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At least 1,477 records · Page 82Linked to original sources
USGS2009

Simulating and understanding sand wave variation: A case study of the Golden Gate sand waves

In this paper we present a detailed comparison between measured features of the Golden Gate sand wave field and the results of a nonlinear sand wave model. Because the Golden Gate sand waves exhibit large variation in their characteristics and in their environmental physics, this area gives us the opportunity to study sand wave variation between locations, within one well-measured, large area. The nonlinear model used in this paper is presently the only tool that provides information on the nonlinear evolution of large-amplitude sand waves. The model is used to increase our understanding of the coupling between the variability in environmental conditions and the sand wave characteristics. Results show that the model is able to describe the variation in the Golden Gate sand waves well when both the local oscillating tidal current and the residual current are taken into account. Current and water depth seem to be the most important factors influencing sand wave characteristics. The simulation results give further confidence in the underlying model hypothesis and assumptions. Copyright 2009 by the American Geophysical Union.

Journal of Geophysical Research F: Earth Surface↗
USGS2019

Application of a towed time-domain electromagnetic (tTEM) imaging system in Jamestown, North Dakota

Time-Domain Electromagnetic (EM) methods have been used for decades in support of groundwater investigations. A new towed Time-Domain EM system called “tTEM”, designed by Aarhus University, is being tested and evaluated under a collaborative research agreement with the U.S. Geological Survey (USGS). The tTEM system is rapid and efficient, providing high-resolution, nearly continuous profiles of subsurface resistivity useful for hydrostratigraphic mapping and assessment of aquifer materials. Here we provide an example of a tTEM survey conducted in Jamestown, North Dakota (ND). The purpose of the ND investigation was to assess tTEM the ability of the system to map coarse-grained materials within the Spiritwood Aquifer. The tTEM survey results compare favorably with the results of an airborne EM (AEM) survey previously conducted in the area and to lithologic logs from nearby boreholes.

North Dakota↗
USGS2009

Discharge and other hydraulic measurements for characterizing the hydraulics of Lower Congo River

The first direct measurements of discharge of the Lower Congo River below Malebo Pool and upstream from Kinganga, Democratic Republic of Congo (DRC) were made in July 2008 using acoustic Doppler current profilers, differential GPS, and echo sounders. These measurements were made in support of research that is attempting to understand the distribution of fish species in the Lower Congo River and reasons for separation of species within this large river. Analyses of these measurements show that the maximum depth in the Lower Congo River was in excess of 200 m and maximum water velocities were greater than 4 m/s. The discharge measured near Luozi, DRC was 35,800 m3/s, and decreased slightly beginning midway through the study. Local bedrock controls seem to have a large effect on the flow in the river, even in reaches without waterfalls and rapids. Dramatic changes in bed topography are evident in transects across the river.

Congo River and Malebo Pool↗
USGS2016

Defining resilience: A preliminary integrative literature review

The term “resilience” is ubiquitous in technical literature; it appears in numerous forms, such as resilience, resiliency, or resilient, and each use may have a different definition depending on the interpretation of the writer. This creates difficulties in understanding what is meant by ‘resilience’ in any given use case, especially in discussions of interdisciplinary research. To better understand this problem, this research constructs a preliminary integrative literature review to map different definitions, applications and calculation methods of resilience invoked within critical infrastructure applications. The preliminary review uses a State-of-the-Art Matrix (SAM) analysis to characterize differences in definition across disciplines and between regions. Qualifying the various usages of resilience will produce a greater precision in the literature and a deeper insight into types of data required for its evaluation, particularly with respect to critical infrastructure calculations and how such data may be analyzed. Results from this SAM analysis will create a framework of key concepts as part of the most common applications for “resilient critical infrastructure” modeling.

