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At least 685 records · Page 38Linked to original sources
USGS2016

Discussion of “The relation between dilatancy, effective stress and dispersive pressure in granular avalanches” by P. Bartelt and O. Buser (DOI: 10.1007/s11440-016-0463-7)

A paper recently published by Bartelt and Buser (hereafter identified as “the authors”) aims to clarify relationships between granular dilatancy and dispersive pressure and to question the effective stress principle and its application to shallow granular avalanches (Bartelt and Buser in Act Geotech 11:549–557, 2 ). The paper also criticizes our own recent work, which utilizes the concepts of evolving dilatancy and effective stress to model the initiation and dynamics of water-saturated landslides and debris flows. Here we first explain why we largely agree with the authors’ views of dilatancy and dispersive pressure as they apply to depth-integrated granular avalanche models, and why we disagree with their views of effective stress and pore-fluid pressure. We conclude by explaining why the authors’ characterization of our recently developed D-Claw model is inaccurate.

Acta Geotechnica↗
USGS1999

Simulation of scenario earthquake influenced field by using GIS

The method for estimating the site effect on ground motion specified by Borcherdt (1994a, 1994b) is briefly introduced in the paper. This method and the detail geological data and site classification data in San Francisco bay area of California, the United States, are applied to simulate the influenced field of scenario earthquake by GIS technology, and the software for simulating has been drawn up. The paper is a partial result of cooperative research project between China Seismological Bureau and US Geological Survey.

California↗
USGS2023

Bringing the Nature Futures Framework to life: Creating a set of illustrative narratives of nature futures

To halt further destruction of the biosphere, most people and societies around the globe need to transform their relationships with nature. The internationally agreed vision under the Convention of Biological Diversity—Living in harmony with nature—is that “By 2050, biodiversity is valued, conserved, restored and wisely used, maintaining ecosystem services, sustaining a healthy planet and delivering benefits essential for all people”. In this context, there are a variety of debates between alternative perspectives on how to achieve this vision. Yet, scenarios and models that are able to explore these debates in the context of “living in harmony with nature” have not been widely developed. To address this gap, the Nature Futures Framework has been developed to catalyse the development of new scenarios and models that embrace a plurality of perspectives on desirable futures for nature and people. In this paper, members of the IPBES task force on scenarios and models provide an example of how the Nature Futures Framework can be implemented for the development of illustrative narratives representing a diversity of desirable nature futures: information that can be used to assess and develop scenarios and models whilst acknowledging the underpinning value perspectives on nature. Here, the term illustrative reflects the multiple ways in which desired nature futures can be captured by these narratives. In addition, to explore the interdependence between narratives, and therefore their potential to be translated into scenarios and models, the six narratives developed here were assessed around three areas of the transformative change debate, specifically, (1) land sparing vs. land sharing, (2) Half Earth vs. Whole Earth conservation, and (3) green growth vs. post-growth economic development. The paper concludes with an assessment of how the Nature Futures Framework could be used to assist in developing and articulating transformative pathways towards desirable nature futures.

Sustainability Science↗
USGS2008

Strong motion observations and recordings from the great Wenchuan Earthquake

The National Strong Motion Observation Network System (NSMONS) of China is briefly introduced in this paper. The NSMONS consists of permanent free-field stations, special observation arrays, mobile observatories and a network management system. During the Wenchuan Earthquake, over 1,400 components of acceleration records were obtained from 460 permanent free-field stations and three arrays for topographical effect and structural response observation in the network system from the main shock, and over 20,000 components of acceleration records from strong aftershocks occurred before August 1, 2008 were also obtained by permanent free-field stations of the NSMONS and 59 mobile instruments quickly deployed after the main shock. The strong motion recordings from the main shock and strong aftershocks are summarized in this paper. In the ground motion recordings, there are over 560 components with peak ground acceleration (PGA) over 10 Gal, the largest being 957.7 Gal. The largest PGA recorded during the aftershock exceeds 300 Gal. ?? 2008 Institute of Engineering Mechanics, China Earthquake Administration and Springer-Verlag GmbH.

