CN104196277B - Functional rainwater garden suitable for interior of urban community grassy area in Shanghai - Google Patents

Abstract

The invention discloses a functional rainwater garden suitable for the interior of urban community green space in Shanghai, including pretreatment facilities, aquifers, seepage facilities and overflow facilities, wherein the pretreatment facilities include annular slopes and gravels, and annular slopes Located around the functional rain garden, the gravel is covered on the circular slope; the aquifer is the space formed by the horizontal enclosure of the circular slope and the bottom of the functional rain garden; the seepage facility is located at the bottom of the functional rain garden; the overflow Facilities include overflow pipes through the thickness of the aquifer and overflow drains at the base of functional rain gardens. The functional rainwater garden of the present invention, which is suitable for use in the green spaces of urban communities in Shanghai, can reduce the peak value of rainfall runoff, purify water quality, replenish groundwater, slow down municipal drainage pressure, improve microclimate, and enhance the livability of the city.

Description

A functional rain garden suitable for the interior of urban community green spaces in Shanghai

technical field

The invention relates to a functional rainwater garden, in particular to a functional rainwater garden suitable for the interior of Shanghai urban community green spaces, and belongs to the technical field of rainwater management.

Background technique

In recent years, the impact of the "rain island effect" and "turbid island effect" in Shanghai has been intensified, and the precipitation in the city has been significantly greater than that in the surrounding suburbs. According to statistics, the rainfall in the flood season from June to September in the Shanghai area in the past 30 years has been in Xujiahui, an urban area. It is nearly 1.5% more than Fengxian in the suburbs. In addition, with the acceleration of urbanization, the area of river courses in cities has been greatly reduced, and the underlying surfaces are mostly asphalt roads and cement roads, etc., which affect water infiltration. At present, my country's drainage standards are relatively low, and the drainage system is not perfect. All these factors are likely to cause runoff pollution and serious water accumulation. Compared with large-scale municipal drainage facilities renovation projects, using rain garden-related ecological stormwater management technologies to deal with rainfall runoff and runoff pollution will be more economical, beautiful and feasible, and the effect of in-situ water retention will be more significant.

The groundwater table in Shanghai is high, and the buried depth of shallow groundwater is generally 0.5-1.0m. According to the research on the pollution characteristics of non-permeable surface runoff in Shanghai, the median concentration of runoff events is: COD205mg/L, BOD568mg/L, SS185mg/L, NH4+～N3.14mg/L, TP0.40mg/L, TN7 .23mg/L, the pollution level is much higher than that of foreign countries. In addition, the soil in the Shanghai area is a cohesive soil with a small permeability coefficient. In view of the special status quo of high groundwater level, heavy surface runoff pollution, and high soil viscosity in Shanghai, it is necessary to construct a functional rain garden suitable for the interior of urban community green spaces in Shanghai. The pretreatment facilities, aquifers, Covering layer, planting layer, transition layer, filling layer, drainage layer, seepage facilities and overflow facilities are designed in detail to ensure that the rain garden can better intercept, store, filter, absorb and purify rainfall runoff And other functions, and make it better connected with the municipal drainage pipe network, so as to effectively reduce the peak rainfall runoff, purify water quality, replenish groundwater, reduce municipal drainage pressure, improve microclimate, and enhance the livability of the city.

After searching the existing technology, it is found that the utility model patent with the patent number of 201320386006.8 discloses a rain garden system suitable for sandy runoff in mountainous cities. The patent includes a rain garden and a sand-water separation system, which can separate mud and sand in the runoff and rainwater, reducing mud and sand from entering the rain garden; the invention patent with the patent number of 201110001511.1 discloses a test device for the permeability coefficient of the rain garden filler. Texture, permeability parameters of fillers with different buried depths. In addition, Wang Shufen, Yang Le, and Bai Weilan wrote in "The Perfect Unity of Technology and Art—A Study on the Construction of Rain Gardens" (Chinese Garden, 2009, June), Xiang Lu, Li Junqi, and Kuang Nuo in "A Study of Rain Garden Design Methods" (Water and Drainage . Science, 2011, 39) all talked about the development background, successful case analysis, landscape application and design points of rain gardens, etc., but they were all limited to the qualitative description of rain gardens and suggestions for their domestic development. None of the above-mentioned patents and documents relate to specific methods and structural parameters for constructing rain gardens inside urban community green spaces.

