Hurricane Gustav Research Articles

Storm Dynamics Control Sedimentation and Shelf‐Bay‐Marsh Sediment Exchange Along the Louisiana Coast

AbstractHurricanes can benefit wetland accretion by augmenting the delivery of mineral sediment, an essential process allowing marshes to offset submergence during rising sea levels. Using Hurricane Gustav (2008, Louisiana) as a control, we examined eight synthetic storms with varying characteristics (track, speed, intensity, size) to evaluate sediment exchange between the inner shelf and bay and bay‐to‐marsh interfaces. All storms showed net landward sediment exchange from the inner shelf to the bay to the marsh—storms with closer proximity, higher intensity, and slower forward speed positively correlated with net sediment exchange; storm size had little impact. Except for slow‐moving storms (½ speed of Gustav), our analyses suggest that most hurricane scenarios cause net bay erosion, because more sediment is conveyed to landward wetlands than is replenished from erosion of the inner shelf. Our results suggest that the ongoing deepening of the bay will likely worsen because of rising sea levels.

Estuarine salinity extremes: Using the Coastal Salinity Index to quantify the role of droughts, floods, hurricanes, and freshwater flow alteration

In the face of accelerating climate change, advancing understanding of how extreme climatic events influence estuarine salinities can help to inform resource management. Extreme salinities driven by droughts, hurricanes, floods, and freshwater flow alterations can lead to ecological transformations in estuarine ecosystems. Here, we applied the Coastal Salinity Index (CSI; Conrads and Darby 2017) to 22 years (1998–2020) of salinity data in a Louisiana estuary (Barataria Estuary, USA) to elucidate the impacts of extreme events on estuarine salinities. The CSI is an index to quantify salinity patterns at a specific location through long-term averages and deviations from historical average conditions. We calculated and compared CSI values for four stations distributed along an estuarine salinity gradient. We identified 10 events between 1998 and 2020 that produced extreme salinities, including two droughts, four hurricanes, three floods, and one freshwater diversion. The droughts of 2000 and 2006 caused surface water salinities to increase substantially throughout the estuary. The effects of hurricanes were highly variable, with some storms leading to elevated salinities throughout the entire estuary (e.g., Hurricanes Katrina and Rita in 2005), whereas other storms led to elevated salinities for some but not all stations (e.g., Hurricanes Gustav and Ike in 2008 or Hurricane Isaac in 2012). The opening of a freshwater river diversion in 2010 contributed to fresher conditions throughout the estuary and appeared to reduce or eliminate the increases in salinity that normally occur during the summer, although these effects were short-lived. Mississippi River floods in 2008, 2011, and 2019 reduced salinities throughout the estuary, but the effects were most pronounced in the lower estuary compared to the upper estuary. Collectively, our results advance understanding of the influence of extreme events on estuarine salinity regimes. Our analyses also highlight the value of the CSI for identifying periods with extreme salinities (i.e., extreme high or low salinities) via calculations that place salinity levels within and across estuaries within a historical context.

Healthcare Impacts Associated with Federally Declared Disasters—Hurricanes Gustave and Ike

People impacted by disasters may have adverse non-communicable disease health effects associated with the disaster. This research examined the independent and joint impacts of federally declared disasters on the diagnosis of hypertension (HTN), diabetes (DM), anxiety, and medication changes 6 months before and after a disaster. Patients seen in zip codes that received a federal disaster declaration for Hurricanes Gustave or Ike in 2008 and who had electronic health records captured by MarketScan® were analyzed. The analysis included patients seen 6 months before or after Hurricanes Gustav and Ike in 2008 and who were diagnosed with HTN, DM, or anxiety. There was a statistically significant association between post-disaster and diagnosis of hypertension, X2 (1, n = 19,328) = 3.985, p = 0.04. There was no association post-disaster and diabetes X2 (1, n = 19,328) = 0.778, p = 0.378 or anxiety, X2 (1, n = 19,328) = 0.017, p = 0.898. The research showed that there was a change in the diagnosis of HTN after a disaster. Changes in HTN are an additional important consideration for clinicians in disaster-prone areas. Data about non-communicable diseases help healthcare disaster planners to include primary care needs and providers in the plans to prevent the long-term health impacts of disasters and expedite recovery efforts.

