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At least 667 records · Page 37Linked to original sources
USGS2023

Targeted metabolomics characterizes metabolite occurrence and variability in stable freshwater mussel populations

Freshwater mussels (order Unionida) play a key role in freshwater systems as ecosystem engineers and indicators of aquatic ecosystem health. The fauna is globally imperilled due to a diversity of suspected factors; however, causes for many population declines and mortality events remain unconfirmed due partly to limited health assessment tools. Mussel-monitoring activities often rely on population-level measurements, such as abundance and age structure, which reflect delayed responses to environmental conditions. Measures of organismal health would enable preemptive detection of declining condition before population-level effects manifest. Metabolomic analysis can identify shifts in biochemical pathways in response to stressors and changing environmental conditions; however, interpretation of the results requires information on inherent variability of metabolite concentrations in mussel populations. We targeted metabolites in the haemolymph of two common mussels, Lampsilis cardium and Lampsilis siliquoidea , from three Indiana streams (USA) using ultra-high-performance liquid chromatography combined with quadrupole time-of-flight mass spectroscopy. The influence of species, stream and sex on metabolite variability was examined with distance-based redundancy analysis. Metabolite variability was most influenced by species, followed by site and sex. Inter- and intraspecies metabolite variability among sexes was less distinct than differences among locations. We further categorized metabolites by occurrence and variability in mussel populations. Metabolites with high occurrence (Categories 1 and 2) included those indicative of energy status (catabolism versus anabolism; arginine, proline, carnitine, nicotinic acid, pantothenic acid), oxidative stress (proline, glutamine, glutamate) and protein metabolism (thymidine, cytidine, inosine). Metabolites with lower occurrence (Category 3) are constituents of assorted metabolic pathways and can be important biomarkers with additional temporal sampling to characterize their variability. These data provide a reference for future temporal (before/after) monitoring and for studies of stressor–metabolite linkages in freshwater mussels.

Indiana↗
USGS2020

Statistical methods in water resources

This text began as a collection of class notes for a course on applied statistical methods for hydrologists taught at the U.S. Geological Survey (USGS) National Training Center. Course material was formalized and organized into a textbook, first published in 1992 by Elsevier as part of their Studies in Environmental Science series. In 2002, the work was made available online as a USGS report. The text has now been updated as a USGS Techniques and Methods Report. It is intended to be a text in applied statistics for hydrology, environmental science, environmental engineering, geology, or biology that addresses distinctive features of environmental data. For example, water resources data tend to have many variables with a lower bound of zero, tend to be more skewed than data from many other disciplines, commonly contain censored data (less than values), and assumptions that the data are normally distributed are not appropriate. Computer-intensive methods (bootstrapping and permutation tests) now improve upon and replace the dependence on t-intervals, t-tests, and analysis of variance. A new chapter on sampling design addresses questions such as “How many observations do I need?” The chapter also presents distribution-free methods to help plan sampling efforts. The trends chapter has been updated to include the WRTDS (Weighted Regressions on Time, Discharge, and Season) method for analysis of water-quality data. This new version contains updated graphics and updated guidance on the use of statistical techniques. The text utilizes R, a programming language and open-source software environment, for all exercises and most graphics, and the R code used to generate figures and examples is provided for download.

Techniques and Methods↗
USGS2000

Geologic Map and Map Database of the Oakland Metropolitan Area, Alameda, Contra Costa, and San Francisco Counties, California

