Anticipating Biological Succession in Rehabilitation of Long-Term Operated Nature_x0002_Based Solutions for Stormwater Treatment in Different Climate Zones – BioReStorm

Nature-based solutions (NBS) for stormwater treatment have been increasingly implemented in the last decades. As these systems are very flexible concerning size, design and adaptation to climatic zone, they have a huge potential for implementation in urban areas worldwide. Vegetation plays an important role for their technical functioning (water quality treatment, hydrology), aesthetic appearance, and other ecosystem services. However, over time, performance of these systems changes. Their maintenance is also often neglected. Initial plant species may be supplanted by others given the demanding growth conditions (prolonged drought alternating with flooding, pollutant accumulation, de-icing salts, nutrient scarcity). Over time, plant and associated microbial communities may diversify or become poorer. Consequently, the aesthetic appearance may conflict with the residents’ expectations. Pollutant accumulation in the filter substrate requires rehabilitation of the systems to restore performance and ecosystem services. However, only a few studies have looked at long term development, changing functionality and restoration measures. Few works have focused on citizen participation in NBS maintenance. In accordance with the objectives of the call, this proposal aims to document (i) evolution of plants and associated bacterial and fungal communities in vertical-flow stormwater NBS over time. (ii) It will assess the impact of plants and microorganisms on the hydraulic and treatment function. (iii) It will identify gaps in the design, implementation and maintenance of stormwater NBS affecting their performance. (iv) It will develop rehabilitation concepts for malfunctioning systems based on biological succession of plants and associated microorganisms beneficial for biodiversity. (v) Similarly, this research will assess the public’s perception of plant development in NBS that have been in operation for several years and the willingness of residents to participate in their maintenance. This project will contribute to a better understanding of societal attitudes and the various value systems surrounding NBS. Taking into account biological succession will enable to develop rehabilitation concepts beneficial for biodiversity, functionality and appearance. The results will be valuable for NBS operators and decision-makers. Indeed, relevant stakeholders will be mobilised throughout the project by a direct involvement in the different work packages. Three countries included in the consortium have long-term experience on the application of NBS for stormwater (Canada, France, Sweden), and one has recently started developing it (Estonia). The involved researchers are continuously contributing to the development of guidance documents and are therefore very aware of the importance of acting on decision-making for a successful societal transformation. BioReStorm offers multiple possibilities for knowledge transfer.