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At least 829 records · Page 46Linked to original sources
USGS1999

The Cadiz margin study off Spain: An introduction

The Cadiz continental margin of the northeastern Gulf of Cadiz off Spain was selected for a multidisciplinary project because of the interplay of complex tectonic history between the Iberian and African plates, sediment supply from multiple sources, and unique Mediterranean Gateway inflow and outflow currents. The nature of this complex margin, particularly during the last 5 million years, was investigated with emphasis on tectonic history, stratigraphic sequences, marine circulation, contourite depositional facies, geotechnical properties, geologic hazards, and human influences such as dispersal of river contaminants. This study provides an integrated view of the tectonic, sediment supply and oceanographic factors that control depositional processes and growth patterns of the Cadiz and similar modem and ancient continental margins.

Marine Geology↗
USGS1988

The Mount Mazama climactic eruption (6900 BP) and resulting convulsive sedimentation on the continent, ocean basin, and Crater Lake caldera floor

The climactic eruption of Mount Mazama and the resulting sedimentation may have been the most significant convulsive sedimentary event in North America during Holocene time. A collapse caldera 1,200 m deep and 10 km in diameter was formed in Mount Mazama, and its floor was covered by hundreds of meters of wall-collapse debris. Wind-blown pyroclastic ash extended 2,000 km northeast from Mount Mazama and covered more than 1,000,000 km 2 of the continent. On the Pacific Ocean floor, Mazama ash was transported westward 600 to 700 km along deep-sea channels by turbidity currents. The initial single-vent phase of the climactic eruption, a Plinian column, emptied over half of the magma erupted. Debris from this phase accumulated as a pumice deposit 10 m thick at the rim to 50 cm thick as much as 100 km from the vent. This deposit created a mid-Holocene stratigraphic marker over the continent and the continental margin of western North America. A ring-vent phase followed as a second part of the climactic eruption and produced highly mobile pyroclastic flows. These flows covered the mountain for at least 14 km from the vent, continued down the valleys nearly 60 km, and deposited as much as 100 m of pumiceous ignimbrite. After the caldera collapsed as a result of the eruption of more than 50 km 3 of magma, heat of the climactic eruption apparently created phreatic explosion craters along the ring fracture zone of the caldera floor. Initially, explosion debris and sheetwash of pyroclastics off highlands seems mainly to have filled the local craters with bedded volcaniclastics. This basal, generally flat-lying unit, was quickly covered by wedges of chaotically bedded debris flow and avalanche-type deposits that thin inward from the caldera walls. These deposits may have formed in response to seismic activity associated with postcaldera volcanism that apparently began soon after the caldera collapsed. The lower two units of non-lacustrine beds (50 to 60 m) make up the majority of the postcaldera sedimentary deposits and seem to have deposited rapidly after the climactic eruption. Twenty to 25 m of lacustrine sediment has been accumulating more slowly over the subaerial debris during the past 6,900 yr. Some Mazama ash probably was transported by rivers to the sea immediately after the climactic eruption because significant amounts of this ash appear in mid-Holocene turbidites of Cascadia Basin. The presence of Mazama ash mixed with Columbia River sand in texturally and compositionally graded turbidites shows that Mazama ash periodically was moved by sediment-gravity flows down the canyons and through channels to deposition sites in the Astoria Fan and the Cascadia Channel. The coarsest and thickest tuffaceous turbidites were deposited on channel floors, and the ash-rich suspension flows that overtopped the levees were deposited as thin-bedded turbidites in interchannel areas. Study of the Mount Mazama climactic eruption shows that such an event in the Cascade Mountains has the potential to: (a) cause major destruction within 100 km of the vent, (b) severely affect biota as far as 2,000 km downwind, and (c) disrupt commercial river and marine transportation or natural sedimentation as far as several hundred kilometers in the opposite direction from wind-blown debris. Present geologic characteristics on the Crater Lake caldera floor suggest that geologic hazards from a significant volcanic event appear to be minimal for the next few thousand years.

