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At least 991 records · Page 55Linked to original sources
USGS2007

The National Streamflow Statistics Program: A Computer Program for Estimating Streamflow Statistics for Ungaged Sites

The National Streamflow Statistics (NSS) Program is a computer program that should be useful to engineers, hydrologists, and others for planning, management, and design applications. NSS compiles all current U.S. Geological Survey (USGS) regional regression equations for estimating streamflow statistics at ungaged sites in an easy-to-use interface that operates on computers with Microsoft Windows operating systems. NSS expands on the functionality of the USGS National Flood Frequency Program, and replaces it. The regression equations included in NSS are used to transfer streamflow statistics from gaged to ungaged sites through the use of watershed and climatic characteristics as explanatory or predictor variables. Generally, the equations were developed on a statewide or metropolitan-area basis as part of cooperative study programs. Equations are available for estimating rural and urban flood-frequency statistics, such as the 1 00-year flood, for every state, for Puerto Rico, and for the island of Tutuila, American Samoa. Equations are available for estimating other statistics, such as the mean annual flow, monthly mean flows, flow-duration percentiles, and low-flow frequencies (such as the 7-day, 0-year low flow) for less than half of the states. All equations available for estimating streamflow statistics other than flood-frequency statistics assume rural (non-regulated, non-urbanized) conditions. The NSS output provides indicators of the accuracy of the estimated streamflow statistics. The indicators may include any combination of the standard error of estimate, the standard error of prediction, the equivalent years of record, or 90 percent prediction intervals, depending on what was provided by the authors of the equations. The program includes several other features that can be used only for flood-frequency estimation. These include the ability to generate flood-frequency plots, and plots of typical flood hydrographs for selected recurrence intervals, estimates of the probable maximum flood, extrapolation of the 500-year flood when an equation for estimating it is not available, and weighting techniques to improve flood-frequency estimates for gaging stations and ungaged sites on gaged streams. This report describes the regionalization techniques used to develop the equations in NSS and provides guidance on the applicability and limitations of the techniques. The report also includes a users manual and a summary of equations available for estimating basin lagtime, which is needed by the program to generate flood hydrographs. The NSS software and accompanying database, and the documentation for the regression equations included in NSS, are available on the Web at http://water.usgs.gov/software/.

Techniques and Methods↗
USGS1987

Checklist of vertebrates of the United States, the U.S. territories, and Canada

On 30 January 1980 the Policy Group of the 1978 Interagency Agreement on Classifications and Inventory established a work group on fish and wildlife species names. The participating agencies were the Fish and Wildlife Service, Forest Service, Bureau of Land Management, Geological Survey, and Soil Conservation Service. The Fish and Wildlife Service was assigned the role of establishing and leading this work group in developing a national list of standard vertebrate species names that is up-to-date and accurate. The Association of Systematic Collections was contracted to develop the reference list. This publication is a revision of portions of the list (amphibians, reptiles, birds, and mammals), including updating to the end of 1985. The geographic areas encompassed by this list are: the United States, including Alaska and Hawaii; the Commonwealth of Puerto Rico, the U.S. Virgin Islands, and Navassa Island; the Trust Territory of the Pacific Islands (the Caroline Islands, Palau Islands, Marshall Islands, and northern Mariana Islands); and the U.S. Territories of American Samoa, Baker Island, Guam, Howland Island, Jarvis Island, the Johnston Islands, Kingman Reef, the Midway Islands, and Wake Islands. Canadian species that do not also occur in the United States have been included. This list includes the names of all Recent species known to occur, or to have occurred, in the geographic areas indicated above. No distinction is made between resident and migratory species or between those that occur regularly and those of casual or accidentally occurrence. The occurrence of all species listed is documented by specimen or photographic evidence. Zoo, aquarium, game park, and hunting preserve populations are not listed, nor are unestablished escapes from such populations. Species that are extinct are marked with a 1 . Species whose only occurrence in an area is the result of introduction by man are marked with a 2 . Species introduced into one area but native to another covered by this checklist do not have a superscript, nor do species for which the documentation of introduction is equivocal. Species listed as Endangered or Threatened (as of January 1987) throughout their ranges are marked with a 3 , whereas species with only selected subspecies or populations so listed are marked with a 4 . Refer to the Code of Federal Regulations (50 CFR) for further details on the Endangered Species Act of 1973 and its requirements. The list includes the scientific names and English names of taxa from order to species. At the level of genus and above, more than one English name may be given; this is to indicate content, not alternative names. English (common or vernacular) names for species vary from region to region and from author to author. The name "gopher", for example, has been applied to kinds of animals as diverse as pocket gophers, ground squirrels, and turtles. Most species have names in other languages as well as English names, and some species lack generally accepted English names. A single English name is given for each species in this list to promote uniformity and to permit more precise communication among users. Accurate communication about species can be assured only by using the scientific names, including their authors and date. We provide an "exploded" illustration (Fig. 1) of a typical portion of the list and identify the elements of each citation.

