Geology topics

Steven E. Suttles

Publications and source records attributed to Steven E. Suttles.

13 recordsLinked to original sources

USGS2026

Salt marsh establishment controlled by sediment availability, landscape position, and anthropogenic history

Anthropogenic actions have directly and indirectly modulated salt marsh extent globally. For example, direct actions such as draining and filling of marshes for agriculture were common before the early 20th century, while development on barrier islands has indirectly reduced the capacity of back-barrier marshes to evolve in response to coastal processes. Similarly, restoration efforts span a spectrum between direct actions such as hydrologic reconnection and sediment placement to indirect actions such as shoreline protection and facilitation of upland migration. With a combination of remote sensing and synoptic in-situ observations, we demonstrate that the vegetative establishment of two disparate salt marsh complexes are strongly linked to their access to external sediment supply, position in the coastal landscape, and anthropogenic history. A marsh complex fringing Delaware Bay, in a former agricultural reclamation area, was directly modified through re-introduction of tidal forcing; vegetative establishment occurred rapidly (3% y −1 increase in vegetative cover) due to a high flood-ebb suspended sediment differential (+32 mg l −1 ), indicating sediment import. The other marsh complex, behind a sand spit fronting the Atlantic Ocean, vegetated indirectly in response to updrift beach nourishment which provided a sheltered environment for expansion. The lower suspended sediment differential (+1.3 mg l −1 ) led to a slower vegetation establishment rate (1.7% y −1 ). The directly modified and restored complex responded more rapidly than the indirectly modified and restored complex due to sediment availability. Direct restoration may be more rapid than indirect methods, and reversing anthropogenic impacts is possible on relatively short timescales, if sufficient external sediment supply exists. Siting of restoration projects can therefore leverage external forcing to accelerate recovery and enhance resilience. In light of ongoing coastal transgression, these examples also demonstrate a potential difference in return-on-restoration-investment between back-barrier marshes undergoing coastal squeeze and estuarine fringing marshes that are naturally transgressing across the coastal landscape.

New Jersey↗

USGS2024

Hydroacoustic observations reveal drivers of mixing and salinization of a karst subterranean estuary during intense precipitation

Karst subterranean estuaries within globally ubiquitous carbonate aquifers are coastal groundwater ecosystems that provide an essential water resource for human populations. To understand the drivers of salinization within a coastal aquifer in the Yucatan Peninsula (Mexico), we employed hydroacoustics in flooded caves to observe how oceanic and atmospheric events facilitate mixing between the meteoric lens (fresh-brackish groundwater) and the saline groundwater on tidal and episodic timescales. Precipitation during Tropical Storm Carlotta increased the flow and salinity of the meteoric lens without evidence for vertical mixing across the halocline. We postulate that vertical migration of haloclines in the conduit relative to those within the rock matrix during precipitation creates lateral density gradients that drive mixing, and ultimately creates a brackish layer within the meteoric lens. These results provide a mechanistic explanation for vertical and lateral exchange in a coastal carbonate aquifer, which has implications for groundwater response to future climatic change.

Ox Bel Ha cave system, Yucatan peninsula↗

USGS2024

Calculation of a suspended-sediment concentration-turbidity regression model and flood-ebb suspended-sediment concentration differentials from marshes near Stone Harbor and Thompsons Beach, New Jersey, 2018–19 and 2022–23

The U.S. Geological Survey collected water velocity and water quality data from salt marshes in Great Channel, southwest of Stone Harbor, New Jersey, and near Thompsons Beach, New Jersey, to evaluate restoration effectiveness after Hurricane Sandy and monitor postrestoration marsh health. Time series data of turbidity and water velocity were collected from 2018 to 2019 and 2022 to 2023 at both sites. Water samples were collected and analyzed for suspended-sediment concentration (SSC), which was used to derive a regression model to estimate a time series of SSC data from turbidity data. The SSC time series data were then combined with the water velocity data to calculate the flood-ebb SSC differential. This report presents the data collection methods, the repeated median regression model used to estimate SSC from turbidity, and the flood-ebb SSC differential calculations.

New Jersey↗

USGS2023

Calibrating optical turbidity measurements with suspended-sediment concentrations from the Herring River in Wellfleet, Massachusetts, from November 2018 to November 2019

The sediment budget in the tidally restricted Herring River in Wellfleet, Massachusetts, must be quantified so restoration options for the river can be evaluated. Platforms equipped with optical turbidity sensors were deployed seaward and landward of the Herring River restriction to measure a time series of turbidity, from which a time series of suspended-sediment concentration (SSC) can be estimated. Water samples were collected periodically from the Herring River from November 2018 to November 2019 and analyzed for SSC to derive a relationship to turbidity measurements given in nephelometric turbidity units. This report presents the data-collection methods used and the linear calibration model generated by repeated median regression to convert turbidity measurements to SSC.

