JP2005105719A - Aquatic plant zone in water region having ebb and flow and affected by salt water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an aquatic plant zone for preventing salt water from remaining in a vegetation soil layer at the low tide as much as possible, supplying fresh water to the vegetation soil layer, and raising aquatic plant such as reed. <P>SOLUTION: This zone 20 of aquatic plant such as reed is constructed in a predetermined area in a brackish water region in the mouth of a river. This zone 20 is provided with a vegetation base 26 whose upper face is set to a place higher than water surface height HL at low tide, the vegetation soil layer 28 provided on the vegetation base 26, a soil washing-away prevention means (for example, a bag body 36 of a sandbag 40) for preventing soil in the vegetation soil layer 28 from being washed away, and a driving channel 50 for leading fresh water into the vegetation soil layer 28. The driving channel 50 has an introduction port 52a in an upstream side part of the river whose height becomes larger than water surface height Hh at high tide in the brackish water region in the mouth of the river and an introduction port 52a in the river in a part in the vicinity of the mouth of the river whose water level becomes higher than water surface height HL at a low tide position in the brackish water region in the mouth of the river by a pipe channel 52 in which a discharge port 52b faces the vegetation soil layer 28. The discharge port 52b can be constituted by a pipe channel facing the vegetation soil layer 28. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an aquatic plant zone which is provided in a predetermined area of a water area affected by tidal salt water and which aims to grow aquatic plants such as reeds.

  It is known that reeds and other aquatic plants that grow on the waterside of rivers and lakes contribute greatly to the natural purification of water quality contaminated by domestic wastewater, etc. Etc., it has been actively carried out to artificially create a reed field and cultivate aquatic plants, and to reproduce the lost reed field and naturally return.

  This artificial reed field is built around a predetermined building area where a dam to prevent the loss of sand and mud etc. is desired, and vegetation soil is put inside and reed stock and underground stems are planted, and freshwater bodies Reproduction of Yoshihara can be achieved.

  By the way, in recent years, attempts have been made to create such artificial reed fields in the brackish water area around the estuary. In the brackish water area, fresh water from the river flows into the surface layer of seawater, and tides Because the tide level changes, if the structure is the same as that of a conventional freshwater artificial reed field, the seawater in the brackish water that has entered the artificial reed field will not be discharged, and the concentration of that salt will increase, preventing reed growth. It will be rare. For this reason, in the aquatic plant zone provided in the brackish water area, it is necessary to keep the salinity of the vegetation soil low.

  Thus, as an aquatic plant zone in which aquatic plants can grow even in such brackish water areas, there has been a proposal of an artificial reed field disclosed in, for example, Patent Document 1. As shown in FIG. 8, the proposed artificial reed field surrounds a predetermined building area along a concrete revetment 2 in a U shape with a stone embankment 4, and sand is placed inside the stone embankment 4. By providing a soil runoff prevention layer 6 formed by stacking filled sandbags and crushed stones, a permeable soil runoff prevention dike 8 is constructed. Inside the soil runoff prevention dike 8, the upper surface is flat and at a low tide level. A vegetation base 10 positioned higher than the water surface is provided, and a vegetation soil 12 is further placed on the vegetation base 10 to plant and grow aquatic plant seedlings and underground stems such as reeds.

And according to this aquatic plant belt, even if brackish water is flooded on the vegetation soil 12 at the high tide level of the rising tide, and the water level is lowered at the subsequent tide, the vegetation soil 12 is permeable to the soil erosion prevention levee. 8, the brackish water can be discharged through the soil runoff prevention dam 8 while preventing the outflow of the vegetation soil 12 to the outside, and the brackish water level is lowered to a low tide level. The function of the fresh water covering the surface layer of the salt water to wash away the salt remaining in the vegetation soil 12 is to prevent an increase in the salt concentration of the vegetation soil 12.
JP 2002-320409 A

  However, in the aquatic plant zone of the conventional brackish water area, the flooded brackish water is constructed by osmotically flowing inside the dried vegetation soil 12 and the base 10 and surrounding the vegetation soil 12 at the time of tide. However, if it is an aquatic plant zone that is built around a small area, it will not be a problem. For example, when a large aquatic plant zone is constructed surrounding a large area along the revetment 2, there is a concern that it takes time to discharge and move the water, and the salinity cannot be sufficiently removed. And if the next tide is filled before the salinity in the soil can be fully removed, the salinity in the vegetation board will not drop easily, resulting in poor growth of aquatic plants such as reeds. . In addition, the salinity cannot be reduced in water areas where offshore fresh water does not reach, and it cannot be applied.

