RE-IMAGINING COPENHAGEN STREETS URBAN ECOSYSTEMS 2009 UNIVERSITY OF COPENHAGEN BECKY NEWISS BO HOLM-NIELSEN JENNIE MANSSON MARK SHILTON MIA PERSSON MIKKEL ZOFFMANN JESSEN
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RE-IMAGINING COPENHAGEN STREETS
INTRODUCTION
SECTION 1
INTRODUCTION 1.1 ABSTRACT
1.2 INTRODUCTION
The effects of climate change are becoming increasingly evident in the urban environment. In recent years more regular and intense rainfall events are resulting in the failure of combined sewer systems, which overflow with unmanageable volumes of stormwater runoff. It is expected that these rainfall events will continue rising, both in amount and intensity over the next one hundred years
This report aims to address stormwater management in the urban context and to offer sustainable and viable alternatives to combined sewer overflows. It will focus on implementing ‘zero solutions’ that disconnect residential areas from existing water systems and to demonstrate how stormwater can be managed locally, with the added potential of enhancing biodiversity and recreational value to the area.
At the same time urban growth has increased the use of impermeable surfaces. As a consequence there is less water infiltration and evaporation, putting pressure on existing sewer systems and resulting in flooding of urban areas. Water bodies receiving excess stormwater overflow are gradually eroded, leading to further flooding and habitat damage.
The report will site its study within the Vanløse city district, west of Copenhagen city centre. It will focus on a specific site chosen for its suitability for implementing a ‘zero solution’ that disconnects stormwater runoff from the combined sewer system.
Combined sewer systems also fail to filter urban pollutants from surface runoff, further exuberating the damaging effects of stormwater. To solve the problem associated with combined sewer overflows it is necessary to provide alternative solutions to stormwater management.
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1.3 OBJECTIVES
1.4 METHODS
The overriding objectives for Re-imagining Copenhagen Streets are:
SITE ANALYSIS Site Selection: • Discussion and description of chosen site
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To disconnect the chosen site(s) from the existing combined sewer system.
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To provide a ‘Zero Solution’ for managing storm water runoff locally.
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To offer an example of an effective ‘Zero Solution’ to storm water management in a typical residential scenario that will inform future sustainable development.
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To provide ‘Plan B’ solutions that respond to twenty year rain events.
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To enhance the recreational and aesthetical value of the area as well as improving biodiversity.
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To treat and improve storm water runoff quality locally and by sustainable methods.
Site Survey and Analysis: • Green and blue areas • Land use and density • Infrastructure and traffic load • Measuring reduced area runoff and flood risks • Topography • Soil type, ground water level, infiltration suitability, drinking water interests, soil pollution • Cultural heritage and sensitivity to change Conclude with a SWOT analysis informed by the site survey and analysis: • Strengths • Weaknesses • Opportunities • Threats/Challenges
To improved ‘liveability’ of the road space and promote stakeholder ownership in the proposed systems. RESEARCH Sustainable Stormwater Design Principals: • Desk study and background reading for technical knowledge, inspiration and references. • What is sustainable stormwater design? What are the design principals?
DESIGN OPTIONS Possible Solutions: Applying knowledge to chosen site • Frame: What is the challenge? • Site specific objectives: What do we want to achieve? • Options: What are the possible solutions?
DISCUSSION Suggested Solution: • Priority: Which solution do we recommend for Vanløse and why? • Relate and criticise our work against other findings
CONCLUSION • Report conclusion
1.5 EXPECTED RESULTS The overriding expected results for Re-imagining Copenhagen Streets are: •
An effective combined sewer disconnection and ‘Zero Solution’ to storm water management that can be applied to similar residential scenarios.
•
Technical knowledge and understanding of SUDs and contributing factors.
Case Studies: • Research into existing examples of SUDs in new developments - Malmo Western Harbour and Monnikenhuizen • Research into existing examples of SUDs in retrofitted developments Portland Streets and Augustenborg 5
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RE-IMAGINING COPENHAGEN STREETS
SITE ANALYSIS
SECTION 2
SITE ANALYSIS 2.1 SITE SELECTION VANLØSE CITY DISTRICT Vanløse is a residential area within the Harrestrup Å catchment west of Copenhagen City Centre. Vanløse is one of the 15 administrative, statistical, and tax city districts comprising the municipality of Copenhagen, Denmark. It lies on the west border of the municipality. With approximately 36,300 inhabitants, Vanløse is the municipality’s smallest district in terms of population. It covers an area of 6.69 km² and has a population density of 5,406 per km². Vanløse has the qualities of a village and a major city. For example, public transport is good and there are a number of green and recreational areas. Vanløse is traditionally a district to live in but not work in. The green and recreational areas in Vanløse are one of the district’s strong points and offer many opportunities for the local inhabitants. These areas provide space to move around in, to have all sorts of experiences, informal encounters and rural experiences. Vanløse offers some challenges with regard to strengthening the urban space and increasing the efforts made to keep the district clean. Vanløse has many large roads with a lot of traffic and is crossed by the longest regional highways. This offers a number of environmental and health challenges: air and noise pollution for example, traffic safety, safe roads and better conditions for non-motorised road users. Information obtained from www.kk.dk
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SITE SELECTION After comprehensive visits to the Vanløse area two sites emerged with potential for a disconnection and to implement a stormwater management scheme. One site is a highly trafficked junction and the other is a quiet residential street. Both sites offer a ‘typical’ residential scenario that can be found within most urban areas. These sites have the potential to offer an example of a best-practice ‘Zero Solution’ to storm water management that will inform future sustainable development.
Bellahøvej Junction
To define the scope of this report it is required to focus specifically upon one of these sites to deliver a comprehensive and robust zero solution within the available timeframe.
Ådalsvej
Each site supports a different emphasis. Bellahøvej Junction requires a response that addresses; • Large expanses of impermeable surfaces • A substantial catchment area • Large volumes of stormwater runoff • Complex traffic conditions • Significant heavy pollutants • Pedestrian and cyclist accessibility • High density urban form
The area alone would be complex to disconnect due to its indefinable boundary and numerous uncontrollable parameters. This scenario would orientate around maintaining traffic circulation while stormwater management may become a secondary concern for the site, thus the response generated would be predominately function led. It would difficult to create a true representation of a zero solution. The residential street Ådalsvej requires a response that addresses; • Streetscape arrangement • Identity • Aesthetics • Liveability and recreation • Biodiversity • Private stakeholders • Localised stormwater runoff • Minor pollutants This scenario has the potential to be a creatively led response that would generate a feasible zero solution. The scale of this site provides the opportunity to focus in greater detail into the specification of stormwater management systems. There is the scope to enhance the liveability and aesthetic of the street whilst creating a sustainable and ecologically diverse environment.
Bellahøvej Junction
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SITE DESCRIPTION - ÅDASLVEJ
Grøndals Parkvej
Ådalsvej
Ådalsvej gradient
Ådalsvej from Grøndals Parkvej
Private Gardens
On-street parking
High density living
Pavements
Private off-street parking
Grøndals Parken swale
Private off-street parking
The chosen site for this report is Ådalsvej. Ådaslvej is a typical neighbourhood street consisting predominantly of single family homes as well as a number of multi-storey apartment blocks. Intersecting Ådaslvej is a series of other similar residential streets and Sallingvej, a major arterial road. Most houses have individual private gardens with off street parking facilities and all apartment blocks have private car parking areas. Large amounts of cars still however, park on the street. The road is of asphalt construction and 6m wide. Along its entire length are footways situated on both sides. These consist of asphalt and block pavers. In total the street is approximately 10m wide. The street has a predominant slope to the south east, leading down to Grøndals Parkvej, another major road and Grøndals Parken, a green corridor that passes through a large section of Vanløse. This green corridor serves as an important green link and a valuable recreational and ecological asset. It also contains a temporarily wet swale.
Ådalsvej typical view of street
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Ådalsvej
Ådalsvej
Aerial view of Ådalsvej
Site location within greater context of Vanløse
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2.2 SITE SURVEY AND ANALYSIS
Green and blue areas + Topography
ANALYSIS OF PHYSICAL CONSTRAINTS •
Vanløse, like the majority of Denmark is situated upon Moræneler (clay) soil. The green corridors located around the area comprise of Ferskvandstørv (peat) soil.
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Ground water levels in Vanløse are more than 3m. For this reason it makes infiltration possible.
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However, Ådalsvej is located within an area of drinking water interest. This makes infiltration not possible unless all runoff water is sufficiently filtered and cleaned.
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The Green corridor areas located around Vanløse are historically wetland. Directing water into these areas could recreate wetland habitats. However doing so would be a controversial from the municipality’s perspective as it will have effects on recreation and maintenance.
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The sewer system used around the majority of Copenhagen, including Vanløse is a combined sewer system. Creating a zero solution would provide relief to this dated system.
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Urban areas around Vanløse have been concluded as being ‘maybe suitable’ for infiltration. Ådalsvej is located within this specified area meaning that infiltration is not recommended, however it is not prohibited.
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Public grenspace Private grenspace
ANALYSIS OF GREEN AND BLUE AREAS AND TOPOGRAPHY
ANALYSIS OF HISTORICAL CONTEXT
Ådalsvej slopes 4m from Sallingvej in the north west to Grøndals Parkvej in the south east. The area is mainly private houses with private gardens. There are some public areas adjacent to Ådalsvej and to the south there is a green belt called Grøndals Parken which follows the railway. This green belt has a small stream that leads towards Ladegårds Å and lake Damhussøen. There is also a temporary wet swale. Grøndals Parken is one of the primary recreational areas in Vanløse and serves as an important green connection through the area.
The historical map shows the area of Ådalsvej and Grøndalsåen around 1842-1899. The area was mainly agricultural with small settlements. Several ditches drained the surrounding farmland into the Grøndals Å. The banks of Grøndals Å is characterized as meadow. This map demonstrates that Grøndals Parken was historically a wetland. Today water passing though the park has been canalised underground.
ANALYSIS OF DENSITY Most of Ådalsvej and the nearby streets consist of single family houses. The density is low and the houses are detached with private gardens. Ådalsvej is a residential street and mainly used by the inhabitants. The street has two lanes with space for car parking although most houses have private car parking areas on their own yard. Within the immediate surroundings of the street there is a school and football field. The density at this site is low. In addition to single family houses, apartments dominate the northern end of Ådalsvej and its surroundings. The buildings are multistory and the density on the site is higher than at the smaller private single family houses, the area is mainly dominated by buildings and paved surfaces. The green courtyards and fore courts give additional space to the compact apartment blocks. The density around the junction where Sallingvej intersects Ådalsvej is high and lack of greenery is obvious. The site is dominated by heavy traffic, mainly cars, and the road has four lanes. Density Analysis Diagram
Infrastructure Analysis Diagram ANALYSIS OF INFRASTRUCTURE AND EXISTING PROFILE Ådalsvej is surrounded by two highly trafficked roads, one of which crosses Ådalsvej. Since Ådalsvej is a smaller street the traffic levels are low. There are biking lanes in the surrounding area and a railway in the south.
