Search

Whitehead, S.J.; Yeager, K.M.; Feagin, R.A.; Huff, T.P.; Paine, J.G.; Schindler, K.S., and Dixon, T.S., 2024. Growth fault–induced effects on tidal marsh surficial processes and landscape conversion in the Slop Bowl, Brazoria National Wildlife Refuge, Texas. Journal of Coastal Research, 40(1), 64–79. Charlotte (North Carolina), ISSN 0749-0208. The Slop Bowl marsh, located in the Brazoria National Wildlife Refuge on the Texas coast, is an anthropogenically influenced tidal marsh setting that has experienced rapid rates of landscape conversion and loss over the last ∼70 years. This tidal marsh has been affected by recently active faults and several hydrologic barriers (roads, pipeline channels, and active hydrocarbon-extraction well pads). Geophysical field methods and sedimentological analyses were conducted to better understand the effects of these developments on marsh surficial processes. Lithostratigraphy, shallow geophysical data, GPS surveys, radionuclide dating, and organic matter analyses all exhibited influences connected to growth-fault motion. The location and activity of a major growth fault were identified as contributing to subsidence on the downthrown fault block and causing vertical displacement of the marsh surface. Fault motion, in conjunction with the construction of roads, has disrupted the natural hydrologic pathways that once existed. Their combined effects resulted in transition of the land cover over the past several decades from a saline coastal prairie to a tidal marsh–dominant landscape, with continued future submergence anticipated. As the natural laboratory of the Slop Bowl demonstrates, anthropogenic development, neotectonics, and hydrocarbon extraction can have outsized effects on sedimentation processes, with implications for the long-term sustainability of coastal wetland environments in the northern Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Coastal Research is the property of KnowledgeWorks Global, Ltd and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Bazgirkhoob, H.; Linhoss, A., and Armandei, M., 2022. A numerical tool for dissolved oxygen simulation in the western Mississippi Sound. Journal of Coastal Research, 38(4), 699–711. Coconut Creek (Florida), ISSN 0749-0208. Dissolved oxygen is an indicator of aquatic health. Hydrodynamic–water quality models facilitate the understanding of flow dynamics and dissolved oxygen in estuarine systems. In this study, dissolved oxygen concentration, seasonality, and vertical stratification were studied in the western Mississippi Sound, Northern Gulf of Mexico. Visual Environmental Fluid Dynamic Code and the water quality model CE-QUAL-ICM were linked together to develop a three-dimensional hydrodynamic and water quality model of the western Mississippi Sound. The model was verified and validated for nutrients and chlorophyl a. Then, the modeled results for dissolved oxygen were compared to measured data. Mean observed dissolved oxygen ranged between 6.29 and 8.48 mg/L in the top and bottom layers at each site. The root mean squared error between measured and modeled dissolved oxygen ranged between 1.30 and 2.87 mg/L. Results indicate that the model was able to capture measured seasonal trends and vertical stratification. The model simulated more realistic results in shallower areas compared to deeper areas. Overall, the model simulated slightly higher dissolved oxygen than what was measured, although 27% of the stations showed no statistical difference between the modeled and measured dissolved oxygen. These results are useful for interpreting the value of this model for future ecological studies. The model can be used as a tool to provide better understanding of the dissolved oxygen dynamics due to multiple scenarios such as hurricanes and storms. [ABSTRACT FROM AUTHOR]

Yue, L.; Wang, Q.; Wang, W.; Wang, Y., and Lv, J., 2020. Numerical simulation analysis of the characteristics of torpedo anchor penetration in cohesive soil. In: Wan, Z. (ed.), Coordinated Sustainable Development in Coastal Areas: Environment and Economy. Journal of Coastal Research, Special Issue No. 109, pp. 139–144. Coconut Creek (Florida), ISSN 0749-0208. Invented by Petrobras in 1996, the torpedo anchor has been successfully applied in Floating Production Storage and Offloading (FPSO) in the Gulf of Mexico (Medeiros, 2002). With a torpedo-like hydrodynamic shape, the torpedo anchor obtains the kinetic energy required for penetration by free-falling through the water. It then uses that energy to penetrate into the seabed, thereby completing its installation. This paper discusses the large deformation finite element method and the CEL method, which are used to calculate the torpedo anchor penetration in a cohesive-soil seabed. The characteristics of the soil and the anchor at different moments during the torpedo anchor penetration are analyzed based on simulation results. [ABSTRACT FROM AUTHOR]

Wang, P.; Adam, J.D.; Cheng, J., and Vallée, M., 2020. Morphological and sedimentological impacts of Hurricane Michael along the northwest Florida coast. Journal of Coastal Research, 36(5), 932–950. Coconut Creek (Florida), ISSN 0749-0208. On October 10, 2018, category 5 Hurricane Michael made landfall at Mexico Beach, generating a nearly 5-m storm surge. The greater landfall area is characteristic of a cuspate headland protruding into the Gulf of Mexico for up to 50 km. The headland is composed of several barrier islands with different orientations fronting a large estuary. The hurricane-impacted areas include densely developed small beachfront communities, modestly to sparsely developed shoreline communities, mostly pristine state parks, and a completely pristine national wildlife refuge. Therefore, Hurricane Michael provides an excellent opportunity to study the impact of an extreme storm over various coastal environments with different degrees of human developments. Because of the shoreline orientation and bathymetry changes induced by the headland, the wave field associated with the hurricane is complicated, with different locations for the highest wave and the landfall site where the surge and wind speed were the greatest. Numerical wave modeling revealed two wave-focusing points along the headland where barrier-island breaching occurred. Beach-dune erosion and impact to infrastructure were examined and compared among various natural–human coastal systems. The magnitude of dune erosion was mostly controlled by the storm wave height and prestorm beach width, but the height of the prestorm dune was not a determining factor. Sedimentological characteristics of storm deposits along the barrier islands, within Apalachicola Bay, and in the surrounding coastal marsh were examined using 116 sediment cores and 40 grab sediment samples. Characteristics of storm deposits and their preservation are described for various subenvironments, including beaches, dunes, interior wetlands, back-barrier bay, and coastal marsh along the landward side of the estuary. The landward penetrations of identifiable sandy overwash deposits were less than 150 m along the barrier islands and less than 30 m along the mainland marshes. These results should have potential implications on paleostorm study. [ABSTRACT FROM AUTHOR]

