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At least 1,531 records · Page 85Linked to original sources

USGS2019

sUAS-based remote sensing of river discharge using thermal particle image velocimetry and bathymetric lidar

This paper describes a non-contact methodology for computing river discharge based on data collected from small Unmanned Aerial Systems (sUAS). The approach is complete in that both surface velocity and channel geometry are measured directly under field conditions. The technique does not require introducing artificial tracer particles for computing surface velocity, nor does it rely upon the presence of naturally occurring floating material. Moreover, no prior knowledge of river bathymetry is necessary. Due to the weight of the sensors and limited payload capacities of the commercially available sUAS used in the study, two sUAS were required. The first sUAS included mid-wave thermal infrared and visible cameras. For the field evaluation described herein, a thermal image time series was acquired and a particle image velocimetry (PIV) algorithm used to track the motion of structures expressed at the water surface as small differences in temperature. The ability to detect these thermal features was significant because the water surface lacked floating material (e.g., foam, debris) that could have been detected with a visible camera and used to perform conventional Large-Scale Particle Image Velocimetry (LSPIV). The second sUAS was devoted to measuring bathymetry with a novel scanning polarizing lidar. We collected field measurements along two channel transects to assess the accuracy of the remotely sensed velocities, depths, and discharges. Thermal PIV provided velocities that agreed closely (R^2 = 0.82 and 0.64) with in situ velocity measurements from an acoustic Doppler current profiler (ADCP). Depths inferred from the lidar closely matched those surveyed by wading in the shallower of the two cross sections (R^2 = 0.95) but the agreement was not as strong for the transect with greater depths (R^2 = 0.61). Incremental discharges computed with the remotely sensed velocities and depths were greater than corresponding ADCP measurements by 22% at the first cross section and < 1% at the second.

Colorado↗

USGS2024

Classification of lakebed geologic substrate in autonomously collected benthic imagery using machine learning

Mapping benthic habitats with bathymetric, acoustic, and spectral data requires georeferenced ground-truth information about habitat types and characteristics. New technologies like autonomous underwater vehicles (AUVs) collect tens of thousands of images per mission making image-based ground truthing particularly attractive. Two types of machine learning (ML) models, random forest (RF) and deep neural network (DNN), were tested to determine whether ML models could serve as an accurate substitute for manual classification of AUV images for substrate type interpretation. RF models were trained to predict substrate class as a function of texture, edge, and intensity metrics (i.e., features) calculated for each image. Models were tested using a manually classified image dataset with 9-, 6-, and 2-class schemes based on the Coastal and Marine Ecological Classification Standard (CMECS). Results suggest that both RF and DNN models achieve comparable accuracies, with the 9-class models being least accurate (~73–78%) and the 2-class models being the most accurate (~95–96%). However, the DNN models were more efficient to train and apply because they did not require feature estimation before training or classification. Integrating ML models into benthic habitat mapping process can improve our ability to efficiently and accurately ground-truth large areas of benthic habitat using AUV or similar images.

Michigan, Wisconsin↗

USGS2024

Mapping river flow from thermal images in approximately real time: Proof of concept on the Sacramento River, California, USA

Image velocimetry has become an effective method of mapping flow conditions in rivers, but this analysis is typically performed in a post-processing mode after data collection is complete. In this study, we evaluated the potential to infer flow velocities in approximately real time as thermal images are being acquired from an uncrewed aircraft system (UAS). The sensitivity of thermal image velocimetry to environmental conditions was quantified by conducting 20 flights over four days and assessing the accuracy of image-derived velocity estimates via comparison to direct field measurements made with an acoustic Doppler current profiler (ADCP). This analysis indicated that velocity mapping was most reliable when the air was cooler than the water. We also introduced a workflow for River Velocity Measurement in Approximately Real Time (RiVMART) that involved transferring brief image sequences from the UAS to a ground station as distinct data packets. The resulting velocity fields were as accurate as those generated via post-processing. A new particle image velocimetry (PIV) algorithm based on staggered image sequences increased the number of image pairs available for a given image sequence duration and slightly improved accuracy relative to a standard PIV implementation. Direct, automated geo-referencing of image-derived velocity vectors based on information on the position and orientation of the UAS acquired during flight led to poor alignment with vectors that were geo-referenced manually by selecting ground control points from an orthophoto. This initial proof-of-concept investigation suggests that our workflow could enable highly efficient characterization of flow fields in rivers and might help support applications that require rapid response to changing conditions.