Existing Road Profile Diagram
The street of Ådalsvej is approximately 10m wide between the front boundaries of residential properties. This includes a road width of 6m which is asphalt and two pavements of 2m which are covered with large pavers, small setts and asphalt. The distance from house to house is approximately 25m. These distances vary along Ådalsvej. Most houses have a large private front garden with their own parking facilities. Only a few cars park on the street. 13
ANALYSIS OF SURFACE RUNOFF This drawing illustrates the various types of surfaces that convey water around Ă…dalsvej. The table shows the total reduced runoff areas of these surfaces. These areas will be used to inform the calculations for storage capacities required for specified stormwater management systems.
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Topography has also been considered in these surface area calculations. Therefore streets that intersect Ă…dalsvej have been included in the total reduced surface area. This means that all proposed systems will also manage all water entering the street by surface runoff.
2.3 SWOT ANALYSIS STRENGTHS:
OPPORTUNITIES:
THREATS AND CHALLENGES:
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The site is cross section of a typical residential area.
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To create an exemplar model for future sustainable developments.
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How to manage and clean water before it re-enters the water cycle.
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Low traffic volumes with low pollutant runoff.
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To create a unique identity for Ådalsvej.
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How to create an effective use of the limited available space.
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Large areas of permeable private green space.
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To create an improved streetscape arrangement that addresses function, safety, traffic flow, pedestrian and cyclist movement.
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How to manage water at major road junctions.
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Large amount of tree canopy cover.
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How to justify infiltration systems against opposing municipality recommendations.
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How to accommodate a Plan B 20 year rain event.
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How to create solutions that are sensitive to place and to the stakeholders concerns.
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Localise stormwater catchment area clearly defined by street layout. Variety of stakeholders within the local residential population. Sloping topography reduces the likelihood of localised flooding.
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• •
Conflict over the suitability to infiltrate considering the ground water level, soil pollution and drinking water interests.
To improve biodiversity possibilities.
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To improve liveability and recreational possibilities.
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To utilise the variety of the built densities and surrounding semi-private spaces.
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To utilise nearby green spaces for Plan B scenarios.
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To utilise the topography to direct the flow of stormwater.
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To involve local stakeholders and encourage local ownership.
WEAKNESSES: •
To create synergy between streetscape functions and streetscape aesthetics.
Restricted available public space – small scale, long and narrow streets. Large areas of impermeable public and semi-public space.
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RE-IMAGINING COPENHAGEN STREETS
RESEARCH
SECTION 3
RESEARCH 3.1 SUSTAINABLE STORMWATER DESIGN PRINCIPALS
THE GOALS OF SUSTAINABLE WATER MANAGEMENT Sustainable water management aims to mimic natural hydrological functions and should aim to achieve the following three goals to the greatest extent possible.
THE EFFECTS OF URBANISATION An undisturbed landscape has the ability to capture, absorb and slow the movement of rainwater when it reaches the ground. However urbanisation disturbs this natural and healthy watershed, reducing the landscape’s absorptive capabilities as well as introducing pollutants.
Improve runoff quality: Stormwater facilities should filter and remove excess sediments and other pollutants from runoff. By allowing water to interact with plants and soil, water quality improvements are achieved through a variety of natural physical and chemical processes.
The problem is exacerbated when increased stormwater runoff from urban environments reaches a steam or river that is not capable of handling such high flows. As a result significant erosion and degradation occurs, often resulting in flooding and damage to natural habitats and biodiversity.
Reduce runoff velocity: Stormwater facilities should slow the velocity of runoff by detaining stormwater in the landscape. Conveying runoff through a system of naturalized surface features mimics the natural hydrological cycle and will protect receiving streams and rivers from erosive flows of stormwater runoff.
The following principles of approaching Sustainable Stormwater Design are derived from the San Mateo County Sustainable Green Streets and Parking Lots Design Guidebook and can be transferred in the development of a ‘zero solution’ water managament strategy for Adelsvej
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Reduce runoff volume: Whenever possible, facilities should collect and absorb stormwater to reduce the overall volume of runoff. Retention facilities offer long-term stormwater collection and storage for reuse or groundwater recharge. Plants contribute to retention capacity by intercepting rainfall, taking up water from the soil, and assisting infiltration by maintaining soil porosity. Volume reduction does not require stormwater facilities to be extremely deep. In fact, it is usually best to employ a highly integrated and interconnected system of shallow stormwater facilities.
LEVELS OF GREEN STREET DESIGN The San Mateo County Sustainable Green Streets and Parking Lots Design Guidebook defines a five level scale for classifying the extent of which a site manages stormwater runoff. Each level encompasses all elements of preceding levels as well as including additional elements of stormwater management. Level 1: Maximise the utilisation of permeable surfaces and minimise the overall impermeable surface area as much as practically possible. This can be categorised as a passive system. Level 2: Add significant tree canopy to the landscape to capture rainfall and provide root uptake. Level 3 : Include landscape systems such as vegetated swales and rain gardens which actively capture and manage rain water at the source. Level 4 : Provide focus on accommodating alternative, more environmentally friendly forms of transportation such as cycling, walking and mass transit in order to reduce runoff pollutants and create a more liveable street environment.
STORMWATER MANAGEMENT STRATEGIES The San Mateo County Sustainable Green Streets and Parking Lots Design Guidebook provides a summary of strategies that can be applied to a site. These strategies are categorised into two types: Site layout strategies: Ways that a site can be designed more efficiently in order to create additional landscape space. These are considered as passive methods of stormwater management. Site layout strategies include: • Providing efficient site design • Balancing parking spaces with landscape space • Utilizing surface conveyance of stormwater • Adding significant tree canopy • Providing alternative transportation options Stormwater facility strategies: Methods of actively managing stormwater through landscape systems which actively capture and manage stormwater water at the source. Stormwater facility strategies include • Pervious Paving • Vegetated Swales • Infiltration and Flow-Through Planters • Rain Gardens • Stormwater Curb Extensions • Green Gutters
Level 5 : The ‘greenest’ and most difficult approach to sustainable rainwater management which integrates public and private space as a whole system. Runoff from the street is managed within private gardens and visa versa if necessary. As a result the system is efficient and aesthetically coherent. It is desirable to achieve the highest level possible in a sustainable water management strategy. However this can be constrained by a multitude of site specific issues which are mostly related to retrofitted scenarios. In these situations, a maximum of level 3 may be realistically achieved, whereas in new developments there may be opportunities to reach levels 4 or 5.
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3.2 CASE STUDY - MALMÖ WESTERN HARBOUR Western harbour in Malmö was built in 2001 to be a leading example of sustainable urban development during the housing fair Bo01. Today the area is a popular, attractive and environmentally friendly neighborhood. Several awards have been appointed to the area, while Västra hamnen has had a profound effect on ecological sustainable development in Malmö. The sustainable urban development is based on an area of dense energyefficient homes and environmentally friendly traffic where pedestrians and cyclists are prioritised over motorists. The greenery, biodiversity and water management were the starting points during the planning process. The area is supplied by local renewable energy where solar, wind and water energy are the main sources but also the residents’ food waste is used as energy after being converted into biogas. The buildings are in addition to its unique architecture also built to be energy-efficient both in heating and electricity.
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Western harbour was planned to be socially and ecologically sustainable. Through access to greenery and water, the procurement of natural light and variation in visual and auditory impression it created an environment for people to thrive in. In order to gather as much greenery as possible a system was introduced which consists of the entire paved surface (i.e. the surface where no infiltration takes place or nor vegetation exists) that are added to the site will be offset by as much green space. The new green areas can be green roofs, climbing plants, dams, etc. This is the Western harbour a prime example of how surfaces can be used to create green spaces and many of the area’s roof and walls are clad in vegetation. Stormwater on the site is taken care of locally and makes use of open stormwater channels and green roofs. Any water is delayed, cleaned or reused by run- off systems.
Since Western harbour was previously industrial area there is a relatively low infiltration into the ground. Most of the ports of stormwater channels go on into ponds and other vegetation where the water can be purified or absorbed by plants. Thus avoiding pollution of water by any heavy metals and no pollutions spread down to the groundwater from the contaminated soil. Several fountains are in the area where stormwater is pumped and used as assembly points for stormwater. The water is treated, in other words as a loop that circulates in the area. Sedum roofs are used to slow the water coming down to the stormwater channels so that these should not be overstressed. At very high rainfall the amount of water is able to increase in the central salt-water canal and during drought the canals are filled with water from the municipal water network.
3.3 CASE STUDY MONNIKENHUIZEN Monnikenhuizen is located in Arnhem on the former grounds of the Vitsse football club. The housing area was build in the years 2000-2002 and holds 204 houses. Four offices were responsible for the architecture; Atelier Z, Meyer en Van Schoten Architects, Van de Looi en Jacobs Architects en Vera Yanovshtchinsky Architects The grounds are very unique for the Netherland with a high sloping terrain. The area is divided in to two rooms, a large and a small to create a green, ecological, corridor in between. Four terraces were constructed in the large room in order to cope with the height differences. In the small room villas are places in the existing terrain.
Water and plantations All runoff water from roofs and roads are exposed and functions as an architectural element. The water is led though a system of large gutters in the pavement to an infiltration basin. These gutters also functions as speed ramps to slow down traffic in between houses. In case of overflow from the basin water is let to the nearby green corridor The streets have a profile that leads water to the adjacent plantings of birches. The plantings are interwoven in the urban structure and keep an overall green character for the whole site. Oaks are planted in the green corridor to connect with the surrounding woodlands and to cope with the overflow scenarios form the basin. References: Monnikenhuizen Article Luebbers Monnikenhuizen Article Yearbook
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3.4 CASE STUDY - PORTLAND STREETS In 2001 the Sustainable Infrastructure Committee in Portland, Oregon was formed to investigate options of sustainable stormwater management in the city. Shortly thereafter a sustainable storm water management program was formed and a couple of streets in the city were retrofitted with green stormwater areas. Portland is today a leading city when it comes to integrating site-specific sustainable stormwater solutions. The city has won several awards for its BMP (best management practices ) project designs, and its municipal program is highly regarded worldwide. The program is continuously developing and new BMPs are still established in the city. The new green initiatives that have been installed for stormwater management are green streets and green roofs.
Green planter strips
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Green Streets A green street is where vegetated facilities are used to manage stormwater runoff at its source. The overall principle of the construction is to store the stormwater runoff so that the pollutants can be captured. The green streets in Portland consist of landscaped curb extensions, swales, planter strips, pervious pavement, and street trees to intercept and infiltrate stormwater. The different infiltration areas in the streets are linked so if the first planter or swale overflows the water will just flow to the next infiltration area. The plants that are used, wich are different types of grass, trees and shrubs, are narrow to fit in the sidewalk space and they change appearance with the season to provide an aesthetic aspect to the street. The new formation of
Green planter strips, won an American Society of Landscape Architects Design Award in 2006.
