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1. Estuarine and coastal natural hazards: An introduction and synthesis

   https://doi.org/10.1016/j.ecss.2020.106654  

   Veeramony, Jay ; Li, Chunyan ; Sheremet, Alex ; Myers, Edward P. ; Xia, Meng ; Mitchell, Steve ( January 2020 , Estuarine coastal and shelf science)

   Two sessions were organized during the 2018 Fall AGU Meeting entitled, (1) Coastal Response to Extreme Events: Fidelity of Model Predictions of Surge, Inundation, and Morphodynamics and (2) Improved Observational and Modeling Skills to Understand the Hurricane and Winter Storm Induced Surge and Meteotsunami. The focus of these sessions was on examining the impact of natural disasters on estuarine and coastal regions worldwide, including the islands and mainland in the northwestern Atlantic and the northwestern Pacific. The key research interests are the investigations on the regional dynamics of storm surges, coastal inundations, waves, tides, currents, sea surface temperatures, storm inundations and coastal morphology using both numerical models and observations during tropical and extratropical cyclones. This Special Issue (SI) ‘Estuarine and coastal natural hazards’ in Estuarine Coastal and Shelf Science is an outcome of the talks presented at these two sessions. Five themes are considered (effects of storms of wave dynamics; tide and storm surge simulations; wave-current interaction during typhoons; wave effects on storm surges and hydrodynamics; hydrodynamic and morphodynamic responses to typhoons), arguably reflecting areas of greatest interest to researchers and policy makers. This synopsis of the articles published in the SI allows us to obtain a better understanding ofmore »the dynamics of natural hazards (e.g., storm surges, extreme waves, and storm induced inundation) from various physical aspects. The discussion in the SI explores future dimensions to comprehend numerical models with fully coupled windwave- current-morphology interactions at high spatial resolutions in the nearshore and surf zone during extreme wind events. In addition, it would be worthwhile to design numerical models incorporating climate change projections (sea level rise and global warming temperatures) for storm surges and coastal inundations to allow more precisely informed coastal zone management plans.« less
2. Assessing the dependence structure between oceanographic, fluvial, and pluvial flooding drivers along the United States coastline

   https://doi.org/10.5194/hess-25-6203-2021  

   Nasr, Ahmed A. ; Wahl, Thomas ; Rashid, Md Mamunur ; Camus, Paula ; Haigh, Ivan D. ( January 2021 , Hydrology and Earth System Sciences)

   Abstract. Flooding is of particular concern in low-lying coastal zones that are prone to flooding impacts from multiple drivers, such as oceanographic (storm surge and wave), fluvial (excessive river discharge), and/or pluvial (surface runoff). In this study, we analyse, for the first time, the compound flooding potential along the contiguous United States (CONUS) coastline from all flooding drivers, using observations and reanalysis data sets. We assess the overall dependence from observations by using Kendall's rank correlation coefficient (τ) and tail (extremal) dependence (χ). Geographically, we find the highest dependence between different drivers at locations in the Gulf of Mexico, southeastern, and southwestern coasts. Regarding different driver combinations, the highest dependence exists between surge–waves, followed by surge–precipitation, surge–discharge, waves–precipitation, and waves–discharge. We also perform a seasonal dependence analysis (tropical vs. extra-tropical season), where we find higher dependence between drivers during the tropical season along the Gulf and parts of the East Coast and stronger dependence during the extra-tropical season on the West Coast. Finally, we compare the dependence structure of different combinations of flooding drivers, using observations and reanalysis data, and use the Kullback–Leibler (KL) divergence to assess significance in the differences of the tail dependence structure. We find, for example, that models underestimate the tailmore »dependence between surge–discharge on the East and West coasts and overestimate tail dependence between surge–precipitation on the East Coast, while they underestimate it on the West Coast. The comprehensive analysis presented here provides new insights on where the compound flooding potential is relatively higher, which variable combinations are most likely to lead to compounding effects, duringwhich time of the year (tropical versus extra-tropical season) compoundflooding is more likely to occur, and how well reanalysis data capture thedependence structure between the different flooding drivers.« less
3. Integrating storm surge modeling with traffic data analysis to evaluate the effectiveness of hurricane evacuation

   https://doi.org/10.1007/s11709-021-0765-1  

   Huang, Wenrui ; Yin, Kai ; Ghorbanzadeh, Mahyar ; Ozguven, Eren ; Xu, Sudong ; Vijayan, Linoj ( December 2021 , Frontiers of Structural and Civil Engineering)

