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INTERNATIONAL GREEN ROOF INSTITUTE
New Approach to Sustainable
Stormwater Planning
Peter Stahre
Malmo Water, Malmo, Sweden
Govert D. Geldof
TAUW, Deventer, The Netherlands
September 2003
www.greenroof.se
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Publikation No 005

INTERNATIONAL GREEN ROOF INSTITUTE
New Approach to Sustainable
Stormwater Planning
Peter Stahre
Malmo Water, Malmo, Sweden
Govert D. Geldof
TAUW, Deventer, The Netherlands
Financed by:
Interreg IIIB
FORMAS proj nr 2001-0455
September 2003
Publication No 005
Augustenborg´s Botanical Roof Garden
Ystadvägen 56, SE -214 45 Malmö, Sweden
+46 40 94 85 20
e-mail: info@greenroof.se
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www.greenroof.se ISBN 91-973489-4-5

Contents
Abstract .................................................................................................................................................. 6
1. Introduction ............................................................................................................................... 7
2. Two planning approaches ........................................................................................... 8
3. Characteristic features of the new integrated approach ................... 9
3.1 System complexity ................................................................................................................ 9
3.2 The role of time in the planning ........................................................................................ 9
3.3 Many opportunities lie in the unknown .......................................................................11
3.4 Diversity and dynamics .......................................................................................................12
3.5 Integrated planning .............................................................................................................12
4. Sustainable stormwater drainage .........................................................................13
5. Planning of sustainable stormwater drainage in practice ...............15
5.1Traditional planning ..............................................................................................................15
5.2 Integrated planning .............................................................................................................16
5.3 Interactive Implementation ..............................................................................................18
6. Sustainable storm drainage - examples from Malmö, Sweden 20
6.1 Green roofs in Augustenborg ..........................................................................................20
6.2 Open drainage in a park in Augustenborg ................................................................21
6.3 Detention of stormwater runoff from the schoolyard in Augustenborg. ........22
6.4 Stormwater detention in the Toftanäs wetland park ...............................................22
6.5 Stormwater detention in the Husie lake ......................................................................23
7. Conclusion .................................................................................................................................24
Acknowledgements ..........................................................................................................................24
Bibliography .........................................................................................................................................25
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Abstract
Traditional models for planning urban water systems are to great extent based on technical
and economic considerations (Model A). This approach is adequate for planning
isolated and well-defined water systems. With the introduction of the concept of sustainability,
the water systems interact with societal processes in the urban environment. We
are then not any more dealing with an isolated water system but with a complex adaptive
system. For such systems the traditional planning models are not good enough. A more
integrated planning approach is needed (Model B).
In complex adaptive systems, time plays a very important role in the planning. Among
the conditions that must be taken into account can be mentioned:
• The complexity of the system
• The past (history)
• The present and the future
• The timing
• The uncertainties of the system
Speeding up a complex process often results in unforeseen rebound effects (“More haste,
less speed”).
Different techniques for sustainable stormwater drainage are described. Based on experiences
in the city of Malmö in Sweden a practical approach for integrated planning
of these types of drainage systems has evolved (Model B). The new approach is called
Interactive Implementation. As a result multiple use of stormwater facilities has today
become general practice in Malmö. The outcome of some sustainable stormwater projects
is presented.
Peter Stahre: Malmö Water, S – 205 80 Malmö, Sweden
e-mail: peter.stahre@malmo.se
Govert D. Geldof: Tauw, PO Box 133, 7400 AC Deventer, The Netherlands;
e-mail: gdg@tauw.nl

1. Introduction
The Rio declaration and the Agenda 21 from the early 1990’s introduced the concept
of long-term sustainability of our environment. One important ingredient in the new
approach is that technical, economic and social aspects of the development are handled
integrated. There is today a consensus that urban water systems should be approached
in an integrated way. Surface water, groundwater, water quality, water quantity and ecology
should be looked upon in relation to each other. We also know that integrated approaches
can give inspiration to new solutions to water problems. Thus, the introduction
of the concept of sustainability has in the field of urban water systems among others led
to an increased interest for source control and open drainage of stormwater within the
urban environment.
Although an integrated approach sounds good, there are many obstacles under way. In
recent years many integrated urban water plans have been drawn up. Interdisciplinary
teams develop plans, formulate optimum packages of measures and create beautiful reports
with nice pictures. The local politicians often enthusiastically receive these plans.
However, many of the suggested measures are never implemented. As some people say:
“Integrated urban water plans die from their own beauty.”
