Hurricane-induced Storm Surge Research Articles

Rapid Decadal Acceleration of Sea Level Rise along the U.S. East and Gulf Coasts during 2010–22 and Its Impact on Hurricane-Induced Storm Surge

Abstract Sea level rise (SLR) shows important spatiotemporal variability. A better understanding of characteristics and mechanisms of the variability is critical for future SLR projection and coastal preparedness. Here we analyze various observational and modeling data of sea level and its components, atmospheric pressure and winds, and ocean circulation in the North Atlantic. Both the century-long tide gauge data and the more recent altimetry data reveal a rapid decadal acceleration of SLR during 2010–22 along the U.S. East Coast and the Gulf of Mexico coast. The acceleration is most notable on the Southeast and Gulf Coasts, as quantified by the decadal rise rate, extreme annual sea level departure from the long-term trend, as well as the sea level record-breaking frequency and magnitude. Our analysis suggests that this SLR acceleration is largely a lagged response to the observed slowdown of the Atlantic meridional overturning circulation in 2009–10. In the North Atlantic, the response is characterized by a large-scale pattern of contrast changes in dynamic sea level between the Eastern Subpolar Gyre and the U.S. Southeast and Gulf Coasts. The latest global climate model generally captures this observed pattern and projects that further increase in greenhouse gas forcing will modify it over the twenty-first century. The faster SLR on the Southeast and Gulf Coasts, at a rate of more than 10 mm yr−1 during 2010–22, coincided with active and even record-breaking North Atlantic hurricane seasons in recent years. As a consequence, the elevated storm surge exacerbated coastal flooding and damage particularly on the Gulf Coast.

Spatial Accessibility Analysis of Emergency Shelters with a Consideration of Sea Level Rise in Northwest Florida

Hurricane-induced storm surge and flooding often lead to the closures of evacuation routes, which can be disruptive for the victims trying to leave the impacted region. This problem becomes even more challenging when we consider the impact of sea level rise that happens due to global warming and other climate-related factors. As such, hurricane-induced storm surge elevations would increase nonlinearly when sea level rise lifts, flooding access to highways and bridge entrances, thereby reducing accessibility for affected census block groups to evacuate to hurricane shelters during hurricane landfall. This happened with the Category 5 Hurricane Michael which swept the east coast of Northwest Florida with long-lasting damage and impact on local communities and infrastructure. In this paper, we propose an integrated methodology that utilizes both sea level rise (SLR) scenario-informed storm surge simulations and floating catchment area models built in Geographical Information Systems (GIS). First, we set up sea level rise scenarios of 0, 0.5, 1, and 1.5 m with a focus on Hurricane Michael’s impact that led to the development of storm surge models. Second, these storm surge simulation outputs are fed into ArcGIS and floating catchment area-based scenarios are created to study the accessibility of shelters. Findings indicate that rural areas lost accessibility faster than urban areas due to a variety of factors including shelter distributions, and roadway closures as spatial accessibility to shelters for offshore populations was rapidly diminishing. We also observed that as inundation level increases, urban census block groups that are closer to the shelters get extremely high accessibility scores through FCA calculations compared to the other block groups. Results of this study could guide and help revise existing strategies for designing emergency response plans and update resilience action policies.

Parameterized coastal fragilities and their application to aging port structures subjected to surge and wave

This study proposes a methodology for the development of parameterized fragility models for open type port structures subjected to hurricane-induced storm surge and wave loading, while also considering the potential influences of time-dependent aging and deterioration. The proposed framework uses a simulation-based strategy to propagate uncertainty in loads, geometrical configurations, material properties and capacities associated with different exposure conditions and failure modes (i.e. uplift, flexure, shear). Alternative classification-type statistical learning methods are tested to derive parameterized fragility models for each failure mode in order to evaluate limit state exceedance probability given a vector of deterministic or probabilistic parameters that define the structure and exposure conditions. Such parameterized coastal fragility models enable rapid application to a portfolio of aging port structures to explore the impact of current and future storm conditions, as illustrated via case study application for two terminals located in the Houston Ship Channel. The results reveal the dominant failure mode, spatial distribution of failure probabilities for structures within and across terminals, and influence of aging on surge and wave vulnerability of port structures.

