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At least 1,279 records · Page 71Linked to original sources
USGS2000

MODFLOW-2000, The U.S. Geological Survey modular ground-water model: User guide to modularization concepts and the ground-water flow process

MODFLOW is a computer program that numerically solves the three-dimensional ground-water flow equation for a porous medium by using a finite-difference method. Although MODFLOW was designed to be easily enhanced, the design was oriented toward additions to the ground-water flow equation. Frequently there is a need to solve additional equations; for example, transport equations and equations for estimating parameter values that produce the closest match between model-calculated heads and flows and measured values. This report documents a new version of MODFLOW, called MODFLOW-2000, which is designed to accommodate the solution of equations in addition to the ground-water flow equation. This report is a user's manual. It contains an overview of the old and added design concepts, documents one new package, and contains input instructions for using the model to solve the ground-water flow equation.

Open-File Report↗
USGS2003

Processing large remote sensing image data sets on Beowulf clusters

High-performance computing is often concerned with the speed at which floating- point calculations can be performed. The architectures of many parallel computers and/or their network topologies are based on these investigations. Often, benchmarks resulting from these investigations are compiled with little regard to how a large dataset would move about in these systems. This part of the Beowulf study addresses that concern by looking at specific applications software and system-level modifications. Applications include an implementation of a smoothing filter for time-series data, a parallel implementation of the decision tree algorithm used in the Landcover Characterization project, a parallel Kriging algorithm used to fit point data collected in the field on invasive species to a regular grid, and modifications to the Beowulf project's resampling algorithm to handle larger, higher resolution datasets at a national scale. Systems-level investigations include a feasibility study on Flat Neighborhood Networks and modifications of that concept with Parallel File Systems.

Open-File Report↗
USGS2004

Monitoring Colonias Development along the United States-Mexico Border: A Process Application using GIS and Remote Sensing in Douglas, Arizona, and Agua Prieta, Sonora

The U.S. Department of Housing and Urban Development (HUD) and the U.S. Geological Survey (USGS) have developed a joint project to create Internet-enabled geographic information systems (GIS) that will help cities along the United States-Mexico border deal with issues related to colonias. HUD defines colonias as rural neighborhoods in the United States-Mexico border region that lack adequate infrastructure or housing and other basic services. They typically have high poverty rates that make it difficult for residents to pay for roads, sanitary water and sewer systems, decent housing, street lighting, and other services through assessment. Many Federal agencies recognize colonias designations and provide funding assistance. It is the intention of this project to empower Arizona-Sonora borderland neighborhoods and community members by recognizing them as colonias. This recognition will result in eligibility for available economic subsidies and accessibility to geospatial tools and information for urban planning. The steps to achieve this goal include delineation of colonia-like neighborhoods, identification of their urbanization over time, development of geospatial databases describing their infrastructure, and establishment of a framework for distributing Web-based GIS decision support systems. A combination of imagery and infrastructure information was used to help delineate colonia boundaries. A land-use change analysis, focused on urbanization in the cities over a 30-year timeframe, was implemented. The results of this project are being served over the Internet, providing data to the public as well as to participating agencies. One of the initial study areas for this project was the City of Douglas, Ariz., and its Mexican sister-city Agua Prieta, Sonora, which are described herein. Because of its location on the border, this twin-cities area is especially well suited to international manufacturing and commerce, which has, in turn, led to an uncontrolled spread of colonias. The USGS worked with local organizations in developing the Web-based GIS database. Community involvement ensured that the database and map server would meet the current and long-term needs of the communities and end users. Partners include Federal agencies, State agencies, county officials, town representatives, universities, and youth organizations, as well as interested local advocacy groups and individuals. A significant component of this project was development of relationships and partnerships in the border towns for facilitating binational approaches to land management.

Open-File Report↗
USGS2005

Field guide to the major organisms and processes building reefs and islands of the Dry Tortugas: the Carnegie Dry Tortugas Laboratory Centennial Celebration (1905-2005)

This guide to the geology and biology of the Dry Tortugas is divided into four sections: 1) geologic and anthropogenic features you will pass on your trip to and from the Tortugas, 2) a summary of items of Tortugas geologic, historic, and human interest and what you will experience at Loggerhead Key while walking and snorkeling, 3) a summary of recent coral-monitoring results, and 4) an Appendix with tributes to some of the significant research accomplishments of researchers at the laboratory between 1905 and 1939.

