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At least 109 records · Page 6Linked to original sources
USGS2003

Automated calibration of a stream solute transport model: Implications for interpretation of biogeochemical parameters

The hydrologic processes of advection, dispersion, and transient storage are the primary physical mechanisms affecting solute transport in streams. The estimation of parameters for a conservative solute transport model is an essential step to characterize transient storage and other physical features that cannot be directly measured, and often is a preliminary step in the study of reactive solutes. Our study used inverse modeling to estimate parameters of the transient storage model OTIS (One dimensional Transport with Inflow and Storage). Observations from a tracer injection experiment performed on Uvas Creek, California, USA, are used to illustrate the application of automated solute transport model calibration to conservative and nonconservative stream solute transport. A computer code for universal inverse modeling (UCODE) is used for the calibrations. Results of this procedure are compared with a previous study that used a trial-and-error parameter estimation approach. The results demonstrated 1) importance of the proper estimation of discharge and lateral inflow within the stream system; 2) that although the fit of the observations is not much better when transient storage is invoked, a more randomly distributed set of residuals resulted (suggesting non-systematic error), indicating that transient storage is occurring; 3) that inclusion of transient storage for a reactive solute (Sr2+) provided a better fit to the observations, highlighting the importance of robust model parameterization; and 4) that applying an automated calibration inverse modeling estimation approach resulted in a comprehensive understanding of the model results and the limitation of input data.

Journal of the North American Benthological Societ↗
USGS2013

Semi-automted analysis of high-resolution aerial images to quantify docks in Upper Midwest glacial lakes

Lake resources can be negatively affected by environmental stressors originating from multiple sources and different spatial scales. Shoreline development, in particular, can negatively affect lake resources through decline in habitat quality, physical disturbance, and impacts on fisheries. The development of remote sensing techniques that efficiently characterize shoreline development in a regional context could greatly improve management approaches for protecting and restoring lake resources. The goal of this study was to develop an approach using high-resolution aerial photographs to quantify and assess docks as indicators of shoreline development. First, we describe a dock analysis workflow that can be used to quantify the spatial extent of docks using aerial images. Our approach incorporates pixel-based classifiers with object-based techniques to effectively analyze high-resolution digital imagery. Second, we apply the analysis workflow to quantify docks for 4261 lakes managed by the Minnesota Department of Natural Resources. Overall accuracy of the analysis results was 98.4% (87.7% based on ) after manual post-processing. The analysis workflow was also 74% more efficient than the time required for manual digitization of docks. These analyses have immediate relevance for resource planning in Minnesota, whereas the dock analysis workflow could be used to quantify shoreline development in other regions with comparable imagery. These data can also be used to better understand the effects of shoreline development on aquatic resources and to evaluate the effects of shoreline development relative to other stressors.

Minnesota↗
USGS2023

Estimating streamflow permanence with the watershed erosion prediction project model: Implications for surface water presence modeling and data collection

Many data collection efforts and modeling studies have focused on providing accurate estimates of streamflow while fewer efforts have sought to identify when and where surface water is present and the duration of surface water presence in stream channels, hereafter referred to as streamflow permanence. While physically-based hydrological models are frequently used to explore how water quantity may be influenced by various climatic and basin characteristics at local, regional, national, and global extents they are less often used to explore streamflow permanence. Herein, the Watershed Erosion Prediction Project (WEPP) hydrological model is applied to watersheds in the humid H. J. Andrews Experimental Forest (HJA) and watersheds of the arid Willow and Whitehorse creeks (WW), both in Oregon, to simulate daily (WW) and annual (HJA and WW) streamflow permanence. One thousand parameter combinations were tested to calibrate WEPP to observed streamflow in the HJA watersheds and one hundred parameter combinations were tested to calibrate WEPP to observed surface water presence time series data in WW watersheds. When calibrated to observed streamflow, WEPP correctly classified annual streamflow permanence for 83% of HJA stream reaches. In the WW, WEPP simulations correctly classified 63–93% of daily streamflow permanence observations and 59-87% of annual streamflow permanence classifications. Inclusion of a dry-day threshold (the maximum number of days a stream reach could be modeled ‘dry’ but still classified as permanent for the year) improved annual accuracy in three WW watersheds from 2-10%. Parameter sets that produced the best daily accuracies in WW resulted in poor annual accuracies. Results highlight the importance of evaluating physically-based streamflow permanence models on both permanent and nonpermanent streams at daily and annual time scales to ensure evaluation metrics are appropriate for interpretation purposes. Additionally, results suggest that strategic collection of surface water presence observations and streamflow observations may support robust calibration of physically based models to simulate streamflow permanence moving forward.

