FINAL RAIN GARDEN INDIVIDUAL STUDY PROJECT

R A I N

G A R D E N S

“Water is the precious life substance of the earth. Its value to the environment, climate and life of our world will be increasingly recognised. Violated, humiliated, piped, contaminated, less and less can it unfold its selfless qualities and perform its life-supporting task.

Awareness, care and perceptive consciousness are being asked of humanity.�

Wolfgang Geiger and Herbert Dreiseitl [1995].

Marta Derska Maria Plesniak

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TABLE OF CONTENTS 1. Abstract 2. Introduction 3. Objective 4. Methods and Materials 5. Results 5.1. Potential of using rain gardens for reducing the run off 5.2. Potential of using rain gardens for controlling water quality 5.3. Potential of rain gardens for creating an attractive environment 5.4. Rain garden variations 5.4.1. Rain garden for residential areas 5.4.2.

Rain

garden/bioretention

area

for

parking

space

and

for

industrial/business areas 5.5. Plants suitable for rain gardens 5.6. Rain garden projects

5.6.1.

Single family house

5.6.2.

Multi-storage residential house

6. Discussion 7. Conclusions 8. Literature

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1. Abstract Onsite water management is a pro ecological alternative to using the stormwater drains. Capturing stormwater during a storm and holding it on the side has many economical and environmental advantages.

Rain garden is a simple and efficient tool to achieve such goal. It is intentional low area where runoff water from impervious surfaces is diverted and contained so that the runoff infiltrates into the soil instead of going to the drain system.

Rain gardens are sustainable development features. Sustainable development is a socioecological process characterized by the fulfillment of human needs while maintaining the quality of the natural environment indefinitely.

Project objective will be supported with two examples of rain gardens designed in different scales and different contexts.

2. Introduction1,2 In traditional stormwater management, water is typically moved off from the site as quickly as possible to a centralized facility. Low impact development (LID) takes a lot-level approach to stormwater management, treating rainwater where it falls by creating conditions that allow the water to infiltrate back into the ground. Essentially LID attempts to model nature through ecofriendly terms like infiltrating, storing, filter, evaporating, and detaining runoff. Rain gardens are one of the low impact development solutions incorporated into residential and commercial properties.

The increasing water demands worldwide, rising costs of urban drainage, mandatory restrictions and water quality concerns are the problems that urban water management has to deal with in order to conserve and protect water resources and the function of the city.

Rain gardens are most often a feature in a residential or small landscape. The purpose of a rain garden is to create a more natural flow keeping stormwater on site to infiltrate and reducing the amount of stormwater that runs into streets and storm drains. A rain garden collects stormwater runoff and filter it through soil and plant roots. The plants in the rain gardens are designed to be an attractive landscape feature.

1 2

Seymour R. M., Capturing rainwater to replace irrigation water for landscapes: rain harvesting and rain gardens.

Mary C. H., Low-Impact Development, The Journal for Surface Water Quality Professionals ‘Stormwater Features’.

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Bioretention areas serve a similar function to rain gardens but tend to be located in larger commercial landscaped settings. They collect rainwater from roofs of commercial buildings and\or parking lots. In bioretention area more stress should be applied on water quality because of higher pollution pressure. Bioretention areas provide treatment by adsorbing metals and phosphorus in organic matter, biomass and soil, by killing harmful pathogens and by reducing sediments and nitrogen as captured stormwater infiltrates.

These two alternatives for landscape water supply are wining strategies that can be used in both commercial and residential site design to improve water quality and reduce the need for potable water use in landscape irrigation. The aim of this project is to increase knowledge about the importance of onsite water management. Project objective will be supported with two examples of rain gardens designed in different scales and purposes.

3. Objective The aim of this assignment is to describe the potential of using rain gardens for reducing the run off, ensuring high water quality, harvesting rain and creating attractive environments. Keeping dialogue with people will be emphasised. The focus will be on residential areas, parking space and industrial/business areas.

In addition the authors will design two specific rain gardens as an example of alternative water management in residential areas. Gardens will be designed for alternative climate conditions (Poland and Denmark).

4. Methods and Materials Literature survey - peer-reviewed publications, conference materials, books, manuals, and websites will be used to present the results.

The study of the above will be applied to the projects of rain garden for two specific sites.

5. Results 5.1. Potential of using rain gardens for reducing the run off3 The project will focus on how to prevent stormwater runoff using the rain garden and bioretention as the key-solution to onsite water management.

Any technique that soaks water into the ground makes water available for evapotranspiration, stores water for re-use or diverts stormwater away from the drainage system can be considered as a volume reduction practise.

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Dunnett N., Clayden A. Rain Gardens - Managing water sustainably in the garden and designed landscape; Timber Press 2007

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Volume reduction techniques:

•

Infiltration - process of soaking water into the ground

•

Evapotranspiration - the combined process of evaporating and transpiring

•

Storage - collecting water in rain barrels, cisterns and other containers (pools, ponds, etc.)

•

Conveyance - process which prolongs water transportation time through various facilities and allow to transpire or soak it into the ground (channels, linear depressions, swales and other tracks)

The aim of this project is focused on rain garden as a feature itself, however it is very important to acknowledge that it can be incorporated with other elements of bigger system which is called stormwater chain. Combining two or more elements together will multiply beneficial effects of reducing the run-off, what is the major objective of Low Impact Development. Designing new rain garden should be followed with the site analysis focused on looking for possibility of developing linked elements. Rain garden chain can include following features: •

Green roof – because roofs represent approximately 50 per cent of the impermeable surfaces in urban areas it makes them a potentially major role player in reducing the amount of rainwater rushing off the surfaces. The storage capacity of green roof varies with the season of the year, the depth and type of substrate, the angle of slope of the roof, the type of plants incorporated in the roof and many other factors. However, most studies agree that yearly reductions in run-off reach as much as 60 per cent.

