Ways of rainfall channelling in cities by M Ples

Ways of rainfall channelling in cities

Maria Plesniak Individual Study at Copenhagen University (5th year of master studies at WrocĹ&#x201A;aw University of Environmental and Life Sciences) Supervisor: Senior Researcher, PhD Marina Bergen Jensen Academic year: 2007/2008 ECTS credits: 15

Table of content

Introduction……………………………………………………….…….4

Methods and materials……………………………………….……….5

Sustainability and stormwater management………………………..6

Ways of rainfall channelling and reduction (literature overview)…8 4.1. (A) Stormwater infiltration devices…………………………...….…..8 4.2. (B) Stormwater retention devices (without infiltration)…….…..….15 4.3. (C) Stormwater pre-treatment devices…………………….….……19 4.4. (D) Conveyance devices………………………………….…………23 4.5. (E) Other devices……………………………………………...……..23

Stormwater chain examples…………………………………….…..24 5.1. Bo01, Malmo……………………………………………………….…25 5.2. Augustenborg, Malmo……………………………..…………….…..30

Discussion…………………………………………………………….36

Bibliography……………………………………………………….…..39

Appendix……………………………………………………….……...40 8.1. Harmful substances and its treatment in soils……………….……40 8.2. City – soil and water conditions………………………………….…43

Acknowledgement

I wish to thank my supervisor Marina Bergen Jensen for patience, support and in particular for help with translation.

1. Introduction In the past rain was almost always seen as blessing. It was needed to water fields and animals. Stormwater, besides natural disasters, wasn't the difficulty until more modern times.

Stormwater

and

wastewater

became

problematic

with

increasing

urbanisation. Various facilities were created and developed. Street gutters were already being built in antiquity, but puddles and stench were common. Later, an underground net of pipes, the sewage system, became an effective solution that has survived until the present. The problem of stormwater disappeared from view, but has it been solved once and for all? Today, we know that has not: municipal authorities complain about damages that flooding is causing after heavy rains; climatologists are warning about inefficient amounts of pure water and its increasing pollution; ecologists inform us that big part of the sewage which is not purified contaminates rivers and lakes. Some facilities render making less good that they adumbrated. There are many ways of stormwater channelling. Generally, it can be reduced by infiltration or evapotranspiration (rain gardens, pervious pavements, drain pipes, lawns, swales), retained (green roofs, pools, containers), pre-cleaned (surface sand filters, sedimentation wells) or conveyed (gutters, channels, sewer system). To date, rainwater has mainly been redirected toward surface waters or sewage treatment plans. But with sustainable development there is tendency to change direction and use more and more sensitive solutions. They are very often combined in a â&#x20AC;&#x2DC;stormwater chainâ&#x20AC;&#x2122;. Combined system helps to reduce run-off locally (prevents flooding), improves water quality, local environment and also the ecological awareness of people. The objective is to describe sustainable stormwater management solutions that are alternative or supplementary to the traditional stormwater management in sewer system. By describing sustainable urban drainage solutions (SUDS), presented as elements in a 'stormwater chain', is expected to be a clear and easy to understand way for non-technical professionals as well for non-professional private lot owners. Terminology from the first part of the thesis is used to describe a number of solutions in Malmo, and further the quantitative contribution of individual elements to the overall stormwater solution is assessed.

2. Methods and materials Literature survey - peer-reviewed publications, conference materials, books, manuals, and web-sites are used to present selected ways of stormwater reduction, retention and conveyance. The description of devices is made to be systematic and easy to understand. The terminology, after site survey, is applied to stormwater chain examples from Malmo. Then difficulties are clarified and some questions are posed.

Flow chart illustrating formation of this paper

3. Sustainability and stormwater management Sustainability Up to 1987 (the Brundtland Commission, formally the World Commission on Environment and Development) the global development was seen as two dimensional. In 1987, to the economic and social, environmental (third contribution) was added and a sustainable development was defined.

Global Development up to 1987

Global Development after 1987 1

The sustainability was specified as a development that meets the needs of the present without compromising the ability of future generations to meet their own needs.2

Sustainable stormwater management Sustainable Drainage Systems (SuDS), also known as Sustainable Urban Drainage Systems (SUDS), are solutions that reduce potential adverse impact of the development on disturbed there water. The idea behind SUDS is to collect, store, clean, allow to evapotranspirate or infiltrate and drain away surface water by replicating natural systems (i.e. reed beds, constructed wetlands) before allowing it to be released slowly back into water courses. SUDS prevent flooding and sewer flooding on the development site, release sewage system and also protect and enhance water quality.

