CN105672459A - Low-elevation greenbelt for reducing urban initial-rainwater runoff pollution - Google Patents

Abstract

The invention discloses a concave green space for reducing urban rainwater runoff pollution at the initial stage, comprising: a concave green space, which is composed of a first block and a second block, the first block is horizontally laid with a packing layer, and aquatic plants are planted on the packing layer Vegetation; a plurality of water retaining walls inserted into a layer of fill with the bottoms of the water retaining walls flush with or extending beyond the lower surface of the fill layer and the tops of the water retaining walls flush with the upper surface of the fill layer Or extending out of its upper surface, an opening is provided on the water-retaining partition wall, a water-retaining partition wall is arranged at the junction of the first block and the second block, and the water-retaining partition wall located at the junction of the first block and the second block The wall and the second block and the inner wall of the concave green space form a reservoir; the catchment ditch is set on the outside of the concave green space, and the inner side of the catchment ditch is provided with a water inlet, and the water inlet is connected with the concave green space and the water catchment. ditch connected. The invention can effectively alleviate the hydraulic load of urban initial rainwater runoff pollution, thereby enhancing the ability of the concave green space to remove complex pollutants.

Description

Recessed green space to reduce urban stormwater runoff pollution

technical field

The invention relates to the field of urban primary rainwater runoff pollution control. More specifically, the present invention relates to a recessed green space that reduces urban primary stormwater runoff pollution.

Background technique

As urban rainwater runoff scours and engulfs a large amount of pollutants accumulated from the atmosphere and different urban underlying surfaces such as roofs, residential pavements, green spaces, and road pavements during the confluence process, it is directly discharged into the urban receiving water body without treatment , causing serious pollution of urban river and lake water systems, destroying the urban aquatic environment, and seriously affecting the daily life of residents around receiving water bodies. Rainwater runoff pollution is highly random, contingency, and widespread, and the pollution load varies greatly in time and space, making research, control, and treatment difficult. Non-point source pollution caused by rainwater runoff has become one of the important factors of urban water environment pollution.

At present, the development trend of domestic stormwater runoff management is to attach importance to the implementation of flood control and drainage, and gradually strengthen the research and application development of rainwater resource utilization and rainwater runoff pollution control technology, so as to promote the optimal allocation of urban rainwater resources and maintain the ecological balance of urban water cycle. Concave green space is a kind of green space rainwater regulation and storage technology. Compared with ordinary green space, concave green space fully stores rainwater by using the concave space, which significantly increases the rainwater infiltration time. It has the advantages of infiltrating rainwater, reducing peak flow and reducing surface runoff pollution.

The reduction of runoff pollution by concave green space is the result of the joint action of plant absorption and utilization, soil matrix adsorption and microbes in the matrix. The short hydraulic retention time leads to the reduction of COD, NH ₄ ⁺ -N and TP in the green space mainly depends on the physical action of the infiltration medium and the mechanical filtration and adsorption of the covering plants, while the degradation of microorganisms in the soil medium and the green space coverage The absorption and utilization of plants has not been fully utilized.

Contents of the invention

The purpose of the present invention is to provide a concave green space that reduces the pollution of urban initial rainwater runoff, which can reduce the hydraulic load of surface runoff on the concave green space, fully exert the biochemical effects of plants and soil microorganisms, and improve the ability to remove complex pollutants , realize the high-efficiency purification ability of the concave green space, make the urban surface runoff sewage stagnate and infiltrate after purification, and effectively solve the urban surface runoff pollution while replenishing groundwater.