  The present invention has been made in view of such circumstances, and its purpose is to prevent as much as possible retention of salt water in the vegetation soil layer at the time of ebb tide, and to supply fresh water in the vegetation soil layer. The purpose of the present invention is to provide an aquatic plant zone that can promote the reduction of salinity as much as possible and can grow aquatic plants such as reeds in the water area affected by tidal salt water.

  In order to achieve the above object, the present invention comprises an aquatic plant zone that is affected by tidal salt water as follows.

  The invention according to claim 1 is an aquatic plant zone such as reed that is formed in a predetermined area of a water area affected by tidal salt water, and the vegetation whose upper surface is set higher than the water surface height at low tide A base, a vegetation soil layer provided on the vegetation base, a soil loss prevention means for preventing the soil of the vegetation soil layer from being washed away, and a fresh water supply means for supplying fresh water as a fresh water source to the vegetation soil layer It is characterized by having.

  The invention according to claim 2 is characterized in that the fresh water supply means is a water conduit that guides fresh water from a fresh water source located higher than the vegetation base to the vegetation base.

  The invention according to claim 3 is characterized in that the fresh water source is a reservoir.

  In the invention according to claim 4, the water area affected by the salt water is an estuary brackish water area, the fresh water source is a river flowing into the brackish water area, and the water conduit is at a high tide level in the estuary brackish water area. In addition to having an inlet at the upstream of the river that is higher than the water level, the outlet is formed by a conduit that faces the vegetation soil layer.

  In the invention according to claim 5, the water area affected by the salt water is an estuary brackish water area, the fresh water source is a river flowing into the brackish water area, and the water conduit is at a low tide level in the estuary brackish water area. In addition to having an introduction port in the river near the estuary where the water level is higher than the height of the water surface, the discharge port is constituted by a pipe line facing the vegetation soil layer.

  The invention according to claim 6 is characterized in that the vegetation base is permeable ground.

  According to the invention of the aquatic plant zone affected by tidal salt water according to claim 1, the water level is lowered below the vegetation soil layer formed on the vegetation base at the low tide level, and the vegetation base Since the upper part is exposed on the water surface, drainage in the vegetation sandbag layer is performed as soon as possible, and fresh water is supplied to the vegetation soil layer from the fresh water source by the fresh water supply means. The fresh water functions to wash away the salt water in the vegetation soil layer, so that the salt water hardly stays in the vegetation soil layer. For this reason, it is possible to prevent the salinity concentration of the vegetation soil layer from increasing and to grow aquatic plants such as reeds. Moreover, when draining, the loss of vegetation soil from the vegetation soil layer prevents soil loss. Prevented by means.

  According to the invention of the aquatic plant zone affected by tidal salt water according to claim 2, the fresh water supply means is composed of a conduit for guiding fresh water from a fresh water source located higher than the vegetation base to the vegetation base. Therefore, it is possible to always supply fresh water to the vegetation soil layer at a low price without using a power machine such as a pump without incurring a power cost.

  According to the invention of the aquatic plant zone affected by tidal salt water according to claim 3, since the fresh water source is a reservoir, for example, a nearby lake or pond or a rainwater reservoir is used as the reservoir. As a result, fresh water can be supplied stably and inexpensively without any power costs.

  According to the invention of the aquatic plant zone affected by tidal salt water according to claim 4, the water area where the aquatic plant zone is provided is an estuary brackish water area, the river flowing into the brackish water area is a fresh water source, and the estuary brackish water area Since the inlet is in the river near the estuary where the water level is higher than the water level at the low tide level of the river, and the outlet is constructed by a conduit that faces the vegetation soil layer, The fresh water from the river can always be supplied to the vegetation soil layer at a low cost without power costs, and in the estuary brackish water, light fresh water flowing from the river is layered on heavy salt water (thickness of several centimeters to several tens of centimeters). Therefore, when the water level is lowered during the low tide, the lower layer salt water is drawn first, and then the upper fresh water passes through the vegetation soil layer and falls downward. However, the vegetation soil layer can be washed away and the salinity can be reduced. To be promoted.

