Waterscape design in ecotype landscape design

Ecosystem refers to a certain space, the biological community and its environment formed by the interaction of the unity, any ecosystem is composed of biological and abiotic environment two major parts. The abiotic environment is the material, energy and living place on which organisms live in the ecosystem. It is the sum of all the environmental factors except organisms, including sunlight, air, water, soil and inorganic minerals. Wait.

    

     

The cycle of water movement in the biosphere is driven by solar energy and gravity. Oceans, lakes, rivers and surface waters evaporate constantly, forming water vapor into the atmosphere; water vapor absorbed by plants enters the atmosphere through transpiration of leaf surface is cooled, forming rain, snow, hail and other precipitation return to the earth's surface, part of which falls directly into the ocean, lakes and rivers and other waters, part of which falls to the earth's surface. On land, runoff forms on the surface and flows into the oceans, lakes, rivers, or underground for plant roots to absorb. The cycle of water is cyclic.

   With the rapid development of urban construction, a large number of buildings and roads make the impervious surface area of the city grow rapidly. Rainwater runoff will greatly increase, if we do not take measures and simply consider the rapid discharge of rainwater runoff, the capacity and transport capacity of rain pipelines, rain pumping stations and other facilities will be increased, which is a heavy burden for urban construction.

In addition, due to the enhancement of environmental awareness, it is recognized that the rapid discharge of rainwater from urban areas increases the flood hazards, riparian erosion and impact loads of pollutants received by the water bodies, and also causes difficulties in the operation of sewage treatment plants in the combined system and pollutes the water bodies due to the spillover of some rainwater and sewage mixtures. On the other hand, the guiding ideology was questioned.

On the one hand, the use of a huge rainwater drainage system to drain the growing runoff from the city, on the other hand, it is a serious shortage of urban groundwater supply. If the infiltration of rainwater is considered in the design of rainwater pipeline system, land use planning and ground cover, and the rainwater is reasonably and adequately utilized to conserve groundwater resources, the crisis of urban water resources can be alleviated, the water content in soil can be increased, and the climate can be adjusted, so as to improve the ecological environment of the city, and the required capacity of rainwater pipes can be reduced. Quantity, that is, reduce the investment and operation cost of rainwater pipe system, and reduce the risk of waterlogging and water pollution in urban areas. In fact, the infiltration of rain water has already been embodied in the buildings of some ancient cities in China. The infiltration pits, wells and ditches are used to make the rain water infiltrate underground.

On the one hand, the use of a huge rainwater drainage system to drain the growing runoff from the city, on the other hand, it is a serious shortage of urban groundwater supply. If the infiltration of rainwater is considered in the design of rainwater pipeline system, land use planning and ground cover, and the rainwater is reasonably and adequately utilized to conserve groundwater resources, the crisis of urban water resources can be alleviated, the water content in soil can be increased, and the climate can be adjusted, so as to improve the ecological environment of the city, and the required capacity of rainwater pipes can be reduced. Quantity, that is, reduce the investment and operation cost of rainwater pipe system, and reduce the risk of waterlogging and water pollution in urban areas. In fact, the infiltration of rain water has already been embodied in the buildings of some ancient cities in China. The infiltration pits, wells and ditches are used to make the rain water infiltrate underground.

As far as possible, reduce the pavement, retain natural raw soil, retain the existing vegetation and reduce surface runoff. Include:

(1) use centralized development to reduce road pavement.

(2) double load car parks, shared driving and turning lanes.

(3) minimize the width of road pavements as far as possible.

Setting up silt barrier during construction to avoid sediment loss

The siltation barrier should be set up before the start of the construction and maintained until the completion of the construction. All soil surfaces are covered with vegetation.

Minimize irrigation and use less herbicides, pesticides and fertilizers.

Maintaining grasslands and gardens in rehabilitated areas creates high concentrations of pesticides, nutrients and other pollutants.