Introduction This report contains a new geologic map at 1:50,000 scale, derived from a set of geologic map databases containing information at a resolution associated with 1:24,000 scale, and a new description of geologic map units and structural relationships in the mapped area. The map database represents the integration of previously published reports and new geologic mapping and field checking by the author (see Sources of Data index map on the map sheet or the Arc-Info coverage pi-so and the textfile pi-so.txt). The descriptive text (below) contains new ideas about the Hayward fault and other faults in the East Bay fault system, as well as new ideas about the geologic units and their relations. These new data are released in digital form in conjunction with the Federal Emergency Management Agency Project Impact in Oakland. The goal of Project Impact is to use geologic information in land-use and emergency services planning to reduce the losses occurring during earthquakes, landslides, and other hazardous geologic events. The USGS, California Division of Mines and Geology, FEMA, California Office of Emergency Services, and City of Oakland participated in the cooperative project. The geologic data in this report were provided in pre-release form to other Project Impact scientists, and served as one of the basic data layers for the analysis of hazard related to earthquake shaking, liquifaction, earthquake induced landsliding, and rainfall induced landsliding. The publication of these data provides an opportunity for regional planners, local, state, and federal agencies, teachers, consultants, and others outside Project Impact who are interested in geologic data to have the new data long before a traditional paper map could be published. Because the database contains information about both the bedrock and surficial deposits, it has practical applications in the study of groundwater and engineering of hillside materials, as well as the study of geologic hazards and the academic research on the geologic history and development of the region.

Miscellaneous Field Studies Map↗
USGS2023

Sediment deposition, erosion, and bathymetric change in San Francisco Bay, California, 1971–1990 and 1999–2020

Bathymetric change analyses document historical patterns of sediment deposition and erosion, providing valuable insight into the sediment dynamics of coastal systems, including pathways of sediment and sediment-bound contaminants. In 2014 and 2015, the Office for Coastal Management, in partnership with the National Oceanic and Atmospheric Administration (NOAA) Office of Coastal Management, provided funding for new bathymetric surveys of large portions of San Francisco Bay. A total of 93 bathymetric surveys were conducted during this 2-year period, using a combination of interferometric sidescan and multibeam sonar systems. These data, along with recent NOAA, U.S. Geological Survey (USGS), U.S. Army Corps of Engineers, and private contractor surveys collected from 1999 to 2020 (hereinafter referred to as 2010s), were used to create the most comprehensive bathymetric digital elevation models (DEMs) of San Francisco Bay since the 1980s. Comparing DEMs created from these 2010s surveys with USGS DEMs created from NOAA’s 1971–1990 (hereinafter referred to as 1980s) surveys provides information on the quantities and patterns of erosion and deposition in San Francisco Bay during the 9 to 47 years between surveys. This analysis reveals that in the areas surveyed in both the 1980s and 2010s, the bay floor lost about 34 million cubic meters of sediment since the 1980s. Results from this study can be used to assess how San Francisco Bay has responded to changes in the system, such as sea-level rise and variation in sediment supply from the Sacramento-San Joaquin Delta and local tributaries, and supports the creation of a new, system-wide sediment budget. This report provides data on the quantities and patterns of sediment volume change in San Francisco Bay for ecosystem managers that are pertinent to various sediment-related issues, including restoration of tidal marshes, exposure of legacy contaminated sediment, and strategies for the beneficial use of dredged sediment.

California↗
USGS2007

Climate and floods still govern California levee breaks

Even in heavily engineered river systems, climate still governs flood variability and thus still drives many levee breaks and geomorphic changes. We assemble a 155-year record of levee breaks for a major California river system to find that breaks occurred in 25% of years during the 20th Century. A relation between levee breaks and river discharge is present that sets a discharge threshold above which most levee breaks occurred. That threshold corresponds to small floods with recurrence intervals of ???2-3 years. Statistical analysis illustrates that levee breaks and peak discharges cycle (broadly) on a 12-15 year time scale, in time with warm-wet storm patterns in California, but more slowly or more quickly than ENSO and PDO climate phenomena, respectively. Notably, these variations and thresholds persist through the 20th Century, suggesting that historical flood-control effects have not reduced the occurrence or frequency of levee breaks. Copyright 2007 by the American Geophysical Union.

