The result M7 “Nature based solutions for reducing the urban heat island” describes a nature-based solution to reduce the urban heat island effect and treat initial rainwater runoff in Mediterranean cities. These challenges affect public health, the integrity of natural ecosystems and the climate resilience of urban areas.

Two critical urban challenges are addressed:

First, the Treatment of the first-flush stormwater runoff, and second, the mitigation of the urban heat island effect.

These challenges impact public health, natural ecosystem integrity, and the climate resilience of, especially, Mediterranean cities.

The tool consists of the design under T3.2 and construction under T9.2 of bioswales as Sustainable Urban Drainage Systems (SUDS), specifically adapted to Mediterranean conditions and grounded in Nature-Based Solutions. These are bioretention swales composed of gravel, vegetated soil, and mulching layers, engineered to enhance infiltration and water purification through root development, without requiring irrigation beyond the contributions provided by urban runoff.

Their main functions include purification of stormwater through physical, chemical, and biological processes, and mitigation of the urban heat island effect through microclimatic regulation provided by vegetation.

Currently, three experimental bioswales are accessible for research activities within an open-air laboratory (Urban River Lab), along with one fully operational bioswale implemented in an urban area. After completion of the experimental phase, open datasets and design guidelines will be produced to support replication by municipalities, engineering firms, water management agencies, and urban planning teams. All materials will be published openly on the project’s dissemination platforms.

Primary users include:

  • Local and regional public administrations responsible for urban planning.
  • Professionals and companies in urban planning, civil engineering, landscape architecture, and water management.
  • Environmental institutions, water agencies, and organisations working on climate resilience.
  • Scientific and technical communities interested in Nature-Based Solutions.

The tool will provide empirical evidence and robust technical criteria to support the integration of efficient, climate-adapted bioswales in urban environments. It will enable users to select, size, and implement these solutions in an informed manner.

The experimental solution implemented at the URL has been monitored for five months using environmental parameters, and further experiments will be conducted in the coming weeks to assess purification performance through the application of a designed-rain recreating the same pollution conditions of the first-flush under controlled conditions.

Municipal authorities, urban planning practitioners, and water management teams have expressed strong interest in the replicability of the solution, particularly due to its potential to reduce diffuse pollution, improve environmental conditions in vulnerable urban areas, and increase surface permeability.