Contents of the invention

In view of the above-mentioned defects of the prior art, the technical problem to be solved by the present invention is to provide a suitable for reducing the peak value of rainfall runoff, purifying water quality, supplementing groundwater, alleviating municipal drainage pressure, improving the microclimate, and enhancing the livability of the city. A functional rain garden inside the urban community green space in Shanghai.

In order to achieve the above object, the present invention provides a functional rain garden suitable for use in Shanghai urban community green space, the functional rain garden is located in the community green space, the structure of the functional rain garden includes pretreatment facilities, water storage layers, seepage facilities and overflow facilities, wherein the pretreatment facilities include a circular slope and gravel, the circular slope is located at the periphery of the functional rain garden, and the gravel is covered on the circular slope; The aquifer is the space formed by the horizontal enclosure between the annular slope and the bottom of the functional rain garden; the seepage facility is located at the bottom of the functional rain garden; the overflow facility includes The overflow pipe in the thickness direction of the aquifer and the overflow drain pipe located at the bottom of the functional rain garden, the overflow pipe is connected with the overflow drain pipe.

Further, a covering layer, a planting layer, a transition layer, a filling layer and a drainage layer are sequentially arranged along the thickness direction of the aquifer, and the drainage layer is located at the bottom of the functional rain garden.

Further, the covering layer is paved with fine stones, the thickness of the covering layer is 5 cm, and the particle size of the fine stones is 1-2 cm.

Further, the planting layer includes formula soil and vegetation planted in the formula soil, the formula soil is uniformly mixed with 60% garden planting soil and 40% medium sand, and the thickness of the formula soil is 25-50cm; the vegetation is a perennial herb or shrub with moisture and drought tolerance, and the height of the vegetation is 25-75cm.

Further, the transition layer is paved with medium sand, the thickness of the transition layer is 5-10 cm, and the particle size of the medium sand is 0.35-0.5 mm.

Further, the filler layer is laid by block bricks, the thickness of the filler layer is 25-35 cm, and the particle size of the block bricks is 3-5 cm.

Further, the water seepage facility is composed of a water seepage pipe and a water seepage drainage pipe; the water seepage pipe is located at the bottom of the drainage layer, the diameter of the water seepage pipe is 12-18 cm, and the outside of the water seepage pipe is wrapped with 1~ Two layers of geotextiles are tied tightly with strings; the seepage pipe and the seepage drainage pipe are connected.

Further, the seepage drainage pipe has a slope of 1-3%, the higher end of the seepage drainage pipe communicates with the seepage pipe, and the lower end communicates with a nearby branch drainage pipe or rainwater well.

Further, the overflow pipe has an overflow port, and a honeycomb baffle with a pore size of 1 to 2 cm is installed on the overflow port, and the honeycomb baffle is 12 to 17 cm higher than the aquifer, lower than the aquifer. The diameter of the overflow pipe is 12-17 cm in the surrounding community green space of 3 cm.

Further, the overflow drain pipe has a slope of 1-3%, the higher end of the overflow drain pipe communicates with the overflow pipe, and the lower end communicates with a nearby drainage branch pipe or rainwater well.

Further, the functional rain garden has an area of 10-40m ² , an aspect ratio of 1.5-2:1, and a structural thickness of 105-160cm.

Further, the circular slope is located at the intersection of the functional rain garden and the community green space, the slope of the circular slope is 30-35°, and the width is 43-67cm.

Further, the gravel has a thickness of 8-12 cm and a particle size of 5-8 cm.

Further, the bottom of the aquifer is recessed 15-20 cm downwards compared to the community green space.

The functional rainwater garden of the present invention, which is suitable for use in the green spaces of urban communities in Shanghai, can reduce the peak value of rainfall runoff, purify water quality, replenish groundwater, slow down municipal drainage pressure, improve microclimate, and enhance the livability of the city.

The idea, specific structure and technical effects of the present invention will be further described below in conjunction with the accompanying drawings, so as to fully understand the purpose, features and effects of the present invention.