The Study of the Hurricane-Induced Storm Surge and Bay-Ocean Exchange Using a Nesting Model

Lagoon systems are more heavily impacted by hurricanes, whereas the relevant storm surge modeling studies have been paid little attention to lagoon systems and the storm-induced exchange in lagoon systems is even less understood. To address this gap, a three-dimensional unstructured grid-based model was configured for the Maryland Coastal Bays, a typical lagoon system with two unique inlets (Ocean City Inlet (OCI) and Chincoteague Inlet (CI)), to investigate how Hurricane Sandy impacted inlet dynamics. A nesting model framework was applied to provide the necessary remote forcing from a large model domain and maintain the intricate shoreline and bathymetry of an inner model domain. Results indicated that the flux patterns varied in response to the change in wind direction and rising/falling high water levels from the coastal ocean, rather than a single flow pattern during the passage of Sandy. From October 29 05:00 to 17:00 UTC, mild (> 10 m/s) and strong (> 15 m/s) northerly winds accompanied by the rising high water level from the coastal ocean promoted a mean inflow pattern at the OCI and a mean outflow pattern at the CI. Strong southwesterly winds (> 15 m/s) dominated in the bays from October 30 03:00 to 15:00 UTC. Under strong southwesterly winds and falling high water levels from the coastal ocean, flux was transported landward at the CI and seaward at the OCI. Sensitivity experiments on various storm temporal scales showed that a net inflow pattern occurred in the bays, and the net exchange amounts became smaller in response to longer storm durations. Residual effect of relatively high river flow from Sandy could still influence the salinity at the OCI, whereas the CI salinity was not affected by river flow owing to a long distance between the CI and river locations.

A polynomial chaos framework for probabilistic predictions of storm surge events

We present a polynomial chaos-based framework to quantify the uncertainties in predicting hurricane-induced storm surges. Perturbation strategies are proposed to characterize poorly known time-dependent input parameters, such as tropical cyclone track and wind as well as space-dependent bottom stresses, using a handful of stochastic variables. The input uncertainties are then propagated through an ensemble calculation and a model surrogate is constructed to represent the changes in model output caused by changes in the model input. The statistical analysis is then performed using the model surrogate once its reliability has been established. The procedure is illustrated by simulating the flooding caused by Hurricane Gustav 2008 using the ADvanced CIRCulation model. The hurricane’s track and intensity are perturbed along with the bottom friction coefficients. A sensitivity analysis suggests that the track of the tropical cyclone is the dominant contributor to the peak water level forecast, while uncertainties in wind speed and in the bottom friction coefficient show minor contributions. Exceedance probability maps with different levels are also estimated to identify the most vulnerable areas.

EFFECTS OF WAVE LOADING CONDITIONS ON THE FRAGILITY OF PILE-SUPPORTED WHARVES/PIERS

Pile-supported wharves/piers are often subjected to extreme forces caused by coastal hazards. For instance, hurricanes Katrina (2005) and Wilma (2005) caused significant structural damage to pile-supported piers (Gutierrez et al. 2006) and wharves (Bardi et al. 2007), respectively. The problem becomes more pressing as the hazard exposure of these structures evolves with sea level rise caused by climate change (Lamberti et al. 2011). Thus, in light of gaps in the risk assessment of these structures in hurricane prone regions, Balomenos and Padgett (2018a) proposed the first probabilistic framework for developing analytical fragility models for pile-supported wharves/piers vulnerable to hurricane-induced storm surge and waves. Then, Balomenos and Padgett (2018b) adopted this framework to provide an initial exploration into the sensitivity of the fragility estimate to epistemic uncertainties in the wave load model. However, considering that the wave period may have a significant variation at or near the coast based on reported periods during hurricanes Katrina and Rita (Dietrich et al. 2011), this study further explores the influence of hazard parameter variation on the resulting failure probability of these structures, while propagating uncertainties in other parameters such as concrete compressive strength, deck thickness, etc.

