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1. Compound coastal flooding in San Francisco Bay under climate change

   https://doi.org/10.1038/s44304-024-00057-0  

   Wang, Zhenqiang; Leung, Meredith; Mukhopadhyay, Sudarshana; Sunkara, Sai_Veena; Steinschneider, Scott; Herman, Jonathan; Abellera, Marriah; Kucharski, John; Ruggiero, Peter (January 2025, npj Natural Hazards)

   Abstract The risk of compound coastal flooding in the San Francisco Bay Area is increasing due to climate change yet remains relatively underexplored. Using a novel hybrid statistical-dynamical downscaling approach, this study investigates the impacts of climate change induced sea-level rise and higher river discharge on the magnitude and frequency of flooding events as well as the relative importance of various forcing drivers to compound flooding within the Bay. Results reveal that rare occurrences of flooding under the present-day climate are projected to occur once every few hundred years under climate change with relatively low sea-level rise (0.5 m) but would become annual events under climate change with high sea-level rise (1.0 to 1.5 m). Results also show that extreme water levels that are presently dominated by tides will be dominated by sea-level rise in most locations of the Bay in the future. The dominance of river discharge to the non-tidal and non-sea-level rise driven water level signal in the North Bay is expected to extend ~15 km further seaward under extreme climate change. These findings are critical for informing climate adaptation and coastal resilience planning in San Francisco Bay. 

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2. Projecting Future Chronic Coastal Hazard Impacts, Hotspots, and Uncertainty at Regional Scale

   https://doi.org/10.22541/essoar.169711756.69292862/v1  

   Leung, Meredith C; Cagigal, Laura; Méndez, Fernando J; Ruggiero, Peter (October 2023, Authorea, Inc.)

   While there is high certainty that chronic coastal hazards like floodingand erosion, are increasing due to climate change induced sea-levelrise, there is high uncertainty surrounding the timing, intensity, andlocation of future hazard impacts. Assessments that quantify theseaspects of future hazards are critical for adaptation planning under achanging climate and can reveal new insights into the drivers of coastalhazards. In particular, probabilistic simulations of future hazardimpacts can improve these assessments by explicitly quantifyinguncertainty and by better simulating dependence structures between thecomplex multivariate drivers of hazards. In this study, a regional-scaleprobabilistic assessment of climate change induced coastal hazards isconducted for the Cascadia region, USA during the 21st century. Threeco-produced hazard proxies for beach safety, erosion, and flooding arequantified to identify areas of high hazard impacts and determine hazarduncertainty under three sea-level rise scenarios. A novel chroniccoastal hazard hotspot indicator is introduced that identifies areasthat may experience significant increases in hazard impacts compared topresent day conditions. We find that Southern Cascadia and NorthernWashington have larger hazard impacts and hazard uncertainty due totheir morphologic setting. Erosional hazards, relative to beach safetyand coastal flooding, will increase the most in Cascadia during the 21stcentury under all sea-level rise scenarios. Finally, we find that hazarduncertainty associated with wave and water level variability exceeds theuncertainty associated with sea-level-rise until the end of the century. 

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3. Breaking down annual and tropical cyclone-induced nonlinear interactions in total water levels

   Sakib, M S; Muñoz, D F; Wahl, T (December 2025, Advances in water resources)