•

Rain barrels and water butts – the features which enable harvesting, storage and reuse of the rain water. (photo)

•

Outflows and gullies. The outflow is the point at which water leaves downspout. The gully is a shallow channel set within the pavement and it aim is to transport the water across the impermeable surface before releasing it into rain garden.

•

Stormwater planters – above-ground planting containers that intercept water from the roof. They help to reduce run-off through infiltration, evaporation, transpiration and storage.

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Figure 1: Components of rain garden chain •

Landscape swales – vegetated channels and linear depressions which temporarily store and move run-off water. Swales are most effective solutions for commercial developments and along the car parks, streets and highways

•

Filter strips – gently slopping vegetated areas – designed to slow down the rate of flow and trap sediments and pollutants

•

Retention ponds – impermeable basins that will permanently retain the water; they are one of the final elements of the stormwater chain.

•

Rain gardens/bioretention areas – shallow basins design to collect and hold stormwater run-off allowing pollutants to settle and filter out as the wather rains through vegetation and soil into the ground, they are also final elements of the stormwater chain.

5.2. Potential of using rain gardens for controlling water quality4 As water from rainfall and snowmelt flows through the landscape, it picks up and carries contaminants from many different sources. This is called Non-Point Source pollution.

This polluted water ends up in streams, lakes and the ocean by flowing directly in or by going through untreated storm drains. Water also carries pollutants into underground drinking water as it soaks into the ground.

Pollution of urban runoff Urban runoff washes pollutants from streets, parking lots, construction sites, industrial storage yards and lawns. Besides “conventional” pollutants like sediments, nutrients, oxygen demanding materials and bacteria found in both urban and rural runoff also the toxic pollutants as metals, pesticides other chemicals can be detected.

“Conventional” pollutants 4

Miffin W, Poluted urban runoff: a source of concern; 1997

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•

Sediment

Mix of sediment produce by urban areas — flakes of metal from rusting vehicles, particles from vehicle exhaust, bits of tires and brake linings, chunks of pavement, and soot from residential chimneys and industrial smokestacks.

The leading sources of sediment in existing urban areas are industrial sites, commercial development and highways.

•

Nutrients

Runoff from both urban and rural areas is loaded with nutrients such as phosphorus and nitrogen.

Phosphorus is the nutrient of greatest concern because it promotes weed and algae growth in lakes and streams.

•

Oxygen Demanding Material

Urban runoff carries organic material such as pet waste, leaves, grass clippings and litter.

Runoff from older residential areas (with more pavement, more pets, and combined storm and sanitary sewers) carries the highest load of oxygen demanding materials.

•

Bacteria

Sources of bacteria in urban runoff include sanitary sewer overflows, pets, and populations of urban wildlife such as pigeons, geese.

Toxic Pollutants •

Metals (mainly lead and zinc)

Lead is a problem for both humans (damage to the nervous system and kidneys, high blood pressure and digestive disorders) and aquatic life (toxic). Zinc does not create human health problems, but it can be toxic to aquatic life. The primary source of many metals in urban runoff is vehicle traffic. Concentrations of zinc, cadmium, chromium and lead appear to be directly correlated with the volume of traffic on streets that drain into a storm sewer system.

•

Pesticides and herbicides

Tests indicate that most properly applied pesticides are bound up in plants and soil; therefore, little runs off. Nevertheless, some pesticides are frequently found in urban runoff at levels that violate water quality standards.

Finding agricultural herbicides in urban stormwater may seem surprising since they are not used in lawns and garden compounds. However, the herbicides in urban run-off are consistent with concentrations found in rainfall. It turns that those chemicals easily evaporate from treated farm fields and later end up in rainfall or snow.

•

Other Chemicals

There are many other potentially toxic chemicals found in urban runoff. Some of these chemicals are hazardous even in very small doses and require water quality standards set to parts per billion.

Sampling for these chemicals can be difficult and costly so information on them is very limited.

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Some of them are products of incomplete combustion from vehicles, wood and oil burning furnaces, and incinerators. Some are used as ingredients in gasoline, asphalt and wood preservatives, insulation in transformers and in electrical capacitors for old fluorescent light fixtures and appliances, coolants or lubricants, they might be present in sediment contaminated by past industrial waste discharges, spills, and waste incineration.

They remain in the environment for a long time, build up in the food chain, accumulate in human fatty tissue, and may eventually cause health problems (cancer, skin sores, reproduction problems, fetal abnormality development, immunity to disease, and problems with liver functions)

Using rain gardens for controlling water quality Properly designed rain gardens are not only reducing the run-off but also work as the bioretention facilities. They can control both quantity and quality of the urban run-off. Water purification is based on physical, chemical and biological processes. Bioremediation and phytoremediation are biological processes which can be used in rain gardens to improve the water quality.

•

Bioremediation is a biological and biochemical process associated with bacteria, fungi and plants to clean toxic contamination associated with pollution. For example – bacteria and fungi found in planting soil mix can be very efficient at degrading organic pollutants. Mulch and clay have the ability to absorb and immobilize heavy metals as copper, lead and zinc.

•

Phytoremediation specifically refers to the use of green plants to remove pollutants from the environment or render them harmless. Particular plants have remarkable ability to accumulate several hundred times more heavy metals in their biomass than most plants.

Such plants are called hyperaccumulators. At present, there are over 400 species of known hyperaccumulators which are able to take nickel, manganese, zinc, cadmium, thallium, copper, cobalt and arsenic.

•

Use of geo-fabrics combined with proper soil fraction and selection of plants with complex root system (see figure 2) can increase efficiency of settling pollutant sediments dramatically.

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Figure 2: Complex root system plays important role in sedimentation process.

5.3. Potential of rain gardens for creating an attractive environment5 Before looking in detail at the narrower concept of the rain garden it is very important to acknowledge the benefits of such installation that contribute equally to both - landscape sustainability and the people.

•

Rain gardens are good for wildlife and biodiversity – replacing paved surface or intensively managed grass areas with mixed naturalistic planting not only results in overall reduced needs for maintenance and inputs of fertiliser, water and energy, but will also greatly increase the wildlife and habitat value of a garden.