Cheng, J. and Wang, P., 2019. Unusual beach changes induced by Hurricane Irma with a negative storm surge and poststorm recovery. Journal of Coastal Research, 35(6), 1185–1199. Coconut Creek (Florida), ISSN 0749-0208. The coast of west-central Florida, facing the Gulf of Mexico, experienced Hurricane Irma with a negative surge of 1.1 m and a highly oblique northerly approaching wave in September 2017. This unusual hydrodynamic condition provides an opportunity to investigate the effect of surge and incident wave direction on morphology changes. Beach profiles, spaced at 300 m apart, along a 15-km stretch of beach were surveyed 2 weeks prior to the passage of Hurricane Irma and 1 week after and continued for up to 5 months after the passage to obtain Irma-induced erosion as well as post-Irma recovery. Owing to the occurrence of negative surge, the profile volume of the dune field remained mostly stable. The majority of beach erosion occurred below mean sea level, with a considerable amount of sediment transported seaward of the depth of closure. This is opposite to the conservation of beach profile volume above depth of closure under several earlier storms with a positive surge. The alongshore variation of overall beach profile volume erosion demonstrates a southward decreasing trend, due to a southward decreasing wave height as controlled by the northerly incident wave. After the passage of Irma, minor beach volume recovery occurred during the calm period of the fall season. Opposite to the typical erosive beach in winter, the most substantial beach accretion and onshore bar movement were observed during the following peak winter season as beach/bar evolved toward equilibrium. The profile volume in the dry beach region experienced a complete recovery in the first 5 months after Hurricane Irma. Shoreline change is a valid proxy for beach volume change during both the erosive and the recovery phase of Irma. The systematically measured beach profiles provide a solid dataset to calibrate process-based models to study beach morphodynamics. [ABSTRACT FROM AUTHOR]

Ragan, A.N. and Wozniak, J.R., 2019. Linking hydrologic connectivity in salt marsh ponds to fish assemblages across a heterogenous coastal habitat. Journal of Coastal Research, 35(3), 545–558. Coconut Creek (Florida), ISSN 0749-0208. In estuarine systems, inundation regime plays a vital role in shaping the physical and chemical characteristics of salt marsh ponds. Along the Texas Gulf Coast, salt marsh ponds are scattered across the coastal marsh landscape, with each pond possessing a varying degree of hydrological connectivity to adjacent estuarine waters. The timing, frequency, and magnitude of connection events can directly influence both the abiotic and biotic components of the ponds. To determine how the degree of hydrological connectivity impacts these systems, discriminant function analysis (DFA) was used to test the ability of environmental variables (e.g., pond size, vegetation, soil type, water column salinity, pH, dissolved oxygen, etc.), fish presence–absence data, and fish relative abundances to predict the level of connectivity of a subset of ponds. In addition, canonical correspondence analysis (CCA) was used to determine whether fish assemblage data (collected via seine and minnow traps) could determine whether pond conditions affect the composition of fish assemblages. Results from the DFA for environmental parameters showed that the model classified ponds correctly to their a priori connectivity classifications; however, no more accurately than random chance. Fish presence–absence data were the least accurate for predicting degree of connectivity, but the relative abundances of those species proved to be an accurate method for pond connectivity classification. Many efforts to understand how an altered hydroperiod impacts marsh complexes along the Texas Gulf Coast have focused on tidal creeks and the vegetated portions of open marshes rather than salt marsh ponds, which can be key habitats for both primary and secondary productivity. This study concentrates on salt marsh ponds to provide a better understanding of how these ecosystems function within the greater marsh landscape. [ABSTRACT FROM AUTHOR]

The temporally incomplete tropical cyclone (TC) observational record limits the understanding of recurrence intervals and the impacts of repeated TCs on coastal ecosystems. Growth of maritime trees near the Gulf of Mexico may be affected by high winds, precipitation, and storm surges from TCs. Proxy records, such as tree growth recorded in annual ring widths, can be used to extend TC records temporally but must be verified with the observational record first. This study develops chronologies of total ring width (TRW), earlywood ring width (ERW), and latewood ring width (LRW) from slash pine (Pinus elliottii var. elliottii Engelm.) trees located 2 km from an open saltwater bay in the Grand Bay National Estuarine Research Reserve in coastal Mississippi, U.S.A. These chronologies are compared with TC storm surge and wind speed records using superposed epoch analysis. The year after a TC occurrence, tree growth is significantly (p < 0.05) suppressed (narrower than average annual growth rings) for TRW, ERW, and LRW with respect to storm surge and shows no statistical significance with high wind speeds. Individual trees display suppression in growth for 1-6 years after TC occurrences. This study demonstrates that slash pine trees in close proximity to salt water can be used to produce chronologies of TC occurrences for the northern Gulf of Mexico region and thus can eventually be used to extended and supplement temporally the existing TC observational record. [ABSTRACT FROM AUTHOR]

