Attitudes of administrative decision-makers towards nature-based solutions for flood risk management in Germany

Over the last two decades, alternative and holistic concepts, such as Nature-based Solutions (NbS) were introduced and adopted by policy-makers, including to the field of flood protection, thereby causing a paradigm shift towards flood risk management. The inclusion of natural water retention measures (NWRM) such as dike relocation and floodplain restoration into the German guidelines for flood protection institutionalized the new concepts in Germany. Whereas small scale NbS and the affected population have already been subject to thorough scientific research, large-scale NbS and the decision-makers assigned with the measure’s implementation have yet to be studied. How do administrative decision-makers perceive the new approach and measures? Are there particular attitudes among the decision-makers regarding NbS? Which aspects of implementing large-scale NbS influence possible attitudes? Which hurdles do decision-makers concern for the implementation of the new concepts? This paper investigates these questions on the example of dike relocation and floodplain restoration using Q-methodology with administrative decision-makers of flood protection authorities in the German state of Saxony-Anhalt. The consecutive statistical analysis unveiled three significant viewpoints among the decision-makers. The viewpoints/attitudes were classified as 1. The Convinced, 2. The Concerned and, 3. The Evaluators, defined by varying and individual concerns on the implementation of dike relocation and floodplain restoration. Hereby, this study delivers insights on large-scale NbS as well as on the issues of their implementation.

Examples of Floodplain Restoration Evaluation Studies in the Danube River Basin

<p>Countries located in the Danube River Basin (DRB) are in danger of being affected by major catastrophic floods along the Danube and its tributaries. Floodplain restoration measures are among win-win nature-based solutions (NBS) for flood risk reduction but practitioners see their limitations in comparison to technical measures, when looking at their effectiveness and profitability. Within the framework of the EU Interreg Danube Floodplain project, this presentation shows the benefits of floodplain restoration in terms of monetized ecosystem services (ES). Our work focused on multiple ES groups for four study areas in the Danube catchment, located in Czech Republic, Romania, Serbia, and Slovenia. This was done with the help of stakeholder engagement, hydrodynamic models results, and the Toolkit for Ecosystem Service Site-Based Assessment (TESSA). Moreover, the approach was complemented with alternative methodologies (e.g. surveys on social media). Results show positive annual combined benefits of floodplain restoration measures, suggesting the helpfulness of evaluating these NBS through ES assessment. The work done will help increasing the knowledge on floodplain and their ES, and on how to rapidly evaluate them. Moreover, it will bring decision-makers further evidence in favor of floodplain restoration measures to be implemented for a general benefit of the communities.</p>

Invertebrate and Microbial Response to Hyporheic Restoration of an Urban Stream

All cities face complex challenges managing urban stormwater while also protecting urban water bodies. Green stormwater infrastructure and process-based restoration offer alternative strategies that prioritize watershed connectivity. We report on a new urban floodplain restoration technique being tested in the City of Seattle, USA: an engineered hyporheic zone. The hyporheic zone has long been an overlooked component in floodplain restoration. Yet this subsurface area offers enormous potential for stormwater amelioration and is a critical component of healthy streams. From 2014 to 2017, we measured hyporheic temperature, nutrients, and microbial and invertebrate communities at three paired stream reaches with and without hyporheic restoration. At two of the three pairs, water temperature was significantly lower at the restored reach, while dissolved organic carbon and microbial metabolism were higher. Hyporheic invertebrate density and taxa richness were significantly higher across all three restored reaches. These are some of the first quantified responses of hyporheic biological communities to restoration. Our results complement earlier reports of enhanced hydrologic and chemical functioning of the engineered hyporheic zone. Together, this research demonstrates that incorporation of hyporheic design elements in floodplain restoration can enhance temperature moderation, habitat diversity, contaminant filtration, and the biological health of urban streams.

Integrated Valuation of Nature-Based Solutions Using TESSA: Three Floodplain Restoration Studies in the Danube Catchment

Floodplain restoration measures are among the most well-known nature-based solutions for flood risk reduction but practitioners see their limitations in comparison to technical measures when considering both their effectiveness and profitability. The aim of this study is to show the co-benefits (besides flood risk reduction) of floodplain restoration and handle them in terms of monetized ecosystem services (ES). Our work focused on six ES groups for three study areas in the Danube catchment along the Krka, Morava, and Danube rivers. ES mapping through stakeholder engagement is also considered. We applied the methodologies suggested in the Toolkit for Ecosystem Service Site-Based Assessment (TESSA) complemented with alternative methodologies (e.g., questionnaires on social media). Results show annual combined benefits of floodplain restoration in a range from 237,000 USD2019 at Krka to 3.1 million USD2019 at Morava, suggesting the utility of ES assessment. The combination of stakeholder workshops and the TESSA guidelines, as well as the newly developed methods, were all central tools to provide decision-makers with arguments to use nature-based solutions for an integrated and holistic riparian land use management.