SUDS deal in an integrated way with the issues of water quantity, water quality and amenity 3

1 Edwards Brian, Hyett Paul, Rough Guide To Sustainability. RIBA Publications, 2002. 2 Edwards Brian, Hyett Paul, Rough Guide To Sustainability. RIBA Publications, 2002. 3 Adapted from: Dâ&#x20AC;&#x2122;Arcy BJ. Urban best management practice. In: Pratt CJ, editor. Proceedings of the Fifteenth Meeting of the Standing Conference on Stormwater Source Control, School of The Built Environment, Coventry University, 1998.

Some principles how return excess surface water to the natural water cycle with minimal harmful effect on the environment and people are to: •

manage the stormwater that runs off on site as close to the source as

possible •

slow down the velocity of the run-off

•

treat polluted water using natural processes; and

•

release to the watercourse and the groundwater water that has good quality.

SUDS are to be easy to manage, cost effective, flexible to use, environmentally and aesthetically friendly and require little or no energy input (except from environmental sources such as sunlight, etc.). To achieve the goal of SUDS there is necessity of working in partnership by numerous disciplines and agencies (developers, planners, engineers, architects, landscape architects, ecologists and hydrologists). 4, 5 The term SUDS was described in United Kingdom, however United States has developed their own approach and own terminology such as Best Management Practice (BMP) and Low Impact Development (LID).6

4 http://en.wikipedia.org/wiki/Sustainable_urban_drainage_systems 5 http://www.scotland.gov.uk/Publications/2001/07/pan61 6 http://en.wikipedia.org/wiki/Sustainable_urban_drainage_systems

4. Selected ways of stormwater reduction, retention and conveyance (literature overview)7 4.1. (A) Stormwater infiltration devices A.1. Infiltration without retention volume Principle Stormwater is allowed to seep into the soil through permeable or vegetated surface. There is no room for temporary holding back of water (retention) Ability to purify water Very good on the top level of a surface covered with grass and when slowly soaking away through fine-grained top layers. Maintenance Normal maintenance of the grass (regular moving) and other plants. Possible applications • areas with high or average permeability • roads (in parks, in residential areas, fire roads), courtyards, squares, sports grounds Advantages Disadvantages • good conditions for maintenance • small retention possibility • high ability to purify water (water quality • demand of a big surface doesn't have to be high) Combination and variation possibilities • with retention and treating devices • overflow to swale, drainage pipe or ditch where efficiency of infiltration is insufficient. Possible sorts: • without vegetation (mineral foundation, drainage asphalt, concrete grate, permeable arrangement of paved surface) • with vegetation: grass or other plants (grassy rubble, openwork gratings with grass, lawns) Tips • •

the absorption capacity has to be bigger than the expected rainwater flow inflow to whole surface should be evenly distributed

Permeable parking lot

7 Geiger Wolfgang, Dreiseiltl Herbert, Nowe sposoby odprowadzania wód deszczowych. Bydgoszcz: Ofic. Wyd. ProjprzemEKO, 1999 Pictures without stated source are from this book.

A.2. Infiltration with retention on the surface A.1.1.

Swales, rain gardens, bioretention areas

Principle Surface infiltration through humic soil surface with and fine grained top layers. Used in open, green areas with possibility of temporarily holding the stormwater. Ability to purify water • high biological purification in a well-structured soil layer covered with vegetation • retention of insoluble substances. Maintenance • regular maintenance and control (especially in autumn after leaves have fallen) • regular moving demanded • surface smoothing away when needed Possible applications • areas with average permeability • in order to develop or improve housing surroundings • green areas, road sides Advantages Disadvantages • high ability to purify water (water quality • may accumulate rubbish doesn't have to be high) waste • high retention • requires space • good conditions for adaptation in green areas • possible to use as a garden element if cover with various vegetation • good conditions for maintenance

or organic

Combination and variation possibilities • with belowground storage (infiltration trench) • upstream retention or pre-treatment devices Tips • • •

stormwater should be retained no longer than 1-2 days (longer period may cause surface sealing of the soil and consequently bloc the infiltration) avoid surface sealing and compaction during construction (e.g. heavy machinery) the bottom must be even or cascade shaped

Rain garden with perennials8

Swale9

8 http://www.rfcity.org/Eng/Stormwater/YourProperty/YourProperty.htm

Cross-section of a rain garden/bioretention area10

A.1.2.