Urban water managers have become aware that it is not sufficient to restrict an integrated
approach to surface water, groundwater, water quality, water quantity and ecology. They
also require measures that are attuned to spatial planning, traffic, maintenance and management
of public areas, urban renewal, etc. A town displays a great deal of dynamics,
in which a large variety of professionals intervene. Traffic engineers adapt roads and
streets, architects make new designs for buildings in the city centre, green belts are changed,
programs are initiated to improve social safety, and town planners implement urban
renewal plans where significant parts of the town are redesigned. It is essential that water
management fit into these dynamics. However, that is not always the case today.
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2. Two planning approaches
Traditional planning models for urban water systems are to great extent based on technical
and economic considerations. In these urban water systems are mostly regarded as
controlled systems that have to be optimised: we measure, define objectives, compare
measurements and objectives, remove bottlenecks and apply techniques to improve the
water system. Finally, the system will attain the objectives.
The traditional planning approach is adequate for isolated and well-defined systems,
such as under-ground pipe networks and end of pipe treatment facilities. However, for
water systems, where there is an interaction between water and society, the traditional
planning approach is not sufficient. To be able to handle the social dimensions in
an appropriate way we must find alternatives to the traditional planning models. This
means that integrated systems must be approached as complex adaptive systems with
positive and negative feedback loops.
In the following the traditional planning approach (“Model A”) and the new integrated
approach (“Model B”) will be discussed in more detail.
Water manager
Water system
The whole as a complex
adaptive system
Society
Water system
Model A Model B
Figure 1. Schematic illustration of the traditional (Model A) and integrated
(Model B) planning approaches.
In figure 1, Model A represents the traditional way of thinking. It assumes that the water
manager controls the water system, so it will function properly. When the water manager
detects deficiencies, he or she will compose an optimum package of corrective measures.
The planning process in this model can be described in consecutive steps, which are passed
through cyclically.
Model B represents a new way of thinking. The water system is regarded as an integrated
part of the city, which display a lot of dynamics. The model focuses on the interactions
between the water system and society. These interactions are complex by nature, because
many actors are involved in the process, a large variety of structures exist and different
scale levels, and many policy fields are covered, like traffic, spatial planning and housing.
It is also a meeting between technical and social sciences. The whole of processes is assumed
to be a complex adaptive system. The system has the ability to adapt its structure
when environment changes.

3. Characteristic features of the new integrated
approach
In the previous section two planning approaches were introduced: Model A, representing
the traditional approach to planning of urban water system and Model B, representing
the new integrated approach. At first sight there seem to be only minor differences between
the two planning approaches. However in practice the differences are huge. Some
of these differences will here be explained in more detail.
3.1 System complexity
Urban water systems, which interact with societal processes, are complex adaptive systems.
The complexity that characterises such systems should not be disputed but be
made manageable. Complexity must not be looked upon as something nasty that has
to be reduced or avoided, but as a precondition for innovation and transition. When a
complex adaptive system is tamed and totally controlled, it loses its ability to adapt and
to innovate.
Disputing complexity (as in Model A) means in practice that the integrated systems are
reduced to such an extent that they show predictable behaviour that can be controlled.
This means that only part of the system is in focus, i.e. the part that shows linear behaviour
and which falls under negative feedback loops.
Managing complexity (as in Model B) means that we try to understand the value of
the interwoven processes. The whole system then comes into view. This is when we discover
that the system is not static but undergoes constant changes. In that, time plays
an important role. With model B we illuminate subsystems with negative and positive
feedback loops. Due to the positive feedback loops, processes accelerate and may show
chaos, part of the time.
Complex adaptive systems exhibit patterns on which we can reflect during planning. In
that, we have to strengthen the bond between science and practice. Science offers new
insights and tools for practice, and practice offers experience for science.
3.2 The role of time in the planning
In complex adaptive systems time plays an important role. Looking at planning processes
in integrated urban water management, where insights and techniques have evolved
dramatically in the last decades, we see that there has not really been a dignified place for
time. Model A still dominates. In the following the importance of time will be discussed.
The past
In systems with positive feedback the past does not fade away. A lot of values attached to
water systems, especially surface water, have their roots in history. In plans we make with
Model A, the history of an area is not taken into account. We recognise the present and
the future, where the future should present a better state than the present. So – measures
are planned. History does normally not influence the process of selecting appropriate
measures.
