provided to close each through-hole. By removing the plugs that are blocking the through-holes, seawater W flows out from those through-holes, and the predetermined depth h of the seawater W stored in the dock section 3 is determined according to the height position of the through-hole from which the plugs are removed.

[0021] Furthermore, the height at which the seawater W flows out of the outlet section 4a can be kept constant. Alternatively, the partition wall 4 can be constructed without an outlet section 4a. In this structure, the seawater W stored in the dock section 3 flows over the partition wall 4, so the predetermined depth H of the seawater W stored in the dock section 3 is determined according to the height of the partition wall 4.

[0022] The reservoir section 5 is used to cultivate desired organisms, such as seagrass. The reservoir section 5 is moored to the surrounding ground of the dock section 3, for example, by mooring ropes. The reservoir section 5 is not limited to two; there may be one or three or more. The plan view shape of the reservoir section 5 is not limited to a rectangle; any shape can be adopted.

[0023] As illustrated in Figure 4, each reservoir 5 is formed by erecting a peripheral wall 7 around the periphery of the bottom surface 6, and stores seawater W at a predetermined depth h. The upper end of the peripheral wall 7 of each reservoir 5 is higher than the water level of the seawater W stored in the reservoir 5. Soil S, such as sand, is laid on the bottom surface 6 of each reservoir 5.

[0024] As illustrated in Figure 5, an outlet 7a for the water storage section is formed in the peripheral wall 7 of each water storage section 5. The seawater W stored in each water storage section 5 flows out to the dock section 3 through this outlet 7a. In this embodiment, a notch is formed at a position midway along the width direction (Y direction) of the peripheral wall 7, extending along the entire length in the vertical direction (Z direction), and this notch functions as the outlet 7a. Multiple water level regulating bodies 8 are stacked and installed to block the outlet 7a. The water level regulating bodies 8 are not limited to impermeable walls (concrete, iron, etc.), but can also be permeable walls (stone, blocks, pipes), or a combination of these.

[0025] In this embodiment, an impermeable water level regulator 8 is employed, and the seawater W stored in each water reservoir 5 flows out over the water level regulator 8 located in the outlet 7a. Therefore, the predetermined depth h (upper limit) of the seawater W stored in each water reservoir 5 is determined according to the number (height) of stacked water level regulators 8. That is, by changing the number (height) of stacked water level regulators 8, the height at which the seawater W flows out of the outlet 7a becomes variable, and the seawater W stored in the water reservoir 5 can be set to a desired predetermined depth h.

[0026] The outflow section 7a can be formed at any desired position relative to the width direction of the peripheral wall 7, and can be formed in multiple locations, not just one. Furthermore, the lower end position of the outflow section 7a is not limited to being at the same position as the bottom surface 6, as in this embodiment, but can be, for example, at approximately the same height as the soil S laid on the bottom surface 6.

[0027] To vary the height at which seawater W flows out of the outflow section 7a, various structures can be employed, not limited to the structure exemplified in this embodiment. For example, a weir can be provided that protrudes upward from the lower end of the outflow section 7a, and the amount of upward protrusion of this weir can be varied. Since the seawater W flows over this weir, the predetermined depth h of the seawater W stored in each water storage section 5 is determined according to the amount of upward protrusion of this weir. Alternatively, multiple through-holes can be formed at intervals in the height direction of the peripheral wall 7, and plugs can be provided to close each through-hole. By removing the plugs that are blocking the through-holes, seawater W flows out from those through-holes, and the predetermined depth h of the seawater W stored in each water storage section 5 is determined according to the height position of the through-hole from which the plugs are removed.

[0028] Furthermore, the height at which the seawater W is discharged from the outlet section 7a can be kept constant. Alternatively, the structure can be designed so that the outlet section 7a is not formed on the peripheral wall 7. In this structure, the seawater W stored in each reservoir section 5 flows over the peripheral wall 7, so the predetermined depth h of the seawater W stored in each reservoir section 5 is determined according to the height of the peripheral wall 7.