In order to achieve these objects and other advantages according to the present invention, a kind of recessed green space for reducing urban initial rainwater runoff pollution is provided, including:

The concave green space is composed of a first block with a larger area and a second block with a smaller area, the first block is horizontally laid with a filler layer, and aquatic plants are planted on the filler layer;

A plurality of water-retaining partition walls are inserted into the packing layer at intervals along the vertical direction, the bottom of the water-retaining partition wall is flush with or extends beyond the lower surface of the packing layer, and the water-retaining wall The top of the partition wall is flush with or extends beyond the upper surface of the packing layer, and both sides of the water-retaining partition wall are fixedly connected with the inner sidewall of the concave green space to divide the packing layer into a plurality of purification areas, the upper part of the water retaining partition is provided with an opening, the lowest point of the opening is between the upper surface and the lower surface of the packing layer, the first block and the second A water-retaining partition wall is provided at the junction of the blocks, and the opening position on the water-retaining partition wall at the junction of the first block and the second block is higher than that of the second block. The water-retaining partition wall at the junction of one block and the second block forms a water reservoir with the second block and the inner wall of the concave green space;

A catchment ditch is arranged around the outer side of the concave green land, and at least one water inlet is arranged on the inner side of the water catchment ditch, and the water inlet is connected to the concave green land and the inside of the water catchment ditch, and The rainwater entering the concave green space from the water inlet all flows to the purification area farthest from the second block, and the height inside the bottom of the catchment ditch is not higher than the height outside the bottom of the catchment ditch. Height, the height of the lowest point of the water inlet is equal to the height inside the bottom of the catchment ditch, and not lower than the height of the top of the packing layer.

Preferably, in the recessed green space for reducing urban initial rainwater runoff pollution, the plurality of water-retaining partition walls are parallel to each other, and the openings on two adjacent water-retaining partition walls are arranged alternately left and right.

Preferably, in the concave green space for reducing urban initial rainwater runoff pollution, the at least one water inlet is a water inlet, and the water inlet and the openings on the water retaining partition wall opposite to it are arranged staggered left and right .

Preferably, in the concave green space for reducing urban initial rainwater runoff pollution, the filler layer is successively a gravel layer, a zeolite layer, a biological ceramsite layer and a gravel layer from bottom to top, and the thickness of each layer is 10mm .

Preferably, in the concave green space for reducing urban initial rainwater runoff pollution, the bottom and top of the water retaining partition wall are flush with the upper surface and the lower surface of the filling layer respectively, and the highest point of the opening flush with the upper surface of the packing layer, and the opening is arranged on one side of the water retaining partition wall.

Preferably, in the concave green space for reducing urban initial rainwater runoff pollution, the height inside the bottom of the catchment ditch is lower than the height outside the bottom of the catchment ditch, and the height of the bottom of the catchment ditch The slope is 2% to 8%.

Preferably, in the concave green space for reducing urban initial rainwater runoff pollution, a plurality of metal grids are vertically spaced at the water inlet, and the distance between the metal grids is 10mm.

Preferably, in the concave green space for reducing urban primary rainwater runoff pollution, an anti-seepage film is laid on the inner sidewall and bottom of the concave green space.

Preferably, in the recessed green space for reducing urban primary rainwater runoff pollution, the height of the highest point of the metal grid is lower than the height of the highest point of the water inlet.

Preferably, the concave green space for reducing urban initial rainwater runoff pollution also includes:

A backing plate, which is laid horizontally on the filling layer at a position opposite to the water inlet, the size of the backing plate is larger than the size of the water inlet, and one side of the backing plate is connected to the concave green space. The inner side wall is fixedly connected, and the curved surface on one side of the backing plate is attached to the inner side wall of the concave green space, and a plurality of first positioning holes are arranged at intervals along the vertical direction on the backing plate;

The bottom plate is horizontally laid on the backing plate, and a plurality of through holes are arranged at intervals on the bottom plate, the size of the bottom plate is the same as that of the backing plate, and there are many a second positioning hole, the first positioning hole and the second positioning hole have the same size and one-to-one correspondence;

A plurality of filter thorns are arranged at intervals on the upper surface of the bottom plate, the filter thorns are tapered, and the larger diameter end of the filter thorns is fixedly connected to the bottom plate, and is connected to the through hole and the The second positioning hole does not interfere, and the distance between the filter thorns is less than 10mm;

A plurality of pins, one pin is arranged in each of the first positioning holes and the corresponding second positioning holes.