  The invention of the aquatic plant zone of the water area affected by salt water with tide according to claim 5 is a water area affected by the salt water as an estuary brackish water area, and the fresh water source is a river flowing into the brackish water area, The headrace has an inlet in the river near the estuary where the water level is higher than the water level at the low tide level in the estuary brackish water area, and the outlet is configured by a pipe line that faces the vegetation soil layer Therefore, the fresh water of the river can be led to the vegetation soil layer at low cost by using the water head pressure between the water level at the introduction port and the water level at the discharge port at least at the time of low tide. In addition to being able to reduce the concentration of salt as much as possible by rinsing, the vegetation soil layer can be washed away even in the upper fresh water when the water level is lowered during the ebb tide as above, Reduces salt content as much as possible and leads And obtained as much as possible short constituting a conduit length of the road it can be reduced in cost.

  According to the invention of the aquatic plant zone affected by salt water with tide according to claim 6, since the vegetation base is formed on the water-permeable ground, it can function as a drainage layer, further improving drainage. Thus, an increase in the salinity concentration of the vegetation soil layer can be further suppressed.

  Hereinafter, preferred embodiments of an aqueous plant zone affected by tidal salt water according to the present invention will be described in detail with reference to the accompanying drawings.

  1 is a plan view showing an outline of the aquatic plant zone of the present invention, FIG. 2 is a sectional view taken along the line II-II in FIG. 1, and FIG. 3 is a sectional view taken along the line III-III in FIG. 4 is a longitudinal sectional view of a planting sandbag, and FIG. 5 is a perspective view showing a housing and a planting sandbag loaded on the upper side thereof.

  As shown in FIG. 1, the aquatic plant zone 20 is formed in a predetermined area of a brackish water area of a river mouth where a river 22 is poured into a sea 24 and seawater and fresh water are mixed, and is used for growing aquatic plants such as reeds. The aquatic plant belt 20 is provided to extend offshore with a predetermined width along the concrete revetment 2, and includes a vegetation base 26 in which the upper surface 26a is set higher than the water surface height HL at low tide, and the vegetation. And a vegetation soil layer 28 provided on the base 26.

  The vegetation base 26 is formed of a permeable gravel ground 29 and forms a drainage layer. In this embodiment, as shown in FIG. Is laid vertically and horizontally on the water bottom ground 34. Then, on the upper surface 26a of the vegetation base 26 formed by laying a large number of the skeletons 32, a large number of vegetation sandbags are formed, in which a vegetation soil 38 is filled in a bag body 36 as shown in FIG. (Hereinafter referred to as a vegetation sandbag) 40 is further laid and placed vertically and horizontally, whereby a vegetation soil layer 28 is formed.

  The bag body 36 of the vegetation sandbag 40 uses a fine woven fabric 42 that can prevent outflow of soil at least on the peripheral side surface 36a and the bottom surface 36b, while the upper surface 36c has a sprout of aquatic plants. A coarse nonwoven fabric 44 that does not impede the passage of the stem and the growth of the stem is used, and is arranged to be openable and closable. That is, a vegetation soil layer 28 formed by arranging a large number of vegetation sandbags 40 vertically and horizontally is provided with a fine cloth on at least the peripheral side surface and the bottom surface as a soil loss prevention means for preventing soil loss. It has been configured. In addition, rhizomes, seedlings, and seeds of aquatic plants such as reeds are embedded in the vegetation soil 38 filled in the bag body 36 in advance.

  More specifically, for example, as shown in FIGS. 2 and 5, the housing 32 has a rectangular parallelepiped shape, and a frame 45 made of an angle material or a rod material is provided on each side thereof. The mesh material 46 knitted in a bag shape is formed by being locked. The cracked stone 30 placed in the housing 32 is filled to a predetermined height from the bottom ground 34 so that its upper end portion is exposed from the low tide level water surface HL at low tide, and is formed of the cracked stone 30. The gravel ground 29 is set so that its upper part is exposed on the water surface at low tide.