A channel that cuts into the curb
the streets does not only take care of and clean the stormwater they also beautifies the surrounding, provide habitats, strengthens the local economy and creates safer streets. Green roofs Many buildings in Portland are provided with a green roof to decrease the runoff. The vegetated roofs also offer aesthetic, better air quality and habitats. In 2007, the City Council approved a resolution, report, and policy to officially promote and encurage the use of green street facilities in both public and private development.
Landscaped curb extension
Swale that collects parking lot run off
3.5 CASE STUDY - AUGUSTENBORG
Courtyard Pond
Green Roof
The courtyard pond can store 570m3 water and will overflow to an adjacent area when water level reaches the pathway
The extensive green roof is 2-5 cm thick and can be installed on existing roof constructions due to the relatively little weight. The plants are draught tolerant and need very little mantanence.
Augustenborg is an inner-city high density housing area build in the 1940´s. In 1997 Augustenborg became part of Eco-city project in Malmø, with special attention on storm water management and social rehabilitation. Case Study Area
Main Channel and Miniature wetland
Showing compartment B1, B2, C and D STRATEGY The storm water management was implemented as a series of SUDS elements interconnected to work as one system. Since infiltration and deep peculation was not an option the system is based on evaporation and evapotranspiration, by detaining and retaining storm water. This case study focuses on a smaller part of Augustenborg marked on the diagram as area B, C and D and involves elements as green roofs, open channels, dry and wet ponds and wet lands.
The 170m long main channel interconnects the different compartments with the courtyard pond. Approximately midtway a miniature wetland is installed
CONCLUSIONS The main conclusion is that the different elements minimize the total outflow from the area by retaining the storm water in the different ponds and wet lands. The combination of ponds/wetlands and channels decreases the peak inflow in the different elements during storm events. For instance storm water from area C and D lead into small ponds before it runs through the main channel to the court yard pond which is the main storage capacity. Green roofs in area D obtain approximately 10 mm water during rain events but do not seem to be very effective in delaying water flow during heavy rain events. MAJOR CHALLENGES The lack of useful space has been a major challenge in the project. In area D the need for parking space determined the size of the open channel and basin. Green roofs were implemented to support the drainage system. The lack of space for large drainage systems between houses in area C and B in combination with unsuitable roofs for green roofs resulted in a design draining water to the large courtyard pond. 23
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RE-IMAGINING COPENHAGEN STREETS
DESIGN OPTIONS
SECTION 4
DESIGN OPTIONS 4.1 INTRODUCTION This report could have two possible directions. One direction could be ‘product orientated’ where the report aims to produce one design solution for Ådalsvej. This would involve exploring the range of scenarios the site presents, suggesting concept solutions for each and then deciding on the ‘ideal’ or most realistic scenario and detailing one comprehensive solution. The problem with this direction is that the ‘ideal’ scenario is made up of our presumptions, we are deciding the constraints which gives an unrealistic conception and the proposed solution may not be a true reflection of the site’s situation and needs. The report would be very site specific. The other direction would be ‘research orientated’ where the report aims to produce a range of design solutions for Ådalsvej. This would involve exploring the range of scenarios the site presents and suggesting a heavily detailed and comprehensive solution for each. This direction would not only create a variety of solutions for Ådalsvej but a framework of solutions that could be applied to other residential streets.
For Ådalsvej it is important to analyse the range of scenarios the site presents and suggest various related solutions. One of the most important arguments for this report is whether infiltration is possible on this site or not. As discovered in our site analysis ground water levels are >3m and for this reason makes infiltration possible. However, Ådalsvej is located within an area of drinking water interest which makes infiltration not possible unless all runoff is sufficiently treated. Grøndals Parken historically is a wetland and directing water here could recreate wetland habitats. However doing so would be a controversial from the municipality’s perspective as it will have effects on recreation and maintenance. 26
Overall it has been concluded that urban areas around and including Ådalsvej are ‘maybe suitable’ for infiltration, meaning that infiltration is not recommended, however it is not prohibited. Therefore this report will suggest solutions with the possibility of infiltrating and suggest solutions with no infiltration possibilities. After exploration the priority solution will support one of or a mixture of these scenarios. The other important argument for this report considers the available space. Public space is considered the space from one residential boundary to another hence the road, pavements and any other left over space. Public space is considered readily available and it will be presumed that it can be changed. Private space is considered the area within a residential boundary, this includes gardens and roofspace. Where private space is used it is presumed that there is 100% stakeholder involvement and they are happy to include stormwater systems within their land boundary. Realistically this isn’t something that can be taken for granted and there is likelihood that some residential plots will not being suitable for the suggested interventions e.g. the existing roof can’t support a green roof or the garden is too small for a rain garden etc. Therefore, to make this report more realistic it is stated that 70% of residential plots on Ådalsvej can support the suggested interventions. This means, for example, that some residential plots will have a rain garden, a swale or a green roof etc, some houses will have all interventions and some houses may have none. As long as for each suggested solution there is 70% of the residential plots that can support and implement it. There is the argument that some residents would not be happy at adopting these proposals but this would involve asking the individuals and accommodating their wishes which is too specific for a research orientated report. We are to presume there is 100% stakeholder involvement.
Therefore this report will suggest solutions with the possibility of using private space and suggest solutions with no private space use possibilities. With these two constraints four solution scenarios have been created: •
SOLUTION 1: The use of public and private space with the possibility to infiltrate.
•
SOLUTION 2: The use of public space with the possibility to infiltrate.
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SOLUTION 3: The use of public and private space with no infiltration possibilities.
•
SOLUTION 4: The use of public space with no infiltration possibilities.
These solutions will focus on the section of Ådalsvej between Sallingvej and Vanløse Allé. Instead of considering the whole street, this small section gives enough physical variety to produce solutions that can be applied to the length of the street. The decision to select this section of Ådalsvej is based upon the following factors: • • • • •
The section is a typical cross section of Ådalsvej. The section deals with three intersecting junctions of various sizes There is a variety of built forms and scales. There is a variety of public and private space. There is a variety of private plot scales.
4.2 STORMWATER VOLUMES The suggested solutions are accommodating water from roof runoff, garden runoff and street (road, pavements and car parks) runoff. These volumes will be applied to all four solutions. To be able to size the sustainable urban drainage systems accurately the total area of the different surface types is required. A reduced area can then be calculated using the run-off coefficients for different surfaces. See Figure 1 and corresponding table. The stormwater volumes generated by various rain events can then be calculated and used for sizing SUDS. When sizing SUDS the standard rain events used for calculations are 0.2, 5 and 20 year rain events. As the solutions will focus on either infiltration or no infiltration possibilities, calculations that use different rain durations are also required. For infiltration and non-infiltration storage systems rain durations of 120 minutes are required as a basis of calculation. However for non-infiltration transport systems a rain duration of 10 minutes is necessary.
Figure 1: Total areas and reduced areas plan Roofs Total Area m 7991 Reduced Area m2 7991 *Road and pavement 2
(co-ef 1.0)
Street* 6887 6198
(co-ef 0.9)
Car Parks (co-ef 0.9) 1265 1139
Gardens (co-ef 0.1) 6921 692
Combined Total 23064 m2 16020 m2
Storage volumes required for non-infiltration transport systems for the focus section of Ådalsvej
Storage volumes required for infiltration and non-infiltration storage systems for the focus section of Ådalsvej
Storage required for a 0.2 year rain event (Normal heavy) Volume = Reduced Area x Time x Rain Intensity V = Ared * tr * intensity V = 16020m² x 0.0001m²/ha x 10min x 60s/min x 52 l/s/ha V = 49982l V = 49982l / 1000l/m³ = 50m³
Storage required for a 0.2 year rain event (Normal heavy) Volume = Reduced Area x Time x Rain Intensity V = Ared * tr * intensity V = 16020m² x 0.0001m²/ha x 120min x 60s/min x 11 l/s/ha V = 126878l V = 126878l / 1000l/m³ = 127m³
Storage required for a 5 year rain event (Standard) Volume = Reduced Area x Time x Rain Intensity V = Ared * tr * intensity V = 16020m² x 0.0001m²/ha x 10min x 60s/min x 190 l/s/ha V = 182628l V = 182628l / 1000l/m³ = 183m³
Storage required for a 5 year rain event (Standard) Volume = Reduced Area x Time x Rain Intensity V = Ared * tr * intensity V = 16020m² x 0.0001m²/ha x 120min x 60s/min x 33 l/s/ha V = 380635l V = 380635l / 1000l/m³ = 381m³
Storage required for a 20 year rain event (Extreme event) Volume = Reduced Area x Time x Rain Intensity V = Ared * tr * intensity V = 16020m² x 0.0001m²/ha x 10 x 60sec x 280 l/s/ha V = 269136l V = 269136l / 1000l/m³ = 269m³
Storage required for a 20 year rain event (Extreme event) Volume = Reduced Area x Time x Rain Intensity V = Ared * tr * intensity V = 16020m² x 0.0001m²/ha x 120 x 60sec x 64 l/s/ha V = 738201l V = 738201l / 1000l/m³ = 738m³
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4.3 SOLUTION 1 The use of the public and private space with the possibility to infiltrate. For infiltration systems 5 year rain events with duration of 120 minutes are required to calculate stormwater volumes. In Solution 1 we have three on site interventions: • Green Roofs • Rain Gardens • Vegetated Infiltration Channels
1. Extensive green roof, small rain garden and vegetated infiltration channel
Runoff that is generated within a residential plot is dealt with by using green roofs and rain gardens. For a realistic scenario it is presumed that some residential plots will not be suitable for the suggested interventions e.g. the existing roof can’t support a green roof or the garden is too small for a rain garden etc. Therefore we have three possible situations. •
•
• •
The first situation is if a residential plot has a green roof then only a small rain garden (4m x 4m) is required to deal with all the water. See figure one. Secondly, if a residential plot does not have a green roof then a larger rain garden (6m x 6m) is required to deal with all the water. See figure two. In the case of a 20 year rain event both rain gardens have an outlet into the street, this can be seen within figures one and two. The third situation is the residential plot only has a green roof. In this case the runoff from the green roof is deposited into the street system. See figure three.
2. Large rain garden and vegetated infiltration channel
3. Green roof and vegetated infiltration channel 28
Green Roof
On site there are 28 buildings, 5 are high density , which are regarded ‘public’, and 23 are individual houses. For the 5 high density buildings we have sized individual rain gardens to accommodate the total runoff for each building as they differ in size quite considerably. For the individual houses we have found the average roof area as they only slightly differ in size. For this research orientated approach it would be beyond the remit of this report to work out the size of the rain garden for each individual house.