The present invention at least includes the following beneficial effects:

In the present invention, the left and right staggered openings are arranged so that the runoff pollution forms a roundabout channel in the purification area, thereby reducing the hydraulic load of the rainwater runoff pollution in the concave green space, prolonging the hydraulic retention time, and fully exerting the biochemical effects of plants and soil microorganisms. Improve the ability to remove complex pollutants and realize the efficient purification ability of concave green space.

The invention plants aquatic plants on the filler layer, which not only has the effect of beautifying the landscape, but also can exert the effect of purifying the plants.

The present invention is provided with a metal grid at the water inlet, which can intercept large pollutants such as leaves, cigarette butts and domestic garbage, and perform primary filtration on the initial rainwater, because the height of the highest point of the metal grid is lower than the highest point of the water inlet When the later rainfall is large and the metal grid is partially blocked or completely blocked, the later rainwater can directly enter the concave green space from above the metal grid, which improves the stability of the concave green space.

In the present invention, a backing plate and a bottom plate are laid on the filling layer at the position opposite to the water inlet, and filter thorns are arranged on the bottom plate, and the rainwater entering the concave green space from the water inlet flows to the bottom plate, so that small pollutants are retained in the filter In the gaps between the thorns, the bottom plate and the filter thorns can also buffer the impact of rainwater and prevent rainwater from directly washing the packing layer.

Other advantages, objectives and features of the present invention will partly be embodied through the following descriptions, and partly will be understood by those skilled in the art through the study and practice of the present invention.

Description of drawings

Fig. 1 is the structural representation of recessed green land of the present invention;

Fig. 2 is the structural representation of packing layer and water-retaining partition wall according to the present invention;

Fig. 3 is a structural schematic diagram of a water retaining partition wall according to the present invention;

Fig. 4 is a schematic structural view of the water inlet according to the present invention;

Fig. 5 is a structural schematic diagram of the water inlet and the bottom plate of the present invention.

detailed description

The present invention will be further described in detail below in conjunction with the accompanying drawings, so that those skilled in the art can implement it with reference to the description.

It should be noted that, in the description of the present invention, the terms "horizontal", "vertical", "upper", "lower", "front", "rear", "left", "right", "vertical", The orientation or positional relationship indicated by "horizontal", "top", "bottom", "inner", "outer", etc. is based on the orientation or positional relationship shown in the drawings, and is only for the convenience of describing the present invention and simplifying the description, and It is not to indicate or imply that the device or element referred to must have a particular orientation, be constructed in a particular orientation, or operate in a particular orientation, and thus should not be construed as limiting the invention.

As shown in Figures 1 to 5, the present invention provides a concave green space 100 for reducing urban initial rainwater runoff pollution, including:

The concave green space 100 is composed of a first block with a larger area and a second block with a smaller area. A filler layer 110 is laid horizontally on the first block, and aquatic plants are planted on the filler layer 110; optional Plants that are resistant to drought and humidity and have high-efficiency purification effects, such as calamus and calamus, can not only beautify the landscape, but also play a role in plant purification.

A plurality of water-retaining partition walls 120 are inserted into the packing layer 110 at intervals along the vertical direction, and the bottom of the water-retaining partition wall 120 is flush with or extends beyond the lower surface of the packing layer 110 , The top of the water-retaining partition wall 120 is flush with or extends beyond the upper surface of the filler layer 110 , and both sides of the water-retaining partition wall 120 are fixedly connected to the inner side walls of the recessed green space 100 , to divide the packing layer 110 into a plurality of purification areas 111, the upper part of the water retaining partition wall 120 is provided with an opening 121, and the lowest point of the opening 121 is between the upper surface and the lower part of the packing layer 110 Between surfaces, when the top of the water retaining partition wall 120 extends beyond the upper surface of the packing layer 110, the highest point of the opening 121 can be higher than the upper surface of the packing layer 110, or lower than the upper surface of the packing layer 110, as long as the opening The lowest point of 121 is between the upper surface and the lower surface of the packing layer 110, then the rainwater must be able to flow from the upper-level purification area to the next-level purification area, and the junction of the first block and the second block A water-retaining partition wall 120 is provided, and the opening 121 on the water-retaining partition wall 120 at the junction of the first block and the second block is higher than the second block. The water retaining partition wall 120 at the junction of the block and the second block and the inner wall of the second block and the concave green space 100 enclose a reservoir 101;

