Objective: To provide a transparent analysis of the changing cost structures, benefits, and financing options associated with the implementation of blue-green infrastructure.

Coaches: Jan Hendrik Trapp and Dr. Stefan Schneider (Difu)

The costs, benefits, and financing of blue-green infrastructures represent the socio-economic dimension of the coaching toolbox. The transformation-related changes often give rise to challenges that lie in the specific constellation of actors, required resources, technical components, and regulatory relationships within these infrastructures.
Blue-green infrastructures offer numerous advantages in combination with grey, technical infrastructures, for example, regarding flood prevention, ambient temperature, biodiversity, and quality of life in cities. However, their specific design significantly determines the expected cost-benefit effects, meaning these must be carefully considered during the planning and financing phases.
The specific costs of such infrastructure projects vary considerably and depend not only on the concrete technical implementation but also, and especially, on the framework conditions of a project. Two cost categories must be distinguished in connection with the introduction of blue-green infrastructure: firstly, the often higher transaction costs compared to traditional central drainage systems, which arise during the planning, coordination, and consultation of stakeholders; and secondly, the costs for replacing and supplementing existing urban drainage infrastructure with blue-green infrastructure.
Furthermore, it is important to differentiate between a micro- and a macroeconomic perspective. From a microeconomic point of view, the focus is on costs (and benefits) at the level of individual properties or individual infrastructure components. The focus here is on owners, users, and local stakeholders. Specific interests regularly emerge that require negotiation and cooperation between the parties involved.
From a macroeconomic perspective, blue-green infrastructure can influence, for example, the land and property values of surrounding properties, the quality of life in neighbourhoods, and the overall common good. The macroeconomic effects, such as improved quality of life, climate adaptation, and increased resilience, justify public measures but simultaneously pose challenges regarding a fair distribution of costs and benefits. Put simply: Who pays and who benefits?
The widespread implementation of blue-green infrastructure changes and shifts the level, types, and causes of costs. For example, maintenance costs for technical infrastructure at the city's drainage department may decrease, while maintenance costs for city parks at the parks department may increase.
In user-financed areas, this can have a direct impact on the personal finances of people in a city. For some, this could become a problem if their own financial contribution increases significantly.
Climate-adapted urban development using blue-green infrastructure therefore goes far beyond technical issues and requires an integrated approach that considers not only ecological but also economic and social aspects, thus laying the foundation for a sustainable and socially balanced transformation. The coaching toolbox offers two powerful instruments for this purpose, which have repeatedly proven their worth in practical application:

• netWORKS 4 Info Cards: Tool to support participatory planning processes (more information at: https://networks-group.de/de/networks-4/infokarten.html )
• Constellation analysis: A method for developing cooperation models in the implementation of blue-green-grey infrastructures (Schramm, Engelbert; Trapp, Jan Hendrik; Stein, Christian; Rauchecker, Markus (2023): Development and maintenance of blue-green-grey infrastructures for municipal climate adaptation. Case studies, constellations and cooperation management. Ed. by the netWORKS research network. Berlin (netWORKS Papers, 39). Available online at https://repository.difu.de/jspui/handle/difu/583721 .; originally developed by: Schön, S., S. Kruse, M. Meister, B. Nölting, D. Ohlhorst (2007): Handbook of constellation analysis: An interdisciplinary bridging concept for sustainability, technology and innovation research. Oekom, Munich 2007.)

Furthermore, as part of the coaching, other existing tools will be used and, if necessary, adapted to answer specific questions (e.g., the Berlin Rainwater Agency's Rainwater Calculator ( https://regenwasseragentur.berlin/kosten-regenwasserbewirtschaftung/ ), the Berlin Rainwater Agency's "Orientative Cost Estimate for De-Sealing Measures" guide ( https://www.berlin.de/sen/uvk/umwelt/bodenschutz-und-altlasten/vorsorgender-bodenschutz/vorsorgender-bodenschutz-nichtstofflich/entsiegelungspotenziale/ ), or the IÖW's "Garden Services" urban green space assessment tool ( https://www.gartenleistungen.de/publikationen/infografiken-und-factsheets/ ). If required, participants can also (further) develop their own methodological approaches to guide cost estimates with reasonable effort.