Z E S Z Y T Y N A U K O W E P O L I T E C H N I K I P O Z N AŃ S K I E J Nr Seria A r c h i t e k t u r a i U r b a n i s t y k a Rok 2009

Karl H.C. LUDWIG*

DESIGNING WITH RAINWATER

After decades of banishment from cities and housing developments, water has become a significant design feature in urban settings, and rainwater management concepts are a frequent feature of innovative architecture today. Nine projects exemplify and illustrate the creative use of water in housing areas and buildings.

Keywords: design, rainwater

Water is one of the most universal elements on earth; without water there would

be no life, whether for humans or for landscapes. It is the world's softest element, and the cycle of precipitation, evaporation and condensation that makes up the worldwide system of water transport never seems to end. In fact, regions such as Central Europe never seem to run out of water, and the people living here often feel that it rains too much.

However, burgeoning urban development is changing the water cycle all over the world. The impermeable surfaces of urbanized areas prevent precipitation from infiltrating down to the natural water table as it does out in the open countryside. Instead, over half of the rainfall in such areas disappears into the sewage system - out of sight and out of our mind.

But water can be returned to sight and to awareness as a vital element if use is deliberately made of it as a design/planning element. Indeed, its potential as a sculptural medium is unsurpassed. Not only is water transparent - it can take on various colours and forms, move in various ways and it also addresses the emotions. In other words architects, landscape architects and urban planners are finding it a most desirable and interesting element.

Understanding water is not something that can be gleaned from books but is a matter of experience, an open mind, a willingness to think and plenty of examples. To stimulate interest in designing with water, examples of different ways of using rainwater ecologically and as a design element are provided as follows. Most of them are the work of Herbert Dreiseitl, who started to design * Fakultät 5 - LUS, Landschaftsarchitektur, Umwelt- und Stadtplanung HfWU - Hochschule für Wirtschaft und Umwelt Nürtingen-Geislingen, Nürtingen, DE.

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with rainwater at a time when few people were courageous and crazy enough to do so.

It took some years to convince and persuade Herbert to have at least a selection of his projects published in a book, but one with the title Waterscapes we eventually produced a few years ago. Today his studio is a multi-disciplinary planning office involved in a broad range of project types on a global level. Most of the projects described here are taken from the last decade, starting out with a small example that marks a sort of a starting point and leading on to more complex measures.

1. WIND- AND WATER-WHEEL IN OWINGEN

The fact that rain is necessary but is often difficult to forecast precisely makes people feel that it never comes at the right time. We feel similarly about the wind - that is, unless we enjoy going sailing. Children, to whom wind and weather mean change usually see this differently, and for this reason Herbert Dreiseitl wanted to make something positive out of wet and stormy weather. In 2000 he was offered the opportunity to realize this idea at the primary and secondary school in Owingen, a small town in the hinterland of Lake Constance, Germany.

Fig. 1 Owingen-plan (waterscapes-p59). General plan of the drainage system for the school showing the collecting the runoff stemming from the 360-square-metre roof area

As so often in his work,

the approach he took to the project was not just artistic but also very functional and indeed ecological, since it returns rainwater to the natural cycle. For technical and financial

reasons, a decentralized open rain-water concept was chosen. In his design, some of the runoff stemming from a 360-square-metre roof area is led into an open court, where it seeps away into a small pond, an attractive area in its own right. Most of it, however, runs along a metal gutter on the outside of the building, where it reaches an undulating concrete wall into which a playful installation is let. This consists of two red wheels with rotor blades and a water-wheel with six blue metal scoops that respond wind or water gushing in from the gutter. Once passing the water-wheel, the runoff leads along a further gutter and continues under a path to a system of hollows and trenches, occasionally turning the playing field into

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a temporarily water-filled infiltration swale in the process. A sheet of blue metal keeps the urge to climb the undulating wall and the wind- and water-wheel within limits.

Fig. 2 Owingen. Water from the roof flows through to a wind-and-water-wheel, where it sets the rotor blades in motion, and then continues through an undulating concrete wall

2. THE NUREMBERG PRISMA PROJECT

The Prisma Project in Nuremberg is a complex of 61 apartments, 32 offices, nine shops, a coffee shop and a kindergarten designed by the Tübingen architect Joachim Eble according to urban ecological criteria. Rainwater is assigned crucial importance in that all the roof runoff is harvested. Some of it is guided through various cleaning phases into a 300-cubic-metre holding tank, whereby any overflow is filtered through gravel below the basement garage into the ground. The water is then pumped from the tank into two separate circulating systems, the first of which is used to supply the plants and the pond in the four-storey conservatory foyer on the inside court of the complex.

The second system feeds the runoff to six water walls in the foyer, which facing south and south-west gets very hot in summer. The 5-metre-high water walls have a number of positive effects in that the water streaming down them pulls in outside air through a slit in the wall, cleaning it in the process and cooling it in summer. In winter, when the water is kept at a minimum temperature of 18° C, this effect helps warm the inside of the foyer.