Pools

Principle Water infiltrates through humic soil surface and top fine grained layers of the soil. The water capacity is higher and the water can be retained for a longer period than in swales. Ability to purify water • good biological purification in humic layer of a soil • retention of insoluble substances • higher purification efficiency if formed sedimentation layer is kept Maintenance • regular maintenance and control (especially in autumn after leaves have fallen) • regular greenery maintenance • removal of sediment when the infiltration is blocked Possible applications • mainly used for motorways drainage • for bigger drainage (> 1ha) • areas (existing or new developments) with efficient surface area

Cross section of infiltration pool 9 Picture taken by Maria Plesniak 10 Minesota stormwater manual, 2005

Advantages Disadvantages • high ability for purification (water quality • dangerous for children when filled up doesn't have to be high) (fence may be needed) • good conditions for water storage • self-blocking if wrongly maintained • good conditions for adaptation in the • if sediment is not removed toxic landscape (as a biotop) concentrations may build up (conflict with • good conditions for maintenance biotope ambition) Combination and variation possibilities • upstream retention or pre-treatment devices • with swales Tips • • •

vegetated bottom and banks increase infiltration rate avoid surface sealing (e.g. by building trucks) to avoid bank erosion use boulders at the water inflow

Infiltration pools11

11 Picture 1 and 2 – unknown source

A.1.3. A.1.3.1.

Infiltration with subsurface retention Soakaways

Principle Concentrated below-ground spot from where stormwater soaks into the soil through artificial filtration layers. There is direct infiltration into groundwater and no possibility to soak through fine grained top soil layers. Ability to purify water • poor condition for water purification • water has to be pre-treated • retention of larger insoluble substances Maintenance • regular control • removal of clocking layers of sediment Possible applications • when soil permeability is good and average • inside cities and where available space is limited

Inflow of soakaway

Advantages Disadvantages • small surface demand • no possibility to water purification • good controlling possibility • limited maintenance possibility • application possible even where there • water shouldn't contain fine suspensions are impermeable top layers or other pollutants • high reconstruction costs when blocked Combination and variation possibilities • upstream retention or pre-treatment devices • combined with swales and drainage pipes

Soakaway crossection12 12 http://www.webcomsystems.co.uk/help/pcconc.htm

A.1.3.2.

Absorption ditch/trench

Principle Soaking away under the ground by artificially inserted gravel with good permeability, big infiltration surface and high retention capacity. Ability to water purification • very small if not constructed with surface infiltration (then pre-treatment devices are required) and when soaking away omit top fine-grained layers (good only through top layers if soil is covered with vegetation) Maintenance • no maintenance possibility, replacement necessary Possible applications • grounds with average permeability • when drilling of less permeable layer is needed in order to reach more permeable one Advantages • small surface demand • good retention capacity • small restrictions in surface use

Disadvantages • poor conditions for water purification • no maintenance possibility • water shouldn't contain suspensions or other pollutants

Combination and variation possibilities • possible location just below the surface or deeper • different shapes possible: linear, wavy, bended, network • with swale (for better retention capacity and better water purification ability) • upstream retention or pre-treatment devices • additional infiltration might be provided by top fine-grained layers

Cross section of absorption ditch with (a) point inflow and (b) surface inflow

A.1.3.3.

Drainage pipe (infiltration pipe)

Principle Perforated drainage pipes in covered ditches provide linear infiltration. Pipes and wrapping gravel assure retention capacity. Ability to water purification • no possibility for water purification. Pre-treatment devices are needed. Maintenance • conditionally allowed rinsing of pipes Possible applications • grounds with average permeability • possibility to omit higher non permeable layers Advantages Disadvantages • small surface demand • no possibility for water purification • good retention capacity • low maintenance and conservation possibility • small restrictions in surface use • water shouldn't contain suspensions or • light constructions on the surface are other pollutants combination options? possible (e.g. a garage)

4.2. (B) Stormwater retention devices (without infiltration) B.1.1.

Sealed filtration swale

Principle Sealed, drained swale with good retention and water purification functions. Water is carried away to a natural receiving water body, or an infiltration device. Ability to purify water • high biological purification in a living layer of a soil • holds back dissolved substances Maintenance • regular greenery maintenance Possible applications Swale with sealed bottom • application independently from soil permeability and contamination • for pre-treatment of heavier contaminated water • near roads with high traffic volume Advantages Disadvantages • optimum control possibility before water • lack of percolation (volume reduction) is soaking away or discharged • may accumulate rubbish or organic • good retention properties waste • good conditions for adaptation in green areas Combination and variation possibilities • downstream soaking away devices, pre-treatment devices or vegetation passages

Cross-section of a filtration swale13

13 Minesota stormwater manual, 2005

B.1.2.

Retention and filtration pool

Principle Sealed, drained pool with humus surface and light liquid (oily substances) separator added. Ability to purify water • high biological purification in humic layer of the soil • holds soluble substances Maintenance • regular greenery maintenance Possible applications • only for bigger drainage basins (>1ha) • for pre-treatment of heavier contaminated water • near roads with high traffic volume Advantages Disadvantages • optimum control possibility before water • dangerous for children when filled up is infiltrated or discharged (fence may be needed) • good water purification ability • lack of percolation (volume reduction) • good water storage ability (backwater) • possibility to create shape of natural pond

Retention and filtration pool

Retention pool in Augustenborg14

14 Picture taken by Maria Plesniak

B.1.3.