[0029] In this embodiment, the bottom surface 6 of each water storage section 5 is flat and at the same height level throughout its entire range. However, as illustrated in Figure 6, a water storage section 5 can also be used in which the height positions of the bottom surface 6 are at multiple different levels. The water storage section 5 illustrated in Figure 6 has two flat bottom surfaces 6 at different height levels. The bottom surfaces 6 at different height levels are separated by a partition projection 6a, and soil S is laid on each bottom surface 6. Because the height positions of the bottom surfaces 6 are at multiple different levels, even with a single water storage section 5, the stored seawater W can be at multiple different predetermined depths h1, h2. The number of bottom surfaces 6 at different height levels is not limited to two, but can be three or more. In Figure 6, the bottom surfaces 6 at different height levels are arranged in parallel in the longitudinal direction X, but a structure in which they are arranged in parallel in the width direction Y is also possible.

[0030] The seawater supply unit 9 continuously or intermittently supplies seawater W to the water storage unit 5. When supplying seawater W intermittently, for example, the supply and cessation of seawater W are repeated at predetermined time (predetermined period) intervals, or a supply schedule is set for the times (periods) when seawater W is supplied and the times (periods) when it is stopped.

[0031] In this embodiment, a pump is used as the seawater supply unit 9 to supply seawater W from a well (seawater well) in the land portion of the subsidence region 2. Various known pumps 9 can be used. A pipe 9a extending to the water storage unit 5 is connected to this pump 9. Various devices can be used for the seawater supply unit 9 as long as they can supply seawater W to the water storage unit 5. Conventional electricity can be used to drive the seawater supply unit 9, but greenhouse gas emissions can be suppressed by using electricity obtained from wind power generation or solar power generation, for example.

[0032] Instead of using a seawater well, seawater W can also be drawn from the sea area facing the subsidence zone 2 by the seawater supply unit 9 and supplied to the water storage unit 5. However, seawater W drawn directly from the sea contains various organisms, increasing the risk of the presence of organisms (natural enemies) that inhibit the growth of organisms being cultivated in the water storage unit 5. On the other hand, seawater wells contain a more limited range of organisms compared to seawater. There is also the risk of exposure to rapid water quality changes such as high water temperatures in summer and red tides. Therefore, to reduce the risks mentioned above, it is preferable to draw seawater W supplied by the seawater supply unit 9 from a seawater well.

[0033] In this seawall 1, seawater W is supplied to the water storage section 5 continuously or intermittently by the seawater supply unit 9. When a predetermined depth h of seawater W is stored in the water storage section 5, the seawater W flows out from the water storage section 5 through the outlet unit 7a and is supplied to the dock section 3. When a predetermined depth H of seawater W is stored in the dock section 3, the seawater W flows out from the dock section 3 into the sea through the outlet unit 4a. In other words, in this embodiment, seawater W is directly supplied to the water storage section 5 only by the seawater supply unit 9, and the dock section 3 is indirectly supplied with seawater W by the seawater supply unit 9 via the water storage section 5. The configuration is not limited to this, and it is also possible to configure the seawater supply unit 9 to directly supply seawater W to both the water storage section 5 and the dock section 3.

[0034] As illustrated in Figure 7, each reservoir 5 stores seawater W at a predetermined depth h, and new seawater W is supplied continuously or intermittently. Therefore, organisms suitable for the seawater W at that predetermined depth h can be cultivated in each reservoir 5. In detail, in this embodiment, eelgrass is cultivated in reservoirs 5a and 5b. The amount of sunlight irradiating the eelgrass changes depending on the predetermined depth h of the seawater W, so the predetermined depth h is set to one suitable for the growth of eelgrass. The organisms cultivated in the reservoir 5 are not limited to eelgrass; other examples include, for example, Zostera marina, Zostera japonica, and Zostera marina.