Politicians tend to include history in their decision-making processes, but planners and
policy makers do not. This is remarkable, because in many processes of transition most
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counter-arguments are drawn from history: “Things were promised but never materialised”
and “It’s been tried before, but wasn’t really successful”. Even more important is
the fact that in the past, events have taken place that gave historical or cultural meaning
to objects in the area. People attach stories to places. These stories have value. If these
stories are not taken into account, residents involved in the planning process feel that the
professionals are not taking them seriously.
History is of importance especially in water management, because in every country the
water systems represent cultural values. In Model B the history is taken into account
and the connection between water and culture is examined. Experience show that when
source control or open drainage of stormwater is applied, people in residential areas often
will respond enthusiastically, particularly if the cultural values are increased.
The present and the future
In traditional planning, the difference between the present and the future in many cases
is artificial. Goals are formulated for the future (e.g. “By 2005, emissions from the sewer
system have to be reduced by 50%”). Later, when these goals have been reached, the state
of the system will have improved. For that to happen, however, the goals have to be both
rigid and verifiable. Today we often apply standards as goals.
How do we cope with the goals and standards in Model A? We compare the present state
of a system with its desired future state. By doing that, we beat down time and confront
ourselves with a pile of bottlenecks – problems – in the present. Time has disappeared.
To reduce these bottlenecks we identify measures. After that, we use complex planning
strategies to prioritise the measures and reintroduce the eliminated time. The result is a
measuring rod of time, with measures neatly organized alongside. This time structure is
the result of a bargaining process, in which ambition and costs are important variables.
Glasbergen and Driessen (1993) analysed several integrated planning processes in the
Netherlands. They concluded that: “Defining rigid project goals beforehand… will discourage
actors from participating in the process.” They observed that in successful planning
processes goals are formulated during the process and sometimes even afterwards.
The goals emerge from the process.
The perception of time
Time is a rich concept. At the level of integrated water management plans, time manifests
itself in a creative manner, i.e. as the carrier of change. Sometimes we can predict
change, but often we cannot. Time produces surprises and if we do not like them we
experience time as an obstacle and an enemy. It is an obstacle when it separates us from
goals in the future and an enemy when it reveals our inability to control environmental
problems. By means of advanced models we create the impression that complex processes
can be predicted and controlled. When it does not work out the way we expect, we feel
guilty or we blame someone else. A cyclic pattern of problem, solution, control, failure
and guilt develops.
In the most extreme cases people try to escape the ravages of time. People who do not
have time, who do not reflect on the present and the past, and who try to exclude future
surprises, are afraid of getting old. They have no stories. They had better form an alliance
with time (Model B) and try to appreciate the beauty of the uncontrollable. By trying to
understand the uncontrollable, we can discover new patterns that can help us to navigate

through a complex world. People who take their time do not experience it as an obstacle.
However, time as an obstacle increases when activist groups force the local government
to reduce time intervals. (e.g. “The goals must be met in 2005 instead of 2008!”)
Good timing
Not all moments are suitable for implementing ideas to improve urban water systems.
This is especially true in the planning of open water systems in the urban environment.
It is an art to give planning processes the time they need. Visions about water systems
and society must not be translated into rigid goals too quickly. Pressing the turbo button
in order to achieve the goals must be avoided. Speeding up the planning processes often
results in delay (“More haste, less speed”). Mumford (1947) distinguishes two types of
time: the chronological time and the kairo-logical time (Kairos = the right moment).
The former offers a structure for events and measures, whereas the latter emerges from
knowledge, intuition and experience and consists of “the right moments”. Intervening in
processes requires good timing. To have a feel for the right moment is important, because
sometimes it is better not to act. Although this increases the complexity of interventions,
it also makes them more realistic and effective. Good politicians act in kairological
time.
3.3 Many opportunities lie in the unknown
When we in the planning explore the relationships between goals and measures and
between cause and effect, we meet uncertainty. Sometimes it is possible to predict the
effects of different interventions in the system. However, there are a lot of cases where
the outcome could be a surprise. We can distinguish three degrees of uncertainty in cause
and effect relationships: certain, uncertain and structurally uncertain.
Some processes are easy to predict. For example, when we double the pump-capacity in
a pond system, it is easy to predict the effects on surface water level management. There
are no real uncertainties. However, when we increase the storage capacity within a sewer
system, it is difficult to predict the effects on the pollution load on the surface water. We
know that the larger the storage, the smaller the pollution load. But, predictions of the
effects are often inaccurate – there are uncertainties. Doing more research and applying
better models can reduce these uncertainties.
We talk about structural uncertainty (Walker, 2000) when it is impossible to reduce the
uncertainty. For example, it is very hard to predict how people will react to an integrated
water plan, as it is difficult to model public and political support. On the top of that,
societal systems often show a deterministic chaos. As result it is impossible to predict
long-term future behaviour, even if we have a perfect model.