Description of drawings

Fig. 1 is the principle structural sectional view of the functional rainwater garden that is applicable to Shanghai urban community green land of a preferred embodiment of the present invention;

Fig. 2 is the schematic structural plan view of the functional rain garden applicable to the interior of Shanghai urban community green space according to a preferred embodiment of the present invention;

Fig. 3 is the sectional view of the principle structure of the functional rain garden that is applicable to the interior of Shanghai urban community green space of embodiment 1;

Fig. 4 is the principle structural plan view of the functional rainwater garden applicable to the interior of Shanghai urban community green space of embodiment 1;

Fig. 5 is the sectional view of the principle structure of the functional rain garden applicable to the interior of Shanghai urban community green space of embodiment 2;

Fig. 6 is a plan view of the principle structure of the functional rain garden applicable to the interior of Shanghai urban community green space according to embodiment 2.

detailed description

As shown in Figures 1 to 2, a preferred embodiment of the present invention provides a functional rain garden 1 suitable for the interior of Shanghai urban community green space. 40m ² , the aspect ratio is 1.5-2:1, and the structural thickness is 105-160cm. Its structure includes pretreatment facility 2, aquifer 3, seepage facility 9 and overflow facility. Arrow 18 in Figures 1 and 2 indicates the direction of flow of rainfall runoff.

Among them, the pretreatment facility 2 includes a circular slope and gravel covered on the circular slope. The circular slope is located at the junction of the functional rainwater garden 1 and the community green space 14. The slope of the circular slope is 30-35° and the width is 43-67cm, the thickness of the gravel is 8-12cm, and the particle size is 5-8cm.

The aquifer 3 is a space formed by the horizontal enclosure of the circular slope and the bottom of the functional rain garden, and the bottom of the aquifer 3 is 15-20cm lower than the community green space.

A covering layer 4 , a planting layer 5 , a transition layer 6 , a filling layer 7 and a drainage layer 8 are sequentially arranged along the thickness direction of the aquifer 3 , and the drainage layer 8 is located at the bottom of the functional rain garden 1 . The covering layer 4 is paved with fine stones, the thickness of the covering layer 4 is 5 cm, and the particle size of the fine stones is 1-2 cm. The planting layer 5 includes the formula soil and the vegetation 11 planted in the formula soil. The formula soil is uniformly mixed with 60% garden planting soil and 40% medium sand. The thickness of the formula soil is 25-50cm; and drought-tolerant perennial herbs or shrubs, the height of vegetation 11 is 25-75cm. The transition layer 6 is paved with medium sand, the thickness of the transition layer 6 is 5-10 cm, and the particle size of the medium sand is 0.35-0.5 mm. The filler layer 7 is laid by block bricks, the thickness of the filler layer 7 is 25-35 cm, and the particle size of the block bricks is 3-5 cm.

The seepage facility 9 is located at the bottom of the drainage layer 8 and is composed of a seepage pipe 15 and a seepage drain pipe 12 . The pipe diameter of seepage pipe 15 is 12～18cm, and the outside of seepage pipe 15 is wrapped with 1～2 layers of geotextiles, and is fastened with string. The seepage drainage pipe 12 has a slope of 1-3%. The higher end of the seepage drainage pipe 12 communicates with the seepage pipe 15, and the lower end communicates with the nearby drainage branch pipe 16 or rainwater well 17.

The overflow facility includes an overflow pipe 19 running through the thickness direction of the aquifer and an overflow drain pipe 13 located at the bottom of the functional rain garden 1 . The overflow pipe 19 has an overflow port 10 on which a honeycomb baffle 20 with a pore size of 1-2 cm is installed. Green land 14 is 3cm low, and the pipe diameter of overflow pipe 19 is 12～18cm. The overflow drain pipe 13 has a slope of 1-3%. The higher end of the overflow drain pipe 13 communicates with the overflow pipe 19 , and the lower end communicates with the nearby drainage branch pipe 16 or rainwater well 17 .

The working principle of the functional rainwater garden suitable for the interior of Shanghai urban community green space of the preferred embodiment of the present invention is as follows:

(1) When rainfall occurs, the rainfall runoff collected by the community green space 14 will flow into the functional rain garden 1 due to gravity, and after buffering and preliminary filtering by the pretreatment facility 2, it will enter the aquifer 3, and then flow into the aquifer 3. After the aboveground part of the vegetation 11 is blocked and preliminarily purified, most of the rainfall runoff infiltrates, and the infiltrating water body passes through the covering layer 4, the planting layer 5, the transition layer 6, the filling layer 7 and the drainage layer 8 in sequence, and the rainfall runoff is in the During the infiltration process, after the precipitation, adsorption, ion exchange, denitrification, biofilm oxidation, and absorption of nitrogen and phosphorus by plant roots in the above-mentioned structural layer, the purpose of reducing runoff pollution and rainfall runoff can be achieved.