Conference Paper↗
USGS2010

Depth-averaging effects on hydraulic head for media with stochastic hydraulic conductivity

Hydraulic conductivity of a porous medium frequently is considered to be a single realization of a three-dimensional spatial stochastic process. The most common observations of flow in porous media are hydraulic-head measurements obtained from wells which are screened over extensive sections of the medium. These measurements represent, approximately, a one-dimensional spatial average of the actual three-dimensional head distribution, the actual head distribution being a stochastic process resulting from flow through a random hydraulic-conductivity field. This paper examines, via ensemble averages, the effect of such spatial averages of groundwater flow on the spatial autocovariance function for a simple, yet viable, stochastic model of a bounded medium. The model is taken to be three-dimensional flow in a medium that is bounded above and below and in which the hydraulic conductivity is a second-order stationary stochastic process. Spatial averaging of the hydraulic heads is considered to take place over the entire thickness of the medium. Ensemble variances and autocorrelations for depth-averaged heads are computed for the resulting two-dimensional flow system and compared with those from a fully three-dimensional flow system.

Water Resources Research↗
USGS2019

Enabling real-time user interaction for decision support: Experiences extending a local agave platform metadata service

The University of Hawai'i Information Technology Services Cyber-infrastructure team in partnership with the United States Geological Survey developed the Hawai'i groundwater recharge tool, a decision support tool, as part of the 'Ike Wai Gateway to support water sustainability research for the state of Hawai'i. To enable the development of the tool within the existing University of Hawai'i Agave platform that the 'Ike Wai Gateway is built on, the Metadata application programmatic interface (API) and Agave infrastructure needed to be extended to store and retrieve spatial data and handle a larger number of requests. The development team successfully added the functionality to the local University of Hawai'i Agave platform instance to support the storage of deserialized vector data and metadata that can be spatially queried across hundreds of thousands of records to enable decision support applications within a science gateway.

Hawaii↗
USGS2005

Analyzing indicators of stream health for Minnesota streams

Recent research has emphasized the importance of using physical, chemical, and biological indicators of stream health for diagnosing impaired watersheds and their receiving water bodies. A multidisciplinary team at the University of Minnesota is carrying out research to develop a stream classification system for Total Maximum Daily Load (TMDL) assessment. Funding for this research is provided by the United States Environmental Protection Agency and the Minnesota Pollution Control Agency. One objective of the research study involves investigating the relationships between indicators of stream health and localized stream characteristics. Measured data from Minnesota streams collected by various government and non-government agencies and research institutions have been obtained for the research study. Innovative Geographic Information Systems tools developed by the Environmental Science Research Institute and the University of Texas are being utilized to combine and organize the data. Simple linear relationships between index of biological integrity (IBI) and channel slope, two-year stream flow, and drainage area are presented for the Redwood River and the Snake River Basins. Results suggest that more rigorous techniques are needed to successfully capture trends in IBI scores. Additional analyses will be done using multiple regression, principal component analysis, and clustering techniques. Uncovering key independent variables and understanding how they fit together to influence stream health are critical in the development of a stream classification for TMDL assessment.

Conference Paper↗
USGS1997

Community involvement in a multimedia outreach project for Caddo Lake, Texas

Caddo Lake is located in northeast Texas and northwest Louisiana and is the largest freshwater lake in Texas. A portion of the lake in Texas has been designated a "Wetland of International Significance" under the Ramsar Convention of the United Nations. The human community in the watershed has experienced a number of hydrological alterations to Caddo Lake over the last 100 years by the Federal Government. Thus, many landowners in the area have become organized to protect Caddo Lake against what some view as harmful further alterations. In 1992, the U.S. Congress appropriated funds for an initiative to conduct baseline studies of the natural resources of Caddo Lake in order to foster ecotourism and economic development in the surrounding counties. For the information gathering part of the initiative and in response to negative criticism of the Caddo Lake Initiative expressed at a public meeting, the U.S. Geological Survey's National Wetlands Research Center invited public participation in developing a multimedia outreach system to improve the understanding of the natural resources at Caddo Lake and provide information about the studies. In the development of the outreach system we sought to strengthen working relationships with the State of Texas, local governments, and grassroots citizens groups. The outreach system consisted of an MS Windows-based interactive CD-ROM package that incorporated pictures, sound, animation, and video footage of the lake and the local culture. Public involvement in system development served as a catalyst for changing community perceptions about Federal and states studies at Caddo Lake and fostered community endorsement of the Caddo Lake Initiative.