[0035] Seagrasses such as eelgrass absorb carbon dioxide and release oxygen through photosynthesis. Therefore, cultivating seagrasses such as eelgrass in reservoir 5 is beneficial for reducing greenhouse gases (carbon dioxide). Different types of organisms can also be cultivated in each reservoir 5.

[0036] By reducing the predetermined depth h of the seawater W stored in the reservoir 5, and by installing an appropriate size and shape of structure R on the bottom surface 6 of the reservoir 5, the structure R can protrude from the seawater W at the predetermined depth h, or soil S can be laid on the bottom surface 6 to create an environment similar to a tidal pool that appears at low tide. The soil S can be made of a material suitable for the desired organisms, such as sand or gravel. In a reservoir 5 with such an environment, organisms such as crabs that inhabit tidal pools and shellfish such as clams that inhabit tidal flats and sandy beaches can be cultivated. Alternatively, the predetermined depth h of the seawater W stored in the reservoir 5 can be reduced as much as possible, and soil S can be laid on the bottom surface 6 of the reservoir 5 to create an environment similar to a saline wetland. In a reservoir 5 with such an environment, organisms such as reeds that inhabit saline wetlands can be cultivated. By installing reservoirs 5 with different environments in this way, it is advantageous to allow a wider variety of organisms to inhabit the seawall 1.

[0037] With the structure illustrated in Figure 6, the seawater W stored in a single reservoir 5 can be set to multiple different predetermined depths h1 and h2, making it possible to cultivate organisms suitable for each predetermined depth h1 and h2 of seawater W. In other words, the structure illustrated in Figure 6 is advantageous for successfully cultivating multiple types of organisms in a single reservoir 5.

[0038] In dock section 3, various types of seaweed, such as kelp and wakame, can be cultivated, which are suitable for the underwater environment in which the installed object R is located. Therefore, it becomes possible to form a seaweed bed rich in organisms that inhabit seaweed in the water of dock section 3. Since seaweed absorbs carbon dioxide and releases oxygen through photosynthesis, it is beneficial for reducing greenhouse gases (carbon dioxide).

[0039] The dock area 3 and the reservoir area 5 are separated from the sea by a partition wall 4. Therefore, various organisms inhabiting the sea area that the seawall 1 faces do not directly flow into the dock area 3 and the reservoir area 5. As a result, the risk of organisms being cultivated in the dock area 3 and the reservoir area being inhibited by organisms (natural enemies) inhabiting the sea area that the seawall 1 faces or by changes in the marine environment is reduced. For this reason, the seawall 1 is advantageous for cultivating desired organisms.

[0040] In this embodiment, as illustrated in Figure 1, the widthwise position where the seawater supply unit 9 supplies seawater W to each reservoir 5 is substantially the same as the widthwise position of the outlet 7a of each reservoir 5. With such a structure, the flow direction of seawater W in each reservoir 5 becomes linear, increasing the risk of stagnation of seawater W. Therefore, it is also possible to make the widthwise position where seawater W is supplied and the widthwise position where it is discharged different. That is, the position where the seawater supply unit 9 supplies seawater W to the reservoir 5 and the position of the outlet 7a formed on the peripheral wall 7 of the reservoir 5 are made different in the widthwise direction (offset). This makes it even more advantageous to avoid stagnation of seawater W in each reservoir 5 and maintain a good environment for cultivating organisms.

[0041] As illustrated in Figure 8, a dock section 3 with a structure in which the height positions of the bottom surface 3a are at multiple different levels can also be adopted. This dock section 3 has two flat bottom surfaces 3a at different height positions, and the bottom surfaces 3a are stepped. The bottom surfaces 3a at different height positions are separated from each other by a partition inner wall 3b. Because the height positions of the bottom surfaces 3a are at multiple different levels, even with a single dock section 3, the stored seawater W can be stored at multiple different predetermined depths H1 and H2. In each region separated by the partition inner wall 3b, the predetermined depths H1 and H2 of the stored seawater W can be independently adjusted. The number of bottom surfaces 3a at different height positions is not limited to two, but can be three or more. In Figure 8, the bottom surfaces 3a at different height positions are arranged in parallel in the longitudinal direction X, but a structure in which they are arranged in parallel in the width direction Y can also be adopted. By adopting such a dock section 3, it is possible to cultivate organisms that are suited to each predetermined depth H1 and H2 and the environment of the bottom surface 3a. In other words, the structure illustrated in Figure 8 is advantageous for successfully raising diverse types of organisms in a single dock section 3.