Massachusetts↗

USGS2023

State of the science and decision support for measuring suspended sediment with acoustic instrumentation

Acoustic instrumentation can be used to provide time-series and discrete estimates of suspended-sediment concentration, load, and sediment particle sizes in fluvial systems, which are essential for creating informed solutions to many sediment-related environmental, engineering, and land management concerns. Historically, scientists have developed relations between suspended sediment characteristics and other parameters, most commonly streamflow, to estimate sediment information when physical sediment samples cannot be collected. Approaches using streamflow can have substantial accuracy limitations because of hysteresis effects, giving rise to the use of more direct surrogate approaches such as acoustic methods. Interagency efforts in recent years have advanced the testing, methods development, operational guidelines, and training on acoustic methods for measuring suspended sediment. Scientists interested in using these methods are faced with many decisions on the type of application and deployment: horizontal profiling, vertical profiling, or point acoustic instruments; single or multifrequency instruments; continuous or discrete sediment measurements; and fixed or mobile instrument deployments. To promote cost-effective, accurate, and high-resolution fluvial sediment data for the Nation, the interagency Sediment Acoustic Leadership Team (SALT) develops technical guidance and training for using acoustic instruments to measure aquatic sediment. Even though acoustic instrumentation has been used successfully to measure suspended-sediment characteristics throughout the world, some deployments have been unsuccessful because of limited technical guidance and selection of an inappropriate method. To guide decisions on method selection, the SALT has compiled the state of the science for the main types of acoustics-based suspended-sediment measurement methods in development, testing, and use, and has created a flowchart to guide method selection.

Conference Paper↗

USGS2022

Shoaling wave shape estimates from field observations and derived bedload sediment rates

The shoaling transformation from generally linear deep-water waves to asymmetric shallow-water waves modifies wave shapes and causes near-bed orbital velocities to become asymmetrical, contributing to net sediment transport. In this work, we used two methods to estimate the asymmetric wave shape from data at three sites. The first method converted wave measurements made at the surface to idealized near-bottom wave-orbital velocities using a set of empirical equations: the “parameterized” waveforms. The second method involved direct measurements of velocities and pressure made near the seabed: the “direct” waveforms. Estimates from the two methods were well correlated at all three sites (Pearson’s correlation coefficient greater than 0.85). Both methods were used to drive bedload-transport calculations that accounted for asymmetric waves, and the results were compared with a traditional excess-stress formulation and field estimates of bedload transport derived from ripple migration rates based on sonar imagery. The cumulative bedload transport from the parameterized waveform was 25% greater than the direct waveform, mainly because the parameterized waveform did not account for negative skewness. Calculated transport rates were comparable to rates estimated from ripple migration except during the largest event, when calculated rates were as much as 100 times greater, which occurred during high period waves.

Florida, Massachusetts, New York↗

USGS2021

Summary of oceanographic and water-quality measurements offshore of Matanzas Inlet, Florida, 2018

U.S. Geological Survey (USGS) scientists and technical staff deployed instrumented underwater platforms and buoys to collect oceanographic and atmospheric data at two sites near Matanzas Inlet, Florida, on January 24, 2018, and recovered them on April 13, 2018. Matanzas Inlet is a natural, unmaintained inlet on the Florida Atlantic coast that is well suited to study inlet and cross-shore processes. The two study sites were located offshore of the surf zone, in 9 and 15 meters of water depth, in a line perpendicular to the coast. A sea-floor platform was deployed at each site to measure ocean currents, wave motions, acoustic and optical backscatter, temperature, salinity, and pressure. The objective was to quantify the hydrodynamic forcing for sediment transport and the response to such forcing near the seabed in the vicinity of an unmaintained inlet.

