Enthusiasm for and investments in nature-based solutions (NBS) as sustainable strategies for climate adaptation and infrastructure development is building among governments, the scientific community, and engineering practitioners. This is particularly true for water security and water-related risks. In a freshwater context, NBS may provide much-needed “win-wins” for society and the environment that could benefit imperiled freshwater biodiversity. Such conservation benefits are urgently needed given the ongoing freshwater biodiversity crisis, with declines in freshwater species and their habitats occurring at more than twice the rate of marine or terrestrial systems. However, for NBS to make meaningful contributions to safeguarding freshwater biodiversity, clear links must be established between NBS applications and priorities for conservation. In this paper, we link common water-related NBS to six priority actions for freshwater life established by the conservation science n community, and highlight priority research and knowledge that will be necessary to bring NBS to bear on the freshwater biodiversity crisis. In particular, we illustrate how NBS can play a direct role in restoring degraded aquatic and floodplain ecosystems, enhancing in-stream water quality, and improving hydrological connectivity among freshwater ecosystems. System-level monitoring is needed to ensure that freshwater NBS deliver on their promised benefits for ecosystems and species.

Nature-based solutions (NbS) leverage the power of ecosystems and biodiversity to address societal challenges. NbS for addressing water security challenges in cities are widely recognized for accelerating sustainability and delivering multiple co-benefits. However, peer-reviewed studies and implementation guidance have primarily focused on the Global North, necessitating adaptation for the Global South. While NbS could provide environmental and socio-economic benefits, the specific adaptations required for planning, designing, and implementing in the context of the Global South remain unclear. During the 6th Symposium on Urbanization and Stream Ecology (SUSE 6) held in Brisbane, Australia, in May 2023, a group of interdisciplinary experts discussed these challenges. This was followed by in-depth discussions with additional experts spanning various sectors across the Global South and a comprehensive literature review. This paper presents the outcomes of these efforts specifically focused on three objectives: understanding the NbS planning context in the Global South, identifying unique challenges for implementing NbS in these regions, and identifying “bright spots” as learning opportunities for implementation. We outline the contextual differences between the Global North and Global South in the context of water security and NbS, and then the challenges and opportunities to mainstream urban water NbS in the Global South are discussed across four thematic categories: environmental; socio-economic and perceptional; capacity, knowledge and expertise; and management and governance. We highlight select bright spots to foster a broader understanding of ongoing efforts in the Global South. Ultimately, we seek to highlight opportunities for more efficient and socially-just pathways for adoption of NbS to address urban water security in the Global South. We also recommend practical steps such as capacity building in NbS design and implementation, development of best practices and support tools, monitoring of outcomes, consideration of other effective area-based conservation measures (OECM) as NbS and building partnerships for all of these with stakeholders.

Computer model simulations were conducted of an existing parking lot with pervious concrete low-impact development (LID) controls using the U.S. EPA Storm Water Management Model (SWMM). For three different types of storms, simulations were performed using a range of pervious concrete pavement area coverages and infiltration rates to assess the effects of these variables on runoff volume. Field measurements of in-place pervious concrete infiltration rates averaged $45\mathrm{mm}/\mathrm{h}$ , suggesting that the pervious concrete was not performing as an effective LID control. The modeling results show that increasing the area of pervious concrete pavement coverage by 30% reduced the volume of runoff by 21–45%, depending on the intensity of the rainfall. However, the same volume of runoff could be reduced by maintaining the desired infiltration rate of the original coverage of pervious concrete pavement. Overall, results illustrate the effectiveness of maintaining high infiltration rates in well-constructed, small, pervious pavement areas in contrast with poorly maintained pervious pavement covering large areas.

Urban watersheds undergo significant ecological change due to increased imperviousness, flashy hydrologic processes, channel evolution, the loss of riparian zones, and the fragmentation of movement corridors. Watershed restoration seeks to address these challenges simultaneously through site-scale actions coordinated at the basin scale. Ecological benefits, social outcomes, and monetary costs represent common metrics to inform decision-making on these programs. However, decision-making at the site and watershed scale may differ, and the accuracy and resolution of benefit and cost data should vary as project needs dictate. This paper presents a case study of urban stream restoration in Utoy Creek, Atlanta, Georgia, USA, where multiple partner organizations are planning a portfolio of stream restoration projects. Analyses were conducted to assess ecological benefits, social outcomes, and monetary costs at the watershed scale to inform site selection, at the site scale to guide restoration design, and then again at the watershed scale to identify an effective portfolio of sites. These scales each presented unique technical challenges and required the adaptation of analytical methods to suit decision-making needs. This case study is not presented as a comprehensive approach applicable in all urban systems, but instead a template for urban restoration practitioners to adapt to their unique watershed and planning contexts.

The change of natural pervious surfaces into impervious surfaces due to urbanization, construction, and development causes excess stormwater runo |