Oregon↗
USGS2023

Using DC resistivity ring array surveys to resolve conductive structures around tunnels or mine-workings

In underground environments, conventional direct current (DC) resistivity surveys with a single linear array of electrodes produce fundamentally non-unique inversions. These non-uniqueness and model resolution issues stem from limitations placed on the location of transmitters (TXs) and receivers (RXs) by the geometry of existing tunnels and boreholes. Poor excitation and/or sampling of the region of interest (ROI) can create artifacts and reduce the resolution of the recovered model. To address these problems we propose the use of an ensemble of ring arrays, which are created by placing one or more electrodes in each face (sidewalls, floor, and ceiling) of the tunnel to form a ring of electrodes at each along-tunnel location. Using a series of increasingly complex synthetic models, we assess the benefits of ring arrays and show that they can be used to better constrain the location and shape of anomalous bodies around the tunnel. Although ring arrays significantly improve the resolution of the recovered model, the size of the comprehensive ring array survey increases rapidly with the number of electrodes used. To balance model resolution and survey size, we developed a physics-based survey design methodology. In this methodology, TXs are selected based upon secondary charge accumulations on a test block that is moved throughout the ROI. Although this survey design methodology does not produce a strictly optimal survey, it balances model resolution and survey size in a practical and computationally efficient manner. Since the ring array more accurately estimates the around-tunnel location of targets and ensures that targets on all sides of the tunnel are detected, it is ideally suited to tunnel-based environments. Our results show that only about 6 % "> 6% of the possible TXs and 0.5 % "> 0.5% of the RXs in the comprehensive ring array survey are needed to retain the improvements in resolution. Therefore, economical ring array surveys can be designed for both reconnaissance and target characterization. Following the inversion of the reconnaissance dataset, additional rings can be added to reduce the inter-ring spacing or off-tunnel boreholes can be added to the region around identified anomalies to increase resolution as required.

Journal of Applied Geophysics↗
USGS2025

Advancing current understanding of Martian impact-generated hydrothermal systems through novel coupled modeling: Insights from Gale, Jezero, and other craters

Impact-generated hydrothermal systems are considered potentially habitable environments on Mars, Earth, and other planetary bodies for microbial life. However, there is an ongoing debate regarding what geological features on Mars provide definitive evidence for such systems. Although earlier studies have modeled hydrothermal processes in Martian craters, they often lacked integration with shock physics hydrocodes to constrain initial impact conditions. The importance of this two-code coupling was demonstrated by successfully replicating alteration signatures in the Earth's Haughton impact structure. In this study, we use a similar two-code approach, combining the iSALE hydrocode with the HYDROTHERM hydrothermal model to simulate the full evolution of impact-generated hydrothermal systems. We apply this method to craters the size of Jezero (∼50 km) and Gale (∼154 km) in diameter. Although Jezero's interior is largely buried, our results align with hypothesized hydrothermal vents and alteration minerals near central uplifts in similarly sized exposed craters, such as Toro and Auki. Furthermore, our models correspond to alteration patterns observed by the Curiosity in the lower layers of Mount Sharp, which may represent remnants of impact-driven hydrothermal activity. A key finding is that these systems may persist much longer than previously estimated. Our simulations suggest that a Jezero-sized system could remain habitable for thermophiles for approximately 720,000 years, whereas a Gale-sized system could persist for nearly 2 million years. Additionally, simulations under unsaturated crustal conditions reveal that air-dominated near-surface layers can suppress vertical fluid flow, enabling deep subsurface alteration without producing detectable mineral signatures at the surface.

