The role of Green Structures in Development of the Sustainable City

TRITA-INFRA EX 04-084 

ISSN 1651-0194 

ISRN KTH/INFRA/EX-04-084-SE 

KTH Infrastructure 

THE ROLE OF GREEN STRUCTURES IN 

DEVELOPMENT OF THE SUSTAINABLE CITY 

Supervisor: Dr. Dorota Wlodarczyk 

Examiner: Prof. Dick Urban Vestbro 

Jie Chen 

Stockholm 2004 

Master Thesis in the Subject of 

Built Environment Analysis, Division of Urban Studies, Department of Infrastructure 

Within the Master Programme Environmental Engineering and Sustainable Infrastructure 

Royal Institute of Technology 

1

THE ROLE OF GREEN STRUCTURES IN 

DEVELOPMENT OF THE SUSTAINABLE CITY 

Jie Chen 

Supervisor: Dr. Dorota Wlodarczyk 

Examiner: Prof. Dick Urban Vestbro 

Master Thesis in the Subject of Built Environment Analysis within the Master Programme 

Environmental Engineering and Sustainable Infrastructure, Division of Urban Studies, 

Department of Infrastructure, The Royal Institute of Technology 

2

Master Thesis 2004 

Department of Infrastructure 

Division of Urban Studies 

The Role of Green Structures in Development of the Sustainable City 

© Jie Chen 

TRITA-INFRA EX 04-084 

ISSN 1651-0194 

ISRN KTH/INFRA/EX-04-084-SE 

Cover Photograph: View of Gustaf Adolf's Place, Enköping. (Courtesy of Enköping 

municipality) 

Print: Universitetsservice US AB, Stockholm 2004 

Distribution: KTH/Department of Infrastructure/Division of Urban Studies/Built Environment 

Analysis, 100 44 Stockholm 

3

Acknowledgements 

With a deep sense of gratitude, I wish to express my sincere thanks to my supervisor Dr. Dorota 

Wlodarczyk who kept an eye on the progress of my work and always was available when I needed her 

advices, with her immense help in planning, especially with data collections and field studies in 

Enköping. I specially thank the EESI programme coordinator Jan-Erik Gustafsson for the financial 

support in conducting this thesis. I also would like to thank Professor Dick Urban Vestbro for his 

suggestions and concerns with my work. 

My sincere thanks are due to Wendelin Müller-Wille, Chairman of the education committee in 

Enköping Municipality, for his great help with information collections, local interviews and 

encouragements. I wish I would never forget the help of Enköping Municipality staff. In particular, I 

am thankful to Danielle Littlewood, Stefan Mattson, Mats Jonsson, Marie Lewen-Carlsson. 

I also would like to thank Docent Per. Berg from the Department of Landscape Planning, Swedish 

Agriculture University. His valuable suggestions in landscape analysis investigation are greatly 

acknowledged. Many thanks to Landscape architect Alexander Ståhle with his valuable information. 

The acknowledgement would not be complete without the mention of my colleague Chung-Wenyuan 

for his timely help to my thesis park analysis auto drawing. 

I also want to thank my parents, who taught me the value of hard work by their own example. I would 

like to share this moment of happiness with my mother, grandmothers and uncles. They rendered me 

enormous support during the whole tenure of my research. The encouragement and motivation that was 

given to me to carry out my research work by my father Chen-Jianzhong is also remembered. 

Finally, I would like to thank all whose direct and indirect support helped me completing my thesis in 

time. 

Jie Chen 

Stockholm, December 2004 

4

Abstract 

Urban growth causes various environmental problems. In order to ameliorate this problem, the idea of 

the compact city has been introduced nowadays. However, densification can imply a loss of other 

important urban quality factors, such as green spaces. A reduction of urban green structure due to urban 

growth can lead to degradation of ecosystem services, air quality, recreation and aesthetic. However the 

decision makers and urban planner seldom recognize the roles of green structures play in many cities all 

over the world. Too often green areas are treated as leftover space, sometimes as reserve for potential 

future profitable functions. 

In this master thesis, main focus is on the roles of green structure in the urban environment. A 

theoretical study is carried to review the functions of the green areas within cities. Enköping 

muncipality was selected a case and studied. The case contributes with analysis of the public life in 

urban green areas, functioning of storm water treatment park. Accessibility of green areas in Enköping 

was evaluated. 

The analysis shows that city landscape may affect the health of town-dweller. Statistically significant 

relationships can be found between the use of urban open spaces and self-reported experiences of stress. 

Meanwhile, the findings show the importance of green areas for urban biodiversity development, 

removal of nitrogen, phosphorous and heavy metals, as well for city climatic conditions improvement. 

Key Words: green structure, wetland, public life, human health, energy conservation, biodiversity, 

Enköping 

5

Table of Contents 

Acknowledgements ............................................................................................................................. 4 

Abstract ..................................................................................................................................................... 5 

Table of Contents........................................................................................................................................ 6 

1. Introduction ...................................................................................................................................... 7 

1.1 Sustainable Development...................................................................................................................7 

1.2 Statement of the Problems and Study Objectives .............................................................7 

1.3 Research Methodology ........................................................................................................................8 

2. Urban Green Structure.............................................................................................................. 9 

2.1 Urban Green Structure Historical Development in Sweden......................................9 

2.2 Definition of Urban Green Structure ........................................................................................9 

2.3 Classification of Green Structure...............................................................................................10 

2.4 Functions of Green Structure .......................................................................................................10 

Key Concepts: .................................................................................................................................................11 

3. Analysis of Functions of Urban Green Areas............................................................ 12 

3.1 Green Structure and Urban Climate.......................................................................................12 

3.11 Green Structure and Air Quality.........................................................................................................13 

3.12 Green Structure and Energy Conservation ..............................................................................................13 

3.13 Green Structure and Wind Control ....................................................................................................15 

3.2 N, P and Heavy Metals Removal by Green Area.............................................................16 

3.3 Green Structure and Biodiversity..............................................................................................21 

3.4 Green Structure and Health ..........................................................................................................22 

3.5 Green Structure and Noise Reduction....................................................................................23 

3.6 Green Area and Surface Erosion Control ............................................................................23 

4. Case Study - Enköping ............................................................................................................. 25 

4.1 Introduction..............................................................................................................................................25 

4.2 Selected Components of Green Structure: Public Parks, Pocket Parks and 

Gardens ...............................................................................................................................................................26 

4.21 Accessibility ..............................................................................................................................................27 

4.22 Public Life.................................................................................................................................................28 

4.23 Human Health.........................................................................................................................................28 

4.3 Storm Water Treated by Water Park .....................................................................................33 

4.4 Energy Supply by Energy Forest ...............................................................................................36 

5. Conclusions..................................................................................................................................... 39 

6. References........................................................................................................................................ 41 

APPENDIX................................................................................................................................................... 43 

GLOSSARY................................................................................................................................................... 44 

6


1. Introduction 

1.1 Sustainable Development 

Particularly in the last decade, there have been a number of attempts to define sustainable development 

formally. Probably the most frequently cited definition is that put forth by the World Commission on 

Environment and Development (WCED), also commonly known as the Brundtland Commision, which 

defined sustainable development as that which “meets the needs of the present without compromising 

the ability of future generations to meet their own needs” (WCED, 1987). It means sustainable 

development is thus a much broader concept than environmental protection. It implies a concern for 

future generations and for the long-term health and integrity of the environment. It embraces concerns 

for the quality of life (not just income growth), for equity between people in the present (including the 

prevention of poverty), for inter-generational equity (people in the future deserve an environment which 

is at least as good as the one we currently enjoy, if not better), and for the social and ethical dimensions 

of human welfare. It also implies that the further development should only take place as long as it is 

within the carrying capacity of natural systems. Clearly, addressing the sustainable agenda provides 

new challenges for urban policy integration within holistic frameworks. (European Commission, 1996). 

More recently, the National Commission on the Environment has defined sustainable development as a 

strategy for improving the quality of life while preserving the environmental potential for the future, of 

living off interest rather than consuming natural capital. Sustainable development mandates that the 

present generation must not narrow the choices of future generations but must strive to expand them by 

passing on an environment and an accumulation of resources that will allow its children to live at least 

as well as, and preferably better than, people today. Sustainable development is premised on living 

within the Earth’s means (National Commission on the Environment 1993). 

In 1998, European Commission stated in the report “Toward Urban Agenda in European Union”: “the 

green city model is an alternative model for the sustainable city, based on ecological design and the 

development of more or less sufficient communities. In comparison with the compact city, urban and 

rural areas are more integrated, and greater urban self-sufficiency promotes reduced car use. 

However, implementation of the green city model is based on the availability of land, which may pose a 

problem in densely populated countries”. 

1.2 Statement of the Problems and Study Objectives 

A large proportion of the urban growth occurs at the urban fringe and urban hinterland. It leads to a 

separation between workplace and housing thereby increasing the needs of cars or another transports to 

commute. That in turn causes various environmental problems. In order to ameliorate this problem, the 

idea of the compact city has been developed. However, densification can imply a loss of other 

important urban quality factors, such as green spaces. A reduction of urban green structure due to urban 

growth can lead to degradation of ecosystem services, air quality, recreation and aesthetic quality. 

Main question within this theme concerns urban growth and densification and multifunctional urban 

green structures. This question relates to the spatial dimension of the environmental, social and 

economic of sustainable development and requires integrated planning approaches across sectors and 

disciplines in order to be properly managed. The urban green space is important to the quality of urban 

everyday life of the citizens as well as in ecological processes. The current problem is that in many 

cities all over the world, the decision makers and urban planners take less consideration about this role 

due to insufficient fund on it. Too often green areas are treated as leftover space, sometimes as reserve 

for potential future profitable functions. In this thesis paper, the comprehensive green structure concept, 

which is concerned with sustainable city development, will be presented. Enköping town with 38 000 

inhabitants, which has received the Golden Award in the international competition "Nations in Bloom" 

in 2003, will be the case studied in this thesis. 

7

1. Introduction 

1.3 Research Methodology 

In this thesis paper, different research methods have been used. Chapter 2 (Urban Green Structure) and 

3 (Analysis of functions of urban green areas) are mainly based on literature review and information 

obtained from internet. 

The Chapter 4 is complemented by information from the interviews and observations made during the 

case study period. Interviews with the Enköpings Kommun leaders, who are from Consultant 

Department, Water & Street Cleaning Department, Parks Department, City Council, Education 

Committee and Street Department are important. They present views and knowledge and are of great 

assistance in language understanding. Direct-observations were carried out on Wednesday, Oct. 6 th . 

2004 in Kaplanen Park, Kloster Park and Water Park, while interviews with inhabitants in Kloster Park 

carried out. Detailed information attached in Appendix. 