California↗

USGS2024

Reach-scale mapping of surface flow velocities from thermal images acquired by an uncrewed aircraft system along the Sacramento River, California, USA

An innovative payload containing a sensitive mid-wave infrared camera was flown on an uncrewed aircraft system (UAS) to acquire thermal imagery along a reach of the Sacramento River, California, USA. The imagery was used as input for an ensemble particle image velocimetry (PIV) algorithm to produce near-continuous maps of surface flow velocity along a reach approximately 1 km in length. To assess the accuracy of PIV velocity estimates, in situ measurements of flow velocity were obtained with an acoustic Doppler current profiler (ADCP). ADCP measurements were collected along pre-planned cross-section lines within the area covered by the imagery. The PIV velocities showed good agreement with the depth-averaged velocity measured by the ADCP, with R 2 ">

Water↗

USGS2017

Management implications of broadband sound in modulating wild silver carp (Hypophthalmichthys molitrix) behavior

Invasive silver carp (Hypophthalmichthys molitrix) dominate large regions of the Mississippi River drainage, outcompete native species, and are notorious for their prolific and unusual jumping behavior. High densities of juvenile and adult (~25 kg) carp are known to jump up to 3 m above the water surface in response to moving watercraft. Broadband sound recorded from an outboard motor (100 hp at 32 km/hr) can modulate their behavior in captivity; however, the response of wild silver carp to broadband sound has yet to be determined. In this experiment, broadband sound (0.06–10 kHz) elicited jumping behavior from silver carp in the Spoon River near Havana, IL independent of boat movement, indicating acoustic stimulus alone is sufficient to induce jumping. Furthermore, the number of jumping fish decreased with subsequent sound exposures. Understanding silver carp jumping is not only important from a behavioral standpoint, it is also critical to determine effective techniques for controlling this harmful species, such as herding fish into a net for removal.

Illinois↗

USGS2024

Spatial distribution patterns of invasive silver carp can inform removal efforts in an oxbow lake of the Mississippi River

Oxbow lakes are highly productive waterbodies that host multiple life stages of many freshwater aquatic species. These lakes also provide foraging and rearing habitat to the invasive silver carp ( Hypophthalmichthys molitrix ) enabling populations to grow in biomass and abundance that can add propagule pressure to connected waterways and oxbows within the Mississippi River Basin. Ecologically these fish are undesirable because they overlap in diet and may compete for resources with native fishes and negatively impact recreational fisheries. Our goal was to evaluate silver carp distribution patterns in a major Mississippi River oxbow lake to inform removal programs and precision harvesting. We implanted 35 adult silver carp with acoustic tags and released them into the lake. Periodic tracking over 365 d revealed that fish were predominantly found in lake areas with water depths ranging from 2.0 to 5.9 m during all seasons, despite the availability of shallower and deeper water. Silver carp tended to aggregate in the wintertime (December–February) relative to other seasons. This information about lake area uses and seasonal aggregations could inform removal efforts in invaded waterbodies by exploiting natural behavioral and temporal vulnerabilities of this highly invasive and difficult-to-capture fish.

Mississippi↗

USGS2008

Resurgence of emerald shiners Notropis atherinoides in Lake Huron's main basin

Emerald shiners Notropis atherinoides were formerly common in Lakes Huron and Michigan, but declined during the 1960s as the exotic alewife Alosa pseudoharengus proliferated. The Lake Huron emerald shiner population was chronically depressed through 2004; however, we detected resurgence in emerald shiner density and biomass in Lake Huron during acoustic and midwater trawl surveys conducted during 2004–2006. Emerald shiners were not found during 2004, but by 2006 main basin density exceeded 500 fish/ha, biomass estimates exceeded 0.5 kg/ha, and emerald shiners contributed more to pelagic biomass than alewives or rainbow smelt Osmerus mordax . Length frequency distributions suggested that increased density was the result of two consecutive strong year classes in 2005 and 2006. Emerald shiner distributions also expanded from a focus in western Lake Huron in 2005 to a lakewide distribution in 2006. Emerald shiners occurred offshore, but were nearly always associated with epilimnetic surface waters warmer than 19°C. Resurgence of emerald shiners was likely a consequence of reduced alewife abundance, as they declined concurrently with alewife proliferation during the early 1960s. Return of this species may benefit native nearshore piscivores; however, benefits to Pacific salmonids Oncorhynchus spp. are uncertain because emerald shiners are smaller and still less abundant than historically important prey species, and they may be thermally segregated from salmonines.

