Carl Friedrichs

Virginia Institute of Marine Science · Chesapeake Bay National Estuarine Research Reserve in Virginia

The geotechnical evaluation of seabed sediments is important for engineering projects and naval applications, offering valuable insights into sediment properties, behavior, and strength. Obtaining high-quality seabed samples can be a challenging task, making in-situ testing an essential part of site characterization. Free Fall Penetrometers (FFP) h...

Hypoxia in coastal waters is a pressing ecological problem caused by continued eutrophication and climatic change that has widespread consequences for metazoan life and biogeochemical cycles. Numerous studies have investigated the controls on seasonal hypoxia formation and persistence in many of the world’s large estuaries and coastal hypoxic zones...

This data repository is a permanent archive of the results presented in the associated publication (Turner et al. 2022, Limnology & Oceanography Letters, https://doi.org/10.1002/lol2.10301). The objective of this study was to illustrate a water clarity phenomenon in the lower York River Estuary of the Chesapeake Bay. The data include light attenuat...

The objectives of this study are to better understand controls on bed erodibility in muddy estuaries, including the roles of both sediment properties and recent hydrodynamic history. An extensive data set of erodibility measurements, sediment properties, and hydrodynamic information was utilized to create statistical models to predict the erodibili...

While ecosystem health is improving in many estuaries worldwide following nutrient reductions, inconsistent trends in water clarity often remain. The Chesapeake Bay, a eutrophic estuary with a highly populated watershed, is a crucial testbed for these concerns. Improved efforts are needed to understand why some measurements of downstream estuarine...

While ecosystem health is improving in many estuaries worldwide following nutrient reductions, inconsistent trends in water clarity often remain. The Chesapeake Bay, a eutrophic estuary with a highly populated watershed, is a crucial testbed for these concerns. Improved efforts are needed to understand why some measurements of downstream estuarine...

While ecosystem health is improving in many estuaries worldwide following nutrient reductions, inconsistent trends in water clarity measurements often remain. The Chesapeake Bay, a eutrophic estuary with a highly populated watershed, is a crucial testbed for these concerns. Improved efforts are needed to understand why some measurements of downstre...

Shoreline erosion supplies sediments to estuaries and coastal waters, influencing water clarity and primary production. Globally, shoreline erosion sediment inputs are changing with anthropogenic alteration of coastlines in populated regions. Chesapeake Bay, a prime example of such a system where shoreline erosion accounts for a large proportion of...

While water quality is improving in many estuaries worldwide following nutrient reductions, ambiguous trends in water clarity often follow despite declining nutrient concentrations. The Chesapeake Bay, a highly populated eutrophic estuary, is a crucial testbed for this issue. Efforts are needed to understand why downstream estuarine water clarity i...

While ecosystem health is improving in many estuaries worldwide following nutrient reductions, inconsistent trends in water clarity measurements often remain. The Chesapeake Bay, a eutrophic estuary with a highly populated watershed, is a crucial testbed for these concerns. Improved efforts are needed to understand why some measurements of downstre...

The Chesapeake Bay is the largest estuary in the United States, and its watershed is home to more than 18 million people. Over the last several decades, the Chesapeake Bay has experienced a significant net decline in estuarine water clarity in conjunction with rapid human population growth within its watershed. Despite long-term reductions in river...

Shoreline erosion supplies sediments to estuaries and coastal waters, influencing water clarity and primary production. Globally, shoreline erosion sediment inputs are changing with anthropogenic alteration of coastlines. Chesapeake Bay serves as a case study for investigating the effects of changing sediment inputs on water clarity. Long-term incr...

While ecosystem health is improving in many estuaries worldwide following nutrient reductions, ambiguous trends in water clarity often remain. The Chesapeake Bay, a highly populated eutrophic estuary, is a crucial testbed for this issue. Efforts are needed to understand why downstream estuarine water clarity appears uncorrelated with watershed mana...

Shoreline erosion supplies sediments to estuaries and coastal waters, influencing water clarity and primary production. Globally, shoreline erosion sediment inputs are changing with anthropogenic alteration of coastlines in populated regions. Chesapeake Bay, a prime example of such a system where shoreline erosion accounts for a large proportion of...

To better understand the nature of flocs of varying organic content in estuarine surface waters, Laser in situ Scattering and Transmissometry, video settling, and pump sampling were deployed in the York River estuary. A new in situ method was developed to simultaneously solve the floc fractal dimension (F), primary particle size (dp), and primary p...

This data repository is a permanent archive of the results presented in the associated publication (Turner et al. 2020, Science of the Total Environment, doi: 10.1016/j.scitotenv.2021.145157). The objective of this study was to investigate the effects of shoreline erosion on water clarity in the Chesapeake Bay. To this end, we used the Chesapeake B...