Long-Term Suppression of Hardwood Regeneration by Chinese Privet (Ligustrum sinense)

Native hardwood regeneration in the southeast United States is hindered by repeat disturbance events and the presence of invasive species. Our study aimed to determine the ability of native species in an unmanaged urban forest fragment to persist following high winds from hurricane Gustav in 2008 and subsequent salvage logging. In 2009, researchers estimated the density and composition of the regeneration and overstory trees as well as percent crown cover of invasive Chinese privet. Percent Chinese privet cover was visibly high, leading them to believe it may be inhibiting native hardwood establishment. Ten years later in 2019, we returned to the plots to take repeat measurements. Forest composition remains the same and privet crown cover remains high. There has been no increase in regenerating individuals, and overstory trees per hectare and basal area remains low. These results confirm that the heavy Chinese privet presence is persistent long term and will require management to promote reproduction of native overstory tree species.

Deltaic floodplain wetland vegetation dynamics along the sediment surface elevation gradient and in response to disturbance from river flooding and hurricanes in Wax Lake Delta, Louisiana, USA

Herbaceous wetland vegetation species percent cover data collected over five growing seasons (2007–2011) was used to define unique species assemblages along the elevation gradient of deltaic islands in the actively prograding deltaic floodplain wetlands in the Wax Lake Delta, a major distributary of the Mississippi River. The passage of Hurricanes Gustav and Ike in September 2008 as well as a major river flood in spring of 2011 provided an opportunity to quantify the response and recovery of the vegetation community following disturbances of varying intensities. Two significant persistent species assemblages were observed from 2007 through 2011. The higher elevation species assemblage occurred above mean low water (MLW; –0.04 m NAVD88). While the lower elevation species assemblage occurred at elevations ranging from –0.47 to 0.30 m NAVD88. These unique lower and higher elevation species assemblages overlap at intertidal elevations. Hurricanes Gustav and Ike drastically reduced aboveground vegetation and percent cover immediately following the storms particularly for lower elevation species. No aboveground cover was observed for Sagittaria latifolia, Nelumbo lutea, Potamogeton nodosus, or Submerged Aquatic Vegetation (SAV) in any of the sampling stations following the hurricanes, compared to pre-hurricane aboveground cover mean ranging from 2 to 5%. Sagittaria platyphylla aboveground cover decreased from a pre-hurricane mean of 12.5% to <1% following the hurricanes. In subsequent years the community composition for all species returned to pre-disturbance cover, with the significant species assemblages returning within two years. In 2011 the major river flood resulted in disturbance that reduced species richness within both assemblages, likely related to differences in flood tolerance of vegetation species, with Nelumbo lutea cover expanding from a mean of 10% cover in the year prior to the flood to 22.5% following the flood. Vegetation community composition was shown to be robust to major river floods and hurricane storm surge passage.

Risk Assessment of Dam-Breach Flood Under Extreme Storm Events

In recent years, as a result of increasingly intensive rainfall events, the associated water erosion and corrosion have led to the increase in breach risk of aging dams in the United States. In this study, a hydrodynamic model was used to the inundation simulation under three hypothetical extreme precipitation-induced homogeneous concrete dam-breach scenarios. All hydraulic variables, including water depth, flow velocity, and flood arriving time over separated nine cross-sections in the Catawba River, were calculated. The hypothetical simulation results illustrate that the impact of Hurricane Florence’s rainfall is far more severe over the downstream of hydraulic facilities than that of the Once-in-a-century storm rainfall event. Although Hurricane Florence’s rainfall observed in Wilmington had not historically happened near the MI Dam site, the river basin has a higher probability to be attacked by such storm rainfall if more extreme weather events would be generated under future warming conditions. Besides, the time for floodwaters to reach cross-section 6 under the Hurricane Gustav scenario is shorter than that under the Once-in-a-century rainfall scenario, making the downstream be inundated in short minutes. Since the probability can be quantitatively evaluated, it is of great worth assessing the risk of dam-break floods in coastal cities where human lives are at a vulnerable stage.

