A comparison between measured wave properties and simple wave hindcasting models in shallow water

Significant wave heights and wave periods obtained from field measurements in Lake Balaton, Hungary, were compared with two versions of the shallow water wave hindcasting model published by the U.S. Army Corps of Engineers. The version presented in CERC [3, 4] was found to give very good hindcasts of wave height but fall —20% low on wave period. The model presented in CERC [5] was 15-20% above the earlier version at long fetches and approximately equivalent at shorter fetches

A comparison of the nonlinear frictional characteristics of two-dimensional and three-dimensional models of a shallow tidal embayment

The nonlinear frictional behavior of two-dimensional (2-D) and three-dimensional (3-D) models are compared in this study of tides in the Bight of Abaco. The shallow depths and the existence of an extensive set of tidal elevation data (five astronomical and two overtide constituents at 25 stations) from Filloux and Snyder (1979) offer an excellent opportunity to compare the effects of different frictional formulations. In addition, previous modeling efforts in the bight have consistently overpredicted the M6and generally overdamped the O1, K1, and S2tides. The results indicate that although the 2-D and 3-D models may be calibrated to produce nearly identical responses for the dominant M2tide, there are systematic differences in the responses of the primary overtides. These differences are explained using analytical expansions of the friction terms and are shown to be due to differences in the terms that are nonlinear in velocity and in water level. The investigation concludes that the overgeneration of M6and the overdamping of secondary astronomical tides will occur in 3-D models as well as 2-D models. Although several causes for these problems were considered, improvement in these constituents could be achieved only by modifying the standard quadratic friction or flow-dependent eddy viscosity relations to reduce the nonlinear frictional effect relative to the linear frictional effect. The required modifications suggest the presence of a constant background velocity, residual turbulence field, or possibly the need for a more advanced frictional closure

U.S. IOOS coastal and ocean modeling testbed: Evaluation of tide, wave, and hurricane surge response sensitivities to mesh resolution and friction in the Gulf of Mexico: IOOS TESTBED-RESOLUTION AND FRICTION

This paper investigates model response sensitivities to mesh resolution, topographical details, bottom friction formulations, the interaction of wind waves and circulation, and nonlinear advection on tidal and hurricane surge and wave processes at the basin, shelf, wetland, and coastal channel scales within the Gulf of Mexico. Tides in the Gulf of Mexico are modestly energetic processes, whereas hurricane surge and waves are highly energetic. The unstructured-mesh, coupled wind-wave and circulation modeling system, SWAN+ ADCIRC, is implemented to generate modeled tidal harmonic constituents and hurricane waves and surge for a Hurricane Ike (2008) hindcast. In the open ocean, mesh resolution requirements are less stringent in achieving accurate tidal signals or matching hurricane surge and wave responses; however, coarser resolution or the absence of intertidal zones decreases accuracy along protected nearshore and inland coastal areas due to improper conveyance and/or lateral attenuation. Bottom friction formulations are shown to have little impact on tidal signal accuracy, but hurricane surge is much more sensitive, especially in shelf waters, where development of a strong shore-parallel current is essential to the development of Ike's geostrophic setup. The spatial and temporal contributions of wave radiation stress gradients and nonlinear advection were charted for Ike. Nonlinear advection improves model performance by capturing an additional 10―20 cm of geostrophic setup and increasing resonant cross-shelf waves by 30―40 cm. Wave radiation stress gradients improve performance at coastal stations by adding an extra 20―40 cm to water levels

Scalability of an Unstructured Grid Continuous Galerkin Based Hurricane Storm Surge Model

This paper evaluates the parallel performance and scalability of an unstructured grid Shallow Water Equation (SWE) hurricane storm surge model. We use the ADCIRC model, which is based on the generalized wave continuity equation continuous Galerkin method, within a parallel computational framework based on domain decomposition and the MPI (Message Passing Interface) library. We measure the performance of the model run implicitly and explicitly on various grids. We analyze the performance as well as accurracy with various spatial and temporal discretizations. We improve the output writing performance by introducing sets of dedicated writer cores. Performance is measured on the Texas Advanced Computing Center Ranger machine. A high resolution 9,314,706 finite element node grid with 1s time steps can complete a day of real time hurricane storm surge simulation in less than 20 min of computer wall clock time, using 16,384 cores with sets of dedicated writer cores

A Once and Future Gulf of Mexico Ecosystem: Restoration Recommendations of an Expert Working Group