Storm surge fragility assessment of above ground storage tanks

This study proposes a dual layer metamodel based approach to develop parameterized fragility functions for above ground storage tanks (ASTs) subjected to hurricane induced storm surge. ASTs are extensively used in petrochemical facilities for storing large volumes of hazardous substances. Failure of ASTs due to storm surge may lead to spills that can cause severe environmental damage and considerable economic loss. A significant number of ASTs are located in coastal areas which are susceptible to hurricanes, such as in the Houston Ship Channel, Texas. However, tank design guidelines are deficient in addressing prevention of surge related failures. Although their vulnerability has been exposed during past hurricanes, the literature lacks studies on performance analysis of ASTs during storm surge events. In this light, a method is presented to derive fragility functions for the most important failure modes of ASTs – flotation and buckling – in addition to the system fragility, considered as series system of failure modes. For this purpose, a novel dual layer metamodel based approach is proposed where a limited number of simulations are used to train the first binary classifier, which predicts failure of tanks, upon which the second metamodel is trained; the final metamodel is used to derive parameterized fragility functions. This approach significantly reduces the number of limit state evaluations, which may require costly finite element simulations, and enables accurate fragility assessment to capture the nonlinear behavior of tanks under surge loading, while also considering the correlation between failure modes during system fragility modeling. Results indicated that the fragility estimates of a typical tank obtained with the dual layer metamodel compare well with those derived by high fidelity methods such as Monte Carlo Simulations. In order to demonstrate the application of the parameterized fragility functions to study the effect of variation in design and construction parameters, fragilities of four case study tanks are evaluated. The results highlight the effect of parameter variation on the fragilities and offer insights into the influence of alternative design impacts on tank vulnerability. For example, anchoring tanks significantly reduces the probability of flotation; however, anchoring leads to buckling dominated failures.

Characteristics of river flood and storm surge interactions in a tidal river in Rhode Island, USA

During a hurricane event, heavy rainfall can cause storm runoff and river flood. In tidal rivers, hurricane induced storm surge can increase the river downstream boundary water levels. The interactions of storm-induced rainfall runoff and storm surge in tidal rivers may cause more severe flood during hurricane events. In this study, hydrodynamic model simulations were conducted to characterize the interactions of rainfall runoff and storm surge in a tidal river in Rhode Island, USA. River floods under scenarios with and without storm surge were compared.

A numerical study of the impact of hurricane-induced storm surge on the Herbert Hoover Dike at Lake Okeechobee, Florida

Hurricanes Frances, Jeanne, and Wilma passed over Lake Okeechobee, Florida, in September 2004 and October 2005, respectively. Strong winds caused a large surface seiche on the lake during all three storms. These storms resulted in erosion damage to the Herbert Hoover Dike (HHD) on Lake Okeechobee. In this paper, we use the Fully Adaptive Storm Tide (FAST) model (Kelly et al. in Coast Eng J 57(4):1–30, 2015, Nat Hazards 83:53–74, 2016) to study the response of the lake (in terms of the water level fluctuations and induced currents) to hurricanes Frances, Jeanne, and Wilma. Comparisons of the modeled surface water level with the observations are in overall good agreement for all three hurricanes. The modeled results suggest that the strong currents induced by the storm winds may be the dominant factor controlling the dike erosion observed at the lake side. The locations of erosion damage to the dike are consistent with the modeled high velocity zones during these three storms. In addition, numerical experiments have been conducted with eight hypothetical category 5 hurricanes approaching from different directions to investigate the erosion-prone zones related to high velocities in the vicinity of the dike. The results of the study should help to provide insight into vulnerable reaches of the HHD and inform flood control in the Okeechobee region.

Probabilistic hurricane-induced storm surge hazard assessment in Guadeloupe, Lesser Antilles

Abstract. Current storm surge hazard maps in the French West Indies are essentially based on simple statistical methods using limited historical data and early low-resolution models which do not take the effect of waves into account. In this paper, we infer new 100-year and 1000-year surge levels in Guadeloupe from the numerical modelling of storm surges induced by a large set of synthetic events that are in statistical agreement with features of historical hurricanes in the North Atlantic Basin between 1980 and 2011. Computations are performed using the wave-current coupled model ADCIRC–SWAN with high grid resolutions (up to 40–60 m) in the coastal and wave dissipation areas. This model is validated against observations during past events such as hurricane HUGO (1989). Results are generally found to be in reasonable agreement with past studies in areas where surge is essentially wind-driven, but found to differ significantly in coastal regions where the transfer of momentum from waves to the water column constitutes a non-negligible part of the total surge. The methodology, which can be applied to other islands in the Lesser Antilles, allows storm surge level maps to be obtained that can be of major interest for coastal planners and decision makers in terms of risk management.