The water walls not only offer benefits in terms of air temperature and humidity but also a visual one in that they make an impression of art objects on visitors. The constant flow of water changes their polychromatic appearance during the day and especially at night, and the sound of the water has a calming effect.

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Fig. 3 Prisma-principle1. This section shows the rainwater concept of Prisma Project - with collection, storage, purification and infiltration

Fig. 4 Prisma-principle2. The rainwater collected is used for natural air conditioning, fire-fighting and plant watering

Fig. 5 Prisma. The multi-storey glass building creates an attractive ambience within the city centre

Fig. 6 Prisma. - Six water-walls and the vegetation create a healthy atmosphere with the constant flow of water giving an ever-changing appearance during the day and especially at night

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3. HOUSING ESTATE ARKADIEN ASPERG

Arkadien Asperg seems like the built vision of an 'urban village' in which density and privacy are able to coexist even within such a congested area as the Stuttgart conurbation. Environmental resource protection in the form of rainwater harvesting ranked high on the priority list for the two-hectare development, again the work of Joachim Eble Architects. Roof runoff is collected in a number of cisterns. These range from a 60-cubic-metre tank that mainly feeds a small manmade streamlet via paved channels, to 14 smaller cisterns that are distributed around individual houses to provide water for use in irrigation, toilet flushing and washing machines.

Fig. 7 Arkadien-streamlet. An newly created streamlet, accompanied by a small footpath, is a characteristic feature of the Arkadien Estate

Fig. 8 Arkadien-streamlet. The squares and pockets at more public points are spaces for creative play for adults and especially children such as this stainless steel weir

Space for a central village plaza, complete with a fountain, was found

by locating parking in an underground garage, and in the meantime this area has become the social centre of the estate. Unity in design and extensively planted open spaces with a clear relationship to the surrounding buildings shape this generous

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complex with its Mediterranean touch. The diversity of semi-public and private spaces matches the wide variety of passive housing types. The streamlet, which has natural and planted banks, meanders through semiprivate community spaces, offering play elements such as a stainless steel weir and an Archimedes screw at more public points.

4. KÜPPERSBUSCH HOUSING SCHEME IN GELSENKIRCHEN

For decades, Küppersbusch was known in Germany as a manufacturer of high quality kitchen furniture and cooking stoves. The company had to close down in the 1980s and its site gradually took on a brownfield character. In the 90s, it was transformed into a housing estate featuring architecture by Szyszkowitz + Kowalski of Graz, Austria, and open spaces by Brandenfels of Münster, Germany.

Fig. 9 Küppersbusch -plan. The lens-shaped plaza forms the heart of the Küppersbusch Housing Scheme acting as a central pocket park …

Fig. 10 Küppersbusch –plaza. … as well as a rainwater reservoir and infiltration swale

The estate itself is divided off from a nearby railway line by an embankment

that consists of contaminated material taken from the site and covered by a membrane barrier and a thin layer of earth. A lens-shaped plaza forms

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the heart of the development, acting as a central pocket park for the housing scheme as well as a rainwater reservoir and infiltration swale. Some 80 percent of the runoff from the roofs surrounding the plaza can be collected and led to the plaza, where a series of small concrete walls withholds the water and helps it to infiltrate directly into the ground. The runoff from the roofs reaches the plaza by pole-supported gutters, which despite being prone to minor problems lend the estate a very distinctive look.

5. THE KRONSBERG HOUSING ESTATE IN HANNOVER

Do you remember Expo 2000, the World Exhibition held in Hannover, Germany? One of the principle goals of the event was to foster sustainable urban development, as in the case of creation and implementation of an open space concept for Kronsberg Housing estate, a new urban district 130 hectares in size set on a hill next to the Expo. The landscape design took the theme of ecological optimization into consideration with an innovative rainwater concept that focuses on on-site infiltration and retention. The idea was that not a drop of the rainwater falling on roofs, roads and squares was to disappear into the sewage system but to seep into the ground or soak away at the foot of the hill, thus feeding a valuable aquifer below it, even in dry periods.

Fig. 11 Plan of Kronsberg housing estate: The sloping avenues and retention areas at the foot of the slope show up as a system of linear stripes of the urban parkland

Fig. 12 Kronsberg. Rainwater is stored temporarily in the sloping avenues open spaces with retention lips and then runs down to the bottom of the slope

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This has been largely achieved by creating two 13 x 30 metre green areas parallel to the slope and three parkland strips arranged in a row along its bottom. These areas of green receive all the surface water from the private and semi-private spaces and the estate's parks that does not soak away, evaporate or be retained in some way.