Resource Publication↗
USGS2011

I3N risk assessment and pathway analysis: Tools for the prevention of biological invasions

Information on invasive alien species from published and unpublished accounts and databases is usually scattered in locations and formats that are not easily accessible. Customized informatics tools for collecting and organizing invasive species information can help resource managers better control biological invasions. The Invasives Information Network (I3N) of the Inter-American Biodiversity Information Network has created a distributed network of databases of invasive species profiles, subject matter experts, projects, and datasets hosted and published online by natural resource institutions throughout the Americas. Invasive species information is documented and published online in a standard format that can be searched by the public. Profiles and occurrence information on invaders can be documented using the I3N Database on Invasive Alien Species, published online using an easy-to-use template, and exchanged in standard formats. The I3N Risk Assessment and Pathway Analysis tools are designed to be used in conjunction with I3N Databases to assist decision-makers in setting priorities for containment. All these tools are freely available online at http://i3n.iabin.net. Coordinated by the United States Geological Survey National Biological Information Infrastructure, this network serves as an example of successful capacity building and regional collaboration on an issue of global significance.

Conference Paper↗
USGS2014

Development of limestone reservoirs in Comal County, Texas

The Edwards limestone, and to a lesser extent the Comanche Peak limestone and the lower part of the Glen Rose limestone below, all of Lower Cretaceous age, form one of the most extensive ground‐water reservoirs in Texas. As a result of normal faulting, these formations are connected by underground channels to form a hydrologic unit which is partly artesian and partly unconfined. Observations in Comal County show that the development of the reservoir by solution is closely related to the geologic history, in which complex faulting and the disconformity between the Edwards and Georgetown limestones are important factors. Various phases of development are shown in different fault blocks, depending upon length of exposure at the surface. The Edwards limestone, which contains the main channels of underground drainage, is almost uniformly permeable from top to bottom, whereas the older, but more recently exposed lower part of the Glen Rose limestone is generally relatively impermeable except where exposed by mature streams.

Texas↗
USGS2008

Joint NOAA/NWS/USGS prototype debris flow warning system for recently burned areas in Southern California

Debris flows, also known as mudslides, are composed gravity-driven mixtures of sediment and water that travel through steep channels, over open hillslopes, and the like. Addressing this issue, US Geological Survey (USGS) and NOAA have established a debris-flow warning system that has the ability to monitor and forecast precipitation and issue timely weather hazard warning. In 2005, this joint NOAA-USGS prototype debris-flow warning system was issued in Southern California and as a result, it has provided valuable information to emergency managers in affected communities.

California↗
USGS2009

Advancing techniques to constrain the geometry of the seismic rupture plane on subduction interfaces a priori: Higher-order functional fits

Ongoing developments in earthquake source inversions incorporate nonplanar fault geometries as inputs to the inversion process, improving previous approaches that relied solely on planar fault surfaces. This evolution motivates advancing the existing framework for constraining fault geometry, particularly in subduction zones where plate boundary surfaces that host highly hazardous earthquakes are clearly nonplanar. Here, we improve upon the existing framework for the constraint of the seismic rupture plane of subduction interfaces by incorporating active seismic and seafloor sediment thickness data with existing independent data sets and inverting for the most probable nonplanar subduction geometry. Constraining the rupture interface a priori with independent geological and seismological information reduces the uncertainty in the derived earthquake source inversion parameters over models that rely on simpler assumptions, such as the moment tensor inferred fault plane. Examples are shown for a number of wellconstrained global locations. We expand the coverage of previous analyses to a more uniform global data set and show that even in areas of sparse data this approach is able to accurately constrain the approximate subduction geometry, particularly when aided with the addition of data from local active seismic surveys. In addition, we show an example of the integration of many two-dimensional profiles into a threedimensional surface for the Sunda subduction zone and introduce the development of a new global threedimensional subduction interface model: Slab1.0. ?? 2009 by the American Geophysical Union.