[0042] Next, an example of the procedure for constructing this revetment 1 using the biological symbiotic revetment construction method of the present invention will be described.

[0043] This seawall 1 will be constructed using the subsidence area 2 illustrated in Figures 9 and 10. If the height of the existing subsidence area 2 is insufficient, it can be raised to the required height.

[0044] As illustrated in Figure 11, a partition wall 4 is erected at the seaward edge of the subsidence area 2, and necessary construction work, such as excavation, is carried out in the required areas of the subsidence area 2 to form the dock section 3. The partition wall 4 that separates the dock section 3 from the sea can be formed by driving piles or steel pipes, by casting concrete in place, or by installing a pre-fabricated concrete structure in the ground. The other wall surfaces and bottom surface 3a that make up the dock section 3 can be used with the ground surface of the subsidence area 2 exposed as is, or the ground surface can be covered with concrete or the like.

[0045] The water storage section 5 can be formed using various known materials such as concrete, wood, and metal. In addition, a seawater well is dug at an appropriate location in the subsidence area 2 to install a seawater supply section 9 and connect the piping 9a.

[0046] Seawater W is supplied to the formed dock section 3 by the seawater supply section 9 and stored there. The water reservoir section 5 is placed floating in the seawater W stored in the dock section 3. Then, seawater W is supplied to the water reservoir section 5 by the seawater supply section 9, and seawater W is discharged from the water reservoir section 5 to the dock section 3. As a result, seawater W is stored in the water reservoir section 5 to a predetermined depth h, and seawater W is discharged from the dock section 3 into the sea, storing seawater W to a predetermined depth H in the dock section 3. The upper end of the partition wall 4 is set higher than the sea surface and the water surface of the seawater W stored in the dock section 3. As the sinking region 2 sinks over time, the upper end of the partition wall 4, which sinks, is maintained at a position higher than the sea surface.

[0047] Furthermore, at appropriate times, the desired soil S will be laid on the bottom surface 6 of the reservoir 5. Organisms to be cultivated (seeds, seedlings, etc.) will be planted in the soil S. For example, in the reservoir 5, seeds or seedlings of seagrasses such as eelgrass will be planted. In the reservoir 5, which is designed to resemble a tide pool, crabs and shellfish will be released. In the reservoir 5, which is designed to resemble a saline wetland, seeds or seedlings of reeds to be cultivated will be planted in the soil S. In addition, desired seaweeds or their spores will be attached to the installation objects R placed in the water of the dock section 3.

[0048] The subsidence area 2 on which the seawall 1, illustrated in Figures 1 and 2, is constructed, subsides over time. Therefore, after a certain period of time (for example, 10 or 20 years), the seawall 1 in Figure 2 will be in the state illustrated in Figure 12 due to the subsidence of subsidence area 2. In Figure 12, the sea level is higher than in Figure 2.

[0049] Even if the seawall 1 sinks over time along with the sinking area 2, the upper end of the partition wall 4 remains above sea level. Therefore, even if the sinking area 2 sinks over time relative to the sea level, it is possible to maintain the underwater environment in the dock area 3 without substantially changing it. The reservoir 5 is installed floating on the seawater W stored in the dock area 3. As a result, the reservoir 5 can cultivate desired organisms suitable for its predetermined depth h without being affected by the time-dependent sinking of the sinking area 2 relative to the sea level. For example, the reservoir 5 can maintain a good environment where sunlight can reach the seagrass being cultivated. Therefore, this seawall 1 is advantageous in that it effectively utilizes the sinking area 2 while suppressing the time-dependent changes in the habitat of organisms caused by the time-dependent sinking of the sinking area 2.