Caudle, T.L. and Paine, J.G., 2017. Applications of coastal data collected in the Texas High School Coastal Monitoring Program (THSCMP). The Texas High School Coastal Monitoring Program (THSCMP) engages students and teachers who live along the Gulf of Mexico in the study of their natural environment. Scientists from the Bureau of Economic Geology (BEG) at The University of Texas at Austin show middle and high school students and teachers how to measure topography, map vegetation lines and shorelines with GPS, and observe weather and wave conditions. The students are active participants in the research project, which has the dual benefit of enhancing their science education while providing valuable data on the dynamic coastline. Students collect critical scientific data that help scientists and managers address coastal issues and gain a better understanding of dune and beach dynamics on the Texas coast. Since the THSCMP began in 1997, data collected by students have been applied by scientists to investigate beach, dune, and vegetation-line recovery following several tropical cyclones, including Hurricane Ike in 2008. Student-collected data are used to monitor the effects of nourishment projects on South Padre Island, foredune changes on Mustang Island, geotextile tubes on Galveston Island, and jetty construction on Matagorda Peninsula. Student data are also used in verifying shoreline positions for updates of Texas' long-term shoreline change rates. Through these real-world examples of scientific observations, students gain a better understanding of environmental issues affecting their communities. [ABSTRACT FROM AUTHOR]

An introduction to the issue is presented which discusses the Technical Framework for the Governors' Action Plan for Healthy and Resilient Coasts to promote healthy ecosystems along the Gulf of Mexico coast in the U.S. states of Alabama, Louisiana, Florida, Mississippi, and Texas.

Medina-Gómez, I.; Villalobos-Zapata, G.J., and Herrera-Silveira, J.A., 2015. Spatial and temporal hydrological variations in the inner estuaries of a large coastal lagoon of the southern Gulf of Mexico. Coastal lagoons receive significant inputs from river basins, leading to inner estuaries or fluvial lagoon subsystems subject to the bidirectional flow of energy, organic matter, nutrients, and sometimes toxic materials between river mouths and lagoons. Such exchanges are highly dynamic and enhance lagoon productivity. Terminos Lagoon (TL) is a large coastal lagoon in the southern Gulf of Mexico that has two deep permanent inlets connecting the lagoon to the Gulf and strong riverine input. We evaluated the influence of river discharge on seasonal and spatial patterns of water quality in six fluvial lagoon subsystems in TL. Six bimonthly samplings were carried out from February to December 2001. Temperature, salinity, dissolved oxygen, dissolved inorganic nutrients (nitrate, nitrite, ammonium, soluble reactive phosphorus, and soluble reactive silica), and chlorophyll a were measured. There were large differences between the western and eastern river mouths due to differences in river discharge and the nature of their watersheds ( e.g., land use, size). Furthermore, the influence that the dominant depositional environment and local habitats ( i.e. submerged aquatic vegetation) developing adjacent to these estuarine lagoon subsystems may exert over the nutrient concentrations of the water column is discussed. These differences were more evident during the rainy season when river discharge was highest. It is suggested that the input of N rather than P could have the greatest impact on TL in the future. [ABSTRACT FROM AUTHOR]

Schiller, R.V. and Kourafalou, V.H., 2014. Loop current impact on the transport of Mississippi river waters. River plume studies have traditionally focused on coastal and shelf circulation. Here, we examine novel interactions of a large river plume with offshore flows, which introduces additional export pathways for the riverine waters. We show the impact of the Loop Current System (LCS) on the offshore transport and fate of Mississippi River (MR) plume waters. The high-resolution Northern Gulf of Mexico (NGoM) model, nested in a data-assimilative, regional, Gulf of Mexico model, was employed for a 5-year, realistically forced simulation. Model results, in tandem with satellite data, demonstrate that the entrainment of MR waters by the LCS varies interannually and extends pathways of shelf cross-marginal transport to the basin interior and beyond. Plume-to-LCS interactions are determined by episodic northward intrusions of the LCS in the NGoM. If the intrusion is very close to the MR Delta, plume waters can be entrained with little contribution from winds. If the intrusion is farther offshore and lasts for months, LCS entrainment may be modulated by wind forcing because plume transport can change from an along-shelf to an exclusively across-shelf regime. Seasonal changes in river discharge did not have a direct influence on the transport induced by LCS intrusions. However, high-frequency (daily) variability of the river discharge induced by the Mississippi and 16 other major rivers was important and played a role in the overall NGoM freshwater transport. During the 5-year period, plume-to-LCS interactions corresponded on average to ∼11% of the yearly net offshore freshwater transport near the MR Delta. Model results were supported by satellite and in situ observations that demonstrate the far-reaching potential of MR waters as they are traced to the SE Gulf of Mexico and the Florida Keys. This study demonstrates how across-basin, connectivity pathways for riverine waters may be affected by local coastal-to-offshore interactions induced by a large-scale current system. [ABSTRACT FROM AUTHOR]

Passeri, D.L.; Hagen, S.C.; and Irish, J.L., 2014. Comparison of shoreline change rates along the South Atlantic Bight and Northern Gulf of Mexico coasts for better evaluation of future shoreline positions under sea level rise. Shoreline change rates established by the USGS Coastal Vulnerability Index (CVI) (Thieler and Hammar-Klose, 1999; Thieler and Hammar-Klose, 2000), the USGS National Assessment of Shoreline Change (Morton et al., 2004; Morton and Miller, 2005) and erosion rates estimated using the Bruun Rule (Bruun, 1962) are compared along sandy shorelines of the U.S. South Atlantic Bight and Northern Gulf of Mexico coasts. The intent of the study is not to regard one method better than another, but rather to explore similarities and differences between the methods. Based on the comparison, the following recommendations are offered for quantifying future shoreline positions under sea level rise(SLR). In areas where long-term erosion rates correspond well with rates predicted by the Bruun Rule, shoreline retreat can be assumed to be completely attributed to forces related to SLR and the Bruun Rule can be applied to estimate future shoreline positions under SLR scenarios. If long-term erosion rates are higher than the rates predicted by the Bruun Rule, a hybrid approach can be taken to include a factor for background erosion due to influences other than SLR. Lastly, care should be taken when extrapolating shoreline change rates determined by the CVI or National Assessment of Shoreline Change to predict future shoreline positions. CVI rates may be projected when considering extreme future SLR scenarios, as they are typically larger than the long-term historic rates. [ABSTRACT FROM AUTHOR]