Florida↗

USGS2020

Spatiotemporal variability of light attenuation and net ecosystem metabolism in a back-barrier estuary

Quantifying system-wide biogeochemical dynamics and ecosystem metabolism in estuaries is often attempted using a long-term continuous record at a single site or short-term records at multiple sites due to sampling limitations that preclude long-term monitoring. However, differences in the dominant primary producer at a given location (e.g., phytoplankton versus benthic producers) control diel variations in dissolved oxygen and associated ecosystem metabolism, and they may confound metabolic estimates that do not account for this variability. We hypothesize that even in shallow, well-mixed estuaries there is strong spatiotemporal variability in ecosystem metabolism due to benthic and water-column properties, as well as ensuing feedbacks to sediment resuspension, light attenuation, and primary production. We tested this hypothesis by measuring hydrodynamic properties, biogeochemical variables (fluorescent dissolved organic matter – fDOM, turbidity, chlorophyll a fluorescence, dissolved oxygen), and photosynthetically active radiation (PAR) over 1 year at 15 min intervals at paired channel (unvegetated) and shoal (vegetated by eelgrass) sites in Chincoteague Bay, Maryland–Virginia, USA, a shallow back-barrier estuary. Light attenuation ( K dPAR ) at all sites was dominated by turbidity from suspended sediment, with lower contributions from fDOM and chlorophyll a . However, there was significant seasonal variability in the resuspension–shear stress relationship on the vegetated shoals, but not in adjacent unvegetated channels. This indicated that K dPAR on the shoals was mediated by submerged aquatic vegetation (SAV) and possibly microphytobenthos presence in the summer, which reduced resuspension and therefore K dPAR . We also found that gross primary production ( P g ) and K dPAR were significantly negatively correlated on the shoals and uncorrelated in the channels, indicating that P g over the vegetated shoals is controlled by a feedback loop between benthic stabilization by SAV and/or microphytobenthos, sediment resuspension, and light availability. Metabolic estimates indicated substantial differences in net ecosystem metabolism between vegetated and unvegetated sites, with the former tending towards net autotrophy in the summer. Ongoing trends of SAV loss in this and other back-barrier estuaries suggest that these systems may also shift towards net heterotrophy, reducing their effectiveness as long-term carbon sinks. With regards to temporal variability, we found that varying sampling frequency between 15 min and 1 d resulted in comparable mean values of biogeochemical variables, but extreme values were missed by daily sampling. In fact, daily resampling minimized the variability between sites and falsely suggested spatial homogeneity in biogeochemistry, emphasizing the need for high-frequency sampling. This study confirms that properly quantifying ecosystem metabolism and associated biogeochemical variability requires characterization of the diverse estuarine environments, even in well-mixed systems, and demonstrates the deficiencies introduced by infrequent sampling to the interpretation of spatial variability.

Maryland, Virginia↗

USGS2017

Summary of oceanographic and water-quality measurements in Chincoteague Bay, Maryland and Virginia, 2014–15

U.S. Geological Survey scientists and technical support staff measured oceanographic, waterquality, seabed-elevation-change, and meteorological parameters in Chincoteague Bay, Maryland and Virginia, during the period of August 13, 2014, to July 14, 2015, as part of the Estuarine Physical Response to Storms project (GS2–2D) supported by the Department of the Interior Hurricane Sandy recovery program. These measurements provide time series data that quantify the response and can be used to better understand the resilience of this back-barrier estuarine system to storms. The Assateague Island National Seashore (National Park Service) and the Chincoteague National Wildlife Refuge (U.S. Fish and Wildlife Service) are on the east side of Chincoteague Bay.

Maryland, Virginia↗

USGS2016

Summary of oceanographic and water-quality measurements in Barnegat Bay, New Jersey, 2014–15

Scientists and technical support staff from the U.S. Geological Survey measured suspended-sediment concentrations, currents, pressure, and water temperature in two tidal creeks, Reedy Creek and Dinner Creek, in Barnegat Bay, New Jersey, from August 11, 2014, to July 10, 2015 as part of the Estuarine Physical Response to Storms project (GS2–2D). The oceanographic and water-quality data quantify suspended-sediment transport in Reedy Creek and Dinner Creek, which are part of a tidal marsh wetland complex in the Edwin B. Forsythe National Wildlife Refuge. All deployed instruments were removed between January 7, 2015, and April 14, 2015, to avoid damage by ice.