•

Rain gardens provide visual and sensory pleasure – human beings have instinctive attraction to water; whatever the reason, if there is a lake, pond, stream, fountain or other water feature within a garden or park – people and especially children will automatically head for.

•

Rain gardens are good for play – one of the most rewarding aspects of designing rain garden is a huge potential to both animate and bring the life to the landscape. Children are fascinated by water in all forms. Gathering, transportation, storage and release of rainwater are not only environmentally sustainable design but also create exciting and engaging play environments for children of all ages. (photograph 1, 2)

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Dunnett N., Clayden A. Rain Gardens - Managing water sustainably in the garden and designed landscape; Timber Press 2007

1

•

Rain water harvesting can result the cost savings by reducing municipal water bill, it also requires people to consider how we manage water when its supply can no longer be regulated by a turning on a tap and when its disposal is not just a matter of pouring it down a drain.

Photograph 1, 2: Children’s fascination with water. Outflow (left) gully (right)

Dialogue with people Keeping dialogue with people is one of the most important issues in urban ecosystem management. It is crucial for every project success so the people can recognize it from the beginning as something that they like and value. Underestimating the importance of such perceptions is a certain path to failure.

"If we design and implement something that might be extraordinarily effective from the standpoint of stormwater management or the standpoint of ecology, but people don't get it or don't particularly like it in their neighbourhood or their yard, it's just not going to be there in five or 10 years. You can just do so many innovative things with stormwater management within that framework, but I always start with what people like." (Joan Iverson Nassauer – the professor of landscape architecture at the University of Michigan) Effective communication with people can be achieved by popularising knowledge about rain gardens through different channels including marketing tools such as public relation, advertising, promotion and finally incorporating it with proposed changes in law.

Examples of the methods providing successful dialogue with people are listed below: Marketing

1

•

launching information and education campaigns by organizing special events and venues to raise people’s awareness about rain gardens and the sustainable development in general; such events should be organized by municipality in local community councils and schools (nurturing the next generation about responsible water usage is essential to achieve long term goals) as well as in door to door basis

•

educating by showing examples of accomplished rain garden projects in public spaces (municipality garden, schools, parking lots, etc.)

•

distributing information leaflets, issuing free public relations papers

•

creating social environment that enables each member for active participation

•

organizing ecological contests among community members

Training and active aid •

providing public and individual consultations free of charge

•

organisation of training courses for various social and professional groups

Law •

changes in law

•

law execution

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5.4. Rain garden variations 6 With urban development, sealing of the earth’s surface increase. One of the consequences is altered draining and trickling away of rain water. Small rivers swell after rain. Longer periods of rain will lead to an increase of the water level, bigger streams and in the end to floods.

Retention of rainwater can be improved by changing impervious areas into non-sealed ones.

Figure 3: Rainwater balance. With increasing development and the associated increasing amount of impermeable surfaces there is a reduction in the amount of infiltration and increase in surface water run-off.

Bioretention facilities use natural physical, chemical and biological processes of plants, soil and microbes (including adsorption, filtration, volatilization, ion exchange, decomposition) for capturing/reducing stormwater runoff and removing pollutants from the runoff. There are two major types of bioretention to consider, depending on individual needs and possibilities: •

Bioretention which allows to infiltrate water into the surrounding soil (functioning as an infiltration basin or rainwater garden)

•

Bioretention which collects the water by an under-drain system and discharge it to the storm sewers or directly to receiving waters (functioning like a surface sand filter)

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Minesota stormwater manual, 2005

1

Basic bioretention types on account of facility (function) Type of facility

Infiltration / Recharge

No under-drain. In-situ soils need to have a high infiltration rate to Description

accommodate the inflow levels (because of no under-drain). The infiltration rate of the in-situ soils must be determined through proper soil testing/diagnostics.

•

where high recharge of ground water is possible and would be beneficial for areas and land uses that are expected to generate

Application

nutrient runoff (residential and business campuses). •

areas where visibility is not a concern because hydraulic overload can cause extended periods of standing water conditions, although it is required that the water quality volume be drawn down within 48 hours

Figure 4: Cross-section of rain garden specialising in infiltration and/or recharging

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Type of facility

Filtration/Partial Recharge An under-drain at the invert of the planting soil mix ensures that the facility

Description

drains at a desired rate. The facility shown on the picture incorporates a filter material between the gravel blanket around the under-drain and the planting soil above (do not wrap the under-drain with filter fabric). It may contain a pea gravel diaphragm over the under-drain gravel blanket instead of other filter material. Attention to mulch type and its amount will ensure the adequate treatment of the anticipated loadings

Application

•

where high filtration and partial recharge of runoff would be beneficial

•

areas and land uses that are expected to generate nutrient and metals loadings (residential, business campus, or parking lots)

•

visually prominent or gateway locations in a community

•

recommended for tight impermeable soils where infiltration is limited (some volume reduction will be seen from evapotranspiration.)

Figure 5: Cross-section of rain garden specialising in infiltration

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Type of facility

Infiltration/Filtration/Recharge The raised under-drain has the effect of providing a storage area below the invert of the under-drain discharge pipe. This area provides a recharge zone

Description

and quantity control can also be augmented with this storage area.

Designed to incorporate a fluctuating aerobic/anaerobic zone below the raised under-drain discharge pipe. This fluctuation created by saturation and infiltration into the surrounding soils will achieve de-nitrification. With a combination of a fresh mulch covering, nitrates will be mitigated through the enhancement of natural denitrification processes.

Application

•

where higher nutrient loadings (particularly nitrates) are anticipated

•

where nitrate loadings are typically a problem

(residential communities)

Figure 6: Cross-section of rain garden specialising in filtration, infiltration and recharging

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Type of facility

Filtration Only The impervious liner is designed to reduce or eliminate the possibility of ground water contamination.

Description

The facility provides a level of treatment strictly through filtration processes that occur when the runoff moves through the soil material to the under-drain discharge point. In the event of an accidental spill, the under-drain can be blocked and the objectionable materials siphoned through the observation well and safely contained.