Earthquake Engineering and Engineering Vibration↗
USGS2017

Impacts of coastal land use and shoreline armoring on estuarine ecosystems: An introduction to a special issue

The nearshore land-water interface is an important ecological zone that faces anthropogenic pressure from development in coastal regions throughout the world. Coastal waters and estuaries like Chesapeake Bay receive and process land discharges loaded with anthropogenic nutrients and other pollutants that cause eutrophication, hypoxia, and other damage to shallow-water ecosystems. In addition, shorelines are increasingly armored with bulkhead (seawall), riprap, and other structures to protect human infrastructure against the threats of sea-level rise, storm surge, and erosion. Armoring can further influence estuarine and nearshore marine ecosystem functions by degrading water quality, spreading invasive species, and destroying ecologically valuable habitat. These detrimental effects on ecosystem function have ramifications for ecologically and economically important flora and fauna. This special issue of Estuaries and Coasts explores the interacting effects of coastal land use and shoreline armoring on estuarine and coastal marine ecosystems. The majority of papers focus on the Chesapeake Bay region, USA, where 50 major tributaries and an extensive watershed (~ 167,000 km 2 ), provide an ideal model to examine the impacts of human activities at scales ranging from the local shoreline to the entire watershed. The papers consider the influence of watershed land use and natural versus armored shorelines on ecosystem properties and processes as well as on key natural resources.

Estuaries and Coasts↗
USGS2018

Rebuttal to “The case of the Biscayne Bay and aquifer near Miami, Florida: density-driven flow of seawater or gravitationally driven discharge of deep saline groundwater?” by Weyer (Environ Earth Sci 2018, 77:1–16)

A recent paper by Weyer (Environ Earth Sci 2018, 77:1–16) challenges the widely accepted interpretation of groundwater heads and salinities in the coastal Biscayne aquifer near Miami, Florida, USA. Weyer (2018) suggests that the body of saltwater that underlies fresh groundwater just inland of the coast is not a recirculating wedge of seawater, but results instead from upward migration of deep saline groundwater driven by regional flow. Perhaps more significantly, Weyer (2018) also asserts that established hydrologic theory is fundamentally incorrect with respect to buoyancy. Instead of acting along the direction of gravity (that is, vertically), Weyer (2018) claims, buoyancy acts instead along the direction of the pressure gradient. As a result, Weyer (2018) considers currently available density-dependent groundwater flow and transport modeling codes, and the analyses based on them, to be in error. In this rebuttal, we clarify the inaccuracies in the main points of Weyer’s (2018) paper. First, we explain that Weyer (2018) has misinterpreted observed equivalent freshwater heads in the Biscayne aquifer and that his alternative hypothesis concerning the source of the saltwater does not explain the observed salinities. Then, we review the established theory of buoyancy to identify the problem with Weyer’s (2018) alternative theory. Finally, we present theory and cite successful benchmark simulations to affirm the suitability of currently available codes for modeling density-dependent groundwater flow and transport.

Environmental Earth Sciences↗
USGS2016

Midcontinent Prairie-Pothole wetlands and climate change: An Introduction to the Supplemental Issue

The multitude of wetlands in the Prairie Pothole Region of North America forms one of Earth’s largest wetland complexes. The midcontinent location exposes this ecologically and economically important wetland system to a highly variable climate, markedly influencing ponded-water levels, hydroperiods, chemical characteristics, and biota of individual basins. Given their dominance on the landscape and recognized value, great interest in how projected future changes in climate will affect prairie-pothole wetlands has developed and spawned much scientific research. On June 2, 2015, a special symposium, “Midcontinent Prairie-Pothole Wetlands: Influence of a Changed Climate,” was held at the annual meeting of the Society of Wetland Scientists in Providence, Rhode Island, USA. The symposium’s twelve presenters covered a wide range of relevant topics delivered to a standing-room-only audience. Following the symposium, the presenters recognized the need to publish their presented papers as a combined product to facilitate widespread distribution. The need for additional papers to more fully cover the topic of prairie-pothole wetlands and climate change was also identified. This supplemental issue of Wetlands is the realization of that vision.