Texas↗
USGS2021

Managing nonperennial headwater streams in temperate forests of the United States

Forest management guidelines are designed to protect water quality from unintended effects of land use changes such as timber harvest, mining, or forest road construction. Although streams that periodically cease to flow (nonperennial) drain the majority of forested areas, these streams are not consistently included in forest management guidelines. This paper reviews management guidelines for nonperennial (intermittent and ephemeral) streams draining temperate forests in the continental U.S., evaluates potential impacts of land use activities on ecosystem services provided by these streams, and identifies information needed to incorporate nonperennial streams into water quality protection practices. For federally administered lands, national management guidance is deliberately nonprescriptive, deferring to regional and forest-level recommendations for both perennial and nonperennial streams. Most state guidelines recommend riparian management zone (RMZ) protection for perennial streams (48/50 states) and intermittent streams (45/50 states), but only Alaska and West Virginia require RMZs around ephemeral streams. Based on the National Hydrography Dataset, an average of 58% of forested land area in the U.S. drains to nonperennial headwater streams, making these stream types the most common connectors between forested lands and the aquatic system. Land uses that modify flow regimes in these streams can affect sediment and organic matter transport and distribution, stream temperature dynamics, and biogeochemical processing. Nonperennial streams also provide material subsidies to downstream waters and serve as temporary habitats for some aquatic species. However, limited research has examined how forest land uses affect ecosystem services and biota in these streams. Therefore we highlight a set of key questions about nonperennial streams in forests, not the least of which is simply understanding where headwater stream channels are located and associated patterns of flow duration. Although many questions remain, we also note where recent advances in data collection, modeling and process-level research provide opportunities to resolve uncertainties around nonperennial streams in forested landscapes of the continental U.S.

Forest Ecology and Management↗
USGS2024

Evaluating effectiveness of restoration to address current stressors to riverine fish

River restoration programmes with the goal of conserving and rehabilitating inland fishes have a multi-decadal history, but evaluation and synthesis of past restoration actions have been limited by a lack of monitoring and reporting. Given that calls for both monitoring and systematic reviews of restoration have increased, we were interested in the influence that restoration has had on improving conditions for riverine fishes resulting from long-standing and increasingly prominent stressors. Our objectives were to (1) identify which stressors were targeted in river restoration efforts, (2) determine the proportion of published studies that articulate restoration goals and develop comparative monitoring designs for assessing the effects of restoration on fishes, and (3) conduct a meta-analysis to synthesise fish responses to restoration projects. We assessed restoration effectiveness for increasing fish density and richness from peer-reviewed papers published over the past decade using a global systematic review and meta-analysis. We found that restoration actions addressed major stressors primarily by improving in-stream habitat (37%), increasing in-stream longitudinal connectivity (26%) and increasing lateral floodplain connections (9%). Although 81% of studies had comparative monitoring designs (i.e., before/after and control/impact) and stated restoration goals, only 40% of those studies reported sufficient data to be included in the meta-analysis. Projects which increased in-stream connectivity had the largest positive effect size on fish density and richness compared to in-stream habitat improvements and increasing floodplain connections. Time since restoration and restoration size (i.e., geographical footprint) were not strong predictors of fish response effect sizes. Restoration effectiveness was highly variable among project types. Authors of studies included in the meta-analysis often identified spatial or temporal scale of monitoring, overriding catchment conditions, and recolonisation potential as sources of variability and effectiveness in restoration outcomes. Systematic reporting of these and other covariates may help guide processes in restoration evaluation and provide valuable research insights. Despite increased emphasis on monitoring, incomplete data reporting limited the number of studies that could be included for quantitative meta-analysis. Persistent emphasis on setting specific criteria (e.g., measurable outcomes of fish response) for restoration goals, project monitoring, data reporting, information sharing and collaborative projects is likely to continue to improve understanding of restoration effectiveness transferable to future endeavours. Our results can be used to support river restoration practitioners with evidence-based information to evaluate the cost–benefit ratio of competing restoration priorities, and inform restoration planning and implementation for riverine fish.