   Abstract An integrated storm surge modeling and traffic analysis were conducted in this study to assess the effectiveness of hurricane evacuations through a case study of Hurricane Irma. The Category 5 hurricane in 2017 caused a record evacuation with an estimated 6.8 million people relocating statewide in Florida. The Advanced Circulation (ADCIRC) model was applied to simulate storm tides during the hurricane event. Model validations indicated that simulated pressures, winds, and storm surge compared well with observations. Model simulated storm tides and winds were used to estimate the area affected by Hurricane Irma. Results showed that the storm surge and strong wind mainly affected coastal counties in south-west Florida. Only moderate storm tides (maximum about 2.5 m) and maximum wind speed about 115 mph were shown in both model simulations and Federal Emergency Management Agency (FEMA) post-hurricane assessment near the area of hurricane landfall. Storm surges did not rise to the 100-year flood elevation level. The maximum wind was much below the design wind speed of 150–170 mph (Category 5) as defined in Florida Building Code (FBC) for south Florida coastal areas. Compared with the total population of about 2.25 million in the six coastal counties affected by storm surgemore »and Category 1–3 wind, the statewide evacuation of approximately 6.8 million people was found to be an over-evacuation due mainly to the uncertainty of hurricane path, which shifted from south-east to south-west Florida. The uncertainty of hurricane tracks made it difficult to predict the appropriate storm surge inundation zone for evacuation. Traffic data were used to analyze the evacuation traffic patterns. In south-east Florida, evacuation traffic started 4 days before the hurricane’s arrival. However, the hurricane path shifted and eventually landed in south-west Florida, which caused a high level of evacuation traffic in south-west Florida. Over-evacuation caused Evacuation Traffic Index ( ETI ) to increase to 200% above normal conditions in some sections of highways, which reduced the effectiveness of evacuation. Results from this study show that evacuation efficiency can be improved in the future by more accurate hurricane forecasting, better public awareness of real-time storm surge and wind as well as integrated storm surge and evacuation modeling for quick response to the uncertainty of hurricane forecasting.« less
4. Developing a Modeling Framework to Simulate Compound Flooding: When Storm Surge Interacts With Riverine Flow

   https://doi.org/10.3389/fclim.2020.609610  

   Loveland, Mark ; Kiaghadi, Amin ; Dawson, Clint N. ; Rifai, Hanadi S. ; Misra, Shubhra ; Mosser, Helena ; Parola, Alessandro ( February 2021 , Frontiers in Climate)

   Compound flooding is a physical phenomenon that has become more destructive in recent years. Moreover, compound flooding is a broad term that envelops many different physical processes that can range from preconditioned, to multivariate, to temporally compounding, or spatially compounding. This research aims to analyze a specific case of compound flooding related to tropical cyclones where the compounding effect is on coastal flooding due to a combination of storm surge and river discharge. In recent years, such compound flood events have increased in frequency and magnitude, due to a number of factors such as sea-level rise from warming oceans. Therefore, the ability to model such events is of increasing urgency. At present, there is no holistic, integrated modeling system capable of simulating or forecasting compound flooding on a large regional or global scale, leading to the need to couple various existing models. More specifically, two more challenges in such a modeling effort are determining the primary model and accounting for the effect of adjacent watersheds that discharge to the same receiving water body in amplifying the impact of compound flooding from riverine discharge with storm surge when the scale of the model includes an entire coastal line. In this study,more »we investigated the possibility of using the Advanced Circulation (ADCIRC) model as the primary model to simulate the compounding effects of fluvial flooding and storm surge via loose one-way coupling with gage data through internal time-dependent flux boundary conditions. The performance of the ADCIRC model was compared with the Hydrologic Engineering Center- River Analysis System (HEC-RAS) model both at the watershed and global scales. Furthermore, the importance of including riverine discharges and the interactions among adjacent watersheds were quantified. Results showed that the ADCIRC model could reliably be used to model compound flooding on both a watershed scale and a regional scale. Moreover, accounting for the interaction of river discharge from multiple watersheds is critical in accurately predicting flood patterns when high amounts of riverine flow occur in conjunction with storm surge. Particularly, with storms such as Hurricane Harvey (2017), where river flows were near record levels, inundation patterns and water surface elevations were highly dependent on the incorporation of the discharge input from multiple watersheds. Such an effect caused extra and longer inundations in some areas during Hurricane Harvey. Comparisons with real gauge data show that adding internal flow boundary conditions into ADCIRC to account for river discharge from multiple watersheds significantly improves accuracy in predictions of water surface elevations during coastal flooding events.« less
5. Extreme sea levels along coastal China: uncertainties and implications

   https://doi.org/10.1007/s00477-020-01964-0  

   Fang, Jiayi ; Wahl, Thomas ; Zhang, Qiang ; Muis, Sanne ; Hu, Pan ; Fang, Jian ; Du, Shiqiang ; Dou, Tingfeng ; Shi, Peijun ( February 2021 , Stochastic Environmental Research and Risk Assessment)

   Abstract Extreme sea levels (ESLs) due to typhoon-induced storm surge threaten the societal security of densely populated coastal China. Uncertainty in extreme value analysis (EVA) for ESL estimation has large implications for coastal communities’ adaptation to natural hazards. Here we evaluate uncertainties in ESL estimation and relevant driving factors based on hourly observations from 13 tide gauge stations and a complementary dataset derived from a hydrodynamic model. Results indicate significant uncertainties in ESL estimations stemming from using different EVA methods, which then propagate to the inundation assessment. Amplification factors due to sea-level rise (SLR) are highly sensitive to local relative SLR and the shape of the exceedance probability curve, which in turn depends on the selected EVA method. The hydrodynamic model hindcast indicates that high ESLs mainly occurred in eastern coastal China due to typhoon-induced storm surge. Larger uncertainties in the modelled ESLs are found for the coasts of the Yangtze River Delta, and particularly in the river mouth region. Future research and adaptation planning should prioritize these regions given expected future rising sea level, compound flood events, and human-induced factors (e.g. subsidence). This study provides theoretical and practical references for adaptation to ESL-related hazards along coastal China, with implicationsmore »for coastal regions worldwide.« less