Differentiating hurricane deposits in coastal sedimentary records: two storms, one layer, but different processes

Hurricanes Gustav and Ike consecutively impacted coastal Louisiana in 2008. Two sediment cores taken from Bay Champagne, a coastal backbarrier lake near Port Fourchon, Louisiana, contain a depositional layer of clastic sediment up to 21 cm thick attributable to these two storms. X-ray fluorescence measurements and statistical analysis suggest the two storm events can be distinguished from one another based on contrasting geochemical profiles. The bottom portion of the layer, attributable to Gustav, contains high concentrations of marine-derived elements, suggesting a strong influence from storm surge. The top portion of the layer, attributed to Ike, contains higher concentrations of terrestrially-derived elements, indicative of contributions from fluvially-driven deposition. The elemental concentration profiles and corresponding environmental data suggest the storm deposits in each core were deposited through two distinct hydrological processes: a storm surge-driven marine intrusion event during Gustav, followed by a mixture of storm-surge and fluvial deposition resulting from Ike. Results show that hurricane-generated deposition in coastal environments is a bi-directional process in which the role of fluvial freshwater deposition cannot be ignored.

Morphodynamic modeling of a low-lying barrier subject to hurricane forcing: The role of backbarrier wetlands

Along much of the world's coastline, coastal barriers serve as the first line of defense against oceanic and meteorological forces. Extreme storms cause large morphological changes on coastal barriers through high sediment transport rates, which may degrade their defensive capabilities. The understanding of morphological impacts is therefore important for coastal resiliency, but is often challenged by site-specific characteristics, such as land cover and sediment availability, and their poorly understood impacts on the governing physical processes. The Caminada Headlands, Louisiana, USA presents unique considerations for morphodynamic modeling with regard to its low-lying topography, variable land cover, nearshore muddy substrate and sand deficiency. This study investigates the effects of land cover and limited sediment supply on low-lying barrier island morphology under storm conditions by using physics-based numerical models. A high-resolution, local-scale sediment transport/morphodynamic model (XBeach) of the Caminada Headlands is verified for Hurricane Gustav's (2008) impact using pre- and post-storm LIDAR surveys. When accurate input data are used to create physics-based numerical models these tools are robust in hindcasting storm impacts and provide a wealth of information as to the governing processes, which is otherwise difficult to obtain observationally. The simulation results show that a short-duration overwash regime dominates the morphological change in this low-lying barrier and is influenced by backbarrier wetland deterioration. The morphological response to overwash is modulated by backbarrier land cover and topography, as reduced accommodation space limits landward transport during the subsequent inundation regime. An intact backbarrier marsh reduces landward washover sediment transport distances and promotes deposition at supratidal elevations. In light of these findings, simultaneous restoration/creation of backbarrier wetlands in conjunction with subaerial beach renourishment may be an effective form of increasing the resiliency of low-lying barriers subject to frequent overwashing.

Hurricane Summer by Asha Bromfield

Reviewed by: Hurricane Summer by Asha Bromfield Deborah Stevenson, Editor Bromfield, Asha Hurricane Summer. Wednesday/St. Martin’s, 2021 [400p] Trade ed. ISBN 9781250622235 $18.99 E-book ed. ISBN 9781250622303 $10.99 Reviewed from digital galleys R Gr. 10 up Tilla is eighteen, shepherding her nine-year-old sister Mia as the two travel from Toronto to Jamaica for a summer with their never-home father. Once there, she’s hurt and furious to discover Dad will be largely staying in Kingston while she and Mia bunk with extended family in the country. As the summer goes on, she learns more about her father’s strengths (he’s financially helping most of his extended family) and weaknesses (unbeknownst to her mother, he’s got another family in Kingston), renews her friendship with a cousin, falls for one sexy guy (who’s promised to somebody else) and makes out with another one, and suffers a sexual assault and a torrent of slut-shaming. She also falls in love with the beauty of Jamaica, and she sees its fragility when it’s hit by the ferocity of Hurricane Gustav, an event that leads to personal as well as national loss. The father plot roots this in domestic realism but it blooms into reality-enhanced melodrama, with heightened emotion, shivering, satisfying sexual encounters, and even a Real Housewives–level catfight. Underneath the sometimes literal Sturm und Drang are sharp observations about cultural difference, class implications, economic privilege, and colorism; the Jamaican characters’ use of Patois helps mark Tilla as the outsider she is (called, sometimes affectionately, sometimes derisively, “Canada”). Prose about Tilla’s reflections and the glory of the countryside is accessible yet sumptuous, and readers will yearn for an island summer, preferably sans hurricane, of their own. Copyright © 2021 The Board of Trustees of the University of Illinois