Journal of Geophysical Research - Planets↗
USGS2005

The soil physics contributions of Edgar Buckingham

During 1902 to 1906 as a soil physicist at the USDA Bureau of Soils (BOS), Edgar Buckingham originated the concepts of matric potential, soil–water retention curves, specific water capacity, and unsaturated hydraulic conductivity ( K ) as a distinct property of a soil. He applied a formula equivalent to Darcy's law (though without specific mention of Darcy's work) to unsaturated flow. He also contributed significant research on quasi-empirical formulas for K as a function of water content, water flow in capillary crevices and in thin films, and scaling. Buckingham's work on gas flow in soils produced paradigms that are consistent with our current understanding. His work on evaporation elucidated the concept of self-mulching and produced sound and sometimes paradoxical generalizations concerning conditions that favor or retard evaporation. Largely overshadowing those achievements, however, is that he launched a theory, still accepted today, that could predict transient water content as a function of time and space. Recently discovered documents reveal some of the arguments Buckingham had with BOS officials, including the text of a two-paragraph conclusion of his famous 1907 report on soil water, and the official letter documenting rejection of that text. Strained interpersonal relations motivated the departure of Buckingham and other brilliant physicists (N.E. Dorsey, F.H. King, and Lyman Briggs) from the BOS during 1903 to 1906. Given that Buckingham and his BOS colleagues had been rapidly developing the means of quantifying unsaturated flow, these strained relations probably slowed the advancement of unsaturated flow theory.

Soil Science Society of America Journal↗
USGS2015

Point spread functions for earthquake source imaging: An interpretation based on seismic interferometry

Recently, various methods have been proposed and applied for earthquake source imaging, and theoretical relationships among the methods have been studied. In this study, we make a follow-up theoretical study to better understand the meanings of earthquake source imaging. For imaging problems, the point spread function (PSF) is used to describe the degree of blurring and degradation in an obtained image of a target object as a response of an imaging system. In this study, we formulate PSFs for earthquake source imaging. By calculating the PSFs, we find that waveform source inversion methods remove the effect of the PSF and are free from artifacts. However, the other source imaging methods are affected by the PSF and suffer from the effect of blurring and degradation due to the restricted distribution of receivers. Consequently, careful treatment of the effect is necessary when using the source imaging methods other than waveform inversions. Moreover, the PSF for source imaging is found to have a link with seismic interferometry with the help of the source-receiver reciprocity of Green’s functions. In particular, the PSF can be related to Green’s function for cases in which receivers are distributed so as to completely surround the sources. Furthermore, the PSF acts as a low-pass filter. Given these considerations, the PSF is quite useful for understanding the physical meaning of earthquake source imaging.

Geophysical Journal International↗
USGS2024

Predicting the response of fish populations to changes in river connectivity using individual-based models

Barrier removal restores physical stream processes and improves accessibility of critical habitats to migratory fishes. Although increasing connectivity benefits stream systems and migratory fishes, barrier removals may also lead to increased production of undesirable or invasive migratory species, as well as myriad other concerns (e.g., reduced recreational opportunities). Few studies have predicted how migratory fish populations will respond to enhanced fish passage, despite being a critical step in the decision-making process. We developed an individual-based model framework to forecast the response of migratory fishes to changes in connectivity and applied the framework to six species under multiple fish passage scenarios for the FishPass project on the Boardman River, MI, which outlets into Lake Michigan. Population response to barrier removal was species-specific and varied based on initial population size and distribution within the watershed, number of fish passed upstream, and species life history traits. Species restricted to below the barrier prior to removal benefitted most; non-native species were found to have greater production potential under full passage scenarios than native Great Lakes species. With increasing passage of non-native Pacific salmonids, steelhead Oncorhynchus mykiss surpassed brook trout Salvelinus fontinalis as the system’s dominant species. Our results will inform decision-makers on management alternatives for fish passage on the Boardman River and our model framework can be modified, updated, and applied to additional river systems as more barrier removal projects are conducted in the future.