Rain Garden
Runoff that is generated within the streetscape is combined with runoff from houses without a rain garden. This combined runoff is dealt with by using vegetated infiltration channels. The channel is a 50mm wide depression that is found on either side of the road. It has a vegetation layer which has storage capacity for heavier than normal rain events, then an active soil layer of 50mm followed by an infiltration trench 50mm wide and 150mm deep. The total channel length is 670m. To allow for access small bridges are placed over the trench. Cross section of a rain garden
Vegetated Infiltration Channel
Cross section of a green roof
Cross section of a vegetated infiltration channel 29
SOLUTION 1 CALCULATIONS
H = 90mm
V = 1390l / 1000l/m³ = 1.4m³
CALCULATIONS FOR SYSTEMS WITHIN RESIDENTIAL PLOTS
Houses with a standard roof and a rain garden Standard Roof Runoff: Reduced Area = Co-efficient x Roof area = 1 x 117m² = 117m² Runoff Volume = Reduced Area x Time x Rain Intensity V = Ared * tr * intensity V = 117m² x 0.0001m²/ha x 120min x 60s/min x 33 l/s/ha V = 2780l V = 2780l / 1000l/m³ = 2.9m³
1.4m3 of roof runoff will be deposited in the street per house. 8 houses do not have a rain garden. 8 x 1.4m3 = 11.2m3 will be deposited in the street from these houses.
On site there are 28 buildings, 5 are high density and 23 are individual houses. Average Roof Area= Total roof area of houses / No of houses 2690m² / 23 = 117m² Average Roof Area Houses with a green roof and a rain garden Green Roof Runoff: Reduced Area = Co-efficient x Roof area = 0.5 x 117m² = 58.5m²
Rain Garden Size: Emptying rate = Volume / 24hrs Emptying rate = 2.9m³ / 24hrs Emptying rate = 0.1208 m³/h Emptying rate = 3.4 * 10-5 m³/s
Runoff Volume = Reduced Area x Time x Rain Intensity V = Ared * tr * intensity V = 58.5m² x 0.0001m²/ha x 120min x 60s/min x 33 l/s/ha V = 1390l V = 1390l / 1000l/m³ = 1.4m³
Infiltration Area = Emptying rate / Soil Hydraulic Conductivity (Clay 10-7) Infiltration Area = 3.4 * 10-5 m³/s / 10-7 Infiltration Area = 34 m²
Rain Garden Size: Emptying rate = Volume / 24hrs Emptying rate = 1.4m³ / 24hrs Emptying rate = 0.0583 m³/h Emptying rate = 1.6 * 10-5 m³/s
Volume = Length x Width x Height 2.9 m³ = 6m x 6m x H 2.9 m³ = 36m2 * H 2.9 / 36 = H H = 0.08m H = 80mm
Infiltration Area = Emptying rate / Soil Hydraulic Conductivity (Clay 10-7) Infiltration Area = 1.6 * 10-5 m³/s / 10-7 Infiltration Area = 16 m² Volume = Length x Width x Height 1.4 m³ = 4m x 4m x H 1.4 m³ = 16m2 * H 1.4 / 16 = H H = 0.09m 30
Houses with a green roof but no rain garden Green Roof Runoff: Reduced Area = Co-efficient x Roof area = 0.5 x 117m² = 58.5m² Runoff Volume = Reduced Area x Time x Rain Intensity V = Ared * tr * intensity V = 58.5m² x 0.0001m²/ha x 120min x 60s/min x 33 l/s/ha V = 1390l
Vegetated Infiltration Channel Size: Emptying rate = Volume / 24hrs Emptying rate = 158.2m³ / 24hrs Emptying rate = 6.6 m³/h Emptying rate = 0.002 m³/s
Building A with a green roof and a rain garden Runoff Volume: 11.3m³ Infiltration Area = 130 m² (10m x 13m x 90mm)
Infiltration Area = Emptying rate / Soil Hydraulic Conductivity (Clay 10-7) Infiltration Area = 0.002 / 10-7 Infiltration Area = 2000 m²
Building B with a green roof and a rain garden Runoff Volume: 41m³ Infiltration Area = 240 m² (16m x 15m x 90mm) Building C with a green roof and a rain garden Runoff Volume: 9.3m³ Infiltration Area = 272 m² (4m x 68m x 90mm)
The SUDS element is to be implemented as an infiltration trench with a width of 0.5 m and a depth of 1.5 m Infiltration area per running metre = 2 x 1m x 1.5m = 3m² Trench length = 2000 m² / 3 m² = 665m
Building D with a green roof and a rain garden Runoff Volume: 22m³ Infiltration Area = 260 m² (16.3m x 16m x 90mm)
Trench Volume = L * W * H Trench Volume = 665m x 0.5m x 1.5m Trench Volume = 500 m³
CALCULATIONS FOR SYSTEMS WITHIN THE PUBLIC REALM
The total site run off volume is 158.2 m³ Beach stones = 500 * 0.2 = 100 m³ LECA clay pellets = 500 * 0.5 = 250 m³ Plastic Box = 500 * 0.9 = 450 m³ Therefore LECA clay pellets are suitable fill material for the infiltration trench.
Road Runoff: Reduced Area = Co-efficient x Road area = 0.9 x 6887m² = 6198m² Volume = Reduced Area x Time x Rain Intensity V = Ared * tr * intensity V = 6198m² x 0.0001m²/ha x 120min x 60s/min x 33 l/s/ ha V = 147264l V = 147264l / 1000l/m³ = 147m³ + Plus 11.2 m3 roof runoff from houses that do not have a rain garden. Total Road Runoff = 158.2m3
We need 665m of trench to accommodate 158.2m3 water. Ådalsvej has 670m of available road space for infiltration trenches.
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4.4 SOLUTION 2 The use of the public space with the possibility to infiltrate. For infiltration systems 5 year rain events with duration of 120 minutes are required to calculate stormwater volumes. In Solution 2 we have three on site interventions: • Vegetated Infiltration Channels • WADIs • Rain Gardens
On site there are 28 buildings, 5 are high density, which are regarded ‘public’, and 23 are individual houses. To support the trench and the WADI rain gardens provide a further infiltration intervention. For the 5 high density public buildings we have sized individual rain gardens to accommodate the total runoff for each building.
In solution two we do not have the added benefit of using private space to deal with the stormwater runoff. All generated runoff within the streetscape is a combination of runoff from individual houses and the road. This combined runoff is dealt with by using vegetated infiltration channels. The channel is a 50mm wide depression that is found on either side of the road. It has a vegetation layer which has storage capacity for heavier than normal rain events, then an active soil layer of 50mm followed by an infiltration trench 50mm wide and 150mm deep. The total channel length is 670m. To allow for access small bridges are placed over the trench. Alone, this trench, which can also be seen within Solution 1, will not support the volume of runoff generated, the system requires further infiltration interventions. For this we have suggested the use of a WADI. A WADI benefits from the combination of a vegetated swale which is 300mm wide and 30mm deep and an infiltration trench which is 50mm wide and 150mm deep. The swale component is 135m in length and the trench is 120m. For Ådalsvej we cannot accommodate one long WADI as there are issues with access and streetscape alignment. Therefore there will be 14 smaller WADIs that are 10m in length and 3m wide. The road width is 6m and allows for two lines of traffic, where there is a WADI it will be reduced to 3m only allowing for one line of traffic – by standards this is acceptable on a small residential street. There is ample space between WADIs to allow for cars to pass each other. WADIs are only found on one side of the street to avoid cars zigzagging and to keep a comfortable, constant motion. 32
Cross section of vegetated infiltration channel and WADI
Plan view of vegetated infiltration channel and WADI Rain Garden
Vegetated Infiltration Trench
WADI - Swale with Infiltration Trench
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SOLUTION 2 CALCULATIONS CALCULATIONS FOR SYSTEMS WITHIN THE PUBLIC REALM Total area of Ådalsvej (minus gardens): 16143m2 Total reduced area of Ådalsvej: 15328m2 Total surface runoff volume for 5 year rain event for Ådalsvej: 364m3 From Solution 1 it is proven that 670m * 0.5m * 1.5m of infiltration trench with LECA pellets will accommodate 158.2m3 of stormwater. Also from Solution 1 it is proven that rain gardens within the grounds of public buildings A, B, C and D will accommodate 83.6m3 (11.3m3 + 41m3 + 9.3m3 + 22m3) of stormwater. Building A with a green roof and a rain garden Runoff Volume: 11.3m³ Infiltration Area = 130 m² (10m x 13m x 90mm) Building B with a green roof and a rain garden Runoff Volume: 41m³ Infiltration Area = 240 m² (16m x 15m x 90mm) Building C with a green roof and a rain garden Runoff Volume: 9.3m³ Infiltration Area = 272 m² (4m x 68m x 90mm) Building D with a green roof and a rain garden Runoff Volume: 22m³ Infiltration Area = 260 m² (16.3m x 16m x 90mm) Therefore in Solution 2: 364m3 – 158.2m3 – 83.6m3 = 122.2m3 of stormwater needs to be accommodated in additional systems to the trench and rain gardens. For Solution 2 we are suggesting the use of a WADI to accommodate 122.2m3 of stormwater. We want to 34
manage 50 % of the water in the swale component and 50% in the infiltration trench. Vswale = 50 % * Vtrench = 50 % * 122.2m3 = 61.1 m3 Provided the swale has a width of 3 m and a depth of 0.3 m We use a triangular cross section. The cross sectional area is consequently Asection = ½ * w * d. Length = Vswale / Asection Length = Vswale / (½ * w * d) Length = 61.1 m3 / (½* 3 m * 0.3 m) = 135.7 m The swale has an estimated soil depth of 0.3 m, the soil volume in the swale is: 164.8m3 Soil volume, Vsoil = l * d * w Soil volume, Vsoil = 135.7 m * 0.3 m * 3 m Soil volume, Vsoil = 122.2 m3 This soil volume is expected to soak up 25 % of the runoff, preventing it from reaching the infiltration trench located below the wadi. The water volume retained in the soil is: 30.6 m3 Water volume retained in the soil, Vsoil = 25% * 122.2 m3 = 30.6 m3 The remaining water volume to be managed in the trench within 24 hours is: Remaining water volume, Vtrench = Vtrench - Vswale Vsoil Remaining water volume, Vtrench = (122.2 – 61.1 – 30.6) m3 Remaining water volume, Vtrench = 30.6 m3 Emptying rate = Volume / 24hrs Emptying rate = 30.6m³ / 24hrs Emptying rate = 1.3 m³/h Emptying rate = 3.6 * 10-4 m³/s
Infiltration Area = Emptying rate / Soil Hydraulic Conductivity (Clay 10-7) Infiltration Area = 3.6 * 10-4 m³/s / 10-7 Infiltration Area = 360 m² The SUDS element is to be implemented as an infiltration trench with a width of 0.5 m and a depth of 1.5 m Infiltration area per running metre = 2 x 1m x 1.5m = 3m² Trench length = 360 m² / 3 m² = 120m Trench Volume = L * W * H Trench Volume = 120m x 0.5m x 1.5m Trench Volume = 90 m³ The volume is 30.6 m³: Beach stones = 90 * 0.2 = 18 m³ LECA clay pellets = 90 * 0.5 = 45 m³ Plastic Box = 90 * 0.9 = 81 m³ Therefore LECA clay pellets are suitable fill material for the infiltration trench. Therefore we have a WADI with the swale component at 135m and the trench at 120m that accommodates 122.2m3.