Risk of hydrological failure under the compound effects of instant flow and precipitation peaks under climate change: A case study of Mountain Island Dam, North Carolina

The risk of flooding as a result of infrastructure failures among aging dams in the United States continues to increase dramatically, which lead to the severe consequences in socio-economic and environmental terms. Environmental impacts regarding the failure of hydrological facilities, including the loss of sustainable habitats and clean water previously provided by reservoir, have raised concerns. In this study, the potential risks to hydrological infrastructure within the context of the 100-year joint probability of maximum rainfall and peak water stage were examined over the Mountain Island Dam (North Carolina, USA) for the period of 1950–2099. We found that nearly 92% of annual maximum extreme rainfall events were closely related to the passage of hurricanes over the dam’s watershed over the 25 years of the validation period. The results show that the projected annual maximum precipitation is likely to intensify under the RCP8.5 climate scenario and the frequency of the annual precipitation maxima exceeding 100 mm/day is projected to increase in the future. Noticeably, it is found that even weaker storm events can contribute a significant amount of rainfall at inland locations. The probability of occurrence of a hurricane like Gustav is higher than that of a 100-year storm rainfall event under the RCP8.5 climate change scenario, this type of storm rainfall will more likely occur near the Mountain Island Dam in the future. Inspectors should focus more on observing water level fluctuation and rainfall volume variation at station two under the same rainstorm - water level situations, because it is more sensitive to the once-in-a-century co-occurrence event than other stations. A HEC-RAS (The Hydrologic Engineering Center (HEC) developed the River Analysis System (RAS) to aid hydraulic engineers in channel flow analysis and floodplain determination) simulation demonstrated that the occurrence probability of hurricane Gustav induced rainfall is more than that of 100-year rainfall events and this type of storm rainfall would highly likely occur near the Mountain Island Dam again under the future warming conditions by the conditional prediction of Copula function. Insights gained suggest that it is critical to evaluate the risk of dam failures regarding either extreme weather conditions or potential environmental concerns under the climate change scenarios, especially where human lives are threatened.

The role of sediment-induced light attenuation on primary production during Hurricane Gustav (2008)

Abstract. We introduced a sediment-induced light attenuation algorithm into a biogeochemical model of the Coupled Ocean–Atmosphere–Wave–Sediment Transport (COAWST) modeling system. A fully coupled ocean–atmospheric–sediment–biogeochemical simulation was carried out to assess the impact of sediment-induced light attenuation on primary production in the northern Gulf of Mexico during the passage of Hurricane Gustav in 2008. When compared with model results without sediment-induced light attenuation, our new model showed a better agreement with satellite data on both the magnitude of nearshore chlorophyll concentration and the spatial distribution of offshore bloom. When Hurricane Gustav approached, resuspended sediment shifted the inner shelf ecosystem from a nutrient-limited one to a light-limited one. Only 1 week after Hurricane Gustav's landfall, accumulated nutrients and a favorable optical environment induced a posthurricane algal bloom in the top 20 m of the water column, while the productivity in the lower water column was still light-limited due to slow-settling sediment. Corresponding with the elevated offshore NO3 flux (38.71 mmol N m−1 s−1) and decreased chlorophyll flux (43.10 mg m−1 s−1), the outer shelf posthurricane bloom should have resulted from the cross-shelf nutrient supply instead of the lateral dispersed chlorophyll. Sensitivity tests indicated that sediment light attenuation efficiency affected primary production when sediment concentration was moderately high. Model uncertainties due to colored dissolved organic matter and parameterization of sediment-induced light attenuation are also discussed.