A strategy often attached to the model of reducing complexity (Model A) is to avoid chaos
and structural uncertainty. Interventions are focused on cause and effect relationships
that can be described very well and exhibit little uncertainty. In practice this means that
only processes in the biophysical water system are taken into account and the interaction
between water and society are taken for granted. Society is in equilibrium. This strategy
of avoiding uncertainty gives rise to concern, because the change will be incremental.
To really change system behaviour, the area of structural uncertainty offers the best prospects.
The reason is that the associated processes have the highest degree of freedom.
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Many opportunities lie in the unknown. The future may reveal change that coincides
with a shared vision on sustainable water management. For that, a strategy that fits Model
B shows a healthy uncertainty balance. The interactions between water system and
society are taken into account and interventions are carried out in both water system and
society. To cope with the structural uncertainty, the strategy includes learning by doing.
Over the course of time, we learn.
3.4 Diversity and dynamics
A lot of policy papers talk about diversity. We should aim for bio-diversity and diversity
in architecture and in the design of public space. Even urbanized areas offer good opportunities
for “nature”, and by increasing spatial diversity we increase the identity of a
residential or industrial area. Also source control measures and open stormwater drainage
systems show a lot of diversity when techniques are adapted to the local circumstances.
In short, diversity is important.
For ecosystems, van Leeuwen (1966) discovered that diversity and dynamics are interrelated:
the higher the dynamics – the lower the diversity. This relationship between
diversity and dynamics gives reason to question the call for dynamics in urban planning.
This relationship might be applicable to societal processes. Where dynamics increase,
diversity might decrease. A good example concerns the construction of large areas of new
housing. In a short period of time many houses are designed and built. The diversity of
these new areas is nothing compared to the diversity of an old town centre that has been
developed over hundreds of years.
When diversity and dynamics are really related to each other in the way described here,
this is an argument to include time in planning processes more explicitly. Slowing down
a process might increase diversity.
3.5 Integrated planning
Many scientists still entertain the idea that they develop new knowledge, which is then
translated into tools to be used by water managers. By using these tools, water management
will improve. For a lot of management questions, this way of thinking (which is
connected to Model A) is sufficient. However, it is inadequate for integrated management.
Integrated management requires a new kind of science (Model B).
Over the course of time, the characteristics of integrated water management problems
will change, and the tools offered by scientists have to be capable of adapting to the new
situation. The dynamics of the interaction between water system and society has to be
taken into account. For that, it is impossible for scientists to observe processes from a
distance, collect data, construct a tool and offer this tool to people in practice. To include
time in science, there has to be an intensive interaction between science and practice.
Only then will integration become effective.
Integrated water management issues are complex. In planning processes, this complexity
should not be resisted but made manageable. It is obvious that:
• Time plays an important role in planning processes.
• To obtain public and political support for a plan, it is necessary to include history,
timing and uncertainty in the planning process.
• Real integration is only possible when science and practice interact intensively. Science
from a distance is not sufficient.

4. Sustainable stormwater drainage
The drainage of stormwater from urban areas has traditionally been accom-plished by
constructing storm sewers, through which stormwater is conveyed directly into adjacent
surface waters. In recent years there has been an increased concern about the impact of
the stormwater runoff on the quality of our surface waters. The solutions that came up
were based on the idea of slowing down the runoff by source control measures and by
open stormwater drainage systems. These measures have among others been referred to as
sustainable stormwater drainage. As illustrated in figure 2 these types of drainage facility
can be categorized in four groups.
Source
control
Onsite
control
Private land Public land
Slow
transport Downstream
control
Figure 2. Categorization of facilities for sustainable stormwater drainage
Table 1 shows some examples of the technical configuration of facilities within the four
categories. It must be emphasized here that the detailed technical configuration of the
facilities to great extent must be adapted to the prevailing local conditions and to its
intended role in the urban environment.
Table 1. Examples of technical configuration of sustainable stormwater facilities.
Category Example of technical design
Source control (private land) Green roofs
Infiltration on lawns
Infiltration in stone fillings (percolation)
Collection of rainwater in tanks for re-use
Onsite control (public land) Permeable pavements
Small dry pond
Small wet ponds/wetlands
Infiltration in stone fillings
Infiltration in swales
Slow transport (public land) Overland flow in swales
Constructed concrete canals
Creeks
Downstream control (public land) Wetlands
Ponds
Lakes
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The know-how of the technical design and dimensioning of sustainable stormwater facilities
is today well established. Extensive documentation of design practices is available
in various guidelines and handbooks. The new element in the design is the integrated
approach where hydraulic design criteria are combined with ecological, biological, aesthetic
considerations.
