Total water levels (TWL) – the combination of wave-runup, tides, surges and in the future, sea-level rise – stand as a critical variable contributing to coastal inundation during storms. Quantifying the contribution of wave runup to extreme TWL is essential for accurate assessments of coastal inundation risk at wave-dominated coastlines. Despite decades of research, a fundamental challenge for coastal practitioners is selecting from numerous runup models, often constrained by the unavailable site-specific beach slope data. This study presents a novel dataset of TWL observations inferred from marine debris deposits surveyed immediately after storms in New South Wales, Australia. Using this dataset, this work assesses the accuracy of simplified TWL models integrating still water levels, local nearshore wave data, various runup formulae and different beach slope proxies derived from remote sensing technologies. Models utilising historical beach slopes from LiDAR outperformed the models using satellite-derived slopes. Findings suggest that runup formulae calibrated during small-to-moderate wave conditions can be extrapolated to extreme storms when applied to similar sites, emphasising the preference for site-specific formulae over one-model-fits-all approaches. Challenges and opportunities of modelling TWL for coastal inundation assessments are discussed, highlighting the need to incorporate beach slope uncertainties to fully assess inundation impacts as sea-levels rise.

Coastal areas that are characterized by coastal squeeze are highly vulnerable to the contemporary threats of climate change, sea level rise and biodiversity loss. Innovative coastal adaptation policies are necessary to accommodate these threats and have become salient issues on the agendas of mandated decision-makers on a global scale. This article provides a perspective on how historical–geomorphological knowledge can be integrated as an evidence base for coastal adaptation in such vulnerable zones when re-thinking and re-designing coastal adaptation policies. Our historical–geomorphological perspective proposes that we explicitly need to account for the geological, natural extent of human-modified and squeezed areas to fully understand their present-day developments. The geo-historical extent provides information on the long-term development of sedimentary structures and the functioning of coastal systems, and evaluates their effects on coastal protection, conservation and necessary adaptation. We use the Wadden Sea coastal zone as a case study to illustrate the necessity of the development of a geo-historical perspective and operationalize its integration into contemporary decision-making. The North European Wadden Sea is the largest continuous region of intertidal sand and mud flats in the world, and was recognized for its outstanding universal value by UNESCO in 2009. Nonetheless, it is an area that suffers intensely from coastal squeeze and has lost 70–80% of its coastal zone due to land reclamation and dike building. In short, our geo-historical perspective demands: (i) geo-historical risk assessment of coastal areas, (ii) geomorphological modelling that links the historical-induced risk to contemporary dynamics, (iii) assessment of ecological and societal values that are capable of estimating trade-offs between different coastal adaptation options in the contemporary system, (iv) evaluation of feasibility and legitimacy of potential coastal adaptation on the local scale of coastal inhabitants and (v) applying a transdisciplinary process that enables effective knowledge co-production between science and societal stakeholders.

Coastal communities face increasing risks from sea level rise, erosion, flooding and growing pressure on coastal land and resources. Addressing these challenges requires research that connects technical, environmental, social, creative and governance outlooks. In this perspective article, we reflect on how interdisciplinary coastal research can be achieved and better supported, drawing on selected literature and our own experiences from European and US coastal engineering research contexts. We argue that meaningful interdisciplinary collaboration depends on both profound disciplinary expertise and reciprocal learning across disciplinary boundaries. To support this discussion, we introduce two new concepts. The hook-shaped researcher illustrates how researchers from different disciplines can jointly develop an interdisciplinary research space through partial but mutual knowledge exchange. The interdisciplinary bridge model highlights the need for meaningful, challenging and relevant collaboration across all disciplines involved. We identify time, trust, strong relationships, distributed leadership and supportive institutional structures as central conditions for successful interdisciplinary work. We also discuss how funding schemes, publication practices and academic reward systems can better recognize and enable interdisciplinary collaboration. Strengthening these conditions can improve coastal adaptation research and support sustainable responses to complex coastal challenges.