Application

•

recommended for areas that are known as potential stormwater “hotspots” (gas stations, transfer sites, and transportation depots)

Figure 7: Cross-section of rain garden specialising in infiltration

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Design Types for Various Land Uses It should be noted that the layout of the bioretention area will vary according to individual sites, and to specific site constraints such as underlying soils, existing vegetation, drainage, location of utilities, sight distances for traffic, and aesthetics. Designers are encouraged to be creative in determining how to integrate bioretention into their respective site designs. With this in mind, the following conceptual illustrations are presented as alternative options.

Design type

On-lot / Rain garden

Description Application

Simple design that incorporates a planting bed in the low portion of the site. • designed to receive flows from gutters, and/or other impervious surfaces

Photograph 3, 4: On-lot rain garden

Design type

Parking Lot Islands (Curbless)

Description

This application of bioretention should only be attempted where shallow grades allow for sheet flow conditions over level entrance areas. Water may be pooled into the parking area where parking spaces are rarely used to achieve an element of stormwater quantity control beyond the confines of the bioretention

Application

surface area. • in a paved area with no curb

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Design type

Parking Lot Islands (Curb-cut)

Description

For curb-cut entrance approaches, the water is diverted into the bioretention area through the use of an inlet deflector block, which has ridges that channel the runoff into the bioretention area.

Special attention to erosion control and pre-treatment should be given to the

Application

concentrated flow produced by curb-cuts.

• paved area with curbs (with some curb-cuts)

Figure 8: Parking lot islands

Design type

Road Medians / Traffic Islands Utilizing road medians and islands a multifunctional landscape can be created.

A buffer may be necessary along the outside curb perimeter to minimize the

Description

possibility of drainage seeping under the pavement section, and creating “frost heave” during winter months. Alternately, the installation of a geotextile filter fabric “curtain wall” along the perimeter of the bioretention island will

Application

accomplish the same effect.

• between roads

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Design type

Tree Pits / Tree Box Filters

Description

Designs vary widely from simple “tree pits”, used for local drainage interception to more formal tree box filters, which are a useful tool for highly urbanized streetscapes.

Tree box filters are bioretention areas installed beneath trees that can be very effective at controlling runoff, especially when distributed throughout the site.

Runoff is directed to the tree box, where it is cleaned by vegetation and soil before entering a catch basin. The runoff collected in the tree-boxes helps irrigate the trees. The system consists of a container filled with a soil mixture, a mulch layer, under-drain system and a shrub or tree. Stormwater runoff drains directly from impervious surfaces through a filter media. Treated water flows out of the system through an under-drain connected to a storm drainpipe / inlet or into the surrounding soil. Tree box filters can also be used to control runoff volumes / flows by adding storage volume beneath the filter box with an outlet

Application

control device.

• along streets and pavements, in the city centre

Figure 9: Tree box filters in a chain:

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5.4.1. Rain garden for residential areas The rain garden design for residential areas implies much less difficulties comparing to rain garden design for parking spaces and industrial/business areas.

The run-off quality is relatively high, so there is no big need to reduce pollutants. Major focus is to create attractive and pleasant environment close to the living place. Run-off reduction is a major profit for people and other living organisms, and environment in general.

Additionally, using water from rain harvesting might be a good solution for irrigation and laundry facilities as an ecological alternative to using potable tap water for that purposes.

To popularise and succeed in the idea of having the rain gardens in residential areas, the effective dialogue with dwellers has to be emphasised (information, education, help in design). Individuals take the decision about their own facilities so they have to recognize the rain garden from the beginning as something that they like and value.

5.4.2.

Rain

garden/bioretention

area

for

parking

space

and

industrial/business areas High water quality is a big complication for industrial/business areas because of high impurity of the run-off. Especially parking lots tend to be highly polluted with motor oils, heavy metals and various sediments. Dealing with this problem is challenging from both design and technical point of view. Introducing the rain gardens in industrial areas is more demanding and complicated than in residential areas.

Rain gardens/bioretention areas are very good solution on big parking lots - not only for collecting the run off but also for moisturizing the dry air and creating fine microclimate - paved surfaces store heat energy from the sun and re-radiate it; plants in rain garden can cool the area down by evapotranspiration.

Because of problematic pollution issues water harvesting can be considered only after testing with the positive results the quality run-off.

Rain gardens/bioretention areas might be also a good proposition to create the ‘image’ of the companies as nature and human friendly, carrying about natural environment and employees.

Promotion of rain gardens/bioretention areas to business owners, school directors and local governments should be encourage by education, support and finally with law regulations.

5.5. Plants suitable for rain gardens Most suitable plants for rain garden should be non-invasive species that are resistant to the stress from both wet periods of pooling as well as droughts between rainfall events. A variety of plants with large root structures which makes rain garden more effective and less susceptible to disease.

It is also better to use plants with a developed root structure instead of starting plants by seed.

There is number of publications with ready to use lists of plants however local conditions have to be taken into consideration, when transferability is discussed. It has to be appropriate to the local

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climate and weather conditions, light exposure and individual design preferences such as balance of form, scale, colour and four season interest. More precise information about plants, including the examples will be introduced in rain garden projects chapters.

5.6. Rain garden projects Two sites have been selected to re-design according to project objective:

location impervious surface [m2] green area [m2] purpose

5.6.1.

1. multi-storage residential house Copenhagen, Denmark 1500 200 reduce runoff

2. single family house Wroclaw, Poland 270 13793 reduce/manage runoff

Single family house

Introduction Single family house with garden situated in south-west Poland, near Wroclaw.

Photograph 5: South part of the plot.

Rainwater’s catchment and drainage House, extended recently about 1/3 of the surface, with a gable roof, has an large impervious surface which collects rainfall and lead it towards gutters. Because of lack of sewer system, rainfall is not channelled from the house, but soaks close to the building. As it is large amount of

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water it causes soil degradation and also foundation damage while soaking. For this reason south part of the roof is channelled to the well, located in the west side of the plot (this part of the roof will be not taken in consideration). Another impervious surface is the garage entrance – concrete ramp at the rear of the house (north, this part will be also excluded from project), road to the garage (designed, not existing yet) and pavement to the house (also not existing at the moment).