Khalil, S. M.; Finkl, C. W., and Raynie, R. C., 2013. Development of new rRestoration strategies for Louisiana barrier island systems, northern Gulf of Mexico, USA The rapid degradation of Louisiana's barrier island (BI) systems adversely impacts the vitality of strategic economic and biological resources (including aquatic habitat). Louisiana's BI systems have undergone landward migration through BI rollover, area loss and island narrowing as a result of complex interactions among land subsidence, sea-level rise, wave processes, inadequate sediment supply, and intense human disturbance. Consequently, the structural continuity of the BI shorelines has weakened as the islands narrowed, fragmented and, in some cases, submerged. Several multipronged restoration strategies are currently underway to develop effective interdisciplinary restoration projects that mitigate degradation of the Mississippi River delta plain and compensate for coastal land loss. Restoration of the BI systems requires strategies that protect interior wetlands and bolster the first lines of storm defense in a post- Hurricane Katrina-Rita-Gustav-Ike-Isaac and post-Deep Water Horizon era. Coastline degradation would have continued were it not for a series of massive barrier island restoration projects. Such efforts commonly consist of beach nourishment on the Gulfside and marsh creation on the bayside of barrier islands. Regionalizing monitoring, maintenance, and data management efforts support the still evolving scientific and engineering aspects of rebuilding BIs. [ABSTRACT FROM AUTHOR]

The Florida Middle Ground is a complex of north to northwest trending ridges that lie approximately 180 km northwest of Tampa Bay, Florida. The irregular ridges appear on the otherwise gently sloping West Florida shelf and exhibit between 10-15 m of relief. Modern studies interpret the ridges as remnants of a Holocene coral-reef buildup that today provide a hard substrate for growth of a variety of benthic organisms including hydrocorals, scleractinians, alcyonarians, and algae. Recent rotary coring reveals that the core of the eastern ridge of the Florida Middle Ground complex consists of unconsolidated marine calcareous muddy sand that is capped by a boundstone composed primarily of the sessile vermetid gastropod Petaloconchus sp., and overlays a weathered, fossiliferous limestone. Accelerator Mass Spectrometry radiocarbon ages (uncalibrated) on the 3.6-m thick vermetid worm rock indicate that it developed during a sea-level stillstand in the early Holocene (8,225 ± 30-8,910 ± 25 yr B.P.). Our observations suggest that the Florida Middle Ground is a remnant of a series of shore parallel bars that formed in the early Holocene and were capped by a 3.6-m thick unit of vermetid gastropods. During a rapid sea-level rise that began ~8,000 yr B.P. the vermetids growth ceased and the worm rock preserved the ridges structure. Diver observations document that the edges of the ridges are currently being eroded and undermined by biological activity and current action, leading to calving of large capstone blocks. [ABSTRACT FROM AUTHOR]

The Gulf of Mexico (GOM) is a shared ecosystem in which problems and solutions are a common responsibility among governments, primarily the United States and Mexico. Concepts about management of coastal systems suggest that GOM ecosystem-based management approaches should be coupled with ecological risk assessment and that quantitative modeling is a valuable tool for ecosystem-based management, which results in sound sustainable management. Sustainable management requires the consideration of a number of processes and issues. These include definition of ecological regions, description of processes controlling primary productivity, wetland restoration and coastal fisheries, and an understanding that pulsing is a fundamental characteristic of coastal systems, that climate change must be taken into consideration in management, and that environmental sustainability and socioeconomic development are strongly related. Throughout the 6,134 km of coastline stretching from Florida to Quintana Roo, there are several major geographic regions that include the warm-temperate GOM, the tropical GOM, and the Caribbean coast connected to the GOM. Within each geographic region, discrete complex systems can be defined as geographic/hydrological subregions, characterized by the interactions of geology, geomorphology, oceanography, climate, freshwater input, biogeochemistry, coastal vegetation, wildlife, estuary-shelf interactions, and human factors. We conclude: (a) system functioning should serve as a basis for sustainable coastal management; and (b) to sustain environmental and socioeconomic conditions, the GOM must be maintained as a healthy, productive, and resilient ecosystem. The challenge for future coastal management in the GOM should be towards an integration of coastal management with large marine ecosystem management. [ABSTRACT FROM AUTHOR]

The stratigraphy of sections of three barrier island systems in the northeastern Gulf of Mexico (Apalachicola, Mississippi, and Chandeleur) have been mapped using geophysical and coring techniques to assess the influence of geologic variations in barrier lithosomes and adjoining inner shelf deposits on long-term rates of shoreline change at regional and local scales. Regional scale was addressed by comparing average geologic characteristics of the three areas with mean shoreline-change rates for each area. Regionally, differences in sand volume contained within the part of the barrier lithosome above sea level, sand volume on the inner shelf, and to a lesser extent, sediment grain size correlate with shoreline change rates. Larger sand volumes and coarser grain sizes are found where erosion rates are lower. Local scale was addressed by comparing alongshore variations in barrier island and inner shelf geology with alongshore variations in shoreline change. Locally, long-term shoreline change rates are highest directly shoreward of paleovalleys exposed on the inner shelf. While geology is not the sole explanation for observed differences in shoreline change along these three coastal regions, it is a significant contributor to change variability. [ABSTRACT FROM AUTHOR]

