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At least 667 records · Page 37Linked to original sources
USGS2019

An integrative GIS approach to analyzing the impacts of septic systems on the coast of Florida, USA

An estimated 2.7 million septic systems in Florida, USA are potential ground and surface water contaminant sources that may affect environmental and human health. This study examined the spatial distribution of septic systems, coastal surface water contamination, and related environmental factors of coastal Florida watersheds at the 8-digit hydrologic unit code level. Hydrology, in situ sampling data, and other ancillary data were combined in a geographic information system to examine spatial relationships. Spatial distribution data were correlated to nitrogen, Enterococci counts, and beach closures tabulated since 2000, 2007, and 2012. Significant positive correlations (α = 0.05) with nitrogen and Enterococci counts were consistent for percent agricultural cover, percent combined urban and agricultural cover, septic tank density, population density, and septic tank density in poorly drained soils. Beach closures since 2012 were significantly positively correlated (α = 0.05) to average impervious cover (IC) and percent urbanization. Statistics indicated that Enterococci counts, nitrogen, and beach closures may be related to specific environmental factors and septic tank densities. The combination of septic tanks in urban regions with high IC prone to elevated runoff could also be a factor in surface water contamination. Data availability was also highlighted as a limitation due to infrequent spatial and temporal sampling.

Florida↗
USGS2009

Erosional history of Cape Halkett and contemporary monitoring of bluff retreat, Beaufort Sea coast, Alaska

Cape Halkett is located along the Beaufort Sea at the end of a low-lying tundra landscape. The area has been subject to major modifications over the last century as a result of erosion and migration of the coastline inland. Long-term mean annual erosion rates (1955-2009) for the entire cape are 7.6 m/yr, with a gradual increase in rates over the first five time periods of remotely sensed imagery analyzed and a large increase during the most recent time period. Division of the cape into three distinct coastal zones shows very different erosional patterns: the northeast-facing segment (Zone 1) showing a consistent and large increase; the southeast-facing segment (Zone 3) showing a gradual increase with recent, heightened erosion rates; and the east-facing segment (Zone 2) showing decreased rates due to the reformation of a sand and gravel spit. Monitoring of bluff erosion with time-lapse photography, differential GPS surveys, terrestrial and bathymetric surveys, and water level, sea and permafrost temperature data provide insights into the processes driving contemporary patterns of erosion and will provide valuable information for the prediction of future shoreline positions.

Alaska↗
USGS1983

Clutch size, reproductive success, and organochlorine contaminants in Atlantic coast black-crowned night-herons

In 1979, we gathered clutch-size and reproductive-success data on Black-crowned Night-Herons ( Nycticorax nycticorax ) nesting in three New England and two North Carolina colonies. In 1975, we gathered similar data from one of the New England and one of the North Carolina colonies. Latitudinal differences in clutch initiation were not evident. Mean clutch size was larger in the New England than in the North Carolina colonies. Mean clutch size was smaller in late nests from one New England colony studied in both years and another New England colony studied in 1979; seasonal trends in clutch size for other colonies were not found. In 1979, nest success was greater in two New England colonies than in one North Carolina colony. Within-season differences in nest success occurred but were inconsistent among colonies. In the four instances where statistical comparisons could be made, larger clutches were more successful than smaller ones in two colonies; large and small clutches had similar success in two other colonies. One egg was collected from each of several nests in each colony in 1979 for organochlorine contaminant analysis, and the fate of the remaining eggs was recorded. Concentrations of DDE and PCBs did not differ with clutch size; concentrations of PCBs were lower, however, in eggs laid late in the season. Although the data suggest an effect of DDE on hatching success in the northern more contaminated colonies, the impact of environmental contaminants on overall reproductive success appears to be minimal.