Water catchment ditch 130, which is set around the outside of the concave green space 100, and at least one water inlet 131 is arranged on the inside of the water catchment ditch 130, and the water inlet 131 is connected with the concave green space 100 and the water catchment The interior of the ditch 130 is all connected, and the rainwater entering the concave green land 100 from the water inlet 131 flows to the purification area farthest from the second block, so that the rainwater can flow to the storage tank after being filtered step by step. In the pool 101, the height inside the bottom of the catchment ditch 130 is not higher than the height outside the bottom of the catchment ditch 130, and the height of the lowest point of the water inlet 131 is the same as the height inside the bottom of the catchment ditch 130. The heights are equal, and not lower than the height of the top of the packing layer 110, so that the rainwater in the gutter 130 can all flow into the concave green space 100, and first flow to the surface of the packing layer 110, and then gradually penetrate downwards And keep filtering. The inner side of the bottom of the catchment ditch 130 is the side close to the concave green space 100 , and the outer side of the bottom of the catchment ditch 130 is the side away from the concave green space 100 . Rainwater flows in the catchment ditch 130, because the height of the inside of the bottom of the catchment ditch 130 is not higher than the height of the outside of the bottom of the catchment ditch 130, that is, the level of the bottom of the catchment ditch 130, or the height of the inside of the bottom of the catchment ditch 130. Low, like this, rainwater can flow into the purification zone farthest away from the second block by the water inlet 131, that is, the first-level purification zone.

There are more pollutants in the initial rainwater and less rainfall. After the rainwater is circulated and filtered step by step from the first-level purification area to the second-adjacent purification area (the last-level purification area), the filtered rainwater passes through the The opening 121 on the water-retaining partition wall 120 at the junction of the first block and the second block flows into the reservoir 101, and the rainwater in the reservoir 101 can be used for garden irrigation and landscape water, and can also directly flow into the river or into groundwater. In the purification zone 111, fillers and aquatic plants can reduce pollutants through physical effects such as mechanical filtration and adsorption, and at the same time, the metabolism of plant roots and the biochemical effects of microorganisms can be fully exerted, and the synergistic effect of fillers-plants-microbes makes Incipient stormwater runoff pollution is effectively reduced.

There are fewer pollutants in the middle and late rainwater, and when the rainfall is also small, the filtering method is the same as that of the initial rainwater. Because the top of the water-retaining partition wall 120 is flush with the upper surface of the packing layer 110 or extends out of its upper surface, when the rainfall is large and the top of the water-retaining partition wall 120 is flush with the upper surface of the packing layer 110, excessive rainwater It can directly flow from the surface of the packing layer 110 to the reservoir 101; when the top of the water retaining partition wall 120 extends beyond the top of the packing layer 110, and the highest point of the opening 121 is lower than the upper surface of the packing layer 110, the water retaining The top of the partition wall 120 cannot extend too much, so as to prevent rainwater from flowing directly from the upper surface of the packing layer 110 to the reservoir 101 when the amount of rainfall is large. If there are too many upper surfaces, the rainwater will collect in the first-level purification area, and can only pass through the opening 121 to transition to the next-level purification area, or when the rainfall is very heavy, it will directly pass through the top of the water-retaining partition wall 120 to enter the next-level purification area; when the top of the water-retaining partition wall 120 extends beyond the top of the packing layer 110, and the water-retaining partition wall 120 is much higher than the packing layer 110, the highest point of the opening 121 can be set higher than the upper surface of the packing layer 110, In this way, rainwater can also flow directly from the upper surface of the packing layer 110 into the water storage tank 101 . Generally, in the actual construction process, from the perspective of cost saving, it is enough to set the top of the water-retaining partition wall 120 flush with the upper surface of the packing layer 110, but other forms can also achieve the purpose of the present invention, which belongs to the present invention scope of protection.

