Nature Based Solutions - Implementation Models Database

Rain/infiltration gardens

DrainGarden in Ober-Grafendorf

A short description of the NSB

The drainage of rain water in public spaces is becoming an increasing challenge for settlement areas. Increasingly frequent heavy rainfall incidents lead to surface flooding in expanding settlement areas and damage of private and public property. The adaptation of the entire drainage system - from sewer grates over pipe cross-sections, pumping stations, treatment plants and retention systems to the impacts of current and future weather conditions - represent an enormous burden of cost for municipalities. An economically attractive and ecologically valuable alternative are DrainGardens, planted with perennial vegetation or shrubs and specific substrates. DrainGardens help retain rain water locally and deliver it purified to the groundwater. This corresponds also to the objectives of the EU Commission. The plants evaporate the stored water gradually and improve the microclimate. The project “eco-street” (Ökostraße) implemented in the municipality of Ober-Grafendorf represents a smart, decentralised, ecological rainwater management system based on an environment-friendly urban street design (DrainGarden). It is a system of vegetated, aesthetically appealing roadside surface strips covered with special substrates of natural origin and planted with greenery that are able to absorb, retain, store and filter large amounts of water in short time. The specifically developed soil substrates are layered in a way as to combine high water permeability with high storage capacities. In case of heavy rainfall the water is not flowing from streets and other paved surfaces into the sewer, but into the green areas. Each cubic metre of substrate can store up to 500 litres of water. As it is required by regulations in place for conventional water retention structures, the system is designed to assure flood protection up to heavy precipitation events with a 100 year return interval. The water remains available to the plants, is filtered by the substrate and allowed to infiltrate slowly into the groundwater body. The micro-climatic effect of the water used by the plants for transpiration equates to the cooling capacity of a 100-years-old beech tree on a hot summer day and is able to reduce the local temperature by up to 5°C during heat periods. Further environmental co-benefits include the storage of CO2 by plants and substrate, the containment of growth of sealed soil, an increase in urban green spaces, and visual improvement of the townscape. The system allows the municipality to avoid investment costs for construction of additional sewage pipes as well as regular operational costs for maintaining the sewerage and operating pumping facilities. In addition, the existing urban water drainage system is disburdened, and costs for operating the municipal wastewater treatment facility as well as for irrigation and maintenance of the urban greenery are reduced. Selection of the right plant species is a crucial factor for success of the measure. Apart from being in compliance with road safety standards, the greenery should be designed as to avoid drivers and walkers from damaging the system, which can be achieved by using shrubs, flowering and soil-covering species. On the other hand, suitable plant species need to be adjusted to the local climate and should be perennial, easy to maintain and robust, including resilience against de-icing salt during winter time. The project has been designed as a scientific experiment whose performance parameters are currently continuously monitored in order to learn for future applications. The adaptation measure is particularly suited for the secondary street system in settlements and for newly developed settlement areas. With necessary modifications, the rainwater management system can be tailored to other situations, such as green roofs, car parks, and private housing. The “eco-street” concept has received much attention by both the public and experts, and it is considered an important innovation in sustainable local road construction. The municipality Ober-Grafendorf intends to widely apply the concept on its territory, therewith reducing the share of sealed surface area.

NBS Implementation context
Location Ober-Grafendorf (Austria)
Status (from - to) Project delivered (2015-2016)
NBS Scale Object (streets) Neighbourhood City
NBS Impacts scale Object (street) Neighbourhood City
Urban density/ Soil consumption High (dense city center)
NBS Typology