The photosynthetic response of many wetland plant species to soil salinity and nutrients has been described in the laboratory, but less is known about the cumulative effect of these abiotic factors in the natural environment. In this investigation we correlated field measurements of chlorophyll fluorescence with simultaneous measurements of soil nitrogen and phosphorus content, soil salinity, and relative leaf nitrogen content in Spartina alterniflora (Loisel), Spartina patens ((Aiton) Muhl), Schoenoplectus californicus ((C.A. Mey.) Steud.) and Schoenoplectus robustus ((Pursh) M.T. Strong), common in brackish and salt marshes of the northwestern Gulf of Mexico. The relationship between chlorophyll fluorescence and soil N : P ratio was not significant in S. alterniflora, nonlinear in S. patens and S. robustus, and significant and positive in S. californicus. The relationship between leaf nitrogen content and effective quantum yield was significant and positive in S. alterniflora and S. robustus, but only S. alterniflora appeared to be able to increase relative leaf nitrogen content over a wide range of soil nutrient and salinity regimes. Schoenoplectus californicus had the greatest potential for photosynthetic light capture but also had the narrowest ecological distribution. Thus, the species best adapted to high levels of abiotic stress (S. alterniflora) was less dominant at lower salinities, and the species with the highest potential for photosynthetic performance (S. robustus and S. californicus) were only found in locations with favorable abiotic conditions. We found that the range of environmental conditions experienced by each species in the field is greater than what has been considered in laboratory investigations. [ABSTRACT FROM AUTHOR]

Dredging activities are a potential source of sediment and should be considered in any conservation and restoration planning process. Wise use of sediment resources from dredging is integral to accomplishing the conservation and restoration initiatives and objectives being recommended under the Gulf of Mexico Alliance. Keeping dredged sediments within the natural system or using it in the construction of restoration projects can improve environmental conditions, provide storm damage protection, and contribute to habitat creation and restoration goals. Hundreds of millions of cubic yards of sediments are dredged each year from Gulf ports, harbors, and waterways, much of which could be used beneficially. Currently it is estimated that about 30% of all material dredged from federal channels in the Gulf states is used beneficially and very little of the privately funded dredging is used for beneficial purposes. The U.S. Army Corps of Engineers (USACE) conducts dredging under its navigation maintenance program and much of the dredging conducted is typically done on a scheduled and routine basis. Successful planning of beneficial-use projects utilizing USACE dredging necessitates the early coordination and work of multidisciplinary interagency teams on a regular basis. There is also a need to improve data access and management for dredging activities for use by project managers and planners. [ABSTRACT FROM AUTHOR]

Eleven habitat restoration case studies were summarized for a variety of habitat types, restoration goals, and project sizes. Each project had unique characteristics that required its own specific approach to habitat restoration/creation, habitat conservation, and beneficial use of sediment required for restoration. However, in every case, the underlying theme associated with restoration or conservation was effective use of sediment. For example, upland disposal of dredged material for bird habitat to avoid adverse impacts of increased turbidity on seagrass beds worked well for Laguna Madre, but Louisiana used similar material for containment dikes and marsh restoration. In both cases sediment was used for habitat restoration rather than disposed of outside the active sediment system. Project success for all case studies depended upon clear and consistent communication among stakeholders. Addressing concerns associated with proposed restoration early in the process builds confidence among stakeholders and a level of trust that often carries through the project approval process. [ABSTRACT FROM AUTHOR]

Packery Channel is an artificial inlet that occupies a historic ephemeral pathway between Corpus Christi Bay and the Gulf of Mexico. In 2005, the inlet was opened by Hurricane Emily during its construction and has remained open and navigable for more than 4 years. The shallow-draft channel has not required maintenance dredging despite episodic shoaling during storms, including Hurricane Ike. Stability of the inlet and adjacent beach is attributed to location in the southeast corner of Corpus Christi Bay, receiving augmented ebb flow by wind setup accompanying winter fronts. The ebb current, with speed sometimes exceeding 1.0 m/s, scours sediment deposited during the summer months, thereby maintaining channel depth adequate for water exchange and navigation. After the channel opened, a deposition basin initially served as the main sediment repository for sediment scoured from the bay side. Entrance channel shoaling began to increase in 2008, initiated by 15,000 m3of beach sand that entered the channel during Hurricane Ike. Subsequent shoaling is attributed to unrestricted wind-blown transport enhanced by drought. Since completion of the 430-m long dual jetties in 2006, an ebb-tidal delta has not formed. Ebb delta development is suppressed by a strong longshore current and longshore bar formation that alternates in direction seasonally, and by strong bursts of ebb flow during winter. The inlet is located in a region of nearly balanced longshore sediment transport, indicated by near-symmetric shoreline response at each jetty. The shoreline within a 1-km zone of the inlet advanced at a rate of 7.5 m/yr, whereas along the 18-km monitoring area it receded at a rate of 1.6 m/yr, reflecting in part the influence of Hurricane Ike. Channel performance tracks closely with that reported in the original design, with stability to date exceeding those 1997 predictions. [ABSTRACT FROM AUTHOR]