Tracking hurricane-generated storm surge with washover fan stratigraphy

Research Article| February 01, 2015 Tracking hurricane-generated storm surge with washover fan stratigraphy John Shaw; John Shaw * 1Department of Geosciences, 216 Ozark Hall, University of Arkansas, Fayetteville, Arkansas 72701, USA2Jackson School of Geosciences, University of Texas at Austin, C9000, Austin, Texas 78712, USA3Department of Geology and Geophysics, Department 3006, University of Wyoming, Laramie, Wyoming 82071, USA *E-mail: shaw84@uark.edu Search for other works by this author on: GSW Google Scholar Yao You; Yao You 2Jackson School of Geosciences, University of Texas at Austin, C9000, Austin, Texas 78712, USA †Current address: Hess Corporation, 1501 McKinney, Houston, Texas 77010, USA. Search for other works by this author on: GSW Google Scholar David Mohrig; David Mohrig 2Jackson School of Geosciences, University of Texas at Austin, C9000, Austin, Texas 78712, USA Search for other works by this author on: GSW Google Scholar Gary Kocurek Gary Kocurek 2Jackson School of Geosciences, University of Texas at Austin, C9000, Austin, Texas 78712, USA Search for other works by this author on: GSW Google Scholar Author and Article Information John Shaw * 1Department of Geosciences, 216 Ozark Hall, University of Arkansas, Fayetteville, Arkansas 72701, USA2Jackson School of Geosciences, University of Texas at Austin, C9000, Austin, Texas 78712, USA3Department of Geology and Geophysics, Department 3006, University of Wyoming, Laramie, Wyoming 82071, USA Yao You †Current address: Hess Corporation, 1501 McKinney, Houston, Texas 77010, USA. 2Jackson School of Geosciences, University of Texas at Austin, C9000, Austin, Texas 78712, USA David Mohrig 2Jackson School of Geosciences, University of Texas at Austin, C9000, Austin, Texas 78712, USA Gary Kocurek 2Jackson School of Geosciences, University of Texas at Austin, C9000, Austin, Texas 78712, USA *E-mail: shaw84@uark.edu Publisher: Geological Society of America Received: 14 Aug 2014 Revision Received: 18 Nov 2014 Accepted: 21 Nov 2014 First Online: 09 Mar 2017 Online ISSN: 1943-2682 Print ISSN: 0091-7613 © 2014 Geological Society of America Geology (2015) 43 (2): 127–130. https://doi.org/10.1130/G36460.1 Article history Received: 14 Aug 2014 Revision Received: 18 Nov 2014 Accepted: 21 Nov 2014 First Online: 09 Mar 2017 Cite View This Citation Add to Citation Manager Share Icon Share Facebook Twitter LinkedIn MailTo Tools Icon Tools Get Permissions Search Site Citation John Shaw, Yao You, David Mohrig, Gary Kocurek; Tracking hurricane-generated storm surge with washover fan stratigraphy. Geology 2015;; 43 (2): 127–130. doi: https://doi.org/10.1130/G36460.1 Download citation file: Ris (Zotero) Refmanager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search All ContentBy SocietyGeology Search Advanced Search Abstract We use the stratigraphy preserved in a washover fan to reconstruct the timing or emplacement and environmental conditions along the Matagorda Peninsula, Texas, during Hurricane Ike in 2008. Washover fan stratigraphy preserves a topset-foreset break (TFB) that rises 0.42 m in elevation as the fan built landward. We constrain overwash flow depths to 0.1–0.32 m through deposit sedimentology, and tie the rising trajectory of the TFB to rising storm surge water levels measured in the back-barrier bay (0.03 m h–1) as the hurricane approached the coast. This relation allows us to estimate that the fan took 0.52–0.90 days to build, and was finished building before the storm surge peaked. This is 15–25% of the 3.5 days of hurricane-induced storm surge near the site. We show how washover stratigraphy can be used to constrain the timing and amount of sediment redistribution on a coast associated with a hurricane; information that is necessary to test and/or calibrate existing numerical models that predict shoreline change during hurricanes. You do not have access to this content, please speak to your institutional administrator if you feel you should have access.

