Mainstreaming Nature-Based Solutions in Torrential Landscapes: Establishing Demonstration Sites in Austria and Slovenia

Torrential landscapes, characterized by steep slopes, confined channels, and rapid runoff, are increasingly susceptible to climate-driven hazards triggered by heavy precipitation. The resulting fluvial and pluvial floods, debris flows, and associated erosional processes pose a risk to infrastructure and communities in surrounding and in downstream areas. While historical evidence supports the use of nature-based solutions (NbS) in these environments, they support alternative and/or complementary investments to grey infrastructure. However, there is a significant lack of robust, long-term data regarding their effectiveness in the complex alpine terrain. Within the scope of the NATURE-DEMO project, this gap is addressed by investigating the potential of NbS to mitigate climate risks through real-world demonstration sites in Austria and Slovenia.

The project establishes two distinct demonstration sites within torrential landscapes located in Austria and Slovenia, addressing conflicting socio-economic, ecological and technical contexts. In Slovenia, the Gradaščica River site demonstrates NbS implementation in semi-urban and urban contexts within Ljubljana. This site focuses on large-scale river restoration, including channel widening and the creation of buffer zones, to protect over 17,000 inhabitants from recurrent flooding. In contrast, in Austria at the Brunntal Valley the focus is on facilitating sedimentation within the valley floor and mitigate erosional processes to safeguard aquifers that serve as a strategic drinking water supply for the city of Vienna. Given that stringent environmental regulations in this water protection zone largely prohibit conventional grey infrastructure and the application of NbS is preferable.

To gather empirical evidence on NbS functionality, the project employs advanced monitoring strategies. These include UAV-LiDAR and UAV-Photogrammetry to track geomorphological changes and sediment dynamics, alongside traditional hydrological gauging. Preliminary results from the planning and establishment phase highlight the challenges of technical approval and the necessity of stakeholder engagement in mainstreaming green solutions and shifting the paradigm from purely technical engineering to resilient, hybrid landscape management. This results in a multitude of ecological and socio-economic co-benefits that support climate resilience of water infrastructures. Thus, this contribution presents the establishment of torrential landscape demonstration sites and the monitoring strategies used to gather evidence on NbS functioning, along with preliminary results obtained during the planning and establishment phase.

 

Acknowledgements: The authors would like to acknowledge the financial support provided by the European Union’s Horizon Europe Research and Innovation Programme, within the scope of the project “NATURE-DEMO: Nature-Based Solutions for Climate-Resilient Infrastructure” (Grant agreement No. 101157448). The study was also partially financed by the Slovenian Research and Innovation Agency (ARIS) within the research program P2–0180. The research is also supported by the UNESCO Chair on Water-related Disaster Risk Reduction and the Slovenian national committee of the IHP UNESCO research programme.