Roof with clogging of water and green roof

Principle Stormwater retention in vegetated porous ground foundation or water clogging (backwater). Delayed run-off and run-off reduction by evaporation. Ability to purify water roof with clogging of waters • no possibility for water purification green roof • biological and mechanical rainwater purification by filtration through vegetation and porous ground medium Maintenance roof with clogging of waters • regular water outlet controlling green roof • maintenance during first 2-3 years (water outlet rinsing if blocked, vegetation maintenance) • with intensive vegetation watering and maintenance is needed Possible applications • on every flat roof • on sloping roofs, with slopes up to 30*. At higher slopes planting is possible only with protection • good efficiency in dense urban areas Advantages Disadvantages roof with clogging of waters roof with clogging of waters • good retention efficiency • higher roof load • often small costs of flat roof • higher leakproofness requirement reconstruction (choke and overflow installation) green roof green roof • higher roof load • good retention efficiency • higher leakproofness requirement • air contamination reduction and air • high maintenance expenditure with enrichment in oxygen, local microclimate intensive vegetation improvement • increased wildlife (promoting diversity of plants, insects and birds) • temperature regulation under the roof • lengthening of the life expectancy of the roof • improvement in the appearance of the rooftops • good adaptation possibilities in the landscape • noise suppression Combination and variation possibilities roof with clogging of waters • with infiltration devices green roof • with infiltration devices • with stormwater reusing devices

Roof with clogging of water

Green roof

Green roof in Augustenborg15

Extensive green roof in Augustenborg16

15 Picture taken by Maria Plesniak 16 Picture taken by Maria Plesniak

4.3. (C) Stormwater pre-treatment devices C.1.1.

Sedimentation well

Principle Intermediate stormwater storage and mechanical purification by sedimentation in concrete well (with bottom). Ability to purify water • purification by sedimentation • light and floating substances holding by dipped wall • dissolution and washing out of sediment particles Maintenance • regular sediment removal • controlling twice a year Possible applications • stormwater pre-treatment with high level of sediments • small stormwater inflow Advantages • small surface demand • no or small restrictions in surface usage

Disadvantages • ability to purification limited substances that sediment easily

Combination and variation possibilities • downstream soaking away • pre- treatment devices Tips •

build with dipped wall close to the outflow and cat ladder

Cross section of sedimentation well

C.1.2.

Soakaway with sedimentation tank

Principle Combined infiltration and sedimentary well. Low part is leakproof (creating sedimentation chamber) Ability to purify water • purification by sedimentation • sediment outflow reduction by usage of geotextile Maintenance • yearly sediments removal • controlling four times a year Possible applications • stormwater pre-treatment with high level of sediments Advantages Disadvantages • small surface needed • small maintenance possibility • no or small restrictions in surface usage • purification ability limited to easily falling substances • possibility to omit higher non permeable layers • small construction costs Combination and variation possibilities • upstream retention or other treatment devices

Cross section of soakaway with sedimentation tank

C.1.3.

Geotextile filtration bag for soakaway

Principle Geotextile in form of bag fitting a well, typically in a road. Water purification by filtration through geotextile. Ability to water purification • high sediments holding (also dust and clay) Maintenance • first cleaning after a year, later every second year (bag rinsing) • controlling four times a year Possible applications • pre-treatment for water with dominant insoluble substances • in cities - small surface needed Advantages • higher purification ability than for soakaway with sedimentation tank • very small surface needed Combination and variation possibilities • downstream retention devices and treatment devices

Sediments removal from the bag

C.1.4.

Vegetation passage

Principle Rainwater flows through soil and vegetation roots. Sealed bottom. Ability to water purification • high ability to purify water by oxygen and oxygen-free decomposition • mechanical purification • chemical and physical (adsorption) bond on soil particles • biological ability to purify is 20% lower in winter Maintenance • maintenance of vegetation • yearly vegetation cutting, at the latest in the spring • regular controlling of inflow and outflow Vegetation passage cross section Possible applications • more advanced stormwater purification with high biological contamination • in cities as a biotope Advantages Disadvantages • high ability to remove soluble biological • maximum efficiency only with constant substances inflow • good controlling possibilities • rainwater shouldn't contain insoluble substances • good adaptation possibilities • big surface demand • lack of objectionable odour enable for usage in residential areas Combination and variation possibilities • recommendation to connect to precedent retention and mechanical treatment devices • succeeding by infiltration devices Tips • • • •

water level should be always below the surface to avoid water bypassing above the surface upstream sedimentation device to clean from suspended impurities use gravel to suppress water hammer avoid soil consolidation

Example of vegetation passage

4.4. (D) Conveyance devices Conveyance devices serve to transfer rainwater from one place to another. Examples: a) open and closed channels b) gutters c) pipes d) swales (also listed in A.1.1) e) sealed filtration swales (also listed in C.1.1) They can be made of permeable materials (d) or have a sealed bottom. They can have a transportation function only (a, b, c) or have more functions (d, e).