Prairie Pothole Region↗
USGS2020

Tidal wetland resilience to increased rates of sea level rise in the Chesapeake Bay: Introduction to the special feature

The papers in this Special Feature are the result of the first Marsh Resilience Summit in the Chesapeake Bay region, which occurred in February 2019. The Chesapeake Bay region has one of the highest rates of relative sea level rise in the U.S., jeopardizing over 1000 km 2 of tidal wetlands along with other coastal lands. The goal of the Summit and this collection of articles is to analyze tidal wetland response to accelerating sea level rise and the effect their response will have on adaptation planning for surrounding communities. Ten Summit presenters share their research in this Special Feature. In this Introduction, we summarize their findings on evaluating restoration potential at the site-specific level, measuring and projecting marsh migration and erosions rates, describing impacts of wetland migration on a marsh dependent animal, effects on human communities, and finally the roles of property owners and government on future tidal wetland extent. These contributions demonstrate that tidal marsh distribution is dynamic in response to sea level rise, and that social, legal, and policy tools can be used and further developed to enable opportunities for restoring or conserving wetlands when stakeholders are engaged effectively. The papers here and feedback from Summit participants illuminate diverse priorities, research unknowns, and next steps for land use planning toward resilience of the Chesapeake Bay region that also can inform global communities.

Maryland, Virgina↗
USGS2020

Ecological interfaces between land and flowing water: Themes and trends in riparian research and management

This paper provides an overview of past, present and future themes for research and management of riparian zones, often relating to papers within this Wetlands Special Feature. Riparian research expanded in the United States around 1980 with themes that recognized (1) damage from excessive livestock, or (2) damage from river damming and diversion, and (3) the beneficial capacity of riparian buffers to intercept and assimilate nutrients and other water contaminants. Research expanded globally in the 1990s, with themes including (4) plant life history requirements and (5) reliance on fluvial geomorphic dynamics that enable riparian rejuvenation. Resource managers recognized that riparian areas provide (6) rich wildlife habitats (7) along with valued ecosystem services, (8) which encouraged conservation and restoration initiatives, (9) including environmental flow regimes. Floodplains are (10) vulnerable to invasive plants and management has included biocontrol such as for Tamarix in the American Southwest. Into the twenty-first century, (11) climate change is advancing, and riparian ecosystems may be especially impacted due to the compound challenges from increasing water demand and declining summer flows. As an emerging opportunity, (12) while reservoirs submerge floodplain vegetation, reservoir deltas may support compensatory riparian wetlands. (13) Studies increasingly utilize remote sensing tools including satellite imagery, LiDAR and unmanned aircraft systems, and (14) the coordination of large data sets invites digital ecology, including artificial intelligence and machine learning. Since riparian zones are centres for human activities, (15) there are opportunities for citizen science, social media and internet applications, which will increasingly democratize riparian research and management.

Wetlands↗
USGS2019

Records of engagement and decision making for environmental and socio-ecological challenges

We propose creating and maintaining records of engagement and decision-making (RoED) to help us and our communities better understand ourselves, our goals, our decisions, and the dynamic systems in which we all live. The purpose of RoED is to go well beyond noting that dialogue occurred or a decision was reached. The records should, in ways appropriate to the context and participants, document interactions and note biases, beliefs, emotions, behaviors, norms, and values. These crucial aspects are generally absent in academic papers and formal reports, yet they always play a role in decision-making processes. While not a panacea for addressing critical biophysical and social challenges, we propose that a comprehensive framework for promoting realistic, legitimate and inclusive engagement could enhance trust, establish institutional memory, and when and where appropriate, ensure greater transparency. The aim is to create and maintain RoED to collect significant information and share insights from multi-stakeholder decision-making processes from diverse institutions, contexts, and disciplinary domains. In the long-term RoED could promote more effective adaptive management or governance approaches. This paper describes an exploratory phase intended to catalyze collaborative efforts worldwide.

EURO Journal on Decision Processes↗
USGS1973

Mariner 9-Image processing and products

The purpose of this paper is to describe the system for the display, processing, and production of image-data products created to support the Mariner 9 Television Experiment. Of necessity, the system was large in order to respond to the needs of a large team of scientists with a broad scope of experimental objectives. The desire to generate processed data products as rapidly as possible to take advantage of adaptive planning during the mission, coupled with the complexities introduced by the nature of the vidicon camera, greatly increased the scale of the ground-image processing effort. This paper describes the systems that carried out the processes and delivered the products necessary for real-time and near-real-time analyses. References are made to the computer algorithms used for the, different levels of decalibration and analysis.

