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USGS2008

Great Basin paleontological database

The U.S. Geological Survey has constructed a paleontological database for the Great Basin physiographic province that can be served over the World Wide Web for data entry, queries, displays, and retrievals. It is similar to the web-database solution that we constructed for Alaskan paleontological data (www.alaskafossil.org). The first phase of this effort was to compile a paleontological bibliography for Nevada and portions of adjacent states in the Great Basin that has recently been completed. In addition, we are also compiling paleontological reports (Known as E&R reports) of the U.S. Geological Survey, which are another extensive source of l,egacy data for this region. Initial population of the database benefited from a recently published conodont data set and is otherwise focused on Devonian and Mississippian localities because strata of this age host important sedimentary exhalative (sedex) Au, Zn, and barite resources and enormons Carlin-type An deposits. In addition, these strata are the most important petroleum source rocks in the region, and record the transition from extension to contraction associated with the Antler orogeny, the Alamo meteorite impact, and biotic crises associated with global oceanic anoxic events. The finished product will provide an invaluable tool for future geologic mapping, paleontological research, and mineral resource investigations in the Great Basin, making paleontological data acquired over nearly the past 150 yr readily available over the World Wide Web. A description of the structure of the database and the web interface developed for this effort are provided herein. This database is being used ws a model for a National Paleontological Database (which we am currently developing for the U.S. Geological Survey) as well as for other paleontological databases now being developed in other parts of the globe. ?? 2008 Geological Society of America.

Geosphere↗

USGS1994

National Water Quality Laboratory Profile

The National Water Quality Laboratory determines organic and inorganic constituents in samples of surface and ground water, river and lake sediment, aquatic plant and animal material, and precipitation collected throughout the United States and its territories by the U.S. Geological Survey. In water year 1994, the Laboratory produced more than 900,000 analytical results for about 65,000 samples. The Laboratory also coordinates an extensive network of contract laboratories for the determination of radiochemical and stable isotopes and work for the U.S. Department of Defense Environmental Contamination Hydrology Program. Heightened concerns about water quality and about the possible effects of toxic chemicals at trace and ultratrace levels have contributed to an increased demand for impartial, objective, and independent data.

Open-File Report↗

USGS2021

Long-term population fluctuations of a Burrowing Owl population on Kirtland Air Force Base, New Mexico, USA

Western Burrowing Owls ( Athene cunicularia hypugaea ; hereafter, Burrowing Owls) were once widespread residents of grasslands throughout western North America, but their range has contracted, and abundance has declined in some regions. The causes of declines and geographic variation in population trends of Burrowing Owls are unclear but may be linked to changing land use and urbanization. Burrowing Owls are often found in association with airfields and airports, and their presence at such facilities is sometimes considered to be in conflict with those operations. Documenting the long-term persistence of Burrowing Owls at active airfields can help airfield managers who face decisions regarding compatibility of owls and airfield operations. We report the results of a long-term effort to monitor Burrowing Owls on Kirtland Air Force Base in New Mexico, USA, including the rapid recovery of Burrowing Owl numbers from near-extirpation and the relationships between abundance and other demographic traits. The number of breeding pairs of Burrowing Owls increased from one pair in 2013 to 28 pairs in 2019 and 2020, and the number of fledglings produced increased from one in 2013 to 84 in 2019 and 61 in 2020. The recovery was not uniform across all areas of Kirtland Air Force Base, and some formerly occupied areas remained unoccupied. We documented dispersal outside the Air Force base boundary and that the number of breeding pairs was more strongly influenced by the number of offspring produced in the prior year than the number of owls returning from prior years, which indicated that the population is part of a larger meta-population. Our results demonstrate that the maintenance of Burrowing Owl populations is not necessarily at odds with safe airfield operations, that Burrowing Owls exhibit complex population dynamics, and can rapidly recolonize previously occupied areas if habitat and nest sites remain suitable.

New Mexico↗

USGS1981

Improved methods for national water assessment, water resources contract: WR15249270

The purpose of our research is to develop methods to make National Water Assessment more useful in estimating water availability for economic growth and more helpful in determining the effect of water resource development upon the environmental quality of related land resources. There are serious questions pertaining to the 1975 Water Assessment and these amplify the significance of decisions made as to the planning and scheduling of the next assessment.