The accurate characterization of coral reef habitats not only supplies invaluable data to marine researchers but also provides conservation managers the necessary information to protect these fragile ecosystems. Without accurate in situ documentation of benthic coral reef communities, the general health, as well as the effects of stressors on these habitats, cannot be correctly quantified for scientific evaluation. In this study, the benthic ecological assessment for marginal reefs (BEAMR), a comprehensive monitoring protocol for reef characterization, was applied to a nearshore coral reef system in the southeast region of the Gulf of Mexico to determine if the condition of the habitat had negatively altered over the study's duration. BEAMR data sets were collected in three separate sampling events over 5 years, with sampling scheduled around an experimental application of beach compatible sand adjacent to the study area. The results from PRIMER-E v.6 statistical analyses showed that the marine reef community as a whole (i.e., integration of all benthic functional groups) was not negatively affected throughout the study's duration. Additionally, parametric statistical analyses showed that the coral reef habitat in this Gulf region did not sustain significant influxes of sediment or adverse effects to the biota, but rather showed a significant increase in stony coral colony size and cover over time. Overall, it was determined that the condition of this reef resource has maintained a positive level of sustainability during this study, and by using the BEAMR method, marine biologists were able to statistically quantify the health of a coral reef system. Even so, the vulnerability of reef resources remain, which is why specific habitat assessment protocols, such as the BEAMR method, help support the worldwide conservation of coral reef communities. By aiding in the quantification of reef health, BEAMR can help identify and characterize potential reef effects from both natural and human pressures. [ABSTRACT FROM AUTHOR]

The upper Texas coast is one of the most populated areas along the Gulf of Mexico. Three dynamic barriers along this section of coastline (Bolivar Peninsula, Galveston Island, and Follets Island) have a well-documented history of shoreline change. Numerous engineering studies incorporating both sedimentological data and numerical models have been established for this system to understand sediment fluxes. However, rarely have previous studies examined sediment fluxes for the upper Texas coast in light of certain fundamental concepts of coastal geology. Here, we discuss the current theory and understanding of barrier island dynamics from a geologic standpoint as they relate to sediment budgets for the upper Texas coast. From sediment cores, we quantify both shoreface and washover sand fluxes, which previously were not incorporated as sand sinks into sediment budgets for this system. Shoreface sand fluxes represent a sizable portion of the total budget, whereas modern washover sand fluxes are minimal. Until now, a depth of closure (beyond which sediment transport is negligible) of 4 m has typically been used; however, our data suggest a depth of at least 8 m would be more appropriate. We show that the combined upper and lower shoreface has the potential to sequester ∼160,000 ± 39,000 m³/y of sand, equaling ∼17% of the entire calculated sediment flux and ∼37% of the total longshore transport flux for the upper Texas coast, based on previous studies. Therefore, we recommend revised approaches to future sediment budget studies in order to establish more robust analyses. Ultimately, it will be crucial to use both engineering principles and geologic concepts to construct an accurate and realistic scenario for coastal restoration projects. [ABSTRACT FROM AUTHOR]

The hydrodynamics, salinity circulation, and transport of suspended fine sediment from major rivers on the northern Gulf of Mexico (GOM) were simulated with the numerical model H3D. Tides, river inflow, wind, and heat exchanges were used to drive the three-dimensional baroclinic model. Tide propagation in the northern Gulf and seasonality in the sediment plume advection from the Mississippi and Atchafalaya rivers into the GOM were well represented in the model. The similarity between the model's results and the sediment plume as seen in MODIS satellite images and the salinity structure as observed in previous studies is demonstrated. This qualitatively valid model is used for initial guidance in design of new Mississippi River (MR) diversions by studying the effects of five conceptual MR diversions on the fate of its suspended fine material. The diversions were positioned halfway between Port Sulphur and Venice, southeast Louisiana. The scenario transporting 70% of the MR to the west and 30% to the east of the delta presents the best configuration in terms of retention of sediment within the continental shelf. This configuration redirects the main sediment and freshwater flow from the river to the nearshore and the upper continental shelf with the least losses to deeper GOM waters. Given the local dominant westward wind regime, increased discharges diverted to the east will increase the amount of sediment that travels west around the MR birdfoot delta and over the Mississippi Canyon, with a higher chance of being lost to deeper waters. [ABSTRACT FROM AUTHOR]

The Pontchartrain Basin extends over 44,000 km2 from northern Mississippi to the Gulf of Mexico and includes one of the largest and most important estuarine systems in the United States. The basin supports a variety of environments, from woodlands in the north to wetlands in the south, and a growing socioeconomic infrastructure that has led to rapid development of the southern half of the basin over the past two centuries. To properly administer this infrastructure, managers need to understand the complex geologic framework of the basin and how it will respond to continued sea-level rise, variable rates and magnitudes of land subsidence, and human alteration of the landscape. This article summarizes the body of work that describes the regional evolution and stratigraphic architecture of the Pontchartrain Basin. The northern two-thirds of the basin is underlain by a stratigraphy of undifferentiated sands and clays deposited throughout the Plio-Pleistocene by glacially influenced rivers. These deposits were weathered and incised by rivers during sea-level low stands, forming a series of terraces that increase with age from south to north. The southern third of the basin is composed of estuaries formed during the Holocene, while shoreline processes created a series of sandy barriers that restricted communication to the Gulf of Mexico. The Mississippi River completed the geologic development of the basin by building a sequence of subdelta lobes along this southern margin over the past 5000 years, further sealing it from the open Gulf of Mexico. Presently, the modern Mississippi River bypasses the estuarine environment and only contributes sediments during flood events when the river overtops the levee system. Sea-level rise, subsidence within the Holocene delta-plain deposits, and movement along numerous fault systems are the active natural processes that continue to affect basin geomorphology. [ABSTRACT FROM AUTHOR]