  In addition, a space for inserting a vegetation sandbag 40 is further provided in the upper portion of the casing 32 filled with the walnut stone 30, and the vegetation sandbag 40 is loaded in the upper space. The peripheral side portion is restrained by the frame 45 and the net member 46 so that the mold is prevented from being deformed. The vegetation sandbag 40 may be filled with vegetation soil 38 in advance and then inserted into the upper space of the housing 32 and placed on the gravel ground 29. However, as shown in FIG. Only 36 may be inserted into the upper space and fixed and locked to the frame 45, and after dredging, the bottom mud may be sucked up by a pump or the like as vegetation soil 38 and filled through the pipe 48. Alternatively, when the water content of the bottom mud is high, the bottom mud may be classified and dehydrated using a screw decanter, a sand collector or the like to become a material such as a decanter cake, and then filled. In addition to the bottom mud, mountain soil, river sand, etc. may be used as the material for the vegetation soil 38. Further, as a material for forming the gravel ground 29 by being put in the housing 32, a recycled material such as a concrete lump or oyster shell may be used in addition to the above-mentioned cracked stone 30.

  In the aquatic plant zone 20 having such a configuration, the water level in the brackish water area is lowered below the vegetation sandbag 40 forming the vegetation soil layer 28 at the time of low tide at the time of ebb tide. Since the upper part of the vegetation base 26 formed in 29 is exposed on the water surface, the drainage in the vegetation sandbag 40 can be performed as soon as possible, and when the water surface level is lowered, the lower salt water is first drawn. Since the fresh water in the upper layer passes through the vegetation soil layer 28 and decreases downward, the fresh water layer functions to wash away the salt water in the vegetation soil layer 28, and salt water stays in the vegetation soil layer 28. It becomes difficult to do. In addition, since the gravel ground 29 with good drainage can be easily installed at an appropriate height, the frequency of the vegetation soil layer 28 contacting the fresh water (thickness of several centimeters to several tens of centimeters) of the brackish water surface layer as much as possible. Get enhanced. For this reason, it is possible to prevent the salinity concentration of the vegetation soil layer 28 from increasing and to grow aquatic plants such as reeds. Moreover, since the bottom part of the vegetation sandbag 40 can be exposed to air at low tide, the aerobicization of the soil is promoted, and septic bottom mud can be effectively used as vegetation soil.

  Further, the vegetation sandbag 40 forming the vegetation soil layer 28 uses fine woven fabric 42 on the peripheral side surface 26a and the bottom surface 36b of the bag 36, so that the soil particles of the filled vegetation soil 38 flow out during drainage. Therefore, the vegetation soil layer 28 having a function of preventing soil loss can be easily created.

  In addition, since there is a drainage layer of gravel ground 29 at the lower part, dewaterability of bottom mud and the like is improved, and a stable vegetation soil layer 28 can be provided. Furthermore, since the vegetation sandbag 40 covers the upper surface of the vegetation soil 38 using a coarse nonwoven fabric 44 on the upper surface of the bag body 36, the shoots and stems of various aquatic plants can be easily extended. Or there is no possibility that the bottom mud of the filled vegetation soil 38 is eroded. Here, the upper surface of the vegetation sandbag 40 is more preferably covered with gravel or the like in addition to the nonwoven fabric 44.

  A vegetation base 26 is formed in advance by installing a frame structure such as a frame 32 at a construction position in a predetermined construction planned area in the brackish water area, and a vegetation sandbag 40 is laid and arranged vertically and horizontally on the vegetation base 26. By going, the vegetation base 26 and the vegetation soil layer 28 formed of the gravel ground 29 can be easily and quickly created according to the size of the construction area. Further, by fixing and locking the upper end portion of the vegetation sandbag 40 to the frame of the vegetation base 26 and filling the bottom mud and the like, there is no need to lift and install the bag body after the dehydration process. Thus, the workability can be further improved. In addition, when using bottom mud with high water content, etc., if the decanter cake after classifying the dredged bottom mud with a screw decanter is used, the water content can be kept low while ensuring fluidity. Therefore, the workability is good and the volume reduction rate by dehydration after filling is low, so that deformation of the finished shape can be prevented.

  By the way, in this invention, as shown in FIG.1 and FIG.3, the freshwater supply means 49 is provided in the vegetation soil layer 28 in the said aquatic plant belt 20. FIG. The fresh water supply means 49 may be configured to provide a water conduit 50 that guides the fresh water of the river 22 flowing into the brackish water area to the vegetation soil layer 28, for example. In the illustrated example, the water conduit 50 has an inlet 52a in the upstream portion of the river that is higher than the water surface height Hh at the high tide level in the brackish water area, and the outlet 52b is the vegetation soil layer 28 of the aquatic plant zone 20. The pipe 52 is installed along the river 22 while being swept through the water.

