An analysis of the understanding of maintenance of nature-based solutions for urban stormwater management

Abstract: Urban stormwater management is necessary to protect human life and society from the dangers and damages associated with flooding from extreme weather events. Conventional measures of stormwater management utilise grey infrastructure to convey runoff away from urban areas, but due to increasing urbanization, aging of urban infrastructure, climatic variability, and flooding due to extreme weather events, these measures are often no longer sufficient. On the other hand, sustainable stormwater management systems, such as nature-based solutions, involve working with ecosystems in order to improve resilience and adaptability in a changing climate, while simultaneously providing other benefits to biodiversity, pollution control, and human health.  While academic interest in sustainable systems, and the transition from conventional measures in urban areas, is growing, there remains significant uncertainty surrounding the maintenance of these systems. To investigate the maintenance requirements, how it impacts the transition, and how to reduce this uncertainty, a comprehensive literature review was undertaken, analysing 70 texts on the subjects of urban stormwater management, nature-based solutions, and maintenance.  The findings indicate a variety in terminology and concepts used to describe sustainable systems, causing confusion, and resulting in fragmentation of the body of knowledge of them. Data on maintenance activities, frequencies, and costs for both conventional and sustainable systems were compiled. Major barriers discovered include unclear management responsibilities, lack of expertise, misconceptions regarding maintenance demands, uncertainty in long-term costs and performance, and a lack of policy and governance instruments.  Collaboration and education will be vital to expanding the transition to sustainable stormwater management. Incorporating maintenance and stakeholder involvement throughout the planning process will reduce the uncertainty involved in the implementation of nature-based solutions. Large-scale and in- depth monitoring and reporting programs will provide evidence in performance and lifespan and reduce uncertainty further. Educating decision-makers and the public alike on the efficacy and benefits of nature- based solutions will lead to wider acceptance. Strong regulatory and governance frameworks will foster widespread uptake, encouraging the transition from conventional to sustainable urban stormwater management.