Mount Mazama↗
USGS2012

Resource and hazard implications of gas hydrates in the Northern Gulf of Mexico: Results of the 2009 Joint Industry Project Leg II Drilling Expedition

In the 1970's, Russian scientists were the first to suggest that gas hydrates, a crystalline solid of water and natural gas, and a historical curiosity to physical chemists, should occur in abundance in the natural environment. Since this early start, the scientific foundation has been built for the realization that gas hydrates are a global phenomenon, occurring in permafrost regions of the arctic and in deep water portions of most continental margins worldwide. Recent field testing programs in the Arctic (Dallimore et al., 2008; Yamamoto and Dallimore, 2008) have indicated that natural gas can be produced from gas hydrate accumulations, particularly when housed in sand-rich sediments, with existing conventional oil and gas production technology (Collett et al., 2008) and preparations are now being made for the first marine field production tests (Masuda et al., 2009). Beyond a future energy resource, gas hydrates in some settings may represent a geohazard. Other studies also indicate that methane released to the atmosphere from destabilized gas hydrates may have contributed to global climate change in the past.

Northern Gulf Of Mexico↗
USGS2012

Development of a liquefaction hazard screening tool for caltrans bridge sites

We have developed a liquefaction hazard screening tool for the California Department of Transportation (Caltrans) that is being used to evaluate the liquefaction hazard to approximately 13,000 bridge sites in California. Because of the large number of bridge sites to be evaluated, we developed a tool that makes use of parameters not typically considered in site-specific liquefaction investigations. We assessed geologic, topographic, seismic hazard, and subsurface conditions at about 100 sites of past liquefaction in California. Among the parameters we found common to many of these sites are: (a) low elevations, (b) proximity to a water body, and (c) presence of geologically youthful deposits or artificial fill materials. The nature of the study necessitated the use of readily available data, preferably datasets that are consistent across the state. The screening tool we provided to Caltrans makes use of the following parameters: (1) proximity to a water body, (2) whether the bridge crosses a water body, (3) the age of site geologic materials and the environment in which the materials were deposited, as discerned from available digital geologic maps, (4) probabilistic shaking estimates, (5) the site elevation, (6) information from available liquefaction hazard maps [covering the 9-county San Francisco Bay Area and Ventura County] and California Geological Survey (CGS) Zones of Required Investigation. For bridge sites at which subsurface boring data were available (from CGS' existing database), we calculated Displacement Potential Index values using a methodology developed by Allison Faris and Jiaer Wu. Caltrans' staff will use this hazard-screening tool, along with other tools focused on bridges and foundations, to prioritize site-specific investigations. ?? 2009 ASCE.

Conference Paper↗
USGS1990

The Ebro margin study, northwestern Mediterranean Sea - an introduction

The Ebro continental margin from the coast to the deep sea off northeastern Spain was selected for a multidisciplinary project because of the abundant Ebro River sediment supply, Pliocene and Quaternary progradation, and margin development in a restricted basin where a variety of controlling factors could be evaluated. The nature of this young passive margin for the last 5 m.y. was investigated with particular emphasis on marine circulation, sediment dynamics, sediment geochemistry, depositional facies, seismic stratigraphy, geotechnical properties, geological hazards and human influences. These studies show the importance of marine circulation, variation in sediment supply, sea-level oscillation and tectonic setting for the understanding of modern and ancient margin depositional processes and growth patterns.

Marine Geology↗
USGS2022

Statistical consideration of nonrandom treatment applications reveal region-wide benefits of widespread post-fire restoration action

Accurate predictions of ecological restoration outcomes are needed across the increasingly large landscapes requiring treatment following disturbances. However, observational studies often fail to account for nonrandom treatment application, which can result in invalid inference. Examining a spatiotemporally extensive management treatment-- post-fire seeding of declining sagebrush shrubs across the semiarid U.S. over two decades -- we quantify drivers and consequences of selection biases in restoration, using remotely sensed data. Treatments were disproportionately applied in more stressful, degraded ecological conditions. Failure to incorporate nonrandom treatment allocation led to the conclusion that costly, widespread seedings were unsuccessful; however, after considering biases, restoration positively affected sagebrush recovery. Treatment effect sizes varied with climate, indicating possible prioritization criteria for interventions. Our findings revise the perspective that widespread post-fire sagebrush seedings have been broadly “unsuccessful” and demonstrate how selection biases can pose substantive inferential hazards in observational studies of restoration efficacy and development of restoration theory.