Geochemistry, Geophysics, Geosystems↗
USGS2014

Magnetic studies of the Florida peninsula

This investigation was undertaken primarily as a pilot‐experiment for gaining information concerning the field‐technique and accuracy which is needed for covering large areas in detail and at the same time economically. Owing to the complex nature of magnetic observations, such a pilot‐study serves, in addition, as a basis for determining the best methods of presenting the results of large areal studies in an easily comprehensible form. The State of Florida was chosen for such preliminary study for the following reasons: First, because it is geologically ideal for such an investigation since it comprises a series of unconsolidated, flat‐lying, Tertiary and Cretaceous sediments of low magnetic permeability covering a complex and much‐folded crystalline basement composed largely of rocks carrying strongly paramagnetic materials; secondly, because information concerning the structural trends of the crystalline basement would be of great interest and importance in the study of Appalachian orogeny and the relationship of the Florida Peninsula to both the Appalachian and Antillean tectonic systems.

Florida↗
USGS2016

Variability and trends in runoff efficiency in the conterminous United States

Variability and trends in water-year runoff efficiency (RE) — computed as the ratio of water-year runoff (streamflow per unit area) to water-year precipitation — in the conterminous United States (CONUS) are examined for the 1951 through 2012 period. Changes in RE are analyzed using runoff and precipitation data aggregated to United States Geological Survey 8-digit hydrologic cataloging units (HUs). Results indicate increases in RE for some regions in the north-central CONUS and large decreases in RE for the south-central CONUS. The increases in RE in the north-central CONUS are explained by trends in climate, whereas the large decreases in RE in the south-central CONUS likely are related to groundwater withdrawals from the Ogallala aquifer to support irrigated agriculture.

Journal of the American Water Resources Associatio↗
USGS2021

Nitrogen and phosphorus sources and delivery from the Mississippi/Atchafalaya River Basin: An update using 2012 SPARROW models

Nitrogen (N) and phosphorus (P) inputs throughout the Mississippi/Atchafalaya River Basin (MARB) have been linked to the Gulf of Mexico hypoxia and water‐quality problems throughout the MARB. To describe N and P loading throughout the MARB, SPAtially Referenced Regression On Watershed attributes (SPARROW) models were previously developed based on nutrient inputs and management similar to 1992 and 2002. In this study, refined SPARROW models were developed with higher resolution basin delineation, updated (2012) source inputs, improved calibration (load) targets, and additional statistical techniques than used in the previous SPARROW models. Based on the refined models, consistent with past models, N and P loads/yields were the highest from the central part of the MARB (Corn Belt) and along the Mississippi River. Agricultural activities remained the most important N and P source, but more so for N because its input, which could now be distinguished from atmospheric deposition, could be estimated. Natural loss of P from geologic material throughout the MARB was an important source, contributing about 23% of the total P from the MARB, and resulted in specific areas, such as Kentucky and Tennessee, being larger sources of P than previously estimated. This information can help managers decide where efforts will have the largest effects (highest ranked areas) on reducing nutrient loading to the Gulf hypoxia and what are the most important sources of N and P in these areas.

Mississippi/Atchafalaya River Basin↗
USGS2011

Rapid wetland expansion during European settlement and its implication for marsh survival under modern sediment delivery rates

Fluctuations in sea-level rise rates are thought to dominate the formation and evolution of coastal wetlands. Here we demonstrate a contrasting scenario in which land-use–related changes in sediment delivery rates drive the formation of expansive marshland, and vegetation feedbacks maintain their morphology despite recent sediment supply reduction. Stratigraphic analysis and radiocarbon dating in the Plum Island Estuary (Massachusetts, United States) suggest that salt marshes expanded rapidly during the eighteenth and nineteenth centuries due to increased rates of sediment delivery following deforestation associated with European settlement. Numerical modeling coupled with the stratigraphic observations suggests that existing marshland could survive, but not form under the low suspended sediment concentrations observed in the estuary today. These results suggest that many of the expansive marshes that characterize the modern North American coast are metastable relicts of high nineteenth century sediment delivery rates, and that recent observations of degradation may represent a slow return to pre-settlement marsh extent. In contrast to ecosystem management practices in which restoring pre-anthropogenic conditions is seen as a way to increase ecosystem services, our results suggest that widespread efforts to restore valuable coastal wetlands actually prevent some systems from returning to a natural state.