Open channel examples17

4.5. (E) Other devices Other devices are devices not arranged in lists above or have different purposes (f. ex. pipeâ&#x20AC;&#x2122;s ends, thresholds, stones, cubes etc.).

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

5. Stormwater chain examples18 Stormwater chain Itâ&#x20AC;&#x2122;s a bigger system that combines different stormwater management elements.

Stormwater chain example19

18 Pictures taken by Maria Plesniak, Marina Bergen Jensen and Marta Derska. Cross sections drawn by Maria Plesniak 19 Adapted from: Dunnett N., Clayden A. Rain Gardens - Managing water sustainably in the garden and designed landscape; Timber Press 2007

5.1. Bo01, Malmo

Bo01 development plan

In Western Harbour (Vastra Hamnen) on previous harbour, shipyard and industrial are the new housing estate (Bo01) is developing. The first stage was built and completed for the European Housing expo 2001 as the â&#x20AC;&#x2DC;City of tomorrowâ&#x20AC;&#x2122;. The aim was to make the Western Harbour an internationally leading example of a densely populated, environmentally sound neighbourhood. Houses are built close together â&#x20AC;&#x201C; the ecological and sustainable society has to use valuable ground space efficiently. Pedestrians and bicycles have priority (Bo01 is car free). The area gets its energy supply from renewable sources; solar energy and wind power. Some IT-solutions are implemented for reading meters and

controlling of energy use and ventilation in dwellings. Water is feature in various forms: (a) salt water in the open sea, in the harbour and in the canal, (b) fresh water in a system of ponds and miniature canals. The water from the sea is pumped to the canal and tap water runs trough retention ponds. Runoff is controlled locally. Rainwater is delayed on green roofs and in retention pools located in courtyards and public spaces. It runs through open paving channels which discharge via the ornamental canal into the sea. There is no water harvesting for washing. Visible waterways combined with trees and undergrowth (a symbol of life and ecology of the district) provide good qualities to this rather sterile urban environment.20

A. Infiltration 1. permeable surfaces

Western Harbour - Bo01 C. D. Type of device Retention PreConveyance treatment 1. pre1. open and 1. pools (canal treatment closed channels along the park and pools with vegetation) 2. gutters 2. green roofs B.

E. Other 1. pipe's end, thresholds

Table showing type of device and its major contribution in the stormwater chain

Conveyance and retention are the most significant in the area.

Cross section of stormwater chain (marks are reflections of marks from the table)

20 www.eco-guide.net and www.greenroof.se

A1. Permeable surfaces Besides parks and courtyards there is lack of permeable surfaces. The area is densely build and paved between buildings to provide access to them. B1. Pools Retention pools in Bo01 are in form of (a) pools with vegetation (supply with water is provided by rainwater and tap water running through it) and a large, 1 meter deep (b) canal along the â&#x20AC;&#x2DC;Ankarparkenâ&#x20AC;&#x2122; park.

Pools with vegetation (a)

Pools with vegetation (a) next to the channel (b)

Channel (b)

B2. Green roofs Low maintenance green roofs are usually covered with Sedum that gives reddish colour and is able to cope with extreme drought and at the same time to soak up huge amounts of rainwater while growing on very thin earth layer (5cm, including drainage layer).

C1. Pre-treatment One pond serves as pre-treatment device where water is sucked in the device and purified (the mechanism of purification is not determined because of lack of sources).

D1. Open and closed channels There are various shapes (rounded, cubic and trapezoid) and depth of the canals. They lead water to through retention ponds to the canal or sea.

Sometimes however they seem to be only a dummy going up the slope.

E1. Pipeâ&#x20AC;&#x2122;s ends and thresholds Pipeâ&#x20AC;&#x2122;s ends are attractive visually and also, together with thresholds, are implemented to slow down the velocity of the runoff.