Freshwater Biology↗
USGS2019

Spatial and temporal variability in ripple formation and migration across a coral reef flat and lagoon

The transport of carbonate sediment across reefs to the shoreline is of great interest to the research community and coastal managers alike. This sediment is generated by the breakdown of reef skeletal structure and a critical source for beach nourishment that provides a buffer to coastal flooding as sea levels rise. Understanding the physical processes that are responsible for this flux of sediment to the coast is therefore necessary before we can begin to predict how it may be affected by rising sea levels. Six weeks of high quality physical oceanographic data collected on the fringing reef in the Jurabi UNESCO World Heritage Site in Western Australia provides the opportunity to examine these processes in greater detail than ever before.

Jurabi UNESCO World Heritage Site↗
USGS1989

Guide for selecting Manning's roughness coefficients for natural channels and flood plains

Although much research has been done on Manning's roughness coefficient, n, for stream channels, very little has been done concerning the roughness values for densely vegetated flood plains. The n value is determined from the values of the factors that affect the roughness of channels and flood plains. In densely vegetated flood plains, the major roughness is caused by trees, vines, and brush. The n value for this type of flood plain can be determined by measuring the vegetation density of the flood plain. Photographs of flood-plain segments where n values have been verified can be used as a comparison standard to aid in assigning n values to similar flood plains.

Water Supply Paper↗
USGS1995

Survival and population size estimation in raptor studies: A comparison of two methods

ABSTRACT.--The Jolly-Seber model is a capture-recapture model that can provide less-biased survival and population size estimates than those produced from simple counting procedures. Parameter estimation by simple counts and Jolly-Seber methods are based on certain assumptions that directly determine the validity of estimates. Evuluation of assumptions for parameter estimation is a focus of this paper and used as a basis for determining which methods are more likely to produce better estimates. An example of population size and survival estimation for a peregrine falcon(Falco peregrinus) population in western Greenland is used to compare the two methods.Based on results from the Greenland peregrine population, and an assessment of the underlying assumptions of simple counts and the Jolly-Seber model,we suggest that Jolly-Seber estimation of survival and population size is less biased than simple counts in studies with marked birds. We recommend the use of a Jolly-Seber analysis of data when capture-recapture techniques are employed in raptor population studies.

Journal of Raptor Research↗
USGS2010

Herbicide treatment of invasive Vinca major growing with endangered Galium buxifolium, an island endemic

Galium buxifolium E. Greene [Rubiaceae] (sea-cliff bedstraw) is a small shrub restricted to San Miguel and Santa Cruz Islands, in the California Channel Islands. Almost all of the 26 known populations grow on vertical north-facing sea cliffs in native scrub, sandwiched between the sea below and non-native annual grasslands on the terraces above. A notable exception is a popula?tion at Pelican Bay on Santa Cruz Island, growing on the cliff and on thin terrace soils above the cliff in a stand of coastal bluff scrub that is recovering from more than a century of sheep grazing (Figure 1). Ironically, this stand is near the location of the historic Eaton Resort, a charismatic inn frequented by Hollywood glitterati in the early 1900s. Several landscape ornamentals planted there persist today in the area of the Galium population. Italian stone pine (Pinus pinaea) and eucalyptus (Eucalyptus spp.) tower over the site while the invasive groundcover Vinca major L. [Apocynaceae] (greater periwinkle) forms dense mats at the cliff edge that are spreading into the developing native plant stand. Wherever the Galium is found it is intermixed with other native scrub plants in dense communities on moist ocean bluffs. Historic notes and herbarium collections indicate that it may have been more widespread on nearshore terraces adjacent to sea-cliff populations before conversion to grassland. Since Pelican Bay is the only site that we know of where Galium is spreading onto the nearby terrace, we wanted to know whether the Vinca posed a roadblock to upslope population expansion. In 2005 we mapped Vinca and Galium at the site. We also measured Galium individuals to see where the smaller, younger plants were to better understand where the population is expanding. We observed that 1) both the Galium and the Vinca appear to be spreading from the cliff face upslope onto a series of rock outcrops, stone walls and benches, 2) the native scrub community is recovering at the site and 3) the Vinca appears to be moving into the native scrub where it overtops small plants, including those Galium in the smallest size classes. This observed pattern of Vinca displacement of native vegetation has been noted in other places, where it is treated as an invasive weed. We concluded that Vinca may pose a threat to the expansion of both the native scrub and the Galium population that it supports. Therefore, we worked with the US Fish and Wildlife Service and others to develop a research project investigating 1) best techniques for killing Vinca within the boundaries of an endangered plant population and 2) demographic response of Galium to the treatment. Our intent is to push Vinca back to the vertical cliff face to give the natives a chance to establish a vigorous stand. Our conservation goal is to encourage natural establishment of new Galium plants on the terrace along with expansion of the native coastal bluff scrub and Galium population. Our immediate treatment objective is to reduce live Vinca cover by 90 % on the accessible upslope portions of the habitat. Our recovery objective is no net loss of Galium plants 2006-2016.