The prevailing natural conditions at the site of the planned facility must be taken as
a base for the design. Examples of natural conditions are topography, hydrology (watercourses,
wet lands, surface waters), soil condition (permeability, groundwater level),
vegetation etc. To optimise the stormwater management one should try to combine technical
solutions from the different categories of stormwater facilities. Thus infiltration
and percolation of stormwater on individual lots should be combined with measures
on publicly controlled land. The goal must be to use all parts of the urban stormwater
“runoff-train”.
The multiple use of a stormwater facility plays an important role in the design. The special
objectives and goals that have been set up for the facility must be considered in the
design process. The challenge in the design of sustainable stormwater facilities is that the
design criteria for quantity and quality control of stormwater sometimes are contradictory
to the design criteria for other purposes such as aesthetics, recreation, public access,
education etc.

5. Planning of sustainable stormwater drainage
in practice
5.1 Traditional planning
Storm drainage is the responsibility of the city’s Drainage department. As traditional
stormwater facilities (pipes and detention tanks), are located underground the planning,
design and the construction is normally carried out without involvement of any other
technical department in the city (Model A). Figure 3 schematically illustrates the traditional
planning of measures to upgrade an existing urban storm-water system.
Drainage department
Determine goals
Monitor the system
Compare observations
with goals
Identify and optimise
measures
Implement measures
Evaluate results
Figure 3. Illustration of traditional planning of stormwater facilities (Model A)
As a base for the planning a goal is set up for what runoff standards that are to be fulfilled.
With the help of advanced hydraulic modelling tools alternative measures to improve the
system are identified. A cost benefit analysis is carried out to select the optimal set of improvement
measures. When the measures have been implemented the result is evaluated
by monitoring the system. The typical feature of the planning is that it in practice is fully
controlled by the Drainage department (Model A).
Model A is still the prevailing approach for planning measures in urban stormwater systems.
This is all right as long as the measures are limited to the construction of facilities,
which do not directly intervene with the urban environment. However, the introduction
of sustainable stormwater drainage has changed the pre-requisites for the planning. Because
the measures are integrated in the urban environment in quite another way than
traditional underground stormwater facilities, Model A is not adequate any longer.
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The planning cannot be carried out by the Drainage department alone, but must be
carried out in co-operation with other city departments and with involvement of the
citizens.
5.2 Integrated planning
To succeed with the implementation of the concept of sustainable urban storm drainage
it is of utmost importance to consider the societal aspects that are associated with an integration
of the stormwater facilities in the urban environment. Examples of these aspects
are given in figure 4.
Economic
value
Recreational
value
Cultural
value
Technical
value
Historic
value
Aestethic
value
Input to
the integrated
planning
PR
value
Biologic
value
Ecological
value
Environmental
value
Pedagogic
value
Figure 4. Examples of values that should be considered in the planning of
sustainable stormwater drainage systems
The introduction of sustainable stormwater drainage leads to that the planning becomes
much more complex (Model B) compared to planning of traditional stormwater facilities
(Model A). An active involvement is needed of several departments in the city. This
involvement is seldom problemfree. Most cities do not have the tradition to co-operate
in the planning and the implementation of jointly owned and operated water facilities.
The institutional barriers for such initiatives are often unexpectedly high. In the city of
Malmö in Sweden it took many years to overcome these barriers.
During 10 years experiences of sustainable stormwater drainage in the city of Malmö a
new planning approach for this type of facility has evolved. In figure 5 this approach is
outlined for a typical example of integrated planning (Model B).

Dep of street & traffic
Dep of recreation
Dep of City environment
General program for
city environment
Park and environmental
policy and objectives
Dep of real estate
Organisations
Media
Common vision
Physical planning
Illustration
Additional partners
Public participation
Public relation
Detailed design and
dimensioning
Financing
Realisation
Drainage department
General Drainage plans
Drainage policy and
objectives
City planning dep
Private developers
The citizens
Schools
Figure 5. Schematic illustration of integrated planning of sustainable stormwater
drainage systems in the city of Malmö, Sweden (Model B)
When sustainable stormwater management is applied in Malmö at least three departments
in the city administration typically take active part in the planning process. One
important element in the planning is the involvement of citizens, schools, and pressure
groups, which can have an interest in the planned facilities.