5.2. Augustenborg, Malmo Ecostaden Augustenborg (Eco-city Augustenborg) is an ecological development in the existing district in Malmo, Sweden. The Eco-city project is made up of several sub-projects, one of which is the construction of an open stormwater system. Project was developed in 1998-2002 by the Malmรถ Department of Water and Wastewater. Few years ago Augustenborg experienced damage and inconvenience from basement flooding about 5-6 times a year. It was due to combined sewer and rainwater system that was underdimensioned for modern conditions (where green spaces have been replaced with impervious surfaces) and also due to the pressure from other parts of the city. The goal of the solution is to detain about 70-80% of 30-year rain. In fact in 1997 it was able to take 50-year rain. Water from impervious surfaces is channelled through open and closed canals to pools and filtration swales before finally draining into a traditional stormwater system. Tops of the flat roofs covered with vegetation are able to hold huge amount of rainwater. Holding ponds and temporary flood areas are incorporated to the system which in the first phase stops in a large pool with vegetation. In the second phase water from the industrial area is lead through the park as seminatural stream (filtration swale) to the second pond also containing greenery. Excess water from the housing estate, the school and park ends up in the same place.21

Plan of Augustenborg

21 www.eco-guide.net and www.greenroof.se

A. Infiltration 1. permeable surfaces

Augustenborg C. Type of device Retention Pretreatment 1. filtration swales B.

2. pools

Conveyance

Other

1. open and closed channels

1. pipeâ&#x20AC;&#x2122;s ends, thresholds, stones, cubes

2. gutters

2. overflow protection

3.green roofs Table showing type of device and its major contribution in the stormwater chain

Retention and conveyance are the most significant in the area.

Cross section of stormwater chain (marks are reflection of marks from the table)

A1. Permeable surfaces Augustenborg area is much less sealed than Bo01 (there is a lot of greenery and lawns), but clay soil on the certain level doesnâ&#x20AC;&#x2122;t allow to water to infiltrate deeply into the groundwater. The stormwater is running along this permeable layer and riches basements. So even some devices look like they are able to soak water, they have sealed surface below that doesnâ&#x20AC;&#x2122;t allow deep infiltration.

B1. Filtration swale Filtration swales are to transport stormwater to its destination point - retention ponds - allowing also some retention, evaporation and transpiration. They are highly visible in the landscape and incorporated in it very well.

B2. Pools Pools have also sealed bottom. Some have concrete banks, some are vegetation covered.

The amphitheatre can flood

Rainwater runs also through a sand surface for children

Basketball court is a large magazine for stormwater

Last ponds have always overflow protection (inflow to the sewer)

B3. Green roof Tops of the roofs of buildings for recycling and of the industrial area are covered with low maintenance greenery, mainly Sebum.

D1. Open and closed channels Channels are very variable, from small to very big; remaining river with small bridges; with very formal and geometrical or informal and natural shapes.

Big open channel with stormwater clogging by thresholds

Open channel combined with swale E1. Pipe’s ends, thresholds, stones, cubes Pipes ends, thresholds, stones and cubes besides its role to slow down the velocity of the runoff have big esthetical value.

Tear drops create movement in the water, cleans off the smaller particles, and allow water to run-off even without slope. E2. Overflow protection The overflow protection is provided at the end of the ‘stormwater chain’ (entrance to the sewage).

6. Discussion Sustainability The ambition of open stormwater management in Bo01 is to demonstrate how to retain rainwater without allowing water to infiltrate as it usually does. Overflood in this are is not such a big problem as in Augustenborg because of proximity to the sea where the water can be easily discharged. So there is no need of water quantity reduction. Quality of the rainwater shouldnâ&#x20AC;&#x2122;t be a problem because of car traffic elimination in the area (this is my assumption, not stated in any source). There is additional energy consumption by pumping tap water, sea water and waste of the potable water. However sustainable solutions try to avoid unnecessary energy consumptions and waste production, from the broader perspective in Bo01 it is not so negative. Previously as an industrial area, Western Harbour is converting today to the high density housing, business and services development. It is located very close to the city centre and is to be attractive. Besides different housing types in the area, attractiveness is provided by well shaped and organised canal and park in the middle of the district, public spaces and semiprivate courtyards. Water is there important element of the amenity22.

Position of the solution in stormwater sustainability triangle The ambition of open stormwater management in Augustenborg is to prevent damages from flooding. New stormwater solutions are introduced in the area dealing with problem locally: minimising run-off and minimising pressure on the sewage system. 22Term explanation from Wikipedia (http://en.wikipedia.org/wiki/Amenity): â&#x20AC;&#x2DC;In the contexts of real estate and lodging, amenities are any tangible or intangible benefits of a property, especially those which increase the attractiveness or value of the property or which contribute to its comfort or convenience. Tangible amenities might include parks, swimming pools, health club facilities, party rooms, bike paths, community centres, doormen, or garages, for example. Intangible benefits might include a "pleasant view" or aspect, low crime rates, or a "sun-lit living room", which all add to the living comforts of the property.â&#x20AC;&#x2122;

Choosing an open stormwater system in which the water is visible has added ecological and aesthetic contribution to the community. The rainwater is no longer seen as a waste but as a resource that adds value to the landscape. Water quantity is highly reduced. There is no rainwater quality control, but it might not be necessary because of character of the area: housing with low traffic volume (this is my assumption, not stated in any source). The amenity is achieved by good incorporation of different devices and solutions into the landscape. The stormwater chain adds specific character to the place.