It is generally felt in the water resources community that the most significant twenty-first century public works projects will be those undertaken to correct environmental damage caused by twentieth century projects. A second axiom is that the switch from economic development to restoration and mitigation, what we call redemption, often will be precipitated by disaster. Finally, it must be expected that the repair project will cost far more than the initial public investment but also may have economic revitalization potential far exceeding anticipated environmental benefits. We examine this cycle for the federally funded Mississippi River Gulf Outlet (MRGO) navigation project east of New Orleans, beginning with its much heralded birth in 1963 as a 122 km long free-flowing tidal canal connecting New Orleans to the Gulf of Mexico and ending with its recent de-authorization and closure. We track the direct and indirect effects of the project through its commercial failure, and then on to the official denial, the pervasive environmental impacts, and finally exposure of its role in flooding New Orleans during Hurricane Betsy in 1965 and more seriously during Hurricane Katrina in 2005. Post de-authorization planning to curtail continuing environmental and economic damage now offers an opportunity to apply lessons that have been learned and to reinstate natural processes that were disrupted or interrupted by the MRGO during the half-century of its operation. One surprising outcome is that the restoration program may turn out to be more commercially successful than the original navigation project, which was conceived as an agent of economic transformation. The U.S. Army Core of Engineers still does not acknowledge, even in the face of compelling scientific evidence, that the MRGO project was a significant cause of early and catastrophic flooding of the Upper and Lower 9th Wards, St. Bernard Parish, and New Orleans East during Hurricane Katrina. A modeling effort that removed the MRGO from the landscape, and restored the cypress swamps and marshes killed by the MRGO, reduced flooding from Hurricane Katrina by 80%. We conclude that the MRGO spelled the difference between localized flooding, and the catastrophe that killed 1464 people and inflicted tens of billions of dollars of property damages. If the MRGO-caused economic damages associated with Hurricanes Betsy and Katrina are combined with those of construction, operation and maintenance, and wetlands destroyed, then the total economic cost of the MRGO is in the hundreds of billions of dollars. [ABSTRACT FROM AUTHOR]

Aspects of northern Gulf of Mexico (NGOM) (Louisiana, Mississippi, Alabama, and Florida panhandle) processes and barrier islands that are pertinent to their geomorphologic response are contrasted with the broader knowledge base summarized by SCHWARTZ (1973) and LEATHERMAN (1979, 1985). Salient findings from studies documenting the short-term (storm-induced; timescales of hours, days, and weeks) and long-term (timescales of years, decades, and centuries) response of barrier island systems in the NGOM are synthesized into a conceptual model. The conceptual model illustrates the hypothetical evolution of three barrier island morphologies as they evolve through a typical Category 1-2 hurricane, including poststorm recovery (days to weeks) and long-term evolution (years to decades). Primary factors in barrier island geomorphologic response to storms, regardless of location, are the elevation of the island relative to storm (surge plus setup) elevation, and duration of the storm. Unique aspects of the NGOM barrier islands, compared with knowledge summarized for other barrier types, include (1) storm paths, wind speed, and large bays that create the potential for both Gulf and bayshore erosion and (2) in Louisiana and Mississippi, the potential for loading of the underlying substrate by the barrier island, which, through time, increases consolidation, relative sea level rise, overwash, morphologic change, and migration. We recommend that design of large-scale beach restoration projects incorporate the potential for (1) time-dependent consolidation of the underlying sediment due to project loading and future migration, (2) Gulf and bayshore erosion and overwash, and (3) eolian transport toward the Gulf from north winds. [ABSTRACT FROM AUTHOR]

Barrier-island chains worldwide are undergoing substantial changes, and their futures remain uncertain. An historical analysis of a barrier-island chain in the north-central Gulf of Mexico shows that the Mississippi barriers are undergoing rapid systematic land loss and translocation associated with: (1) unequal lateral transfer of sand related to greater updrift erosion compared to downdrift deposition; (2) barrier narrowing resulting from simultaneous erosion of shores along the Gulf and Mississippi Sound; and (3) barrier segmentation related to storm breaching. Dauphin Island, Alabama, is also losing land for some of the same reasons as it gradually migrates landward. The principal causes of land loss are frequent intense storms, a relative rise in sea level, and a sediment-budget deficit. Considering the predicted trends for storms and sea level related to global warming, it is certain that the Mississippi-Alabama (MS-AL) barrier islands will continue to lose land area at a rapid rate unless the trend of at least one causal factor reverses. Historical land-loss trends and engineering records show that progressive increases in land-loss rate correlate with nearly simultaneous deepening of channels dredged across the outer bars of the three tidal inlets maintained for deep-draft shipping. This correlation indicates that channel-maintenance activities along the MS-AL barriers have impacted the sediment budget by disrupting the alongshore sediment transport system and progressively reducing sand supply. Direct management of this causal factor can be accomplished by strategically placing dredged sediment where adjacent barrier-island shores will receive it for island nourishment and rebuilding. [ABSTRACT FROM AUTHOR]

A recently developed remote-sensing instrument acquires high-quality digital photographs in shallow-marine settings within water depths of 15 m. The technology, known as the Along-Track Reef-Imaging System, provides remarkably clear, georeferenced imagery that allows visual interpretation of benthic class (substrates, organisms) for mapping coral reef habitats, as intended. Unforeseen, however, are functions new to the initial technologic purpose: interpretable evidence for real-time biogeologic processes and for perception of scaled-up skeletal self-similarity of scleractinian microstructure. Florida reef sea trials lacked the grid structure required to map contiguous habitat and submarine topography. Thus, only general observations could be made relative to times and sites of imagery. Degradation of corals was nearly universal; absence of reef fish was profound. However, ∼1% of more than 23,600 sea-trial images examined provided visual evidence for local environs and processes. Clarity in many images was so exceptional that small tracks left by organisms traversing fine-grained carbonate sand were visible. Other images revealed a compelling sense, not yet fully understood, of the microscopic wall structure characteristic of scleractinian corals. Conclusions drawn from classifiable images are that demersal marine animals, where imaged, are oblivious to the equipment and that the technology has strong capabilities beyond mapping habitat. Imagery acquired along predetermined transects that cross a variety of geomorphic features within depth limits will (1) facilitate construction of accurate contour maps of habitat and bathymetry without need for ground-truthing, (2) contain a strong geologic component of interpreted real-time processes as they relate to imaged topography and regional geomorphology, and (3) allow cost-effective monitoring of regional- and local-scale changes in an ecosystem by use of existing-image global-positioning system coordinates to re-image areas. Details revealed in the modern setting have taphonomic implications for what is often found in the geologic record. [ABSTRACT FROM AUTHOR]