Massachusetts, North Carolina, Rhode Island↗
USGS2022

Considerations for creating equitable and inclusive communication campaigns associated with ShakeAlert, the earthquake early warning system for the West Coast of the USA

Purpose The 2019 Global Assessment Report on Disaster Risk Reduction (GAR) cites earthquakes as the most damaging natural hazard globally, causing billions of dollars of damage and killing thousands of people. Earthquakes have the potential to drastically impact physical, social and economic landscapes; to reduce this risk, earthquake early warning (EEW) systems have been developed. However, these technical EEW systems do not operate in a vacuum; the inequities in social systems, along with the needs of diverse populations, must be considered when developing these systems and their associated communication campaigns. Design/methodology/approach This article reviews aspects of social vulnerability as they relate to ShakeAlert, the EEW system for the USA. The authors identified two theories (relationship management theory and mute group theory) to inform self-reflective questions for agencies managing campaigns for EEW systems, which can assist in the development of more inclusive communication practices. Finally, the authors suggest this work contributes to important conversations about diversity, equity and inclusion (DEI) issues within early warning systems and earthquake preparedness campaigns in general. Findings To increase inclusivity, Macnamara (2012) argues that self-reflective questioning while analyzing perspective, philosophy and approaches for a campaign can help. Specific to EEW campaigns, developers may find self-reflective questions a useful approach to increase inclusion. These questions are guided by two theories and are explored in the paper. Research limitations/implications Several research limitations exist. First, this work explores two theories to develop a combined theoretical model for self-reflective questions. Further research is required to determine if this approach and the combination of these two theories have adequately informed the development of the reflective questions. Orginality/value The authors could find little peer-reviewed work examining DEI for EEW systems, and ShakeAlert in particular. While articles on early warning systems exist that explore aspects of this, EEW and ShakeAlert, with its very limited time frames for warnings, creates unique challenges.

West Coast↗
USGS2020

Detrital zircon age spectra of middle and upper Eocene outcrop belts, U.S. Gulf Coast region

Recently reported detrital zircon (DZ) data help to associate the Paleogene strata of the Gulf of Mexico region to various provenance areas. By far, recent work has emphasised upper Paleocene-lower Eocene and upper Oligocene strata that were deposited during the two episodes of the highest sediment supply in the Paleogene. The data reveal a dynamic drainage history, including (1) initial routing of western Cordilleran drainages towards the Gulf of Mexico in the Paleocene, (2) an eastward shift of the western continental divide, from the Jura-Cretaceous cordilleran arc to the eastern edge of the Laramide province after the Paleocene and (3) a southward shift, along the eastern Laramide province, of the headwaters of river systems draining to the Mississippi and Houston embayments at some time between the early Eocene and Oligocene. However, DZ characterisation of most (~20 Myr) of the middle Eocene-lower Oligocene section remains limited. We present 60 DZ age spectra, most of which are from the middle or upper Eocene outcrop belts, with 50–200-km spacing. We define six to eight distinct groups of DZ age spectra for middle and upper Eocene strata. Data from this and other studies resolve at least six substantial temporal changes in age spectra at various positions along the continental margin. The evolving age spectra constrain the middle and upper Eocene drainage patterns of large parts of interior North America. The most well-resolved aspects of these drainage patterns include (1) persistent rivers that flowed from erosional landscapes across the Paleozoic Appalachian orogen either into the low-lying Mississippi embayment or directly into the eastern Gulf; (2) at least during marine regressions, a trunk channel that likely flowed southward along the axial part of Mississippi Embayment and integrated tributaries from the east and west; and (3) rivers that flowed to the Houston embayment in the middle Eocene that likely originated in the Laramide province in central Colorado and southern Wyoming, as Precambrian basement highs in those source areas were being unroofed.

Gulf Coast region↗
USGS2005

Estimating water‐table altitudes for regional ground‐water flow modeling, U.S. Gulf Coast

Water‐table altitude, a controlling factor for ground‐ water flow , was estimated from detailed topographic data by subtracting the estimated depth‐to‐water. Land‐surface altitude of the Coastal Plain in the south‐ central United States varies from 0 to more than 800 feet above sea level. Predevelopment depth‐to‐water in 6,825 wells less than 150 feet deep averages 25.7 feet (standard deviation, 19.5 feet). Most water‐table‐altitude variation is due to variation in land‐surface altitude and not due to variation in depth‐to‐ water. Digital topographic data, from 1:250,000 scale maps for every 30 seconds of latitude and longitude are available for the continental United States. About 90 altitudes were averaged for each 25‐square‐mile block of a rectangular grid used for ground‐water flow modeling. Multiple linear regressions of predevelopment water‐level data and topographic data were used to derive empirical equations relating water‐table altitude to topography. The regression method was more consistent, efficient, and accurate than manually digitizing values from manually contoured water‐table maps. Water‐table maps usually are prepared from few data that are concentrated in topographically flat areas. Manually digitizing water‐table maps on a regional scale introduces additional error. About 35 percent of the water‐table altitudes obtained manually were greater than average land‐surface altitudes from topographic data. The mean difference between water‐table altitudes from the two methods was less than 10 feet, which indicates no systematic error was incorporated in the regression method. Copyright © 1989, Wiley Blackwell. All rights reserved