RECONNAISSANCE LEVEL STUDIES ON A STORM SURGE BARRIER FOR FLOOD RISK REDUCTION IN THE HOUSTON-GALVESTON BAY

The Houston - Galveston area is at significant risk from hurricane induced storm surges. This paper summarizes ongoing studies on flood risk reduction for the region. Firstly, based on a simplified probabilistic hurricane surge model , the return periods of surges within the bay have been estimated. This model framework can be used to assess the effectiveness of several risk reduction interventions. Sketch- and conceptual designs have been made of a storm surge barrier in the Bolivar Roads, that would be part of the Ike Dike coastal protection concept. Such a storm surge barrier would consist of two parts, an environmental section for flow requirements (consisting of caissons with vertical gates) and a navigation section of the barrier (consisting of a barge gate), which would allow unhindered passage of navigation during normal conditions. Future questions and challenges for flood risk reduction in the Bay are identified.

Multi-hazard risk assessment of highway bridges subjected to earthquake and hurricane hazards

This paper presents a Parameterized Fragility based Multi Hazard Risk Assessment (PF-MHRA) procedure risk for assessment of a portfolio of highway bridges subjected to earthquake and hurricane events. As a part of this approach, parametric bridge fragility functions are generated for the two hazards, which are an advance over conventional fragility curves as they can be used for bridges with different geometric and structural properties given exposure to different hazard types. The parametric bridge fragility functions are derived using metamodels and stepwise logistic regression with a non-linear logit function. The relative change in hurricane and earthquake fragilities of the bridges is captured by the parametric fragility functions given variation in design details or geometric parameters of the bridges. These fragility functions are combined with regional hazard data to evaluate annual risk, which is measured as the annual probability of damage. For this purpose, hazard input parameters are identified for earthquakes and hurricane events and a new risk assessment procedure for bridges subjected to hurricane wave and surge loading is also developed. Furthermore, coupling of the risk assessment procedure with parameterized fragilities enables a comparative assessment of the contributions of different hazards to the total risk as the bridge details differ in a portfolio. The proposed framework is applied to multi-span simply supported concrete girder bridges located in South Carolina. The application demonstrates the identification and derivation of input models for the multi-hazard risk assessment for earthquakes and hurricane induced storm surge and wave loading. By applying the proposed method, insights are gained on the influence of different bridge geometries and hazard exposure conditions to the risk of bridge damage. The potential of the proposed procedure to serve as an aid to risk based design of bridges is also highlighted.

A coral-rubble ridge as evidence for hurricane overwash, Anegada (British Virgin Islands)

Abstract. A coral-rubble ridge fringes part of the north shore of Anegada, a low-lying island in the northern Caribbean. Both historical reports and the geological record underline its vulnerability to tsunami and hurricanes. In this study we document the sedimentary characteristics of a coral-rubble ridge, which extends discontinuously along 1.5–1.8 km of chiefly north-facing shores at Soldier Wash. The ridge is less distinctive and appears only in patches along the west-facing shoreline at Windless Bight, where the wave regime is calmer. It is located ca. 8 m from the fair-weather shore, has a maximum width of 15 m and a maximum thickness of 0.8 m. The lower seaward-facing slope of the ridge is relatively flat, probably due to successive reworking, whereas the upper seaward slope is steep and partly displays avalanching faces. The landward flank is gently sloping and terminates abruptly. The ridge is mainly composed of well-rounded, encrusted and bored coral rubble (average diameter of 16 cm) that has been reworked in the shallow marine environment prior to transport. Only a few pieces of angular beach rock and karstified Pleistocene limestone are incorporated. The components build a clast-supported framework. No sand is present in the interstices. Imbrication of flat clasts indicates a deposition during landward bed load transport. The ridge morphology, composition and related hydrodynamic conditions during its emplacement are typical for coral-rubble ridges deposited by hurricane-induced storm surges. In comparison, nearby evidence for tsunami inundation is very different because the tsunami-transported coral boulders on Anegada are much bigger (2 m) than the biggest components in the ridge, they are deposited much farther inland (up to 1.5 km), and the corals seem to have been freshly broken out of the reef by the tsunami. The age of the ridge is difficult to estimate. The dark grey surface of the ridge is caused by bioweathering by endolithic organisms that takes tens of years and may give a very rough estimate of the minimum age of the ridge. Storms and related surges that built the ridge were likely stronger than 2010 hurricane Earl, which attained category 4 north of the island. Earl was able to slightly rework the lower seaward part of the ridge, but transported only few and smaller pieces of coral rubble and sand onshore. Therefore, the coral-rubble ridge found at the north shore of Anegada may imply that the island is vulnerable to hurricane-induced surges of greater impact (in relation to storm path and intensity) compared with the any of the recently documented storms which were only able to rework the ridge.