(2) When the rainfall is less than 29.9mm/12h, the rainfall runoff flows into the functional rain garden 1, and the collected rainfall runoff is held in the structural layer, and flows through the covering layer 4, the planting layer 5, and the transition layer 6 in sequence , the filler layer 7 and the drainage layer 8, after slowly infiltrating layer by layer, are used to supplement the soil moisture of the surrounding community green space 14, and the runoff that continues to infiltrate will replenish groundwater, realizing the full absorption and purification of rainfall runoff.

(3) When the rainfall is 30-139.9mm/12h, the rainfall runoff flows into the functional rain garden 1, and the collected rainfall runoff passes through the structural layer of the rain garden, that is, it flows through the covering layer 4, the planting layer 5, and the transition layer in sequence 6. After the filler layer 7 and the drainage layer 8 infiltrate slowly layer by layer, part of the purified water body is used to supplement the surrounding soil moisture and groundwater, and the other part of the water body that is too late to infiltrate is discharged into the municipal drainage pipe network through the seepage facility, which can Cut 70-80% of runoff and remove 70-90% of total pollutants.

(4) When the rainfall is greater than 140mm/12h, after the initial rainfall runoff with high pollutant concentration is intercepted, filtered and purified by the functional rain garden 1, more than 70% of the total pollutants can be removed, and the flood peak can be delayed by 40~ 60 minutes; when the infiltration speed of the rainfall runoff in the rain garden system is lower than the inflow speed of the rainfall runoff, the system will gradually accumulate water to the height of the overflow port 10, and the rainfall runoff will quickly enter the overflow pipe from the overflow port 10 19, and then directly discharged to the municipal drainage pipe, while the accumulated water in the functional rain garden 1 that does not reach the height of the overflow 10 still continues to infiltrate, which can alleviate the municipal drainage pressure to a certain extent and reduce the surrounding accumulated water.

Example 1:

A functional rainwater garden 21 is set up in the green space between the model houses in the southern part of the landscape demonstration area of the villa area in Xiangcheng District, Suzhou Greenland, to collect the runoff generated in the green space 22 . As shown in Figures 3 and 4, the functional rain garden 21 has an area of 12m ² , a kidney shape, a bottom length of 4.8m, a width of 2.5m, and a structure thickness of 105cm. The arrow 40 in Figures 3 and 4 The direction of flow of rainfall runoff is given.

The structure of the functional rain garden 21 includes a pretreatment facility 23, an aquifer 24, an infiltration facility 25 and an overflow facility.

Wherein, the pretreatment facility 23 includes a circular slope and gravel covered on the circular slope. The circular slope is located at the junction of the functional rain garden 21 and the green space 22. The slope of the circular slope is 35°, the width is 43cm, and the gravel The thickness is 8cm and the particle size is 5cm.

The aquifer 24 is a space formed by the horizontal enclosure of the circular slope and the bottom of the functional rain garden 21 .

A covering layer 26 , a planting layer 27 , a transition layer 28 , a filling layer 29 and a drainage layer 30 are arranged in sequence along the thickness direction of the aquifer 24 , and the drainage layer 30 is located at the bottom of the functional rain garden 21 . The covering layer 26 is paved with fine stones, the thickness of the covering layer 26 is 5 cm, and the particle size of the fine stones is 1 cm. The planting layer 27 comprises formula soil and the vegetation 31 planted in the formula soil, and the formula soil is formed by uniformly mixing 60% garden planting soil and 40% medium sand, and the thickness of the formula soil is 25cm; Ophiopogon japonicus. The transition layer 28 is made of medium sand with a particle size of 0.5 mm, and its thickness is 5 cm. The filler layer 29 is laid by block bricks with a particle size of 3 cm, and the thickness of the filler layer 29 is 25 cm.

