A5037232976- Coastal and Marine Dynamics
- Geological formations and processes
- Coastal wetland ecosystem dynamics
- Hydrology and Sediment Transport Processes
- Aeolian processes and effects
- Underwater Acoustics Research
- Landslides and related hazards
- Granular flow and fluidized beds
- Ocean Waves and Remote Sensing
- Soil erosion and sediment transport
- Tropical and Extratropical Cyclones Research
- Particle Dynamics in Fluid Flows
- Oceanographic and Atmospheric Processes
- Hydrology and Watershed Management Studies
- Water Quality and Resources Studies
- Geology and Paleoclimatology Research
- Geophysical Methods and Applications
- Flood Risk Assessment and Management
- Soil Mechanics and Vehicle Dynamics
- Fluid Dynamics and Turbulent Flows
- Soil and Unsaturated Flow
- Water Quality Monitoring Technologies
- Wave and Wind Energy Systems
- Geotechnical Engineering and Soil Mechanics
- Geological Modeling and Analysis
Saint Louis University
2011-2025
United States Geological Survey
2003-2011
Pacific Science Center
2003-2010
The Milton H. Erickson Foundation
2009
Clarkson University
2009
University of Florida
1995-2006
National Oceanic and Atmospheric Administration
2006
California State University, Monterey Bay
2006
United States Army Corps of Engineers
2006
Harbor Branch Oceanographic Institute
1995-1997
The rapid shearing of a mixture cohesionless glass spheres and air or water was studied in an annular, parallel-plate shear cell designed after Savage (1978). Two types flow were observed. In the first type entire mass granular material mobilized. At high rates normal stresses found to be quadratically dependent upon mean rate (at constant volume concentration), general agreement with observations Bagnold (1954) & Sayed (1984), ‘kinetic’ theory Jenkins (1983). weakly on concentration up...
Flooding is a major disturbance that impacts aquatic ecosystems and the ecosystem services they provide. Predicted increases in global flood risk due to land use change water cycle intensification will likely only increase frequency severity of these impacts. Extreme flooding events can cause loss life significant destruction property infrastructure, effects are easily recognized frequently reported media. However, also has many other on people through freshwater services, which often go...
We consider a sheet flow in which heavy grains near packed bed interact with unidirectional turbulent shear of fluid. focus on flows the particles are supported by their collisional interactions rather than velocity fluctuations fluid and introduce what we believe to be simplest theory for regime that captures its essential features. employ relatively simple model shearing use kinetic grain predict profiles mean velocity, particle concentration, strength within sheet. These obtained as...
A two‐phase model is implemented to study the effects of wave shape on transport coarse‐grained sediment in sheet flow regime. The based balance equations for average mass, momentum, and fluctuation energy both fluid phases. Model simulations indicate that responses flow, such as velocity profiles, instantaneous bed shear stress, flux, total amount mobilized sediment, cannot be fully parameterized by quasi‐steady free‐stream may correlated with magnitude local horizontal pressure gradient...
For the first time, detailed measurements of sediment concentrations and grain velocities inside sheet flow layer under prototype surface gravity waves have been carried out in combination with suspension processes above layer. Experiments were performed a large‐scale wave flume using natural sand. Sand transport high shallow water is mainly contained within so‐called “sheet layer,” thin (10–60 diameters) which volume concentration sand decreases by an order magnitude from value near 0.6 at...
A field of giant sand waves, among the largest in world, recently was mapped high resolution for first time during a multibeam survey 2004 and 2005 through strait Golden Gate at mouth San Francisco Bay California (Figure la). This massive bed form covers an area approximately four square kilometers water depths ranging from 30 to 106 meters, featuring more than 40 distinct waves with crests aligned perpendicular dominant tidally generated cross‐shore currents, wavelengths heights that...
The mechanics of collisional grain flows are applied to the intense bed‐load transport sediment. velocity distribution and determined analytically without any freely adjustable parameters. flow is modeled as two fluid regions with continuous stress, velocity, granular concentration overlying a stationary bed: collision‐dominated granular‐fluid region wall‐bounded turbulent‐fluid shear saltating grains. A simple kinematic model for saltation grains developed predict in zone provide upper...
In this paper we present a detailed comparison between measured features of the Golden Gate sand wave field and results nonlinear model. Because waves exhibit large variation in their characteristics environmental physics, area gives us opportunity to study locations, within one well‐measured, area. The model used is presently only tool that provides information on evolution large‐amplitude waves. increase our understanding coupling variability conditions characteristics. Results show able...
High-resolution bathymetric surveys are interpreted to describe the morphology and movement of a field sand waves near San Francisco, CA, USA. The wave size, shape, orientation, migration described. Portions nearly two dimensional, but overall is three with changes in structure. trough-to-crest height individual ranges from 2 9 m. There range wavelengths orientations. dominant wavelength 90 100 m, orientation clusters around directions: 40 68 degrees. found be highly dynamic stable...
A recently developed acoustic multiple transducer array was utilized to measure small‐scale bed forms in the nearshore and inner shelf regions at Duck, North Carolina. Two populations of wave‐formed ripples were observed: short wave (SWR) with heights ranging from 3 mm 2 cm lengths 4 25 long (LWR) 6 35 200 cm. The SWR only present sometimes, their presence or absence determined by a critical value near‐bed mobility number. highly dynamic, sometimes flattening during groups reforming over...
Suspended sediment concentrations and fluid velocities measured in the swash zone of a high‐energy steep beach were used to investigate importance accelerations suspended transport. Swash flow acceleration was nearly constant at about one‐half downslope gravitational with two important exceptions. We observed strong, short‐lived periods accelerating uprush beginning cycle decelerating backwash end (magnitudes both approximately twice that expected acceleration). Interestingly, spikes load...
A 3 MHz acoustic concentration meter (ACM) was deployed with electromagnetic flowmeters in the nearshore region October 1984 at Stanhope Lane, Prince Edward Island, Canada, as a component of Canadian Coastal Sediment Study. The ACM measured backscatter energy vertical beam pattern within approximately 1 m seabed. Laboratory calibration experiments were conducted to verify method for converting into suspended sand profiles. functioned well when there no air bubbles water. Both profiles and...
Data obtained in an annular shear cell are interpreted to evaluate a dynamic Coulomb yield criterion at the boundary separating flowing and stationary grains steady granular fluid flow. The ratio of stress normal is nearly constant depth no motion, suggesting balance between mobilizing effect applied stabilizing which results from immersed weight moving grains. We suggest that can be predict undergoing bed load transport.
Sediment transport under nonlinear waves in a predominately sheet flow condition is investigated using two‐phase model. Specifically, we study the relative importance between waveshape and boundary layer streaming on cross‐shore sand transport. Terms governing equations because of process are included this one‐dimensional vertical (1DV) model by simplifying two‐dimensional (2DV) ensemble‐averaged with assumption that propagate without changing their form. The first driven measured time...
Field observations of the suspension sand near seabed under shoaled waves in nearshore region are presented and discussed with regard to influence wave groups. Sand is found be suspended at both incident frequency lower frequencies corresponding These limited indicate likelihood that groups result higher concentrations than randomly distributed similar heights.