JPH11269839A - Revetment with developing base for tidal flat - Google Patents

Abstract

PROBLEM TO BE SOLVED: To develop a tidal flat by forming recesses having a specified area at the surface of a revetment in between high and low tidal water's edges and providing a developing base having a down slope with a specified angle to the water bottom. SOLUTION: A developing base 2 for a tidal flat gently going down at 30 degrees or smaller inclination from a land toward a water bottom is formed in between high and low tidal water's edges to form a revetment 1. The inclination of the developing base 2 is gradually lessened from the land side to the water bottom side to reduce the erosive action of flowing water and accumulate sand, mud, etc., transferred by flowing water at the high tide on the developing base 2. Then, stones 16 or the like are piled on the surface of developing base 2 to form a number of recesses 3 and accelerate settling of sand, mud, etc., by the settling action of the recesses 3. Further, the recesses 3 are formed at 30% or more area on the surface of developing base 2 to effectively settle sand, mud, etc., and take root of aquatic plants, halophytic plants, and alga and fix small animals or the like. In this way, disappeared tidal flats can be restored and a favorable habitat for creatures can be formed and further, the dissolved oxygen in the tidal flat can be increased and moreover, water can be purified.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a revetment with a tideland formation stand, and more particularly to a revetment for forming a tideland by pit accumulation and protection from erosion by running water.

[0002]

2. Description of the Related Art Seawalls are being constructed to protect shores such as inland seas, canals, and waterways from erosion due to flowing water. An example of a conventional revetment is a concrete retaining wall or sheet pile or the like which is installed substantially vertically along the boundary between land and water (hereinafter referred to as an upright revetment). However, upright seawalls have poor hydrophilicity or poor water retention, and have problems such as destruction of living habitats.

[0003] On the other hand, a gentle slope revetment is being constructed as a revetment having a structure that has little effect on a biological habitat. FIG. 3 (A)
Shows an example of a conventional gentle slope revetment 10 in which a portion higher and lower than the low tide water surface L is an upright revetment 11 and a gentle slope revetment 10, respectively. For example, by covering the gentle slope revetment 10 with sand or mud, etc. It secures a habitat on the bottom of the water. FIG. 3B shows an example in which the entirety from the high tide water surface H to the water bottom 14 is a gentle slope revetment 10, for example, a gentle slope revetment.
By backfilling sand and mud etc. on the top 10, a wide habitat is secured. In the drawing, reference numeral 12 indicates a seawall top, and reference numeral 13 indicates a wave return.

[0004]

However, the gently sloped revetment 10 of FIG. 3 has a problem that it does not necessarily provide a favorable habitat, although the habitat is expanded. One of the causes is that in the natural world, the tidal flat formed between the shoreline at high tide and the shoreline at low tide (hereinafter referred to as the intertidal zone) is a place where various organisms inhabit as a contact place between water, land and the atmosphere. On the other hand, the tidal flat is difficult to form in the intertidal zone on the gentle slope revetment 10 in Fig. 3.

It is difficult to form a tidal flat with the conventional gentle slope revetment 10 because the slope angle of the gentle slope revetment 10 is as large as about 30 to 60 degrees, and as shown in FIG. In the case of the masonry structure, it is considered that since there is no concave portion suitable for accumulation on the surface, the backfilled sand and the like easily flow out, and conversely, the accumulation of the sand and the like hardly occurs.

[0006] From the viewpoint of coexistence with nature, there is a demand for the development of a revetment structure capable of securing a better habitat for living organisms than a conventional gentle slope revetment. In particular, it is desired to actively create good biological habitats by restoring tidal flats that have disappeared in inland seas, canals, waterways, rivers, and the like.

[0007] Therefore, an object of the present invention is to provide a seawall with a tidal flat formation platform for actively forming a tidal flat.

[0008]

Referring to the embodiment of FIGS. 1 and 2, a seawall with a tideland formation stand of the present invention has a number of depressions 3 formed on the surface between a shoreline at high tide and a shoreline at low tide. The tideland is provided with a tidal flat formation table 2 whose gradual descending gradient from the land side to the water bottom side is gradually reduced. Preferably, at least 30% of the surface area of the tidal flat 2 is a depression 3.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A revetment 1 according to the present invention has a tidal flat forming platform 2 which is gently descended from the land side to the water bottom side between a shoreline at a high tide and a shoreline at a low tide, and FIG. FIG. 2 is a cross-sectional view of the example, and FIG. By making the gradient of the tidal flat 2 sufficiently gentle and gradually decreasing the gradient from the land side to the water bottom side, the erosion of running water is reduced,
Sand and mud carried by the high tide are deposited on the tidal flat 2. Preferably, the inclination of the tidal flat 2 is 30 degrees or less. The tidal flat 2 can be thought of as a shallow water bottom of the population, and the shallow distance can be determined according to the tidal flat to be formed.

[0010] Further, a number of depressions 3 are provided on the surface of the tideland formation table 2, and the accumulation of the depressions 3 promotes the accumulation of sand and mud. Preferably, recesses 3 of different sizes are provided on the tidal flats 2. For example, when the tidal flats 2 are made of a masonry structure made of stones 16 having substantially the same size as in the illustrated example, the pit 3 is surrounded by several dents 3 having a size similar to that of a single stone 16. Depression 3 of size, depression 3 of size surrounded by dozens of stones 16
Etc. can be provided. However, the tidal flats 2 are not limited to the masonry structure, and may be made of, for example, concrete or a material having little influence on the biological habitat. Further, the depth of the depression 3 can be about 10 to 30 cm.

