Fostering Transdisciplinary Nature-Based Solutions in River Basin Governance: Towards Socio-Eco-Hydro Permitting for water sensitive systems

Transdisciplinarity is essential to achieve the climate action, circular and green economy objectives. Safety and healthy water, land, soils, citizens and communities are governed by inter-linked dynamics associated to societal actions and eco-hydrological processes and resources. Scientific evidence has proven that humans are at the same time the major cause and remediation means to tackle increasing climate stressors and impacts. While the importance of working with and for nature is seldom understood, the operational uptake of Nature-based Solutions (NBS) is still limited. This research examines the current state of knowledge, practice and legislation that guides, or hinders, the implementation of green economy water management measures, while proposing a framework to advance their technological and policy implementations. This work was conducted analysing policy and technical regulations derived primarily from the European Water Framework and Flood directives and further extended to all norms pertaining to river basin and water management from the European to the regional scale, using the river basin as main technical and administrative reference unit. Over 150 documents were revised, including EU directives, national technical reports, peer-reviewed articles, and international standards, followed by the implementation of a biophysical risk assessment framework linking hydro-meteorological hazard domains to NBS functional typologies for water sensitive design. This methodology led to the creation of a catalogue of 42 NBS (see in the Supplementary, S1) sourced from five operational domains (hydromorphological, agricultural, forest and silvicultural, urban, and fluvial-coastal) and connected each measure to both biophysical processes and applicable regulatory instruments. Indeed, a further contribution of this research is the alignment of the NBS catalogue within eco-green permitting frameworks. This work promotes, thus, the link of NBS domain and target of applications with existing socio-eco-hydrological standards reversing NBS-related permitting, certification and standards role - from barrier to means - for the adoption of green management strategies and interventions at the river basin scale. A novel conceptual framework is designed and proposed that is able to synergetically combine hazard assessment, operational domains, available measures, normative frameworks, and the permitting process into a scalable tool for NBS implementation by river basin authorities, public administrations, and non-specialist actors. This marks a shift from a static NBS catalogue of solutions towards a novel integrated NBS solution-driven permitting and certification standards. This research aims, thus, to implement NBS actions by means of a dynamic, hazard-specific, and objective-oriented decision tool, enabling also the integration of grey-green hybrid solutions within existing river basin governance. This manuscript also describes an operational NBS workflow fostering river basin-scale socio-eco-hydrological certification to close the gap between scientific knowledge, regulatory compliance, and sustainable infrastructure implementation while embracing green circular and climate action principles and strategies.