Convergent, co-produced coastal research engages researchers across disciplines and brings together researchers, practitioners and community representatives to co-create new knowledge and understanding to support community resilience while advancing scientific understanding. This type of research is increasingly required by funding agencies and yet it is relatively new. Given this, along with the expansive range of scholarly and lived expertise required to carry out this type of research, there are many epistemological, relational, temporal and institutional challenges for successful projects to overcome. Here we describe these challenges, along with strategies employed to overcome them, based on the work of multiple convergent, co-production research projects focused on coastal communities and environments, funded by the National Science Foundation’s Coastlines and People (CoPe) Program. Our experience leads us to recommend that project leaders use inclusive communication practices; incorporate boundary spanners; build shared understanding; select the style and depth of co-production intentionally; focus on earning trust; tailor co-production approaches to the communities involved; equalize power dynamics; embrace and acknowledge the expanded timeline required; plan for delays; embrace flexibility; and build and sustain partnerships for the long haul. Additionally, supporting this type of work requires academic institutions to reward and value the best research practices and research products that emerge from convergent, community-engaged research, including revision of promotion and tenure guidelines to accommodate the expanded timelines required, and the different types of outcomes and products arising from these types of efforts. Further, we recommend that funders consider offering staged, progressive funding opportunities and longer funding timeframes, in recognition of the time it takes to build and sustain meaningful, trusting community partnerships and to plan research projects in a deeply collaborative way with community partners.

The ecological and socio-economic services that deltas provide are central to regional infrastructure, sustainable development and climate-change adaptation strategies. Approximately 45% of the global deltaic population resides within South and Southeast Asian mega-deltas. The two principal Vietnamese deltas (Mekong and Song Hong/Red River) account for almost half of that total and have been the subject to sedimentological, hydrogeological and seismic research. However, some inconsistencies remain. Analysis of tidal notches provides an independent, complementary dataset for studying relative sea-level change and associated processes. We present a Late Pleistocene–Late Holocene inundation chronology for the Red River Delta. Pleistocene dates (52–29 cal. kBP) are cautiously attributed to late phases of the Vinh Phuc transgression. Periods of sea-level stabilisation are confirmed leading up to, during and after the Dong Da/Flandrian transgression (6–4 cal. kBP). Results highlight the complexity of past sea-level change in tropical deltaic settings and the value of palaeoecological records to capture sea-level dynamics outside the reach of modern instrumentation. Potential linkage between relative sea level and variability in the strength of the Asian Summer Monsoon/El Niño-La Niña system is posited. Coupling of sea-level regression to climate conditions during the 4.2 and 2.8 ka Cold Events in particular warrants further investigation.

Reef passages are ecologically, socio-economically and culturally important habitats in Pacific Island Countries (PICs), yet remain poorly understudied and inadequately documented. We developed and deployed an adapted, low-cost, adjustable, suspended, baited remote underwater video (suspended-BRUV) system, specifically designed to monitor marine species diversity across three reef passages around Ovalau in Fiji, in the southwest Pacific. The suspended-BRUV deployment protocol and design were guided by local ecological knowledge and expertise from local fishers. A total of 36 deployments were conducted across three barrier reef passages, yielding 31 valid videos from which 1,001 individuals representing 60 species across 18 families were identified. Individuals cross-referenced with the IUCN Red List of Threatened Species revealed that two Critically Endangered, three Endangered, four Vulnerable and one Near-Threatened species were observed, demonstrating the effectiveness of this suspended-BRUV system in documenting conservation-relevant taxa. The system’s application demonstrated a strong potential as an effective tool for improving fisher-led biodiversity monitoring, even in highly dynamic environments such as reef passages, while also supporting community engagement, knowledge sharing and informing local management and conservation efforts. This study contributes to highlighting the importance of reef passages as biodiversity hotspots and encourages the need for inclusive, contextualized monitoring of coastal ecosystems.