California, Colorado, Idaho, Nevada, Oregon, Utah,↗
USGS2013

Extreme rainfall, vulnerability and risk: a continental-scale assessment for South America

Extreme weather continues to preoccupy society as a formidable public safety concern bearing huge economic costs. While attention has focused on global climate change and how it could intensify key elements of the water cycle such as precipitation and river discharge, it is the conjunction of geophysical and socioeconomic forces that shapes human sensitivity and risks to weather extremes. We demonstrate here the use of high-resolution geophysical and population datasets together with documentary reports of rainfall-induced damage across South America over a multi-decadal, retrospective time domain (1960–2000). We define and map extreme precipitation hazard , exposure , affected populations, vulnerability and risk , and use these variables to analyse the impact of floods as a water security issue. Geospatial experiments uncover major sources of risk from natural climate variability and population growth, with change in climate extremes bearing a minor role. While rural populations display greatest relative sensitivity to extreme rainfall, urban settings show the highest rates of increasing risk. In the coming decades, rapid urbanization will make South American cities the focal point of future climate threats but also an opportunity for reducing vulnerability, protecting lives and sustaining economic development through both traditional and ecosystem-based disaster risk management systems.

Philosophical Transactions of the Royal Society A:↗
USGS2023

Shallow deformation on the Kirby Hills fault, Sacramento–San Joaquin Delta, California (USA), revealed from high-resolution seismic reflection data and coring in a fluvial system

The Sacramento–San Joaquin Delta (Delta) in California (USA) is an important part of the state’s freshwater system and is also a major source of agricultural and natural resources. However, the Delta is traversed by a series of faults that make up the easternmost part of the San Andreas fault system at this latitude and pose seismic hazard to this region. In this study, we use new high-resolution chirp subbottom data to map and characterize the shallow expression of the Kirby Hills fault, where it has been mapped to cross the Sacramento River at the western extent of the Delta. The fault is buried here, but we document a broad zone of deformation associated with the eastern strand of the fault that changes in character, along strike, across ~600 m of the river channel. Radiocarbon dates from sediment cores collected in the Sacramento River provide some minimum constraints on the age of deformation. We do not observe evidence of the western strand as previously mapped. We also discuss difficulties of conducting a paleoseismologic study in a fluvial environment.

California↗
USGS1977

Reconnaissance engineering geology of the Metlakatla area, Annette Island, Alaska, with emphasis on evaluation of earthquakes and other geologic hazards