Dr. Student Ulrika A. Stigsdotter research results concerning “level of stress of employees at 

workplace” is quoted to analyse public park and human health in the Chapter 4. Her method was using 

questionnaires sent by post to 2,200 individuals of all ages, who were selected at random and lived in 

nine Swedish cities: Enköping, Halmstad, Kristianstad, Lund, Trelleborg, Trollhättan, Uppsala, Varberg 

and Västerås. The response rate was 47%, answered by working people, the rest being children, 

pensioners and unemployed. The questionnaire contained three different parts. The first part focused on 

the respondents’ personal data, such as age, sex, profession, home environment and access to garden at 

home and at work. Part two dealt with how often and how long people visited the open spaces of the 

town, while the third part asked the respondents to self-estimate their health status. All questions were 

pre-coded, often with multiple-choice options, however with an opportunity to make their own remarks. 

Why use a case and choose Enköping as the case study area? 

A case study area is one, which is investigated to answer specific research questions and provide a 

range of different kinds of evidence. Before selecting Enköping as a case study area, other towns were 

considered. The choice of Enköping was motivated by the fact that the city in 2003 received the Golden 

Award in the international competition "Nations in Bloom", and was announced as the most livable 

community by the United Nations Environment Programme. The city, therefore, represents an 

interesting and much cases with challenging exposition of the study phenomena. Well-planned public 

parks and green area make Enköping information rich in terms of basic data sources when compared to 

other cities within the country. “The meticulous description of a case can have an impact greater than 

almost any other form of research report.” (Gillham, 2000). Enköping’s green structure was analysed 

and described in Chapter 4. 

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2. Urban Green Structure 

2.1 Urban Green Structure Historical Development in Sweden 

The green structure in Swedish towns today have developed during the last 200 years and have their 

origin in the development of the modern town in the 19 th century (Bucht and Persson, 1994). It was 

mainly for aesthetic, social and hygienic purposes that green structure like parks and strolling areas 

were laid out or restored. 

In the second half of 19 th century, parks such as city parks and parks close to railway stations were 

designed with ideas from England forming what is called the English Park (Bucht, 1993; Bucht and 

Persson, 1994), and from Germany (Bucht, 1997). In 1926, Rutger Sernander who is one of the 

Swedish professor in plant geography, he was one of the first in Sweden to suggest preservation of 

green habitat corridors from the city centre to nearby green recreation areas and nature reserves 

(Sernander, 1926). In the 1960s and 70s a major feature of urban green space planning in Sweden were 

the green spaces with accompanied the ‘million-homes programme’ developments, a national 

programme which aimed to build a million new homes for the Swedish population within ten years, 

between 1965 and 1975. The concept of the ‘city park’ became an archaic notion in Swedish urban 

design circles, replaced by large reserved areas for outdoor recreation. Nature was considered more 

important than it had been, and many green spaces were left in their natural state. These concepts laid 

more importance on activities than social interaction. In the 1970s a renewed interest in city parks could 

be seen, possible as a result of town planning ideas from Demark, where the concept of ‘dense and low’ 

development had emerged. This concept was a part of some million-programme developments, but did 

not infiltrate Swedish planning to the same extent as in Demark. (Geraint, 1998). In 1992 the United 

Nations Environmental Conference in Rio focused its attention and globally sustainable development, 

and quoted physical planning as being a possible means of maintaining the biodiversity. On a national 

level, the importance of the “green aspects” in the planning context has been attracting growing 

attention. The Swedish Planning and Building Act were revised in 1996 to incorporate the concept of 

“an appropriate structure of green areas”. The green structure is equated with buildings and 

infrastructure, and other facilities (Regionplane och Trafikkontoret, 1998). 

2.2 Definition of Urban Green Structure 

Urban green structure is a concept used in most Nordic countries, however with varying 

interpretations and legal status. Urban green structure contains all land of the urban landscape that is 

neither covered nor sealed, including parks, playgrounds, sport fields, allotments, private gardens, 

green space of housing districts, industrial properties as well as along streets and rail roads etc. In 

Sweden, green structure as a hidden resource, is often used in discussions related to urban 

development. The concept was introduced in the Swedish planning discussion in the beginning of the 

1990s. Ulf G.Sandström defined the green structure in an urban environment refers to all non-hard and 

non-built areas, including surface water areas as well as a zone of 1-2 km between town and 

countryside, that are more or less connected to each other. The structure should be organised with an 

overruling strategy, i.e. it must be possible to recognise a system in the structure. Accordingly a green 

infrastructure is a network of patches of natural character including surface water and greenways, 

penetrating an urban built-up area. The concept should not be limited by administrative considerations; 

i.e. both public and private lands are including in a green infrastructure (Sandström, 2002). The City 

Architect Office in Lund, Sweden supports the approach stating that: “ green structure include both the 

landscape and its nature in the city neighbourhood as well as all non-hard ground in the city. This 

means that the green structure in a local government plan includes not only determined green areas but 

also non-hard areas in housing areas, day nursery gardens, school yards, institutions and sports 

grounds, cemeteries, verges, green squares, allotments and adjacent sectors of the landscape. Also 

non-hard ground without any value for recreation, e.g. safety zones for traffic or industrial 

establishments, belongs to this category.” (Stadsarkitektkontoret in Lund, 1996:5) 

9

2. Urban Green Structure 

2.3 Classification of Green Structure 

The green structure can be classified as following (Beer, 2000): 

Paved city spaces with plants: courtyards & patios, roof gardens & balconies, tree-lined allees, 

promenades, city squares and schoolyards 

Parks, gardens and sports grounds: public parks, pocket parks, gardens, public sports grounds, 

public recreation areas and public playgrounds 

Burial places: crematorium, burial ground and churchyard 

Private open spaces: institution grounds, residential home grounds, health services grounds, private 

sports grounds, private estate grounds, local authority services grounds and commerce grounds 

Domestic gardens: house gardens, allotments, communal semi-public gardens and communal 

private garden 

Farmland and horticulture: arable, pasture and orchard 

Transport corridor verges: canal sides, rail sides and roadsides 

Water margins: wetland, riversides and lakesides 

Water: still water, running water 

Woods: woodland, timber/bio-fuel woodland, wild wood and semi-natural woodland 

Normally, green areas occupy a big part of the city area. However, formal green structure represents 

merely the green areas that are maintained by the local authorities, while the actual green structure 

represents all areas that fit the general definition of green structure. The maps below show substantial 

quantitative differences between the formal green structure (left map) and the actual green structure 

(right map) in a part of Göteborg the second largest city in Sweden. 

Figure 1: Substantial quantitative differences 

between the formal green structure (left map) 

and the actual green structure (right map) in 

a part of Göteborg 

Source: Alm, 2004 

2.4 Functions of Green Structure 

In relation to a sustainable urban development, green structure is important as functions and meanings 

for (Alm, 2004): 

Urban climate, noise moderation, air cleaning and handling surface water 

As an indicator of environmental changes 

Cultivation of energy plants 

Biodiversity: to save valuable urban species, as refuges for species from rural biotopes and as 

spreading corridors 

Social and cultural values: for health, recovering and rehabilitation, to give beauty and comfort, to 

give room for passivity and activity, as a cultural heritage, as an arena for citizenship, for education 

Urban design: to give a city understands able structure to connect different scales and parts of the 

urban landscape. 

10


Urban green structure is especially important for children and elderly people, as these groups often are 

limited to stay in the city while other groups easier can go to bigger nature areas outside of cities. Urban 

green structure is a vitally important link between nature and human. 

Key Concepts: 

Bio-energy 

Bio-energy source such as energy crops and forest wood fuel are carbon neutral over their life cycle and 

have potential to make a significant contribution to renewable energy and climate change. 

Biological diversity 

Heywood and Baste (1995) define biological diversity as the total diversity and variability of living 

things and of the systems of which they are a part. This covers the total range of variation in and 

variability among systems and organisms, at the bio-regional, landscape, ecosystem and habitat levels, 

at the various organism levels down to species, populations and individuals, and at the level of the 

population and genes. 

Blue structure 

In Scandinavia blue structure is more embedded and hidden in the natural landscape. Smaller water 

streams are often piped and covered in the cities and thus not always visible in everyday lives of the 

citizens. In physical planning water flows and wetlands are often seen as integrated, although very 

essential, elements of the green structure. 

Greenery 

Greenery understood both as single green elements such as trees; bushes etc and green environments 

(larger green area such as woods, sport fields and shrubberies) constitute a large amount of the urban 

landscape. 

Green corridor 

Green corridor is a system of balanced natural urban areas linked to the suburban green areas by linear 

street greenery and elongated green areas, often of great recreational and/or ecological value. The 

nature that exists in the landscape is the source use for disseminating wild plants and animals into urban 

areas. That is why green corridors out in the countryside and leading into urban areas are vital, as is the 

transitional zone between urban and rural. 

Green wedge 

The most important function of the green wedges is to form continuous green corridors containing both 

cultural and scientific values as well as attractive countryside for the enjoyment of human beings. 

Pocket park 

Pocket park is a small green space that can be found in an unexpected place. Its properties can be 

defined as (Brent Council, 2004) 

A small site often secreted between houses or buildings 

Will generally contain formal bedding 

High level of horticultural maintenance regardless of the type of planting 

Often has limited access due to its location 

Will often have a fairly high level of facilities considering its size 

Normally would be heavily used, especially by local people 

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3. Analysis of Functions of Urban Green Areas 


Green area development is to improve conditions of living, work and recreation for inhabitants, taking 

into account optimal bio-climatic, hygienic and aesthetic factors; to increase ecological sustainability, 

stability and biodiversity of city environment; to increase attractiveness of the city environment; to 

develop relevant green network, suitable for economic and social activities, what would stimulate the 

expansion of business, trade, tourism, increase investment flow. 

As urban authorities seek to maintain quality of life in the towns and cities, they have become 

increasingly aware of the value of green spaces within urban areas. Preservation of open spaces, 

protection of plant life, biodiversity and regeneration of riverbanks all involve social and cultural issues. 

Correct environmental planning management of urban green spaces requires close, creative cooperation 

between urban planners, architects, landscape architects and engineers. 

The features of well-functioning open space are to be based on several principles: no visual stress 

production, legibility, coherence, complexity, distance and size (Beer, 2000): 

 

 

 

 

 

 

No visual stress production: a spatial environment means that visually perceived space “is not either 

too diverse or too monotonous”. The criteria for such an ideal space depend on the 

neuropsychological characteristics of the human nervous system 

Legibility: it is “the inference that one can explore an environment without becoming lost”. From 

the point of the city image it is the possibility to find, notice, perceive, distinguish from the context 

the potential elements of city image 

Coherence: “ it is the sense that all parts of conceptually perceived environment make a one unit”. 