In the concave green space 100 for reducing the pollution caused by initial rainwater runoff in the city, the plurality of water retaining partition walls 120 are parallel to each other, and the openings 121 on two adjacent water retaining partition walls 120 are arranged alternately left and right. In this way, rainwater can flow from one side of the upper-level purification area to the other side, and then flow from the other side of the upper-level purification area to the next-level purification area, so that runoff pollution can form a roundabout channel in the purification area 111, thereby Reduce the hydraulic load of rainwater runoff pollution in the concave green space 100, prolong the hydraulic retention time, give full play to the biochemical effects of plants and soil microorganisms, improve the ability to remove complex pollutants, and realize the high-efficiency purification ability of the concave green space 100. The left and right staggered setting is based on the middle part of the water retaining partition wall as a reference point, facing the left and right sides seen by the water retaining partition wall.

In the concave green space 100 for reducing urban initial rainwater runoff pollution, the at least one water inlet 131 is a water inlet 131, and the water inlet 131 and the opening 121 on the water retaining partition wall 120 opposite to it are about Staggered settings. This can increase the residence time of rainwater in the first stage purification zone.

In the concave green space 100 for reducing urban initial rainwater runoff pollution, the filler layer 110 is successively composed of a gravel layer, a zeolite layer, a bioceramic layer and a gravel layer from bottom to top, and the thickness of each layer is 10 mm.

In the concave green space 100 for reducing the pollution of initial urban rainwater runoff, the bottom and top of the water retaining partition wall 120 are respectively flush with the upper surface and the lower surface of the filling layer 110, and the highest point of the opening 121 is The opening 121 is arranged on one side of the water-retaining partition wall 120 to be flush with the upper surface of the packing layer 110 . In this way, the packing layer 110 can be divided into a plurality of purification areas 111, and each purification area 111 can be connected through the opening 121, and the cost can also be saved.

In the concave green space 100 for reducing the pollution caused by initial rainwater runoff in the city, the height inside the bottom of the water catchment ditch 130 is lower than the height outside the bottom of the water catchment ditch 130, and the height of the bottom of the water catchment ditch 130 is The slope is 2% to 8%. Because the bottom of the catchment ditch 130 is provided with a slope, it is beneficial for rainwater to flow into the first-stage purification area through the water inlet 131. If the slope is too small, it is easy to cause a large amount of rainwater to collect in the catchment ditch 130 and cannot enter the first-stage purification area in time; If the slope is too large, when rainwater flows into the recessed green land 100 from the catchment ditch 130, it will not only impact the water inlet 131, but also impact the fillers and plants near the water inlet.

In the concave green space 100 for reducing the pollution caused by the initial rainwater runoff in the city, a plurality of metal grids 140 are arranged at intervals along the vertical direction at the water inlet 131, and the distance between the metal grids 140 is 10 mm. Pollutants such as leaves, cigarette butts and domestic garbage can be intercepted in this way, and the suspended solids and large particle pollutants in the initial urban rainwater runoff are deposited and filtered through the catchment ditch 130, which needs to be cleaned regularly. Other suspended matter etc. are degraded and adsorbed through the purification zone 111 .

In the concave green space 100 for reducing urban initial rainwater runoff pollution, the inner wall and bottom of the concave green space 100 are covered with anti-seepage membranes. The packing layer 110 is separated from the recessed green space 100, so that the treated sewage can be prevented from infiltrating and polluting the groundwater.

In the recessed green space 100 for reducing urban primary rainwater runoff pollution, the height of the highest point of the metal grid 140 is lower than the height of the highest point of the water inlet 131 . If the metal grid 140 is not cleaned in time, after being partially blocked or completely blocked, the later rainwater in the water catchment ditch 130 can flow into the recessed green space 100 through the part between the top of the metal grid 140 and the highest point of the water inlet 131 .