NBS Uban Challenges
Climate Issues Climate mitigation
Climate adaptation
Other 0
Urban water management and quality Urban water management and quality
Flood management
Other 0
Air Quality Air quality at district/city scale
Air quality locally
Other 1
Urban Space and Biodiversity Biodiversity
Urban space design
Urban space management
Other 0
Urban Regeneration and Soil Air quality at district/city scale
Other 0
Resource efficiency Food, energy and water
Raw materials
Waste
Recycling
Other 0
Public health and well-being Acustic
Quality of life
Health
Other 0
Environmental justice and social cohesion Environmental Justice: Recognition
Environmental Justice: Procedural Justice
Environmental Justice: Distributional Justice
Environmental Justice: Capabilities
Environmental Justice: Responsibility
Social Cohesion
Other 0
Urban planning and governance Urban planning and form
Governance in planning
Other 0
People Security Control of crimes
Control of extraordinary events
Other 0
Green economy Circular economy
Bioeconomy activities
Direct economic value of NBS
Other 0
Other
NBS Stakeholders & Governance

The project was initiated by the Mayor of Ober-Grafendorf, who has long been a strong proponent of sustainable and environment-friendly solutions in municipal development. The decision to finance and install the adaptation measure has been taken by the municipal council. Since the measure was to be realized in a new urban area that was still undeveloped, there was no particular need to further involve residents in the decision. However, as it is required by the spatial planning laws in Austria, the preceding local spatial development plan and the concrete zoning plan have been subject to stakeholder participation and public consultation. Crucial contacts to external experts were brokered by the long-term gardening service provider of the municipality. On behalf of the municipality, the project has been implemented in cooperation with the University of Natural Resources and Life Sciences Vienna and the consultancy firm Zenebio GmbH, who had already invested several years of research in developing smart rainwater management systems.

Initial actors (Leaders) Governments Local government/municipality (Ober-Grafendorf Municipality)
Involved actors Governments Local government/municipality (Ober-Grafendorf Municipality),Community Citizens Research institutions (University of Natural Resources and Life Sciences Vienna),Market Social enterprises / social entrepreneurs (Zenebio GmbH)
Ecological scale Local scale green area
Governance model CLUSTER 5: Network Governance Collaborative governance
NBS Financial aspects

In comparison to conventional structural solutions, the smart, ecological urban rainwater management system implemented in Ober-Grafendorf has considerable cost advantages, both over the short and the long term, and it delivers a range of environmental co-benefits. Depending on the dimension and the accessibility of the site, the absolute investment costs for implementing the eco-street/DrainGarden concept can vary from case to case. The cost of the substrate for one cubic metre is about 100€. Depending on the choice of plants, the cultivation cost ranges from two €/sqm for seeding to several thousand €/sqm for planting large woody perennial plants. While a budget of 65.000€ was available for the process management and support services within the EU co-funded C3-Alps project ‘Capitalising Climate Change Knowledge for Adaptation in the Alpine Space’, the municipalities and other stakeholders did not receive any funding or remuneration for participating in the regional pilot process and for implementing concrete measures. However, the process managers provided consulting and advise on available financial incentives and financing opportunities within existing funding programs of the provincial state and the federal government. In general, the adaptation activities defined and implemented by the municipalities often were soft and low-cost measures, rather than technological solutions requiring substantial investments.

Global (estimated) cost of the project -
Financing mechanism CLUSTER 1: Public financing
NBS Business Models Archetype
Technological Non applicable
Social Non applicable
Organisational Develop scale-up solutions
NBS Success and limiting factors
Process enablers
Knowledge Generation of evidence Lesson learnt through implemented projects, Collaboration Co-creation, Awareness Climate Change
Governance Process efficiencies Collaboration Coordination role, Co-creation and participation Co-production
Economy De-risking Sharing risks, Government support Provisioning of incentives to attract private investment
Process inibitors
Knowledge Uncertainty Operational unknown
Governance -
Economy Budget constraints
IM Keywords
  • Collaborative governance

  • Local scale green area

  • Public financing

  • Develop scale-up solutions

References
forschung.boku.ac.at/fis/suchen.projekt_uebersicht?sprache_in=en&menue_id_in=300&id_in=10721 climate-adapt.eea.europa.eu/metadata/case-studies/environment-friendly-urban-street-design-for-decentralized-ecological-rainwater-management-in-ober-grafendorf-lower-austria