Position of the solution in stormwater sustainability triangle Determination of sustainability of devices is difficult to define. It depends what devices are chosen, how they are combined, what is the goal to achieve and how it is done. Some solutions that are sustainable alone might be used in non sustainable way. There are also pros and cons of using alternative or supplementary to the sewage system solutions. For usage might be: counterbalance of the sewer system, damages prevention, healthier/sustainable environments, water treated as a resource not waste, savings (not in every case). Against usage might be difficulty to choose proper devices (size, treatment), big land and surface occupation in many cases, worthlessness if existing sewage system is able to receive stormwater or worthlessness if construction of the SUDS is too expensive.

Terminology There are some difficulties in describing SUDS and applying terminologies to solutions for example using same terminology for different solutions or many terms for one device (f. ex. what is the difference between pond and pool? Can pond be special kind of pool?) There is also gap between professionals and non-professionals in terms of terminology and understanding of the processes when applying technical solutions or advanced technologies. There is hesitancy if the stormwater is polluted and need to be pre-treated, what kind of pollutants it contains and what processes/devices might be used to purify the

rainwater and how does the regulator know that controlling that specific pollutant alone will prevent pollution from the urban run-off. Collaboration is needed: ‘To provide Sustainable Urban Drainage Systems (SUDS) requires a number of disciplines and agencies (developers, planners, drainage engineers, architects, landscape architects, ecologists and hydrologists) to work in partnership. (…) Planning policy should set the framework in structure and local plans and in masterplanning exercises.’

http://www.scotland.gov.uk/Publications/2001/07/pan61

7. Bibliography 1. A green Vitruvius – Principles and Practice of Sustainable Architectural Design. James & James, 1999 2. D’Arcy BJ. Urban best management practice. In: Pratt CJ, editor. Proceedings of the Fifteenth Meeting of the Standing Conference on Stormwater Source Control, School of The Built Environment, Coventry University, 1998 3. Dunnett N., Clayden A. Rain Gardens - Managing water sustainably in the garden and designed landscape; Timber Press 2007 4. Edwards Brian, Hyett Paul, Rough Guide To Sustainability. RIBA Publications, 2002 5. Geiger Wolfgang, Dreiseiltl Herbert, Nowe sposoby odprowadzania wód deszczowych. Bydgoszcz: Oficyna Wydawnicza Projprzem-EKO, 1999 6. Miffin W., Polluted urban run-off: a source of concern; 1997 7. Minesota stormwater manual, 2005 Available at: http://www.pca.state.mn.us/water/stormwater/stormwatermanual.html 8. www.eco-guide.net 9. http://en.wikipedia.org/wiki/Amenity 10. http://en.wikipedia.org/wiki/Sustainable_urban_drainage_systems 11. www.greenroof.se 12. http://images.google.dk/imgres?imgurl=http://www.webcomsystems.co.uk/help/ima ges/Ring_soakaway.gif&imgrefurl=http://www.webcomsystems.co.uk/help/pcconc. htm&h=382&w=510&sz=9&hl=da&start=1&sig2=cTPb1aLatOf5BY14aOwDQ&um=1&tbnid=Aqk47M8WCMD8kM:&tbnh=98&tbnw=131&ei=NBJWSJPn LZXIwgGA-n1CQ&prev=/images%3Fq%3Dsoakaway%26ndsp%3D20%26um%3D1%26hl%3 Dda%26client%3Dfirefox-a%26rls%3Dorg.mozilla:en-US:official%26sa%3DN 13. http://www.rfcity.org/Eng/Stormwater/YourProperty/YourProperty.htm 14. http://www.scotland.gov.uk/Publications/2001/07/pan61 15. http://www.webcomsystems.co.uk/help/pcconc.htm 16. Interview and brochures from Augustenborg Botanical Garden

8. Appendix 8.1. Harmful substances and its treatment in soils As water from rainfall and snowmelt flows through the landscape, it picks up and carries contaminants from many different sources. 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 the underground drinking water as it soaks into the ground.