A program to study the engineering geology of most larger Alaska coastal communities and to evaluate their earthquake and other geologic hazards was started following the 1964 Alaska earthquake; this report about the Metlakatla area, Annette Island, is a product of that program. Field-study methods were of a reconnaissance nature, and thus the interpretations in the report are tentative. Landscape of the Metlakatla Peninsula, on which the city of Metlakatla is located, is characterized by a muskeg-covered terrane of very low relief. In contrast, most of the rest of Annette Island is composed of mountainous terrane with steep valleys and numerous lakes. During the Pleistocene Epoch the Metlakatla area was presumably covered by ice several times; glaciers smoothed the present Metlakatla Peninsula and deeply eroded valleys on the rest. of Annette Island. The last major deglaciation was completed probably before 10,000 years ago. Rebound of the earth's crust, believed to be related to glacial melting, has caused land emergence at Metlakatla of at least 50 ft (15 m) and probably more than 200 ft (61 m) relative to present sea level. Bedrock in the Metlakatla area is composed chiefly of hard metamorphic rocks: greenschist and greenstone with minor hornfels and schist. Strike and dip of beds are generally variable and minor offsets are common. Bedrock is of late Paleozoic to early Mesozoic age. Six types of surficial geologic materials of Quaternary age were recognized: firm diamicton, emerged shore, modern shore and delta, and alluvial deposits, very soft muskeg and other organic deposits, and firm to soft artificial fill. A combination map unit is composed of bedrock or diamicton. Geologic structure in southeastern Alaska is complex because, since at least early Paleozoic time, there have been several cycles of tectonic deformation that affected different parts of the region. Southeastern Alaska is transected by numerous faults and possible faults that attest to major movements of the earth's crust. The latest of the major tectonic events in the Metlakatla region occurred in middle Tertiary time; some minor fault activity probably continues today at depth. Along the outer coast of southeastern Alaska and British Columbia, major faulting activity occurs in the form of active, strike-slip movement along the Queen Charlotte fault about 100 mi (160 kin) west-southwest of Metlakatla. Some branching subsidiary faults also may be active, at least one of which may be the Sandspit fault. Many major and smaller earthquakes occur along the outer coast. These shocks are related to movements along the Queen Charlotte fault. A few small earthquakes occur in the region between the outer coast and the Coast Mountains, which includes Metlakatla. 0nly a few earthquakes have been reported as felt at Metlakatla; these shocks and others felt in the region are tabulated. Historically, the closest major earthquake was the magnitude 8.1 Queen Charlotte Islands earthquake of August 22, 1949, which occurred along the Queen Charlotte fault 125 mi (200 km) southwest of Metlakatla. No damage was reported at Metlakatla. The probability of destructive earthquakes affecting Metlakatla is unknown. A consideration of the tectonics and earthquake history of the region, however, suggests that sometime in the future an earthquake with a magnitude of about 8 will occur along that segment of the Queen Charlotte fault nearest to Metlakatla. Smaller earthquakes with magnitudes of 6 or more might occur elsewhere in the Metlakatla region or south-southeastward near Dixon Entrance or Hecate Strait. Several geologic effects that have characterized large earthquakes elsewh6re may be expected to accompany some of the possible major earthquakes that might affect the Metlakatla area in the future. Evaluation of effects indicates that fault displacement and tectonic uplift or subsidence are probably unlikely, and ground shaking in general probably would be strongest

Open-File Report↗
USGS2021

An assessment of vertical land movement to support coastal hazards planning in Washington state

The sea and land change elevation spatially and temporally from a multitude of processes, so it is necessary to constrain the movement of both to evaluate how coastlines will evolve and how those evolving coastlines will impact the natural and built environment over time. We combine land movement observations from global navigation satellite systems (GNSSs), leveling of geodetic monuments, and tide gauge records with a tectonic model of the Cascadia subduction zone to constrain absolute rates of vertical land movement in coastal Washington. We infer rates of vertical land movement in areas lacking direct observations by interpolating high-quality land movement observations and a discretely sampled interseismic locking model. Here we present a model of absolute vertical land movement that is combined with sea level rise estimates to inform local relative sea level projections on a community-scale. The most rapid vertical uplift (~3.5 mm/year) of the land is found across the northwest Olympic Peninsula, which currently outpaces sea level rise. Conversely, some areas, including a stretch of the northern Pacific Ocean coast from La Push to Kalaloch and the southern Puget Sound, are found to be subsiding at 0.5–1.0 mm/year, exacerbating the rate of relative sea level rise and thereby increasing the vulnerability of coastal communities.

Washington↗
USGS2026

Impacts of transient critical zone evolution on landslide susceptibility and hazard Across the Utuado batholith, Puerto Rico