Massachusetts↗
USGS2025

Kilometers-scale subsidence of the inner Puerto Rico Trench wall since the Pleistocene

We have observed a thin veneer of Pleistocene-age carbonate rocks on the southern side of Mona Block, a seamount northwest of Puerto Rico, above a water depth of 1800 m. Mona Block is located within the inner wall of the Puerto Rico Trench. A similar veneer of carbonate rocks (corals and pavement) was encountered during a deep submergence vehicle (DSV) Alvin dive in 1976 on the north side of Mona Block at depths of 3650–2900 m. We also observed a remnant Oligocene–Pliocene carbonate platform at a depth of 2080 m on the east side of the block. Restoring the carbonate outcrops to near sea level implies that Mona Block, with a summit currently at 670 m bsl, was an island with an elevation of ≥1000 m until the mid-Pleistocene and has subsided and tilted to the north thereafter. We suggest that the observed subsidence was caused by the foundering or retreating North American slab, which gave rise to the anomalously deep Puerto Rico Trench. Our estimated trench wall subsidence varies nonlinearly from ~800 m in the distal part to ≥3700 m near the trench. Carbonate platform subsidence north of Puerto Rico is older (mid-Pliocene), suggesting that subsidence and, by inference, trench collapse had propagated westward with time. Mona Block is thus a yardstick for studying mantle processes associated with slab retreat and foundering.

Geology↗
USGS1951

Missouri River basin floods of April-May 1950 in North and South Dakota

In area coverage and magnitude of peak discharge the floods of April-May 1950 in the Missouri River Basin in North and South Dakota were unprecedented in the area. These floods were characterized by an extremely late spring breakup of ice, by great flood peaks resulting from snow melt, and by two separate floods in the James River Valley in less than a month. The primary cause of the floods was the rapid melting of the season's great accumulation of snow, one of the deepest on record. In the period between the normal spring breakup time and the actual breakup of river ice, considerably more snow accumulated. Some of this was melted by a few warm days and the melt was stored as water behind snow barriers in upland watercourses. A sudden increase in temperature beginning April 13 and lasting until most of the snow had been converted into runoff resulted in rapid rise of flood waters. Tributary flood waters made the Missouri River from Mobridge to Yankton, S. Dak., rise to near the maximum recorded discharge. At Sioux City, Iowa, the 1950 flood peak-discharge exceeded any previously recorded by the Geological Survey. The center of the flooded area west of the Missouri River lay in the Cannonball River Basin which had the greatest water content of snow on the ground just before the ice broke up Floods north and south of this area were relatively less intense. Scattered records of the Cannonball River and a study of newspaper accounts and other information show that the flood of 1950 was greatest since the area was settled. Flooding of the James River at Jamestown was the greatest since 1897, and the floods of April and May 1950 were of nearly the same stage. Itemized flood damages were made by Federal and State agencies, and relief was sent to the area by the Department of the Army and the American National Red Cross. Data include records of stage and discharge at 54 gaging stations for the period of flood, a summary of peak discharges and comparative data for past and present maxima, a table of crest stages, and weather associated with the 1950 flood.

North Dakota, South Dakota↗
USGS2007

Geologic characteristics of the central stretch of the Ticona Channel, north-central Illinois

