Nature-based solutions unlock measurable value in cities

Cities are rethinking how they manage stormwater while improving urban life, biodiversity, and climate resilience. Nature-based solutions (NBS) can address these challenges in one integrated approach. Yet their full value is rarely captured in traditional project assessments.

Ramboll has developed the NBS Value tool to quantify and monetise the broader benefits of these solutions, including improved health, better urban environments, and enhanced biodiversity. This creates a stronger foundation for comparing solutions and prioritising investments.

"Blue-green solutions in urban environments can deliver value that goes far beyond water retention and treatment. The ability to assign value to these co-benefits strengthens decision-making and supports the development of more climate-resilient cities and that is very exciting," says Allan Bo Mikkelsen, Project Manager for Climate & Wastewater at Aarhus Vand.

Applying the approach across Aarhus

In collaboration with Aarhus Vand, Ramboll applied the NBS Value tool to three projects at three locations in Aarhus: Åbyhøj, Fredensvang, and Vesterbro Torv. The projects represent different scales and stages, from local interventions to large urban transformations.

Across all three cases, the analysis shows a clear pattern: when co-benefits are included, nature-based solutions provide a significantly stronger overall value than traditional approaches.

In Åbyhøj, the analysis focused on two green streets and an urban park.

The results show that:

• Green streets improve how people move through the area and increase traffic safety
• The park creates space for recreation, physical activity, and biodiversity

The calculated socio-economic value of the solutions amounted to minimum 5.3 million DKK per year. However, additional blue-green measures have since been implemented in the district, meaning the calculated value represents only part of the total provided co-benefits.

Scaling impact in Fredensvang

In Fredensvang, six types of interventions were analysed, including parks, streets, residential areas, and public spaces. These were used to assess three development scenarios:

• A pipe-based solution
• A fully nature-based solution
• A hybrid approach

Allan Bo Mikkelsen says: "Ramboll supported us in calculating and pricing co-benefits for these three very different projects, from a large-scale separation project with green solutions across roughly 200 hectares, to the evaluation of an already completed project, and a major urban-redevelopment and climate initiative in central Aarhus. These processes have been insightful."

The results show that:

• Nature-based solutions deliver the majority of socio-economic benefits - four times as much as the hybrid approach, while the pipe-based solution delivered close to none
• Multifunctional design significantly increases returns with limited additional cost
• Scalable solutions such as green streets generate substantial cumulative benefits

The comparison highlights how early integration of co-benefits leads to better-informed decisions and more robust project outcomes.

Transforming Vesterbro Torv

At Vesterbro Torv, the project transforms a traffic-dominated area into a multifunctional urban space that combines climate adaptation with improved urban life.

The results show that:

• Recreational value and improved urban experience are the largest contributors
• Green infrastructure improves air quality and supports carbon sequestration
• Traffic safety increases when pedestrians and cyclists are prioritised

The project demonstrates how relatively modest investments can significantly increase the value of urban spaces when solutions are designed to serve multiple purposes. In the case of Vesterbro Torv, the annual socio-economic value of co-benefits of its transformation is minimum 7 million DKK. Moreover, subsequent cost-benefit analysis including the monetized co-benefits shows that for each 1 DKK invested in the project, the city of Aarhus gets approximately 1.5 DKK back.

Supporting better decisions

The collaboration between Ramboll and Aarhus Vand shows how quantifying co-benefits strengthens decision-making in climate adaptation projects.

By making the full value visible, utilities and municipalities gain a clearer basis for prioritising solutions that deliver long-term benefits for both people and the environment.

As cities continue to adapt to climate change, the ability to measure and compare the full impact of solutions will become increasingly important.

Tools such as NBS Value support this shift by enabling more transparent, data-driven decisions and unlocking the potential of nature-based solutions in urban development.