Report↗

USGS1996

Level II scour analysis for Bridge 37 (BARTTH00080037) on Town Highway 8, crossing Willoughby River, Barton, Vermont

This report provides the results of a detailed Level II analysis of scour potential at structure BARTTH00080037 on town highway 8 crossing the Willoughby River, Barton, Vermont (figures 1–8). A Level II study is a basic engineering analysis of the site, including a quantitative analysis of stream stability and scour (U.S. Department of Transportation, 1993). Results of a Level I scour investigation also are included in Appendix E of this report. A Level I investigation provides a qualitative geomorphic characterization of the study site. Information on the bridge, gleaned from Vermont Agency of Transportation (VTAOT) files, was compiled prior to conducting Level I and Level II analyses and is found in Appendix D. The site is in the New England Upland section of the New England physiographic province of north-central Vermont in the town of Barton. The 60.4-mi 2 drainage area is in a predominantly rural and forested basin. In the vicinity of the study site, the banks have sparse to moderate woody vegetation coverage. In the study area, the Willoughby River is probably incised, has a sinuous channel with a slope of approximately 0.009 ft/ft, an average channel top width of 108 ft and an average channel depth of 6 ft. The predominant channel bed material is cobble (D 50 is 95.1 mm or 0.312 ft). The geomorphic assessment at the time of the Level I and Level II site visit on October 20, 1994, indicated that the reach was stable. The town highway 8 crossing of the Willoughby River is a 96-ft-long, two-lane bridge consisting of one 94-foot steel-beam span (Vermont Agency of Transportation, written communication, August 4, 1994). The bridge is supported by vertical, concrete abutments with wingwalls. The channel is skewed approximately 15 degrees to the opening while the opening-skew-to-roadway is 10 degrees. No scour was reported in the channel or along abutments or wingwalls during the Level I assessment. Type-2 stone fill (less than 24 inches diameter) was reported at each abutment and all four wingwalls. Additional details describing conditions at the site are included in the Level II Summary and Appendices D and E. Scour depths and rock rip-rap sizes were computed using the general guidelines described in Hydraulic Engineering Circular 18 (Richardson and others, 1993). Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. Data in appendix D (Vermont Agency of Transportation, written communication, August 4, 1994) indicate that the right abutment may be founded on or near marble bedrock which may limit scour depths. Bedrock was not detected by borings in the vicinity of the left abutment. The scour analysis results are presented in tables 1 and 2 and a graph of the scour depths is presented in figure 8. Contraction scour for all modelled flows was 0 ft. Abutment scour ranged from 7.3 to 10.7 ft and the worst-case abutment scour occurred at the 500-year discharge. Additional information on scour depths and depths to armoring are included in the section titled “Scour Results”. Scoured-streambed elevations, based on the calculated scour depths, are presented in tables 1 and 2. A cross-section of the scour computed at the bridge is presented in figure 8. Scour depths were calculated assuming an infinite depth of erosive material and a homogeneous particle-size distribution. It is generally accepted that the Froehlich equation (abutment scour) gives “excessively conservative estimates of scour depths” (Richardson and others, 1993, p. 47). Usually, computed scour depths are evaluated in combination with other information including (but not limited to) historical performance during flood events, the geomorphic stability assessment, existing scour protection measures, and the results of the hydraulic analyses. Therefore, scour depths adopted by VTAOT may differ from the computed values documented herein.