The Ticona Channel is located in north-central Illinois and occurs in Grundy, LaSalle, and Putnam counties. It is a buried bedrock valley that served as the principal paleodrainage system in north-central Illinois during the Illinoian and pre-Illinoian. This study focused on the part of the Ticona Channel within the Leonore 7.5??? Quadrangle. The geometry and stratigraphy of sediments that fill the Ticona Channel were investigated using high-resolution, shallow seismic reflection profiling, traditional field geologic mapping techniques, borehole data, and water-well-log data. The valley is about 2 km (1 mi) wide and approximately 60 m (200 ft) deep. The U-shape channel is straight, trends east-west, and has only one mappable tributary. The valley is carved into the Pennsylvanian Carbondale Formation in the eastern part of the study area; it has incised into the Ordovician Prairie du Chien Group in the west. At its base, the Ticona Channel is filled with the Pearl Formation, which is coarse-grained sand and gravel that was deposited during the Illinoian glaciation. The Pearl Formation is overlain by Illinoian till of the Glasford Formation and is capped by Wedron Group sediments from the Wisconsinan stage. Copyright ?? 2007. The American Association of Petroleum Geologists/Division of Environmental Geosciences. All rights reserved.

Environmental Geosciences↗
USGS2020

Geology of the Trout Rock caves (Hamilton Cave, Trout Cave, New Trout Cave) in Pendleton County, West Virginia (USA), and implications regarding the origin of maze caves

The Trout Rock caves (Hamilton Cave, Trout Cave, New Trout Cave) are located in a hill named Cave Knob that overlooks the South Branch of the Potomac River in Pendleton County, West Virginia (U.S.A). The geologic structure of this hill is a northeasttrending anticline, and the caves are located at different elevations primarily along the contact between the Devonian New Creek Limestone (Helderberg Group) and the overlying Devonian Corriganville Limestone (Helderberg Group). The entrance to New Trout Cave (Stop 1) is located on the east flank of Cave Knob anticline at an elevation of 585 m (1,920 ft) relative to sea level, or 39 m (128 ft) above the modern river. Much of the cave consists of passages that extend to the northeast along strike, and many of these passages have developed along primary joints that trend N40E or secondary joints that trend N40W. Sediments in New Trout Cave include mud and sand (some of which was mined for nitrate during the American Civil War), as well as large boulders in the front part of the cave. Gypsum crusts are present in a maze section of the cave ~213 to 305 m (700 to 1,000 ft) from the cave entrance. Excavations in New Trout Cave have produced vertebrate fossils of Rancholabrean age, ~300,000 to 10,000 years Before Present (BP). The entrance to Trout Cave (Stop 2) is located on the east flank of Cave Knob anticline ~100 m (328 ft) northwest of the New Trout Cave entrance at an elevation of 622 m (2,040 ft) relative to sea level, or 76 m (249 ft) above the modern river. Much of the cave consists of passages that extend to the northeast along strike, although a small area of network maze passages is present in the western portion of Trout Cave that is closest to Hamilton Cave. Many of the passages of Trout Cave have developed along primary joints that trend N40E or secondary joints that trend N40W. Sediments in Trout Cave include mud (also mined for nitrate during the American Civil War), as well as large boulders in the front part of the cave. Excavations in the upper levels of Trout Cave have produced vertebrate fossils of Rancholabrean age (~300,000 to 10,000 years BP), whereas excavations in the lower levels of the cave have produced vertebrate fossils of Irvingtonian age (~1,810,000 to 300,000 years BP). The entrance to Hamilton Cave (Stop 3) is located along the axis of Cave Knob anticline ~165 m (540 ft) northwest of the Trout Cave entrance at an elevation of 640 m (2,100 ft) relative to sea level, or 94 m (308 ft) above the modern river. The front (upper) part of Hamilton Cave has a classic network maze pattern that is an angular grid of relatively horizontal passages, most of which follow vertical or near-vertical primary joints that trend N40W and N50W and secondary joints that trend N60W and N80E. This part of the cave lies along the axis of Cave Knob anticline. In contrast, the passages in the back (lower) part of Hamilton Cave lie along the west flank of Cave Knob anticline at ~58 to 85 m (190 to 279 ft) above the modern river. These passages do not display a classic maze pattern, and instead they may be divided into the following two categories: (1) longer northeast-trending passages that are relatively horizontal and follow the strike of the beds; and (2) shorter northwest-trending passages that descend steeply to the west and follow the dip of the beds. Sediments in Hamilton Cave include mud (which was apparently not mined for nitrate during the American Civil War), as well as large boulders in the front part of the cave. Gypsum crusts are present along passage walls of the New Creek Limestone from the Slab Room to the Airblower. Excavations in the front part of Hamilton Cave (maze section) have produced vertebrate fossils of Irvingtonian age (~1,810,000 to 300,000 years BP). The network maze portions of Hamilton Cave are interpreted as having developed at or near the water table where water did not have a free surface in contact with air and where the following conditions were present: (1) Location on or near the axis of an anticline (the location of the greatest amount of flexure); (2) Abundant vertical or near vertical joints, which are favored by location in the area of greatest flexure and by a lithologic unit (chert-rich limestone) that is more likely to experience brittle rather than ductile deformation; (3) Widening of joints to enhance ease of water infiltration, favored by location in area of greatest amount of flexure; and (4) Dissolution along nearly all major joints to produce cave passages of approximately the same size (which would most likely occur via water without a free surface in contact with air). The cave passages that are located along anticline axes and along strike at the New Creek-Corriganville contact are interpreted as having formed initially during times of base level stillstand at or near the water table where water did not have a free surface in contact with air and where the water flowed along the hydraulic gradient at gentle slopes. Under such conditions, dissolution occurred in all directions to produce cave passages with relatively linear wall morphologies. In the lower portions of some of the along-strike passages, the cave walls have a more sinuous (meandering) morphology, which is interpreted as having formed during subsequent initial base level fall as cave development continued under vadose conditions where the water had a free surface in contact with air, and where water flow was governed primarily by gravitational processes. Steeply inclined cave passages that are located along dip at the New Creek-Corriganville contact are interpreted as having formed during subsequent true vadose conditions (after base level fall). This chronology of base level stasis (with cave development in the phreatic zone a short distance below top of water table) followed by base level fall (with cave development in the vadose or epiphreatic zone) has repeated multiple times at Cave Knob during the past ~4 to 3 million years, resulting in multiple cave passages at different elevations, with different passage morphologies, and at different passage locations with respect to strike and dip.