Geophysical Research Letters↗
USGS2026

Potential flood events in the lower Missouri River basin over multiple centuries identified using tree-ring based multi-model streamflow reconstructions

The Missouri River basin (MRB), the largest river basin in the United States, presents major water management challenges due to its complex topology and extensive infrastructure designed to manage high annual flows. Severe hydroclimatic events, particularly floods in 1993, 2011, and 2019, have highlighted vulnerabilities, leading the U.S. Army Corps of Engineers to enhance flood risk assessments in 2023. This study focuses on the full MRB, using tree-ring based streamflow reconstructions to extend the Basin's historic streamflow perspective. We developed annual streamflow reconstructions for the Hermann, Missouri streamgage from water years 1360–1900 using K-nearest neighbor and principal component regression methods. These reconstructions incorporate 183 tree-ring chronologies (1360–2020) and modeled natural streamflow (1901–‍2020). Reconstructions were evaluated for consistency using statistical measures and wavelet analysis. Both methods produced similar results, confirming their reliability in reconstructing multi-century streamflows. This novel methodology, guided by wavelet analysis, was developed to identify potential flood events in the lower Missouri River basin (LMRB), resulting in the identification of 172 potential flood events from water years 1360–2020, with 126 events common to the two versions of the MRB reconstructions. The reconstructed streamflow records showed an increase in the number of events until the late-18th- or mid-19th-century. These findings provide insights into evolving flood characteristics in the LMRB. The novel methodology developed in this study can be used to identify potential flood events from tree-ring based annual streamflow reconstructions and generally be applicable to other river basins.

Colorado, Iowa, Kansas, Missouri, Nebraska, Wyomin↗
USGS2011

Seismic zonation of Port-Au-Prince using pixel- and object-based imaging analysis methods on ASTER GDEM

We report about a preliminary study to evaluate the use of semi-automated imaging analysis of remotely-sensed DEM and field geophysical measurements to develop a seismic-zonation map of Port-au-Prince, Haiti. For in situ data, V S 30 values are derived from the MASW technique deployed in and around the city. For satellite imagery, we use an ASTER GDEM of Hispaniola. We apply both pixel- and object-based imaging methods on the ASTER GDEM to explore local topography (absolute elevation values) and classify terrain types such as mountains, alluvial fans and basins/near-shore regions. We assign NEHRP seismic site class ranges based on available V S 30 values. A comparison of results from imagery-based methods to results from traditional geologic-based approaches reveals good overall correspondence. We conclude that image analysis of RS data provides reliable first-order site characterization results in the absence of local data and can be useful to refine detailed site maps with sparse local data.

Port-au-Prince↗
USGS1981

Analysis of variance of thematic mapping experiment data.

As an example of the methodology, data from an experiment using three scales of land-use and land-cover mapping have been analyzed. The binomial proportions of correct interpretations have been analyzed untransformed and transformed by both the arcsine and the logit transformations. A weighted analysis of variance adjustment has been used. There is evidence of a significant difference among the three scales of mapping (1:24 000, 1:100 000 and 1:250 000) using the transformed data. Multiple range tests showed that all three scales are different for the arcsine transformed data. - from Author

Photogrammetric Engineering and Remote Sensing↗
USGS2021

The presence of denitrifiers in bacterial communities of urban stormwater best management practices (BMPs)

Stormwater best management practices (BMPs) are engineered structures that attempt to mitigate the impacts of stormwater, which can include nitrogen inputs from the surrounding drainage area. The goal of this study was to assess bacterial community composition in different types of stormwater BMP soils to establish whether a particular BMP type harbors more denitrification potential. Soil sampling took place over the summer of 2015 following precipitation events. Soils were sampled from four bioretention facilities, four dry ponds, four surface sand filters, and one dry swale. 16S rRNA gene analysis of extracted DNA and RNA amplicons indicated high bacterial diversity in the soils of all BMP types sampled. An abundance of denitrifiers was also indicated in the extracted DNA using presence/absence of nirS, nirK , and nosZ denitrification genes. BMP soil bacterial communities were impacted by the surrounding soil physiochemistry. Based on the identification of a metabolically-active community of denitrifiers, this study has indicated that denitrification could potentially occur under appropriate conditions in all types of BMP sampled, including surface sand filters that are often viewed as providing low potential for denitrification. The carbon content of incoming stormwater could be providing bacterial communities with denitrification conditions. The findings of this study are especially relevant for land managers in watersheds with legacy nitrogen from former agricultural land use.