Rainwater infiltration facilities

Using permeable paving materials

Permeable paving material is the most powerful tool for maintaining and restoring natural circulation. The most impermeable part of a typical development is not the building that people live in, but the hard pavement. Permeable vegetation surfaces, such as auxiliary parking lots and emergency lanes, are occasionally used on the ground of automobiles.

Permeable strong turf or hollow pavement lattices are made of concrete or plastics filled with topsoil or granules.

Surfaces of sidewalks, such as walkways and courtyards, are constructed with loose grains, wooden panels, or elaborately arranged paving stones.

The porous surface layer of porous asphalt consists of a "gradeless" granular material, and the voids between the large particles in the granular material are not filled with small particles. A stepless stone base maintains water until it penetrates the underlying soil. Compared with impermeable asphalt, porous asphalt is easier to drain, has better friction and appearance in a humid environment, and reduces glare and car noise.

In addition to the green area of infiltrated ground, artificial infiltrated ground is mainly divided into two categories, one is porous asphalt and porous concrete ground, the other is turf brick. They can be used for parking lots, less roads and sidewalks, especially for residential areas.

(1) porous asphalt and concrete floor

The typical porous asphalt surface structure is shown in Figure 2. Avoid the use of small aggregate surface asphalt layer, asphalt weight ratio of 5.5% ~ 6.0%, porosity of 12% ~ 16%, 6 ~ 7 cm thick. The asphalt layer consists of two layers of crushed stone, the upper layer of crushed stone diameter 1.3 cm, thickness 5 cm, the lower layer of crushed stone diameter 2.5-5 cm, porosity 38% - 40%, the thickness of which depends on the amount of water required, because it is mainly used to store rainwater and delay runoff.

Porous concrete ground structure is similar to porous asphalt ground, but the surface layer is replaced by sand-free concrete, its thickness is about 12.5 cm, porosity is 15% ~ 25%. Porous asphalt and porous concrete floors have been widely used in developed countries since 1973 when they were used in the United States. However, there are few reports in China.

(2) turf brick

Turf brick is a concrete block with various shapes of voids, the opening rate can reach 20% ~ 30%, because in the voids can be planted grass named. It was first used in Germany in 1961 and has been widely used both at home and abroad. Especially for urban parking lots, living quarters and roadside. It not only has the function of infiltrating rain water, but also has the effect of beautifying the environment.

Compared with porous asphalt and concrete ground, turf brick ground can purify rainwater runoff and regulate atmospheric temperature and humidity more effectively because of the growth of grass plants. Experiments show that it has certain removal effect on heavy metals such as lead, zinc and chromium. The leaves, stems and roots of plants can slow down runoff and prolong runoff time. The runoff coefficient of turf brick floor is between 0.05 and 0.35, which depends on the storage capacity of the gravel layer and the slope of the ground.

The cost of infiltration surface is about 10% higher than that of traditional impervious surface, but the total investment of rainwater system can be reduced by 12% ~ 38% considering the length and diameter of rainwater pipeline shortened due to the decrease of runoff and the prolongation of surface collecting time. It can also bring about greater environmental and social benefits.

Permeable pool

(1) ground penetrating tank

When land conditions are good and soil permeability is good, surface permeation tanks can be used. Pools can be large or small, or several small pools can be integrated use, depending on the terrain conditions, ground infiltration pools are seasonal water, such as several times a month, several times a year or spring water filling autumn dry up, water level changes greatly. Some of the ground infiltration pools are water all year round. Plants should be planted in the ground infiltration tank. Seasonal plants should be resistant to both drought and drought, depending on the water level in the ponds. Perennial surface infiltration ponds are similar to wetlands in land treatment systems. They are suitable for planting water-tolerant plants and phytoplankton. They can be used as habitats for wildlife and improve the ecological environment. Using natural low-lying land as ground penetrating tank is the most economical. If the bottom of the tank is treated simply, such as laying cobblestone and other permeable materials, its permeability will be greatly improved.