[0050] In the embodiment described above, a relatively tall partition wall 4 is used from the initial construction of the seawall 1. That is, in the seawall 1 illustrated in Figure 2, the upper end of the partition wall 4 is positioned relatively high relative to the sea surface. In contrast, as illustrated in Figure 13, a relatively low partition wall 4 can also be adopted at the initial construction of the seawall 1.

[0051] In the case of the seawall 1 illustrated in Figure 13, the time when the sea level becomes level with the upper end of the partition wall 4 due to the time-dependent subsidence of the subsidence region 2 arrives earlier than in the case of the seawall 1 illustrated in Figure 2. Therefore, as illustrated in Figure 14, a new partition wall 4N is erected at the upper end of the partition wall 4 before the sea level rises above the upper end of the partition wall 4, which is subsiding due to the time-dependent subsidence of the subsidence region 2. In this way, the upper end of the partition wall 4 can be maintained at a position higher than the sea level. By erecting a new partition wall 4N, the predetermined depth H of the seawater W stored in the dock section 3 can also be increased.

[0052] The revetment 1 illustrated in Figure 1 is constructed at the corner of the subsidence area 2, but the revetment 1 can be constructed at any desired location in the subsidence area 2. In the revetment 1 illustrated in Figure 1, two sides of the rectangular dock section 3 in plan view are partition walls 4, but in the revetment 1 illustrated in Figure 15, only one side of the dock section 3 is partition wall 4. That is, the dock section 3 illustrated in Figure 15 is partitioned by three wall surfaces formed by the ground of the subsidence area 2 and one side partition wall 4. The other configurations are substantially the same as in the previous embodiment. Various configurations and structures described in the previous embodiment can also be adopted in this revetment 1.

[0053] This disclosure encompasses the following inventions. Invention 1: A biologically symbiotic seawall constructed in a subsidence region where the rate of subsidence over time relative to the sea surface is greater than a predetermined value, The system comprises a dock section formed at the seashore of the submerged area, a partition wall separating the dock section from the sea, a water reservoir section floating on the seawater stored in the dock section, and a seawater supply section for supplying seawater. A biologically symbiotic seawall is configured such that the upper end of the partition wall is set higher than the sea surface, seawater is supplied to the reservoir by the seawater supply unit, seawater flows out of the reservoir to the dock, and a predetermined depth of seawater is stored in the reservoir, and seawater flows out of the dock into the sea, and a predetermined depth of seawater is stored in the dock. Invention 2: The bio-symbiotic revetment according to Invention 1, wherein a predetermined shape of installation is provided protruding from and / or stacked inside the aforementioned dock section. Invention 3: The bio-symbiotic revetment according to invention 1 or 2, wherein the seawater supply unit is a pump that supplies seawater from a well in the land portion of the subsidence area. Invention 4: A biologically symbiotic seawall according to any one of Inventions 1 to 3, wherein an outflow section is formed in the partition wall, seawater flows from the dock section into the sea through the outflow section, and the height position from which the seawater flows out of the outflow section is variable. Invention 5: A biologically symbiotic revetment according to any one of Inventions 1 to 4, wherein a water reservoir outlet is formed in the water reservoir, seawater flows from the water reservoir to the dock through the water reservoir outlet, and the height position from which the seawater flows out of the water reservoir outlet is variable. Invention 6: The bio-symbiotic revetment according to any one of inventions 1 to 5, wherein at least one of the water storage sections has multiple different height levels at its bottom surface. Invention 7: A construction method for building a bio-friendly seawall in a subsidence area where the rate of subsidence over time relative to the sea surface is greater than a predetermined value, A dock section is formed at the seashore of the aforementioned subsidence area, and this dock section is separated from the sea by a partition wall. Seawater is supplied to the dock section to store the seawater, and the water storage section is placed in a floating state in the seawater stored in the dock section. Seawater is supplied to the reservoir, and seawater is discharged from the reservoir to the dock to store seawater to a predetermined depth in the reservoir, and seawater is discharged from the dock to the sea to store seawater to a predetermined depth in the dock, A method for constructing a biologically symbiotic seawall, wherein the upper end of the partition wall is set at a position higher than the sea surface, and the upper end of the partition wall, which sinks as the subsidence of the subsidence area over time, is maintained at a position higher than the sea surface. Invention 8: A method for constructing a biologically symbiotic seawall according to Invention 7, wherein a new partition wall is erected at the upper end before the sea level rises above the upper end of the partition wall that sinks as the aforementioned sinking region sinks over time. [Explanation of Symbols]