Rainwater that does not infiltrate directly into the ground is collected in swales provided with sub-surface storage capacity and reduced outflow detention channels. From here it ultimately drains into nine retention ponds, which as the site's main collection areas form part of a recreational open space in which changing water levels serve as an appealing feature to draw all age groups closer to the natural environment.

The retention and soak-away areas on the slope and at its foot are rightly called open spaces, whereby some of the retention ponds are specially reinforced with a cohesive substrate to promote extended use and enjoyment of these outdoor amenities. Although the housing estate is only 20 percent permeable, a simulation of natural infiltration has shown that recharge of the aquifer is the same as before construction.

6. THE SCHARNHAUSER PARK PROJECT IN OSTFILDERN

Traditionally speaking, military or barrack architecture has little in common with quality of life. The buildings are arranged and developed from a purely functional point of view and have little concern for such aspects as ecological impact, yet they nevertheless have hidden potential.

Once no longer required by the military, they certainly take the pressure of towns to develop new building areas. A case in hand is that of Scharnhauser Park, near Ostfildern, for which Wolfrum + Janson of Karlsruhe provided the urban development plan. The 150-hectare, southern-sloping site is one of the largest contemporary urban development schemes in and around Stuttgart. From the very start of the planning process, Atelier Dreiseitl led the effort to sustainably manage its rainwater, whereby it was clear that the precipitation would have to be treated in a way that complemented the fresh, contemporary philosophy guiding the redevelopment. An emphasis is placed on water as such at the multi-storey water curtain that embellishes the entrance of the new so-called 'City House', designed by Berlin architect Jürgen Mayer H.

To avoid flooding, particularly as rainwater disposal is now disconnected from the sewage system, the design implements a strategy of discharge reduction, discharge delay and modest infiltration into the clayey subsoil. Runoff that is not retained in private storage tanks or on roof gardens, is used to feed a system of open channels and ditches alongside the streets and central open spaces. This water network, which runs through the new estate as an unmistakable design feature, leads on to 40 landscape steps that cascade downhill for 1.5 kilometres

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in particularly striking fashion. At the bottom of the steps, the water is purified in retention hollows and pools in a living substrate zone before continuing on to nearby wetlands and biotopes via natural gradients.

In this way, the water elegantly overpowers the remnants of the old military barracks while forming harmonious new links with the landscape surrounding the Scharnhauser Park Project.

Fig. 13 Site plan showing the system of rainwater management in Scharnhauser Park with the landscape steps as the green backbone

Fig. 14 Multifunctional grass-surfaced swale area in Scharnhauser Park

7. TANNER SPRINGS PARK IN PORTLAND, OREGON

Formerly a wetland close to the broad Willamette River, Pearl District was once bisected by Tanner Creek until rail yards and industry claimed and drained the land. Over the past 30 years, a new neighbourhood has progressively established itself - young, mixed, urban and dynamic. Today Pearl District is home to families and businesses. While the district was expanding into the last of the rail yards, the City of Portland engaged Atelier Dreiseitl to design a new park to bring green space into this previously industrial area. As a result, the urban skin of a downtown 60-by-60-metre wasteland block has been peeled back with surgical artistry.

Given its natural inspiration, the park was envisioned as a model of urban sustainable design. All runoff from the park is directed into a cleansing biotope at one end of the park rather than out to the curbs and gutters of surrounding streets. An undulating wall made of historic railroad tracks set on end curves in

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and out behind the biotope area as a symbol of the old city fabric. Some 60 metres long, it features pieces of fused Portland glass with pictures of insects and amphibians hand-painted by Herbert Dreiseitl. From the inclusion of public art and the cleansing of urban runoff to creation of a place where red-winged blackbirds, great blue herons and local residents alike can find respite from the stresses of contemporary urban life, Tanner Springs Park shows that it is possible to find nature in the city again.

Fig. 16 At the beginning of the project citizens were invited to present their own ideas and opinions at several public workshops

Fig. 15 Master plan for the Tanner Springs Parks

Fig. 17 The inlaid glass pieces in the undulating art wall, created from historic railroad tracks, are an echo of the grasses in the foreground

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8. WATER TRACES IN HANNOVERSCH MÜNDEN

Hannoversch Münden is a small central German city that features a remarkable ensemble of historic houses in its old quarter. As is the case with many settlements that developed alongside rivers, water has often brought it both great happiness and great misery. The Fulda and Werra rivers that meet here to form the Weser flow past behind the old quarter, and although they have given the city its name (münden means to flow or empty into), they play an insignificant role today, both for the city and in the awareness of many people.