Journal of Great Lakes Research↗

USGS2022

Assessing the efficacy of oblique bubble screens for control of aquatic invasive species

Non-physical barriers, such as bubble screens (or curtains), are promising low-impact strategies to deter the spread of Aquatic Invasive Species (AIS) in streams. Bubble screens have been successfully implemented to redirect and/or deter adult fish and to capture plastics in some rivers, but their efficacy on invasive fish at multiple life stages (eggs, larvae, and adult fish) is not yet known. Air bubbles rising from a diffuser placed at the bottom of a stream generate counterrotating eddies that interact with the mean flow. Understanding such interactions allows us to design an Oblique Bubble Screen (OBS), a system able to direct drifting particles (i.e., eggs and larvae) towards the banks of a stream for potential capture, based on the water velocity, river morphology, orientation of the OBS, diffuser material, and air flow rate. We present the results from a series of laboratory experiments at the Ecohydraulics and Ecomorphodynamics Laboratory at the University of Illinois at Urbana-Champaign, using positively buoyant (specific gravity SG=0.9, and diameter d=7.09mm) and negatively buoyant (SG=1.04, d=5.9mm) spherical particles to represent the range of size and density of developing Grass carp eggs, an invasive species in North America (Ctenopharyngodon idella). An air compressor was connected to a porous tube laid at the bottom of a recirculating flume, with a regulator and a flow meter to control air pressure and air flow rate. Acoustic Doppler Velocimeters (ADV) and Surface Particle Image Velocimetry (PIV) were used to measure the effect of the OBS on the velocity field. Our collected data showed that: (1) a single OBS is able to direct drifting particles towards the bank at the downstream end of the OBS, (2) adjusting orientation angle and air flow rate of the diffuser can increase capture efficacy under different flow conditions, reaching up to a 100% of capture for buoyant particles, and (3) the ratio between lateral velocity generated by the OBS (as a function of air flow rate) and the mean longitudinal flow velocities, can be used as an indicator to predict whether the OBS will be able to carry the particles all along the length of the diffuser in wider and deeper streams. The optimal configurations from our study will be tested with live Grass carp eggs and larvae, as well as with upstream-swimming adult carp to assess its potential as a two-way barrier, and to provide design parameters to set the air-flow rate and diffuser type needed for field deployments, according to width-to-depth ratios and stream morphology.

Conference Paper↗

USGS2010

Hydraulic alterations resulting from hydropower development in the Bonneville Reach of the Columbia River

We used a two-dimensional (2D) hydrodynamic model to simulate and compare the hydraulic characteristics in a 74-km reach of the Columbia River (the Bonneville Reach) before and after construction of Bonneville Dam. For hydrodynamic modeling, we created a bathymetric layer of the Bonneville Reach from single-beam and multi-beam echo-sounder surveys, digital elevation models, and navigation surveys. We calibrated the hydrodynamic model at 100 and 300 kcfs with a user-defined roughness layer, a variable-sized mesh, and a U.S. Army Corps of Engineers backwater curve. We verified the 2D model with acoustic Doppler current profiler (ADCP) data at 14 transects and three flows. The 2D model was 88% accurate for water depths, and 77% accurate for velocities. We verified a pre-dam 2D model run at 126 kcfs using pre-dam aerial photos from September 1935. Hydraulic simulations indicated that mean water depths in the Bonneville Reach increased by 34% following dam construction, while mean velocities decreased by 58%. There are numerous activities that would benefit from data output from the 2D model, including biological sampling, bioenergetics, and spatially explicit habitat modeling.

