rainwatermanagement.ch Understandable and Easy to Use

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1 rainwatermanagement.ch Understandable and Easy to Use Peter PETSCHEK and Michael FLUSS 1 Introduction In Switzerland, a lot of information is provided by Cantons and other institutions on how to deal with rainwater. At first glance the published brochures give a good basic impression; this changes once you start working with them and discover the amount of complex hydrological information available. Transforming expert knowledge into a form which nonexperts can then apply in a construction project is not simple. Providing landscape contractors and landscape architects with an understandable and easy to use Workflow method for rainwater management was the main goal of the research Project which was funded by the Swiss Government Agency KTI. The Project is another example of how aspects of Information Technology besides the main CAD/GIS/VIS programs can be applied in the field of Landscape Architecture. 2 Laws, Fees and Costs The Swiss Federal Law for the Protection of Water underlines its strategy for rain water with the following quote: Non-polluted water has to percolate or filter into the ground as it would have before the natural ground was built on by various impermeable constructions. If this is not possible then the water must flow into rivers and lakes. To control flooding, retention measures have to be planned and built. Since 1991, the city of Zürich has been raising its rainwater fees. This has made the public more aware of the problem and most have since positively accepted rainwater management as it has the following advantages: For the average citizen: In Zürich, fees are 60% lower when rainwater is drained on site. Using recycled rainwater in the house or in the garden reduces yearly water fees. For the local government: Less expenditure for flood protection and prevention. Lower costs for drainage and sewer infrastructures. Lower construction costs for infrastructures in new housing areas.

2 rainwatermanagement.ch Understandable and Easy to Use 67 3 Products of the construction industry Nowadays there are many permeable above ground products on the market for example permeable paving stones. In Switzerland, the two products called Stabilizer and Saibro are often used for gravel areas. Both products include natural agents which bind aggregates and can therefore also be used in areas of ground water preservation. Regular interlocking concrete pavestones, like the products of our economic partner Tschümperlin also offer drainage functions. Some of the concrete products are porous and others have channels where water is allowed to penetrate. Studies to compare concrete pavers were done by Borgwardt in Even with technological advances, completing outdoor areas which are flat is still impossible, all surfaces have to have a slight slope to them and if the water still doesn t drain unaided, then manholes have to be positioned accordingly. The producers of rainwater usage and retention systems are developing interesting new products. On sites where ponds, basins and swales are not possible new modular retention systems like the REHAU RAUSIKKO BOX can be used. The products are made out of Polyethylene (PE), they work like sponges and can withstand soil pressures at a depth of up to 4 metres. The water which is led into these structures should be filtered first by the natural soil, if this is not possible new special filter systems which form parts of manholes should simulate the filtering ability of the natural soil. Because of these new systems, rainwater management is now possible in places where before a simple excuse like We have no space for ponds or swales was used. 4 Standards and Guidelines The Swiss Norm 592'000 Liegenschaftsentwässerung and the Guideline Richtlinien zur Versickerung, Retention und Ableitung von Niederschlagswasser in Siedlungsgebieten define standards on how to deal with rainwater on construction sites. The Swiss engineers and architects association (SIA), with its standard SIA 318 in Landscape Construction also refers to the above standards. The Guideline which should direct planners and builders on how to deal with the environmental critical issue of rainwater has one major fault; it was developed by hydrologists who did not realise that these guidelines were going to be used by people with little or no hydrological background. Landscape Contractors and Landscape Architects/Planners were not the focus group of the guideline for drainage, retention and run off. Nevertheless, in small and medium size construction projects these groups are always involved in the planning and building of rainwater management systems. These projects are too small to hire hydrologists; therefore important standards are not applied in a lot of construction projects. 5 REGENWASSERMANAGEMENT.CH To find out if there is a demand for a rainwater management system, the Hochschule Rapperswil (HSR) conducted a survey via . We received 60 answers from 120 consulted companies. The majority of answers was very positive. The survey showed a necessity for an easy-to-use tool for dealing with rainwater management. Based on the

3 68 P. Petschek and M. Fluss information above, the HSR, the Institute for Landscape and Open Space have developed the website REGENWASSERMANAGEMENT.CH. The project is supported by the Swiss Agency KTI and the main economic partner is the Swiss Landscape Contractor Association VSG. REGENWASSERMANAGEMENT.CH helps with the planning and the calculation of water percolation into the ground and its retention in small and medium sized projects. The contents of are as follows: Workflow Basic Information (Accessible without a Password) 0. Fees 1. Priorities 2. Laws and Standards 3. Subject to approval 4. Not subject to approval 5. Building a preliminary inquiry 6. Not possible 7. Optimization Preliminary Planning (Accessible only with a Password) 8. Measurements 9. Design 10. Percolation test on site 11. Requirements 12. Swales and Rivers 13. Dimensioning 14. Rough Decision 15. Building permits Construction Documents (Accessible only with a Password) 16. Surface Materials 17. Optimization 18. Construction Documents 19. Vegetation Several Excel sheets for calculations are integrated in the workflow.