Maryland↗
USGS2022

Machine learned daily life history classification using low frequency tracking data and automated modelling pipelines: Application to North American waterfowl

Background Identifying animal behaviors, life history states, and movement patterns is a prerequisite for many animal behavior analyses and effective management of wildlife and habitats. Most approaches classify short-term movement patterns with high frequency location or accelerometry data. However, patterns reflecting life history across longer time scales can have greater relevance to species biology or management needs, especially when available in near real-time. Given limitations in collecting and using such data to accurately classify complex behaviors in the long-term, we used hourly GPS data from 5 waterfowl species to produce daily activity classifications with machine-learned models using “automated modelling pipelines”. Methods Automated pipelines are computer-generated code that complete many tasks including feature engineering, multi-framework model development, training, validation, and hyperparameter tuning to produce daily classifications from eight activity patterns reflecting waterfowl life history or movement states. We developed several input features for modeling grouped into three broad categories, hereafter “feature sets”: GPS locations, habitat information, and movement history. Each feature set used different data sources or data collected across different time intervals to develop the “features” (independent variables) used in models. Results Automated modelling pipelines rapidly developed easily reproducible data preprocessing and analysis steps, identification and optimization of the best performing model and provided outputs for interpreting feature importance. Unequal expression of life history states caused unbalanced classes, so we evaluated feature set importance using a weighted F1-score to balance model recall and precision among individual classes. Although the best model using the least restrictive feature set (only 24 hourly relocations in a day) produced effective classifications (weighted F1 = 0.887), models using all feature sets performed substantially better (weighted F1 = 0.95), particularly for rarer but demographically more impactful life history states (i.e., nesting). Conclusions Automated pipelines generated models producing highly accurate classifications of complex daily activity patterns using relatively low frequency GPS and incorporating more classes than previous GPS studies. Near real-time classification is possible which is ideal for time-sensitive needs such as identifying reproduction. Including habitat and longer sequences of spatial information produced more accurate classifications but incurred slight delays in processing.

Movement Ecology↗
USGS2008

Nodal failure index approach to groundwater remediation design

Computer simulations often are used to design and to optimize groundwater remediation systems. We present a new computationally efficient approach that calculates the reliability of remedial design at every location in a model domain with a single simulation. The estimated reliability and other model information are used to select a best remedial option for given site conditions, conceptual model, and available data. To evaluate design performance, we introduce the nodal failure index (NFI) to determine the number of nodal locations at which the probability of success is below the design requirement. The strength of the NFI approach is that selected areas of interest can be specified for analysis and the best remedial design determined for this target region. An example application of the NFI approach using a hypothetical model shows how the spatial distribution of reliability can be used for a decision support system in groundwater remediation design. ?? 2008 ASCE.

Journal of Geotechnical and Geoenvironmental Engin↗
USGS2026

Watershed Continuum Monitoring Approach: Combining multiple water quality patterns along stream and river flowpaths to track sources, pathways, and processing of pollutants