According to the experiment of the present inventor, sand mud and the like are effectively deposited on the depression 3 by making the depression 3 at least 30% of the surface area of the tideland development table 2, and the tideland is formed on the tideland development table 2. Could be created. However, the ratio of the depression 3 to the surface area of the tidal flat formation table 2 of the present invention is not limited to this example, and can be 30% or less in consideration of the speed of flowing water, the type of living organisms, and the like. In addition, since the seawall 1 of the present invention reduces the erosion effect of flowing water, the tideland can be artificially formed in a short period of time by artificially covering the tideland formation table 2 with sand or mud.

The depression 3 in which sand mud or the like is deposited can be a good habitat for various small animals such as sand crabs such as black crabs, tiger crabs, and black crabs; In addition, the tidal flat created on the tidal flat 2 by the inhabitation of these organisms becomes a predation place for other organisms such as birds, so that the ecosystem of the tidal flat can be expected to be restored through the food chain.

[0013] Preferably, at least 50% of the surface area of the tidal flat formation table 2 is a depression 3. By expanding the area of the depression 3, the habitat of small animals can be expanded, and the creation of a tidal flat where a larger number of small animals inhabit can be expected. In this case, sand mud or the like is artificially coated on the tidal flat formation base 2 in a layered manner from the lower layer in the order of fine particles, whereby a tidal flat closer to the natural world can be formed in a short period of time. This is because sand mud and the like are deposited in layers in the natural tidal flat according to the fineness of the particles, and each layer is considered to be a habitat for a different small animal.

More preferably, the surface area of the tidal flat 2 is 70
% Is defined as the depression 3. By setting the depression 3 to 70% or more of the surface area, the contact area between the depression 3 and the running water can be sufficiently widened.
It can be expected that a layered structure according to the fineness of the particles is naturally formed. Therefore, even if the operation of covering the tidal flat formation table 2 with artificial layered sand mud or the like is omitted, a tidal flat that is extremely close to the natural world can be formed on the tidal flat formation table 2.

[0015] Thus, the object of the present invention, that is, the provision of "bank protection with a tidal flat formation platform for actively forming tidal flats" can be achieved.

[0016]

In the embodiment of FIGS. 1 and 2, the slope of the revetment 1 toward the water bottom near the shoreline at high tide is set to 30 degrees or more, and the slope of the water bottom from the area near the shoreline at high tide is set to 30 degrees or less. I have. By setting the slope near the shoreline at high tide to 30 degrees or more, the same level of protection against erosion due to flowing water as the conventional gentle slope revetment 10 shown in FIG. 3B can be expected.

In the illustrated example, the upright revetment 11a is provided on the water bottom side from the lower end of the tidal flats 2; however, a gentle slope revetment may be used instead of the upright revetment 11a. In addition, if necessary, rooting or the like may be provided at the lower end of the upright seawall 11a.

In the illustrated example, a road 5 is provided in a portion of the revetment 1 above the shoreline at the time of high tide and in which there is no submersion in order to prepare for the recovery of the garbage that has been launched and for an emergency. A masonry upright revetment 11b is formed in the rear part of the road 5, and the revetment top 12 on the upright revetment 11b is covered with soil. Seawall top 1
By breeding various kinds of plants, the inhabitation of living creatures such as land crabs and fungus can be promoted throughout the revetment.

In addition, plants, for example, aquatic plants living mainly in water, such as reeds and eelgrass, halophytes, seaweeds, etc. that grow on the beaches, coasts, dunes, inland salt lands, etc. By fixing algae such as attached algae, the dissolved oxygen in the tidal flat can be increased by photosynthesis of plants, and a water purification function can be added. The creation of a better biological habitat can be expected by the establishment of these plants.

[0020]

As described above, the revetment with a tidal flat according to the present invention has a number of depressions formed on the surface between the shoreline at high tide and the shoreline at low tide, and gently descends to the bottom of the water. Since the table is provided, the following remarkable effects are exhibited.

(A) The tidal flat which has disappeared at the waterside or the like can be restored and a favorable living environment can be positively created. (B) By fixing aquatic plants, halophytes, algae, etc. in the depressions of the tidal flats, the dissolved oxygen in the tidal flats can be increased, and the water can be further purified. (C) It can be widely applied to seawalls and embankments.

[Brief description of the drawings]

FIG. 1 is a sectional view of an embodiment of a seawall according to the present invention.

FIG. 2 is a plan view of the revetment of the present invention viewed from the II-II direction in FIG.

FIG. 3 is an explanatory view of a conventional gentle slope revetment.

FIG. 4 is an explanatory diagram of a conventional masonry on a gentle slope revetment.

[Explanation of symbols]

 1 ... revetment with tideland development stand 2 ... tideland development stand 3 ... recess 5 ... road 10 ... gentle slope revetment 11 ... upright revetment 12 ... revetment top 13 ... wave return 14 ... water bottom 16 ... stone

Claims (5)

[Claims] 1. A tidal flat forming platform having a number of depressions formed between a shoreline at a high tide and a shoreline at a low tide, and a gentle downward gradient from a land side to a water bottom side is gradually reduced. A revetment with a tidal flat created by forming a tidal flat by sedimentation. 2. The revetment according to claim 1, wherein 30% or more of the surface area of the tidal flat is used as the depression. 3. The seawall according to claim 1, wherein aquatic plants, halophytes, algae and / or small animals are fixed in the depressions of the seashore. 4. In the revetment according to any one of claims 1 to 3,
A revetment with a tidal flat that has the tidal flat as a masonry structure. 5. In the revetment according to any one of claims 1 to 4,
A revetment with a tidal flat forming stand, wherein the slope of the revetment toward the water bottom near the shoreline at high tide is 30 degrees or more, and the slope of the reef near the shoreline at the time of high tide is 30 degrees or less.