(2) underground infiltration tank

When the ground is short of land, we have to use the underground infiltration tank. In fact, it is a kind of underground water storage device, using gravel voids, perforated pipes, infiltration channels and other storage rainwater. For various types of underground seepage pools, the use of the bottom pervious canal can reduce the need for stone and increase the volume of water storage. In short, there are many kinds of underground permeable pools with different shapes.

(3) osmotic tube

The penetration pipe is usually made of perforated PVC pipe or made of permeable material. The collected rainwater passes through the permeable canal to enter the gravel layer around it.

  

Consider separating existing fallout and rainwater pipes from sewers to drain water from fallout pipes into depressions or gravel pits to facilitate infiltration, control and treat runoff from roofs and unavoidable impermeable pavement, and return it as far as possible to the natural diameter of the soil.

(1) the design of each drainage channels, ponds and drainage pit, with its special location and drainage area is consistent.

(2) the level of the water permeability surface runoff dispersing to nearby a vegetation soil, thus changing the central jet rainstorm flooding.

(3) transfer of concentrated runoff to vegetation depressions, rather than constructed drains or pipes. When exposed to runoff vegetation and porous soil, it decreases the volume and velocity, pollutant filtering. Compared with the construction of a closed system, the open drainage system can increase the diversity of vegetation, reduce the demand for irrigation water drainage and reduce the flow rate and the degree of erosion. In addition, it reduces the peak of flow and volume of runoff, increase water infiltration, for the wild animal habitat, represents the interaction with nature, and almost no maintenance.

(4) fixing soil to reduce the scour speed of water flow. It is very effective to install rocky or wooden dams, plant turf, erosion-resistant fibrous plants, and plant fast-rooting aquatic plants in unstable channels or in new low-lying areas that are easily eroded after leveling. The low-lying land at the bottom can reduce energy.

(5) the use of wetlands along the drainage channels and the construction of pools to achieve the current control of emissions. The pools and wetlands consist of a shallow pit, a low dam, and drainage from a water diversion flow. They can temporarily store rainstorms and improve water quality by static, filtration, and biodegradation of pollutants. Effective water treatment can be achieved by providing sufficient area for the water body and different depth of water for different plant growing areas and biophysical processes.

(1) use island and Peninsular to define the shape of the water body and expand the flow path and treatment effect.

(2) A series of pools and wetlands are set up along the drainage channels of a certain section, starting with some tiny ponds located at the top of the drainage area.

3. In a depression with a driveway, a small wetland is formed with a lane as a retaining dam.

(6) When constructing water bodies at the lowest part of the area, the drainage should be accurately calculated to prevent waterlogging, and the existing wetlands and shore buffer zones should be prevented as far as possible by constructing water bodies at the lower part of the area.

(7) The vegetation buffer zone around the parking lot can relieve oil and sediment on the parking lot and road surface.

The seepage basin is a closed depression on the ground, where water can only seep into the soil, and there is no way out. Infiltration is the best management and protection of runoff, because pollutants can be filtered out from the soil, flood and erosion can be alleviated downstream, and natural water can be supplied to groundwater and downstream water.

(1) design seepage basins according to open system or closed system. Some seepage basins are open and have vegetation. Vegetation maintains porous soil structure. Others are built below the ground using rubble of all sizes, and their surfaces are transformed into parking lots or other uses. Perforation pipes or prefabricated boxes are sometimes used to replenish the storage capacity of the seepage basin. Most underground basins have no access to the bottom for inspection and maintenance. Because of the high cost of materials used to construct groundwater basins, groundwater basins are preferred only when land is very tight and there is an urgent need to turn the surface into a dual-use basin.

(2) setting up a seepage basin near the source of runoff is most economical and effective.

(3) to avoid making the basin close to the foundation of the building, it should avoid being built on steep and unstable slopes.

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