Topography The landscape is flat (only ramp slops towards building). Because the garden is not build yet, it will be easy to create suitable slopes.

Weather conditions for Poland7 Poland's climate is moderate in between the maritime and continental climates, lying in the zone of atmospheric fronts. This result in fairly wet and mild winters, with average monthly temperature of around 0°C, or heavy and dry winters, with average monthly temperature of -10°C. A similar variation in air temperatures and precipitation occurs in the summer season, especially during the vegetation period. Hot and dry summers (with less than 20 mm of rainfall in June, July and August) may alternate with cold and wet summers with a monthly rainfall up to 150 or even 200 mm.

Annual isotherms range between 6.5°C and 8.5°C; average temperatures range in January: from -1°C to -5°C, and June: from 17°C to 19°C. Average annual rainfall is 583 mm ranging between 500-600 mm in most regions of the country.

Two-thirds of annual rainfall occurs in the summer. Snow accounts for two thirds of winter (December - March) precipitation.

Figure 10: Yearly average - precipitation and temperature for Wroclaw. 8

Soil and permeability 7

www.icid.org/cp_poland.html

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www.icid.org/cp_poland.html

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In front of the building (south and west) soil is sandy, poor and permeable. Big surface at the rear of the plot (north and east), where heaviest soil occurs, is already filled with ramp. The owner wish to get there green house and vegetable garden (because of the fertile soil). Summing up, front location for the rain garden is recommended.

Vegetation Whole terrain is covered by unkempt lawn. Keeping lawn in good condition is made hard by soil compression (lack of pavement and road). Only south and and east side of the plot is planted with fruit trees, which has no big value. They are not cropping well and might be replaced with other trees/vegetation.

Services Telephone wire and water supply system run along the west fence, they are in neutral place.

System sizing 2

Surface [m ]

Surface not included in calculations

Total surface

roof pavement

Slopes into the rain garden

138,8

Surface for calculations

Slopes into other directions - (channelled to the well) 60,4

79,2

21,0

19,0

(slope to the lawn) 2,0

-

road

169.2

-

-

169,2

ramp

49,6

-

(slope to the garage) 49,6

-

Subtotal

19,0

Total Total property surface:

248,4 267,4=~270,0

1290 [m2]

Computational rainfall intensity event9 Rainfall intensity event calculations for Poland are: 101 [l/(s · ha)]

(with 1 year frequency)

127 [l/(s · ha)]

(with 2 years frequency)

173 [l/(s · ha)]

(with 5 years frequency)

Because of climate changes and abnormalities these changes bring, computational rainfall intensity event is taken bigger that seems to be needed, it is: 200 [l/(s · ha)] 1[l] = 0,001 [m3] 10 [min] = 600 [s] 9

Odwodnienie dróg,2006,Roman Edel

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1[ha] = 10 000 [m2] Calculations: For computational rainfall in 10 minutes (R 10), for total impervious surface 270 [m2] (project requirements) R10 = 270 [m2] · 0,00002 [m/s] · 600 s = 3,24 [m3] Average water-flow speed [v] and water flow [Q] in the stream-bed for trapezoid cross-section: slope: Is = 1% = 0,01 [-] depth of stream-bed: h = 5 [cm] stream-bed crown width: B = 25 [cm] buttress: lF = 6,5 [cm] Calculations for the stream: width of stream-bed: b = B - 2(lF2 – h2)1/2 = 16,7 [cm] wet perimeter: lzw = b + 2 lF = 29,7 [cm] buttress slope (indignation): n = (lF2 – h2)1/2 /h = 3,45 [-] water-flow cross-section: A = b · h + n · h2 = 169,75 [cm2] hydraulic radius: rhy = A/lzw = 0,000572 [cm] = 0,00000572 [m] roughness number for cobble stone: kst = 60 [m1/3/s] water-flow speed: v1 = kst · rhy2/3 · Is1/2 = 0,94 [m/s] water-flow: Q = v1 · A = 0,0159 [m3/s] = 16 [l/s] Water capacity of designed system: Stream capacity: R1 = 0,5(b+B)h·60= 0,4 [m3]

Containers (filled with field stones) capacity: 2R2 = 2·0,6·0,6·0,6·0,5 = 0,1 [m3] Rain garden capacity: R3 = (0,5·3·0,2+0,03·3)14 = 4,2 [m3]

Total rain capacity in designed system: Rc = R1 + 2R2 + R3 = 4,7 [m3]

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Assumption: Rc>=R10 4,7>=3,24 [m3] Conclusions: System capacity is big enough to contain 10 minutes' rain of 200 [l/(s 路 ha)] intensity.

Test points To show if stream is able to contain rain felled on the surface it is necessary to compare water-flow (Q = 16 [l/s]) to amount of rainfall on the surface (K) in characteristic points.

Assumption: Q>=K K1 = 18 [m2] 路 0,00002 [m/s] = 0,0036 [m3/s] = 0,36 [l/s]

Q>=K1

16[l/s]>=0,36 [l/s]

K2 = 60,4 [m2] 路 0,00002 [m/s] = 0,001208 [m3/s] = 1,208 [l/s]

Q>=K2

16[l/s]>=1,208 [l/s]

Q>=K3

16[l/s]>=4,044 [l/s]

2

3

K3 = 202,2 [m ] 路 0,00002 [m/s] = 0,004044 [m /s] = 4,044 [l/s] Conclusions:

Stream is big enough to contain rain felled on the surface in characteristic points.

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Rain garden composition and selection of vegetation

Figure 11: Plot arrangement

According to soil conditions rain garden is located in the west and stretch from main road toward building between road and pavement. To collect water and lead it to the rain garden long stream was designed.

Photograph 6: Rain garden will be located between path and road in front of the building.