Michigan↗
USGS2025

Identification of representative earthquakes for probabilistic tsunami hazard analysis (PTHA) using earthquake rupture forecasts and machine learning

As probabilistic tsunami hazard analysis (PTHA) focuses more on assessments for localized, populous regions, techniques are needed to identify a subsample of representative earthquake ruptures to make the computational requirements for producing high-resolution hazard maps tractable. Moreover, the greatest epistemic uncertainty in seismic PTHA is related to source characterization, which is often poorly defined and subjective. We address these two salient issues by applying streamlined earthquake rupture forecasts (ERFs), based on combinatorial optimization methods, to an unsupervised machine learning workflow for identifying representative ruptures. ERFs determine the optimal distribution of a millennia-scale sample of earthquakes by inverting the observed slip rate on major faults. We use two previously developed combinatorial optimization ERFs, integer programming and greedy sequential, to produce the optimal location of ruptures with seismic moments sampled from a regional Gutenberg–Richter magnitude–frequency distribution. These ruptures in turn are used to calculate peak nearshore tsunami amplitude, using computationally efficient tsunami Green's functions. An unsupervised machine learning workflow is then used to identify a small subsample of the earthquakes input to ERFs for onshore PTHA analysis. We eliminate epistemic uncertainty related to source distribution under traditional PTHA analysis; in its place, a quantifiable, less subjective and generally smaller uncertainty related to the input to ERFs is included. The Nankai subduction zone is used as a test case, where previous ERFs have been conducted. Results indicate that the locations of representative earthquakes are sensitive to choice of magnitude–area relation and to whether a minimum cumulative stress objective is imposed on the fault. In general, incorporating ERFs into PTHA provide a physically self-consistent method to incorporate fault slip information in determining representative earthquakes for onshore PTHA, eliminating a major source of epistemic uncertainty.

Nankai subduction zone↗
USGS2003

When and where the aftershock activity was depressed: Contrasting decay patterns of the proximate large earthquakes in southern California

Seismic quiescence has attracted attention as a possible precursor to a large earthquake. However, sensitive detection of quiescence requires accurate modeling of normal aftershock activity. We apply the epidemic-type aftershock sequence (ETAS) model that is a natural extension of the modified Omori formula for aftershock decay, allowing further clusters (secondary aftershocks) within an aftershock sequence. The Hector Mine aftershock activity has been normal, relative to the decay predicted by the ETAS model during the 14 months of available data. In contrast, although the aftershock sequence of the 1992 Landers earthquake (M = 7.3), including the 1992 Big Bear earthquake (M = 6.4) and its aftershocks, fits very well to the ETAS up until about 6 months after the main shock, the activity showed clear lowering relative to the modeled rate (relative quiescence) and lasted nearly 7 years, leading up to the Hector Mine earthquake (M = 7.1) in 1999. Specifically, the relative quiescence occurred only in the shallow aftershock activity, down to depths of 5-6 km. The sequence of deeper events showed clear, normal aftershock activity well fitted to the ETAS throughout the whole period. We argue several physical explanations for these results. Among them, we strongly suspect aseismic slips within the Hector Mine rupture source that could inhibit the crustal relaxation process within "shadow zones" of the Coulomb's failure stress change. Furthermore, the aftershock activity of the 1992 Joshua Tree earthquake (M = 6.1) sharply lowered in the same day of the main shock, which can be explained by a similar scenario.

Journal of Geophysical Research B: Solid Earth↗
USGS2015

Slipstream: an early Holocene slump and turbidite record from the frontal ridge of the Cascadia accretionary wedge off western Canada and paleoseismic implications