There is a growing need to improve and expand water quality monitoring approaches to more accurately track the sources, fate, and transport of multiple chemicals and pollutants holistically and quantify the effects of best management practices (BMPs) at the watershed scale. An overarching question raised by scientists, environmental managers, and the general public is: how far can water quality impacts from disturbances or benefits from watershed management and restoration propagate along stream and river flowpaths? Many studies using the classic watershed approach focus on analyzing changes in water quality over time at one or a few sampling stations, whereas theories such as the River Continuum Concept focus on predicting shifts in energy sources and biological communities along rivers but have not been directly applied to water quality. We propose to merge these concepts to create a Watershed Continuum Monitoring Approach (WCMA) that combines both spatial and temporal monitoring in order to better detect and quantify trends and transitions in multiple water quality indicators along flowpaths. Specifically, an array of multiple water quality indicators are analyzed at multiple downstream points along a watershed flowpath over time. These multiple water quality indicators are analyzed together for making comparisons to infer hydrological, biological, and geochemical processes controlling sources, transport, and attenuation of pollutants ( e.g. , analagous to stream tracer studies at the watershed scale). The WCMA leverages the natural expansion of watershed areas along a flowpath, which reflect transitions in land use, land cover, and environmental management across spatial and temporal dimensions for making direct comparisons across different stream reaches and spatial trend analysis. WCMA facilitates monitoring of multiple water quality indicators together, and identifcation of hot spots in sources and attenuation of pollutants or mixtures of pollutants. We illustrate practical applications of the WCMA to analyze water quality trends, transitions, and tradeoffs ( i.e. , a tradeoff occurs when one pollutant is reduced but another is directly or indirectly increased downstream). We explore case studies that quantify: (1) downstream reductions in concentrations of multiple pollutants along a stream flowing to a major drinking water source due to engineered and nature-based solutions, (2) downstream reductions in multiple pollutants and water quality tradeoffs along streams experiencing stormwater BMPs and stream restoration, (3) comparisons in downstream reductions of multiple pollutants and nutrient uptake along streams draining into major drinking water sources based on types of stream restoration, (4) comparisons of downstream pollutant reductions along streams experiencing riparian forest conservation vs. stream restoration, and (5) mapping and visualizing hot spots of increasing water quality problems such as hypoxia, contaminant mobilization, and freshwater salinization that extend downstream to tidal rivers of the Chesapeake Bay. We explore future applications of WCMA for tracking decreasing trends in salinity, E. coli , and other pollutants of emerging concern. WCMA can holistically inform progress towards achieving multiple water quality goals and also be used as a screening tool for selecting monitoring sites and targeting management in strategic locations. Overall, WCMA enables the simultaneous quantification and comparison of sources and transport and attenuation rates for different chemicals and pollutants across a broader range of watershed sizes and flowpath lengths, which is critical for understanding ecological, hydrological, geochemical, and biogeochemical processes along human-impacted streams and rivers.

Ecological Engineering↗
USGS2012

Geological and geochemical characterization of the Lower Cretaceous Pearsall Formation, Maverick Basin, south Texas: A future shale gas resource?

As part of an assessment of undiscovered hydrocarbon resources in the northern Gulf of Mexico onshore Mesozoic section, the U.S. Geological Survey (USGS) evaluated the Lower Cretaceous Pearsall Formation of the Maverick Basin, south Texas, as a potential shale gas resource. Wireline logs were used to determine the stratigraphic distribution of the Pearsall Formation and to select available core and cuttings samples for analytical investigation. Samples used for this study spanned updip to downdip environments in the Maverick Basin, including several from the current shale gas-producing area of the Pearsall Formation. The term shale does not adequately describe any of the Pearsall samples evaluated for this study, which included argillaceous lime wackestones from more proximal marine depositional environments in Maverick County and argillaceous lime mudstones from the distal Lower Cretaceous shelf edge in western Bee County. Most facies in the Pearsall Formation were deposited in oxygenated environments as evidenced by the presence of biota preserved as shell fragments and the near absence of sediment laminae, which is probably caused by bioturbation. Organic material is poorly preserved and primarily consists of type III kerogen (terrestrial) and type IV kerogen (inert solid bitumen), with a minor contribution from type II kerogen (marine) based on petrographic analysis and pyrolysis. Carbonate dominates the mineralogy followed by clays and quartz. The low abundance and broad size distribution of pyrite are consistent with the presence of oxic conditions during sediment deposition. The Pearsall Formation is in the dry gas window of hydrocarbon generation (mean random vitrinite reflectance values, R o = 1.2–2.2%) and contains moderate levels of total organic carbon (average 0.86 wt. %), which primarily resides in the inert solid bitumen. Solid bitumen is interpreted to result from in-situ thermal cracking of liquid hydrocarbon generated from original type II kerogen that was prevented from expulsion and migration by low permeability. The temperature of maximum pyrolysis output ( T max ) is a poor predictor of thermal maturity because the pyrolysis (S2) peaks from Rock-Eval analysis are ill defined. Vitrinite reflectance values are consistent with the dry gas window and are the preferred thermal maturity parameter. A Maverick Basin Pearsall shale gas assessment unit was defined using political and geologic boundaries to denote its spatial extent and was evaluated following established USGS hydrocarbon assessment methodology. The assessment estimated a mean undiscovered technically recoverable natural gas resource of 8.8 tcf of gas and 3.4 and 17.8 tcf of gas at the F95 and F5 fractile confidence levels, respectively. Significant engineering challenges will likely need to be met in determining the correct stimulation and completion combination for the successful future development of undiscovered natural gas resources in the Pearsall Formation.