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Figure 12: Rain garden concept

Figure 13: Rain garden cross section

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Vegetation is selected to stand short flood periods and also drought. As the level of rain garden is different the water conditions are dissimilar and the vegetation differ (drought-resistant, and low plants are on the border, higher and more flood-resistant plants are in the middle).

The high vegetation is designed at the plot entrance and slope down towards the home entrance what gives room in front of home, and separate from main road.

Salix alba is a big tree, but cut in certain height, gives new branches. This shape is a symbol, characteristic for the past polish landscape on the countryside, where people used fast growing trees for fuel.

There are two rain-water entrances to the rain garden (short stream branches). Entrance, where high vegetation is located, should be the main entrance (with 1% gradient) because of higher evapotranspiration of these plants. Other entrance, closer to house should get 0,5 % gradient.

Plant name 1. Salix alba

Type of plant, height [m]

Color of flowers

big tree

Comments Cut is required to keep tree in proper size (not to let it grow too big)

2. Salix purpurea ‘Nana’

shrub

Cut is required to keep shrub under crown of Salix alba

3. Miscanthus sinensis 'Cosmopolitan'

perennial,

1,5

4. Rudbeckia fulgida

perennial,

0,8 yellow

5. Echinacea purpurea

perennial,

0,7 violet

6. Sedum spectabile

Perennial,

0,4 pink

7. Achillea tomentosa

perennial,

0,2 yellow

8. Saxifraga arendsi

perennial, 0,04 purple

9. Sedum acre

perennial, 0,04 yellow

Photograph 7: Salix alba.

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Photograph 8: Plants used in rain garden.

Native soil is used to crate rain garden, only top layer of the soil has admixture of humus to improve soil conditions for plants.

Materials and structure: Materials/objects

Placement

1. concrete

pavement, road

2. concrete containers

under the gutters

Comments 2 pieces, size: 0,6m路0,6m路0,6m

3. granite cobble stone stream 4. granite curb

pavement border

5. field stones

containers, rain garden borders, stream entrance to the rain garden

6. humus

top layer of soil in rain garden

mixed with native soil create 0,1m fertile layer important for vegetation

The plot terrain is designed to facilitate communication to garage, home and outbuilding entrance.

At the pipe end, to slow down running water, there are containers, filled with stones for safety reasons (children).

Pavement, road and yard are made of concrete, and slope (0,5%) towards granite cobble stream or rain garden. Stream (gradient: 1%), to resemble small river, curve gently in the middle of the road, between car's wheels.

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Photograph 9: Example of stream (here used to reduce speed)

Over flood exit road was firstly designed across pavement, but calculations showed, that rain garden capacity is big enough to receive much more than computational rainfall, and over flood exit road is not needed.

Photograph 10: At the back of the house: outbuilding and designed concrete road.

Maintenance: This rain garden doesn't need intensive nurturing nor maintenance, however regular weeding, plant replacement (if needed) and cutting are required. Vegetation, in middle part, might need watering in extreme drought periods.

5.6.2.

Multi-storage residential house

Introduction

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Multi-storage residential house (200 flats) situated in Nørrebro - one of the central districts of Copenhagen with common courtyard surrounded by the housing blocks. The yard has approximately 2000 square meters and contains the features like playground, small basketball field, picnic tables, laundry lines and garbage/recycle containers. The courtyard is being used by residents on the regular bases.

Rainwater’s catchment and drainage The stormwater run-off from all the impervious surfaces and from the the roof is directed through the rain pipes into the gutters and city drainage system. Lawns and other pervious surfaces are less than 10% of the yard so infiltration is minimal.

Topography, soil and permeability There is no visible level difference. The courtyard is flat. The soil has to be examined, although anthropological soil type with mixed fractions is most likely to be detected as the property is located in the big city centre.

Vegetation The established vegetation covers roughly 10% of the courtyard and it consist lawns, shrubs and small fruit trees. Some trees have been trimmed dramatically and they represent very little visual and ecological value.

Rain Garden design Why rain garden in this place?

Environmental considerations become more and more in focus nowadays. The rising costs of urban drainage and water quality concerns are the problems that urban water management has to deal with in order to conserve and protect water resources and the function of the cities. Urban ecology - the creation of more sustainable cities - was discussed much in Denmark in the late eighties. Number of case studies demonstrating various aspects of sustainability had taken place.10 The environmental, economic and social impact of such initiatives can be high, if placed on the right locality especially if performed in small scale and using simple transparent technology with great symbolic value. Redesigning the courtyard in Nørrebro will create an example of environmentally friendly and easy to apply solution. If successful, project can be introduced and supervised by the municipality and eventually become an obligatory feature for both new and existing housing developments in Copenhagen.

Weather conditions in Copenhagen Copenhagen experiences a mild climate throughout the year. It seldom gets really hot or really cold. There may be a few occasional heat waves during June and August, but rarely more than 10

http://www.cardiff.ac.uk/archi/programmes/cost8/index.html

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30째C. The summer season brings temperatures averaging around 20째C. Precipitation falls throughout the year, with the greatest rainfall (70mm) in June and July which are the wettest months. The driest month is February with only 25mm rainfall. Thanks to the Atlantic gulfstream the winters are surprisingly mild with temperatures around 2째C to 4째C and only occasionally dripping to freezing. The only months when it might snow is January and February.

Figure14: Yearly average - rainfall and temperature for Copenhagen.

The temperate weather zone creates a good environment for rain garden vegetation especially because precipitation is the heist when the plants are most active. Additionally, influences of cool maritime climate from the Atlantic Ocean give possibility for planting all-year round attractive looking evergreen shrubs.

New design

Figure15: Required water movement on the site, according to the new design.

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Figure16: Rain garden concept.

Geometrical shapes merging with irregular organic lines create modern and attractive design.

Functions incorporated with design makes the area easy to read and pleasant to spent time in.

Wavy lines of gullies are creating not only the paths for water runoff but also are enriching the design of pavement. Light installations and simplicity of used materials are completing the composition.