From the point of the city image coherence should depend on the three characteristics of the image: 

continuousness of the image, people see and remember the most distinguished elements of an 

environment while they move through a city. These memories are used for “creation” of the mental 

city image later, greenbelts can play an important role in creation of the more preferred 

environment; clear separation of parts of the image, the green slops of the rivers are very important 

for separation of the similar area; hierarchy, role of the green structure is not very big, but the green 

slopes make a great visual background for some very important landmarks in the image of city 

Complexity: “ environment is complex if it contains enough variety to make it worth to learn 

about”. The properties of human perception should be taken into consideration when the complexity 

is researched. We construct the mental image of environment from the pairs of oppositions. It is the 

fundamental feature of perception. Culture can determine the kind, number and spatial relations 

between the oppositions, the role of the green structure could be very important here; nature is 

understood as a natural opposition for urban environment in the EU culture. There the green 

structure makes the image more complex by forming a few, quiet important green districts in the 

image of the city 

Distance: as regard large areas for country walks situated near built-up area, which are of interest 

on a region scale. The most common view seems to be that the maximum distance should not be 

more than 2-3 km. In the case of a greater distance, there is a drastic decrease in the frequency of 

visits made to the area. Consequently it should not take longer than half an hour to reach one of the 

large green areas. Otherwise the travel time becomes unreasonably long in relation to how much 

time can be spent in the green area 

Size: the size of the green area is also important for the experience of seclusion and freedom from 

disturbance. If too many people use the same recreational area, it can loose its character and 

become “worn down”. The size of the recreational area must therefore be adapted to the number of 

people visiting the area in order for it to retain its qualities in the long term. 

3.1 Green Structure and Urban Climate 

The phenomenon of global warming as observed by climate specialists, was at first treated with 

skepticism. The Intergovernmental Panel on Climate Change (IPCC) estimates that during the 20 th 

century, the earth warmed up between 0.3 ° C and 0.6 ° C , while sea levels rose on average by 15 to 

12


25cm. It predicts a sharp increase in these phenomena over coming decades. Unless effective steps are 

taken in the near future, the 21 st century is likely to see temperature increases between 2 ° C and 5 ° C 

and rises in sea levels leading to the destruction of several cities (Dominque, 2002). 

The integrations of climate in urban design call for an interdisciplinary approach. They include 

architecture, physical geography and psychology. Vegetation is part of the geographical position. It 

plays the very important role to modify the microclimate in the scale of people and buildings, as it can 

be the ventilation in the urban area for cleaning of the air, as well as wind control. The climate is seen, 

heard and sensed. It is sensed principally as heat or cold, i.e. thermal comfort. The green area also 

would be the energy savings in the urban energy conservation. 

3.11 Green Structure and Air Quality 

With industrialization and road traffic development, air pollution has become a big problem in urban 

environment, which contents different pollutants shows in Table 1. It affects all of us. The average adult 

breathes over 11,000 liters of air every day. Children breathe even more air per pound of body weight 

and are more susceptible to the harmful effects of air pollution. 

Plants have an important role to play in moderating the air quality impacts of human activities. The air 

is filtered by the dust being collected on leaves and needles and by the rain flushing it down on to the 

ground. Impurities are absorbed, attach themselves to and are bound up in leaves. One hectare of mixed 

deciduous forest can collect an estimated 15 tons of dust per year. Ozone, in particular, can be removed 

from the atmosphere by plants at a rapid rate (Miller, 1997). “Smith and Dochinger (1976) stated, in 

theory a forest could remove about one-eight of O 3 content of the atmosphere in about one hour” 

(Miller, 1997). On the other hand, the role of trees in the storage of CO 2 , a gas that has been increasing 

in concentration in the atmosphere and contributes to the greenhouse effect. Trees take up CO 2 during 

their growth processes, effectively removing it from the atmosphere (Nowak, 1994). Through the 

process of photosynthesis, plants don’t only absorb CO 2 , but also produce O 2; 155m 2 of plant surface 

area can produce enough oxygen for one person for 24 hours. 

In the summer of 1991 the urban forest of Cook and DuPage countries (Chicago region) removed an 

average of 1.2 metric tons /day of CO 2, 3.7 tons/day of SO 2 , 4.2 tons /day of NO 2 , 10.8 tons/day of O 3, 

and 8.9 tons/day of particular matter smaller than 10 ∞ m (Nowak, 1994). 

Native landscaping practices can help improve air quality on a local regional and global level. Locally, 

smog and air toxics can be drastically reduced by the virtual elimination of the need for lawn 

maintenance equipment, which is fuelled by gasoline, electricity or batteries. All of these fuel types are 

associated with the emissions of the following air pollutants: CO, CO 2 , NO x , SO 2 , volatile organic 

compounds (VOC) and air toxics such as benzene. Gasoline lawn and garden equipment, on average, 

produces 5% of ozone forming VOCs in areas with smog problems (Miller, 1997). This equipment also 

emits toxics and particulates. Regionally, the NO x and SO 2 released from lawn maintenance equipment 

react with water in the atmosphere to form acid rain. Globally, native landscaping practices help to 

combat warming such as by taking in CO 2 and storing the carbon in the body of the plants, roots and 

soil. 

3.12 Green Structure and Energy Conservation 

When we feel too hot or too cold, we use more energy to moderate temperatures in homes and business. 

Skilful utilization of plants significantly reduces air temperature in summer, “…trees in a Davis, CA, 

parking lot reduced air temperature 0.5-1.5 o C ”(Scott et al., 1999). 

In order to increases the energy efficiency of buildings, planted tress on the west and east of a 

building’s windows and throughout a neighbourhood are some of the most effective ways to reduce 

peak energy demands (Sand, 1994). In many regions of the US, direct radiation from the sun creates 

uncomfortably high temperatures during the summer seasons. Locating densely foliated trees and shrubs 

13


to the southwest of facilities can reduce heat gain. In most regions, warmth from the sun is desirable 

during the winter. Deciduous tress planted to the south, east, and west of facilities will provide summer 

shade but will not block winter sun. American Forests has estimated that urban trees provide $4 billion 

in energy savings each year (e.g. through shading and cooling) (Moll, 1995). 

Air Pollutants Sources Health Effects Welfare Effects 

Nitrogen Oxides 

(NO x ) 

Sulfur Dioxide 

(SO 2 ) 

Carbon Monoxide 

(CO) 

Burning fuels, 

Automobiles 

Emitted from 

industrial, 

institutional, 

utility and 

residential 

furnaces, 

boilers, 

petroleum 

refineries 

Emitted from 

automobiles, 

buses, 

power plants 

and industrial 

process, heavy 

construction, 

farming 

equipment, 

residential 

heating 

equipment 

Asthmatics 

Heart and 

lung disease 

Slowing reflexes, 

drowsiness; high 

level CO can 

cause 

unconsciousness 

and even death; 

pregnant women 

may threaten the 

unborn child’s 

growth and 

mental 

development 

Harm vegetation, 

component of 

ozone formation 

and acid rain 

Toxic to plant 

life; component of 

acid rain; destroy 

paint pigments; 

corrode metals 

and harm textiles 

Prevention 

& 

Control 

Control motor 

vehicle, 

industrial 

combustion 

emissions 

Reduce the use of 

high sulphur 

fuels (use natural 

gas) 

Control motor 

vehicle and 


emissions; use 

oxygenated 

gasoline during 

winter time 

Ozone 

(O 3 ) 

Vehicles, 

Power plants, 

landfills, 


solvents, 

gas 

stations, 

farm and 

lawn equipment 

Coughing, 

choking, 

impaired 

lung function, 

reduced 

resistance 

to colds, 

heart 

disease, 

asthma, 

bronchitis, 

emphysema 

Corrodes 

Materials 

Such 

as rubber and 

paint 

Reduce motor 

vehicle emissions 

and nitrogen 

oxide emission 

through emission 

standards, 

reformulates fuels, 

inspection 

programs, and 

reduced vehicle 

use 

Particulate Matter 

Emitted from power 

Plants, ethanol 

plants, manufacturing, 

smelters, automobiles, 

wood smoke, dust from 

paved, rock crushing 

Heart or lung 

disease 

Impair visibility, 

contaminate 

materials and 

buildings, and 

corrode metals 

Reduce combustion 

emissions from 

motor vehicles, 

equipment, 

industries, power 

plants, and 

agricultural and 

residential burning 

Table 1: Air pollutants in air 

Source: Miller, 1997 

14


Figure 2: Solar radiation control in summer 

Source: William Spangle and Associate, Inc. 1989 

Figure 3: Solar radiation control in winter 


Planted roof system are widely acknowledged to offer both winter insulation and summer cooling 

benefits the advantages with regard to summer cooling are generally considered to be stronger. 

Summer: the roof can suffer from huge thermal fluctuations on its upper surface throughout the day and 

through the year. Planting the roof surface dramatically reduces the amount of solar radiation absorbed 

by the roof’s bare surface because it reduces heat build up by the following mechanisms: 

Photosynthesis: this is the process by which plants use the sun’s energy to turn H 2 O and CO 2 into 

sugars. Thus, some of the solar radiation is diverted to drive the plant’s growth rather than heat up 

the roof 

Evaporative H 2 O loss from the plant tissues: converting water from liquid into gas requires energy. 

The sun’s energy is used to loss from plant tissue is termed vapour-transpiration. The solar 

radiation is therefore diverted into evaporating water from the plant tissues rather than heating up 

the roof surface 

Evaporative water loss from the soil or substrate: much as for the plant tissue, solar radiation is 

diverted into evaporating water from the soil or substrate rather than heating up the roof surface 

Winter: planted roofs do reduce the buildings heat loss though the roof during the winter months. The 

processes are the insulating effects of the added mass and individual properties of the system 

components. It should be noted that the insulation efficiency of a planted roof depends on the amount of 

water held in the substrates and plant layers due to the water has a negative effect on thermal 

conductance. The biological activity in the roof zone of the planted system, which generates heat. 

As well as being economically advantageous, as less energy would be spent on air conditioning, the 

reduced energy requirements of the building would mean less production of CO 2 . Lightweight planted 

roof systems can be as the sustainable solution for keeping our buildings workable and liveable in the 

years, reduced CO 2 production by the building less energy utilized and removal of CO 2 by the roof 

plants, at the same time release of O 2 are two vitally important environmental benefits of roof planting. 

Green structure can not only be used for energy saving system, but can also be an energy production 

source called bio-energy, to support the use of renewable energy sources for generating electricity and 

heat. 

3.13 Green Structure and Wind Control 

Plants can modify wind speed on the ground for distances up to thirty times their height (Figure 4). 

Dense masses of large evergreen trees planted to intercept prevailing winter and summer winds and 

increase the liveability of outside spaces. Drifting snow may be controlled by a series of plant barriers 

which alternately increase and decrease wind velocities. This can be accomplished by sweeping an area 

of snow with strong winds and depositing the snow where wind velocity decreases (Figure 5). 

Meanwhile, plants also can be used to break, guide, deflect or filter the wind and thereby alter its 

effects. To properly design for wind control using plant materials, a basic knowledge of air dynamic is 

necessary. Information about the directions of prevailing winds and their average speeds for different 

season of the year is also necessary. 