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4.5 SOLUTION 3 Solution 3 practices public –private with no ability for infiltration. Of the 28 houses located at the site there are 23 single family houses that in the suggestion cares for its own stormwater. This requires for all the 23 houses to be engaged in the solution. The other 5 high-density houses and car parks have stormwater being carried out on the street. The suggestion uses four intervention: Green roofs Storage on private gardens Storage and retention on the street Transportation Evaporation
Green roof, storage on private gardens and basin 36
The suggestion for the single family houses is to deal with all the stormwater within the garden. Stormwater on the roof is evaporated and delayed by the use of green roofs. Runoff from this is transported by pipes and collected in a storage tank below ground. The size of the tank is 1m x 1m x 1,4m and the collected water is reused as irrigation, toiletflushing etcetera. Note that the size of the tank is for an average roof area but since the roofs on the private buildings differs in size the size of the tank will also differs accordingly to the roof area. For higher rain events a pipe leads from the storage tank down to the street so that the tank won’t overflow. This is used as a Plan B.
The 5 high density houses can be regarded as public and therefore the runoff is transported from the roofs to the street. Same thing goes for the car parks. Accordingly the runoff from these sites is dealt with on the streetscape. To store and delay the stormwater for the streetscape a solution with vegetated basins is used. The basins are multifunctional and also work as traffic obstacles and are found on both side of the street. To maximize the witdh of the basin a solution containing storage below the pavement is used. Where this occurs a type of pedestrian bridge is applied.
Cross section of a basin with a use of the area beneath the pavement
Channals for water transport
The basins are putt on each side of the street since the street is convex and water will run to both sides. During a rain event the amount of water will be higher at the top of the street, at the first basin. When this basin is filled up channels transport the water down to the next basin and so it continues through the whole street. The basins also have inflow from the street so that the water can come directly from the street down to the basins.
The channels that transport the water are 10 cm wide depressions that can hold a level of 5 cm water. To access the houses and pavement small bridges are placed out crossing over the depression.
Vegetated basin
Irrigation
Inflow to basin from the street
Plan view
Basin
Green roof
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CALCULATIONS FOR PRIVATE NON INFILTRATION STORAGE Using a 5 year rain event with duration of 120min and intensity of 190l/s/ha 23 single family houses Average roof area = 117m2 Green roof runoff: A red = co efficient x roof area = 0,5 x 117m2 = 58,5m2 V= Ared x tr x intensity V= 58,5m2 x 0,0001m2/ha x 120min x60s/min x 33l/s/ha V= 1382,832 l = 1390 l V= 1390 l/ 1000 l/m3 = 1,4m3 Size of storage tank: Dimentions= height x length x width Height= 1,4m3/ 1m x 1m = 1,4m 5 high density houses where the water will flow on to the street without storage Average roof area: Ared total – single family house area A red= 7991m2 – (117m2 x 23) = 5301m2/5 = 1060m2
Standard roof runoff : V= Ared x tr x intensity V= 1060m2 x 0,0001 m2/ha x 120min x 60s/min x 33l/s/ ha V= 25185,6 l = 25200 l V= 25200 l / 1000 l/m3 = 25,2 m3 /house 38
CALCULATIONS FOR PUBLIC NON-INFILTRATING SOLUTIONS
This is not a suitable solution since there has to be room for cars to meet at the site. One solution could be to use other types of storage such as ponds.
Calculations for wet basins Road runoff: V= Ared x tr x intensity V= 6198m2 x 0,0001 m2/ha x 120min x 60s/min x 33l/s/ ha V= 147264,48 l= 150000l V= 150000l / 1000l/m3 = 150m3 Car Park runoff : V= Ared x tr x intensity V= 1139m2 x 0,0001 m2/ha x 120min x 60s/min x 33l/s/ ha V= 27062, 64l = 30000 l V= 30000 l / 1000 l/m3 = 30m3 Total streetscape runoff: V= (25,2m3 x5 houses) + 30m3 + 150m3 = 306 m3 =310 m3 Size of wet basins: V= height x length x width Length= 310 m3 / 0. 6 m x 3m = 172,2 m =173m total
Ideal size of wet basin were the evaporation is the highest: V= height x length x width Length= 310m3 / 0.4m x 3m = 258,33 m = 260 m Length of basin= Length of street – length of basin Length basin= 340m – 260m = 80m road for meeting places
Number of wet basins: 14 or 28 Length of basins(14) = 173m / 14= 12,5m Length of basins(28) = 173m / 28= 6,25(one basin on each side of the road)
For 28 basins: A= length x width A= 18,75m2 = 6,25m x 3m According to the calculations and the conditions at the site 28 basins is the most suitable option. CALCULATIONS ON EVAPORATION Evaporation per day: 3mm /24h = 3 l /m2
Lenght of street: 290m + 67m Cross section: 17m Total road length: 340m Size of meeting points: With basins on one side: 340m road – 173m basin = 167 m road left 14 basins equals 17 meeting points 167m/17 = 9,8 m With basins on each side: 340m road x2 (two sides) -173m basin = 507m road left 28 basins equals 34 meeting points 507m/ 34 =14, 9m
Area for wet basins: A total= Length x width A total= 173m x 3m = 519m2 For 14 basins: A = 519m2/ 14 = 37,5 m2 / one basin A= length x width A= 37,5m2= 12,5m x 3m
A one basin= 18,75m2 Evaporation/ 24h = A x evaporation V evaporation= 18, 75m2 x 3 l/m2 = 56,25 l /day /basin V evaporation=18,75m2 x 0,6m =11,25m3 = 11250 l Duration= 11250 l/ 56,25 l =200 days Volume after evaporation: V = 18,75m 2 x 0,6m = 11,25m3 = 11250 l Evaporation= 18, 75m2 x 3 l/m2 =56,25 l /day /basin V after evaporation/ day= 11250 l – 56,25= 11193,75 l According to the calculations it takes 200 days for the runoff to evaporate. Therefore transportation of the water is necessary.
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4.6 SOLUTION 4 The use of public space for non - infiltration. For dimensioning the system for non – infiltration we need to look at 5 year rain events with the duration of 10 minutes for conveyance systems and 5 year rain events with duration of 120 minutes for storage systems. This gives us the biggest impact on our system. In this solution we have three interventions: • • •
Canals Wet basins Public wet basin
Run off from private housing, roofs and car parks are let to the streets by pipes. Here the water runs into a canal that leads it to wet basins. The canals are located adjacent the road profile and are dimensioned to handle 5 years rain events with the biggest intensity. In case of a 20 year rain event we intent to utilize the road profile as an overflow possibility. The wet basins will be part of both road and pavement. We dimension the width of the basin to be 4,5m this gives us a road width of 4m which is plenty for a car to pass. The basin goes under an overhanging sidewalk, see figure X; this will both be an architectural element for Ådalsvej and give us a larger volume for storing water. The basins are made from concrete and constructed to hold water and wet bed plants. All the basins are connected by the canals with an overflow possibility to the green belt to the south. Roof run off from building A and B is lead into a large wet basin with water plants. The basin is located at the car park area adjacent to building B and can obtain 80m3 of water, which is expected during a 5 year rain event. An overflow pipe connects the basin with channels at the street in order to allow outflow of excess water during an emergency. Building C and D has no individual solutions and runoff is therefore included in the dimensions of the SUDS elements in the street.
40
Large Wet Basin
Wet Basin Along Street
Channel and Vegetated Wet Basin
Open Channels
Access Across Channel
41
SOLUTION 4 CALCULATIONS CALCULATIONS FOR SIZING WET BASINS using a 120 minutes 5 year rain event. Runoff volumes: Roof area exclusive A and B: Total roof area: 7991m2 Roofs A and B: 947m2 + 2357m2 = 3304m2 Roof area: 7991m2 - 3304m2 = 4687m2 Reduced roof area: Ared = Area * runoff coefficient Reduced roof area = 4687m2 * 1 = 4687m2 Reduced road area: 6198m2 (see 4.2) Reduced carpark: 1139m2 (see 4.2) Total reduced area 4687m2 + 6198m2 + 1139m2 = 12024m2
street. Each wet basin therefor has to be: 86m/14 = 6 meters. Sizing wet basin for building A and B: Roof area: 3304m2 Ared: 3304m2 * 1,0 = 3304m2 Runoff Volume = Reduced Area x Time x Rain Intensity V = Ared * tr * intensity V= 3304m2 x 0,0001 m2/ha x 120min x 60s/min x 33 l/s/ ha V= 78503,04l V= 78503,04/ 1000 l/m3 = 80m3 Storage volume = highest volume = 80m Size of storage: Volume= l x d x w V = 10m * 0,8m * 10m = 80m3 Proposed size of wet basin is 10 times 10 meter with a depth of 80 centimeters. 3
Total runoff volume: Runoff Volume = Reduced Area x Time x Rain Intensity V = Ared * tr * intensity V= 12024m2 x 0,0001 m2/ha x 120min x 60s/min x 33 l/s/ ha V= 285690,24l V= 285690,24/ 1000 l/m3 = 290m3 The SUDS storage elements has to accomodate 290m3 of rain water Sizing wet basins along the street: Storage volume = highest volume = 290m3 Size of storage: Volume= l x d x w Width is set to 4,5 m depth is set to 0,75m Length = volume/ d x w l = 292m3/0,75m * 4,5m = 86m The total lenght of the wet basins will then have to be approximately 86meters. We have chosen to construct 14 wet basins along the 42
CALCULATIONS FOR SIZING SUDS TRANSPORT ELEMENTS The relationt between dimensions and flow capacity can be described by following equation: Q = M * R0,67 * A * S0,5 Q is flow rate, M is material friction value, R is the lenght of the perimeter surface, A is the cross sectional area and S is the slope. Pipe connecting single family housing with road: Rain intensity for a 5 year rainevent of 10 minuts duration is 190l/s/ha. Average roof area of single family housing reduced: 117m2 Flow rate(Q) = Rain intensity * Reduced area
Q = 190l/s/ha * 117m2 /10000m2/ha = 2,2l/s The pipe has to accomodate 2,2 liters of rain water per second. Sizing by trial-and-error approach: Pipe with 5 cm diameter, made of plastic and constructed with 0,1% slope: Flow rate(Q) = Material friction value(M) * lenght of the perimeter surface0,67 (R)* Cross sectional area(A) * Slope0,5(S) M = 100, R = π * d = 3,14 * 0,05m = 0,157m A = π * r2 = 3,14 * (0,025m)2 = 0,001963m S = 1m/1000m Q= 100 * (0,157m)2 * 0,001963m * (1m/1000m)0,5 Q = 0,001795m3/s Q = 0,001795m3/s *1000l/m3 Q = 1,8l/s Pipe with 6 cm diameter, made of plastic and constructed with 0,1% slope: Flow rate = Material frictio n value(M) * lenght of the perimeter surface0,67 (R)* Cross sectional area(A) * Slope0,5(S) M = 100, R = π * d = 3,14 * 0,06m = 0,188m A = π * r2 = 3,14 * (0,03m)2 = 0,002826m S = 1m/1000m Q= 100 * (0,188m)2 * 0,002826m * (1m/1000m)0,5 Q = 0,002920m3/s Q = 0,002920m3/s *1000l/m3 Q = 2,9l/s The pipe line has to accomodate 2,2l/s and therefor it is recommanded to use a pipe with a diameter of 6 cm. Road channel connecting wet basins: Rain intensity for a 5 year rainevent of 10 minuts
duration is 190l/s/ha. Total reducedarea: 12024m2 Average reduced area: 12024m2/14 = 859m2 Flow rate(Q) = Rain intensity * Reduced area Q = 190l/s/ha * (859m2/2) / 10000m2/ha = 16,3/s The channel has to accomodate 16,3 liters of rain water per second. The design deals with a channel in each side of the street and thus each channel has to accommodate around 8l/s Sizing by trial-and-error approach: Concrete channel dimensioned 10cm * 5cm, sloping 0,56% Flow rate(Q) = Material friction value(M) * lenght of the perimeter surface0,67 (R)* Cross sectional area(A) * Slope0,5(S) M = 75 R = 0,1m + 0,05m + 0,05m = 0,2m A = 0,1m * 0,05m = 0,005m2 S = 5,6m/1000m Q = 75 * (0,2m)0,67 * 0,005m2 * (5,6m/1000m)0,5 Q = 0,009545867m3/s Q =0,009545867m3/s *1000l/m3 Q = 9,5l/s Concrete channel dimensioned 10cm * 4cm, sloping 0,56% Flow rate(Q) = Material friction value(M) * lenght of the perimeter surface0,67 (R)* Cross sectional area(A) * Slope0,5(S) M = 75 R = 0,1m + 0,04m + 0,04m = 0,18m A = 0,1m * 0,04m = 0,004m2 S = 5,6m/1000m
Q = 75 * (0,18m)0,67 * 0,004m2 * (5,6m/1000m)0,5 Q = 0,007116195m3/s Q = 0,007116195m3/s/s *1000l/m3 Q = 7,1l/s
Q= 100 * (0,1413m)2 * 0,0063585m * (1m/1000m)0,5 Q = 0,008622635m3/s Q =0,008622635m3/s *1000l/m3 Q =8,6l/s
The channel has to accomodate around 8l/s and therefore it is recommanded to have a 10cm wide and 5cm deep channel.
