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At least 883 records · Page 49Linked to original sources
USGS2022

Waters divided: A history of alluvial fan research and a view of its future

Flows exiting confined valleys tend to deposit sediment in fan-shaped landforms. Where deposition is wholly or largely by the tractive forces of flowing water, these landforms are called alluvial fans. They are the product of the progressive division of water and sediment downfan, from slopes that may exceed 0.10 to distal slopes that may be below 0.01. Channel depths also tend to decline, from values that approach one to several meters at steep fanheads, to a few decimeters at distal fan margins. The result is a radiating, depositional ramp where confined or unconfined flows transport sediment from source basins to bounding streams, subsiding basins, or stable platforms. Where streams or subsiding basins consume the sediment supply from the source basin, the fan may approach a steady form whose extent and distal slope are set by stream location or subsidence rate. Where boundary conditions do not remove sediment, the fan may prograde out to long distances and low slopes (<0.01). Theoretical and experimental work over the past several decades support the notion that alluvial fan long-profiles become steeper as sediment supply increases or transport capacity decreases, and increasingly concave upward as the rate of bed material deposition decreases downfan. Grainsize distributions of alluvial fans seem to span the range observed in alluvial rivers, with no processes that uniquely identify them, apart from the distributary pattern of deposition. Bed sand cover tends to increase downfan in arid-region fans, with an absence of systematic downfan fining of coarser grain sizes. Surficial mapping and geochronology have demonstrated that fan deposition varies greatly through time, arguably from climate variations that alter hillslope sediment supply. The combination of surficial mapping and hydraulic modeling with high-resolution topography can now produce detailed flood susceptibility maps. The effective use of these maps to protect lives and property, however, depends on answering many of the enduring questions about the mechanics of how water and sediment divide down alluvial fans.

Book chapter↗
USGS2019

Research Note: How old are the people who die in avalanches? A look into the ages of avalanche victims in the United States (1950-2018)

Since the winter of 1950-1951, 1084 individuals perished in snow avalanches in the United States. In this study, we analyze the ages of those killed (n=900) by applying non-parametric methods to annual median ages and for age groups and primary activity groups. Change point detection results suggest a significant change in 1990 in the median age of avalanche fatalities. Significant positive trends exist for both the 1950 to 2018 and 1990 to 2018 median age of victims. The median age of victims from 1950 to 1989 is 27 and 33 from 1990 to 2018. Since 1990, the 30-39 and 40-49 age groups are the only age category to exhibit a positive trend in the number of fatalities. There is no significant difference in median ages between snowmobilers and other categories. These results can be used to enhance avalanche education and forecasting efforts in the United States.

Journal of Outdoor Recreation and Tourism↗
USGS2018

Research note: Mapping spatial patterns in sewer age, material, and proximity to surface waterways to infer sewer leakage hotspots

Identifying areas where deteriorating sewer infrastructure is in close proximity to surface waterways is needed to map likely connections between sewers and streams. We present a method to estimate sewer installation year and deterioration status using historical maps of the sewer network, parcel-scale property assessment data, and pipe material. Areas where streams were likely buried into the sewer system were mapped by intersecting the historical stream network derived from a 10-m resolution digital elevation model with sewer pipe locations. Potential sewer leakage hotspots were mapped by identifying where aging sewer pipes are in close proximity (50-m) to surface waterways. Results from Pittsburgh, Pennsylvania (USA), indicated 41% of the historical stream length was lost or buried and the potential interface between sewers and streams is great. The co-location of aging sewer infrastructure (>75 years old) near stream channels suggests that 42% of existing streams are located in areas with a high potential for sewer leakage if sewer infrastructure fails. Mapping the sewer-stream interface provides an approach to better understand areas were failing sewers may contribute a disproportional amount of nutrients and other pathogens to surface waterways.