West Virginia↗
USGS2014

Combined multibeam and bathymetry data from Rhode Island Sound and Block Island Sound: a regional perspective

Detailed bathymetric maps of the sea floor in Rhode Island and Block Island Sounds are of great interest to the New York, Rhode Island, and Massachusetts research and management communities because of this area's ecological, recreational, and commercial importance. Geologically interpreted digital terrain models from individual surveys provide important benthic environmental information, yet many applications of this information require a geographically broader perspective. For example, individual surveys are of limited use for the planning and construction of cross-sound infrastructure, such as cables and pipelines, or for the testing of regional circulation models. To address this need, we integrated 14 contiguous multibeam bathymetric datasets that were produced by the National Oceanic and Atmospheric Administration during charting operations into one digital terrain model that covers much of Block Island Sound and extends eastward across Rhode Island Sound. The new dataset, which covers over 1244 square kilometers, is adjusted to mean lower low water, gridded to 4-meter resolution, and provided in Universal Transverse Mercator Zone 19, North American Datum of 1983 and geographic World Geodetic Survey of 1984 projections. This resolution is adequate for sea-floor feature and process interpretation but is small enough to be queried and manipulated with standard Geographic Information System programs and to allow for future growth. Natural features visible in the data include boulder lag deposits of winnowed Pleistocene strata, sand-wave fields, and scour depressions that reflect the strength of oscillating tidal currents and scour by storm-induced waves. Bedform asymmetry allows interpretations of net sediment transport. Anthropogenic features visible in the data include shipwrecks and dredged channels. Together the merged data reveal a larger, more continuous perspective of bathymetric topography than previously available, providing a fundamental framework for research and resource management activities offshore of Rhode Island.