Florida↗
USGS2006

Processed 1938 aerial photography for selected areas of the lower Colorado River, southwestern United States

The U.S. Geological Survey (USGS) initiated a study of the Lower Colorado River to derive temporal-change characteristics from the predam period to the present. In this report, we present summary information on accomplishments under a USGS task for the Department of the Interior's Landscapes in the West project. We discuss our preliminary results in compiling a digital database of geospatial information on the Lower Colorado River and acquisition of data products, and present a geospatial digital dataset of 1938 aerial photography of the river valley. The U.S. Bureau of Reclamation (BOR)'s, Resources Management Office in Boulder City, Nev., provided historical aerial photographs of the river valley from the Hoover Dam to the United States-Mexican border, with some exclusions. USGS authors scanned and mosaicked the photographs, registered the photo mosaics, and created metadata describing each mosaic series, all 15 of which are presented here.

Open-File Report↗
USGS2007

Sea-floor character and surface processes in the vicinity of Quicks Hole, Elizabeth Islands, Massachusetts

The U.S. Geological Survey (USGS), in cooperation with the National Oceanic and Atmospheric Administration (NOAA) and the Massachusetts Office of Coastal Zone Management (MA CZM), is producing detailed geologic maps of the coastal sea floor. The imagery, interpretive data layers, and data presented herein were derived from multibeam echo-sounder and sidescan sonar surveys conducted in the vicinity of Quicks Hole, a passage through the Elizabeth Islands, which extend in a chain southwest off Cape Cod, Massachusetts, and from the stations occupied to verify these acoustic data (fig. 1). Basic data layers show sea-floor topography, sun-illuminated shaded relief, and backscatter intensity; interpretive layers show the distributions of surficial sediment, sedimentary environments, and sea-floor features. Presented verification data include sediment grain-size analyses and a gallery of still photographs of the seabed. The multibeam and sidescan data, which cover an approximately 22.9-km 2 area of sea floor that extends from Vineyard Sound on the south to Buzzards Bay on the north, were collected during NOAA hydrographic survey H11076 (fig. 1). Although originally collected for charting purposes, these data provide a fundamental framework for research and management activities along this part of the Massachusetts coastline (Noji and others, 2004), show the composition and terrain of the seabed, and provide information on sediment transport and benthic habitat.

Massachusetts↗
USGS2007

Jurassic silicic volcanism in the Transantarctic Mountains: Was it related to plate margin processes or to Ferrar magmatism?

Silicic volcanism in the Transantarctic Mountains, represented by rhyolitic tuff that mainly precedes emplacement of the Ferrar Large Igneous Province, is important in interpretation of the tectonic evolution of the Antarctic sector of Gondwana. Sr and Nd isotope data indicate that the tuffs are not directly related to Ferrar magmatism nor to melting of the underlying Ross orogen crust yet zircon gives a U-Pb age of 182.7±1.8 Ma, similar to the U/Pb age for the Ferrar. Distribution of the silicic tuffs along 1400 km of the Transantarctic Mountains suggests, alternatively, a relationship to the Gondwana plate margin. Although West Antarctica comprises Mesoproterozoic crustal terrains, few analyzed rocks are compatible isotopically with the Lower Jurassic tuffs. The source of the tuffs must lie in unexposed Early Jurassic magmatic centers in West Antarctica or an unexposed crustal terrain beneath the Transantarctic Mountains.