Experiences show that the Drainage and the City Environment departments often take
the leading role in the implementation of the concept of sustainable stormwater drainage.
The Drainage department of course primarily sees sustainable storm drainage as a
mean of achieving their storm drainage goals. By applying the sustainable approach the
goals can sometimes even be fulfilled to a lower cost compared to the construction of a
traditional pipe system. The department of City Environment on the other hand, sees
sustainable stormwater drainage as a way of improving the city environment and of adding
new values to existing or new city parks. If the goals of the two departments can be
combined they can join forces and form a common vision. In this vision the possibilities
of multiple use of the facilities are outlined.
The departments of Drainage and City Environment develop their common vision together
with representatives from the City Planning department. Depending on the nature
of the suggested drainage facilities other city departments are involved in the discussions
of the implementation of the vision. If for example the suggested facilities are to handle
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polluted runoff from roads and other trafficked areas the Street department is involved in
the discussions. If the facilities are to be used for recreational purposes the Department
of Recreation is involved.
At the earliest possible stage the developed vision must be introduced in the city’s physical
planning process. The concept of sustainable stormwater drainage can in practice
often become the driving force for developing the plans. Potential additional partners
are approached in order to broaden the economic base for the implementation. Private
developers and the city’s own real estate department are partners that might see a benefit
in taking part in the project. One incentive for them could be that the prize of the land
might increase if a “blue-green” corridor including open water is introduced in or around
the development.
It is important with public participation in the planning process. The visions should therefore
at the earliest possible stage be introduced to citizens, schools and other pressure
groups in the area. A humble attitude to public demands and requests will facilitate the
public acceptance of the facility. Local media can play an important role in the promotion
of the planned facilities.
The costs for the construction of the facilities associated with sustainable storm drainage
and for their maintenance are shared among the involved parties according to their respective
benefits. The estimation of the benefits of the facility for the departments involved
in the project must always be subject for negotiations between the parties.
Comparing figure 3 and figure 5 it is obvious that planning of sustainable stormwater
facilities is much more complex than planning traditional stormwater facilities. This is
quite natural, as the sustainable storm drainage is an integrated part of the urban environment
and visible for the public.
5.3 Interactive Implementation
The order in which actions take place has changed in Malmö. Time plays a different role.
In former days a serial approach was applied as shown in figure 6. Based on policy papers
a plan was made. This plan presented optimised measures, founded on intensive model
studies. Of course the models could only focus on the stormwater and sewer processes,
not on other processes in the urban areas. When the plan was accepted and the financing
was well organised, the drainage department made the designs and implemented the
constructions. After that, the constructions were handled over to the people who do the
maintaining.
When the focus is restricted to sewer management only, this serial approach (Model A)
suffices. However, for integrated planning it shows many shortcomings. It is impossible
to derive all goals from policy papers to make the ideal plan without uncertainties. Urban
dynamics take place at different time and space scales and it is far too complicated
to connect them all. Also, the arena of people involved in the process of planning and
design differs from the implementation arena significantly. The maintenance people do
not interact with the designers. Reducing the costs of a design often results in higher
maintenance costs. These higher costs are not included in the plan.

Policy Making a plan Design Implementation Maintenance
Policy paper
Plan
Specifications
Figure 6. The serial approach of Model A.
Constructions
The serial approach shows characteristics of a relay race where the stick is handled over
from the one runner to the other, in a strict order of time, as quickly as possible. Especially
the process over handling over the stick is crucial and very critical.
Policy
Vision
Making a plan
Design
Implementation
Maintenance
Figure 7. The parallel approach of Interactive Implementation (Model B).
The practice in Malmö shows a different approach, as shown in figure 7. This approach
is called Interactive Implementation. In interaction with a lot of actors, a vision is developed
for the stormwater management, related to other societal processes in the urban
areas. This vision is not a detailed plan, but an attractive presentation of the stormwater
system in the future, with elements at several time and space scales. This vision is easy to
communicate and makes people enthusiastic, like citizens, politicians and people from
other municipal departments. After that, the plan making process, design, implementation
and maintenance are handled parallel. Where there is the right moment (Kairos),
parts of the vision are brought into construction. For other parts, model studies are
carried out. Maintenance people are involved in designing processes. Creativity now is
not restricted to the design process, but also during construction new insights can be
acquired.
Interactive Implementation shows the characteristics of a learning process, where people
act parallel and learn from each other’s mistakes. Practice and science are interwoven.