AAPG Bulletin↗
USGS2001

Borehole P- and S-wave velocity at thirteen stations in Southern California

The U.S. Geological Survey (USGS), as part of a program to acquire seismic velocity data at locations of strong-ground motion in earthquakes (e.g., Gibbs et al., 2000), has investigated thirteen additional sites in the Southern California region. Of the thirteen sites, twelve are in the vicinity of Whittier, California, and one is located in San Bernardino, California. Several deployments of temporary seismographs were made after the Whittier Narrows, California earthquake of 1 October 1987 (Mueller et al., 1988). A deployment, between 2 October and 9 November 1987, was the motivation for selection of six of the drill sites. Temporary portable seismographs at Hoover School (HOO), Lincoln School (LIN), Corps of Engineers Station (NAR), Olive Junior High School (OLV), Santa Anita Golf Course (SAG), and Southwestern Academy (SWA) recorded significant aftershock data. These portable sites, with the exception of Santa Anita Golf Course, were co-sited with strong-motion recorders. Stations at HOO, Lincoln School Whittier (WLB), Saint Paul High School (STP), Alisos Adult School (EXC), Cerritos College Gymnasium (CGM), Cerritos College Physical Science Building (CPS), and Cerritos College Police Building (CPB) were part of an array of digital strong-motion stations deployed from "bedrock" in Whittier to near the deepest part of the Los Angeles basin in Norwalk. Although development and siting of this new array (partially installed at the time of this writing) was generally motivated by the Whittier Narrows earthquake, these new sites (with the exception of HOO) were not part of any Whittier Narrows aftershock deployments. A similar new digital strong-motion site was installed at the San Bernardino Fire Station during the same time frame. Velocity data were obtained to depths of about 90 meters at two sites, 30 meters at seven sites, and 18 to 25 meters at four sites. Lithology data from the analysis of cuttings and samples was obtained from the two 90-meter deep holes and from five of the shallower holes to supplement the velocity interpretation. The two 90-meter boreholes (SB1, CPB) have been instrumented with borehole seismometers for continuous monitoring of earthquake activity (Rogers et al., 1998). No drill samples or cuttings were obtained from the other six sites, but driller's logs were scanned for major changes noted there. The velocity models at those sites were interpreted using only the measured data and major changes in the driller's log as noted above. The sites are shown in Figure 1 and listed in Table 1, which gives references to information regarding the strong-motion data. Several hundred strong-motion records of the main-shock were written by this moderate size earthquake (ML = 5.9), making it important from a scientific and engineering prospective (Brady et al., 1988; Shakal et al., 1988).

California↗
USGS2001

Assessing ecosystem effects of reservoir operations using food web-energy transfer and water quality models

We investigated the effects on the reservoir food web of a new temperature control device (TCD) on the dam at Shasta Lake, California. We followed a linked modeling approach that used a specialized reservoir water quality model to forecast operation-induced changes in phytoplankton production. A food web–energy transfer model was also applied to propagate predicted changes in phytoplankton up through the food web to the predators and sport fishes of interest. The food web–energy transfer model employed a 10% trophic transfer efficiency through a food web that was mapped using carbon and nitrogen stable isotope analysis. Stable isotope analysis provided an efficient and comprehensive means of estimating the structure of the reservoir's food web with minimal sampling and background data. We used an optimization procedure to estimate the diet proportions of all food web components simultaneously from their isotopic signatures. Some consumers were estimated to be much more sensitive than others to perturbations to phytoplankton supply. The linked modeling approach demonstrated that interdisciplinary efforts enhance the value of information obtained from studies of managed ecosystems. The approach exploited the strengths of engineering and ecological modeling methods to address concerns that neither of the models could have addressed alone: (a) the water quality model could not have addressed quantitatively the possible impacts to fish, and (b) the food web model could not have examined how phytoplankton availability might change due to reservoir operations.