Oregon, Washington↗

USGS2016

Deriving habitat models for northern long-eared bats from historical detection data: A case study using the Fernow Experimental Forest

The listing of the northern long-eared bat ( Myotis septentrionalis ) as federally threatened under the Endangered Species Act following severe population declines from white-nose syndrome presents considerable challenges to natural resource managers. Because the northern long-eared bat is a forest habitat generalist, development of effective conservation measures will depend on appropriate understanding of its habitat relationships at individual locations. However, severely reduced population sizes make gathering data for such models difficult. As a result, historical data may be essential in development of habitat models. To date, there has been little evaluation of how effective historical bat presence data, such as data derived from mist-net captures, acoustic detection, and day-roost locations, may be in developing habitat models, nor is it clear how models created using different data sources may differ. We explored this issue by creating presence probability models for the northern long-eared bat on the Fernow Experimental Forest in the central Appalachian Mountains of West Virginia using a historical, presence-only data set. Each presence data type produced outputs that were dissimilar but that still corresponded with known traits of the northern long-eared bat or are easily explained in the context of the particular data collection protocol. However, our results also highlight potential limitations of individual data types. For example, models from mist-net capture data only showed high probability of presence along the dendritic network of riparian areas, an obvious artifact of sampling methodology. Development of ecological niche and presence models for northern long-eared bat populations could be highly valuable for resource managers going forward with this species. We caution, however, that efforts to create such models should consider the substantial limitations of models derived from historical data, and address model assumptions.

West Virginia↗

USGS2019

Activity patterns of bats during the fall and spring along ridgelines in the central Appalachians

Many central Appalachian ridges offer high wind potential, making them attractive to future wind-energy development. Understanding seasonal and hourly activity patterns of migratory bat species may help to reduce fatalities at wind-energy facilities and provide guidance for the development of best management practices for bats. To examine hourly migratory bat activity patterns in the fall and spring in Virginia in an exploratory fashion with a suite of general temporal, environmental, and weather variables, we acoustically monitored bat activity on five ridgelines and side slopes from early September through mid-November 2015 and 2016 and from early March through late April 2016 and 2017. On ridges, bat activity decreased through the autumn sample period, but was more variable through the spring sample period. In autumn, migratory bat activity had largely ceased by mid-November. Activity patterns were species specific in both autumn and spring sample periods. Generally, migratory bat activity was negatively associated with hourly wind speeds but positively associated with ambient temperatures. These data provide further evidence that operational mitigation strategies at wind-energy facilities could help protect migratory bat species in the Appalachians; substantially slowing or locking wind turbine blade spin during periods of low wind speeds, often below where electricity is generated, and warm ambient temperatures may minimize mortality during periods of high bat activity.

Virginia, West Virginia↗

USGS2013

Reliability of fish size estimates obtained from multibeam imaging sonar

Multibeam imaging sonars have considerable potential for use in fisheries surveys because the video-like images are easy to interpret, and they contain information about fish size, shape, and swimming behavior, as well as characteristics of occupied habitats. We examined images obtained using a dual-frequency identification sonar (DIDSON) multibeam sonar for Atlantic sturgeon Acipenser oxyrinchus oxyrinchus , striped bass Morone saxatilis , white perch M. americana , and channel catfish Ictalurus punctatus of known size (20–141 cm) to determine the reliability of length estimates. For ranges up to 11 m, percent measurement error (sonar estimate – total length)/total length × 100 varied by species but was not related to the fish's range or aspect angle (orientation relative to the sonar beam). Least-square mean percent error was significantly different from 0.0 for Atlantic sturgeon ( x̄ = −8.34, SE = 2.39) and white perch ( x̄ = 14.48, SE = 3.99) but not striped bass ( x̄ = 3.71, SE = 2.58) or channel catfish ( x̄ = 3.97, SE = 5.16). Underestimating lengths of Atlantic sturgeon may be due to difficulty in detecting the snout or the longer dorsal lobe of the heterocercal tail. White perch was the smallest species tested, and it had the largest percent measurement errors (both positive and negative) and the lowest percentage of images classified as good or acceptable. Automated length estimates for the four species using Echoview software varied with position in the view-field. Estimates tended to be low at more extreme azimuthal angles (fish's angle off-axis within the view-field), but mean and maximum estimates were highly correlated with total length. Software estimates also were biased by fish images partially outside the view-field and when acoustic crosstalk occurred (when a fish perpendicular to the sonar and at relatively close range is detected in the side lobes of adjacent beams). These sources of bias are apparent when files are processed manually and can be filtered out when producing automated software estimates. Multibeam sonar estimates of fish size should be useful for research and management if these potential sources of bias and imprecision are addressed.