Simulation and Prediction of Storm Surges and Waves Using a Fully Integrated Process Model and a Parametric Cyclonic Wind Model

AbstractThis paper presents a fully integrated coastal process model and a simple parametric cyclonic wind‐pressure model for simulation of wind, storm surges, waves, tidal currents, and river flows. By sharing one computational grid within all those process modules and no need for switching executable codes from one module to another, this full‐coupling feature eliminates possible errors and loss of information due to interpolation and extrapolation of variables between different grids. To generate better cyclonic wind speed and barometric pressure, this parametric wind model includes nonlinear decay effect on wind intensity after hurricane's landfall. By implementing a new wind energy source term, the wave action model is capable of computing wave growth, propagation, and deformation through a regional‐scale domain from deepwater to shallow waters. Model validation and model skill assessment were performed by hindcasting wind, storm surges, waves, and river flows during Hurricane Gustav (2008) by using a high‐resolution grid covering the northern Gulf Coast. With improved wind fields estimated by the new parametric wind model, this fully integrated process model produced high‐quality wavefields in deep and shallow waters and storm tidal levels in the northern Gulf Coasts. Because of computing efficiency provided by seamless integration of process modules and optimized numerical solution schemes, faster‐than‐real‐time predictions of storm surges for the advisories during Hurricane Isaac (2012) were achieved by running the validated model in a desktop computer.

Hurricane sedimentation in a subtropical salt marsh-mangrove community is unaffected by vegetation type

Hurricanes periodically deliver sediment to coastal wetlands, such as those in the Mississippi River Delta Complex (MRDC), slowing elevation loss and improving resilience to sea-level rise. However, the amount of hurricane sediment deposited and retained in a wetland may vary depending on the dominant vegetation. In the subtropical climate of the MRDC, the black mangrove (Avicennia germinans) has been expanding and replacing salt marsh (Spartina alterniflora). Because these vegetation types differ in structure, their influence on sedimentation may also differ. We conducted a survey along 160 km of coastline to determine if the spatial deposition pattern in saline wetlands by Hurricanes Gustav and Ike in September 2008 was differentially influenced by vegetation type. Sampling was initiated two months after landfall at eighteen sites in the MRDC containing side-by-side stands of A. germinans and S. alterniflora along the shoreline, with S. alterniflora marsh landward. Average thickness of hurricane sediment across sites varied from 0.6 to 5.6 cm with an overall mean of 2.6 ± 0.4 cm. Within sites, hurricane-layer thickness varied from 1.3 cm at the shoreline to 4.8 cm in the marsh interior, but this pattern was unaffected by vegetation type. Despite greater canopy height, stem density (including pneumatophores), and leaf area, mangroves did not capture more hurricane sediment than salt marsh nor did they attenuate the delivery of sediment to the marsh interior. Data recorded at thirty-six monitoring stations in Louisiana's Coastwide Reference Monitoring System further showed that rates of accretion, as well as elevation change, in saline wetlands (S. alterniflora) of the MRDC were temporarily increased by Hurricanes Gustav and Ike. These findings agree with previous work showing the beneficial effects of hurricane sediments on coastal wetlands, but suggest that a climate-driven shift from S. alterniflora to A. germinans in the MRDC will not necessarily alter hurricane sediment capture.

Mapping 30 Years of Change in the Marshlands of Breton Sound Basin (Southeastern Louisiana, U.S.A.): Coastal Land Area and Vegetation Green Cover