   With the increase of tropical cyclone activity, coastal communities will experience growing impacts from extreme water levels and associated compound flooding. Multiple drivers contribute to total water level (TWL), including mean sea level, astronomical tides, riverine flow, storm surges, and waves. Therefore, gaining insight into future TWL variability requires a thorough understanding of how those drivers nonlinearly interact at different spatiotemporal scales. In this study, we developed a coupled coastal and wave model at sufficient spatial resolution to analyze: (i) tide–driver interactions and their nonlinear components stemming from surge, river flow, and wind-waves, and (ii) their spatiotemporal evolution across the pre-landfall, landfall, and post-landfall stages of tropical cyclones in the Chesapeake Bay, USA. Results show that tide–surge and tide–wave interactions, along with their nonlinear components, exhibit substantial annual variability, with extreme hurricanes producing abrupt and spatially distinct responses driven by low pressure anomalies in slow-moving storms and wind setup in faster systems. In contrast, tide–river interactions remain negligible except in the upper bay tributaries. A weak or neutral tide–driver interaction does not necessarily indicate a negligible nonlinear response. Rather, nonlinear interactions (NIs) generally act out of phase with their associated drivers, functioning as compensatory mechanisms that amplify or suppress TWL. These nonlinearities are transient and of high-frequency nature near the coast, but evolve into slower, more persistent fluctuations in upstream regions. As climate change reshapes coastal dynamics, a robust understanding of NIs is essential for designing effective flood protection, enhancing risk assessments, and developing informed adaptation strategies for extreme water levels. 

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4. Economic damages from Hurricane Sandy attributable to sea level rise caused by anthropogenic climate change

   https://doi.org/10.1038/s41467-021-22838-1  

   Strauss, Benjamin H.; Orton, Philip M.; Bittermann, Klaus; Buchanan, Maya K.; Gilford, Daniel M.; Kopp, Robert E.; Kulp, Scott; Massey, Chris; Moel, Hans de; Vinogradov, Sergey (May 2021, Nature Communications)

   Abstract In 2012, Hurricane Sandy hit the East Coast of the United States, creating widespread coastal flooding and over $60 billion in reported economic damage. The potential influence of climate change on the storm itself has been debated, but sea level rise driven by anthropogenic climate change more clearly contributed to damages. To quantify this effect, here we simulate water levels and damage both as they occurred and as they would have occurred across a range of lower sea levels corresponding to different estimates of attributable sea level rise. We find that approximately $8.1B ($4.7B–$14.0B, 5th–95th percentiles) of Sandy’s damages are attributable to climate-mediated anthropogenic sea level rise, as is extension of the flood area to affect 71 (40–131) thousand additional people. The same general approach demonstrated here may be applied to impact assessments for other past and future coastal storms. 

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5. Shifting Sources and Fates of Carbon With Increasing Hydrologic Presses and Pulses in Coastal Wetlands

   https://doi.org/10.1029/2023JG007903  

   Anderson, Kenneth_J; Kominoski, John_S; Osburn, Christopher_L; Smith, Matthew_A (June 2024, Journal of Geophysical Research: Biogeosciences)

   Abstract Coastal ecosystems are rapidly shifting due to changes in hydrologic presses (e.g., sea‐level rise) and pulses (e.g., seasonal hydrology, disturbances, and restoration of degraded wetlands). Changing water levels and sources are master variables in coastal wetlands that can alter carbon concentrations, sources, processing, and export. Yet, how long‐term increases in water levels from marine and freshwater sources influence dissolved organic carbon (DOC) concentrations and dissolved organic matter (DOM) composition is uncertain. We quantified how long‐term changes in water levels are affecting DOC concentration (2001–2021) and DOM composition (2011–2021) differently across the Florida Everglades. DOC concentrations decreased with high water depths in peat marshes and increased with high water levels in marl marshes and across mangroves, and these relationships were reproduced in freshwater peat marshes and shrub mangroves. In the highly productive riverine mangroves, cross‐wavelet analysis highlighted variable relationships between DOC and water level were largely modulated by hurricane disturbances. By comparing relationships between water level and DOC concentrations with carbon sources from DOM fluorescence indices, we found that changing water sources between the dry and wet season shift DOM from algal to detrital sources in freshwater marshes, from detrital marsh to detrital mangrove sources in the brackish water ecotone, and from detrital mangrove to algal marine sources in downstream mangroves. As climate change and anthropogenic drivers continue to alter water levels in coastal wetlands, integrating spatial and temporal measurements of DOC concentrations and DOM compositions is essential to better constrain the transformation and export of carbon across these coastal ecosystems. 

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