Details Stormwater planters (figure 17) Shallow (35cm) concrete containers, situated along the building walls, mass-planted with Hemerocallis and Mahonia. They aim is to intercept water from the roof and with the help of plant roots purify it from sediments. Top soil and gravel drainage layer are separated with geofabric.

Stormwater planters help to reduce run-off through infiltration, evapotranspiration and storage.

Excessive water is directed through the pipes to the gullies. (photo 3, 4)

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Figure 17: Cross-section of the stormwater planter with Hemerocallis sp.

Gravel containers 1,2 meter wide stripes of white gravel located in front of the stormwater planters, along the pavement. They make an attractive background for Hemerocallis plants and additionally they can collect excessive water from both stormwater planters and pavement in case of unexpected overflow. Containers are on the same level as surrounding pavement; the layer of gravel is 15cm deep and is able to take up to 18m 3 of water. To stabilise the gravel and protect it from compaction the Gravelpave2 system is introduced.11 (Figure 18) The laundry drying lines (“umbrellas�) are located in gravel stripe as well. The yard is the semipublic space, so there is no need to hide such facilities, especially if they are made from top quality materials and have modern shape. Apart of it the water dripping from the wet clothes goes to the gravel instead of making unattractive looking puddles.

Figure 18: Gravelpave2 available in different colours to match the gravel.

Streams The gully is a shallow channel set within the pavement and it aim is to transport the water across the impermeable surface before releasing it into rain garden. The solution is simple and efficient.

Trapezoid shaped cobblestone channels with 2% slope are incorporated in concrete pavement.

Some stones are replaced with small colour glass squares with light installed underneath to create interesting visual effect. The gullies look attractive with or without water. (Photograph 11, 12) 11

Gravelpave2 is comprised of a porous geotextile fabric, molded directly to the integrated ring and grid system filled with decorative gravel. It provides support for gravel and creates a porous pavement surface. The system can be used for storage and filtration of rainwater. http://www.invisiblestructures.com/index.html

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Photograph 11, 12: Gullies – the rain garden chain element can also have very interesting design.

Playground Rain water will be a major attraction of the proposed playground. Water gathering, transporting, storing and releasing can be an amusing part of play for children of all ages. Play combined with gaining the knowledge about sustainability is the best way to educate future generations. One of the proposed playground features is the sculpted stainless steel fish attached to the building’s wall.

A jet of water is being released from the mouth of the fish by pushing the button on the wall. The water goes to the small sandpit (Photograph 13). This example was one of the most popular attractions in Potsdam garden festival in Germany 12. Other model solutions which can be used as inspiration for this particular playground are Mauerpark, Berlin Germany (Photograph 13) and the playground designed by Günter Beltzig13 in Vienna, Austria.

Photograph 13: Sculpted stainless steel fish which release the water.

Photograph 14: Solar sculptures in Mauerpark, Berlin.

12

Dunnett N., Clayden A. Rain Gardens - Managing water sustainably in the garden and designed landscape; Timber Press 2007 13 Beltzig G., Ksiega Placow Zabaw, Polish 2001

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Sport field The area can be used for various sport purposes for kids of different age. To keep the surface dry and safe the Terraway® technology will be the best solution. Terraway ® is a modern previous pavement made of minerals and resin14. It can take 1,2 l of water per minute/m2.

Photograph 15: Terraway® solution.

Garbage constructions Light, half-circular constructions, made of stainless steel, glass and wood. The side facing the building’s ground floor windows is planted with creepers to give the pleasant view for the inhabitants.

The linear depression around the construction takes the run-off from the roof and transports it through the gully, eventually to the rain garden.

Rain garden The proposed rain garden has to perform well in practical aspect - as the final water destination, but also it has to keep its visual qualities high all year round. The designed rain garden will feature trees, shrubs and perennials. There will be no lawns as they create a hard surface which does not absorb water as readily as garden areas. The technical construction will follow the Filtration/Partial Recharge scheme (shown in chapter 5.4). An under-drain pipe connecting all four partial gardens is essential in case of prolonged raining, overloading or if one of the other gardens will perform poorly.

Figure 19: Rain garden cross-section.

14

http://www.erbis.pl/index.htm

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The circular sitting areas with picnic tables are designed as cosy resting spots surrounded by green belt of luscious vegetation. Most of the selected plants flower in yellow – matching the building walls.

Resigning from use of many colours on behave of only a few ones gives the whole area modern and minimalistic look.

Figure 20: Rain garden/picnic table area cross-section.

Plant selection The selected plants are tolerant of both occasional flooding as well as dry periods. They are non invasive mixture of species which will adapt to the local environment stimulating the biodiversity incensement. Vertical layering will be achieved by a mix of tall, medium, and low-growing, groundcover species.

name

plant type

size

color

moisture tolerance

perennial

1,20m

ye

●●●

1,50m

Ye

●●○

photo

planters Hemerocallis hybrida

perennial, Miscanthus sinensis

ornamental grass

Mahonia aquifolium

shrub

1,20m

iiie

●●○

garbage constructions

3

name

plant type

size

color

moisture tolerance

Ye

○○○

Lonicera sp.

climber

Campsis radicans

climber

-

Ye

○○○

Schizophragma hydrangeoides

climber

-

Ye

○○○

Clematis Vitalba 'Paul Farges'

climber

-

Ye

○○○

Hedera helix

climber

-

-

○○○

tree

20m

shrub

3m

small tree

6m

photo

playground

Liquidambar styraciflua

Salix viminalis

iiie iie

iiie iie

●●○

●●●

rain gardens Salix fragilis ‘Bullata’

iie iie

●●●

3

name

Pennisetum alopecuroides

plant type

size

color

moisture tolerance

0,6-1,2

-

●●●

photo

perennial, ornamental grass

Aesculus parviflora

shrub

ye

●●●

Amorpha fruticosa

shrub

ye

●●●

Hamamelis virginiana

shrub

ye

○○○

Ligularia przewalskii

perennial

150 cm

ye

●●○

Lobelia syphilitica

perennial

100 cm

ye

●●●

Rudbeckia fulgida

perennial

100 cm

ye

●●○

4

name

Osmunda regalis

plant type

size

perennial

60-160

fern

cm

perennial Athyrium filixfemina

groundcover fern

Galium odoratum

color

moisture tolerance

-

●●●

-

●●●

ye

●●●

20-100 cm

perennial,

10-20

groundcover

cm

photo

Maintenance: While the plants in the rain garden are young and becoming established they may require some supplemental water during dry periods, though this should only be the case for the first year.