Pollution of urban run-off The urban run-off 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 run-off also toxic pollutants as metals, pesticides and other chemicals can be detected. “Conventional” pollutants z

Sediment

Mix of sediment produced 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. z

Nutrients

Run-off 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. z

Oxygen Demanding Material

Urban run-off carries organic material such as pet waste, leaves, grass clippings and litter. Run-off from older residential areas (with more pavement, more pets, and combined storm and sanitary sewers) carries the highest load of oxygen demanding materials. z

Bacteria

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

Toxic Pollutants z

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 an aquatic life. The primary source of many metals in urban run-off 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. z

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. z

Other Chemicals

There are many other potentially toxic chemicals found in urban run-off. 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. 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, foetal abnormality development, immunity to disease, and problems with liver functions).24

24 Miffin W., Polluted urban run-off: a source of concern; 1997.

There is close linkage between waste handling and water conservation.25

Soil as a filter, buffer and converter In case of transportation of harmful substances by stormwater soil works as a filter. When infiltration is slower there is better water purification (water movement through smaller pores allow soluble substances or sediments to attach to soil particles). With faster infiltration substances contained by water may be transferred deeper.26

Harmful substances treatment in soils

Mechanical, physiochemical and microbiological processes that occur in soil. 27 25 A green Vitruvius – Principles and Practice of Sustainable Architectural Design. James & James, 1999, p.53 26 Geiger Wolfgang, Dreiseiltl Herbertl, Nowe sposoby odprowadzania wód deszczowych. Bydgoszcz: Oficyna Wydawnicza Projprzem-EKO, 1999. 27 Geiger Wolfgang, Dreiseiltl Herbertl, Nowe sposoby odprowadzania wód deszczowych. Bydgoszcz: Oficyna

8.2. City â&#x20AC;&#x201C; soil and water conditions Together with urban development sealing of the surface increases which changes proportions of the stormwater that evapotranspire, flow on the surface and infiltrate.

Proportions in stormwater distribution depending on sealing of the surface (level of the development).28 Generally, in cities transpiration and infiltration is smaller while velocity and surface flow is higher comparing to non-sealed, vegetation covered areas. Water capacity and evaporation of sealed surfaces is smaller, surface flow is quick and it may cause floods.

Infiltration, evapotranspiration and run-off have different proportions in natural areas and developed areas29

Wydawnicza Projprzem-EKO, 1999. 28 Dunnett N., Clayden A. Rain Gardens - Managing water sustainably in the garden and designed landscape; Timber Press 2007 29 Adapted from: Geiger Wolfgang, Dreiseiltl Herbertl, Nowe sposoby odprowadzania wĂłd deszczowych. Bydgoszcz: Ofic. Wyd. Projprzem-EKO, 1999.

Impervious urban surfaces:30 z

speed up stormwater run-off

reduce natural evaporation

cause soil erosion in landscaped areas and the banks of natural waterways

more constructions (drains, culverts, embankments) are needed to prevent

flooding Dynamics of surface flow depends on location and slope of individual surfaces. Flow is higher when sealed surfaces are bigger and connected. However, some compensation may be achieved by small, sealed surfaces frequently changed with permeable ones.31 Flood as a result of urbanisation32 At the beginning of the 20th century with town expansion and industrialisation some epidemics broke out in European cities. It was discovered that it has a connection with a lack of stormwater channelling and sewage/waste purification. The chance was seen in the quick and joint channelling of (a) stormwater and (b) sewage from household and industry. The construction of the sewage system seemingly provided unlimited city and industry development. Geiger and Dreiseitl prove that there is close linkage between surface sealing and overflood. Surface sealing in the area of small rivers substantially raises flood wave (quickened outflow in case of flood is difficult to get under control).

30 A green Vitruvius – Principles and Practice of Sustainable Architectural Design. James & James, 1999, p.41 31 Geiger Wolfgang, Dreiseiltl Herbert, Nowe sposoby odprowadzania wód deszczowych. Bydgoszcz: Ofic. Wyd. Projprzem-EKO, 1999. 32 Geiger Wolfgang, Dreiseiltl Herbert, Nowe sposoby odprowadzania wód deszczowych. Bydgoszcz: Ofic. Wyd. Projprzem-EKO, 1999.

Vegetation and surface run-off z

enhance groundwater recharge through increased absorption;

reduces downstream flooding by virtually eliminating surface water run-off;

improves water quality through filtering of dirty water and slowing of surface

water velocity33

Vegetation reduces surface run-off and prevent erosion.34

33 34

A green Vitruvius â&#x20AC;&#x201C; Principles and Practice of Sustainable Architectural Design. James & James, 1999, p.57 A green Vitruvius â&#x20AC;&#x201C; Principles and Practice of Sustainable Architectural Design. James & James, 1999, p.52