Icarus↗
USGS1986

Groundwater model of the Blue River basin, Nebraska-Twenty years later

Groundwater flow models have become almost a routine tool of the practicing hydrologist. Yet, surprisingly little attention has been given to true verification analysis of studies using these models. This paper examines predictions for 1982 of water-level declines and streamflow depletions that were made in 1965 using an electric analog groundwater model of the Blue River basin in southeastern Nebraska. Analysis of the model's predictions suggests that the analog model used too low an estimate of net groundwater withdrawals, yet overestimated water-level declines. The model predicted that almost all of the net groundwater pumpage would come from storage in the Pleistocene aquifer within the Blue River basin. It appears likely that the model underestimated the contributions of other sources of water to the pumpage, and that the aquifer storage coefficients used in the model were too low. There is some evidence that groundwater pumpage has had a greater than predicted effect on streamflow. Considerable uncertainty about the basic conceptualization of the hydrology of the Blue River basin greatly limits the reliability of groundwater models developed for the basin. The paper concludes with general perspectives on groundwater modeling gained from this post-audit analysis.

Nebraska↗
USGS1995

Recent data and information system initiatives for remotely sensed measurements of the land surface

As part of the International Satellite Land Satellite Climatology Program (ISLSCP) Workshop on Remote Sensing of the Land Surface for Studies of Global Change, five invited presentations were given on recent data initiatives relevant to the ISLSCP community. The presentations are summarized in this paper along with some observations by the authors on data systems for the land sciences community. The invited presentations are by no means all inclusive but were selected as examples of current data activities, representing a range of topics associated with data for land sciences including: the generation of global and local scale data sets, the reworking of historical data sets, new data initiatives and some programmatic aspects of land data base development. This paper serves to provide information on these data initiatives and to air some of the issues concerning land science data systems that were raised at the meeting.

Remote Sensing of Environment↗
USGS1985

Rock mechanics observations pertinent to the rheology of the continental lithosphere and the localization of strain along shear zones

Emphasized in this paper are the deformation processes and rheologies of rocks at high temperatures and high effective pressures, conditions that are presumably appropriate to the lower crust and upper mantle in continental collision zones. Much recent progress has been made in understanding the flexure of the oceanic lithosphere using rock-mechanics-based yield criteria for the inelastic deformations at the top and base. At mid-plate depths, stresses are likely to be supported elastically because bending strains and elastic stresses are low. The collisional tectonic regime, however, is far more complex because very large permanent strains are sustained at mid-plate depths and this requires us to include the broad transition between brittle and ductile flow. Moreover, important changes in the ductile flow mechanisms occur at the intermediate temperatures found at mid-plate depths. Two specific contributions of laboratory rock rheology research are considered in this paper. First, the high-temperature steady-state flow mechanisms and rheology of mafic and ultramafic rocks are reviewed with special emphasis on olivine and crystalline rocks. Rock strength decreases very markedly with increases in temperature and it is the onset of flow by high temperature ductile mechanisms that defines the base of the lithosphere. The thickness of the continental lithosphere can therefore be defined by the depth to a particular isotherm Tc above which (at geologic strain rates) the high-temperature ductile strength falls below some arbitrary strength isobar (e.g., 100 MPa). For olivine Tc is about 700??-800??C but for other crustal silicates, Tc may be as low as 400??-600??C, suggesting that substantial decoupling may take place within thick continental crust and that strength may increase with depth at the Moho, as suggested by a number of workers on independent grounds. Put another way, the Moho is a rheological discontinuity. A second class of laboratory observations pertains to the general phenomenon of ductile faulting in which ductile strains are localized into shear zones. Ductile faults have been produced in experiments of five different rock types and is generally expressed as strain softening in constant-strain-rate tests or as an accelerating-creep-rate stage at constant differential stress. A number of physical mechanisms have been identified that may be responsible for ductile faulting, including the onset of dynamic recrystallization, phase changes, hydrothermal alteration and hydrolytic weakening. Microscopic evidence for these processes as well as larger-scale geological and geophysical observations suggest that ductile faulting in the middle to lower crust and upper mantle may greatly influence the distribution and magnitudes of differential stresses and the style of deformation in the overlying upper continental lithosphere.