After hurricane overwash, restoration of dune ecosystems requires information on when, where, and how to replace plants removed by storms. Survival and subsequent growth of Schizachyrium maritimum (Chapman) Nash, Morella cerifera (L. Small), and Ceratiola ericoides Michx., transplanted at increasing distances from the Gulf of Mexico (92, 124, 179, and 200 m landward of the Gulf) with increasing protection from salt spray and desiccating winds by developing dunes, were evaluated. Survival and growth was followed for 15 months. Schizachyrium maritimum survival and growth was high regardless of distance from the Gulf. Ceratiola ericoides and M. cerifera did not survive when planted 92 m from the Gulf behind embryo dunes approximately 0.5-1 m tall. Foliage loss was noted at all distances but survival and regrowth were higher at 170 and 200 m behind two to three ridges of embryo dunes 0.5-1 m tall. [ABSTRACT FROM AUTHOR]

Most migrant shorebirds require coastal and estuarine habitat in the nonbreeding season and their overwinter survival is contingent upon the composition and quality of these winter sites. The purpose of this study was to investigate the relationship between the distribution and abundance of the piping plover, a federally threatened and endangered shorebird, and its nonbreeding habitat along the Gulf of Mexico coastline. We identified sites consistently used by wintering piping plovers and quantified landscape and anthropogenic features within a subset of those locations. Using published literature, we documented that piping plovers consistently winter at 49 locations on the U.S. Gulf of Mexico coast (Marco Island, Florida to Padre Island, Texas). At 31 sites, we conducted a remote analysis of aerial photos for 11 features (e.g., intertidal area, urban area, beach). Linear regression was used to test correlations between plover abundance and landscape characteristics. We found that certain shoreline features (e.g., landform, inter-tidal area, total area) and measures of urbanization (e.g., urban area, length of roads) were significantly correlated, positively and negatively, respectively, with piping plover abundance across the Gulf of Mexico coastline. This information is critical to prevent or mitigate negative impacts of urbanization and subsequent coastal landscape change on shorebird populations. [ABSTRACT FROM AUTHOR]

Dauphin Island, Alabama, is a 22.5 km-long microtidal barrier island/barrier spit in the northern Gulf of Mexico. As a result of the geomorphic and topographic differences across the island, tropical storms and hurricanes impact it in a variety of ways. Hurricane Frederic crossed the western end of Dauphin Island on 12 September 1979. Storm waves measuring up to 4.6 m above the mean high water level washed over much of the barrier spit portion of the island. On the eastern end of the island, one or more storm surges created a well-defined stratigraphic unit that was subsequently buried and preserved by migrating quartz-sand foredunes. The size of the storm-surge deposit was limited by several factors, including the wave run-up energy and the areal extent and elevation of the foredunes. The nature and types of invertebrate faunas found within the surge-wave deposit reflect a nearshore subtidal source (i.e., inner neritic—likely less than 10-m water depth). The storm deposit provides invaluable information regarding the strength and intensity of the storm not directly attainable through atmospheric and sea-wave records and is consistent with washover fan sedimentation from other areas in the Gulf of Mexico. [ABSTRACT FROM AUTHOR]

Nadal-Caraballo, N.C.; Campbell, M.O.; Gonzalez, V.M.; Torres, M.J.; Melby, J.A., and Taflanidis, A.A., 2020. Coastal Hazards System: A Probabilistic Coastal Hazard Analysis Framework. In: Malvárez, G. and Navas, F. (eds.), Global Coastal Issues of 2020. Journal of Coastal Research, Special Issue No. 95, pp. 1211-1216. Coconut Creek (Florida), ISSN 0749-0208. Coastal hazards such as storm surge, waves, currents, wind, and rainfall associated with extratropical and tropical cyclones (e.g., hurricanes) can have devastating effects and threaten the lives of millions of people living along the world's coastlines. This has led to the development of the Coastal Hazards System (CHS), an ambitious program with the primary goal of quantifying extreme coastal hazards due to both tropical and extratropical cyclones. The CHS currently covers all U.S. hurricane-prone coastlines along the Gulf of Mexico, the Atlantic seaboard, Puerto Rico, and the U.S. Virgin Islands, as well as regions affected only by extratropical storms like the Great Lakes. The Probabilistic Coastal Hazard Analysis (PCHA) is an innovative statistical and probabilistic framework that serves as the foundation of the CHS. This framework includes comprehensive characterization of storm climatology, high-resolution numerical modeling, and advanced joint probability analysis of atmospheric forcing and primary storm responses, including associated aleatory and epistemic uncertainties. New PCHA advancements overcome limitations of previous joint probability methods by integrating meta-Gaussian copula for the computation of storm probabilities, spatially-varying bias and uncertainty quantification, and Gaussian process metamodel (GPM) based on existing CHS synthetic tropical cyclones. GPM emulates the response of computationally-expensive hydrodynamic models and enables the generation of augmented tropical cyclone suites, consisting of up to millions of storms, for optimal coverage of the parameter and probability spaces. The CHS also includes a database and a web-based data mining and visualization system for public distribution of high-fidelity probabilistic, atmospheric and hydrodynamic modeling results. PCHA results are distributed along with the corresponding metadata, in self-describing data formats for easy and efficient use by engineers, planners, economists, emergency managers, and researchers. [ABSTRACT FROM AUTHOR]