Landscapes in humid climates often experience rapid chemical and mechanical weathering that can change groundwater fluxes, drainage pathways, and frictional strength via alterations in subsurface mineral composition and matrix porosity. These changes to hillslope critical zone structure and strength should control landslide susceptibility, size, and failure style. Here we test the impact of differential weathering on landslide failure processes by exploiting a natural experiment along the dioritic Utuado batholith in Puerto Rico's Cordillera Central, where a sharp weathering gradient follows an upstream-propagating knickzone into an uplifted shoreline platform that was affected by Hurricane Maria in 2017. Through a combination of landslide mapping, field geophysical and geotechnical surveys, topographic analysis, calibrated stream profile inversion, 3D back-analysis of hillslope strength, and debris-flow inundation assessments, we show that differential weathering induces changes to critical zone structure and consequently landslide susceptibility and hazard. Our mapping reveals that the hurricane-induced landslides preferentially cluster along less weathered hillslopes despite a marked increase in frictional strength. Jointly inverted seismic refraction and electrical resistivity profiles show that the frictionally weak, heavily weathered hillslopes are highly porous and dry, which we posit acts to stabilize slopes through limiting deeper hydrologic connectivity that can produce shallow water tables with destabilizing lateral seepage forces during storms. Debris-flow inundation mapping and analysis reveals that major contributors to debris-flow growth, channel steepness and landslide coalescence, scale linearly with hillslope friction angle. This leads to higher-mobility debris flows along knickzone reaches, which disproportionately affects communities at the base of the plateau.

Puerto Rico↗
USGS2023

Assessment of resource potential from mine tailings using geostatistical modeling for compositions: A methodology and application to Katherine Mine site, Arizona, USA

The mining industry, in most cases, targets a specific valuable commodity that is present in small quantities within large volumes of extracted material. After milling and processing, most of the extracted material and the effluents are stored as waste (tailings) in impoundments, such as dams or waste dumps, or are backfilled into underground mines. In time, tailing materials may become an issue of environmental and health concern due to the hazardous elements, ions, and oxides contained within the waste material. In addition, handling and storage of such waste in dams may pose the risk of dam failure with catastrophic consequences to nature and nearby communities. On the other hand, tailings may offer potential as secondary sources of critical elements (CEs), including rare earth elements (REEs), which may have been overlooked during primary production and processing. Therefore, treating mine tailings as a resource has economic and environmental benefits by reducing the waste from new and historical mine sites through remining. One of the critical steps for taking advantage of these benefits is to spatially quantify the resources and the pollutants, which require the application of adequate data analysis and modeling methods, often to compositional geochemical data. Utilizing adequate methods is especially important for correctly quantifying resource potential, as the quantities will often be at low concentrations. This work presents quantification of resource potential (Au, Ag, Cu, Zn, Pb) and elements of environmental concern (Hg and As) from the tailings of a historic mine site, Katherine Mine, AZ, USA. Data reported by the U.S. Bureau of Mines (USBM) after extensive field campaigns in the 1990s, including sampling from tailing impoundment and surrounding areas for geochemical characterization and geophysical surveys, were used. First, compositional data (CoDa) analysis was employed to explore associations of sampling locations, geochemical parts, and the clustering of samples. Next, sequential Gaussian simulation (SGSIM) was applied to samples that showed a genetic link to tailing material after isometric log-ratio transformation (ilr) and mix/max autocorrelation factor (MAF) transformation for spatial modeling and uncertainty evaluation. Geostatistical results revealed spatial variability of concentrations within the tailing area. Uncertainty evaluation based on realizations indicated that Cu (14.27–20.01 t), Zn (44.23–76.23 t), and Pb (22.56–38.28 t) are the most abundant elements within a 5 %–95 % interval, followed by Ag and Au (~5.3 and 0.18 t, at 50th percentile), respectively. Of the elements of health concern, As was found to be ~4.8 t (50th percentile) in the tailing area. The work also showed that ~0.51 t As, 0.005 t Hg, 0.020 t of Au, and 0.62 t of Ag were carried to Lake Mohave by an ephemeral stream called Katherine Wash, which transects the tailings.

Arizona↗
USGS2005

Real-time forecasts of tomorrow's earthquakes in California

Despite a lack of reliable deterministic earthquake precursors, seismologists have significant predictive information about earthquake activity from an increasingly accurate understanding of the clustering properties of earthquakes. In the past 15 years, time-dependent earthquake probabilities based on a generic short-term clustering model have been made publicly available in near-real time during major earthquake sequences. These forecasts describe the probability and number of events that are, on average, likely to occur following a mainshock of a given magnitude, but are not tailored to the particular sequence at hand and contain no information about the likely locations of the aftershocks. Our model builds upon the basic principles of this generic forecast model in two ways: it recasts the forecast in terms of the probability of strong ground shaking, and it combines an existing time-independent earthquake occurrence model based on fault data and historical earthquakes with increasingly complex models describing the local time-dependent earthquake clustering. The result is a time-dependent map showing the probability of strong shaking anywhere in California within the next 24 hours. The seismic hazard modelling approach we describe provides a better understanding of time-dependent earthquake hazard, and increases its usefulness for the public, emergency planners and the media.