Journal of Fish and Wildlife Management↗

USGS1978

The Aleutian Basin, Bering Sea a frontier area for hydrocarbon exploration

The Aleutian Basin is the deep water (>3000 m) basin that lies north of the Aleutian Islands adjacent to the Bering Sea continental shelf. The basin, about the size of the state of Texas, is underlain by a 2-9 km-thick flat-lying sequence of mostly Cenozoic sediment and rock that includes diatomaceous silty clay interbedded with turbidities in the upper 1 km. Before 1974, geologic and geophysical investigations in the Aleutian Basin were directed at determining its geologic history; more recently, investigations have also been aimed at assessing the basin's hydrocarbon potential. The four major requirements for hydrocarbon accumulation may be present, namely, structural and stratigraphic traps, source rocks, reservoir beds, and an adequate thermal and sedimentation history. Energy resource investigations by the US Geological Survey indicate that: (1) numerous structural features (gentle folds, diapirs, basement ridges) are present in the central and eastern parts of the basin, (2) acoustic features (VAMP's _ Velocity AMPlitude features) that may be due to trapped gases within the sedimentary section are common (over 350 identified) in the central basin, (3) concentrations of organic gases, primarily methane, in the upper 1-3 m beneath the seafloor are very small, they increase with depth, and they are highest in areas near VAMP's, and (4) both the thermal gradient and the sediment thickness are sufficiently great to allow hydrocarbon maturation at depth, if source rocks are present. Adverse conditions in the Aleutian Basin such as excessive water depths and severe weather pose difficult technical problems for the recovery of hydrocarbons that may be present. The data nevertheless suggest the basin is a promising site for hydrocarbon accumulations and therefore warrants further exploration.

Conference Paper↗

USGS2016

Statistical comparison of methods for estimating sediment thickness from Horizontal-to-Vertical Spectral Ratio (HVSR) seismic methods: An example from Tylerville, Connecticut, USA

Determining sediment thickness and delineating bedrock topography are important for assessing groundwater availability and characterizing contamination sites. In recent years, the horizontal-to-vertical spectral ratio (HVSR) seismic method has emerged as a non-invasive, cost-effective approach for estimating the thickness of unconsolidated sediments above bedrock. Using a three-component seismometer, this method uses the ratio of the average horizontal- and vertical-component amplitude spectrums to produce a spectral ratio curve with a peak at the fundamental resonance frequency. The HVSR method produces clear and repeatable resonance frequency peaks when there is a sharp contrast (>2:1) in acoustic impedance at the sediment/bedrock boundary. Given the resonant frequency, sediment thickness can be determined either by (1) using an estimate of average local sediment shear-wave velocity or by (2) application of a power-law regression equation developed from resonance frequency observations at sites with a range of known depths to bedrock. Two frequently asked questions about the HVSR method are (1) how accurate are the sediment thickness estimates? and (2) how much do sediment thickness/bedrock depth estimates change when using different published regression equations? This paper compares and contrasts different approaches for generating HVSR depth estimates, through analysis of HVSR data acquired in the vicinity of Tylerville, Connecticut, USA.

Connecticut↗

USGS2011

Methyl mercury dynamics in a tidal wetland quantified using in situ optical measurements

We assessed monomethylmercury (MeHg) dynamics in a tidal wetland over three seasons using a novel method that employs a combination of in situ optical measurements as concentration proxies. MeHg concentrations measured over a single spring tide were extended to a concentration time series using in situ optical measurements. Tidal fluxes were calculated using modeled concentrations and bi-directional velocities obtained acoustically. The magnitude of the flux was the result of complex interactions of tides, geomorphic features, particle sorption, and random episodic events such as wind storms and precipitation. Correlation of dissolved organic matter quality measurements with timing of MeHg release suggests that MeHg is produced in areas of fluctuating redox and not limited by buildup of sulfide. The wetland was a net source of MeHg to the estuary in all seasons, with particulate flux being much higher than dissolved flux, even though dissolved concentrations were commonly higher. Estimated total MeHg yields out of the wetland were approximately 2.5 μg m −2 yr −1 —4–40 times previously published yields—representing a potential loading to the estuary of 80 g yr −1 , equivalent to 3% of the river loading. Thus, export from tidal wetlands should be included in mass balance estimates for MeHg loading to estuaries. Also, adequate estimation of loads and the interactions between physical and biogeochemical processes in tidal wetlands might not be possible without long-term, high-frequency in situ measurements.