15


Figure 4: Tress affect wind currents 

Source: USAF, 2000 

Figure 5: Snowdrift control 

Figure 6: Windy control- directional 


3.2 N, P and Heavy Metals Removal by Green Area 

Civilization has dealt with wastewater for thousands of years. Normal storm water and uses of water for 

hygiene, consumption, manufacturing generates a pollutant load on the resulting wastewater. In order to 

prevent contamination of drinking water supplies and the surrounding environment, wastewater must be 

isolated until pollutant removal is accomplished. In EU there are the requirements for urban wastewater 

as shown in Table 2. Vegetation and substrate can absorb a range of pollutions including nitrogen, 

phosphorus and heavy metals such as cadmium, copper, lead and zinc. Wetland as one kind of methods 

can efficiently reduce BOD, suspended solids, N, P, heavy metals, organics and pathogens. In the 

context we illustrate the wetland functions in storm water treatment. 

Storm Water 

Storm water originates from runoff of rainfall on roofs and streets. Pollutants in storm water originate 

from surfaces such as streets and roofs that are washed with the rainwater. The variation in pollutant 

content is large and varies depending on the type of surface that the run off comes from. Table 3 shows 

the difference sources in the cities contribute with different amount of pollutants to the storm water. 

Urban runoff after a rainfall or an occasion of snow melting is the most polluted. It makes it an 

important task to treat flush before it enters a distribution system, wastewater treatment plant or natural 

recipients. In general, after treatment storm water can be used for water supplies of clothes washing, 

city parks and garden irrigation and develop recreation activities such as boating and skating. 

Storm Water Treatment Process 

Primary treatment is to reduce big particles from storm water 

Secondary treatment method is using the green roofs to absorb particles, heavy metals and nutrients 

Tertiary treatment methods are used in the wetland systems: 

16


Physical process: sedimentation, filtration, infiltration and evaporation 

Chemical processes: adsorption and crystallisation 

Biological processes: plant uptake, biological degradation, nitrification and denitrification 

Primary 

Treatment 

Gross 

Pollutant 

Trapping 

Infiltration 

& 

Filtration 

Secondary 

Treatment 

Sedimentation 

Sedimentation 

Filtration 

Tertiary 

Treatment 

Biological Uptake 

of pollutant 

Absorption of 

Pollutant to sediment 

Figure 7: Storm water treatment process 

Source: Lecture Notes from Waste Water Treatment, 2003 

Parameter Concentration Minimum Reduction % 

BOD (at 20C without nitrification) 25mg/L 70-90 

COD 125mg/L 75 

TSS 

35mg/L 

(p.e. > 10 000) 

60mg/L 

(p.e. < 10 000) 

90 

70 

P 

2mg/L 

(p.e. 10 000 – 100 000) 

80 

1mg/L 

(p.e. > 100 000) 

N 

15mg/ L 

(p.e. 10 000 – 100 000) 

10mg/L 

(p.e. > 100 000) 

70-80 

p.e. = Population equivalent, defined as contributing 0.06kg BOD 5 per person per day 

COD = Chemical Oxygen Demand TSS = Total Suspended Solids P = Phosphorous N=Nitrogen 

Table 2: EU requirements for urban wastewater 

Source: EC Directive 91/271/EEC 

COD N P Pb Zn Cu 

Traffic *** ** * * ** * 

Erosion ** * ** * *** *** 

Precipitation - *** ** ** *** ** 

Animal Droppings * ** *** * * * 

*** = High ** = Medium * = Low 

Table 3: Different amount of pollutants in storm water from different sources 

Source: EC Directive 91/271/EEC 

17


Wetlands 

Storm water that could be treated by constructed wetland systems has been considered as a component 

of a treatment processes, provide a low energy, low-tech method of removing pollutants. 

Minimal energy consumption: elevation differences in the wetland can be provided to allow 

wastewater to flow by gravity through the wetland system. Energy consumption in the treatment 

system is generally limited to the amount of energy consumed by the primary treatment method. 

Minimal use of chemicals: the wastewater treatment reactions in a wetland depend on physical, 

chemical, and microbial processes that occur naturally in the system. In some wetland systems long 

detention times and exposure to sunlight provide sufficient disinfections and as a result additional 

means of disinfections are unnecessary. 

Low-tech: wetlands are designed to have simple hydraulic and mechanical systems. Since 

the treatment processes are naturally carried out, operators do not have to monitor the 

treatment process. The primary tasks of the operator are to keep the hydraulic system 

running, manage wildlife and the occasional harvesting or burning of excess vegetation. 

With wetlands it may not only efficiently to reduce storm water pollutants, but can also be an aesthetic 

addition to a community. As such they provide open space and associated recreational activities (i.e. 

hiking, bird watching etc.). At the same time it provides a buffer to natural aquatic ecosystems, and 

create habitat for flora and fauna. Of all habitat types, wetlands are among the most productive 

(Adames et al.,1986; Tiner, 1984). A number of animals spend all or part of the year in or near wetlands 

and animal diversity is generally greater in inland wetlands than in other inland areas (Tiner, 1984). 

These wetlands ecosystem can be very biologically productive area. Wetland plants thrive in constant 

or intermittent soil moisture. Ideally, these plants contribute to the shelter or sustenance of the native 

wildlife while adding to the natural beauty of the area. In common, there are three basic types of 

wetland systems: natural wetlands, constructed wetlands with surface flow (Figure 8a) and constructed 

wetlands with subsurface flow (Figure 8b). FWS (free water surface) wetlands are characterized by an 

open water surface exposed to the atmosphere. FWS are typically composed of one or more shallow 

cells ranging in depth from 5 cm to more than 1m, fringed with emergent reeds and macrophytes. FWS 

wetlands are diverse system containing both shallow and deep zones, aerobic and anaerobic conditions 

and a broad range of habitats from ephemeral to aquatic. 

Figure 8a: Constructed wetland with surface flow 

Source: Komex Environmental Ltd, 2004 

Wetlands Construction Design 

Based upon constituents targets, the following materials or parameters were designated for primary 

consideration in design of the constructed wetlands system: copper, lead, mercury, total residual 

chlorine, total suspended solids (TSS), biochemical oxygen demand (BOD), chemical oxygen demand 

(COD) and pH. Constructed wetlands generally operate at neutral pH unless influents are strongly basic 

or acidic. The pH in wetlands ordinarily represents the amount of anaerobic decomposition and 

Figure 8b: Constructured wetland with subsurface flow 

Source: Komex Environmental Ltd, 2004 

18

subsequent organic acid production and the amount of photosynthetic activity by algae. 


Sedimentation basins are structured placed within a storm water wetland system to capture coarse 

sediment from storm flows. Sedimentation basins differ from constructed wetlands in that they reply 

primarily on physical processes to treat the water, whereas a wetland relies primarily on biological 

processes. However, it is important to remember the limitation of sediment basins with respect to the 

treatment of dissolved pollutants that are not associated with sediment and so cannot be treated through 

physical process. Sedimentation basins are designed to trap coarse sediment upstream of a natural or 

constructed wetland or creek system. The basins temporarily detain storm water so that the velocity of 

storm flows is reduced and the sediment falls from the water column. Typically, a large proportion of 

nutrient in storm water will be bound to the suspended sediment particles. Therefore, since 

sedimentation basins are designed to facilitate the settling of sediment, they are also effective at 

removing a large proportion of particulate-based nutrients from the water column. The rate at which a 

sedimentation basin removes sediment from the water column is affected by the sediment particle size, 

the velocity of the water and detention time (the length of time that the basin retains the storm water). 

Meanwhile, the basin was designed as flow management to release the volume of storm water gradually 

over time. It can be managed to assure that water was provided to the constructed wetlands during 

summer dry periods with minimal rainfall. The primary concern during the summer dry periods with 

minimal rainfalls is maintenance of water depth in the constructed wetlands. Both the base flow from 

the process area and the water from the flow management basin can be used to assure the constant 

presence of water in the constructed wetlands. 

N Removal 

Nitrates are converted to dinitrogen gas by denitrifying bacteria in anoxic zones. Nitrogen is also taken 

up by plants, and incorporated into the biomass. There are several genera of heterotophic bacteria 

including, Achromobacter, Aerobacter, Alcaligenes, Bacillus, Brevibacterium, Flavobacterium, 

Lactobacillus, Micrococcus, Proteus, Pseudomonas and Spririllum are capable of dissimilatory nitrate 

reduction. This is a two step processes. The first step is conversion of nitrate to nitrite. This stage is 

followed by the production of nitric oxide, nitrous oxide and nitrogen gas. The conversions are shown 

as below: 

NO 

− ⇒ NO 

− ⇒ NO ⇒ N O ⇒ 

3 2 

2 

N 

2 

The presence of dissolved oxygen suppresses the enzyme system needed for denitrification and is a 

critical parameter. The optimum pH range lies between 7 and 8. However, alkalinity produced during 

denitrification can result in rises in pH. Denitrification is also strongly temperature dependent and only 

proceeds at very slow rates, if at all, at temperature below 5 o C . 

P Removal 

The interaction of redox potential, pH, Fe, Al and Ca minerals control phosphorus sorption in wetland. 

Fe and Al oxides and hydroxides, calcite and organometallic complexes retain inorganic P. Biological 

oxidation results in the conversion of most P to the orthophosphate forms (H 2 PO 4 - , HPO 4 - , PO 4 3- ). 

Removal of these latter forms in wetland occurs mainly as a consequence of adsorption, complexation 

and precipitation reaction with Al, Fe, Ca and clay minerals in the bed matrix. Although there is some 

uptake of P into plant biomass this is insignificant compare to the effects of adsorption. In acid 

condition inorganic P is rapidly adsorbed in wetland on hydrous oxides Fe and Al may precipitate as 

insoluble Fe phosphates and Al phosphates.Reduction of phosphorous to gaseous hydrogen phosphates 

under anaerobic conditions by a particular strain of anaerobes and subsequent release to the atmosphere 

is theoretically possible. 

Heavy Metals Removals 

Wetland species have a well-established ability for direct up taken of heavy metals. It should be noted 

that direct up taken is an active process, requiring the plant to be alive. Plant matter will liberate its 

metal content when decomposing. 

Copper removal: weathering of copper minerals results in background copper concentrations in natural 

surface waters usually well below 20ug Cu/L (USEPA 1980) and sediment concentrations ranging from 

1 to 10 mg Cu/Kg. However, much of the copper entering aquatic systems is due to anthropogenic 

19

activities (Moore 1990; Dugan 1991). When copper enters aquatic or wetland systems in solution, it 

wills speciate into numerous forms or compounds as it interacts with components of the ecosystem. 


Several processes determine the fate of copper in wetlands: complex formation, sorption to hydrous 

metal oxides, clays or organic materials, formation of insoluble species (e.g. metal sulfides), and 

bioconcentration / bioaccumulation. Because of its lithic biogeochemical cycle, copper has a high 

affinity for sediments and a short residence time in solution. In this system, the copper is sequestered 

from the aqueous matrix to the hydrosoil of the wetland and allowed to speciate to nonbioavailable 

forms. 