Vermont↗

USGS2012

Preliminary geologic map of the Big Costilla Peak area, Taos County, New Mexico, and Costilla County, Colorado

This map covers the Big Costilla Peak, New Mex.‒Colo. quadrangle and adjacent parts of three other 7.5 minute quadrangles: Amalia, New Mex.‒Colo., Latir Peak, New Mex., and Comanche Point, New Mex. The study area is in the southwesternmost part of that segment of the Sangre de Cristo Mountains known as the Culebra Range; the Taos Range segment lies to the southwest of Costilla Creek and its tributary, Comanche Creek. The map area extends over all but the northernmost part of the Big Costilla horst, a late Cenozoic uplift of Proterozoic (1.7-Ga and less than 1.4-Ga) rocks that is largely surrounded by down-faulted middle to late Cenozoic (about 40 Ma to about 1 Ma) rocks exposed at significantly lower elevations. This horst is bounded on the northwest side by the San Pedro horst and Culebra graben, on the northeast and east sides by the Devils Park graben, and on the southwest side by the (about 30 Ma to about 25 Ma) Latir volcanic field. The area of this volcanic field, at the north end of the Taos Range, has undergone significantly greater extension than the area to the north of Costilla Creek. The horsts and grabens discussed above are all peripheral structures on the eastern flank of the San Luis basin, which is the axial part of the (about 26 Ma to present) Rio Grande rift at the latitude of the map. The Raton Basin lies to the east of the Culebra segment of the Sangre de Cristo Mountains. This foreland basin formed during, and is related to, the original uplift of the Sangre de Cristo Mountains which was driven by tectonic contraction of the Laramide (about 70 Ma to about 40 Ma) orogeny. Renewed uplift and structural modification of these mountains has occurred during formation of the Rio Grande rift. Surficial deposits in the study area include alluvial, mass-movement, and glacial deposits of middle Pleistocene to Holocene age.

New Mexico↗

USGS2001

General field and office procedures for indirect discharge measurements

The discharge of streams is usually measured by the current-meter method. During flood periods, however, it is frequently impossible or impractical to measure the discharges by this method when they occur. Consequently, many peak discharges must be determined after the passage of the flood by indirect methods, such as slope-area, contracted-opening, flow-over-dam, and flow-through-culvert, rather than by direct current-meter measurement. Indirect methods of determining peak discharge are based on hydraulic equations which relate the discharge to the water-surface profile and the geometry of the channel. A field survey is made after the flood to determine the location and elevation of high-water marks and the characteristics of the channel. Detailed descriptions of the general procedures used in collecting the field data and in computing the discharge are given in this report. Each of the methods requires special procedures described in subsequent chapters.

Techniques of Water-Resources Investigations↗

USGS1974

Progress report on the North American Breeding Bird Survey

The Breeding Bird Survey has been monitoring bird population changes in the U.S.A. and Canada since 1966. Each cooperator makes 50 3-minute stops at 0.8-km intervals along randomly selected roadside routes in 4 to 4 1/2 hours on one morning in June of each year. Data from the 1500 to 1600 routes are entered on magnetic tape, edited for accuracy, and then used for statistical analysis of population change at four geographic levels: physiographic region; state or province; region (eastern, central and western); and the continent. Examples of use of the data are: (1) detection of year-to-year changes in continental or rcgional populations; (2) use of population indices to show long-term population changes; (3) range expansion and contraction at the state level, including some of the reasons for those changes and documenting the associated population shifts within the original range; (4) mapping distribution and relative abundance on either a state, regional or continental scale; (5) mapping changes in abundance; and(6) comparing breeding with winter distribution. Future potential uses will include estimates of total continental populations and indices of environmental quality.

Acta Ornithologica↗

USGS2018

Evaluation of sockeye salmon after passage through an innovative upstream fish-passage system at Cle Elum Dam, Washington, 2017

Executive Summary The Bureau of Reclamation (Reclamation) and the Washington State Department of Ecology (Ecology), working with the Yakima River Basin Water Enhancement Project Workgroup (composed of representatives of the Yakama Nation; Federal, State, county, and city governments; environmental organizations; and irrigation districts), developed the Yakima Basin Integrated Plan (Integrated Plan). The Integrated Plan identifies a comprehensive approach to water resources and ecosystem restoration improvements in the Yakima Basin to be implemented over a 30-year period. The Integrated Plan includes seven elements: Reservoir fish passage, Structural and operational changes to existing facilities, Surface water storage, Groundwater storage, Habitat/watershed protection and enhancement, Enhanced water conservation, and Market reallocation. The first listed element, reservoir fish passage, will be expensive and take many years to accomplish. Reclamation and Ecology decided to look at new and innovative means to provide passage that could help reduce project cost and construction timing while maintaining survival rates of traditional upstream passage facilities. Reclamation contracted with the U.S. Geological Survey to do a study to evaluate the outcome of passage through one innovative fish-passage system at Cle Elum Dam, the first Integrated Plan reservoir fish-passage project being implemented.