Slipstream Slump, a well-preserved 3 km wide sedimentary failure from the frontal ridge of the Cascadia accretionary wedge 85 km off Vancouver Island, Canada, was sampled during Canadian Coast Guard Ship (CCGS) John P. Tully cruise 2008007PGC along a transect of five piston cores. Shipboard sediment analysis and physical property logging revealed 12 turbidites interbedded with thick hemipelagic sediments overlying the slumped glacial diamict. Despite the different sedimentary setting, atop the abyssal plain fan, this record is similar in number and age to the sequence of turbidites sampled farther to the south from channel systems along the Cascadia Subduction Zone, with no extra turbidites present in this local record. Given the regional physiographic and tectonic setting, megathrust earthquake shaking is the most likely trigger for both the initial slumping and subsequent turbidity currents, with sediments sourced exclusively from the exposed slump face of the frontal ridge. Planktonic foraminifera picked from the resedimented diamict of the underlying main slump have a disordered cluster of 14 C ages between 12.8 and 14.5 ka BP. For the post-slump stratigraphy, an event-free depth scale is defined by removing the turbidite sediment intervals and using the hemipelagic sediments. Nine 14 C dates from the most foraminifera-rich intervals define a nearly constant hemipelagic sedimentation rate of 0.021 cm/year. The combined age model is defined using only planktonic foraminiferal dates and Bayesian analysis with a Poisson-process sedimentation model. The age model of ongoing hemipelagic sedimentation is strengthened by physical property correlations from Slipstream events to the turbidites for the Barkley Canyon site 40 km south. Additional modelling addressed the possibilities of seabed erosion or loss and basal erosion beneath turbidites. Neither of these approaches achieves a modern seabed age when applying the commonly used regional marine 14 C reservoir age of 800 years (marine reservoir correction Δ R = 400 years). Rather, the top of the core appears to be 400 years in the future. A younger marine reservoir age of 400 years (Δ R = 0 years) brings the top to the present and produces better correlations with the nearby Effingham Inlet paleo-earthquake chronology based only on terrestrial carbon requiring no reservoir correction. The high-resolution dating and facies analysis of Slipstream Slump in this isolated slope basin setting demonstrates that this is also a useful type of sedimentary target for sampling the paleoseismic record in addition to the more studied turbidites from submarine canyon and channel systems. The first 10 turbidites at Slipstream Slump were deposited between 10.8 and 6.6 ka BP, after which the system became sediment starved and only two more turbidites were deposited. The recurrence interval for the inferred frequent early Holocene megathrust earthquakes is 460 ± 140 years, compatible with other estimates of paleoseismic megathrust earthquake occurrence rates along the subduction zone.

Slipstream Slump↗
USGS2012

Displacement fields from point cloud data: Application of particle imaging velocimetry to landslide geodesy

Acquiring spatially continuous ground-surface displacement fields from Terrestrial Laser Scanners (TLS) will allow better understanding of the physical processes governing landslide motion at detailed spatial and temporal scales. Problems arise, however, when estimating continuous displacement fields from TLS point-clouds because reflecting points from sequential scans of moving ground are not defined uniquely, thus repeat TLS surveys typically do not track individual reflectors. Here, we implemented the cross-correlation-based Particle Image Velocimetry (PIV) method to derive a surface deformation field using TLS point-cloud data. We estimated associated errors using the shape of the cross-correlation function and tested the method's performance with synthetic displacements applied to a TLS point cloud. We applied the method to the toe of the episodically active Cleveland Corral Landslide in northern California using TLS data acquired in June 2005–January 2007 and January–May 2010. Estimated displacements ranged from decimeters to several meters and they agreed well with independent measurements at better than 9% root mean squared (RMS) error. For each of the time periods, the method provided a smooth, nearly continuous displacement field that coincides with independently mapped boundaries of the slide and permits further kinematic and mechanical inference. For the 2010 data set, for instance, the PIV-derived displacement field identified a diffuse zone of displacement that preceded by over a month the development of a new lateral shear zone. Additionally, the upslope and downslope displacement gradients delineated by the dense PIV field elucidated the non-rigid behavior of the slide.

California↗
USGS2015

Earthquake rupture process recreated from a natural fault surface

What exactly happens on the rupture surface as an earthquake nucleates, spreads, and stops? We cannot observe this directly, and models depend on assumptions about physical conditions and geometry at depth. We thus measure a natural fault surface and use its 3D coordinates to construct a replica at 0.1 m resolution to obviate geometry uncertainty. We can recreate stick-slip behavior on the resulting finite element model that depends solely on observed fault geometry. We clamp the fault together and apply steady state tectonic stress until seismic slip initiates and terminates. Our recreated M~1 earthquake initiates at contact points where there are steep surface gradients because infinitesimal lateral displacements reduce clamping stress most efficiently there. Unclamping enables accelerating slip to spread across the surface, but the fault soon jams up because its uneven, anisotropic shape begins to juxtapose new high-relief sticking points. These contacts would ultimately need to be sheared off or strongly deformed before another similar earthquake could occur. Our model shows that an important role is played by fault-wall geometry, though we do not include effects of varying fluid pressure or exotic rheologies on the fault surfaces. We extrapolate our results to large fault systems using observed self-similarity properties, and suggest that larger ruptures might begin and end in a similar way, though the scale of geometrical variation in fault shape that can arrest a rupture necessarily scales with magnitude. In other words, fault segmentation may be a magnitude dependent phenomenon and could vary with each subsequent rupture.