Lead removal: to permit particulate lead to settle and to precipitate the soluble lead in the wetland 

hydrosoil as PbS. Lead will also bind with carbonates and hydroxyl ions at circumneutral and higher pH 

with both PbCO 3 and PbOH settling rapid to the hydrosoil. The lead compounds in the hydrosoil should 

be stable and retained within the system. Further, the plants in the constructed wetlands will serve to 

filter any particulate associated lead from the water column. 

Mercury removal: constructed wetland system can be designed to precipitate mercury in the wetland 

hydrosoil as cinnabar (HgS). Mercury in bottom sediments is strongly held by the following binding 

mechanisms: (1) sorption on hydrated ferric oxides (2) surface sorption or ion exchange on mineral ion 

exchangers such as montmorillonite or (3) sorption and or chemical binding with organic material and 

sulfur containing matter. The fundamental principle for sequestering mercury from the effluent in the 

constructed wetland system is via formation of relatively insoluble HgS and precipitation in hydrosoil. 

It will be important to avoid methylation of mercury in these constructed wetlands by regulation of 

water depth and flows to maintain the desired reduction-oxidation (redox) potential in the hydrosoil. 

Total Suspended Solids Removal 

The process used for treatment of total suspended solids (TSS) in the constructed wetlands system is 

based on Stokes’ Law. As the velocity of the water flow into the flow management basin and 

particulates can settle from the water column. Thus, settleable and suspended solids are removed from 

effluent by physical sedimentation and filtration processes. A significant portion of suspended solids 

will settle from the water in the upstream flow management basins prior to entering the constructed 

wetlands. If water leaving the retention basins still contains appreciable amounts of suspended matter, 

the constructed wetlands will provide filtration by wetland vegetation to further remove residual 

suspended solids. 

BOD Removal 

Removal of biochemical oxygen demand from effluent is achieved primarily through sedimentation/ 

filtration processes in the constructed wetlands. Organic matter (BOD) accumulated in constructed 

wetlands is largely degraded through aerobic microbial metabolism, and to a lesser extensive surfaces 

(plant and hydrosoil) in the constructed wetlands provide numerous opportunities for BOD 

transformation. The relatively high surface area to volume relationship in the water column of the 

constructed wetlands assures that ample dissolved oxygen is available for sufficient aerobic 

decomposition of BOD in the wastewater. These processes (both physical sedimentation and microbial 

metabolism) will function to decrease the BOD associated with the effluent outfall. 

Wetlands Maintenance and Operation 

The constructed wetlands require relatively little maintenance. Additional long-term maintenance 

required for the constructed wetlands includes: observation and clearing of the inflow and outflow 

structure; observation and removal of burrowing animals, and observation and control of excessive 

herbivory (insects, mammals etc). Operation of the constructed wetlands consists primarily of adjusting 

water depth for maintenance of the desired redox potential. Redox potential of the constructed wetlands 

hydrosoil can be monitored with simple platinum electrodes. These electrodes can be “permanently” 

installed to minimize stabilization time. 

Selection of Wetland 

Successful performance of treatment wetlands is based on appropriate integration of wetland 

macrofeatures: hydrosoil; hydroperiod and vegetation (Hawkins et al., 1997; Gillespie et al., in press) 

20

- Hydrosoil: hydrosoil selection is based on pH and redox considerations; ability to sequester metals 

and promote other mitigation processes (e.g. aerobic microbial degradation of BOD); appropriate 

chemical and physical characteristics (e.g. organic matter content); minimal background contamination; 


compatibility with selected wetland plant species; availability of nutrients for plant growth and location 

and availability. 

- Hydroperiod: based on process flow rates and availability for land for treatment wetlands 

construction, a hydroperiod had to be established that would facilitate the desired transfers and 

transformations of effluent constituents, as well as meet the hydraulic requirements of the selected 

wetland vegetation. Water depth maintained in the wetlands is important due to its influence on 

hydrosoil reduction or oxidation. 

- Vegetation: selection criteria for the recommended wetland vegetation include: potential effects on 

hydrosoil pH and redox; compatibility with selected hydrosoil; compatibility with local climate; ability 

to tolerate hydroperiod fluctuations (i.e. water depth and hydraulic retention time); compatibility with 

objective (i.e. provide detritus to yield the reducing power to maintain reduced conditions without 

contributing significantly to BOD); resistance to herbivory; cost and availability and nonexotic species. 

It was also be important for the wetland vegetation to contribute organic carbon in the form of detritus 

to provide reducing energy to maintain the negative redox in the hydrosoil. Use of a bulrush in 

remediation of Cu, Pb and Zn has been established in previous studies (Hawkins et al. 1997; Gillespie 

et al. in press) with objectives consistent with that effluent outfall. 

Storm Water Treatment Strategies 

The metals, copper, lead, and mercury are sequestered in a similar manner in that they are settled to 

sediments or will be transformed into very stable metal sulfides. It will be important to sustain desired 

redox conditions in the wetland hydrosoil to accomplish formation of metal sulfides and prohibit 

formation of methyl mercury. Currently, TSS is being removed by primarily by settling in the flow 

management basin, however, filtering within the constructed wetlands system will increase as the plant 

density increases with system maturity. Similarly, BOD is being removed by primarily settling, 

however, filtering within the constructed wetlands system will increase as the plant density increases 

with system maturity. 

3.3 Green Structure and Biodiversity 

Wildlife populations and diversity is one of most important indexes to indicate urban environmental 

quality. Equally, plant materials support wildlife and can be used to increase or decrease the number 

and variety of animal species due to green corridors with flora can support wildlife food, shelter, 

movable place and so on. For instance, constructed green roofs attract birds. These birds use the roof to 

search for food, preening and cleaning, searching for nesting material, nesting and roosting. 

Goldfinches require a varied plant layer to supply the range of seeds that it prefers. 

Three urban categories relevant to wildlife are distinguished: downtown, urban residential, and 

suburbia. The heavily developed downtown is usually at the centre, followed by concentric zones of 

urban residential and suburbs. There is a progression outward of decreasing development and increasing 

vegetative cover. Species richness and diversity is extremely low in the inner cover. The urban 

residential zone is characterized by a denser and more varied mosaic of vegetation shade trees, lawns, 

hedges and planted gardens; approximately 40% of the land’s surface is covered by impervious 

material. This region is characterized by a variety of bird species including scrub jay, mockingbird, 

house finch, (Guthrie 1974, Sproul 1975, Williams and Monroe 1976). Suburban areas with mature 

vegetation closely approximate the natural environment. In addition to landscape gardens and lawns, 

relatively large tracts of adjacent natural vegetation such as chaparral, grasslands, and oak woodland 

abound. Wildlife diversity increases while species density decreases (Thomas and DeGraaf 1975) and 

proportionately greater numbers of native species occur. These areas often provide valuable cover for 

urban wildlife, especially when native plant species can be maintained. From this view, protect nature 

conservation is very important for biodiversity. In many countries, biodiversity in forest environments 

is protected by nature conservation law and forest law-list of protected habitats, list of especially 

important habitats. 

21

Thoren and Nyhuus (1994) give some basic principles to be regarded as guidelines for green planning 

featuring biological diversity in urban areas: 


The distance between the green cores should be as short as possible 

It is preferable that these areas are more or less circular. The latter can be old urban forest, 

hayfields, or established parks with big, old tress. It is better for an organism to meet different sizes of 

areas than several smaller ones. A big area is often a better production area for plants and animals 

compared to a smaller area 

Green corridors provide habitat connectivity necessary for naturally dispersing species. The 

corridors should be designed and managed for native species, which means consideration to species 

sensitive to fragmentation and human disturbance. The corridors also allow people to move between 

green areas. 

Buffer zones around bigger areas are very useful to maintain an area that is not so exploited. For 

example, an area of one-family houses with gardens, or an allotment area can act as a buffer zone. 

3.4 Green Structure and Health 

Today, stress is regarded as one of the most important factors related to ill health in modern society 

(Nygren et al. 2002). Everyday life is characterized by a type of stress: an imbalance between what we 

are able to accomplish and what is demanded of or expected from us, which can lead to a feeling of 

being unable to control our life. Normal stress reactions include increased muscle tension, increased 

sweat-gland production, increased pulse, increased adrenalin production (our fighting hormone), 

increased cortisol production (our wakefulness hormone), reduced melatonin production (our sleeping 

hormone), and so forth. 

Nature helps people to concentrate better and to recover from “directed attention fatigue” (Kaplan 

1990), because nature contains a wealth of restful information that does not cause tiredness in humans 

(Kaplan et al. 1998). 

Positive physiological reactions are lowered heartbeats and blood pressure and calming. In Ulrich et al 

(1991) showed a gory film on industrial accidents to 120 people. Half of the people were then shown a 

nature film, whereas the other half was shown a film on the city, with sequences of buildings and 

traffic. The subjects’ heat beat; muscular tension and blood pressure were monitored throughout. All 

subjects exhibited strong signs of stress during the first film, on industrial accidents. The stress levels of 

the half of the subjects that then watched the nature film had returned to a normal level after 46 

minutes, whereas the half that watched the film on buildings and traffic continued to exhibit high stress 

levels. 

Urban open green spaces play an important part in offering town-dwells a more stress free environment, 

irrespective of sex, age or socio-economic background. The more time people spend outdoors in urban 

open spaces, the less they are affected by stress because humans have very deep emotional, symbolic, 

and spiritual ties to trees (Dwyer, Schroeder, and Gobster 1994), trees can induce feelings of serenity. 

Research in the field of environmental psychology shows that there are above all four qualities that are 

important in the major green areas, namely: wildness, diversity of flora and fauna, cultural 

characteristics and spaciousness (Regionplane och Trafikkontoret, 1998). People tend to seek out places 

where they feel competent and confident, places where they can make sense of the environment while 

also being engaged with it. If this need is not satisfied it leads to the long time stress followed by 

decreased ability to work and loss of any motivation as a results of stress. In 1984, Young and Crandall 

measured self-actualisation in wilderness areas compared to other more developed environments. They 

found in wilderness area that in comparing the more active users in the panel with less active, selfactualisation 

increased for both groups but significantly more for the active users. They concluded that 

the results suggest that wilderness use may cause increase in self-actualisation either directly or through 

moderating variables. When exposed to unfamiliar and challenging tasks, one often develops new skills. 

If we agree that through skill development, self-confidence is built and that this is one of the best 

22

defences against unhealthy peer pressure, then it could be argued that building skills is indeed a healthy 

activity. Wilderness areas can challenge visitors to acquire new skills even when they are unaware that 

the process is occurring. Planning, group participation, physical exertion, humility, fear and thinking on 


your feet all help develop skills that we can use everyday. Outdoors activities and exercise help the 

body to better endure physical and psychological strains such as stress (Åstrand 1987; Blair et al. 1989). 

It is generally agreed that a long day-hike, an overnight, or an extended trip can have physically 

challenging aspects. Most of self-sufficiency is the product that is realized through the process of 

preparation, planning, and then exposing yourself to the unknown. Wilderness can facilitate meaningful 

changes in one’s psychological well being, benefiting the user through an improvement in their 

psychological condition. 