New Jersey↗

USGS2016

Quantification of storm-induced bathymetric change in a back-barrier estuary

Geomorphology is a fundamental control on ecological and economic function of estuaries. However, relative to open coasts, there has been little quantification of storm-induced bathymetric change in back-barrier estuaries. Vessel-based and airborne bathymetric mapping can cover large areas quickly, but change detection is difficult because measurement errors can be larger than the actual changes over the storm timescale. We quantified storm-induced bathymetric changes at several locations in Chincoteague Bay, Maryland/Virginia, over the August 2014 to July 2015 period using fixed, downward-looking altimeters and numerical modeling. At sand-dominated shoal sites, measurements showed storm-induced changes on the order of 5 cm, with variability related to stress magnitude and wind direction. Numerical modeling indicates that the predominantly northeasterly wind direction in the fall and winter promotes southwest-directed sediment transport, causing erosion of the northern face of sandy shoals; southwesterly winds in the spring and summer lead to the opposite trend. Our results suggest that storm-induced estuarine bathymetric change magnitudes are often smaller than those detectable with methods such as LiDAR. More precise fixed-sensor methods have the ability to elucidate the geomorphic processes responsible for modulating estuarine bathymetry on the event and seasonal timescale, but are limited spatially. Numerical modeling enables interpretation of broad-scale geomorphic processes and can be used to infer the long-term trajectory of estuarine bathymetric change due to episodic events, when informed by fixed-sensor methods.

Estuaries and Coasts↗

USGS2016

Colored dissolved organic matter in shallow estuaries: relationships between carbon sources and light attenuation

Light availability is of primary importance to the ecological function of shallow estuaries. For example, benthic primary production by submerged aquatic vegetation is contingent upon light penetration to the seabed. A major component that attenuates light in estuaries is colored dissolved organic matter (CDOM). CDOM is often measured via a proxy, fluorescing dissolved organic matter (fDOM), due to the ease of in situ fDOM sensor measurements. Fluorescence must be converted to CDOM absorbance for use in light attenuation calculations. However, this CDOM–fDOM relationship varies among and within estuaries. We quantified the variability in this relationship within three estuaries along the mid-Atlantic margin of the eastern United States: West Falmouth Harbor (MA), Barnegat Bay (NJ), and Chincoteague Bay (MD/VA). Land use surrounding these estuaries ranges from urban to developed, with varying sources of nutrients and organic matter. Measurements of fDOM (excitation and emission wavelengths of 365 nm (±5 nm) and 460 nm (±40 nm), respectively) and CDOM absorbance were taken along a terrestrial-to-marine gradient in all three estuaries. The ratio of the absorption coefficient at 340 nm (m −1 ) to fDOM (QSU) was higher in West Falmouth Harbor (1.22) than in Barnegat Bay (0.22) and Chincoteague Bay (0.17). The CDOM : fDOM absorption ratio was variable between sites within West Falmouth Harbor and Barnegat Bay, but consistent between sites within Chincoteague Bay. Stable carbon isotope analysis for constraining the source of dissolved organic matter (DOM) in West Falmouth Harbor and Barnegat Bay yielded δ 13 C values ranging from −19.7 to −26.1 ‰ and −20.8 to −26.7 ‰, respectively. Concentration and stable carbon isotope mixing models of DOC (dissolved organic carbon) indicate a contribution of 13 C-enriched DOC in the estuaries. The most likely source of 13 C-enriched DOC for the systems we investigated is Spartina cordgrass. Comparison of DOC source to CDOM : fDOM absorption ratios at each site demonstrates the relationship between source and optical properties. Samples with 13 C-enriched carbon isotope values, indicating a greater contribution from marsh organic material, had higher CDOM : fDOM absorption ratios than samples with greater contribution from terrestrial organic material. Applying a uniform CDOM : fDOM absorption ratio and spectral slope within a given estuary yields errors in modeled light attenuation ranging from 11 to 33 % depending on estuary. The application of a uniform absorption ratio across all estuaries doubles this error. This study demonstrates that light attenuation coefficients for CDOM based on continuous fDOM records are highly dependent on the source of DOM present in the estuary. Thus, light attenuation models for estuaries would be improved by quantification of CDOM absorption and DOM source identification.

Biogeosciences↗

USGS2008

Documentation of the U.S. Geological Survey Oceanographic time-series measurement database

The U.S. Geological Survey (USGS) Oceanographic Time-Series Measurement Database contains oceanographic observations made as part of studies designed to increase understanding of sediment transport processes and associated dynamics. Analysis of these data has contributed to more accurate prediction of the movement and fate of sediments and other suspended materials in the coastal ocean. The measurements were collected primarily by investigators at the USGS Woods Hole Coastal and Marine Science Center (WHCMSC) and colleagues, beginning in 1975. Most of the field experiments were carried out on the U.S. continental shelf and slope. This report describes the instrumentation and platforms used to make the measurements; the methods used to process, apply quality-control criteria, and archive the data; the data storage format, and how the data are released and distributed. The report also includes instructions on how to access the data from the online database at http://stellwagen.er.usgs.gov/ . As of 2016, the database contains about 5,000 files, which may include observations of current velocity, wave statistics, ocean temperature, conductivity, pressure, and light transmission at one or more depths over some duration of time.

Open-File Report↗