[0054] 1. Biologically Symbiotic Seawall 2. Settlement area 3 Dog section 3a Bottom 3b Partition wall 4 Partition wall 4N New partition wall 4a Outlet 4b Water level regulator 5 (5a, 5b) Water storage section 6. Base 6a Partition protrusion 7 Peripheral wall 7a Outlet for water storage section 8 Water level regulator 9. Seawater supply unit (pump) 9a Piping R Installation S soil W Seawater

Claims

1. A biologically symbiotic seawall constructed in a subsidence region where the rate of subsidence over time relative to the sea surface is greater than a predetermined value, The system comprises a dock section formed at the seashore of the submerged area, a partition wall separating the dock section from the sea, a water reservoir section floating on the seawater stored in the dock section, and a seawater supply section for supplying seawater. A biologically symbiotic seawall is configured such that the upper end of the partition wall is set higher than the sea surface, seawater is supplied to the reservoir by the seawater supply unit, seawater flows out of the reservoir to the dock, and a predetermined depth of seawater is stored in the reservoir, and seawater flows out of the dock into the sea, and a predetermined depth of seawater is stored in the dock.

2. The bio-symbiotic revetment according to claim 1, wherein a predetermined shape of installation is provided protruding from and / or stacked inside the dock section.

3. The bio-symbiotic revetment according to claim 1 or 2, wherein the seawater supply unit is a pump that supplies seawater from a well in the land portion of the subsidence area.

4. The biological symbiotic revetment according to claim 1 or 2, wherein an outflow section is formed in the partition wall, seawater flows from the dock section into the sea through the outflow section, and the height position from which the seawater flows out of the outflow section is variable.

5. The bio-symbiotic revetment according to claim 1 or 2, wherein a water reservoir outlet is formed in the water reservoir, seawater flows from the water reservoir to the dock through the water reservoir outlet, and the height position from which the seawater flows out of the water reservoir outlet is variable.

6. The bio-symbiotic revetment according to claim 1 or 2, wherein at least one of the water storage sections has multiple different height levels at its bottom surface.

7. A construction method for building a bio-friendly seawall in a subsidence area where the rate of subsidence over time relative to the sea surface is greater than a predetermined value, A dock section is formed at the seashore of the aforementioned subsidence area, and this dock section is separated from the sea by a partition wall. Seawater is supplied to the dock section to store the seawater, and the water storage section is placed in a floating state in the seawater stored in the dock section. Seawater is supplied to the reservoir, and seawater is discharged from the reservoir to the dock to store seawater to a predetermined depth in the reservoir, and seawater is discharged from the dock to the sea to store seawater to a predetermined depth in the dock, A method for constructing a biologically symbiotic seawall, wherein the upper end of the partition wall is set at a position higher than the sea surface, and the upper end of the partition wall, which sinks as the subsidence of the subsidence area over time, is maintained at a position higher than the sea surface.

8. The method for constructing a biologically symbiotic seawall according to claim 7, wherein a new partition wall is erected at the upper end before the sea level rises above the upper end of the partition wall that sinks as the subsidence of the subsidence region over time.

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