Three-Dimensional Modeling of Storm Surge and Inundation Including the Effects of Coastal Vegetation

Two-dimensional (2D) and three-dimensional (3D) hydrodynamic models are used to simulate the hurricane-induced storm surge and coastal inundation in regions with vegetation. Typically, 2D storm surge models use an enhanced Manning coefficient while 3D storm surge models use a roughness height to represent the effects of coastal vegetation on flow. This paper presents a 3D storm surge model which accurately resolves the effects of vegetation on the flow and turbulence. First, a vegetation-resolving 1DV Turbulent Kinetic Energy model (TKEM) is introduced and validated with laboratory data. This model is both robust enough to accurately model flows in complex canopies, while compact and efficient enough for incorporation into a 3D storm surge-wave modeling system: Curvilinear Hydrodynamics in 3D-Surface WAves Nearshore (CH3D-SWAN). Using the 3D vegetation-resolving model, three numerical experiments are conducted. In the first experiment, comparisons are made between the 2D Manning coefficient approach and the 3D vegetation-resolving approach for simple wind-driven flow. In a second experiment, 2D and 3D representations of vegetation produce similar inundations from the same hurricane forcing, but differences in momentum are found. In a final experiment, varying inundation between seemingly analogous 2D and 3D representations of vegetation are demonstrated, pointing to a significant scientific need for data within wetlands during storm surge events. This study shows that the complex flow structures within vegetation canopies can be accurately simulated using a vegetation-resolving 3D storm surge model, which can be used to assess the feasibility for future wetland restoration projects.

A modeling study of coastal inundation induced by storm surge, sea-level rise, and subsidence in the Gulf of Mexico

The northern coasts of the Gulf of Mexico (GoM) are highly vulnerable to the direct threats of climate change, such as hurricane-induced storm surge, and such risks are exacerbated by land subsidence and global sea-level rise. This paper presents an application of a coastal storm surge model to study the coastal inundation process induced by tide and storm surge, and its response to the effects of land subsidence and sea-level rise in the northern Gulf coast. The unstructured-grid finite-volume coastal ocean model was used to simulate tides and hurricane-induced storm surges in the GoM. Simulated distributions of co-amplitude and co-phase lines for semi-diurnal and diurnal tides are in good agreement with previous modeling studies. The storm surges induced by four historical hurricanes (Rita, Katrina, Ivan, and Dolly) were simulated and compared to observed water levels at National Oceanic and Atmospheric Administration tide stations. Effects of coastal subsidence and future global sea-level rise on coastal inundation in the Louisiana coast were evaluated using a “change of inundation depth” parameter through sensitivity simulations that were based on a projected future subsidence scenario and 1-m global sea-level rise by the end of the century. Model results suggested that hurricane-induced storm surge height and coastal inundation could be exacerbated by future global sea-level rise and subsidence, and that responses of storm surge and coastal inundation to the effects of sea-level rise and subsidence are highly nonlinear and vary on temporal and spatial scales.