  If the fresh water supply means 49 comprising such a water conduit 50 and the like is provided, the fresh water of the river is constantly led to the vegetation soil layer 28 and supplied without requiring power etc. regardless of the tides. And the salt concentration of the vegetation soil layer 28 can be further suppressed as low as possible.

  Further, as shown in FIGS. 6 and 7, the conduit 52 of the water conduit 50 can be shortened in its entire length by setting the installation position of the inlet 52 a near the river mouth. That is, the conduit 50 has the inlet 52a in the river near the estuary where the water level is higher than the water level at the low tide level in the estuary brackish water area, and the conduit 52 where the outlet 52b faces the vegetation soil layer 28. Consists of. And according to the said structure, the fresh water of a river can be led and supplied to the vegetation soil layer 28 using the water head pressure of the water level of the inlet 52a part and the water level of the outlet 52b part which arise at least at the time of low tide, and the said fresh water Can wash out the salt and reduce its concentration as much as possible. That is, even if the inlet 52a is set in the vicinity of the estuary basin, the tide level at the installation site of the outlet 52b facing the vegetation soil layer 28 of the aquatic plant zone 20 at the time of tide from the high tide level is that of the inlet 52a. If it becomes lower than the water surface level of an installation site | part, it will be possible to supply fresh water to the vegetation soil layer 28 at least using the water head pressure at the time of the said low tide.

  In the illustrated embodiment, fresh water of the river 22 is guided by the conduit 50, but if there is a reservoir such as a freshwater swamp or pond in the vicinity, fresh water is introduced from the reservoir such as the swamp or pond. Alternatively, a rainwater receiving reservoir or the like may be installed to introduce fresh water from the reservoir. Further, fresh water may be pumped from the well and this may be used as a key to lead to the vegetation soil layer 28 through the water conduit.

  8 and 9 show a modification of the vegetation soil layer 28 formed on the vegetation base 26, FIG. 8 is a plan view of the outline, and FIG. 9 is a view taken along the line IX-IX in FIG. It is sectional drawing. As shown in the drawing, this modification is different in that a vegetation soil layer is not formed by laying a large number of vegetation sandbags on a vegetation base as in the above-described embodiment. Note that the fresh water supply means 49 and the like are completely the same as those of the above-described embodiment, and common points thereof are denoted by the same reference numerals and detailed description thereof is omitted.

  That is, this aquatic plant belt 20A is provided with a soil retaining means 54 in a U-shape along the outer periphery of a vegetation base 26 formed by laying a skeleton 32 filled with cracked stone 30. The finely woven fabric 42 disposed on the peripheral side surface is locked to the inner surface of the earth retaining means 54, while the woven fabric 42 disposed on the bottom surface is laid on the upper surface 26a of the vegetation base 26. Thus, the vegetation soil layer 28 is formed by filling the vegetation soil 38 inside these woven fabrics 42.

  Here, in the illustrated example, as the soil retaining means 54, a skeleton 32 </ b> A filled with the cracked stone 30 is used in the same manner as the vegetation base 26. The housing 32A is laid on the upper surface 26a of the vegetation base 26 along the outer periphery thereof, and the finely woven fabric 42 is continuously formed on the housing 32A over the entire length along the inner peripheral side surface. Locked and provided. Note that the earth retaining means 54 is not limited to the case 32A filled with the above-mentioned cracked stone 30, and instead of the case 32A, the earth pressure of the vegetation soil 38 can be borne through the woven fabric 42. It is also possible to use a fence body.

  And the water conduit 50 of the fresh water supply means 49 guides the fresh water of a river to the vegetation soil layer 28 comprised as mentioned above, and the pipe line 52 which forms the water conduit 50 is a soil retaining means in the example of illustration. The discharge port 52b is disposed so as to face the vegetation soil layer 28 over the housing 32A that forms 54, and the salt content of the vegetation soil layer 28 is washed by the fresh water supplied from the fresh water supply means 49. The concentration is reduced as much as possible.

  Moreover, although the illustrated example embodiment and the modification thereof illustrate the aquatic plant belt 20 provided along the concrete revetment 2, the present invention is not limited to this and is offshore that is separated from the revetment. It can also be constructed as a floating island. Furthermore, even if the constructed water area of the floating island is an area affected only by tidal salt water that does not reach the fresh water from the river, the fresh water supply means can reliably supply fresh water to the vegetation soil layer. As a result, the aquatic plant can be allowed to grow.