Washington↗

USGS2012

High-resolution digital elevation dataset for Crater Lake National Park and vicinity, Oregon, based on LiDAR survey of August-September 2010 and bathymetric survey of July 2000

Crater Lake partially fills the caldera that formed approximately 7,700 years ago during the eruption of a 12,000-foot volcano known as Mount Mazama. The caldera-forming or climactic eruption of Mount Mazama devastated the surrounding landscape, left a thick deposit of pumice and ash in adjacent valleys, and spread a blanket of volcanic ash as far away as southern Canada. Because the Crater Lake region is potentially volcanically active, knowledge of past events is important to understanding hazards from future eruptions. Similarly, because the area is seismically active, documenting and evaluating geologic faults is critical to assessing hazards from earthquakes. As part of the American Recovery and Reinvestment Act (ARRA) of 2009, the U.S. Geological Survey was awarded funding for high-precision airborne LiDAR ( Li ght D etection A nd R anging) data collection at several volcanoes in the Cascade Range through the Oregon LiDAR Consortium, administered by the Oregon Department of Geology and Mineral Industries (DOGAMI). The Oregon LiDAR Consortium contracted with Watershed Sciences, Inc., to conduct the data collection surveys. Collaborating agencies participating with the Oregon LiDAR Consortium for data collection in the Crater Lake region include Crater Lake National Park (National Park Service) and the Federal Highway Administration. In the immediate vicinity of Crater Lake National Park, 798 square kilometers of LiDAR data were collected, providing a digital elevation dataset of the ground surface beneath forest cover with an average resolution of 1.6 laser returns/m 2 and both vertical and horizontal accuracies of ±5 cm. The LiDAR data were mosaicked in this report with bathymetry of the lake floor of Crater Lake, collected in 2000 using high-resolution multibeam sonar in a collaborative effort between the U.S. Geological Survey, Crater Lake National Park, and the Center for Coastal and Ocean Mapping at the University of New Hampshire. The bathymetric survey collected 16 million soundings with a spatial resolution of 2 meters using an EM1002 system owned and operated by C&C Technologies, Inc. The combined LiDAR and bathymetric dataset has a cell size of 1 meter and will contribute to understanding past volcanic events and their deposits, recognizing of faults and volcanic landforms, and quantifying landscape modification during and after the next volcanic eruption at Crater Lake.

Oregon↗

USGS2017

Overview of a comprehensive resource database for the assessment of recoverable hydrocarbons produced by carbon dioxide enhanced oil recovery

A database called the “Comprehensive Resource Database” (CRD) was prepared to support U.S. Geological Survey (USGS) assessments of technically recoverable hydrocarbons that might result from the injection of miscible or immiscible carbon dioxide (CO 2 ) for enhanced oil recovery (EOR). The CRD was designed by INTEK Inc., a consulting company under contract to the USGS. The CRD contains data on the location, key petrophysical properties, production, and well counts (number of wells) for the major oil and gas reservoirs in onshore areas and State waters of the conterminous United States and Alaska. The CRD includes proprietary data on petrophysical properties of fields and reservoirs from the “Significant Oil and Gas Fields of the United States Database,” prepared by Nehring Associates in 2012, and proprietary production and drilling data from the “Petroleum Information Data Model Relational U.S. Well Data,” prepared by IHS Inc. in 2012. This report describes the CRD and the computer algorithms used to (1) estimate missing reservoir property values in the Nehring Associates (2012) database, and to (2) generate values of additional properties used to characterize reservoirs suitable for miscible or immiscible CO 2 flooding for EOR. Because of the proprietary nature of the data and contractual obligations, the CRD and actual data from Nehring Associates (2012) and IHS Inc. (2012) cannot be presented in this report.