California↗
USGS2009

Effects of hydrologic infrastructure on flow regimes of California's Central Valley rivers: Implications for fish populations

Alteration of natural flow regimes is generally acknowledged to have negative effects on native biota; however, methods for defining ecologically appropriate flow regimes in managed river systems are only beginning to be developed. Understanding how past and present water management has affected rivers is an important part of developing such tools. In this paper, we evaluate how existing hydrologic infrastructure and management affect streamflow characteristics of rivers in the Central Valley, California and discuss those characteristics in the context of habitat requirements of native and alien fishes. We evaluated the effects of water management by comparing observed discharges with estimated discharges assuming no water management ("full natural runoff"). Rivers in the Sacramento River drainage were characterized by reduced winter–spring discharges and augmented discharges in other months. Rivers in the San Joaquin River drainage were characterized by reduced discharges in all months but particularly in winter and spring. Two largely unaltered streams had hydrographs similar to those based on full natural runoff of the regulated rivers. The reduced discharges in the San Joaquin River drainage streams are favourable for spawning of many alien species, which is consistent with observed patterns of fish distribution and abundance in the Central Valley. However, other factors, such as water temperature, are also important to the relative success of native and alien resident fishes. As water management changes in response to climate change and societal demands, interdisciplinary programs of research and monitoring will be essential for anticipating effects on fishes and to avoid unanticipated ecological outcomes.

California↗
USGS2007

Coastal-Change and Glaciological Map of the Northern Ross Ice Shelf Area, Antarctica: 1962-2004

Changes in the area and volume of polar ice sheets are intricately linked to changes in global climate, and the resulting changes in sea level could severely impact the densely populated coastal regions on Earth. Melting of the West Antarctic part alone of the Antarctic ice sheet would cause a sea-level rise of approximately 6 meters (m). The potential sea-level rise after melting of the entire Antarctic ice sheet is estimated to be 65 m (Lythe and others, 2001) to 73 m (Williams and Hall, 1993). The mass balance (the net volumetric gain or loss) of the Antarctic ice sheet is highly complex, responding differently to different conditions in each region (Vaughan, 2005). In a review paper, Rignot and Thomas (2002) concluded that the West Antarctic ice sheet is probably becoming thinner overall; although it is thickening in the west, it is thinning in the north. Thomas and others (2004), on the basis of aircraft and satellite laser altimetry surveys, believe the thinning may be accelerating. Joughin and Tulaczyk (2002), on the basis of analysis of ice-flow velocities derived from synthetic aperture radar, concluded that most of the Ross ice streams (ice streams on the east side of the Ross Ice Shelf) have a positive mass balance, whereas Rignot and others (2004) infer even larger negative mass balance for glaciers flowing northward into the Amundsen Sea, a trend suggested by Swithinbank and others (2003a,b; 2004). The mass balance of the East Antarctic ice sheet is thought by Davis and others (2005) to be strongly positive on the basis of the change in satellite altimetry measurements made between 1992 and 2003. Measurement of changes in area and mass balance of the Antarctic ice sheet was given a very high priority in recommendations by the Polar Research Board of the National Research Council (1986), in subsequent recommendations by the Scientific Committee on Antarctic Research (SCAR) (1989, 1993), and by the National Science Foundation?s (1990) Division of Polar Programs. On the basis of these recommendations, the U.S. Geological Survey (USGS) decided that the archive of early 1970s Landsat 1, 2, and 3 Multispectral Scanner (MSS) images of Antarctica and the subsequent repeat coverage made possible with Landsat and other satellite images provided an excellent means of documenting changes in the coastline of Antarctica (Ferrigno and Gould, 1987). The availability of this information provided the impetus for carrying out a comprehensive analysis of the glaciological features of the coastal regions and changes in ice fronts of Antarctica (Swithinbank, 1988; Williams and Ferrigno, 1988). The project was later modified to include Landsat 4 and 5 MSS and Thematic Mapper (TM) images (and in some areas Landsat 7 Enhanced Thematic Mapper Plus [ETM+] images), RADARSAT images, and other data where available, in order to compare changes that occurred during a 20- to 25- or 30-year time interval (or longer where data were available, as in the Antarctic Peninsula). The results of the analysis are being used to produce a digital database and a series of USGS Geologic Investigations Series Maps (I?2600) (Williams and others, 1995; Williams and Ferrigno, 1998; Ferrigno and others, 2002) (available online at http://www.glaciers.er.usgs.gov).