Aggregation state significantly influences the size, density, and transport characteristics of fine sediment. Understanding sediment transport and deposition processes in the nation's navigable waterways is a primary mission for the US Army Corps of Engineers (USACE), particularly when it comes to infilling of navigation channels. In this study, a...

Despite long-term reductions in riverine sediment and nutrient loading, the mainstem of the Chesapeake Bay has shown a lack of improvement in water clarity as measured by Secchi depth. Shoreline erosion may account for part of this discrepancy, as it provides a significant source of fine sediment loading to the Bay. This study examined the relative...

In the classical theory of the Secchi disk depth, diffuse sunlight falling on the disk is reflected back to the observer's eye along the most direct route, as a beam. The disappearance depth, ZSD, of the disk is then expected to vary inversely with the sum of the beam and diffuse attenuation coefficients: c + KD. Observations presented here show th...

The Chesapeake Bay is the largest estuary in the U.S. with the highest land-to-water ratio of any estuarine watershed in the world. Management policies actively limit watershed inputs of nutrients and sediments to the estuary. In this heavily-populated, highly-managed system, it is imperative to understand water clarity change over time. Remote sen...

Over the last several decades, the Chesapeake Bay has experienced a significant net decline in estuarine water clarity in conjunction with rapid human population growth within its watershed. Despite long-term reductions in riverine sediment loading, the main stem of the Bay has shown a lack of improvement in water clarity as measured by Secchi dept...

As the oyster aquaculture industry grows and becomes incorporated into management practices, it is important to understand its effects on local environments. This study investigated how water quality and hydrodynamics varied among farms as well as inside versus outside the extent of caged grow-out areas located in southern Chesapeake Bay. Current s...

Over the last several decades, the Chesapeake Bay has experienced a significant net decline in estuarine water clarity in conjunction with rapid human population growth within its watershed. Despite long-term reductions in riverine sediment loading, the main stem of the Bay has shown a lack of improvement in water clarity as measured by Secchi dept...

A Data Repository for Minimal Effects of Oyster Aquaculture on Water Quality: Examples from Southern Chesapeake Bay. https://scholarworks.wm.edu/data/417/

Particle settling velocity and erodibility are key factors that govern the transport of sediment through coastal environments including estuaries. These are difficult to parameterize in models that represent mud, whose properties can change in response to many factors, including tidally varying suspended sediment concentration (SSC) and shear stres...

In situ geotechnical testing of surficial sediment layers in areas of active sediment dynamics can provide essential information about physical and geotechnical variations of sediment properties, which have the potential to contribute to engineering activities in subaqueous environments. Portable free fall penetrometers have been used for the rapid...

In fall 2017, a joint project by the Army Corps of Engineers and the Coastal Hydrodynamics and Sediment Dynamics lab at VIMS used laser diffraction particle size analysis (LDPSA) and pipette analysis, respectively, to determine the clay to silt ratio of sediment samples from dredging sites in the James River Estuary in Virginia. Ultimately, the cla...

Investigated the effects of inorganic-organic particle ballasting on water clarity, the transfer of organic matter to depth, and the spatial patterns of primary production using a Chesapeake Bay ROMS-based biogeochemical model.

Subtidal flows driven by density gradients affect the tide-averaged sediment transport in estuaries and, therefore, can influence their long-term morphodynamic evolution. The three-dimensional Coupled Ocean-Atmosphere-Wave-Sediment Transport modeling system is applied to numerically analyze the effects of baroclinicity and Earth's rotation on the l...

Low levels of dissolved oxygen (DO) occur in many embayments throughout the world and have numerous detrimental effects on biota. Although measurement of in situ DO is straightforward with modern instrumentation, quantifying the volume of water in a given embayment that is hypoxic (hypoxic volume (HV)) is a more difficult task; however, this inform...

Laboratory experiments were conducted to examine mobility and burial of objects, including onset of motion on a rigid bottom, scour burial into a sand bed, and the interplay between scour and motion onset. Experiments covered a range of object diameter-to-bottom roughness ratios (D/k) of relevance to mobility of unexploded ordnance (UXO). Results i...

Factors that influence equilibrium, scour-induced burial depth (B) in sand relative to object diameter (D) are examined through analysis of over 750 observations. The main factors that increase scour-induced B/D under steady currents without waves are found to be an increased Shields parameter () and small D (< 3 cm), with separate power laws appl...

The eastern oyster, Crassostrea virginica, is a prominent ecosystem engineer, whose reefs exhibit strikingly consistent morphologies at multiple spatial scales throughout its North American range. These distinct morphologies are thought to form by interactions of nascent reef structures with hydrodynamics. We carried out two field studies to determ...

As three-dimensional (3-D) aquatic ecosystem models are used more frequently for operational water quality forecasts and ecological management decisions, it is important to understand the relative strengths and limitations of existing 3-D models of varying spatial resolution and biogeochemical complexity. To this end, 2-year simulations of the Ches...