Journal of Geophysical Research B: Solid Earth↗
USGS2012

Landscape controls on total and methyl Hg in the Upper Hudson River basin, New York, USA

Approaches are needed to better predict spatial variation in riverine Hg concentrations across heterogeneous landscapes that include mountains, wetlands, and open waters. We applied multivariate linear regression to determine the landscape factors and chemical variables that best account for the spatial variation of total Hg (THg) and methyl Hg (MeHg) concentrations in 27 sub-basins across the 493 km 2 upper Hudson River basin in the Adirondack Mountains of New York. THg concentrations varied by sixfold, and those of MeHg by 40-fold in synoptic samples collected at low-to-moderate flow, during spring and summer of 2006 and 2008. Bivariate linear regression relations of THg and MeHg concentrations with either percent wetland area or DOC concentrations were significant but could account for only about 1/3 of the variation in these Hg forms in summer. In contrast, multivariate linear regression relations that included metrics of (1) hydrogeomorphology, (2) riparian/wetland area, and (3) open water, explained about 66% to >90% of spatial variation in each Hg form in spring and summer samples. These metrics reflect the influence of basin morphometry and riparian soils on Hg source and transport, and the role of open water as a Hg sink. Multivariate models based solely on these landscape metrics generally accounted for as much or more of the variation in Hg concentrations than models based on chemical and physical metrics, and show great promise for identifying waters with expected high Hg concentrations in the Adirondack region and similar glaciated riverine ecosystems.

New York↗
USGS2016

A simple prioritization tool to diagnose impairment of stream temperature for coldwater fishes in the Great Basin

We provide a simple framework for diagnosing the impairment of stream water temperature for coldwater fishes across broad spatial extents based on a weight-of-evidence approach that integrates biological criteria, species distribution models, and geostatistical models of stream temperature. As a test case, we applied our approach to identify stream reaches most likely to be thermally impaired for Lahontan Cutthroat Trout Oncorhynchus clarkii henshawi in the upper Reese River, located in the northern Great Basin, Nevada. We first evaluated the capability of stream thermal regime descriptors to explain variation across 170 sites, and we found that the 7-d moving average of daily maximum stream temperatures (7DADM) provided minimal among-descriptor redundancy and, based on an upper threshold of 20°C, was also a good indicator of acute and chronic thermal stress. Next, we quantified the range of Lahontan Cutthroat Trout within our study area using a geographic distribution model. Finally, we used a geostatistical model to assess spatial variation in 7DADM and predict potential thermal impairment at the stream reach scale. We found that whereas 38% of reaches in our study area exceeded a 7DADM of 20°C and 35% were significantly warmer than predicted, only 17% both exceeded the biological criterion and were significantly warmer than predicted. This filtering allowed us to identify locations where physical and biological impairment were most likely within the network and that would represent the highest management priorities. Although our approach lacks the precision of more comprehensive approaches, it provides a broader context for diagnosing impairment and is a useful means of identifying priorities for more detailed evaluations across broad and heterogeneous stream networks.

Nevada↗
USGS2021

A seasonal electric barrier blocks invasive adult sea lamprey (Petromyzon marinus) and reduces production of larvae