Rhode Island↗
USGS2002

Crustal structure of the coastal and marine San Francisco Bay region, California

As of the time of this writing, the San Francisco Bay region is home to about 6.8 million people, ranking fifth among population centers in the United States. Most of these people live on the coastal lands along San Francisco Bay, the Sacramento River delta, and the Pacific coast. The region straddles the tectonic boundary between the Pacific and North American Plates and is crossed by several strands of the San Andreas Fault system. These faults, which are stressed by about 4 cm of relative plate motion each year, pose an obvious seismic hazard. We have many ways to study earthquake faults. Where faults break the land surface, we may learn valuable information needed for hazard assessment, such as cumulative offset, slip rate, and earthquake history. However, many of the major faults in the region are partly submerged beneath San Francisco and Monterey Bays. Although this situation poses problems in gathering observational data for hazard assessment, bay-region waterways provide an opportunity to study faultzone structure by using marine subsurface-imaging techniques, which are easier and cheaper than equivalent studies on land. In 1993, the U.S. Geological Survey (USGS) launched a 5-year project aimed at unearthing the basic science of the submerged San Andreas strike-slip fault system in the San Francisco Bay region with its many interacting strands. Primary project goals were structural, such as to discover how the San Andreas and Hayward Faults are connected or related at depth, to learn how the complex of faults in the San Andreas stepover zone on the Golden Gate platform functions, and to locate previously unknown faults. This volume thus contains mostly structural information about the San Francisco Bay region, much of it gathered through exploratory geophysical experiments. The volume is organized “top down,” from studies in the shallowest crust to the base of the crust. The first three chapters are linked through their use of novel geophysical techniques to study earthquake effects, coseismic slip, and shallow stratigraphy. Kayen and others examine crustal structure at very high resolution and demonstrate the use of ground-penetrating-radar tomography to measure the liquefaction potential of coastal sedimentary deposits. McGann and others use microfossils from drill cores along the San Francisco-Oakland Bay Bridge to determine a more detailed late Pleistocene stratigraphy of San Francisco Bay than was previously available. Geist and Zoback use the historical record of a small local tsunami generated by the great 1906 San Francisco earthquake to model the rupture process of that earthquake. The last four chapters are dedicated to studies of fault related structure of the seismogenic crust in and around the San Andreas Fault system in the San Francisco Bay region. Jachens and others compile an aeromagnetic anomaly map from new high-resolution flights across the bay region. Some of these anomalies mark the positions of offshore faults, and others are offset by faults, providing constraints on cumulative slip. Hart and others concisely summarize the marine seismic data recorded in and around San Francisco Bay, map the coverage, and provide archival information for those interested in acquiring data. The last two chapters present the results of the seismic data that have been analyzed. Bruns and others present their analysis of high-quality intermediate-resolution (~5-km penetration) seismic-reflection data gathered over the complex San Andreas-San Gregorio Fault junction. This junction, which is thought to be where the 1906 San Francisco earthquake originated (see Geist and Zoback, this volume), contains an apparent extensional right stepover in the San Andreas Fault. Finally, Parsons and others review and summarize the results of deep-crustal seismic-reflection experiments and local-earthquake tomographic studies, including previously unpublished data, and provide additional support and discussion for already-published studies. In summary, these studies were carried out in an environment where background information on faults in the San Francisco Bay region was sought. Much of the structural information presented here comes from experiments of a style unlikely to be conducted by the USGS in the near future. Together, the chapters in this volume provide a structural framework for a major part of a complex strike-slip fault system.

California↗
USGS2012

Bathymetry and capacity of Blackfoot Reservoir, Caribou County, Idaho, 2011

The U.S. Geological Survey (USGS), in cooperation with the Shoshone-Bannock Tribes, surveyed the bathymetry and selected above-water sections of Blackfoot Reservoir, Caribou County, Idaho, in 2011. Reservoir operators manage releases from Government Dam on Blackfoot Reservoir based on a stage-capacity relation developed about the time of dam construction in the early 1900s. Reservoir operation directly affects the amount of water that is available for irrigation of agricultural land on the Fort Hall Indian Reservation and surrounding areas. The USGS surveyed the below-water sections of the reservoir using a multibeam echosounder and real-time kinematic global positioning system (RTK-GPS) equipment at full reservoir pool in June 2011, covering elevations from 6,090 to 6,119 feet (ft) above the North American Vertical Datum of 1988 (NAVD 88). The USGS used data from a light detection and ranging (LiDAR) survey performed in 2000 to map reservoir bathymetry from 6,116 to 6,124 ft NAVD 88, which were mostly in depths too shallow to measure with the multibeam echosounder, and most of the above-water section of the reservoir (above 6,124 ft NAVD 88). Selected points and bank erosional features were surveyed by the USGS using RTK-GPS and a total station at low reservoir pool in September 2011 to supplement and verify the LiDAR data. The stage-capacity relation was revised and presented in a tabular format. The datasets show a 2.0-percent decrease in capacity from the original survey, due to sedimentation or differences in accuracy between surveys. A 1.3-percent error also was detected in the previously used capacity table and measured water-level elevation because of questionable reference elevation at monitoring stations near Government Dam. Reservoir capacity in 2011 at design maximum pool of 6,124 ft above NAVD 88 was 333,500 acre-ft.