Techniques and Methods↗

USGS2013

Potential effects of climate change on inland glacial lakes and implications for lake-dependent biota in Wisconsin: final report April 2013

The economic vitality and quality of life of many northern Wisconsin communities is closely associated with the ecological condition of the abundant water resources in the region. Climate change models predict warmer temperatures, changes to precipitation patterns, and increased evapotranspiration in the Great Lakes region. Recently (1950-2006), many regions of Wisconsin have experienced warming, and precipitation has generally increased except in far northern Wisconsin. Modeling conducted by the University of Wisconsin Nelson Environmental Institute Center for Climate Research predicts an increase in annual temperature by the middle of the 21st century of approximately 6° F statewide, and an increase in precipitation of 1”–2”. However, summer precipitation in the northern part of the state is expected to be less and winter precipitation will be greater. By the end of the 21st century, the magnitude of changes in temperature and precipitation are expected to intensify. Such climatic changes have altered, and would further alter hydrological, chemical, and physical properties of inland lakes. Lake-dependent wildlife sensitive to changes in water quality, are particularly susceptible to lake quality-associated habitat changes and are likely to suffer restrictions to current breeding distributions under some climate change scenarios. We have selected the common loon (Gavia immer) to serve as a sentinel lake-dependent piscivorous species to be used in the development of a template for linking primary lake-dependent biota endpoints (e.g., decline in productivity and/or breeding range contraction) to important lake quality indicators. In the current project, we evaluate how changes in freshwater habitat quality (specifically lake clarity) may impact common loon lake occupancy in Wisconsin under detailed climate-change scenarios. In addition, we employ simple land-use/land cover and habitat scenarios to illustrate the potential interaction of climate and land-use/land cover effects. The methods employed here provide a template for studies where integration of physical and biotic models is used to project future conditions under various climate and land use change scenarios. Findings presented here project the future conditions of lakes and loons within an important watershed in northern Wisconsin – of importance to water resource managers and state citizens alike.

Wisconsin↗

USGS1983

Commercial geophysical well logs from the USW G-1 drill hole, Nevada Test Site, Nevada

Drill hole USW G-1 was drilled at Yucca Mountain, Nevada Test Site, Nevada, as part of the ongoing exploration program for the Nevada Nuclear Waste Storage Investigations. Contract geophysical well logs run at USW G-1 show only limited stratigraphic correlations, but correlate reasonably well with the welding of the ash-flow and ash-fall tuffs. Rocks in the upper part of the section have highly variable physical properties, but are more uniform and predictably lower in the section.

Open-File Report↗

USGS2021

Supporting the development and use of native plant materials for restoration on the Colorado Plateau (Fiscal Year 2020 Report)

A primary focus of the Colorado Plateau Native Plant Program (CPNPP) is to identify and develop appropriate native plant materials (NPMs) for current and future restoration projects. Multiple efforts have characterized the myriad challenges inherent in providing appropriate seed resources to enable effective, widespread restoration and have identified a broad suite of research activities to provide the information necessary to overcome those challenges (e.g., Plant Conservation Alliance 2015; Breed et al. 2018; Winkler et al. 2018). Many of the most complex information needs relate to identifying the appropriate sources of plant species that can successfully establish in dryland environments, like the Colorado Plateau, where precipitation is generally low and highly variable. Providing this information requires synergistic research efforts that build upon insight gained from earlier investigations. The U.S. Geological Survey (USGS) Southwest Biological Science Center’s (SBSC’s) research activities that supported CPNPP in FY20 followed the FY20 Statement of Work to support a research framework that is continually adapting based on the needs of the restoration community and results from previous investigations; the long-term research framework is outlined in the 2019-2023 5-Year Research Strategy (hereafter referred to as the 5-year plan). This research framework provides support for the National Seed Strategy for Rehabilitation and Restoration (Plant Conservation Alliance, 2015), Department of Interior Secretarial Order #3347 ( Conservation Stewardship and Outdoor Recreation ), and Bureau of Land Management Leadership Priority #1 ( Create a conservation stewardship legacy second only to Teddy Roosevelt ). Research activities in FY20 centered on landscape genomics, implementing a common garden experiment near Vernal, UT, conducting experimental treatments using the GRID (Germination for Restoration Information and Decision-making) framework, and collecting seeds and leaf tissues in the field in preparation for future experiments. These activities were supported by five biological science technicians. The SARS-CoV-2 pandemic delayed some aspects of the FY20 workplan, especially for contract laboratory services and the construction of the GRID garden in Flagstaff, AZ. However, goals were largely met, and the overall progress of research remains on track with respect to the 5-year plan. While Dr. Rob Massatti was the only scientist supported by the SBSC-CPNPP agreement in FY20, other scientists, including Drs. John Bradford, Seth Munson, Mike Duniway, Sasha Reed, Matt Jones, and Daniel Winkler, spent a considerable amount of time providing expertise and support for individual projects. Work activities performed in support of each goal are discussed in turn.