The Deepwater Horizon (DWH) well blowout released more petroleum hydrocarbons into the marine environment than any previous U.S. oil spill (4.9 million barrels), fouling marine life, damaging deep sea and shoreline habitats and causing closures of economically valuable fisheries in the Gulf of Mexico. A suite of pollutants — liquid and gaseous petroleum compounds plus chemical dispersants — poured into ecosystems that had already been stressed by overfishing, development and global climate change. Beyond the direct effects that were captured in dramatic photographs of oiled birds in the media, it is likely that there are subtle, delayed, indirect and potentially synergistic impacts of these widely dispersed, highly bioavailable and toxic hydrocarbons and chemical dispersants on marine life from pelicans to salt marsh grasses and to deep-sea animals. As tragic as the DWH blowout was, it has stimulated public interest in protecting this economically, socially and environmentally critical region. The 2010 Mabus Report, commissioned by President Barack Obama and written by the secretary of the Navy, provides a blueprint for restoring the Gulf that is bold, visionary and strategic. It is clear that we need not only to repair the damage left behind by the oil but also to go well beyond that to restore the anthropogenically stressed and declining Gulf ecosystems to prosperity-sustaining levels of historic productivity. For this report, we assembled a team of leading scientists with expertise in coastal and marine ecosystems and with experience in their restoration to identify strategies and specific actions that will revitalize and sustain the Gulf coastal economy. Because the DWH spill intervened in ecosystems that are intimately interconnected and already under stress, and will remain stressed from global climate change, we argue that restoration of the Gulf must go beyond the traditional “in-place, in-kind” restoration approach that targets specific damaged habitats or species. A sustainable restoration of the Gulf of Mexico after DWH must: 1. Recognize that ecosystem resilience has been compromised by multiple human interventions predating the DWH spill; 2. Acknowledge that significant future environmental change is inevitable and must be factored into restoration plans and actions for them to be durable; 3. Treat the Gulf as a complex and interconnected network of ecosystems from shoreline to deep sea; and 4. Recognize that human and ecosystem productivity in the Gulf are interdependent, and that human needs from and effects on the Gulf must be integral to restoration planning. With these principles in mind, we provide the scientific basis for a sustainable restoration program along three themes: 1. Assess and repair damage from DWH and other stresses on the Gulf; 2. Protect existing habitats and populations; and 3. Integrate sustainable human use with ecological processes in the Gulf of Mexico. Under these themes, 15 historically informed, adaptive, ecosystem-based restoration actions are presented to recover Gulf resources and rebuild the resilience of its ecosystem. The vision that guides our recommendations fundamentally imbeds the restoration actions within the context of the changing environment so as to achieve resilience of resources, human communities and the economy into the indefinite future

Once and Future Gulf of Mexico Ecosystem: Restoration Recommendations of an Expert Working Group

The Deepwater Horizon (DWH) well blowout released more petroleum hydrocarbons into the marine environment than any previous U.S. oil spill (4.9 million barrels), fouling marine life, damaging deep sea and shoreline habitats and causing closures of economically valuable fisheries in the Gulf of Mexico. A suite of pollutants—liquid and gaseous petroleum compounds plus chemical dispersants—poured into ecosystems that had already been stressed by overfishing, development and global climate change. Beyond the direct effects that were captured in dramatic photographs of oiled birds in the media, it is likely that there are subtle, delayed, indirect and potentially synergistic impacts of these widely dispersed, highly bioavailable and toxic hydrocarbons and chemical dispersants on marine life from pelicans to salt marsh grasses and to deep-sea animals. As tragic as the DWH blowout was, it has stimulated public interest in protecting this economically, socially and environmentally critical region. The 2010 Mabus Report, commissioned by President Barack Obama and written by the secretary of the Navy, provides a blueprint for restoring the Gulf that is bold, visionary and strategic. It is clear that we need not only to repair the damage left behind by the oil but also to go well beyond that to restore the anthropogenically stressed and declining Gulf ecosystems to prosperity-sustaining levels of historic productivity. For this report, we assembled a team of leading scientists with expertise in coastal and marine ecosystems and with experience in their restoration to identify strategies and specific actions that will revitalize and sustain the Gulf coastal economy. Because the DWH spill intervened in ecosystems that are intimately interconnected and already under stress, and will remain stressed from global climate change, we argue that restoration of the Gulf must go beyond the traditional "in-place, in-kind" restoration approach that targets specific damaged habitats or species. A sustainable restoration of the Gulf of Mexico after DWH must: 1. Recognize that ecosystem resilience has been compromised by multiple human interventions predating the DWH spill; 2. Acknowledge that significant future environmental change is inevitable and must be factored into restoration plans and actions for them to be durable; 3. Treat the Gulf as a complex and interconnected network of ecosystems from shoreline to deep sea; and 4. Recognize that human and ecosystem productivity in the Gulf are interdependent, and that human needs from and effects on the Gulf must be integral to restoration planning. With these principles in mind, the authors provide the scientific basis for a sustainable restoration program along three themes: 1. Assess and repair damage from DWH and other stresses on the Gulf; 2. Protect existing habitats and populations; and 3. Integrate sustainable human use with ecological processes in the Gulf of Mexico. Under these themes, 15 historically informed, adaptive, ecosystem-based restoration actions are presented to recover Gulf resources and rebuild the resilience of its ecosystem. The vision that guides our recommendations fundamentally imbeds the restoration actions within the context of the changing environment so as to achieve resilience of resources, human communities and the economy into the indefinite future

