A robust multi-functional decision support system for widespread planning of nature-based solutions (NBSs) must incorporate components of social equity. NBS systems advance social well-being through enhanced levels of greenspace, which have been shown to improve physical health (e.g., heart disease, diabetes), mental health (e.g., post-traumatic stress disorder, depression), and socio-economics (e.g., property values, aesthetics, recreation). However, current optimization frameworks for NBSs rely on stormwater quantity abatement and, to a lesser extent, economic costs and environmental pollutant mitigation. Therefore, the objective of this study is to explore how strategic management strategies associated with NBS planning may be improved, while considering the tripartite interactions between hydrological, environmental, and societal conditions. Here, a large-scale NBS watershed was calibrated to local conditions using standard hydro-environmental modeling (i.e., EPA’s SWMM) and optimized on the basis of stormwater abatement, pollutant load reduction, and economic efficiency. The spatial allocation of possible NBS features was integrated with properties of social equity through a novel framework involving the Area Deprivation Index (ADI) and a composite Gini coefficient. By embedding social equity into the fabric of the NBS planning process, we provide an opportunity for improving social justice and spurring further community buy-in toward a balanced system. This study demonstrates how the optimal spatial placement of NBSs is location-dependent according to both the physical and human properties of the watershed.

We describe a sampling of over two-dozen sociohydrology case studies that advance our understanding of two-way human-water phenomena. These case studies span broad geographic regions, including over 20 countries, and cover cross-cutting themes such as human behavior, social equity, water security, migration, water resources management, and ecological and environmental phenomena. Collectively, the cases reflect progress within the Panta Rhei decade and suggest new pathways for exciting research in the coming era, in particular by showing how socio-hydrologic modes of study transcend many geographical bounds. We synthesize these insights and describe approaches toward innovative modeling and predictive frameworks that promise to assist in real-world decision-making. We further describe how understanding of diverse and pertinent socio-hydrological phenomena relate to the United Nations’ Sustainable Development Goals (UNSDG) and Environment Programme (UNEP) for addressing climate action in a manner that manifests social well-being and resilient communities.

Urbanization and climate change increase water pressure in dams and stress the stability of flood-control structures. Many of the existing dams are aging and have been classified as deficient or having potential for life-threatening hazards in the event of failure. Common mitigation measures include optimizing reservoir release rates and/or implementing additional large—scale infrastructure. Such decisions are typically investigated with drainage models that do not consider co-evolving variables, such as environmental effects or socio-economic impacts. Flood-control reservoirs form complex hydrologic systems that contain numerous interdependencies and intricate feedbacks that must be balanced to achieve optimal resiliency. A spatial multicriteria analysis (SMCA) framework is presented that integrates a suite of social and environmental vulnerabilities with reservoir modeling and decision-making weights. An implementation of adaptive flood control case study of the Addicks and Barker Reservoirs in Houston, Texas, USA during Hurricane Harvey is used to illustrate the proposed technique and to highlight the complexities involved in reservoir decision-making. Hydrologic synergies that would be realized from maintaining status quo operations, optimizing reservoir releases, or increasing storage capacity through engineered solutions are explored. The SMCA methodology is used to visualize how such relationships alter environmental and social vulnerabilities for improved decision-making. In this way, the decision-making process becomes an endogenous component of the integrated human-water-environment feedbacks, thus enabling adaptive management of flood-control reservoirs with comprehensive risk.