Pennsylvania↗
USGS2014

Landsat-8: Science and product vision for terrestrial global change research

Landsat 8, a NASA and USGS collaboration, acquires global moderate-resolution measurements of the Earth's terrestrial and polar regions in the visible, near-infrared, short wave, and thermal infrared. Landsat 8 extends the remarkable 40 year Landsat record and has enhanced capabilities including new spectral bands in the blue and cirrus cloud-detection portion of the spectrum, two thermal bands, improved sensor signal-to-noise performance and associated improvements in radiometric resolution, and an improved duty cycle that allows collection of a significantly greater number of images per day. This paper introduces the current (2012–2017) Landsat Science Team's efforts to establish an initial understanding of Landsat 8 capabilities and the steps ahead in support of priorities identified by the team. Preliminary evaluation of Landsat 8 capabilities and identification of new science and applications opportunities are described with respect to calibration and radiometric characterization; surface reflectance; surface albedo; surface temperature, evapotranspiration and drought; agriculture; land cover, condition, disturbance and change; fresh and coastal water; and snow and ice. Insights into the development of derived ‘higher-level’ Landsat products are provided in recognition of the growing need for consistently processed, moderate spatial resolution, large area, long-term terrestrial data records for resource management and for climate and global change studies. The paper concludes with future prospects, emphasizing the opportunities for land imaging constellations by combining Landsat data with data collected from other international sensing systems, and consideration of successor Landsat mission requirements.

Remote Sensing of Environment↗
USGS2008

Landsat still contributing to environmental research

Landsat data have enabled continuous global monitoring of both human-caused and other land cover disturbances since 1972. Recently degraded performance and intermittent service of the Landsat 7 and Landsat 5 sensors, respectively, have raised concerns about the condition of global Earth observation programs. However, Landsat imagery is still useful for landscape change detection and this capability should continue into the foreseeable future.

Trends in Ecology and Evolution↗
USGS2002

Limitations in the use of commercial humic acids in water and soil research

Seven samples of commercial "humic acids", purchased from five different suppliers, were studied, and their characteristics were compared with humic and fulvic acids isolated from streams, soils, peat, leonardite, and a dopplerite sample. Cross-polarization and magic-angle spinning 13C NMR spectroscopy clearly shows pronounced differences between the commercial materials and all other samples. Elemental and infrared spectroscopic data do not show such clear-cut differences but can be used as supportive evidence, with the 13C NMR data, to substantiate the above distinctions. As a result of these differences and due to the general lack of information relating to the source, method of isolation, or other pretreatment of the commercial materials, these commercial products are not considered to be appropriate for use as analogues of true soil and water humic substances, in experiments designed to evaluate the nature and reactivity of humic substances in natural waters and soils.

Environmental Science & Technology↗
USGS2006

Researchers consider U.S. Southwest's response to warmer, drier conditions

In 2000, the popular press frequently referred to reports that the southwestern United States might experience a shift from relatively wet to dry conditions during the next couple of decades (see http://topex‐www.jpl.nasa.gov/discover/PDO.html). These predictions stemmed from observations that the Pacific Decadal Oscillation (PDO) appeared to abruptly change from a “positive” to a “negative” phase in 1999 (Figure 1). During the mid‐twentieth century, a similar negative phase of the PDO was accompanied by prolonged dry conditions in the southwest. By extrapolation, some climatologists predicted future drought in the southwest. Such a change would heavily affect land use planning in the region, because national demographics have stressed the region's resources over the past century From 1990 to 2000, for instance, the population of Nevada and Arizona increased by almost 2.3 million people (http://www.census.gov/population/www/cen2000/respop.html). To discuss potential scenarios of landscape and ecosystem response to 25 years of hot and dry climate, scientists from diverse disciplines gathered at the University of Arizona in April 2001. The objectives of this workshop were to address evidence supporting predictions of warmer and drier climate and the possible landscape responses (http://geology.wr.usgs.gov/sw‐workshop/).