Idaho↗
USGS2021

Groundwater hydrology and chemistry of Jamestown Island, Virginia—Potential effects of tides, storm surges, and sea-level rise on archaeological, cultural, and ecological resources

As the site of the first permanent English settlement in North America in 1607, Jamestown Island, Colonial National Historical Park (COLO), Virginia, contains a rich archaeological record that extends from the Paleoindian period (15,000 to 8,000 years ago) through the 20th century. The island is located on the lower James River near the mouth of Chesapeake Bay. Jamestown Island vegetation is dominated by upland forests surrounded by tidal, freshwater-to-oligohaline marshes. Along the Virginia coast, relative sea-level rise was more than 2.5 times the global average during the 20th century. Consequently, the National Park Service (NPS) has identified COLO as one of the 25 national parks most threatened by climate change. Surface waters across the island are hydraulically connected to the laterally continuous Surficial aquifer. The land-surface altitude of the island is low, with two-thirds of the island less than 5 feet (ft) above the North American Vertical Datum of 1988 (NAVD 88). Consequently, sea-level rise, combined with tides and storm surges, threatens the island and its resources as surface-water and groundwater levels rise, saltwater enters the Surficial aquifer, and groundwater chemistry changes. The impact of sea-level rise on the island’s surface-water resources has been well studied, but groundwater effects have been largely ignored. Quantifying the effects of tides, storm surges, and sea-level rise on groundwater levels and chemistry is essential to developing an effective strategy for managing climate-induced changes. The first step in developing a response strategy includes a parkwide general risk assessment for archaeological sites on the island, so that sites can be prioritized for management actions. The U.S. Geological Survey and the NPS began a study in 2015 to develop a long-term groundwater-monitoring program to evaluate this risk and to develop an updated management strategy. The groundwater-monitoring program consists of 45 wells and piezometers in two individual clusters and three transects across the island in different hydrologic and chemical settings. Samples for water quality were collected from the wells and piezometers from October 2015 through September 2018 at variable time intervals. Results of the monitoring identified disparate hydrologic and chemical responses to saltwater intrusion across the island. Specific conductance (an indicator of salinity) of groundwater beneath several marshes responded differently to changes in James River salinity. Groundwater response to changes in James River specific conductance appeared to be controlled by land-surface altitude and slope, differences in lateral and vertical sediment characteristics, distance from surface waters, and the degree of surface water/groundwater connectivity between channels and the aquifer. Groundwater chemistry data from monitoring wells at Black Point, a low-altitude, upland setting, are in contrast with conditions observed in Island House observation wells, a high-altitude, upland setting. Specific conductance (less than 200 microsiemens per centimeter [μS/cm]) and pH (greater than 5.0) of groundwater beneath much of the uplands that characterize the Island House observation wells are typical of groundwater in noncarbonate sedimentary aquifers recharged by precipitation. At Black Point, specific conductance ranged from 2,490 to 15,200 μS/cm, and pH ranged from 3.1 to 6.6 standard units. At the Black Point observation wells, the most saline and dense water was at the water table rather than deeper in the aquifer, causing a density inversion that persisted throughout the study. The density inversion likely resulted from differences in permeability between the shallow clay and fine-grained sands and the deeper coarse-grained sand and gravel. Groundwater with the lowest pH was at the water table. As saline groundwater flows through organic sediment beneath the marshes, bacterial biodegradation of organic matter creates anoxic conditions. Continued biodegradation concomitantly reduces iron-oxide minerals in the sediment and sulfate in saline water. When oxygen is reintroduced into groundwater, iron and sulfur can reoxidize to form sulfuric acid, locally lowering the pH of the water. This report describes the groundwater monitoring network design, rationale for site selection, monitoring approach, and results of monitoring from October 2015 through September 2018. Maps of inundation at selected water-level altitudes are included to identify the risk to archaeological, cultural, and ecological resources. The monitoring results of the hydrology and chemistry data are interpreted, and the different hydrologic and chemical settings are described. The implications of the study results for management decisions are presented, and suggestions for improving the monitoring network are included.

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