Arizona, Colorado, New Mexico, Utah↗

USGS2014

Topographic lidar survey of the Alabama, Mississippi, and Southeast Louisiana Barrier Islands, from September 5 to October 11, 2012

This Data Series Report contains lidar elevation data collected from September 5 to October 11, 2012, for the barrier islands of Alabama, Mississippi and southeast Louisiana, including the coast near Port Fourchon. Most of the data were collected September 5–10, 2012, with a reflight conducted on October 11, 2012, to increase point density in some areas. Point cloud data—data points described in three dimensions—in lidar data exchange format (LAS), and bare earth digital elevation models (DEMs) in ERDAS Imagine raster format (IMG), are available as downloadable files. The point cloud data were processed to extract bare earth data; therefore, the point cloud data are organized into four classes: 1-unclassified, 2-ground, 7-noise and 9-water. Aero-Metric, Inc., was contracted by the U.S. Geological Survey (USGS) to collect and process these data. The lidar data were acquired at a horizontal spacing (or nominal pulse spacing) of 1 meter (m) or less. The USGS conducted two ground surveys in a small area on Chandeleur Island on September 6, 2012, one on bare earth and the other in both bare earth and vegetated areas. The USGS calculated a vertical root mean square error (RMSEz) of 0.072 m and an offset of 0.007 m using interpolated 2-m by 2-m resolution grid surfaces made from the lidar bare-earth data and the combined USGS ground surveys. Aero-Metric, Inc., calculated an RMSEz of 0.025 m by comparing the USGS bare earth ground survey point data to the closest lidar points. The USGS also conducted a terrestrial lidar survey on Dauphin Island, Louisiana, on September 3, 2012. The USGS calculated a RMSEz of 0.32 m and an offset of 0.27 m, meaning the lidar data were 0.27 m higher than the ground truth (Guy and others, 2013), using interpolated 2-m by 2-m resolution grid surfaces from the airborne lidar bare-earth data and the terrestrial lidar survey. This lidar survey was acquired to document the changes of several different barrier island systems resulting from Hurricane Isaac (Guy and others, 2013). The survey supports detailed studies of Louisiana, Mississippi and Alabama barrier islands that resolve annual and episodic changes in beaches, berms and dunes associated with processes driven by storms, sea-level rise, and even human restoration activities. These lidar data are available to Federal, State and local governments, emergency-response officials, resource managers, and the general public.

Alabama; Louisiana; Mississippi↗

USGS1978

United States Geological Survey uranium and thorium resource assessment and exploration research program, fiscal year 1979

After expansion of the USGS (U.S. Geological Survey) uranium-thorium program in FY (fiscal year) 1975, new directions of research could be pursued, particularly in sedimentology or genetic stratigraphy, geochemistry-mineralogy, and geophysics. In a relatively short time, many of the new research projects have developed critical information on uranium habitats and improved methods of exploration. In FY 1979 a budget increase of approximately 20 percent is programmed, for a funding base of $6,600,000. The increase is scheduled for research grants and contracts outside the USGS in order to extend the basic program without additional personnel. This outside research will be designed not only to increase basic information on uranium occurrence but also to aid the USGS in its evaluation of uranium favorability in key resource areas for the NURE (National Uranium Resource Evaluation) program of DOE (U.S. Department of Energy).