Nature↗
USGS2023

Importance of subsurface water for hydrological response during storms in a post-wildfire bedrock landscape

Wildfire alters the hydrologic cycle, with important implications for water supply and hazards including flooding and debris flows. In this study we use a combination of electrical resistivity and stable water isotope analyses to investigate the hydrologic response during storms in three catchments: one unburned and two burned during the 2020 Bobcat Fire in the San Gabriel Mountains, California, USA. Electrical resistivity imaging shows that in the burned catchments, rainfall infiltrated into the weathered bedrock and persisted. Stormflow isotope data indicate that the amount of mixing of surface and subsurface water during storms was similar in all catchments, despite higher streamflow post-fire. Therefore, both surface runoff and infiltration likely increased in tandem. These results suggest that the hydrologic response to storms in post-fire environments is dynamic and involves more surface-subsurface exchange than previously conceptualized, which has important implications for vegetation regrowth and post-fire landslide hazards for years following wildfire.

California↗
USGS2010

Predicting coastal cliff erosion using a Bayesian probabilistic model

Regional coastal cliff retreat is difficult to model due to the episodic nature of failures and the along-shore variability of retreat events. There is a growing demand, however, for predictive models that can be used to forecast areas vulnerable to coastal erosion hazards. Increasingly, probabilistic models are being employed that require data sets of high temporal density to define the joint probability density function that relates forcing variables (e.g. wave conditions) and initial conditions (e.g. cliff geometry) to erosion events. In this study we use a multi-parameter Bayesian network to investigate correlations between key variables that control and influence variations in cliff retreat processes. The network uses Bayesian statistical methods to estimate event probabilities using existing observations. Within this framework, we forecast the spatial distribution of cliff retreat along two stretches of cliffed coast in Southern California. The input parameters are the height and slope of the cliff, a descriptor of material strength based on the dominant cliff-forming lithology, and the long-term cliff erosion rate that represents prior behavior. The model is forced using predicted wave impact hours. Results demonstrate that the Bayesian approach is well-suited to the forward modeling of coastal cliff retreat, with the correct outcomes forecast in 70–90% of the modeled transects. The model also performs well in identifying specific locations of high cliff erosion, thus providing a foundation for hazard mapping. This approach can be employed to predict cliff erosion at time-scales ranging from storm events to the impacts of sea-level rise at the century-scale.

Marine Geology↗
USGS2021

Profiling lunar dust dissolution in aqueous environments: The design concept

Published studies and internal NASA reports indicate that when native lunar dust is suspended in an aqueous solution a variety of metal and other ions are released. This release has implications for future lunar missions, ranging from effects on mission hardware, effects on life support systems, possible direct effects on human health, and effects on research experiments such as plant growth experiments, space biology experiments and any activities that may involve the use of water sourced from the lunar poles. Furthermore, such contaminants could become concentrated or chemically altered to a more hazardous form during a variety of lunar mission activities, including everything from space suit cleaning to lunar industrial materials extraction. The exact profile of the release of ions from lunar dust and the nature of the partially dissolved particles has not been explored. Any model of this dissolution must be based on an understanding of the unique micromorphology of lunar dust, including its glassy nature, agglutinate features, high surface area and the presence of small deposits of elemental iron (nanophase iron) located near the surface of the grain particles. Dust has a very high surface area available for interaction with water. For this reason, on first exposure to water, an immediate pulsed release of ions could occur, with more prolonged release taking place over months or years. The few studies that have been conducted previously have been limited in both the time scales examined and in the selection of ions that were measured. The proposed investigation is a comprehensive materials science investigation, using the most modern analytical tools to catalogue all metals given off from lunar dust in various aqueous solutions and their time profiles of release from the very short term to the very long term. The product of the proposed study will be a comprehensive database determined from NASA curated samples collected from the Apollo landing sites that can be applied to research in both living systems and non-living systems on the moon. The methods developed in the proposed study will also establish standards for analysis of lunar dust samples returned from future manned missions (Artemis and others) and future robotic missions. The knowledge gained from this basic materials science investigation will have broad impact on the design of engineered human safety and health systems.