Heightened hurricane surge risk in northwest Florida revealed from climatological-hydrodynamic modeling and paleorecord reconstruction

Historical tropical cyclone (TC) and storm surge records are often too limited to quantify the risk to local populations. Paleohurricane sediment records uncover long-term TC activity, but interpreting these records can be difficult and can introduce significant uncertainties. Here we compare and combine climatological-hydrodynamic modeling (including a method to account for storm size uncertainty), historical observations, and paleohurricane records to investigate local surge risk, using Apalachee Bay in northwest Florida as an example. The modeling reveals relatively high risk, with 100 year, 500 year, and “worst case” surges estimated to be about 6.3 m, 8.3 m, and 11.3 m, respectively, at Bald Point (a paleorecord site) and about 7.4 m, 9.7 m, and 13.3 m, respectively, at St. Marks (the head of the Bay), supporting the inference from paleorecords that Apalachee Bay has frequently suffered severe inundation for thousands of years. Both the synthetic database and paleorecords contain a much higher frequency of extreme events than the historical record; the mean return period of surges greater than 5 m is about 40 years based on synthetic modeling and paleoreconstruction, whereas it is about 400 years based on historical storm analysis. Apalachee Bay surge risk is determined by storms of broad characteristics, varies spatially over the area, and is affected by coastally trapped Kelvin waves, all of which are important features to consider when accessing the risk and interpreting paleohurricane records. In particular, neglecting size uncertainty may induce great underestimation in surge risk, as the size distribution is positively skewed. While the most extreme surges were generated by the uppermost storm intensities, medium intensity storms (categories 1–3) can produce large to extreme surges, due to their larger inner core sizes. For Apalachee Bay, the storms that induced localized barrier breaching and limited sediment transport (overwash regime; surge between 3 and 5 m) are most likely to be category 2 or 3 storms, and the storms that inundated the entire barrier and deposited significantly more coarse materials (inundation regime; surge > 5 m) are most likely to be category 3 or 4 storms.United States. National Oceanic and Atmospheric Administration (Grant NA11OAR4310101)National Science Foundation (U.S.) (Grant OCE-0903020)National Science Foundation (U.S.) (Grant OCE-1250506

Hurricane Gustav (2008) Waves and Storm Surge: Hindcast, Synoptic Analysis, and Validation in Southern Louisiana

Hurricane Gustav (2008) made landfall in southern Louisiana on 1 September 2008 with its eye never closer than 75 km to New Orleans, but its waves and storm surge threatened to flood the city. Easterly tropical-storm-strength winds impacted the region east of the Mississippi River for 12-15 h, allowing for early surge to develop up to 3.5 m there and enter the river and the city's navigation canals. During landfall, winds shifted from easterly to southerly, resulting in late surge development and propagation over more than 70 km of marshes on the river's west bank, over more than 40 km of Caernarvon marsh on the east bank, and into Lake Pontchartrain to the north. Wind waves with estimated significant heights of 15 m developed in the deep Gulf of Mexico but were reduced in size once they reached the continental shelf. The barrier islands further dissipated the waves, and locally generated seas existed behind these effective breaking zones. The hardening and innovative deployment of gauges since Hurricane Katrina (2005) resulted in a wealth of measured data for Gustav. A total of 39 wind wave time histories, 362 water level time histories, and 82 high water marks were available to describe the event. Computational models-including a structured-mesh deepwater wave model (WAM) and a nearshore steady-state wave (STWAVE) model, as well as an unstructured-mesh "simulating waves nearshore'' (SWAN) wave model and an advanced circulation (ADCIRC) model-resolve the region with unprecedented levels of detail, with an unstructured mesh spacing of 100-200 m in the wave-breaking zones and 20-50 m in the small-scale channels. Data-assimilated winds were applied using NOAA's Hurricane Research Division Wind Analysis System (H*Wind) and Interactive Objective Kinematic Analysis (IOKA) procedures. Wave and surge computations from these models are validated comprehensively at the measurement locations ranging from the deep Gulf of Mexico and along the coast to the rivers and floodplains of southern Louisiana and are described and quantified within the context of the evolution of the storm