Some weeding may also be required the first year until the plants fill out and can compete weeds.

Once the rain garden has become established maintenance is minimal and will generally only include periodic mulching, pruning and thinning, and plant replacement. Mulching is an important part of rain garden maintenance. Mulch keeps the soil moist, allowing for easy infiltration of rain water. Each spring, rain garden should be re-mulched with 5-8cm of hardwood mulch.15

System sizing Surface [m2]

Total surface

roof

Surface for calculations

1500

1500

pervious pavement

600

-

impervious pavement

200

200

2300

1700

Total

15

http://www.uri.edu/ce/healthylandscapes/raingarden.htm

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Computational rainfall intensity event 200 [l/(s · ha)] (Rainfall intensity event calculations for Denmark are based on 140 [l/(s · ha)] according to historically, stable climatic conditions which has have been assumed for water resource management designs. However, global climate warming may lead to changes in rainfall events.

Hydrological changes can result floods, that’s why water resource planners must make future risk assessments. This is the reason of taking into calculations the bigger rain event factor.)16 1[l] = 0,001 [m3] 10 [min] = 600 [s] 1[ha] = 10 000 [m2] Calculations: For computational rainfall in 10 minutes (R10), for total impervious surface 1700 [m2] (project requirements) R10 = 1700 [m2] · 0,00002 [m/s] · 600 s = 20,4 [m3] Average water-flow speed [v] and water flow [Q] in the stream-bed for trapezoid cross-section: slope: Is = 2% = 0,02 [-] depth of stream-bed: h = 5 [cm] stream-bed crown width: B = 25 [cm] buttress: lF = 6,5 [cm] Calculations for the stream: width wet

of stream-bed: b = B - 2(lF2 – h2)1/2 = 16,7 [cm]

perimeter: lzw = b + 2 lF = 29,7 [cm]

buttress

slope (indignation): n = (lF2 – h2)1/2 /h = 3,45 [-]

water-flow hydraulic rough

cross-section: A = b · h + n · h2 = 169,75 [cm2]

radius: rhy = A/lzw = 0,000572 [cm] = 0,00000572 [m]

rate for cobble stone: kst = 60 [m1/3/s]

water-flow water-flow:

speed: v1 = kst · rhy2/3 · Is1/2 = 0,94 [m/s] Q1 = v1 · A = 0,45[m3/s] = 160 [l/s]

Water capacity of designed system:

16

Journal of Hydrometeorology, 2004 American Meteorological Society

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Containers capacity (stormwater planters) R1 = 24 [m3] stream capacity R2 = 0,5(b+B)h·200 = 2 [m3] rain garden capacity R3a = (πr12 · h + πr22· 1/3h) - 3πr32 · h = 17,8 [m3] R3b = 17,8 [m3] R3c = 9,7 [m3] R3d = 0,5πr12 · h = 4,8 [m3] R3 (total) = R3a + R3b + R3c + R3d = 50 [m3]

total rain capacity Rc = R1 + R2 + R3 = 92 [m3] Assumption: Rc>=R10 76>=20,4 To check if gullies (25) are able to contain all the rain fall from the surface it is necessary to compare water-flow (Q = 160 [l/s]) to the amount of rainfall on the total surface (K).

Assumption: Q>=(K/25) K = 1700 [m2] · 0,00002 [m/s] = 1700 [l/s] 1700[m2] : 25 = 68 [l/s] Conclusions: 160 [l/s] >= 68 [l/s] Number and size of gullies will collect all the water run-off.

6. Discussion Both projects consider rain gardens however local conditions are very different:

•

The private plot is located in peri-urban area and it contains a lot of green space. The multi-storage residential house is located in the city centre and surrounded by concrete and asphalt surfaces.

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•

Problem with water pollution is marginal in private plot while in residential house located in the city it has to be dramatically emphasised and solved.

•

In Poland there are big temperature amplitudes and cold winters. Climate in Denmark is mild with only occasional frosts. These differences affect the planting selection. Vegetation in Poland has to stand freezing cold.

•

Roof size, not the number of inhabitants has to be considered while taking decision about rain garden.

7. Conclusions •

Onsite water management is an ecological solution instead of using the stormwater drains and it has many economical and environmental advantages.

•

Rain gardens are protecting communities from flooding and drainage problems by increasing the amount of water that filters into the ground.

•

Rain gardens are helping to protect natural water resources from pollutants carried by urban stormwater

8. Literature 1. Dunnett N., Clayden A. Rain Gardens - Managing water sustainably in the garden and designed landscape; Timber Press 2007

2. Bannerman R., Considine E. Wisconsin Department of Natural Resources Rain Gardens A how-to manual for homeowners; DNR Publication 2003

3. Seymour R. M., Capturing rainwater to replace irrigation water for landscapes: rain harvesting and rain gardens.

4. Mary C. H., Low-Impact Development, The Journal for Surface Water Quality Professionals ‘Stormwater Features’.

5. Miffin W., Poluted urban runoff: a source of concern; 1997 6. http://insurance.essentialtravel.co.uk/tg-europe/denmark/copenhagen-weather.asp 7. http://www.mninter.net/~stack/rain/ 8. http://www.uri.edu/ce/healthylandscapes/raingarden.htm

9. www.livingmachines.com 10. http://www.bbg.org/gar2/topics/design/2004sp_raingardens.html 11. http://www.peterboyd.com/pteridomania2.htm

12. http://www.uri.edu/ce/healthylandscapes/raingarden.htm

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