Strategies and Design: Such a green environment should preferably be easy to access, induce recovery 

and provide the visitor with an opportunity for rest. The distance from home to the nearest urban open 

green space could be a decisive factor in relation the use of parks. Urban open green spaces should be 

used by all social classes, by both sexes and by people of all ages. 

3.5 Green Structure and Noise Reduction 

Green spaces help combat noise, as vegetation absorbs sound like as tress, shrubs, groundcovers and 

turf. If high enough, wide enough, and dense enough, vegetation can decrease highway traffic noise. 

Plants diffract and break up sound waves, changing their direction and reducing their intensity when 

sufficiently massed. A 200-feet width of dense vegetation can reduce noise by 10 decibels, which cuts 

the loudness’ of traffic noise in half. Figure 11 shown the traffic noise is cut by forest in half (USAF, 

2000). 

Figure 10: Plants can reduce noise 


3.6 Green Area and Surface Erosion Control 

Figure 11: Noise cut in half 

Source: FHWA, 1997 

Wind and water can erode valuable topsoil. Plants, especially grasses, can prevent or control erosion by 

stabilizing the soil through their root structure. Exposed soil on cut banks and steep slopes should be 

immediately planted with grasses and/or native low-growing shrubs and spreading groundcovers 

(USAF, 2000). 

23

3.7 Green Structure and Glare Control 


Figure 12: Plants can be used to contorl 

Trees, shrubs and other vegetation can effectively reduce 

erosion 

glare and reflection when placed between the 

light source and the observer (USAF, 2000). Source: USAF, 2000 

Figure 13: Trees can reduce the effect of solar glare and reflection 


24


4. Case Study - Enköping 

4.1 Introduction 

Enköping is a small Swedish town situated in the dense part close to lake Mälaren and the nearby big 

cities Stockholm, Uppsala and Västerås, which are within 35-45 minutes reach. The municipality has 

over 38,000 inhabitants. Within that amount about 20 000 people live in town and the remaining 18 000 

in the countryside. It has about 46% farming land and about 37% forests. The modern Enköping’s trade 

and industry mainly consist of small-medium sized companies, representing traditional engineering 

industry and agricultural enterprises. At the moment, Enköping is one of the most rapidly growing 

municipalities in Sweden and has become an attractive town to live in. The large Lake Mälaren with its 

clean water, beautiful environments and three golf courses nearby attract people (Figure 14). 

25

4. Case Study-Enköping 

In 2003, Enköping received the Golden Award in the international competition "Nations in Bloom", 

held in Apeldoorn, the Netherlands. In competition with 200 municipalities from all over the world (in 

the category "with an average daytime population of 20 000–75 000 people"), Enköping was announced 

as the most livable community. Every season Enköping has its special set of events. In the spring we 

may see the spring market, with stalls and amusements. In the early summer there is a Culture Week, 

where many difference cultures meet and put on entertainment, serve various national dishes and 

arrange different events. Midsummer is celebrated in traditional Swedish fashion with dancing and 

games around the maypole. Some Monday evenings during the summer local and more renowned 

artists provide entertainment on the stage in Skolparken. During the Enköpings harbor festival around 

the beginning of the July, the town really blooms. Streets and squares fill with life and people of all 

ages. In the Figure autumn 14: there Enköping is the city traditional map Mickelsmäss market in Örsundsbro, this being its 29th year, 

attracting Source: tens of thousands Enköpings of Kommun visitors to the municipality. 

4.2 Selected Components of Green Structure: Public Parks, Pocket Parks and 

Gardens 

The parks in Enköping we may classify into two main categories: district park and pocket park. The 

former one normally is a medium to large site with clearly defined boundaries, and consist of a few 

discrete areas so that people can separately play or sit quietly, this site may be with some having a 

number of facilities for people to do, reasonable access for everybody on foot, car or public transport. 

Pocket park is a small green area normally secreted between houses or buildings, it gives an identify at 

place to live, people may have coffee, interaction and sunshine inside. Accessibility is often limited due 

to its location. The district park and pocket park in Enköping city has shown in Figure 15. 

District Park: 

Dream Park 

Kloster 

School Park 

G.Alof 

Kölnbacksparken 

Afzeliiplan 

Pastor Spaks Park 

Väntparken 

Water Park 

Vasterleds Park 

Nya Kyrkogården 

Pocket Park: 

Fridegård's Park 

Rådhusgården 

Munksund Well 

Kaplanen 

Blombergs 

Fisktorget 

Westerlundska 

Romberga garden 

200 meters from Park 

= 5-6 mins walking 

400 meters from Park 

=9-10 mins walking 

Figure 15: Location and accessibility of District Park and Pocket Park 

Each park in Enköping is unique and often the name of it depicts its characteristics. It cans active all the 

senses: sight, hearing, smell, and taste. Also the temperature sense, the muscular sense, and the sense of 

26

touch are activated when, for instance, one put one’s hand on a stone warmed by the sun or the sense of 

balance is exercised when one walks along an uneven path, to feel the irregularities of the ground under 

one’s feet, see and rejoice at the tender blossoms of the witch hazel in the middle of winter, smell the 


sweet odour of the rose, hear the singing of the wind in the poplars, and feel the wind in one’s hair. It is 

a good garden that can bring the visitor a message of life, lust and cyclic change and convey feelings of 

calm, safety, strength, beauty or sensual stimulation. This is a popular way to escape the stresses and 

strains of modern life for a few precious hours. It is also a favorite place for school and senior citizen 

outings, for barbecues, nature walks and simply to enjoy the delightful setting. 

The Dream Park This park was designed by the Dutch designer, Piet Oudolf and laid out in 1996. Tall, 

perpendicular cylinder shaped beech hedges grow in combination with a variety of 220 different 

perennials. The visual effect created by the blue streams of threee kinds of Salvia Nemorosa is much 

appreciated by visitors. The abundant use of ornamental grasses and other vertical growing perennials is 

an aim to echo the naturalness, drawing on an appreciation of natural habitats rather than a traditional 

garden, thus emphasising depth and an illusion of scale. The colour compositions are subtle but 

distinctive forms and striking contrasts in height and growth habits, in foliage texture and flower head 

shapes create the visual image of a brilliant firework display. The seasonal diversity of the perennials 

ensures a distinctive feature to the place. Even after the flowering period the park still maintain its 

attraction values when seed-heads and parchment-like grasses celebrate their beauty with breathtakingly 

frosted winter effects. In this park paved with stones and used as a pathway for walking and 

cycling alongside the river on one side, an exploitation to the senses using colours, textures, and the 

shape of the plants creating a stylish natural growth habitats with highly romantic effects. A place 

where you can just sit and enjoy life in peace and quiet watching the birds on the the river or take a 

stroll along the pathway leading round the park. One of city library is lying in this park, the people may 

relax themselves very well when they feel tired on readings. 

School Park A park from the Victorian era with a rolling grass landscape and a magnitude of attractive 

trees. This park is a valuable asset to the town's people as far as recreational and cultural aspects are 

concerned. Resting on the slopes of the woodland ridge of Kyrkåsen ,which overlooks the town and its 

surrounding, makes it an exciting and stimulating place for rambling or strolling around, pick- nicking 

in the summer and tobogganing and skiing in the winter. There is also an adventure playground which 

attracts children of all ages. In the summer there are several cultural events arranged on or in the close 

vicinity of the outdoor stage. Not far from the stage is another famous feature, a bust of Ernst 

Westerlund, a well-known doctor who lived and worked in Enköping at the turn of the century. 

Rådhusgården as one of new herbal garden (2001/2002) near the Museum of Enköping. Here you find 

ample feed for your senses; from the old symbol of the city the horse-radish to thyme and lavender. The 

detailed text description of each plant you may find. 

School Park 

Rådhusgården 

Photo by: Enköping Park Office Photo by: Enköping Park Office 

4.21 Accessibility 

Public parks and gardens, should strive to be accessible to everybody, to be a design for all (Welch, 

1995). In every day life there is an approximate 10 minutes limit that people can accept as the time to 

move to a green area. If the time increases from 10 minutes to 13 minutes about 50% of visitors 

27

disappear. Within the space of 10 minutes, an older person can walk about 400 meters; children under 

12 years of age and adults cover about 700m, while an adult on a bike travels about 2,500m. Figure 15 

shows the accessibility to parks in Enköping. 


4.22 Public Life 

An investigation, which includes site observations and interviews with users, was carried out in three 

different parks in Enköping to examine activities in the public parks see Appendix. It was intended as a 

test to check for what kind of activities and how many people use the space. Because of time limitation, 

the test was carried one hour in each park on Oct.6 th .2004 

The first tested park Kaplanen is a circular-shaped elevated park adjacent to old buildings (2-4 floors 

height). The cherry trees, Prunus fruticosa "Globosa" give an impression of enclosure and a solitary 

wing nut tree, Pterocarya fraxinfolia, adds character in addition to the bordering Craftsmen's cottages. 

In this park, there were no more than five people staying in and taking their rest here. Only a few 

interactions between people, who was standing in the outer part of this park due to its inconvenient 

accessibility (elevated squared). Two roads surround it. People are coming and going for their business. 

The most frequently pedestrian routes are shown in Figure 16a. The outdoors space and activities are 

shown in Figure 16b. 

The second tested park is Kloster. It was the Franciscan monks, who founded the monastery during the 

14th century on the former island in the town estuary. The building was pulled down in the 17 th , century 

but in the 1930s excavations revealed the remains of the monastery. Towards the end of the 1980s an 

extensive renovation of the park area was undertaken. The river bank between the river and the 

embankment pathway is planted with luxuries and voluptuous perennials divided between horizontal 

and vertical growing weeping plants in order to maintain the contiguity to the water. Two jetties with 

seats on the river provide a pleasant resting places for the visitor, together with the floral garden on the 

opposite side of the foot path. The large central grass area, the playground and the boule court provide 

excellent recreational facilities. Inhabitants use this park for different proposal in different time. Around 

lunchtime, a lot of people who work nearby prefer taking a walk in this park. Retired people with their 

grandchild have fun here. In the afternoon after work time, the park for leisure proposal dramatically 

increases, many people sitting along the riverbank, enjoying fishing, interacting and taking the view of 

it. People walk around with their pets. In this park, there are three main pedestrian routes. People use 

three of them frequently. Two pedestrian routes, which paved near the residential house are used quite 

often by the people who are living beside the Kloster. The third one, which paved along the riverbank is 

much often used by outside people to pass through the park. (Figure 17a.) The people stated: “during 

the summer time, lots of kids play in the park and picnic here.” Young people sit along the riverbank 

and take their drinking. They like to come here and meet friends if weather is good. Figure 19a shows 

the numbers of all types of outdoor activities. Figure 19b shows the comparison of the outdoor activities 

types in different time. 