As three-dimensional (3-D) aquatic ecosystem models are becoming used more frequently for operational water quality forecasts and ecological management decisions, it is important to understand the relative strengths and limitations of existing 3-D models of varying spatial resolution and biogeochemical complexity. To this end, two-year simulations...

Recent advances in development of in situ video settling columns have significantly contributed toward fine-sediment dynamics research through concurrent measurement of suspended sediment floc size distributions and settling velocities, which together also allow inference of floc density. Along with image resolution and sizing, two additional chall...

The Community Sediment Transport Modeling System (CSTMS) cohesive bed sub-model that accounts for erosion, deposition, consolidation, and swelling was implemented in a three-dimensional domain to represent the York River estuary, Virginia. The objectives of this paper are to (1) describe the application of the three-dimensional hydrodynamic York Co...

Under conditions common in muddy coastal and estuarine environments, acoustic Doppler velocimeters (ADVs) can serve to estimate sediment settling velocity (w s) by assuming a balance between upward turbulent Reynolds flux and downward gravitational settling. Advantages of this method include simple instrument deployment, lack of flow disturbance, a...

[1] Strong and strategic collaborations among experts from academia, federal operational centers, and industry have been forged to create a U.S. IOOS Coastal and Ocean Modeling Testbed (COMT). The COMT mission is to accelerate the transition of scientific and technical advances from the coastal and ocean modeling research community to improved oper...

Sea-level rise has a strong influence on tidal systems, and a major focus of climate change effect studies is to predict the future state of these environmental systems. Here, we used a model to simulate the morphological evolution of tidal embayments and to explore their response to a rising sea level. The model was first used to reproduce the for...

The overall size of the "dead zone" within the main stem of the Chesapeake Bay and its tidal tributaries is quantified by the hypoxic volume (HV), the volume of water with dissolved oxygen (DO) less than 2 mg/L. To improve estimates of HV, DO was subsampled from the output of 3-D model hindcasts at times/locations matching the set of 2004-2005 stat...

Concentration of suspended sediment at 1-cm above the bed was determined by direct observation at three localities. Observations reflect approximately 6-wk time series obtained at 13-m depth off Duck, North Carolina, USA and at 15 and 20-m depth off Dounreay, Scotland, UK. The observations cover i) dynamic conditions ranging from predominantly wave...

The use of sound waves in oceanographic environments is well established including active sonar applications for mapping seafloors, for submarine detection, and for passive listening. Acoustic waves have been used for many years to study the ocean, including detecting and identifying objects in the water column, and the measuring the seafloor and s...

While the Acoustic Doppler Velocimeter (ADV) is designed to determine fluid velocity, it is important to recognize that it is actually the velocity of the scatterers themselves that is measured. Thus in a calibration tank designed to relate sediment-induced backscatter to sediment concentration, the vertical velocity registered by an ADV at a given...

The study of the morphology and evolution of tidal flats is particularly well suited in the context of morphodynamics in that characteristics such as profile shape, bed slope, and grain size clearly and systematically vary as a function of sediment supply and wave and tidal forcing, and the nature of wave- and tide-induced velocities across tidal f...

A 14-month time series of sediment cores from the bed of the York River estuary, Chesapeake Bay, USA, were sampled with a Gust erosion microcosm and further analyzed to evaluate variability in a variety of physical bed properties. Variation in sediment solids volume fraction did not relate to variability in bed erodibility. However, solids volume f...

A field experiment was conducted to quantify settling velocities, aggregate states, and flocculation within a hopper dredge plume. Particular interest was in determining the abundance of dense, bed aggregates suspended from the consolidated bed during dredging. A suspended sediment plume from the hopper dredge Essayons was sampled for a period of 9...

Observations are presented from a benthic observatory in the middle reaches of the York River estuary, VA, USA, that show evidence for both muddy flocs and pellets in the lower 1 m of the water column. This study combines in situ time series estimates of (i) volume concentration and particle size distribution from a Laser In Situ Scattering Transmi...

The Waiapu River sedimentary system, New Zealand, provides a prototype for investigating the relative importance of wave- versus current-supported gravity flows on continental shelf deposition. A two-dimensional model was used to represent gravity-driven sediment transport and deposition on the Waiapu shelf over an annual cycle of storm events and...

Submitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution, February, 1993 In this thesis, mechanisms which control morphodynamics of shallow tidal embayments are investigated analytically. In the process of exploring these mec...

Spatial trends in the shape of profiles of South San Francisco Bay (SSFB) tidal flats are examined using bathymetric and lidar data collected in 2004 and 2005. Eigenfunction analysis reveals a dominant mode of morphologic variability related to the degree of convexity or concavity in the cross-shore profile—indicative of (i) depositional, tidally d...