Open-File Report↗
USGS2007

Sea-floor character and sedimentary processes of Great Round Shoal Channel, offshore Massachusetts

The imagery, interpretive data layers, and data presented herein were derived from multibeam echo-sounder and sidescan-sonar data collected in the vicinity of Great Round Shoal Channel, the main passage through shoals located at the eastern entrance to Nantucket Sound, Massachusetts, and from the stations occupied to verify these acoustic data (fig. 1). Basic data layers show sea-floor topography, sun-illuminated shaded relief, and backscatter intensity; interpretive layers show the distributions of surficial sediment, sedimentary environments, and sea-floor features. Presented verification data include sediment grain-size analyses and a gallery of still photographs of the seabed. The multibeam and sidescan data, which together cover an approximately 39.9-km² area of sea floor, were collected during National Oceanic and Atmospheric Administration (NOAA) hydrographic survey H11079 (fig. 1). Although originally collected for charting purposes, these data provide a fundamental framework for research and management activities along this part of the Massachusetts coastline (Noji and others, 2004), show the composition and terrain of the seabed, and provide information on sediment transport and benthic habitat. This publication is the third in a series of U.S. Geological Survey (USGS) digital reports describing the sea-floor geology around Cape Cod. The first focused on the area off the eastern shore of the outer Cape (Poppe and others, 2006); the second on a passage through the Elizabeth Islands (Poppe and others, 2007).

Massachusetts↗
USGS2010

Thermal Imaging of the Waccasassa Bay Preserve: Image Acquisition and Processing

Thermal infrared (TIR) imagery was acquired along coastal Levy County, Florida, in March 2009 with the goal of identifying groundwater-discharge locations in Waccasassa Bay Preserve State Park (WBPSP). Groundwater discharge is thermally distinct in winter when Floridan aquifer temperature, 71-72 degrees F, contrasts with the surrounding cold surface waters. Calibrated imagery was analyzed to assess temperature anomalies and related thermal traces. The influence of warm Gulf water and image artifacts on small features was successfully constrained by image evaluation in three separate zones: Creeks, Bay, and Gulf. Four levels of significant water-temperature anomalies were identified, and 488 sites of interest were mapped. Among the sites identified, at least 80 were determined to be associated with image artifacts and human activity, such as excavation pits and the Florida Barge Canal. Sites of interest were evaluated for geographic concentration and isolation. High site densities, indicating interconnectivity and prevailing flow, were located at Corrigan Reef, No. 4 Channel, Winzy Creek, Cow Creek, Withlacoochee River, and at excavation sites. In other areas, low to moderate site density indicates the presence of independent vents and unique flow paths. A directional distribution assessment of natural seep features produced a northwest trend closely matching the strike direction of regional faults. Naturally occurring seeps were located in karst ponds and tidal creeks, and several submerged sites were detected in Waccasassa River and Bay, representing the first documentation of submarine vents in the Waccasassa region. Drought conditions throughout the region placed constraints on positive feature identification. Low discharge or displacement by landward movement of saltwater may have reduced or reversed flow during this season. Approximately two-thirds of seep locations in the overlap between 2009 and 2005 TIR night imagery were positively re-identified in 2009. These results indicate a 33 percent chance of feature omission in the 2009 imagery. This assessment of seep location and distribution contributes to an understanding of the underlying geology, the role of fault and fracture patterns, and the presence of both interconnected and constrained flow paths in the region. The maps and evaluations will enhance Park management efforts, interpretation of Park resources, and increase understanding of the combined effects of land and water use on the coastal lowlands, estuarine habitats, and natural resources of WBPSP.

Open-File Report↗
USGS2010

Biogeochemical processes in an urban, restored wetland of San Francisco Bay, California, 2007-2009: Methods and data for plant, sediment and water parameters

The restoration of 18 acres of historic tidal marsh at Crissy Field has had great success in terms of public outreach and visibility, but less success in terms of revegetated marsh sustainability. Native cordgrass (Spartina foliosa) has experienced dieback and has failed to recolonize following extended flooding events during unintended periodic closures of its inlet channel, which inhibits daily tidal flushing. We examined the biogeochemical impacts of these impoundment events on plant physiology and on sulfur and mercury chemistry to help the National Park Service land managers determine the relative influence of these inlet closures on marsh function. In this comparative study, we examined key pools of sulfur, mercury, and carbon compounds both during and between closure events. Further, we estimated the net hydrodynamic flux of methylmercury and total mercury to and from the marsh during a 24-hour diurnal cycle. This report documents the methods used and the data generated during the study.

California↗