A password opens the protected area with a complete workflow for rainwater

4 rainwatermanagement.ch Understandable and Easy to Use 69 Fig. 1: The content management system A password opens the protected area with a complete workflow for rainwater management. Fig. 2: Easy to use programs (mainly Excel sheets) for dimensioning of drainage and retention for small and medium size projects

5 70 P. Petschek and M. Fluss 6 Pilot Projects The developed workflow has been tested in two pilot projects. The first project is the new yard of a landscape construction company, and the second is a housing project. Besides testing the workflow, two more questions should be answered: 1. How much water drains on site using the paving materials Stabilizer, Saibro and the interlocking concrete pavestones by Tschümperlin? 2. How much water ends up in the REHAU RAUSIKKO BOX retention system? This was installed in the housing project, as space was limited. Landscape Architects often criticise the dimensions of retentions systems, saying that they are oversized. Home owners want to know if the drainage of the paving material used in their landscaping works over the years. The only way to clarify the above queries is to take measurements on site, therefore during the next three years tests will be run on both pilot projects. The first step in solving the queries involves making an estimate of the runoff volume. Many methods exist, we used the most popular which is the rational formula represented by the expression: Q = r A C Q Runoff rate in Litres per Second R Rainfall intensity in Litres per Second per Square Meter A Area of watershed in Square Metres C Coefficient of Runoff (Values used: Asphalt 1.0, gravel surface 0.6, etc. ) The runoff coefficient C is the ratio of peak runoff to the intensity of rainfall, In other words, it is the percentage of rainfall that doesn t filter into the ground. These values are related specifically to the infiltration rates of the soil, surface cover, channel and surface storage capacity, and rainfall intensity. The value of C is usually assumed by the designer based on some knowledge of the existing field conditions and the proposed structure. (LANDPHAIR & KLATT 118). For calculations with the runoff coefficient C, standard tables are used. The question is if these table values are correct for the used surface materials and do the measured C values change over the years? Our project partner IBU Institut für Bau und Umwelt (Fachstelle Geotechnik) installed sensors in the manhole structures and the retention system. The water that runs off is collected from the sloped surfaces. The water level is measured in a certain time interval with an Ultrasonic sensor. All sensors are controlled by a data logger. This instrument collects all data and sends it to HSR via GPRS. After receiving the data, HSR can calculate the real C-value for the different materials. This value cannot be generalised and used for other projects. It is only applicable on this site. Therefore IBU suggests building a simulation system under laboratory conditions. Additional measurements take place in the retention system of REHAU for gaining information on the amount of water, perlocation rates and dimensioning.

6 rainwatermanagement.ch Understandable and Easy to Use 71 Fig. 3: Plan of the pilot project of the yard of a landscape construction company Fig. 4: Sensor technology in order to monitor rainwater is used in the research project

7 72 P. Petschek and M. Fluss 7 Training The goal of REGENWASSERMANAGEMENT.CH is to develop a tool which is easy to use and can be understood by landscape contractors and landscape architects. The research team had to realize that the issue is complicated to make sure that with only a one day training course one will be able to use the webpage and the accompanied excel sheets. A password is provided during the training which can also be used after the one day training period, a password is given to ensure that only people that have taken the course can use the system. Once given a password, they are part of a network which will be informed on any further developments. 8 IT in LA This research project is using sensor technology in order to monitor rainwater. Other useful applications in landscape construction will follow. The construction industry is already spending a lot of money on research in the sensor technology field to create the Intelligent House, where lighting, security and heating are controlled by sensors. Information Technology (IT) in Landscape Architecture (LA) is therefore no longer restricted to drafting with CAD, analysing with GIS and visualising with Image Editing software. On site analysis GPS/Tachymeter equipment is supported by Landscape Architects. Construction site supervision without mobile communications is no longer possible. The Internet is the platform for research on materials, construction methods and companies. What we need is the awareness in our field that IT is an important part of our daily business and we should spend time and money on it for training and research. References Baudirektion Kanton Zürich (2005), Richtlinie und Praxishilfe Regenwasserentsorgung. Praxishilfe für Baubehörden und Planer Anweisungen für private Fachleute mit Vollzugsaufgaben im Gewässerschutz. Borgwardt, S. (1997), Leistungsfähigkeit und Einsatzmöglichkeit versickerungsfähiger Pflastersysteme. Sonderdruck aus BETONWERK + FERTIGTEIL TECHNIK BFT, Heft 2/1997. Bauverlag, Wiesbaden. Lanphair, H. & Klatt, F. (1979), Landscape Architecture Construction. Elsevier, New York. Schweizer Norm SN (2002), Planung und Erstellung von Anlagen für die Liegenschaftsentwässerung. Verband Schweizer Abwasser- und Gewässerschutzfachleute (2004), Regenwasserentsorgung. Richtlinie zur Versickerung, Retention und Ableitung von Niederschlagswasser in Siedlungsgebieten.

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