Acta Astronautica↗
USGS2021

The value of US coral reefs for flood risk reduction

Habitats, such as coral reefs, can mitigate increasing flood damages through coastal protection services. We provide a fine-scale, national valuation of the flood risk reduction benefits of coral habitats to people, property, economies and infrastructure. Across 3,100 km of US coastline, the top-most 1 m of coral reefs prevents the 100-yr flood from growing by 23% (113 km 2 ), avoiding flooding to 53,800 (62%) people, US\$2.7 billion (90%) damage to buildings and US\$2.6 billion (49%) in indirect economic effects. We estimate the hazard risk reduction benefits of US coral reefs to exceed US$1.8 billion annually. Many highly developed coastlines in Florida and Hawaii receive annual benefits of over US\$10 million km –1 , whereas US reefs critically reduce flooding of vulnerable populations. This quantification of spatial risk reduction can help to prioritize joint actions in flood management and environmental conservation, opening new opportunities to support reef management with hazard mitigation funding.

Nature Sustainability↗
USGS2020

Predicting barrier island habitats and oyster and seagrass habitat suitability for various restoration measures and future conditions for Dauphin Island, Alabama

Barrier islands, such as Dauphin Island, Alabama, provide numerous invaluable ecosystem services including storm damage reduction and erosion control to the mainland, habitat for fish and wildlife, carbon sequestration in marshes, water catchment and purification, recreation, and tourism. These islands are dynamic environments that are gradually shaped by currents, waves, and tides under quiescent conditions yet can evolve in the time scale of hours to days during hurricanes and other extreme storms. The ecosystems associated with these islands also face numerous other hazards, including accelerated sea-level rise, oil spills, and anthropogenic stressors. Hurricane Katrina in 2005 and the Deepwater Horizon oil spill in 2010 are two major events that have affected habitats and natural resources on Dauphin Island, Ala. The latter event prompted a cooperative effort between the U.S. Geological Survey and the U.S. Army Corps of Engineers to investigate viable, sustainable restoration measures that reduce degradation and enhance the natural resources of Dauphin Island, Ala. In collaboration with the State of Alabama and the National Fish and Wildlife Foundation, the overarching goal of the Alabama Barrier Island Restoration Feasibility Assessment project was to document baseline conditions and forecast potential conditions under varying sea-level change and storm scenarios for a no-action alternative along with a variety of restoration measures including beach and dune restoration, marsh and back-barrier restoration, and placement of sand in the littoral zone. The modeling component of this project used decadal hydrodynamic geomorphic, water quality, and habitat modeling to better understand how the various restoration measures may influence the habitat composition, sustainability, and resiliency of Dauphin Island under potential future conditions, benchmarked against the no-action case. The report covers the habitat modeling efforts associated with the Alabama Barrier Island Restoration Feasibility Assessment project. For various potential future island configurations for Dauphin Island, we predicted coverage of habitat types (for example, beach, dune, intertidal marsh, and woody vegetation) using a spatially explicit habitat model based on landscape-position information (for example, elevation and distance from shore) extracted from the hydrodynamic geomorphic outputs. Similarly, we forecasted habitat suitability for oysters and seagrass using habitat suitability index models. Another component of the Alabama Barrier Island Restoration Feasibility Assessment project, presented separately, integrates these habitat model results into a structured decision-making framework that accounts for competing objectives. Collectively, this information provides insights to natural resource managers and planners on how a restoration measure may maintain or impede natural coastal processes and provide information critical for making future-focused decisions regarding barrier island restoration.

Alabama↗