Hybrid numerical methods to solve shallow water equations for hurricane induced storm surge modeling

In this paper an efficient numerical method based on hybrid finite element and finite volume techniques to solve hurricane induced storm surge flow problem is presented. A segregated implicit projection method is used to solve the 2D shallow water equations on staggered unstructured meshes. The governing equations are written in non-conservation form. An intermediate velocity field is first obtained by solving the momentum equations with the matrix-free implicit cell-centered finite volume method. The nonlinear wave equation is solved by the node-based Galerkin finite element method. This staggered-mesh scheme is distinct from other conventional approaches in that the velocity components and auxiliary variables are stored at cell centers and vertices, respectively. The present model uses an implicit method, which is very efficient and can use a large time step without losing accuracy and stability.The hurricane induced wind stress and pressure, bottom friction, Coriolis effect, and tidal forcing conditions are implemented in this model. The levee overtopping option is implemented in the model as well. Hurricane Katrina (2005) storm surge has been simulated to demonstrate the robustness and applicability of the model.

Potential impacts of long-term subsidence on the wetlands and evacuation routes in coastal Louisiana

A steady-state subsidence forecast model was developed as a proof of concept to estimate changes in surface elevations of the wetlands and evacuation routes across coastal Louisiana for the years 2015, 2025, 2050, and 2100. Subsidence estimates were derived from an empirical study published by the National Geodetic Survey. Forecasted vertical change was subtracted from current surface elevations. Land and evacuation routes estimated to have surfaces at or below 0 m in elevation, NAVD88, were quantified and classified as vulnerable to inundation hazards. The extent of the coastal zone susceptible to hurricane induced storm surge was also evaluated relative to surge models published by the National Weather Service. The results indicate spatially heterogeneous rates of subsidence that are forecasted to consume nearly 50 % of the existing coastal margin wetlands by 2100. The most significant rate increases are anticipated between 2015 and 2050. Relative to the impact on evacuation routes, subsidence occurring between the 2015 and 2025 forecast years expanded at slower rates when compared to the latter half of the century. Subsidence adjusted storm surge forecasts reveal similar patterns. The methods employed and findings produced demonstrate forecasting capabilities that provide emergency managers and transportation engineers with resources applicable to evacuation modeling, hazard mitigation, environmental sustainability research, costal restoration efforts, and more.

Effect of hurricane paths on storm surge response at Tianjin, China

A hurricane induced storm surge simulation system was developed for Tianjin coast, which consists of a hurricane model and a storm surge model. The peak storm surge result of the simulation agreed well with that of the observation. Three observed paths (Rita, Mimie and WINNIE) and a hypothetical path (Rita2) were chosen as the selective hurricane paths according to their positions relative to Tianjin. The sensitivity of Tianjin storm surge to the four paths was investigated using the validated storm surge simulation system. Three groups of experiments were done. In group one, the models were forced by the wind field and air pressure; in group two and three the models were forced by the wind only and the air pressure only respectively. In the experiments, the hurricane moved with a fixed speed and an intensity of 50 year return period. The simulation results show that path of the type Rita2 is the easiest to cause storm surge disaster in Tianjin, and the effect of air pressure forcing is most evident for path of the type Rita in Tianjin storm surge process. The above conclusions were analyzed through the evolution of the wind fields and the air pressure distributions. Comparing the experiment results of Group one, two and three, it can be seen that the storm surge is mainly induced by the wind forcing and the nonlinear interaction between the effect of wind forcing and air pressure forcing on the storm surge tends to weaken the storm surge.

The vulnerability of the elderly to hurricane hazards in Sarasota, Florida

Although the elderly are commonly thought to be disproportionately vulnerable to natural hazards, the elderly populations of coastal communities are continuing to grow. Because there is little to no empirical hazards work specifically addressing the vulnerable elderly in coastal communities, this paper uses Sarasota County, Florida, as a case study to analyze how vulnerable the elderly are to hurricane hazards and whether all elderly people are equally vulnerable. To explore the spatial variations in degree and composition of vulnerability among this population, the analysis maps physical exposure to hurricane storm-surge inundation and precipitation-induced flooding and creates social vulnerability indices by applying principal components analysis to census block group data in a geographic information system. The results show that elderly inhabitants of barrier islands face a considerable physical threat from hurricane-induced storm surge and flooding but are less socially vulnerable because of their wealth; the elderly living inland are far less physically vulnerable but are poorer and consequently demonstrate high socioeconomic sensitivity and limited adaptive capacity to these hurricane hazards. The paper concludes that the elderly are not equally vulnerable: there are many different types of elderly living in many different locations, and their vulnerability varies by type and over space. Effective vulnerability reduction measures should account for these differences between the elderly populations.