It is recommanded to use a pipe with a diameter of 9 centimeter. Pipe connecting building B to large wet basin Flow rate(Q) = Rain intensity * Reduced area Ared = 2357m2 Q = 190l/s/ha * 2357m2 / 10000m2/ha = 44,8l/s
Pipe connecting west channel with wet basin The pipe has to accommodate the same flow as the channel, which is 8l/s Sizing by trial-and-error approach: Pipe with 8 cm diameter, made of plastic and constructed with 0,1% slope: Flow rate(Q) = Material friction value(M) * lenght of the perimeter surface0,67 (R)* Cross sectional area(A) * Slope0,5(S) M = 100, R = π * d = 3,14 * 0,04m = 0,1256m A = π * r2 = 3,14 * (0,04m)2 = 0,005024m S = 1m/1000m Q= 100 * (0 0,1256m)2 * 0,005024m * (1m/1000m)0,5 Q = 00,006295972m3/s Q = 0,006295972m3/s *1000l/m3 Q = 6,3l/s Pipe with 9 cm diameter, made of plastic and constructed with 0,1% slope: Flow rate(Q) = Material friction value(M) * lenght of the perimeter surface0,67 (R)* Cross sectional area(A) * Slope0,5(S) M = 100, R = π * d = 3,14 * 0,045m = 0,1413m A = π * r2 = 3,14 * (0,045m)2 = 0,0063585m S = 1m/1000m
Calculations done for the pipe connecting the western channel with wet basins shows that a pipe with a diameter of 17 centimers meets the demand for 44,8l/s Pipe connecting building A Flow rate(Q) = Rain intensity * Reduced area Ared = 947m2 Q = 190l/s/ha * 947m2 / 10000m2/ha =18l/s Sizing by trial-and-error approach: Pipe with 10 cm diameter, made of plastic and constructed with 0,1% slope: Flow rate(Q) = Material friction value(M) * lenght of the perimeter surface0,67 (R)* Cross sectional area(A) * Slope0,5(S) M = 100, R = π * d = 3,14 * 0,05m = 0,157m A = π * r2 = 3,14 * (0,05m)2 = 0,00785m S = 1m/1000m Q= 100 * (0,157m)2 * 0,00785m * (1m/1000m)0,5 Q = 0,011423851m3/s Q = 0,011423851m3/s *1000l/m3 Q =11,4l/s
Pipe with 12 cm diameter, made of plastic and constructed with 0,1% slope: Flow rate(Q) = Material friction value(M) * lenght of the perimeter surface0,67 (R)* Cross sectional area(A) * Slope0,5(S) M = 100, R = π * d = 3,14 * 0,06m = 0,1884m A = π * r2 = 3,14 * (0,06m)2 = 0,011304m S = 1m/1000m Q= 100 * (0,1884m)2 * 0,011304m * (1m/1000m)0,5 Q = 0,018587734m3/s Q = 0,018587734m3/s *1000l/m3 Q =18,6l/s Using a pipe with a diameter of 12 centimeter meets the demand of 18l/s. Overflow pipe for large wet basin Using 33l/s as rain intensity Roof area: 3304m2 Ared: 3304m2 * 1,0 = 3304m2 Flow rate(Q) = Rain intensity * Reduced area Q = 33l/s/ha * 3304m2 / 10000m2/ha = 10,9l/s Sizing by trial-and-error approach: Pipe with 8 cm diameter, made of plastic and constructed with 0,1% slope: Flow rate(Q) = Material friction value(M) * lenght of the perimeter surface0,67 (R)* Cross sectional area(A) * Slope0,5(S) M = 100, R = π * d = 3,14 * 0,04m = 0,1256m A = π * r2 = 3,14 * (0,04m)2 = 0,005024m S = 1m/1000m Q= 100 * (0 0,1256m)2 * 0,005024m * (1m/1000m)0,5 Q = 00,006295972m3/s
Q = 0,006295972m3/s *1000l/m3 Q = 6,3l/s Pipe with 10cm diameter, made of plastic and constructed with 0,1% slope: Flow rate(Q) = Material friction value(M) * lenght of the perimeter surface0,67 (R)* Cross sectional area(A) * Slope0,5(S) M = 100, R = π * d = 3,14 * 0,05m = 0,157m A = π * r2 = 3,14 * (0,05m)2 = 0,00785m S = 1m/1000m Q= 100 * (0,0,157m)2 * 0,00785m * (1m/1000m)0,5 Q = 0,011423851m3/s Q =0,011423851m3/s *1000l/m3 Q =11,4l/s It is recommanded to use a pipe with a diameter of 10 centimeter.
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44
Hemerocallis sp. var. Daylily var.
4.7 PLANT SELECTION The selection of plants for the site needs to be both tolerante to dry and wet conditions, since there can be periods of both drought when there is no rain and wet when the rain is quite heavy. Note that different plants will have different tolerance to these conditions, and not every plant is suitable for every condition. At the site of Ă…dalsvej different solutions are dealth with such as green roofs, swales, rain gardens and vegetated channels. The plants are listed according to these solutions .
Sedum album White stonecrop var.
Rain garden or other infiltration basins
Green roofs with a low depth of soil
Buxus microphylla var. Littleleaf boxwood
Delosperma var. Iceplant Cascade stonecrop
Hemerocallis sp. var. Daylily var.
Festuca glauca Blue fescue
Iris sibirica Siberian iris var.
Sedum acre Biting stonecrop
Mahonia aquifolium Tall Oregon grape
Sedum album White stonecrop
Spiraea douglasii or Hardhack Douglas spiraea
Sedum divergens
Viburnum davidii David viburnum
Spiraea douglasii Douglas spiraea
Sedum hispanicum var. Spanish stonecrop
Sedum telephium var. Autumn joy
Sedum reflexum Reflexed stonecrop
Vegetated channels
Sedum sexangular Tasteless stonecrop
Camassia leichtlinii Camas lily
Sedum telephium var. Autumn joy sedum
Sedum spurium var. Two-row stonecrop
Camassia quamash Common camas
Swales
Carex obnupta Slough sedge Cornus stolonifera Red twig dogwood Deschampsia caespitosa Tufted hairgrass
Acer Sacharrum Sugar Maple
Iris douglasiana Douglas iris
Acer Circinatum Vine Maple
Juncus balticus Baltic rush
Arctostaphylos uva-ursi Kinnikinnick
Juncus tenuis Slender rush Malus fusca Pacific crabapple
Camassia leichtlinii Camas lily
Carex densa Dense sedge
Lavandula stoechas var.
Carex obnupta Slough sedge
Spanish lavender
Mimulus guttatus Yellow monkey flower
Gaultheria shallon Salal
Physocarpus capitatus Pacific ninebark
Juncus patens Grooved rush
Rosa nutkana Nootka rose
Lavandula stoechas var. Spanish lavender
Sisyrinchium californicum Yellow-eyed grass
Mahonia repens Creeping Oregon grape
Spiraea douglasii or Hardhack Douglas spiraea
Salix purpurea nana Blue arctic willow
Viburnum edule Highbush cranberry
Native wetland grass mix
Deschampsia caespitosa Tufted hairgrass
Salix purpurea nana Blue arctic willow
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4.8 PLAN B SOLUTION 1 The stormwater management interventions for Ådalsvej are sized to accommodate 5 year rain events. But in the case of a 20 year rain event Ådalsvej requires a ‘Plan B’ system. In Plan B Solution 1 there is the possibility to infiltrate. It is suggested that Grøndals Parken, which is at the topographically lower end of Ådalsvej is to be used to accommodate the excess water. Grøndals Parken historically was a wetland and directing water could be argued suitable. Due to their lack of potential financial benefits, wetlands have historically been the victim of large-scale draining efforts for developments; this is likely what has happened in Grøndals Parken. However directing water here would be controversial from the municipality’s perspective as it will have effects on recreation and maintenance. Overall it has been concluded that urban areas around and including Ådalsvej are ‘maybe suitable’ for infiltration, meaning that infiltration is not recommended, however it is not prohibited.