Parts of the vision are constructed, even when the financing of the whole vision is not
fully organised. Most of the public and political support emerges out of the process
when practical examples are shown like in Augustenborg (next chapter). Spatial integration
takes place on a large scale (the vision) and integration of water, traffic, recreation,
education and culture takes place in small-scale practical projects. In this, the system
complexity is not disputed, but has been made manageable.
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6. Sustainable storm drainage
- examples from Malmö, Sweden
6.1 Green roofs in Augustenborg
The residential area Augustenborg in Malmö, has a combined sewer system. The area has
suffered from frequent basement flooding. In order to reduce the risk of flooding different
source control techniques have been introduced. The primary goal with these was
to reduce the stormwater runoff to the overloaded combined sewer system.
In the Augustenborg area there is a site with an engineering workshop and a garage. Most
buildings here have flat roofs. To reduce the stormwater runoff from these roofs it was
decided to apply a vegetation cover of sedum grass on top of 9,500 square meters (0,95
hectares) of the roofs. An evaluation of the structural strength of the existing roofs showed
that no extra reinforcement was needed to carry the extra load.
The green roof installation was designed as a full-scale research facility, where the effect of
different grass species, thickness of the soil substrates, the slope of the roof etc could be
investigated. Figure 8 shows one section of the green roof installation in Augustenborg.
Figure 8. A section of the green roof installation at Augustenborg in
Malmö.
The main reason for applying green roofs were their capability to reduce the stormwater
runoff from the roofs. Among the other advantages with this technique can be
mentioned that the green roof serve as an effective insulation of the building and thus
contributes to savings of heating energy. In addition the green roof protects the roof construction.
Calculations show that the lifetime of the roof construction can be prolonged
quite considerably.

6.2 Open drainage in a park in Augustenborg
To reduce the speed of the stormwater runoff, an open drainage system was constructed
through the residential area of Augustenborg. In an existing park the open drainage system
was designed in the form of a shallow drainage ditch (swale). This is only fed with
water during wet-weather conditions. During dry weather conditions the drainage ditch
is totally dried out. One advantage with choosing an open drainage ditch was that the
construction cost was very low and that is easily could be integrated in the park environment.
The new drainage ditch in the park is shown in figure 9.
The idea to form an open drainage ditch originally came from the residents within the
area. Some of them had experienced an old open creek in the park, which was culvertised
when the area was developed several decades ago. No doubt the link to the “historic”
creek through the area was very much appreciated by the residents. In addition the City
Environment department considered that the new open drainage ditch added to the
aesthetic value of the park.
Figure 9. Open drainage ditch in the existing park in Augustenborg
21

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Figure 10. Detention basin in the form of an amphitheatre in the
schoolyard of Augustenborg
6.3 Detention of stormwater runoff from the schoolyard in Augustenborg.
The schoolyard in the residential area of Augustenborg has a very high percentage of
impervious surfaces (roofs and pavements). Almost all runoff from the schoolyard was
connected to the combined sewer system. As part of the upgrading of the sewer system,
the impervious surfaces were remodelled so that most of the runoff was diverted directly
to the new open drainage system in the area.
To slow down the peak flows of runoff, an open detention basin was constructed in the
schoolyard. After discussions with the school authorities it was decided to design the
basin in the form of an open amphitheatre, see figure 10. The ambition was to be able to
use the basin for outdoor lectures.
6.4 Stormwater detention in the Toftanäs wetland park
To be able to manage the stormwater runoff from the new industrial area Toftanäs a
large storage volume was needed. The main reason for that was that the down-stream
pipe system had limited capacity. The City planning, Drainage and City Environment
departments discussed the situation and jointly worked out a vision of a wetland park.
The wetland park was created by excavating an area of about 2 hectares of land to a depth
of about 3 meters (10 feet).
The Toftanäs Wetland Park area is partly designed as a wetland with a shallow marsh
and partly as a traditional dry pond, which is flooded only during wet weather conditions.
The reason for this design was to facilitate public access to the park area during
dry weather conditions. The facility has become an attractive recreational area to which
people come for picnic and for bird watching. Figure 11 shows the inlet area of the wetland
park.

Figure 11. The inlet area in Toftanas wetland park
6.5 Stormwater detention in the Husie lake
To be able to handle stormwater from future settlements in the eastern parts of Malmö
big detention volumes were needed. The closing down of an old military training field
made it possible to create a new lake, the so called Husie Lake. In historic times the area
of the new lake had been a wetland, which however over the last hundred years had been
effectively drained.
The new Husie Lake was created in a natural lowland and was designed with meandering
channels, wetlands, small islands and even one small waterfall. The excavated material
was used for landscaping the area around the lake. The lake has a size of about 4 hectares
(10 acres) with a maximum water depth of 2 meters (6 feet). The lake will receive
stormwater from future settlements in the area as well as drainage water from existing
agriculture-land.