The last tested park-Water Park is located at the edge of the town. It is an artificially shaped water body 

to clean storm water. It is meandering in the natural landscape with rich in birds and species. Water 

Park with very open view, but only a few people use it due to poor public facilities. Asphalt road are 

paved around the park. People follow these pedestrian routes through the park and enjoying towards 

both sides (Figure 18a). 

4.23 Human Health 

About a century ago, many jobs were physically strenuous with long working days and little rest. 

Today, in the Western World, most physically strenuous jobs have disappeared. Most ill health that are 

on the increase today are related instead to behavior involving risk, such has having a sedentary 

lifestyle, smoking, using drugs, consuming too much fatty foods, and leading a stressful life. (Orsega- 

Smith et al., 2000). In Sweden, the most widespread illnesses among people aged 20 to 60 years are 

related to aches and depression. These illnesses are largely stress-related. Recent investigations show 

that both school children and gainfully employed people in Sweden suffer workplaces. For 2001, the 

28

costs for the Swedish public sector have been calculated to be at least ten billion Euros, and for 

burnout-depression syndromes alone, the total costs have been estimated to about 8 billion Euros per 

year. 


Kaplanen Park, Enköping – Oct. 6th. 2004 

Figure 16a: Survey of Pedestrian Routes in Kaplanen 

Pedestrian routes (identified during site’s observation 

Oct. 6 th 04 by Chen Jie) 

Photo 1 by Chen Jie 


29


Figure 16b: Outdoors space and 

activities in Kaplanen 


Kloster Park, Enköping – Oct. 6th. 2004 

Figure 17a: Survey of Pedestrian Routes in Kloster 





30


Figure 17b: Outdoor activities 

in Kloster 


Water Park, Enköping – Oct. 6th. 2004 


Figure 18a: Survey of Pedestrian Routes in Water Park 





Figure 18b: Outdoor space and 

activities in Water Park 

31



Number of outdoor 

activities 

Comparison of public activities in different time in 

Kloster Park (Oct.6th.04) 

20 

15 

10 

5 

0 

4 

13 

6 

6 

17 

2 

5 

8 

4 

5 

1 

0 

12:00-13:00 

15:30-17:00 

Interaction 

Passing by bicycle 

Passing by foot 

Walking around 

Doing sth. 

Staying 

Public Activities Types 

Figure 19a: Numbers of all types of outdoor activities 

Number of outdoor 

activities 

20 

15 

10 

5 

Numbers of outdoor activities in Kloster Park 

(Oct.6th.04) 

Interaction 

Passing by bicycle 

Passing by foot 

Walking around 

0 

12:00-13:00 15:30-17:00 

Time 

Doing sth. 

Staying 

Figure 19b: Comparison of the outdoor activities types in different time. 

Outdoor areas that provide environments free from demands and stress, and that are available as part of 

everyday life, could have significant positive effects on the health of town-dwellers because a nature 

area that sends messages of safety are restorative. It allows the visitor’s whole body to relax and recover 

from stress. These messages may be a matte of humankind’s spontaneous and unconscious response to 

natural stimuli signalling safety. 

Doctor student Ulrika A. Stigsdotter did one of the investigation of gardens can influence the level of 

stress of employees at workplace. A questionnaire was sent by post to 2,200 individuals of all ages, who 

were selected at random and lived in nine Swedish cities including Enköping. The result shows that 

more than two thirds of the respondents say that they have access to a garden at their workplace. Level 

of stress can be decreased as the workplace greenery index increases. Table 4 is showing the 

relationship between stress level and workplace greenery. In her papers she also shows the strong 

significant between trivsel 1 and the stress by the questioned the local people “Do you experience trivsel 

1 Trivsel: pleasure, comfort and well-being 

32

at your workplace??” The respondents gave their answers on a seven grade scale from “No, not at all” 

to “yes, very much so”. 

She also expected to find stronger connections between spending time in a garden and stress level than 

between having a view of a garden and stress level, but the results suggest that the effect of spending 


time in a garden and of having a view of one is the same both with regard to stress reduction and trivsel 

at the workplace. It means taking in a view may be important, just as important as spending this time in 

the garden. 

My conclusion is that lying out gardens at workplaces may be an effective, comparatively cheap and 

aesthetic weapon to be taken in consideration in urban planning to instead of medicine against the new 

widespread ill-health called stress. 

Workplace greenery index N Level of Stress 

W-index 1 95 Having no view of a garden and no chan 153.73 

to go out during breaks 

W-index 2 86 Having no view of a garden and a chance 

a break out of doors once a month at mo 

104.08 

W-index 3 276 Having a view of a garden and few 

or no chances of a break out of 

doors (once a week at most) 

W-index 4 117 Having a view of a green garden 

and chances of a break in a green 

garden more than once a week 

Table 4: Level stress and workplace greenery 

94.66 

77.07 

4.3 Storm Water Treated by Water Park 

The storm water is not filtered through the Enköping sewage works, but is running out into the 

Korsängen dyke and the Enköping River and finally finding its way into Lake Mälaren untreated. 

Due to the increased effluence of nitrogen and phosphorous in the Baltic Sea and Lake Mälaren since 

70s, the Enköping local council launched the project “Lake Mälaren Water” in 1995. The goal of this 

project is to reduce the pollution discharge to Mälaren River, especially to control nitrogen, 

phosphorous contents, thereby improving quality of daily water provided to Enköping residences. 

Figure 20: The Water Park in Enköping 

Source: Vatten & renhållning, 2004 

33

The first drafts to the storm water treatment facility were produced in 1998. “The water park” as is the 

designed concept was introduced shown in Figure 20. The goals of the water park are not only for 

treatment of different pollutants, but also for creation of an aesthetically pleasant environment and 

inspiring recreation area for the local community. At the same time, it supports biodiversity. 

The Water Park development is on municipally owned arable land and consists of a shallow watercourse 


with a system of dams, meandering through the landscape. Its work principles are based on storm water 

treatment by wetland. The water park flow process is shown in Figure 21. 

The storm water accumulated from 1700 hectare outflow area such as from streets, roads and fields 

converge into the Korsängen Dyke (Inlet No.1 shown as in Figure 21) and is then filtered through the 

Water Park, where bacteria living on the water plants transform nitrogen into harmless nitrogen gas. 

The sedimentation process of particle retained phosphorous eventuates. The water dwell time varies 

depending on the weather situation but the estimated averaged dwell time is between 5 and 10 days. 

The total water area comes to 90 000m 2 and the calculated absorption of nitrogen is 3 to 5 tons and 

nearly 1 ton of phosphorous per year (Vatten & Renhållning, 2004). It means the contents of nitrogen 

and phosphorous after filtered through the water park can be approximately reduced 64% and 56% 

respectively. Another environment achievement that is the water park also substantially reduces heavy 

metals between 53% and 86%. BOD, COD could be reduced 11% and 20% respectively. 

Figure 21: Water Park Flow Chat 


In the water park, the important factors that control the treatment processes are the water’s contents, 

composition of various materials, light, temperature, pH and flow conditions. Sedimentation as the 

34

purification process is of crucial importance for the treatment of many polluters in Stormwater. Long 

renewal time and thereby low flow velocity is particularly desirable. The weir (No.2 shown as in Figure 

21) as to be the flow rate manager to regulates the water flow to the water park. 

The Purification Process: Prior to the water reaching the water cause it will filter through an over-flow 

surface (No.3 shown as Figure 21) and a filtering bed (No.7 shown as Figure 21), whose main functions 


are the removal of particles and reduce the level of nitrogen, phosphorous and other heavy metals at this 

stage. This is where the main purification process is accomplished. On the over-flow surface, it 

functions as a reservoir when there are excessive flows of water, the water is pumped into the filtering 

bed by pumping station (No.6 shown as Figure 21) through the intake pipe (No. 5 shown as Figure 21). 

Normally, a regulated amount of water (ca. 59-100 l/s) is being pumped out to the sprinklers on the 

filtering bed. On the filtering bed, the thin layer of water is slowly filtering through the grass-covered 

ground thus supply the water with oxygen and eliminate odorous smells. When the water has passed 

through these sections, most of the polluters will have been sifted away. The water is relatively clean 

and clear when it reaches to the accumulation dyke (No.8 shown as Figure 21). No.4 shown as in Figure 

21 is snow tip. It is used for cleaning the melted snow after heavy snowing in the wintertime. 

Denitrification Process: in the water park, denitrification as the main and final process to remove 

nitrogen. Natures own resourcefulness is the main driving force in this bioprocess, and by diving the 

watercourse with three different depths shown as Figure 22. The deepest part of the section (No.9 

shown as Figure 21) is 1.5 m deep and this is where the most essential part of the process takes place, 

the denitrification process, and the reduction of nitrogen effluence. Denitrification demands oxygen free 

(anaerobic) conditions and rich access to carbon. The signification being those bacteria in oxygen 

deficient water, converts nitrogen nutrients into nitrogen gas. The conversion reaction is shown as 

below: 

− 

− 

24NO3 

+ 5C6 

H12O6 

→ 12N 

2 

+ 30CO2 

+ H 

2O 

+ 24OH 

In the denitrification process, pH is controlled between 7 and 8. The temperature is below 5 o C 

1 . In 

these deeper sections of water, substance making the water cloudy will also together with heavy metals 

sink to the bottom. The accumulation of sediment on the bottom of the water will probably have to be 

scraped off every eight years and then disposal with special landfill that the landfill bed bottom is 

sealed in order to pollute the groundwater. The next water level has an average depth of 0.7 m and it is 

at this section of the dam where the water is oxygenated utilizing the undergrowth. The low water 

threshold is only 20 cm deep, but provides a very important function. Through this passage the water 

runs very slowly, filtering through the densely growing vegetation. A variety of border plants, a variety 

of sedges, herbaceous plants and flowers, grow alongside the water bank. 

Figure 22: Denitrification Process 


The role of vegetation in the treatment processes is to a large extent based on their physical presence. 

For instance increases the possibilities for an even distribution of water flow and reduction of water 

velocity. Vegetation also plays an essential role for the nitrogen reducing process by immobilizing 

oxygen and carbon. It is important to choose such species that form sparse and continuous plant covers 

1 Interviews with Enköpings Kommun Consultant Department 

35

and has thin and streamlined shoots. This gives appropriate resistance to the water flow. The plants are 

harvested 10 times every year. Some of them are disposal with composting, others by landfill. 

Finally, the purified water runs into the Korsängen dyke, this time either to be transported out into the 

Enköping River or to go through the water park process once again. (No.12 is shown as Figure. 21) 

Financing: the cost of the water park is 4.2 million SEK and has to a great extent been financed by the 

local council but the County Council has contributed with an investment grant of 600 000 SEK. The 


municipal water and wastewater works is in charge of the maintenance and operation of the water park, 

but will also require services from the Parks and sports office. The yearly maintenance cost is estimated 

to a total sum of 100 000 SEK (Vatten & Renhållning, 2004). 