Dry basin in dry weather
As this is a 20 year event system a solution needs to be suggested that is multifunctional. The majority of the time it is a space that can be used as parkland but in the event of a 20 year rain event functions as a stormwater management system. A dry basin seems the obvious choice. Dry basins are storage areas for stormwater runoff, which are empty of water during dry weather periods. They provide temporary storage and attenuation of the runoff. The basins inflow diameter is larger than its outflow diameter, this is so it can quickly receive stormwater, retain it and let the water drain away slowly. The water would drain away into the steam that flows through Grøndals Parken. By releasing the water slowly it reduces the erosion that is caused by larger and faster flowing water volumes. In Grøndals Parken the dry basin would be created without a membrane on the bottom to allow for infiltration. There would not have much time for infiltration as the infiltration area is usually small and the time the stormwater spends in the basin is usually short. 46
Dry basin after 20 year rain event
4.9 PLAN B SOLUTION 2 The non infiltration solution for Ådalsvej is sized to accommodate a 5 year rain event. In case of a much higher rain event the intervention cannot retain the amount of runoff. Therefore there has to be a Plan B. The Plan B is also used to accommodate the water that has to be transported from Ådalsvej as the non infiltration solutions has to rely on transport to drain the basins of water on a short time. As a Plan B the green area of Grondals Parken is used to store and accommodate the stormwater from a 20 year rain event. Grondals Parken is today mainly used as a recreational area which could be the argument used for the solution to create something for the public. To produce something for the public will have a number of benefits such as an increased use of the site, which can be related to increased safety, and also an activity for the public which most of the times are highly appreciated. As in solution 3 and 4 storage, evaporation and transport of water is prioritized and infiltration is not possible. Argued that the solution both should store water and be used by the public a skate park could be suitable. The depressions of the skate park could be used for temporary storage incase of a high rain event and be used by skaters when dried out. There should be one or several main depression to which the water directs. These are found in the lower parts so this is where the water will be directed to and of course they are also bigger in size. By using main depressions it will increase the chances for the other depressions to be used by
the public. In these main depressions water could be standing at all times and the water will be stored and delayed and has an outflow towards the stream that flows through Grondals Parken. This outflow to the stream has a much lower diameter than the inflow to the depressions. This will fill the stream up in a slow pace which prevents scenarios such as erosion. The quality of the runoff from Ådalsvej will improve further since the main depressions will have sedimentation and will have a function of a sedimentation pond. Also, if the runoff volume is bigger than what the main depressions are able to store, the smaller depressions, used by skaters, will be temporary be filled. The channels that transport the runoff at Ådalsvej towards the basins at the site only holds the amount of runoff for a 5 year rain event. This means that during a higher rain event there will be overflow on the transport system but the topography at the site will lead the water towards the green area.
Skate park in dry weather
Skate park after 20 year rain event 47
5
RE-IMAGINING COPENHAGEN STREETS
DISCUSSION
SECTION 5
DISCUSSION CONCLUSION
REPORT FOCUS
This aim of this report was to address stormwater management in the urban context and to offer sustainable and viable alternatives to combined sewer overflows. It focused on implementing ‘zero solutions’ that disconnected residential areas, such as Ådalsvej, from existing water systems and demonstrated how stormwater can be managed locally and enhance biodiversity and recreational values of the area.
This report could have had two possible directions. One direction could have been ‘product orientated’ where the report aims to produce one design solution for Ådalsvej.
This report was lead by a series of objectives that were constantly referred to throughout the design process. We are confident in saying that all the below objectives were met in the four suggested solutions for Ådalsvej. OBJECTIVES • To disconnect the chosen site from the existing combined sewer system.
The problem with this direction is that providing one solution would mean creating a specific scenario for the site. We would have to had decided if we could infiltrate or not and if we could use private space or not. This would be presuming too much about the site without further research. This would create an unrealistic situation and the proposed solution may not be a true reflection of the site’s situation and requirements. The report would be very site specific and inapplicable to other residential streets. On the contrary it would have allowed for a more detailed final product that could be implemented on Ådalsvej.
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To provide a ‘Zero Solution’ for managing storm water runoff locally.
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To offer an example of an effective ‘Zero Solution’ to storm water management in a typical residential scenario that will inform future sustainable development.
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To provide ‘Plan B’ solutions that respond to twenty year rain events.
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To enhance the recreational and aesthetical value of the area as well as improving biodiversity.
The direction taken was ‘research orientated’ where the report aimed to produce a range of design solutions for Ådalsvej. This involved exploring the range of scenarios the site presents and suggesting a comprehensive detailed solution for each. This direction created a variety of solutions for Ådalsvej and a framework of solutions that could be applied to other residential streets. These solutions could also be presented to the residents of Ådalsvej and the municipality for them to partake in the selection of the most appropriate solution. Providing four solutions allowed for a greater knowledge and exploration of a variety of stormwater management systems.
•
To treat and improve storm water runoff quality locally and by sustainable methods.
SOLUTION ANALYSIS
To improve ‘liveability’ of the road space and promote stakeholder ownership in the proposed systems.
SOLUTION 1: The use of public and private space with the possibility to infiltrate.
•
Advantages • Solution one utilises an uncomplicated suit of three implementation 50
systems; green roofs, rain gardens and vegetated infiltration trenches. This solution is a complete system where each implementation is fully supported for overflow by another implementation during five year rain events. In the case of an event higher than a 5 year event the system is fully supported by a Plan B. Therefore this is a Zero Solution. •
Solution one infiltration system requires the Plan B solution on a low number of occasions compared to the non-infiltration systems.
•
Solution one is an effective use of space both in public and private areas. The small dimensions of the vegetated infiltration trench along with the private solutions of rain gardens and green roofs have a low impact on the function of the streetscape.
•
The on street implementations greatly improve the streets aesthetics through greening of the road edges, creating a strong sustainable identity for Ådalsvej.
•
Visible on surface infiltration SUD systems can raise awareness of the water cycle, climatic changes and promote a more sensitive use of water resources. It exposes the environmental and aesthetical impacts that residential habits can have on the aquatic ecosystem and encourage people to reduce the use of polluting substances.
•
An infiltration solution resembles the natural water cycle. It helps sustain and stabilise the ground water balance and freshwater supply which supports local wetlands, local stream baseflow and the associated flora and fauna. It also prevents the damaging effects of land subsidence on infrastructure and buildings.
•
Biodiversity values and recreational values such as gardening and habitat creation are enhanced through greening of the streetscape, gardens and roofs. Infiltration systems support the urban ecosystems by improving ecological conditions. Water increases the attraction of the environment and can contribute to a greener and richer plant and animal life.
the cost of implementation is significantly lower. •
•
•
•
Infiltration SUD systems relieves stress on the existing sewer system and treatment plants by reducing the loading rate. It also reduces the chance of sewer overflow which can have negative environmental consequences such as the uncontrolled pollution of local water bodies. Open water bodies and extensive greening established by the use of SUDS can help reduce the urban heat island effect and provide a more comfortable local microclimate regarding humidity and temperature. Infiltration systems offer economical advantages. There is the potential for the municipality to provide an initiative that reimburses the connection fee to local residents who disconnect stormwater from the combined sewer system by using green roofs and rain gardens. It has been calculated by Copenhagen Energy (KE) that reimbursing residents who disconnect is the cheapest climate change adaptation and more cost effective than expanding the combined sewer system to accommodate future climate conditions.
•
•
•
•
•
Land and property value of the surrounding residential area may increase due to a more attractive and greener streetscape.
Disadvantages • This solution is infiltrating in an area that is deemed unsuitable, but not prohibited, by the municipality. •
•
On Ådalsvej the infiltrations systems can lead to the pollution of the ground water and surface soil as it is receiving runoff from roads and parking areas. However, the implementations include pollutant removing assets such as active soil layers and effective vegetation and the heavy metal and xenobiotics levels of Ådalsvej are considered low due to light vehicular activity. The cost of maintaining the efficiency of the infiltration systems compared to the existing combined sewer systems is higher due to removing sediments and the replacement soil and vegetation however,
•
The implementation of infiltration systems in an area of clay soil like Ådalsvej poses a risk of soaking the soil over extended periods of time, this can lead to muddy ground in gardens.
•
Further consideration towards the placement of rain gardens in proximity to buildings will be required as the creation of a secondary water table can damage to the foundations of buildings and basements. It would be difficult to retrofit all private residential properties along Ådalsvej with a rain garden and green roof. It also takes a great deal of private involvement and acceptance when implementing these systems on private ground. There are many practicalities to consider that are beyond the remit of this report but we can appreciate the extra thought involved. Rain gardens and green roofs located within a private property are subject to varying degrees of maintenance. It would also be a challenge for the local authority to overview possible mal-functioning systems which could affect the efficiency of the implementations.
•
The WADIs and vegetated infiltration trenches greatly improve the streets aesthetical diversity through greening of the public realm, creating a strong sustainable identity for Ådalsvej.
•
Visible on surface infiltration SUD systems can raise awareness of the water cycle, climatic changes and promote a more sensitive use of water resources. It exposes the environmental and aesthetical impacts that residential habits can have on the aquatic ecosystem and encourage people to reduce the use of polluting substances.
•
An infiltration solution resembles the natural water cycle. It helps sustain and stabilise the ground water balance and freshwater supply which supports local wetlands, local stream baseflow and the associated flora and fauna. It also prevents the damaging effects of land subsidence on infrastructure and buildings.
•
Compared to solution one, on street biodiversity and recreational values are significantly higher and enhanced through greening of the streetscape. This additional green space acts as an extension of the private gardens encouraging local ownership and outdoor activities.
•
Infiltration systems support the urban ecosystems by improving ecological conditions. Water increases the attraction of the environment and can contribute to a greener and richer plant and animal life.
•
Infiltration SUD systems relieves stress on the existing sewer system and treatment plants by reducing the loading rate. It also reduces the
There is an associated safety risk with open bodies of water however, solution one presents a reduced risk as they are filled temporarily due to infiltration.
SOLUTION 2: The use of public space with the possibility to infiltrate. Advantages • Solution two utilises an uncomplicated suit of three implementation systems; rain gardens, vegetated infiltration trenches and WADIs. This solution is a complete system where each implementation is fully supported for overflow by another implementation during five year rain events. In the case of an event higher than a 5 year event the system is fully supported by a Plan B. Therefore this is a Zero Solution.
Solution two infiltration systems requires the Plan B solution on a low number of occasions compared to the non-infiltration systems. Solution two is an effective use of space and has been designed to maintain the function and a continuous traffic flow of Ådalsvej as much as possible. Although the WADI has a high impact on the streetscape and takes up large areas of public space this solution implements positive traffic calming measures.
51
chance of sewer overflow which can have negative environmental consequences such as the uncontrolled pollution of local water bodies. •
•
•
Open water bodies and extensive greening established by the use of SUDS can help reduce the urban heat island effect and provide a more comfortable local microclimate regarding humidity and temperature. nfiltration systems offer economical advantages. It has been calculated by Copenhagen Energy (KE) that disconnecting is the cheapest climate change adaptation and more cost effective than expanding the combined sewer system to accommodate future climate conditions.
•
The implementation of infiltration systems in an area of clay soil like Ådalsvej poses a risk of soaking the soil over extended periods of time, this can lead to muddy ground in gardens.