Potter, C. and Amer, R., 2020. Mapping 30 years of change in the marshlands of Breton Sound basin (southeastern Louisiana, U.S.A.): Coastal land area and vegetation green cover. Journal of Coastal Research, 36(3), 437–450. Coconut Creek (Florida), ISSN 0749-0208.This study analyzes the 30-year record of Landsat satellite imagery to better understand the patterns and processes of land loss/gain and recent changes in marshland vegetation green cover in coastal wetlands of Breton Sound basin of southeastern Louisiana. Impacted by both Hurricane Katrina in 2005 and Hurricane Gustav in 2008, this vast estuary area just south of New Orleans was mapped at 30 m resolution in 5-year intervals from 1985 to 2017 using the Landsat Normalized Difference Water Index (NDWI) and the Normalized Difference Vegetation Index (NDVI). Results revealed an entirely new picture of marshland change prior to Hurricanes Katrina and Gustav in the Breton Sound basin. Following decades of extensive wetland loss resulting largely from gas and oil well drilling and canal construction, this analysis estimated gains in land area between 1985 and 2005 (pre-Katrina) of 247 km2 across all subbasins of Breton Sound. The largest proportional increases in marshland areas were mapped from dNDWI analysis in the subbasins of Bayou la Loutre, Bayou Pointe-en-Pointe, and Bayou Terre Aux Boeufs, all surrounding the outer Mississippi River Gulf Outlet Canal. Brackish salinity areas were among the first of Louisiana's coastal wetlands to succumb to the hurricane storm surges of 2005 and 2008, as Landsat dNDWI analysis estimated that about 245 km2 of wetlands in the Breton Sound basin were lost to open water from the impacts of Hurricanes Katrina and Gustav. However, combined dNDWI and dNDVI analysis indicated that gains in marshland area and green vegetation cover have occurred at a yearly rate of increase after 2008 comparable to the period between 1985 and 2005. Specific areas of rapid land gain were detected in River aux Chenes and Bayou Bienvenue subbasins, and Bayou Plaquemines and Bayou la Loutre in brackish to saltwater marshland types on the outer margins of Breton Sound basin.

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.

Numerical reconstruction of the intense precipitation and moisture transport fields for six tropical cyclones affecting the eastern United States

Tropical cyclones (TCs) are intense atmospheric vortices that form over the warm tropical oceans. They are recognized for their ability to generate intense precipitation that may in turn create disastrous floods. This article first assesses the suitability of a regional atmospheric model, the Weather Research and Forecasting (WRF) model, to simulate the intense precipitation depth (PD) fields of six North Atlantic TCs that affected the eastern United States during 2002–2016. Due to the strong nonlinearity involved in tropical cyclones' dynamics and thermodynamics, which causes tropical cyclones' tracks to be very sensitive to the different modeling choices, placing the PD fields in the observed locations was challenging. This involved trying several simulation start dates and combinations of the WRF model's parameterization schemes for each storm simulated. Model performance was evaluated by comparing the simulated PD fields with the observed PD fields obtained from the NCEP Stage IV precipitation dataset. In addition to qualitative comparisons, three quantitative metrics were used to quantify the WRF model performance in simulating a PD field's location, structure and intensity. The sensitivity of the simulation results to the choice of the parameterization schemes was then illustrated using Hurricane Gustav (2008). Eventually, the most satisfactory simulations were used to investigate the mechanisms responsible for the generation of intense precipitation in these TCs. More specifically, the vertically integrated vapor transport field and its divergence were calculated using the model outputs, and it was found that horizontal moisture convergence played a central role in the generation of intense precipitation in these TCs.

ASSESSMENT OF THE EVOLUTION OF STORM SURGE IN COASTAL LOUISIANA

The Louisiana coastal landscape comprises an intricate system of fragmented wetlands, natural ridges, man-made navigation canals, flood protection and oil and gas infrastructure. Louisiana lost approximately 1,883 square miles (4,877 sq km) of coastal wetlands from 1932 to 2010 including 300 square miles (777 sq km) lost between 2004 and 2008 due to Hurricanes Katrina, Rita, Gustav and Ike (Couvillion et al., 2011). A projected additional 2,250 square miles (5,827 sq km) of coastal wetlands will be lost over the next 50 years if no preventative actions are taken (Coastal Protection and Restoration Authority of Louisiana, 2017). Storm surge models representing historical eras of the Louisiana coastal landscape can be developed to investigate the response of hurricane storm surge (e.g. peak water levels, inundation volume and time) to land loss and vegetative changes. Land:Water (L:W) isopleths (Gagliano et al., 1970; Twilley et al., 2016; Siverd et al., 2018) have been calculated along the Louisiana coast from Sabine Lake to the Pearl River. These isopleths were utilized to develop a simplified coastal landscape (bathymetry, topography, bottom roughness) representing circa2010. Similar methods are employed with the objective of developing storm surge models that represent the coastal landscape for past eras (circa1890, c.1930, c.1970).