The seepage facility 25 is located at the bottom of the drainage layer 50 and is composed of a seepage pipe 32 and a water seepage drain pipe 33 . The pipe diameter of seepage pipe 32 is 12cm, and the outside of seepage pipe 32 is wrapped with 1 layer of geotextiles, and fastens with string. The seepage drainage pipe 33 has a slope of 3%. The higher end of the seepage drainage pipe 33 communicates with the seepage pipe 32 , and the lower end communicates with the nearby drainage branch pipe 34 or rainwater well 35 .

The overflow facility includes an overflow pipe 36 running through the thickness direction of the aquifer 24 and an overflow drain pipe 37 at the bottom of the functional rain garden 21 . The overflow pipe 36 has an overflow port 38, and the overflow port 38 is equipped with a honeycomb baffle 39 with a pore size of 1 cm. The honeycomb baffle 39 is 12 cm higher than the water storage layer 24 and 3 cm lower than the surrounding green space 22. The pipe diameter of overflow pipe 36 is 12cm. The overflow drain pipe 37 has a slope of 3%. The higher end of the overflow drain pipe 37 communicates with the overflow pipe 36, and the lower end communicates with the nearby drainage branch pipe 34 or rainwater well 35.

According to the design of the above structural parameters, the rain garden can effectively purify and treat about 80m ³ of rainfall runoff under heavy rain intensity (12h rainfall less than 29.9mm) every year, and deal with heavy rain intensity (12h rainfall greater than 30mm) with the highest concentration of pollutants The initial rainfall runoff is about 48m ³ , the reduction rate of TSS is about 90%, the reduction rate of COD is about 60%, the reduction rate of TP is about 80%, and the reduction rate of TN is about 65%. At the same time, this rain garden saves about 20 tons of irrigation water for the green space every year.

Example 2:

A functional rainwater garden 41 is set up in the green space among high-rise residential buildings in Shenghui Community, Baoshan Green Sea Area, Shanghai, to collect the runoff generated in the green space 42 . As shown in Figures 5 and 6, the functional rain garden 41 has an area of 39m ² , a kidney shape, a bottom length of 8.5m, a width of 4.6m, and a structure thickness of 160cm. The arrow 60 in Figures 5 and 6 The direction of flow of rainfall runoff is given.

The structure of the functional rain garden 41 includes a pretreatment facility 43, an aquifer 44, an infiltration facility 45 and an overflow facility.

Wherein, the pretreatment facility 43 includes a circular slope and gravel covered on the circular slope, the circular slope is located at the junction of the functional rain garden and the green space 42, the slope of the circular slope is 30°, and the width is 67cm. The thickness is 12cm, and the particle size is 8cm.

The water storage layer 44 is a space formed by the horizontal enclosure of the circular slope and the bottom of the functional rain garden 41 .

A cover layer 46 , a planting layer 47 , a transition layer 48 , a filler layer 49 and a drainage layer 50 are arranged in sequence along the thickness direction of the water storage layer 44 . The drainage layer 50 is located at the bottom of the functional rain garden 41 . The covering layer 46 is paved with fine stones, the thickness of the covering layer 46 is 5 cm, and the particle size of the fine stones is 1 cm. The planting layer 47 includes the formula soil and the vegetation 51 planted in the formula soil. The formula soil is uniformly mixed with 60% garden planting soil and 40% medium sand. The thickness of the formula soil is 50cm; the vegetation 51 is a leaflet with a height of 65cm gardenia. The transition layer 48 is made of medium sand with a particle size of 0.5mm, and its thickness is 10cm. The filler layer 49 is laid by block bricks with a particle size of 3 cm, and the thickness of the filler layer 49 is 35 cm.

The seepage facility 45 is located at the bottom of the drainage layer 50 and is composed of a seepage pipe 52 and a water seepage drain pipe 53 . The pipe diameter of seepage pipe 52 is 18cm, and the outside of seepage pipe 52 is wrapped with 2 layers of geotextiles, and fastens with string. The seepage drainage pipe 53 has a slope of 1%. The higher end of the seepage drainage pipe 53 communicates with the seepage pipe 52 , and the lower end communicates with the nearby drainage branch pipe 54 or rainwater well 55 .