Open-File Report↗

USGS2025

Surficial geology and Quaternary tectonics of the Madison Valley and fault zone, Madison, Gallatin, and Beaverhead Counties, southwest Montana

The north-northwest-striking Madison fault is approximately 95 kilometers in length, lying at the confluence of the northeastern Basin and Range province and the Yellowstone tectonic parabola. The fault zone consists primarily of west-dipping normal faults that have east-dipping antithetic faults, which create the Madison Valley graben and several northeast-trending intrabasin faults. The Madison fault and associated sections discussed herein refer to the main west-dipping, range-bounding fault along the eastern side of the valley. Detailed geologic mapping (1:12,000 scale) of the entire fault zone and fault scarp profiling (total of 102 profiles) of the Madison fault reveal greater late Quaternary paleoseismic activity towards the south, including at least three paleoevents along the southern part of the fault that postdate Pinedale glaciation. Early to middle Holocene alluvial fans have vertical surface offsets that average between 2.0 and 3.0 meters and define the characteristic single-event surface offset. Pinedale lateral moraines have vertical surface offsets as great as 12.0 meters. Late Pleistocene to Holocene multiple-event fault scarps show little evidence of beveling, suggesting short seismic recurrence intervals and potential late Pleistocene and Holocene temporal clustering. Long-term average tectonic activity rates indicate slip rates ranging from 0.18–0.6 millimeters per year. Based on a comparison of fault-scarp height versus maximum slope angle of known regression lines developed from other paleoseismic investigations, the most recent event ranges from 5–1 ka. The northern section of the fault zone is defined by multiple normal faults, which detached the hanging walls of Laramide thrust faults within the Paleozoic and Mesozoic strata. This resulted in the partitioning of extension along multiple preexisting structures and less displacement along individual normal fault strands. Structural controls on lateral propagation of individual paleoevents involve the position of lateral ramps along preexisting Laramide contractional faults. This resulted in greater displacement within the larger basement-cored structures along the southern section of the fault zone, where extension is accommodated by one inferred principal basement-involved normal fault. Inferred east-northeast trending, intrabasin, normal faults within the southern half of the fault zone have no late Pleistocene displacement.

Idaho, Montana, Wyoming↗

USGS2015

Streambed scour evaluations and conditions at selected bridge sites in Alaska, 2012

Streambed scour potential was evaluated at 18 river- and stream-spanning bridges in Alaska that have unknown foundation details or a lack of existing scour analysis. All sites were evaluated for stream stability and long-term scour potential. Contraction scour and abutment scour were calculated for 17 bridges, and pier scour was calculated for 7 bridges that had piers. Vertical contraction (pressure flow) scour was calculated for sites with overtopping floods (where the modeled water surface was higher than the superstructure of the bridge). In most cases, hydraulic models of the 1- and 0.2-percent annual exceedance probability floods (also known as the 100- and 500-year floods, respectively) were used to derive hydraulic variables for the scour calculations. Alternate flood values were used in scour calculations for sites where smaller floods overtopped a bridge or where standard flood-frequency estimation techniques did not apply. Scour was also calculated for large recorded floods at several sites. Equations for scour in cohesive soils were used for sites where streambed sediment was silt-sized or smaller. Channel instability at four sites was related to human activities (in-channel mining, dredging, and channel relocation). Three of the dredged sites are located on active unstable alluvial fans and were graded to inhibit aggradation. The trend toward aggradation during major floods at these sites greatly reduces confidence in scour estimates. Vertical contraction and pressure flow occurred during 1 percent or smaller annual exceedance probability floods at five sites, including three aggradation sites. Contraction scour exceeded 5 feet at two sites, and total scour at piers (pier scour plus contraction scour) exceeded 5 feet at two sites. Debris accumulation increased calculated pier scour at six sites by an average of 1.2 feet. Total scour at abutments including contraction scour exceeded 5 feet at seven sites. Scour estimates seemed excessive at aggradation sites where upstream sediment supply controls scour and deposition processes, at cohesive soil sites where conservative assumptions were made for soil strength and flood duration, and for abutment scour at sites where failure of the embankment and attendant channel widening would reduce scour.

Alaska↗