Fig. 19 The shallow water allows to play on the terraced steps of the ‘water carpet’; three glass pillars with light an sound accentuate the square

Fig. 18 In Hannoversch Münden the city’s central ensemble of connected squares has been revitalised by different water traces

Fig. 20 Section through the square: The light is caught on the sand-blasted relief on the pillars, passes through the gap in the V to a mirror at the top, which directs the rays down on to the water steps and then reflects their ripples on the wall of the town hall

An ensemble of connected squares sloping downward towards the north marks

the heart of the old quarter, and when decisions were taken to calm the traffic

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in this area, people had the idea of redesigning and revitalising the squares. A theme was quickly found: water traces, the paths followed by water courses, were to be made visible again.

The way in which the project was organized largely contributed to its success. Six working groups chaired by an architect and made up of residents, landscape architects and fine artists developed a wide range of ideas. Experts worked together and with laymen in an open atmosphere and finally came up with six works of art for the ensemble of squares. The contribution by Atelier Dreiseitl mainly uses rainwater, and has been realised in the square between the church and the town hall in the form of four small terraced steps that resemble a large folded carpet. Water bubbles out of the topmost and narrowest of these steps and runs down over the next ones to a stainless steel gutter at the bottom, where it is returned to a circulation tank.

Fig. 21 The rhythmic patterns on the surface of the water are reflected on to the town hall façade by lighting management

Today people of all ages go in search of the traces left by the water

on the terraced steps. Not only is it always changing due to differences in the subsoil but people are also able to make their mark - an effect that was very important to the artists and planners. The flow pattern of the water changes if people simply step onto the steps or interact with the acoustic vibration plates, slides and wave-making devices placed around the water scene. The overall effect is further enhanced by three light pillars made of V-shaped glass about 5 metres high and lit obliquely after dark. The light is caught on the sand-blasted relief on the pillars and in each case passes through the gap in the V to a mirror

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at the top, which directs the rays down on to the water steps, reflecting their ripples on the wall of the historic town hall. Loudspeakers mounted into the pillars can be activated to produce artistically alienated voices or water sounds as a pattern of urban noise.

9. THE WATER SYSTEM IN BERLIN'S POTSDAMER PLATZ

Not many years ago, Potsdamer Platz in Berlin was Germany's largest building site. After the fall of the Iron Curtain, there were immense expectations of the desolate space, which was a major traffic intersection before World War II bombing and division by the Berlin Wall. The problems involved were also highly complicated. As such there were two basic requirements - the square was to be a place of work and also of leisure beneath the shadows of the planned towering headquarters of important global players. Despite the very limited space available for leisure provision, the idea of setting high ecological standards caught on as well. The theme of water as a defining open space element convinced both the Berlin Senate and different investors, their imagination fired by the design possibilities and the chance of meeting ecological challenges. The suggestion of using rainwater for flushing toilets and watering green areas also met with interest.

The same was true of the idea of collecting runoff in subterranean cisterns

and using it to feed a water system that involves a narrow pool on the north side of the square, a large pool in the middle, another to the south and a water feature in the piazza. This proposal also provided the opportunity to not lower

Fig. 22 Potsdamer Platz: Master plan of the site with the main urban water features

Fig. 23 System of the rainwater management at Potsdamer Platz

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the groundwater level during the building phase and to collect runoff and slowly feed it into the nearby Landwehrkanal. A complex computer simulation proved that the canal would only have to absorb peak stormwater levels three times in ten years, but that the system would need adequate buffer capacity to cope with these incidents.

Having found favour, the rainwater proposal was realised, with the necessary buffer capacity primarily being provided in the form of five subterranean cisterns with a total volume of 2,600 cubic metres; in addition, the main pool of water has a 15-centimetre reserve between normal and maximum water level, yielding another 1,300 cubic metres of buffer capacity. After solids have settled in the subterranean cisterns, the runoff reaches the southern and central pools via purification biotopes, whereby technical filters can be used if necessary to remove any floating algae in summer. At the piazza, the water flows over shallow flow-steps, creating intricate patterns in the process - a detail that was worked out in 1:1 models by Atelier Dreiseitl.

LITERATURE

[1] Burkhardt, Hans G. u.a.: Wasserspuren - Wasser sichtbar machen: Die Partizipation

einer bürgerlichen Öffentlichkeit am städteplanerischen und künstlerischen Projekt der Weltausstellung Expo 2000. Verlag Jens Kalkmann, Bodenburg 2000

[2] Dreiseitl, Herbert; Grau, Dieter + Karl H.C. Ludwig (Hrsg.): Waterscapes. Planen, Bauen und Gestalten mit Wasser. Verlag Birkhäuser, Basel / Berlin / Boston 2001

[3] Dreiseitl, Herbert + Dieter Grau (ed.): New Waterscapes. Planning, Building and Designing with Water. Birkhäuser Publishers, Basel / Berlin / Boston 2005

Fig. 24 Where two basic requirements meet - the Potsdamer Platz was to be a place of work and also of leisure beneath the shadows of the headquarters of global players

Fig. 25 At the piazza, active life and prestigious architecture meets while the water flows over shallow flow-steps