The recessed green space 100 for reducing urban initial rainwater runoff pollution also includes:

Backing plate 150, which is laid horizontally on the filler layer 110 at a position opposite to the water inlet 131, the size of the backing plate 150 is larger than the size of the water inlet 131, and one side of the backing plate 150 is connected to the water inlet 131. The inner side wall of the concave green space 100 is fixedly connected, and the curved surface on one side of the backing plate 150 is attached to the inner side wall of the concave green space 100. The backing plate 150 is vertically spaced with multiple a first positioning hole;

Bottom plate 160, which is laid horizontally on the backing plate 150, a plurality of through holes are arranged at intervals on the bottom plate 160, the size of the bottom plate 160 is the same as that of the backing plate 150, and the vertical edge of the bottom plate 160 is A plurality of second positioning holes 161 are arranged at intervals in the vertical direction, and the first positioning holes and the second positioning holes 161 have the same size and one-to-one correspondence;

A plurality of filter thorns 162 are arranged at intervals on the upper surface of the bottom plate 160, the filter thorns 162 are conical, and the larger diameter ends of the filter thorns 162 are fixedly connected to the bottom plate 160 and connected to the bottom plate 160. The through hole does not interfere with the second positioning hole 161, and the distance between the filter thorns 162 is less than 10 mm;

A plurality of pins, one pin is provided in each of the first positioning holes and the corresponding second positioning holes 161 . A backing plate 150 and a bottom plate 160 are laid on the filling layer 110 at a position opposite to the water inlet 131, and the bottom plate 160 is provided with filter thorns 162, so that the rainwater entering the concave green space 100 from the water inlet 131 flows to the bottom plate 160, so that Some pollutants are trapped in the gaps between the filter thorns 162 to further filter the rainwater, and the bottom plate 160 and the filter thorns 162 can also buffer the impact of the rainwater to prevent the rainwater from directly washing the packing layer 110 .

The bottom plate 160 can be fixed on the backing plate 150 through the bolt, thereby fixing the bottom plate 160. When the filter thorns 162 are full of pollutants and need to be cleaned, just pull out the bolt to remove the bottom plate 160. When cleaning, point the high-pressure water gun to the The lower surface of the bottom plate 160 can pass through the through holes to flush out the sundries between the filter thorns 162 . Also can filter thorn 162 downwards, take a twig at random, twig is inserted in the through hole, extract again, can poke out the sundry between filter thorn 162. Because the filter thorns 162 are cone-shaped, the gaps between the filter thorns 162 gradually increase from bottom to top, so pollutants of different sizes in the rainwater flowing in from the water inlet 131 can be intercepted, which is equivalent to setting a net from bottom to top. The multi-layer filter screen with gradually increasing pore size allows pollutants to continuously accumulate between the 162 filter thorns from bottom to top, which reduces the cleaning frequency. Even if the 162 filter thorns are all blocked by debris, the later rainwater can also flow into the concave green space 100 in.

Although the embodiment of the present invention has been disclosed as above, it is not limited to the use listed in the specification and implementation, it can be applied to various fields suitable for the present invention, and it can be easily understood by those skilled in the art Therefore, the invention is not limited to the specific details and examples shown and described herein without departing from the general concept defined by the claims and their equivalents.

Claims (10)

