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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. 

Abstract Storm surge events are a key driver of widespread flooding, particularly when combined with astronomical tides superimposed on mean sea level (MSL). Coastal storms exhibit seasonal variability which translates into a seasonal cycle in storm surge activity. Understanding changes in the seasonal storm surge cycle is critical as both changes in the amplitude and the phase may alter the flood potential, especially when compounded with changes in the MSL cycle. Here, a comprehensive analysis of the storm surge seasonal cycle and its links to the MSL seasonal cycle is performed using tide gauge observations from a quasi‐global data set. Harmonic analysis is used to assess the mean and changing storm surge seasonal cycles over time. Extreme value analysis is applied to explore the effect of seasonal changes on storm surge return levels. We also quantify the influence of large‐scale climate modes, and we compare how the seasonality of storm surge and MSL have changed relative to each other. The peak of the storm surge cycle typically occurs during winter for tide gauges outside of tropical cyclone regions, where there is also greater variability in the phase of the storm surge cycle. The timing of the peak varied by more than a month at 21% of the tide gauges analyzed. The MSL and storm surge cycles peaked at least once within 30 days over the historic records at 74% of tide gauges. 

Abstract Dry and wet extremes (i.e., droughts and floods) are the costliest hydrologic hazards for infrastructure and socio-environmental systems. Being closely interconnected and interdependent extremes of the same hydrological cycle, they often occur in close succession with the potential to exacerbate hydrologic risks. However, traditionally this is ignored and both hazards are considered separately in hydrologic risk assessments; this can lead to an underestimation of critical infrastructure risks (e.g., dams, levees, dikes, and reservoirs). Here, we identify and characterize consecutive dry and wet extreme (CDW) events using the Standardized Precipitation Evapotranspiration Index, assess their multi-hazard hydrologic risks employing copula models, and investigate teleconnections with large-scale climate variability. We identify hotspots of CDW events in North America, Europe, and Australia where the total numbers of CDW events range from 20 to 30 from 1901 to 2015. Decreasing trends in recovery time (i.e., time between termination of dry extreme and onset of wet extreme) and increasing trends in dry and wet extreme severities reveal the intensification of CDW events over time. We quantify that the joint exceedance probabilities of dry and wet extreme severities equivalent to 50-year and 100-year univariate return periods increase by several folds (up to 20 and 54 for 50-year and 100-year return periods, respectively) when CDW events and their associated dependence are considered compared to their independent and isolated counterparts. We find teleconnections between CDW and Niño3.4; at least 80% of the CDW events are causally linked to Niño3.4 at 50% of the grid locations across the hotspot regions. This study advances the understanding of multi-hazard hydrologic risks from CDW events and the presented results can aid more robust planning and decision-making. 

Abstract Little is known about the effect of tidal changes on minor flooding in most lagoonal estuaries, often due to a paucity of historical records that predate landscape changes. In this contribution, we recover and apply archival tidal range data to show that the mean tidal range in Miami, Florida, has almost doubled since 1900, from 0.32 to 0.61 m today. A likely cause is the dredging of a ∼15 m deep, 150 m wide harbor entrance channel beginning in the early 20th century, which changed northern Biscayne Bay from a choked inlet system to one with a tidal range close to coastal conditions. To investigate the implications for high‐tide flooding, we develop and validate a tidal‐inference based methodology that leverages estimates of pre‐1900 tidal range to obtain historical tidal predictions and constituents. Next, water level predictions that represent historical and modern water level variations are projected forward in time using different sea level rise scenarios. Results show that the historical increase in tidal range hastened the occurrence of present‐day flooding, and that the total integrated number of days with high‐tide floods in the 2020–2100 period will be approximately O(10³) more under present day tides compared to pre‐development conditions. These results suggest that tidal change may be a previously under‐appreciated factor in the increasing prevalence of high‐tide flooding in lagoonal estuaries, and our methods open the door to improving our understanding of other heavily‐altered systems.