Gulf of Mexico coast↗
USGS2006

Identification of marine hydrates in situ and their distribution off the Atlantic coast of the United States

Natural gas hydrates, mostly methane hydrates, occur within seafloor sediments almost everywhere in the world’s oceans where water depths exceed 300 to 500 m, and hydrates in this setting probably contain very large quantities of methane.’ Gas hydrates have been identified in marine sediments by coring and by the response that they create in seismic reflection profiles. Our research has endeavored to refine the criteria used to recognize hydrates in seismic reflection data and to use such data to map hydrates on the United States Atlantic continential rise. Gas hydrates in ocean floor sediments occur within a layer just below the sea floor, controlled by the pressure and temperature conditions. Actually, hydrates would be stable in deep ocean water (at depths greater than 300-500 m), but probably do not exist there due to lack of gas saturation. Furthermore, if they did form in the water the hydrates would float upward and melt at the lower pressure and higher temperature conditions found at shallower depths. However, gas is present in the sediments either as biogenic gas produced by bacteria or as thermogenic gas rising from deeper strata, and when hydrate forms in sediments it is trapped in the sedimentary matrix. Temperature increases downward through the sediments, and, although pressure also increases (which tends to make hydrate more stable), the temperature ultimately becomes too great for hydrate to exist at ambient pressure. Because the thermal gradient is fairly constant within a restricted geographic region, this stability limit will be reached at approximately the same subbottom depth everywhere in the region. The result is a zone of hydrate-cemented sediment that extends down from the sea floor; this zone can have a thickness of as much as 1000 m.

Atlantic Coast↗
USGS2014

High fidelity does not preclude colonization: range expansion of molting Black Brant on the Arctic coast of Alaska

High rates of site fidelity have been assumed to infer static distributions of molting geese in some cases. To test this assumption, we examined movements of individually marked birds to understand the underlying mechanisms of range expansion of molting Black Brant ( Branta bernicla nigricans ) on the Arctic Coastal Plain (ACP) of Alaska. The Teshekpuk Lake Special Area (TLSA) on the ACP was created to protect the primary molting area of Brant. When established in 1977, the TLSA was thought to include most, if not all, wetlands used by molting Brant on the ACP. From 2010 to 2013, we surveyed areas outside the TLSA and counted an average of 9800 Brant per year, representing 29–37% of all molting Brant counted on the ACP. We captured and banded molting Brant in 2011 and 2012 both within the TLSA and outside the TLSA at the Piasuk River Delta and Cape Simpson to assess movements of birds among areas across years. Estimates of movement rates out of the TLSA exceeded those into the TLSA, demonstrating overall directional dispersal. We found differences in sex and age ratios and proportions of adult females with brood patches, but no differences in mass dynamics for birds captured within and outside the TLSA. Overall fidelity rates to specific lakes (0.81, range = 0.49–0.92) were unchanged from comparable estimates obtained in the early 1990s. We conclude that Brant are dispersing from the TLSA into new molting areas while simultaneously redistributing within the TLSA, likely as a consequence of changes in relative habitat quality. Shifts in distribution resulted from colonization of new areas by young birds as well as low levels of directional dispersal of birds that previously molted in the TLSA. Based on combined counts, the overall number of molting Brant across the ACP has increased substantially.