The area around the lake has become an attractive recreational area for citizens in the
whole eastern part of Malmö. Surrounding schools and Kindergartens use the lake for
educational purposes, see figure 12.
Figure 12. A group from a Kindergarten is playing at the outlet of the
Husie Lake
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7. Conclusion
The introduction of the concept of sustainable stormwater drainage has led to that stormwater
not any longer can be looked upon as just a technical service that is supplied by
the city’s Drainage department. Stormwater has become a positive resource in the urban
environment for the citizens. This has led to that many of the city’s departments must
take more active part in the planning.
A close co-operation between the different technical depart-ments in the city and an
active involvement of the public has proved to be of utmost importance for a successful
implementation of the concept of sustainable stormwater management. This integrated
approach (Model B) is much more complex and time-consuming than the traditional
approach to stormwater planning (Model A).
Many cities tend to continue to use the traditional approach (Model A) for planning sustainable
stormwater solutions. As this approach is not very well suited for planning stormwater
solutions, which are closely interacting with the societal processes in the urban
environment, the result will often be unsuccessful. For planning sustainable stormwater
systems one should apply Interactive Implementation (Model B).
Experiences show that sustainable stormwater drainage is a most efficient way of handling
stormwater from both existing and new developments. It must be emphasized that
time plays an important role in the integrated planning. To obtain public and political
support for a plan, it is necessary to include among others history, timing and uncertainty
in the planning process.
Acknowledgements
This paper was developed with financial support from the European Research programme
Interreg IIIB and from the Swedish Research Council for Environment, Agricultural
Sciences and Spatial Planning (Formas).

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INTERNATIONAL GREEN ROOF INSTITUTE
New Approach to Sustainable
Stormwater Planning
Traditional models for planning urban water systems are to
great extent based on technical and economic considerations.
This approach is adequate for planning isolated and
well-defi ned water systems. With the introduction of the
concept of sustainability, the water systems interact with societal
processes in the urban environment. We are then not
any more dealing with an isolated water system but with a
complex adaptive system. For such systems the traditional
planning models are not good enough. A more integrated
planning approach is needed.
In complex adaptive systems, time plays a very important
role in the planning. Among the conditions that must be taken
into account can be mentioned:
• The complexity of the system
• The past (history)
• The present and the future
• The timing
• The uncertainties of the system
Speeding up a complex process often results in unforeseen
rebound effects (“More haste, less speed”).
Different techniques for sustainable stormwater drainage
are described. Based on experiences in the city of Malmö
in Sweden a practical approach for integrated planning of
these types of drainage systems has evolved. The new approach
is called Interactive Implementation. As a result multiple
use of stormwater facilities has today become general
practice in Malmö. The outcome of some sustainable stormwater
projects is presented.
ISBN 91-973489-4-5
Augustenborg’s Botanical Roof Garden
This publication is a part of a bigger project aiming
for greener, more sustainable cities. Augustenborg’s
Botanical Roof Garden, in Malmö, Sweden, is a centre
for research, information and inspiration about living
green roofs. On top of a group of industrial buildings
in the area of Augustenborg, the City of Malmö, supported
by the EU and the Swedish Ministry for the
Environment has created a unique establishment to
inform the public about the advantages of green
roofs. Living green roofs have positive effects on the
environment in many different ways:
• Storm water management
• Energy effi ciency
• Better local climate
• Noise reduction
• Habitats for wildlife
• Aesthetics and well-being
Augustenborg’s Botanical Roof Garden is made to
inspire with its beauty, at the same time as it is an
important research site where a number of different
universities are involved in research around for
example green roof technologies, plant materials,
nutrient balance, storm water management, run-off
quality, noise reduction, energy saving, increased
membrane life, users’ aspects, biodiversity and
development of new habitats.
The botanical roof garden can be visited live, or on
the website.
International Green Roof Institute (IGRI)
In connection with the botanical roof garden, a
green roof institute, IGRI, is working to promote the
use of green roofs. The most important task of the
Institute is to co-ordinate the research around living
green roofs, as well as educating and spreading
information. IGRI co-operates with Malmö University
on a university course on green roofs. Yearly international
and national research seminars are arranged
to share knowledge and to further the aim of IGRI
– to contribute to a sustainable future through an
increased use of green roofs.
More about IGRI and Augustenborg’s Botanical Roof
Garden on the web: www.greenroof.se
formas