Limnology and Oceanography↗

USGS2011

An inexpensive instrument for measuring wave exposure and water velocity

Ocean waves drive a wide variety of nearshore physical processes, structuring entire ecosystems through their direct and indirect effects on the settlement, behavior, and survivorship of marine organisms. However, wave exposure remains difficult and expensive to measure. Here, we report on an inexpensive and easily constructed instrument for measuring wave-induced water velocities. The underwater relative swell kinetics instrument (URSKI) is a subsurface float tethered by a short (<1 m) line to the seafloor. Contained within the float is an accelerometer that records the tilt of the float in response to passing waves. During two field trials totaling 358 h, we confirmed the accuracy and precision of URSKI measurements through comparison to velocities measured by an in situ acoustic Doppler velocimeter and those predicted by a standard swell model, and we evaluated how the dimensions of the devices, its buoyancy, and sampling frequency can be modified for use in a variety of environments.

Limnology and Oceanography: Methods↗

USGS2012

Bias from false-positive detections and strategies for their removal in studies using telemetry

The use of radio and acoustic telemetry to study aquatic animals has flourished since the 1950s and 1960s (see Section 1). Electronic data-logging receivers are commonly used in both types of active telemetry to record the presence of transmitters in the detection field formed by one or more antennas or hydrophones. As described in Sections 5.1 and 7.1, the path of a transmitter signal to a telemetry receiver can be influenced by many factors and the received signal is not always detected or correctly assigned. It should be of no surprise to users of active telemetry systems that not all records in telemetry receivers are from tagged fish and not all tagged fish are recorded when present. Four types of observations are possible in data from telemetry receiving systems based on the binary nature of presence and absence (Table 1). True positives and true negatives are what one ideally expects from telemetry systems, but in most studies they are accompanied by false negatives (not recorded when present) and false positives (recorded when absent). False negatives arise due to a variety of causes, including insufficient detection area relative to transmitter pulse rate and fish travel speed, collisions between transmitters in the detection area, interference from ambient noise, or a received signal too weak to be recorded (see Sections 3, 5, and 7). The probability of false negatives can be calculated as (1–detection probability) and can be estimated with proper study design and incorporated into estimates of fish presence (see Sections 7.2 and 9.2).

Book chapter↗

USGS2024

River suspended-sand flux computation with uncertainty estimation using water samples and high-resolution ADCP measurements

Measuring suspended-sand fluxes in rivers remains a scientific challenge due to their high spatial and temporal variability. To capture the vertical and lateral gradients of concentration in the cross-section, measurements with point samples are performed. However, the uncertainty related to these measurements is rarely evaluated, as few studies of the major sources of error exist. Therefore, the aim of this study is to develop a method to determine the cross-sectional sand flux and estimate its uncertainty. This SDC (for sand discharge computing) method combines suspended-sand concentrations from point samples with ADCP (acoustic Doppler current profiler) high-resolution depth and velocity measurements. The MAP (for multitransect averaged profile) method allows obtaining an average of several ADCP transects on a regular grid, including the unmeasured areas. The suspended-sand concentrations are integrated vertically by fitting a theoretical exponential suspended-sand profile to the data using Bayesian modeling. The lateral integration is based on the water depth as a proxy for the local bed shear stress to evaluate the bed concentration and sediment diffusion along the river cross-section. The estimation of uncertainty combines ISO standards and semi-empirical methods with a Bayesian approach to estimate the uncertainty due to the vertical integration. The new method is applied to data collected in four rivers under various hydro-sedimentary conditions: the Colorado, Rhône, Isère, and Amazon rivers, with computed flux uncertainties ranging between 18 % and 32 %. The relative difference between the suspended-sand flux in 21 cases calculated with the proposed SDC method compared to the International Organization for Standardization (ISO) 4363 standard method ranges between − 40 % and + 23 %. This method that comes with a flexible, open-source code is the first to propose an applicable uncertainty estimation that could be adapted to other flux computation methods.

Earth Surface Dynamics↗