Eos, Transactions, American Geophysical Union↗
USGS2011

Progress in global lake drilling holds potential for global change research

During the past decade, numerous international investigations of past global change have focused on particular time intervals, or “Time Streams,” suggested by the Past Global Changes (PAGES) Project of the International Geosphere‐Biosphere Programme (IGBP). Time Stream 1 encompasses the last 2000 years, and Time Stream 2 encompasses at least the last 250,000 years. Geographically many of these studies have been grouped into north‐south transects of continental global change records known as the Pole‐Equator‐Pole (PEP) transects [ Bradley et al. , 1995]. These continental transects have been complemented by the study of marine records included in the International Marine Global Change Study (IMAGES) transects and high‐latitude ice core records such as those from the U.S. Greenland Ice Sheet Project 2 (GISP2) and the European Greenland Ice‐core Project (GRIP).

Idaho, Utah↗
USGS2011

Aeromagnetic survey over U.S. to advance geomagnetic research

A proposed high‐altitude survey of the United States offers an exciting and cost effective opportunity to collect magnetic‐anomaly data. Lockheed Martin Missile and Space Company is considering funding a reimbursable ER‐2 aircraft (Figure 1) mission to collect synthetic aperture radar (SAR) imagery at an altitude of about 21 km over the conterminous United States and Alaska. The collection of total and vector magnetic field data would be a secondary objective of the flight. Through this “piggyback approach,” the geomagnetic community would inherit invaluable magnetic data at a nominal cost. These data would provide insight on fundamental tectonic and thermal processes and give a new view of the structural and lithologic framework of the crust and upper mantle.

Eos, Transactions, American Geophysical Union↗
USGS2014

Appendix C—Report on research in the field of ground water being conducted by oil companies

In view of the shortness of time since the appointment of the writer to the Committee on Ground Water this report is confined to the technology and problems in the Gulf Coast Oil Province. Of course, many of the methods and practices would apply to most parts of the country however, some would differ materially from one region to another. The writer wishes to acknowledge the suggestions and comments by F. H. LAHEE and PAUL WEAVER. Having been stationed in Houston, Texas, in the heart of the Gulf Coast Area for four and a half years, the writer has had an opportunity to view the great similarity of the problems confronting the petroleum geologist and engineer and the ground‐water hydrologist. Both groups deal with the accumulation, movement, and withdrawal of fluid from underground strata, yet each group is content to study its own literature and use its own terminology without much concern for the other. The petroleum and ground‐water engineer, independently of one another, have developed mathematical formulas for the determination of permeability from field‐data. These formulas use the same basic principles of physics and the initial papers on the subject by both groups were published within two years of one another. Because of the similarity in the technology and problems of the petroleum engineer and the ground‐water hydrologist there is a definite need for closer cooperation. Some of the problems are so closely related that their solution rests in cooperative studies.

Eos, Transactions, American Geophysical Union↗
USGS2014

Report of the Research Committee on Runoff, 1945–46

The variety of usage and even the confusion in the nomenclature and terminology of some fields of hydrology have been often remarked. The Committee on Runoff conceived the idea that it would be profitable to consider some of the terms which are especially pertinent to the field of runoff. That consideration was the principal Committee project of the past year and is featured in this report. The Chairman sent a letter to the members of the Committee that was planned to draw out a symposium of opinions on the subject. A good starting point seemed to be the classification of water on the Earth. Meinzer's well‐known classification was given: atmospheric water, surface water, and subsurface or subterranean water. Comments were solicited.

Eos, Transactions, American Geophysical Union↗
USGS2014

Report of Research Committee on Runoff, 1946–1947

The membership of the Committee has remained unchanged during the year. There has been some discussion of committee activities between individual members and in small groups. The further discussion of runoff terminology has resulted in no new developments of special note. The following statements have been received from members of the committee concerning activities of the agencies with which they are associated.

Eos, Transactions, American Geophysical Union↗