Social aspects: since the water park is situated near the town centre and in the close vicinity of schools 

houses and sports fields it is self-evident that creating a natural and inviting park environment fulfils 

just as an important function as the bioprocess itself. Anyone visiting the water park will experience 

visual effects of inspirational value when walking along pathways through meadows, over bridges 

taking pleasure in the diverse scenery of open mirrors of water, read passages and lush foliage. 

Ecological aspects: regarding goals on biodiversity it is particularly important to understand the 

disruption of the water park’s plant societies. These disruptions are the water fluctuations and 

cultivation as grazing and mowing. The disruption prevents the water park from getting overgrown and 

therefore maintains light and warm life conditions. This gives high food productivity in form of seeds 

and insects, which in turn attracts a great variety of animal groups. The water park vegetation also 

offers shelter. An important principle is to favour a vegetation structure where it is close to both food 

and shelter. Since the water park was constructed, 180 new species birds have been found near around 1 . 

The Enköping Municipality is planning to build up one of the bird tower near the water park in the 

future. 

4.4 Energy Supply by Energy Forest 

Aquatic Birds in Water Park 

Photo by Chen Jie 

Green areas can be used for energy production. In 1994 a Combined Heat and Power Plant was 

commissioned on bio-energy. Today, they use between 15-20% of their yearly consumption from Salix 

that is grown in the neighbourhood due to the fact that Salix does not give any problem in the fuel 

handling. The Salix plantations at Nynäs Manor Farm have an annual average yield of 5 GWh, which is 

the equivalent of two percent of total requirements of biofuels. 

Throughout the summer period, the 189-acre energy forest at Nynäs Manor Farm is being irrigated with 

fertile nitrogenous water from the municipal sewage plant. At the same time the bottom ash and 

digested sludge from the wastewater treatment plant is used as a fertilizer for the cultivation of Salix, so 

it is called energy forest. The energy forest is utilizing the nutrients in the sludge water for it growth. In 

other words, this energy forest not only may produce energy, but can also reduce nitrogen, phosphorous 

1 Interviews with Enköpings Kommun Consultant Department 

36

and heavy metals. In all, the plant manages 30 tones of nitrogen and 1 ton of phosphorous per year. 

After about two to three years the energy forest is harvested and the chips are burnt in the municipal 

heating plant, ENA Kraft, generating heat and electricity. 

The energy forest plantations at Nynäs Manor Farm are divided into six different units (Figure 23), each 

unit watered for a full three hours every day in the summer period. The units vary in size from 25 to 37- 

acres. Salix needs a generous supply of water during its period of growth, which means that the energy 

plantation is irrigated 90 days a year. A total amount of 200 000m 3 of water of which 20 000m 3 rejected 


from the centrifuges and decant water come from the basin (two big tanks beside the centrifuges) and 

180 000m 3 of outgoing cleaned waste water from the treatment plant (Figure 24) will be dispersed each 

year. This is the equivalent of 3 mm rainfall every 24 hours. Reject and decant must stay in one of the 

smaller dams (5 000m 3 ) at least two months for hygenizing and after that the hygenized mix will be 

pumped over to the big dam (20 000m 3 ) and lay there until it is time to irrigate the Salix. Then, during 

the three months of summer, it mixes with outgoing cleaned wastewater (2 000m 3 /day) from the last 

sedimentation in the wastewater treatment plant and applied through the pipes directly to the Salix 

roots. Salix use all of the water for growing process, which includes evaporating. The pH value of the 

water is controlled between 7.7 and 7.8; temperature has never got under 8 o C 

1 . This means the water 

has no negative effects for Salix irrigation and does not pollute this irrigation field’s ground water. The 

dams have enough space to reserve the entire reject and decant from wastewater treatment plant 

produced during one year. The irrigation hoses are placed in every second row of Salix, i.e. a distance 

of 2,25m between each hose. The irrigation holes are spaced 80cm apart. 

From studies of the Energy Forest in Enköping, we can see that this is a successful performance in 

multiuse and waste cycling; it is using sewage sludge as a fertilizer for its willow plantations. This is 

cheaper than usual nitrogen remove process. Meanwhile, they use the willow plantations as one of the 

burning materials in the bio-energy in their power and heat plant to generate electricity and heat for 

the local energy support. 

1 Interviews with Enköping Kommun Vattern & rehållning Laboratorieingenjör 

37

Figure 24: Flow chart of wastewater treatment 

Source: Vatten & renhållning, Enköpings Kommun 


A 

B 

A: Big Dam (20 000m3) B: Salix Plants 

38

Figure 23: Irrigation plant in Enköping energy forest 

5. Conclusions 


The search for sustainability of urban environment means a research for both higher and new qualities 

of townscape as well. It covers three dimensions: environmental, social and economical sustainability. 

Environmental benefits 

The green structure that earlier were valued for their aesthetic and social dimensions, have today 

become more important for ecological value and the sustainability for the town of city. Green structures 

improve substantially the climatic conditions of city and provide the city with biological diversity and 

become habitats for flora and fauna as we could observe from our case. A good landscape may attract 

animal species such as songbirds and small game, which add to the richness of residential areas. Green 

space, varying from forest stands to wetland complexes to a single tree support the needs of resident or 

migratory animal populations. In urbanized areas, community and regional parks can serve as habitat 

patches as can an inner-city yard landscape with native plants. 

Social benefits 

Greenery provides enjoyment with the landscape and enhances social contacts and outdoors activities. 

Visual and physical contact with plants can result in direct health benefit; plants can generate 

restorative effects leading to decreased stress, improve patient recovery rates and provide higher 

resistance to illness. As we can see from our case study, greenery can provide enjoyment with the 

landscape defining the space and providing urban residents the setting for outdoor recreational pursuits, 

especially the elderly, and the young who are more dependent on near home recreation spaces. 

Greenery may help to solve some of current social problems such as isolation of intergeneration. An 

increase in contact between generations would lead to enriching opportunities to share knowledge, 

skills and affection. Public outdoor settings could provide interactive opportunities. The pleasant urban 

soundscape is important for city dwellers, similarly to the sound of wind rustling through leaves, which 

has been used in hospital wards to mask disturbing sounds and help heart attack victims to relax. The 

fragrance of flowers and plants can trigger responses that are more cognitive and tend to be 

remembered more vividly than the visual stimuli. Towns should be built in a way so that people in the 

city feel safe, comfortable and happy. Landscaping has often been used to improve the aesthetics of the 

urban environment. Vegetation can provide visual contrast and relief from the highly built-up city 

environment. Visual appeal from an escalated view is an equally important benefit, especially in urban 

areas with many tall surrounding buildings. 

Economical benefits 

Green structure works in the sustainable economic aspects by providing low energy consumption, low 

investment and operation costs such as “Water Park”. Recreational opportunities, scenic beauty and 

wildlife that make Enköping an attractive place to live, work and do business. The population has 

grown from 36 109 to 38 005 since 1993 to 2003 (SCB, 2004). Liveable community might be able to 

encourage and promote business activities such as local tourism business. It may promote local job 

opportunities and local income, thereby to run the local economy. However, values attached to green 

structures, like those derived from pleasant landscape, clear air, peace and quiet and screening as well 

as potential recreational activities in wooded green spaces, reduced speed wind velocity, balanced 

microclimate, and shading and erosion control are non-priced environmental benefits. At the same time 

we have to face a risk that is unclear: which environmental factors make a location pleasant to live in 

and of high quality, and how much people are willing to pay for providing these amenities. 

39

My thesis has shown how important the links are between all green areas in the city. First of all 

undisturbed green connection including water is significant for transfer of plant material, which 

supports wildlife. It can be maintained in form of green corridors, which can consist of all forms, 

mentioned in classification of green structures. Green roofs might appear efficient for nesting, open 

water bodies for fish, home gardens and allotments for animals and plants. Secondly the undisturbed 

green connection equipped in pedestrian, bicycle routes is valuable for health of city dwellers, because 

of their restorative qualities. Besides that it can help to create a preferred, more psychologically 

acceptable urban environment at a whole city scale. Importance of greenery along streets, in squares 

5. Conclusions 

and all other urban interiors should be obvious not only because of aesthetical reasons. Creation of 

well-connected urban green structure adds valuable new qualities to an urban environment. 

Urban planners, while proposing development of new built up areas, should cooperate with 

environmentalists and landscape planners to analyze greenery linkage qualities of existing habitats to 

preserve wildlife migration pathway and human health and comfort. 

Maki addresses linkage as the most important characteristic of the urban exterior space, stating that: 

“Linkage is simply the glue of the city. It is the act by which we unite all the layers of activity and 

resulting physical form in the city…urban design is concerned with the question of making 

comprehensible links between discrete things. As a corollary, it is concerned with making an 

extremely large entity comprehensible by articulating its parts”(Fumihiko, 1964). 

40

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42

Interview 

person 

number 

Time 

Age, Sex, 

Profession 

Do you 

Live 

near this 

park? 

What do you 

usually do 

here? 

Do you like this park 

? Feel Safe? 

Which park is your 

favourest one? 

How much time 

will you stay in 

this park? Visit 

frequency? 

Do you like this 

park as it is or 

would you like to 

improve this park? 

1 12:00 55,M ,Retired Y 

2 12:30 

36,M ,Computer 

operator 

3 13:00 57,F,Grandmoter; 

5,M,Grandson 

4 15:30 

35-37,F&3M , 

Unemployeed 

N 

Take the rest 

& walk around 

with my dogs 

Walking 

Through for 

working break 

Y,Y,Dream park 2-3h,twice/day Y 

Y,Y,Dream park 

Y Walking aound Y,Y,Dream park 

N Meet friends Y,Y,Dream park 

Few minitues, 

once or 

twice/week 

1-2h , 

Many times/week 

2h, once or 

twice/month 

N, 

pathwayconstruction 

material 

would like to 

change from 

asphalt to soft one 

Y 

Y 

APPENDIX 

Interviews Questionnairs in Kloster Park, Enköping 

Interviews with Key Person in Enköping Kommuns 

Danielle Littlewood: Head of Concultant Department 

Marie Lewen-Carlsson: Laboratory Engineer of Water and Street Cleaning Department 

Stefan Mattson: Head of Parks Department 

Mats Jonsson: Employee of Street Department 

Wendelin Muller-Wille: Chairman of the Education Committee 

Vice Chairman of the City Council 

Y=Yes, N=No 

43

GLOSSARY 

N: Nitrogen 

P: Phosphorus 

NO 2: Nitrogen Dioxide 

NO x: Nitrogen Oxides 

CO 2: Carbon Dioxide 

CO: Carbon Monoxide 

O 3 : Ozone 

SO 2: Sulfur Dioxide 

BOD: Biochemical Oxygen Demand 

COD: Chemical Oxygen Demand 

VOC: Volatile Organic Compound 

TSS: Total Suspended Solids 

FWS: Free Water Surface 

Anoxic Process: The process, which have no free oxygen, but oxygen from NO 3 

Anaerob Process: The process is totally oxygen free process 

Aerobic Process: Oxygen needed process 

44

The role of Green Structures in Development of the Sustainable City

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