Sea level rise (SLR) poses a hazard to ecosystems and economies in low-lying coastal and estuarine areas. To better understand the potential impacts of SLR in estuaries, a comprehensive review of existing theory, literature, and assessment tools is undertaken. In addition, several conceptual models are introduced to assist in understanding interlinked estuarine processes and their complex responses to SLR. This review indicates that SLR impacts in estuaries should not be assessed via static (bathtub) approaches as they fail to consider important hydrodynamic effects such as tidal wave amplification, dampening, and reflection. Where hydrodynamic models are used, the existing literature provides a relatively detailed understanding of how SLR will affect estuarine hydrodynamics (e.g., tides and inundation regimes). With regards to the current understanding of, and ability to model, the connections between altered hydrodynamics (under SLR) and dependent geomorphic, ecological, and bio-geochemical processes, significant knowledge gaps remain. This is of particular concern as there is currently a paradigm shift towards more integrated and holistic management of estuaries. Estuarine management under accelerating SLR is likely to become increasingly complex, as decision-making will be undertaken with uncertainty. As such, this review highlights that there is a fundamental requirement for more sophisticated and interdisciplinary studies that integrate physical, ecological, bio-geochemical, and geomorphic responses of estuaries to SLR.

Nature-based Solutions are recognised for their potential to address the biodiversity and climate crises, and less extensively, other societal challenges. However, this nature-society relationship is becoming more important as available food and water resources, income, and human health, are increasingly impacted by environmental changes. Here, we utilise the seven major societal challenges addressed by Nature-based Solutions according to the International Union for Conservation of Nature, to identify the primary themes of the Nature-based Solutions research landscape from 1990-2021. We evaluate how these themes, with respect to the societal challenges, evolved over time, and where. Our findings highlight the under-representation of four societal challenges across the research landscape: economic and social development, human health, food security, and water security. We propose six research pathways to advance the evidence for Nature-based Solutions in these societal challenges, and present opportunities for future research programs to prioritise the needs of society, the environment, and the economy.

Although most stepped spillway–design guidelines were developed for uniform step heights, a nonuniform stepped design might be a practical alternative in some cases. A physical study was conducted in a moderate slope-stepped chute (1V:2H) and five stepped configurations were tested for $0.7<d_c/h<1.9$ . Detailed air-water flow measurements were performed for each configuration and the results were compared in terms of flow patterns, energy dissipation, and flow resistance. The basic findings showed minor differences between all configurations and indicated that the rate of energy dissipation was about the same for uniform and nonuniform stepped configurations. But the observations suggested that the nonuniform stepped configurations might induce some flow instabilities for smaller flow rates.