Ecosystems↗
USGS2020

Exploring the potential of ground-penetrating radar (GPR) to measure the extent of chronic disturbance in peatlands: Examples from acid mine drainage and peat fire

Peatlands are accumulations of partially decayed organic soil that cover approximately 3% of Earth’s surface and have been shown to serve essential environmental and ecological functions such as sequestering carbon, purifying water, and providing habitat for organisms. However, peatlands are threatened by pressures from agriculture, urban development, mining, and climate change. Geophysical methods have been used in peatlands to determine peat volume and carbon stocks (e.g., Comas et al., 2017), observe differences in humification and water content (e.g., Ulriksen, 1982), guide engineering projects (e.g., Jol and Smith, 1995), learn about subsurface greenhouse gas dynamics (Wright and Comas, 2016), observe seasonal variations in pore water salinity (Walter et al., 2018), and assess hydrological processes (Hare et al., 2017). Among various geophysical methods, ground penetrating radar (GPR) is arguably the most popular for studying peat properties given the method’s sensitivity to variations in water content and ability to resolve major structural properties within the peat at high spatial resolution. Though less widely applied, frequency-domain analysis of GPR may also yield useful information.

Conference Paper↗
USGS1996

Hydrologic impact of Great Flood of 1993 in south-central Kansas

The writers analyze the hydrologic budget and quantify the ground-water recharge impact of the Great Flood of 1993 on the Great Bend Prairie aquifer of south-central Kansas. During the summer of 1993, rainfall totals exceeded normal levels by 200% in the northern portion of the study area, while air temperature and evapotranspiration were below normal levels. This extreme event provided the opportunity to revisit previously developed recharge-estimation algorithms. Average ground-water recharge for 1993 at four index sites was estimated at 178 mm using the hybrid water-fluctuation method of Sophocleous. Employing the recharge-estimation multiple-regression methodology of Sophocleous for the area, the writers estimated the 1993 recharge to be 145 mm. Both estimates are higher than the maximum annual recharge observed at the index sites during the 1985–1992 period. A January–July 1993 hydrologic balance analysis resulted in 130 mm of recharge. The recharge caused by the flood was three to more than four times the average annual recharge of the previous eight years. The regression-based recharge-estimation methodology proved to be generally reliable, even under extreme conditions.

Journal of Irrigation and Drainage Engineering↗
USGS1996

The Springdale, Utah, landslide: An extraordinary event

The most dramatic geologic effect of the M-5.7 St. George, Utah earthquake of 2 September 1992 was the triggering of the 14,000,000-m3 Springdale, Utah landslide. The roughly 10 m of landslide movement destroyed three houses, threatened several condominiums, disrupted utility lines, and temporarily closed the southwest entrance to Zion National Park. The seismic triggering of this landslide is puzzling because its distance from the earthquake epicenter, 44 km, is much greater than the farthest distance (18 km) at which similar landslides have been triggered in worldwide earthquakes of the same magnitude. Other Colorado Plateau earthquakes also have produced landslides far beyond worldwide distance limits, which suggests that regional variations in ground-shaking attenuation may require different landslide-triggering distance limits for different seismotectonic regions. Slope stability analysis and historical records of landslide movement suggest that the Springdale landslide was only slightly above limit-equilibrium conditions at the time of the earthquake. Dynamic stability analysis using Newmark's permanent-displacement method indicates coseismic landslide displacement of only 1-8 cm; this rather modest displacement probably induced enough deformation in the montmorillonitic clays along the failure surface to reduce shear strength and destabilize the slide, which continued to move for several hours after the earthquake.

Utah↗