IMAP↗
USGS2024

Segment anything model can not segment anything: Assessing AI foundation model's generalizability in permafrost mapping

This paper assesses trending AI foundation models, especially emerging computer vision foundation models and their performance in natural landscape feature segmentation. While the term foundation model has quickly garnered interest from the geospatial domain, its definition remains vague. Hence, this paper will first introduce AI foundation models and their defining characteristics. Built upon the tremendous success achieved by Large Language Models (LLMs) as the foundation models for language tasks, this paper discusses the challenges of building foundation models for geospatial artificial intelligence (GeoAI) vision tasks. To evaluate the performance of large AI vision models, especially Meta’s Segment Anything Model (SAM), we implemented different instance segmentation pipelines that minimize the changes to SAM to leverage its power as a foundation model. A series of prompt strategies were developed to test SAM’s performance regarding its theoretical upper bound of predictive accuracy, zero-shot performance, and domain adaptability through fine-tuning. The analysis used two permafrost feature datasets, ice-wedge polygons and retrogressive thaw slumps because (1) these landform features are more challenging to segment than man-made features due to their complicated formation mechanisms, diverse forms, and vague boundaries; (2) their presence and changes are important indicators for Arctic warming and climate change. The results show that although promising, SAM still has room for improvement to support AI-augmented terrain mapping. The spatial and domain generalizability of this finding is further validated using a more general dataset EuroCrops for agricultural field mapping. Finally, we discuss future research directions that strengthen SAM’s applicability in challenging geospatial domains.

Remote Sensing↗
USGS2013

Commercial possibilities for stranded conventional gas from Alaska's North Slope

Stranded gas resources are defined for this study as gas resources in discrete accumulations that are not currently commercially producible, or producible at full potential, for either physical or economic reasons. Approximately 35 trillion cubic feet (TCF) of stranded gas was identified on Alaska’s North Slope. The commercialization of this resource requires facilities to transport gas to markets where sales revenue will be sufficient to offset the cost of constructing and operating a gas delivery system. With the advent of the shale gas revolution, plans for a gas pipeline to the conterminous US have been shelved (at least temporarily) and the State and resource owners are considering a liquefied natural gas (LNG) export project that targets Asian markets. This paper focuses on competitive conditions for Asian gas import markets by estimating delivered costs of competing supplies from central Asia, Russia, Indonesia, Malaysia, and Australia in the context of a range of import gas demand projections for the period from 2020 to 2040. These suppliers’ costs are based on the cost of developing, producing, and delivering to markets tranches of the nearly 600 TCF of recoverable gas from their own conventional stranded gas fields. The results of these analyses imply that Alaska’s gas exports to Asia will likely encounter substantial competitive challenges. The sustainability of Asia’s oil-indexed LNG pricing is also discussed in light of a potentially intense level of competition.

Alaska↗