1. A concave green space for reducing urban initial rainwater runoff pollution, characterized in that it includes: The concave green space is composed of a first block with a larger area and a second block with a smaller area, the first block is horizontally laid with a filler layer, and aquatic plants are planted on the filler layer; A plurality of water-retaining partition walls are inserted into the packing layer at intervals along the vertical direction, the bottom of the water-retaining partition wall is flush with or extends beyond the lower surface of the packing layer, and the water-retaining wall The top of the partition wall is flush with or extends beyond the upper surface of the packing layer, and both sides of the water-retaining partition wall are fixedly connected with the inner sidewall of the concave green space to divide the packing layer into a plurality of purification areas, the upper part of the water retaining partition is provided with an opening, the lowest point of the opening is between the upper surface and the lower surface of the packing layer, the first block and the second A water-retaining partition wall is provided at the junction of the blocks, and the opening position on the water-retaining partition wall at the junction of the first block and the second block is higher than that of the second block. The water-retaining partition wall at the junction of one block and the second block forms a water reservoir with the second block and the inner wall of the concave green space; A catchment ditch is arranged around the outer side of the concave green land, and at least one water inlet is arranged on the inner side of the water catchment ditch, and the water inlet is connected to the concave green land and the inside of the water catchment ditch, and The rainwater entering the concave green space from the water inlet all flows to the purification area farthest from the second block, and the height inside the bottom of the catchment ditch is not higher than the height outside the bottom of the catchment ditch. Height, the height of the lowest point of the water inlet is equal to the height inside the bottom of the catchment ditch, and not lower than the height of the top of the packing layer. 2. The concave green space for reducing urban initial rainwater runoff pollution as claimed in claim 1, wherein the plurality of water-retaining partition walls are parallel to each other, and the openings on two adjacent water-retaining partition walls are staggered left and right set up. 3. The concave green space for reducing urban initial rainwater runoff pollution as claimed in claim 1, wherein the at least one water inlet is a water inlet, and the water inlet and the water retaining partition wall opposite thereto are The openings are arranged staggered left and right. 4. The concave green space for reducing urban initial rainwater runoff pollution as claimed in claim 1, wherein the filler layer is successively a gravel layer, a zeolite layer, a biological ceramsite layer and a gravel layer from bottom to top, and each layer The thickness is 10mm. 5. The concave green space for reducing urban initial rainwater runoff pollution as claimed in claim 2, wherein the bottom and the top of the water-retaining partition wall are respectively flush with the upper surface and the lower surface of the filler layer, so The highest point of the opening is flush with the upper surface of the packing layer, and the opening is arranged on one side of the water retaining partition wall. 6. The concave green space for reducing urban initial rainwater runoff pollution as claimed in claim 1, wherein the height inside the bottom of the catchment ditch is lower than the height outside the bottom of the catchment ditch, and the bottom of the catchment ditch The slope of the ditch bottom is 2% to 8%. 7. The recessed green space for reducing urban initial rainwater runoff pollution as claimed in claim 1, wherein the water inlet is vertically spaced with a plurality of metal grids, and the distance between the metal grids is 10mm. 8. The concave green space for reducing urban initial rainwater runoff pollution as claimed in claim 1, wherein an anti-seepage film is laid on the inner sidewall and the bottom of the concave green space. 9. The recessed green space for reducing urban initial rainwater runoff pollution according to claim 7, wherein the height of the highest point of the metal grid is lower than the height of the highest point of the water inlet. 10. The concave green space for reducing urban initial rainwater runoff pollution as claimed in claim 1, further comprising: A backing plate, which is laid horizontally on the filling layer at a position opposite to the water inlet, the size of the backing plate is larger than the size of the water inlet, and one side of the backing plate is connected to the concave green space. The inner side wall is fixedly connected, and the curved surface on one side of the backing plate is attached to the inner side wall of the concave green space, and a plurality of first positioning holes are arranged at intervals along the vertical direction on the backing plate; The bottom plate is horizontally laid on the backing plate, and a plurality of through holes are arranged at intervals on the bottom plate, the size of the bottom plate is the same as that of the backing plate, and there are many a second positioning hole, the first positioning hole and the second positioning hole have the same size and one-to-one correspondence; A plurality of filter thorns are arranged at intervals on the upper surface of the bottom plate, the filter thorns are tapered, and the larger diameter end of the filter thorns is fixedly connected to the bottom plate, and is connected to the through hole and the The second positioning hole does not interfere, and the distance between the filter thorns is less than 10mm; A plurality of pins, one pin is arranged in each of the first positioning holes and the corresponding second positioning holes.