  In addition, in the above-described embodiment and its modification, the vegetation base 26 is formed on the permeable gravel ground 29, but the vegetation area of the aquatic plants is efficiently secured in the construction area of the aquatic plant zone. If the above point is emphasized, even if the vegetation base 26 is not necessarily provided with water permeability, as long as the upper surface of the vegetation base 26 is exposed to the low tide level at the time of low tide, Since the drainage can be improved and fresh water is supplied from the fresh water supply means 49, the salt water can be discharged quickly, so that the vegetation base 26 is constructed by laying a non-permeable concrete block or the like. But there will be no trouble. Moreover, even if it exists in a soil runoff prevention means, it is not limited to the woven fabric 42 of the example of illustration mentioned above.

  That is, according to the present invention, the vegetation base 26 whose upper surface is set higher than the water level at low tide, the vegetation soil layer 28 provided on the vegetation base 26, and the soil of the vegetation soil layer 28 are washed away. And a fresh water supply means 49 provided on the premise of an aquatic plant zone such as reed that is constructed in a predetermined area of the water area affected by tidal salt water. The formation forms of the vegetation base 26, the vegetation soil layer 28, the soil loss prevention means, and the like can be modified in various ways without departing from the scope.

It is a top view which shows the outline | summary of the water plant zone of the brackish water area which concerns on this invention. It is the II-II arrow directional cross-sectional view in FIG. FIG. 3 is a cross-sectional view taken along line III-III in FIG. 1. It is a longitudinal cross-sectional view of a vegetation sandbag. It is a perspective view which shows a skeleton and the vegetation sandbag loaded in the upper part. It is a top view showing other implementation carrying of a fresh water conduit. FIG. 7 is a cross-sectional view taken along the line VII-VII in FIG. 6, where (a) is a diagram illustrating a state during rising tide, and (b) is a diagram illustrating during tide. It is a top view which shows the outline | summary of the modified embodiment example. FIG. 9 is a cross-sectional view taken along line IX-IX in FIG. 8. It is a longitudinal cross-sectional view of the conventional vegetation zone.

Explanation of symbols

2 Concrete revetment 20, 20A Aquatic plant zone 22 River 24 Sea 26 Vegetation base 26a Vegetation base top surface 28 Vegetation soil layer 29 Gravel ground 30 Split stone 32, 32A Shaft 34 Submarine ground 36 Bag body 36a Bag body side surface 36b Bag bottom face 36c Upper surface of bag body 38 Vegetation soil 40 Vegetation sandbag 42 Woven cloth 44 Non-woven fabric 45 Frame 46 Net member 49 Fresh water supply means 50 Water conduit 52 Pipe 52a Inlet 52b Discharge outlet 54 Earth retaining means

Claims (6)

  An aquatic plant belt such as reed that is constructed in a predetermined area of the water area affected by tidal salt water, and a vegetation base whose upper surface is set higher than the water level at low tide, and on the vegetation base Characterized in that it comprises: a vegetation soil layer to be provided; a soil loss prevention means for preventing the soil of the vegetation soil layer from being washed away; and a fresh water supply means for supplying fresh water as a fresh water source to the vegetation soil layer. An aquatic vegetation zone in a body of water that is affected by salt water with tides.   2. The aquatic aquatic area affected by tidal salt water according to claim 1, wherein the fresh water supply means is a water conduit that guides fresh water from a fresh water source located higher than the vegetation base to the vegetation base. Plant belt.   The aquatic plant zone of a water area affected by tidal salt water according to claim 1, wherein the fresh water source is a reservoir.   The water area affected by the salt water is an estuary brackish water area, and the freshwater source is a river flowing into the brackish water area, and the waterway is higher than the water surface height at the high tide level of the estuary brackish water area. The aquatic plant in the water area affected by tidal salt water according to claim 2, characterized in that it has an inlet in the upstream part of the river, and the outlet is constituted by a pipe line facing the vegetation soil layer. band.   The water area affected by the salt water is an estuary brackish water area, and the freshwater source is a river flowing into the brackish water area, and the waterway has a water level higher than the water level at the low tide level of the estuary brackish water area. The water area affected by tidal salt water according to claim 2, characterized in that it has an introduction port in a river near the estuary as a place, and the discharge port is constituted by a pipeline facing the vegetation soil layer Aquatic plant zone. The aquatic plant zone in a water area affected by tidal salt water according to any one of claims 1 to 5, wherein the vegetation base is a water-permeable ground.

Images