The overflow facility includes an overflow pipe 56 running through the thickness direction of the aquifer 44 and an overflow drain pipe 57 located at the bottom of the functional rain garden 41 . The overflow pipe 56 has an overflow port 58, and a honeycomb baffle 59 with a pore size of 2 cm is installed on the overflow port 58. The honeycomb baffle 59 is 17 cm higher than the water storage layer 44 and 3 cm lower than the surrounding green space. The diameter of the flow tube 56 is 18 cm. The overflow drain pipe 57 has a slope of 1%. The higher end of the overflow drain pipe 57 communicates with the overflow pipe 56 , and the lower end communicates with the nearby drainage branch pipe 54 or rainwater well 55 .

According to the design of the above structural parameters, the rain garden can effectively purify and treat about 310m ³ of rainfall runoff under heavy rain intensity (12h rainfall less than 29.9mm) every year, and deal with heavy rain intensity (12h rainfall greater than 30mm) with the highest concentration of pollutants The initial rainfall runoff is about 190m ³ , the reduction rate of TSS is about 90%, the reduction rate of COD is about 80%, the reduction rate of TP is about 90%, and the reduction rate of TN is about 75%. At the same time, this rain garden saves about 78 tons of irrigation water for the green space every year.

The preferred specific embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make many modifications and changes according to the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning or limited experiments on the basis of the prior art shall be within the scope of protection defined by the claims.

Claims (5)

1. A functional rain garden suitable for Shanghai urban community green space, characterized in that, the functional rain garden is located in the community green space, and the structure of the functional rain garden comprises a pretreatment facility, an aquifer, a seepage facilities and overflow facilities, wherein, the pretreatment facility includes an annular slope and gravel, the annular slope is located at the periphery of the functional rain garden, and the gravel is covered on the annular slope; the annular The slope of the slope is 30-35°, and the width is 43-67cm; the thickness of the gravel is 8-12cm, and the particle size is 5-8cm; the aquifer is the annular slope and the functional rainwater The space formed by the horizontal enclosure of the bottom of the garden; the bottom of the aquifer is recessed 15-20cm downwards compared to the community green space; the seepage facility is located at the bottom of the functional rain garden; the overflow The facilities include an overflow pipe running through the thickness direction of the aquifer and an overflow drain pipe located at the bottom of the functional rain garden, and the overflow pipe is communicated with the overflow drain pipe; along the The thickness direction of the aquifer is provided with a cover layer, a planting layer, a transition layer, a filler layer and a drainage layer in sequence, and the drainage layer is located at the bottom of the functional rain garden; the cover layer is paved with fine stones, so The thickness of the covering layer is 5cm, and the particle size of the fine stone is 1-2cm; the planting layer includes the formula soil and the vegetation planted in the formula soil, and the formula soil is composed of 60% garden planting soil and 40% medium sand is uniformly mixed, and the thickness of the formula soil is 25-50cm; the vegetation is a perennial herb or shrub with moisture and drought tolerance, and the height of the vegetation is 25-75cm; the transition The layer is made of medium sand, the thickness of the transition layer is 5-10cm, and the particle size of the medium sand is 0.35-0.5mm; the filler layer is made of block bricks, and the thickness of the filler layer is The particle size of the block brick is 3-5cm; the area of the functional rain garden is 10-40m ² , the aspect ratio is 1.5-2:1, and the structure thickness is 105-160cm. 2. The functional rain garden according to claim 1, wherein the seepage facility is composed of a seepage pipe and a seepage drainage pipe; the seepage pipe is located at the bottom of the drainage layer, and the diameter of the seepage pipe is 12-18cm, the outside of the seepage pipe is wrapped with 1-2 layers of geotextile, and tied tightly with a string; the seepage pipe and the seepage drainage pipe are connected. 3. The functional rain garden according to claim 2, wherein the seepage drainage pipe has a slope of 1 to 3%, and the higher end of the seepage drainage pipe communicates with the seepage pipe, and the lower One end of the pipe is connected to a nearby branch drainage pipe or rainwater well. 4. The functional rainwater garden according to claim 1, wherein the overflow pipe has an overflow port, and a honeycomb baffle with a pore size of 1 to 2 cm is installed on the overflow port, and the honeycomb The type baffle is 12-17cm higher than the aquifer, and 3cm lower than the surrounding community green space, and the diameter of the overflow pipe is 12-17cm. 5. The functional rain garden according to claim 1, wherein the overflow drain pipe has a slope of 1 to 3%, and the higher end of the overflow drain pipe communicates with the overflow pipe , and the lower end communicates with a nearby drainage branch or stormwater well.