Sea lamprey ( Petromyzon marinus ) control is achieved in the Laurentian Great Lakes by applying lamprey-specific pesticides (lampricides) to habitats containing larval sea lamprey. Lampricide treatments cost less and are more effective in watersheds where dams block adult sea lamprey migration and limit larval distribution relative to watersheds with no barriers to migration. However, dams impound water and can block movement of valued fishes, outcomes that are untenable for some stakeholders. Here, a seasonal and non-physical barrier of pulsed direct electrical current was tested to block adult sea lamprey while also monitoring the movement and mortality of non-target fish species. The electric barrier was operated in the Black Mallard River, a tributary to northern Lake Huron, March through August 2016–2018. The electric field blocked adult sea lamprey; 1056 adult sea lamprey were captured downstream of the electric field and two were captured upstream of the electric barrier over the three-year study. In 2018, larval sea lamprey abundance upstream of the barrier was about 50% less than historical averages, and genetic analysis found that roughly 98% of larvae upstream of the barrier were spawned in years prior to barrier installation. When the barrier was electrified, non-target fish species were blocked, and a small percentage (<3%) were killed. This study demonstrated that a seasonally deployed electric barrier can reduce the abundance of larval sea lamprey upstream without impounding water, but effects on the movements and survival of other fish species remain a concern.

Michigan↗
USGS2009

Urban streams across the USA: Lessons learned from studies in 9 metropolitan areas

Studies of the effects of urbanization on stream ecosystems have usually focused on single metropolitan areas. Synthesis of the results of such studies have been useful in developing general conceptual models of the effects of urbanization, but the strength of such generalizations is enhanced by applying consistent study designs and methods to multiple metropolitan areas across large geographic scales. We summarized the results from studies of the effects of urbanization on stream ecosystems in 9 metropolitan areas across the US (Boston, Massachusetts; Raleigh, North Carolina; Atlanta, Georgia; Birmingham, Alabama; Milwaukee-Green Bay, Wisconsin; Denver, Colorado; Dallas-Fort Worth, Texas; Salt Lake City, Utah; and Portland, Oregon). These studies were conducted as part of the US Geological Survey’s National Water-Quality Assessment Program and were based on a common study design and used standard sample-collection and processing methods to facilitate comparisons among study areas. All studies included evaluations of hydrology, physical habitat, water quality, and biota (algae, macroinvertebrates, fish). Four major conclusions emerged from the studies. First, responses of hydrologic, physical-habitat, water-quality, and biotic variables to urbanization varied among metropolitan areas, except that insecticide inputs consistently increased with urbanization. Second, prior land use, primarily forest and agriculture, appeared to be the most important determinant of the response of biota to urbanization in the areas we studied. Third, little evidence was found for resistance to the effects of urbanization by macroinvertebrate assemblages, even at low levels of urbanization. Fourth, benthic macroinvertebrates have important advantages for assessing the effects of urbanization on stream ecosystems relative to algae and fishes. Overall, our results demonstrate regional differences in the effects of urbanization on stream biota and suggest additional studies to elucidate the causes of these underlying differences.

Alabama, Colorado, Georgia, Massachusetts, North C↗
USGS2022

An integrated approach for physical, economic, and demographic evaluation of coastal flood hazard adaptation in Santa Monica Bay, California

The increased risk of coastal flooding associated with climate-change driven sea level rise threatens to displace communities and cause substantial damage to infrastructure. Site-specific adaptation planning is necessary to mitigate the negative impacts of flooding on coastal residents and the built environment. Cost-benefit analyses used to evaluate coastal adaption strategies have traditionally focused on economic considerations, often overlooking potential demographic impacts that can directly influence vulnerability in coastal communities. Here, we present a transferable framework that couples hydrodynamic modeling of flooding driven by sea level rise and storm scenarios with site-specific building stock and census block-level demographic data. We assess the efficacy of multiple coastal adaptation strategies at reducing flooding, economic damages, and impacts to the local population. We apply this framework to evaluate a range of engineered, nature-based, and hybrid adaptation strategies for a portion of Santa Monica Bay, California. Overall, we find that dual approaches that provide protection along beaches using dunes or seawalls and along inlets using sluice gates perform best at reducing or eliminating flooding, damages, and population impacts. Adaptation strategies that include a sluice gate and partial or no protection along the beach are effective at reducing flooding around inlets but can exacerbate flooding elsewhere, leading to unintended impacts on residents. Our results also indicate trade-offs between economic and social risk-reduction priorities. The proposed framework allows for a comprehensive evaluation of coastal protection strategies across multiple objectives. Understanding how coastal adaptation strategies affect hydrodynamic, economic, and social factors at a local scale can enable more effective and equitable planning approaches.

California↗