Alaska↗
USGS2021

Rapid observations of ocean dynamics and stratification along a steep island coast during Hurricane María

Hurricanes are extreme storms that affect coastal communities, but the linkages between hurricane forcing and ocean dynamics remain poorly understood. Here, we present full water column observations at unprecedented resolution from the southwest Puerto Rico insular shelf and slope during Hurricane María, representing a rare set of high-frequency, subsurface, oceanographic observations collected along an island margin during a hurricane. The shelf geometry and orientation relative to the storm acted to stabilize and strengthen stratification. This maintained elevated sea-surface temperatures (SSTs) throughout the storm and led to an estimated 65% greater potential hurricane intensity contribution at this site before eye passage. Coastal cooling did not occur until 11 hours after the eye passage. Our findings present a new framework for how hurricane interaction with insular island margins may generate baroclinic processes that maintain elevated SSTs, thus potentially providing increased energy for the storm.

southwestern Puerto Rico↗
USGS2024

Signatures of wave erosion in Titan’s coasts

The shorelines of Titan’s hydrocarbon seas trace flooded erosional landforms such as river valleys; however, it is unclear whether coastal erosion has subsequently altered these shorelines. Spacecraft observations and theoretical models suggest that wind may cause waves to form on Titan’s seas, potentially driving coastal erosion, but the observational evidence of waves is indirect, and the processes affecting shoreline evolution on Titan remain unknown. No widely accepted framework exists for using shoreline morphology to quantitatively discern coastal erosion mechanisms, even on Earth, where the dominant mechanisms are known. We combine landscape evolution models with measurements of shoreline shape on Earth to characterize how different coastal erosion mechanisms affect shoreline morphology. Applying this framework to Titan, we find that the shorelines of Titan’s seas are most consistent with flooded landscapes that subsequently have been eroded by waves, rather than a uniform erosional process or no coastal erosion, particularly if wave growth saturates at fetch lengths of tens of kilometers.

Science Advances↗
USGS1975

Brown pelicans: Improved reproduction off the southern California coast

Although still about 30 percent too low for population stability, productivity of California brown pelicans at their two northern colonies has improved significantly since 1971. Numbers of adults breeding probably reflect food supplies and recruitment from more successful colonies to the south, but improving fledging rates (up to 0.9 young per nest in 1974) reflect better egg survival and improving eggshell condition, with declining DDE contamination in anchovies, their major food source.

California↗
USGS1967

Geological exploration in an East Coast submarine canyon from a research submersible

Large talus blocks litter the flat floor of Oceanographer Canyon at a depth of 1460 meters; they indicate down-axis mass transport of floor sediment at an unknown time and rate. From 1460 to 1310 meters the sidewall is covered by unconsolidated sediment lying at 35° to 40° from the horizontal. An outcrop of Pleistocene or younger sediment at 1460 meters is probably a remnant of a former fill.

Science↗
USGS1987

Evidence for great Holocene earthquakes along the outer coast of Washington state

Intertidal mud has buried extensive, well-vegetated lowlands in westernmost Washington at least six times in the past 7000 years. Each burial was probably occasioned by rapid tectonic subsidence in the range of 0.5 to 2.0 meters. Anomalous sheets of sand atop at least three ofthe buried lowlands suggest that tsunamis resulted from the same events that caused the subsidence. These events may have been great earthquakes from the subduction zone between the Juan de Fuca and North America plates.

Washington↗
USGS1991

Strain measurements and the potential for a great subduction earthquake off the coast of Washington

Geodetic measurements of deformation in northwestern Washington indicate that strain is accumulating at a rate close to that predicted by a model of the Cascadia subduction zone in which the plate interface underlying the continental slope and outer continental shelf is currently locked but the remainder of the interface slips continuously. Presumably this locked segment will eventually rupture in a great thrust earthquake with a down-dip extent greater than 100 kilometers.

Washington↗
USGS1987

Unconformity between Coast Range ophiolite and part of the lower Great Valley sequence, South Fork of Elder Creek, Tehama County, California

The South Fork of Elder Creek is located on private property about 6 mi (10 km) northwest of Paskenta, Calif. (Fig. 1). To visit this locality it is necessary to call Mr. Les Sutfin (916-824-4628) and arrange to pick up the key to the gate at his home in Corning. From the Paskenta Store, drive 3.3 mi (5.3 km) north on the Toomes Camp road to the locked gate on the north side of the road. From here, take the Pellows Road (four-wheel drive vehicle recommended) 3.6 mi (5 km) north to the end of the road, then walk west along the trail parallel to the South Fork of Elder Creek for approximately 0.5 mi (0.8 km) to the unconformity(Fig. 2).

DNAG Special Publication↗