Tectonophysics↗
USGS1984

Losses from effluent taxes and quotas under uncertainty

Recent theoretical papers by Adar and Griffin ( J. Environ. Econ. Manag. 3 , 178–188 (1976)), Fishelson ( J. Environ. Econ. Manag. 3 , 189–197 (1976)), and Weitzman ( Rev. Econ. Studies 41 , 477–491 (1974)) show that, different expected social losses arise from using effluent taxes and quotas as alternative control instruments when marginal control costs are uncertain. Key assumptions in these analyses are linear marginal cost and benefit functions and an additive error for the marginal cost function (to reflect uncertainty). In this paper, empirically derived nonlinear functions and more realistic multiplicative error terms are used to estimate expected control and damage costs and to identify (empirically) the mix of control instruments that minimizes expected losses.

Journal of Environmental Economics and Management↗
USGS1988

Statistical relationship between pyrite grain size distribution and pyritic sulfur reduction in Ohio coal

This paper presents a statistical relationship between the pyrite particle size distribution and the potential amount of pyritic sulfur reduction achieved by specific-gravity-based separation. This relationship is obtained from data on 26 Ohio coal samples crushed to 14 × 28 mesh. In this paper a prediction equation is developed that considers the complete statistical distribution of all the pyrite particle sizes in the coal sample. Assuming that pyrite particles occurring in coal have a lognormal distribution, the information about the particle size distribution can be encapsulated in terms of two parameters only, the mean and the standard deviation of the logarithms of the grain diameters. When the pyritic sulfur reductions of the 26 coal samples are related to these two parameters, a very satisfactory regression equation ( R 2 = 0.91) results. This equation shows that information on both these parameters is needed for an accurate prediction of potential sulfur reduction, and that the mean and the standard deviation interact negatively insofar as their influence on pyritic sulfur reduction is concerned.

International Journal of Coal Geology↗
USGS1990

Collection and analysis of colloidal particles transported in the Mississippi River, U.S.A.

Sediment transport has long been recognized as an important mechanism for the transport of contaminants in surface waters. Suspended sediment has traditionally been divided into three size classes: sand-sized (>63 ??m), silt-sized (<63 ??m but settleable) and clay-sized (non-settleable). The first two classes are easily collected and characterized using screens (sand) and settling (silt). The clay-sized particles, more properly called colloids, are more difficult to collect and characterize, and until recently received little attention. From the hydrologic perspective, a colloid is a particle, droplet, or gas bubble with at least one dimension between 0.001 and 1 ??m. Because of their small size, colloids have large specific surface areas and high surface free energies which may facilitate sorption of hydrophobic materials. Understanding what types of colloids are present in a system, how contaminants of interest interact with these colloids, and what parameters control the transport of colloids in natural systems is critical if the relative importance of colloid-mediated transport is to be understood. This paper describes the collection, concentration and characterization of colloidal materials in the Mississippi River. Colloid concentrations, particle-size distributions, mineral composition and electrophoretic mobilities were determined. Techniques used are illustrated with samples collected at St. Louis, Missouri, U.S.A.Sediment transport has long been recognized as an important mechanism for the transport of contaminants in surface waters. Suspended sediment has traditionally been divided into three size classes: sand-sized (> 63 ??m), silt-sized (< 63 ??m but settleable) and clay-sized (non-settleable). The first two classes are easily collected and characterized using screens (sand) and settling (silt). The clay-sized particles, more properly called colloids, are more difficult to collect and characterize, and until recently received little attention. From the hydrologic perspective, a colloid is a particle, droplet, or gas bubble with at least one dimension between 0.001 and 1 ??m. Because of their small size, colloids have large specific surface areas and high surface free energies which may facilitate sorption of hydrophobic materials. Understanding what types of colloids are present in a system, how contaminants of interest interact with these colloids, and what parameters control the transport of colloids in natural systems is critical if the relative importance of colloid-mediated transport is to be understood. This paper describes the collection, concentration and characterization of colloidal materials in the Mississippi River. Colloid concentrations, particle-size distributions, mineral composition and electrophoretic mobilities were determined. Techniques used are illustrated with samples collected at St. Louis, Missouri, U.S.A.

Journal of Contaminant Hydrology↗