MORPHOLOGICAL MODELING OF LOW-DUNE BARRIER HEADLAND SYSTEM CHANGES DUE TO HURRICANE FORCING

Coastal barrier landforms serve as the first line of defense against oceanic and meteorological forces. Landward infrastructure and ecosystems, without these barriers, would be significantly more at risk to the flooding and wave forcing caused by extreme storms. Widespread recognition of this function has prompted coastal managers to adopt systematic restoration programs. As an exemplar, the Caminada Headlands (CH) Beach and Dune Restoration Project, located adjacent Port Fourchon, Louisiana (LA), USA cost an estimated $220 million USD and restored ~22.5 kilometers of coastline with a 6.4 million m3 sediment placement. Insight into the performance of the CH restoration during future hurricane impacts requires an understanding of the system’s response to historical storms. In general, the CH experiences high background shoreline erosion rates. Recent historical averages are on the order of 15 m yr-1 [Byres et al., 2017]. This rate may double during active tropical storm seasons, e.g. the year of hurricane Katrina (2005) [Byres et al., 2017] and, at the event time-scale, localized erosion rates spike dramatically as shorelines may translate 100s of meters landward due to dune overwashing and breaching. Calibration of realistic process based morphological models that can accurately simulate these effects require extensive, high fidelity input data. To achieve this end, this study makes use of several monitoring projects in the LA region while employing a coupled XBeach and Delft3D modeling system to simulate the impact of hurricane Gustav (2008) on the CH.

A Fiscally Based Scale for Tropical Cyclone Storm Surge

AbstractCategorization of storm surge with the Saffir–Simpson hurricane scale has been a useful means of communicating potential impacts for decades. However, storm surge was removed from this scale following Hurricane Katrina (2005), leaving no scale-based method for storm surge risk communication despite its significant impacts on life and property. This study seeks to create a new, theoretical storm surge scale based on fiscal damage for effective risk analysis. Advanced Circulation model simulation output data of maximum water height and velocity were obtained for four storms: Hurricane Katrina, Hurricane Gustav, Hurricane Ike, and Superstorm Sandy. Four countywide fiscal loss methods were then considered. The first three use National Centers for Environmental Information Storm Events Database (SED) property damages and Bureau of Economic Analysis (BEA) population, per capita personal income, or total income. The fourth uses National Flood Insurance Program total insured coverage and paid claims. Initial correlations indicated the statistical mode of storm surge data above the 90th percentile was most skillful; this metric was therefore chosen to represent countywide storm surge. Multiple linear regression assessed the most skillful combination of storm surge variables (height and velocity) and fiscal loss method (SED property damages and BEA population, i.e., loss per capita), and defined the proposed scale, named the Kuykendall scale. Comparison with the four storms’ actual losses shows skillful performance, notably a 20% skill increase over surge height-only approaches. The Kuykendall scale demonstrates promise for skillful future storm surge risk assessment in the analytical, academic, and operational domains.

Numerical study of sediment dynamics during hurricane Gustav

In this study, the coupled ocean-atmosphere-wave-and-sediment transport (COAWST) modeling system was employed to explore sediment dynamics in the northern Gulf of Mexico during hurricane Gustav in 2008. The performance of the model was evaluated quantitatively and qualitatively against in-situ and remote sensing measurements, respectively. After Gustav's landfall in coastal Louisiana, the maximum significant wave heights reached more than 8 m offshore and they decreased quickly as it moved toward the inner shelf, where the vertical stratification was largely destroyed. Alongshore currents were dominant westward on the eastern sector of the hurricane track, and offshoreward currents prevailed on the western sector. High suspended sediment concentrations (>1000 mg/l) were confined to the inner shelf at surface layers and the simulated high concentrations at the bottom layer extended to the 200 m isobaths. The stratification was restored one week after landfall, although not fully. The asymmetric hurricane winds induced stronger hydrodynamics in the eastern sector, which led to severe erosion. The calculated suspended sediment flux (SSF) was convergent to the hurricane center and the maximum SSF was simulated near the south and southeast of the Mississippi river delta. The averaged post-hurricane deposition over the Louisiana shelf was 4.0 cm, which was 3.2–26 times higher than the annual accumulation rate under normal weather conditions.