Disadvantages • Water volumes must be dealt with on the surface which is a limiting design criterion.
•
Further consideration towards the placement of rain gardens in proximity to buildings will be required as the creation of a secondary water table can damage to the foundations of buildings and basements.
•
Non-infiltration systems require the Plan B solution on a greater number of occasions compared to the infiltration systems.
•
Non-infiltration can get very complicated as the stormwater management is a system of components that include delay, detain, transport, evaporation and evapotranspiration elements in connection.
•
It would be difficult to retrofit all private residential properties along Ådalsvej with a green roof. There are many practicalities to consider that are beyond the remit of this report but we can appreciate the extra thought involved.
•
There is an associated safety risk with open bodies of water however, solution one presents a reduced risk as they are filled temporarily due to infiltration.
As all implementations in solution two are located within the public realm the centralised systems are planned and managed by a signal organisation unit of the local authority this allows greater overview and maintenance of possible mal-functioning systems.
SOLUTION 3: The use of public and private space with no infiltration possibilities. •
Land and property value of the surrounding residential area may increase due to a more attractive and greener streetscape.
Advantages • This solution is a complete system where each implementation is fully supported for overflow by another implementation in the case of an extreme rain event.
It takes a great deal of private involvement and acceptance when implementing green roofs on private ground. Again, there are many practicalities to consider that are beyond the remit of this report but we can appreciate the extra thought involved.
Disadvantages • This solution is infiltrating in an area that is deemed unsuitable, but not prohibited, by the municipality.
•
Stormwater runoff and management systems are visible which encourages environmental and climatic awareness.
•
Green roofs located within a private property are subject to varying degrees of maintenance which can affect the efficiency of the implementations.
•
On Ådalsvej the infiltrations systems can lead to the pollution of the ground water and surface soil as it is receiving runoff from roads and parking areas. However, the implementations include pollutant removing assets such as active soil layers and effective vegetation and the heavy metal and xenobiotics levels of Ådalsvej are considered low due to light vehicular activity.
•
This solution is not infiltrating in an area that is deemed unsuitable, but not prohibited, by the municipality.
•
The small scale of a vegetated water basin along with the private solutions of green roofs has a low impact on the function of the streetscape.
Evaporation and evapotranspiration is so low that the non infiltration solution has to rely on transport of the runoff to the Plan B just to empty the basins in a short period of time.
•
Due to sedimentation in the basins there is an increased maintenance from the municipality
The cost of maintaining the efficiency of the infiltration systems compared to the existing combined sewer systems is higher due to removing sediments and the replacement soil and vegetation however, the cost of implementation is significantly lower.
•
The on street implementations greatly improve the streets aesthetics and alignment.
•
The economical aspect. Due to maintenance and remaking of the street the solution is quite expensive if you only look at the money aspect. (Although there is also a lot of benefits that cant be valued in money)
•
•
52
•
•
Biodiversity values and recreational values such as gardening are enhanced through greening of the streetscape.
SOLUTION 4: The use of public space with no infiltration possibilities.
•
Advantages • This solution is a complete system where each implementation is fully supported for overflow by another implementation in the case of an extreme rain event.
During 20 years rain events we will have to rely on the street as one main channel leading water to the plan B storage facility or using a pumping system leading water to the sewer system. The evaporation in itself is too small to get water basins empty.
PLAN B ANALYSIS •
•
•
This solution is not infiltrating in an area that is deemed unsuitable, but not prohibited, by the municipality. Stormwater runoff and management systems are visible which encourages environmental and climatic awareness. The on street implementations greatly improve the streets aesthetics and alignment. This solution greatly enhances traffic calming measures.
Advantages • In the occurrence of a rain event that is greater than a 5 year event Grøndals Parken will provide a Plan B solution further reinforcing that solutions one and two are Zero Solutions.
Biodiversity values and recreational values such as gardening are enhanced through greening of the streetscape.
Disadvantages • The large scale of the wet basins and transport elements have a high impact on the streetscape and take up large areas of public space but have been designed to maintain function and a continuous traffic flow as much as possible. •
•
This solution is multifunctional, it requires the space in Grøndals Parken for a relatively short period of time; therefore the impact on the park will only be temporary and will allow its permanent function to return.
•
Re-introduction of the historical wetlands will greatly improve the biodiversity of Grøndals Parken. Biodiversity values are enhanced through increased infiltration which supports and improves ecological conditions. Water increases the attraction of the environment and can contribute to a greener and richer plant and animal life.
Non-infiltration can get very complicated as the stormwater management is a system of components that include delay, detain, transport, evaporation and evapotranspiration elements in connection. Water volumes must be dealt with on the surface which is a limiting design criterion. Non-infiltration systems require the Plan B solution on a greater number of occasions compared to the infiltration systems. In our case this implies in situations with several rain events with short intervals.
Open water bodies and extensive greening established by the use of SUDS can help reduce the urban heat island effect and provide a more comfortable local microclimate regarding humidity and temperature.
•
Visible on surface infiltration SUD systems can raise awareness of the water cycle, climatic changes and promote a more sensitive use of water resources. It exposes the environmental and aesthetical impacts that residential habits can have on the aquatic ecosystem and encourage people to reduce the use of polluting substances.
•
Infiltration SUD systems relieves stress on the existing sewer system and treatment plants by reducing the loading rate. It also reduces the chance of sewer overflow which can have negative environmental consequences such as the uncontrolled pollution of local water bodies.
•
Solutions one and two will ensure that all water entering Grøndals Parken will have been thoroughly treated of pollutants through removal assets such as active soil layers and effective vegetation. This is further ensured by the fact that the heavy metal and xenobiotics levels of Ådalsvej are considered low due to light vehicular activity.
This is a realistic solution that can be easily implemented and would not have a great impact on the parks existing recreational values.
•
• •
•
SOLUTION 1: The use of Grøndals Parken with infiltration possibilities.
• •
and fauna.
•
Flooding this area provides a sensitive stormwater management system compared to the overflow of a combined sewer system. Infiltration systems on Ådalsvej will require the Plan B solution on a low number of occasions compared to the non-infiltration systems. An infiltration solution resembles the natural water cycle. It helps sustain and stabilise the ground water balance and freshwater supply which supports local wetlands, local stream baseflow and the associated flora
Disadvantages • The municipality may oppose this suggestion as there is infiltration in an area that is deemed unsuitable, but not prohibited and there is greater maintenance required. •
It will prove to be a challenge to transport water from Ådalsvej across Grøndals Parkvej and into Grøndals Parken.
•
There is an associated safety risk with open bodies of water however, this solution presents a reduced risk as the dry basin is only filled temporarily due to infiltration.
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•
The implementation of infiltration systems in an area of clay soil like Grøndals Parken poses a risk of soaking the soil over extended periods of time, this can lead to muddy ground in areas of recreational value.
•
•
The cost of maintaining the efficiency of the infiltration systems compared to the existing combined sewer systems is higher due to removing sediments and the replacement soil and vegetation however, the cost of implementation is significantly lower.
NEXT STAGES
SOLUTION 2: The use of Grøndals Parken with no infiltration possibilities. Advantages • This is a realistic solution that can be easily implemented and will highlight the importance of stormwater management and climatic change. •
A skate park has a strong social aspect and would improve the parks existing recreational values.
•
A sunken skate park can function as a detention basin and hold a large volume of water.
Disadvantages • The municipality may oppose this suggestion as there is greater maintenance required and there are considerations for health and safety. •
A question of quality of the water. Is the sedimentation and retention at the basins of Ådalsvej and in the main depressions enough to send the water to the stream in Grondals Parken without causing the pollution of the stream?
•
An overflow/outflow system to Grøndalsåen will be necessary in order to avoid the skate park to be flooded for longer periods, due to the slow evaporation . In this respect water quality has to be high to avoid polluting Grøndals åen.
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Some sort of sedimentation facility is needed in addition to the skate park.
This report severed as a research orientated study that proceeded stakeholder and municipality involvement. It has generated four solutions that address the two constraints; the possibilities to infiltrate and the possibilities of using private space. The next stages would be to present this report to the stakeholders and the municipality in a series of consultation events that would establish the parameters of the constraints and address stakeholder concerns. In response there would be further development of a solution that accommodated the identified parameters for Ådalsvej. This response would include a site specific refined designed solution and comprehensive technical specification that could be implemented on site. This report produced four solutions that can also serve as a framework or a foundation for other similar residential sites that are wishing to disconnect. This report can be used by many stakeholders and adapted to suit each sites individual scenarios and constraints.
SECTION 6
REFERENCES •
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Design Principals, San Manteo County Sustainable Green Streets and Parking Lots design Guidebook, first edition, January 2009.
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Solutions literature, Lecture presentation by Antje Backhaus -SUDS Function and Design
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Solutions photography, Copyright of Kevin Robert Perry. Taken from the page: http://www.portlandonline.com/bes/index.cfm?c=34598
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Solutions photography, various Flickr pages with the creative commons license.
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Solutions photography, “Large Wet Basin” and ”Channel and Vegetated Wet Basin” from Augustenborg taken by Author
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Solutions photography, “Wet Basin Along Street” from “Green Streets tour map” http://www.portlandonline.com/BES/index.cfm?c=44407&
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Solutions photography, “Open Channel” from www.galenfrysinger.com/ germany_freiburg.htm
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Solutions photography, “Access Across Channel” from Internet (we can not find the reference)
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Plant List, http://www.portlandonline.com/bes/index. cfm?c=43110&a=129060
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Plant List, Planlaegningsguide Ekstensive tagbeplantning med system ZinCo
Malmo Western Harbor, http://www.malmo.se/download/18.293ce0691 104a399cfe800064/fb_total_webb_final_070122.pdf Malmo Western Harbor photography Mark and Beckys own.
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Augustenborg, ”Inner city stormwater control using a combination of best management practices” , Edgar L. Villarreal, Annette SemadeniDavies, Lars Bengtsson, Ecological Engineering 22 (2004) p 279-298, www.sciencedirect.com
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Solutions literature, Stormwater Compendium by Marina Bergen Jensen
Design Principals, Lecture presentation by Marina Bergen Jensen and Ole Fryd - Urban Hydrology and Stormwater Management
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Augustenborg photography, All 3 photos by author. Diagram from: ”Inner city stormwater control using a combination of best management practices” , Edgar L. Villarreal, Annette Semadeni-Davies, Lars Bengtsson, Ecological Engineering 22 (2004) p 279-298, www.sciencedirect.com Augustenborg, Guided tour by employee from Scandinavian Green Roof Institute
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Monnikenhuizen, Article Luebbers
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Monnikenhuizen, Article Yearbook
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Portland streets, http://www.portlandonline.com/BES/index. cfm?c=44407
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Portland streets, http://www.portlandonline.com/BES/index. cfm?c=34602
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Site Survey, Lecture presentation by Ole Fryd - Harrestrup Maps Presentation
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