Evaluating the Capabilities of the Second Generation PICS Settling Column Floc Camera in a Muddy Tidal Estuary, York River, Virginia, USA Grace M. Cartwright, S. Jarrell Smith, Carl T. Friedrichs, and Kelsey A. Fall US Army Corps of Engineers Engineer Research and Development Center Waterways Experiment Station Vicksburg, MS

Independent verification Acoustic Doppler Velocimeter (ADV) Method Bulk Settling Velocity (Ws) of suspended sediment is burst averaged concentration from calibrated ADV backscatter is burst averaged Turbulent Reynold’s Flux C background is the lowest concentration observed during the study period Motivation ADV Concentration (mg/L) Bulk (Dickhudt et al, 2009; Cartwright et al, 2011; Fugate and Friedrichs, 2002) An Example Set of Bursts (mm/s)(mg/L) Bulk Settling Velocities for MUDBED Tripod Deployments

PICS – Particle Imaging Camera System camera Laser source settling column Laser source Side View Top View Current 1mm light sheet 10 x 14 mm (Smith- INTERCOH 2012)

Example PICS Video Sequence (1 m depth) Fluid Velocity hinders sediment settling 10/06/ :06:00 (frames ) collected at 8 frames/sec

PTV/PIV method to remove fluid velocity effects PTV: Particle Tracking Velocity individual particles ≥ 30 μm (3 pixels) PIV: Particle Image Velocity groups of particles ≤20 μm (2 pixels) Fluid velocities estimated for each cell from one frame to the next Peak velocity used for each cell Particles are tracked from frame to frame A Thread is a particle tracked for at least 5 frames (Smith and Friedrichs, 2012;Van Leussen and Cornelisse, 1993; Fennessy et al, 1994)

PTV/PIV method to estimate Ws, ρ s and mass (Smith and Friedrichs, 2012; Oseen, 1927; Schiller and Naumann, 1933; Soulsby, 1997,) Calculated as the net of the Particle and fluid velocity vectors Averaged for all the frames in the track Split into 3 classes: Density 1. primary > 1800 kg/m 3 2. bed aggregate kg/m 3 3. flocculants < 1150 kg/m 3 Particle Density

Study Site NSF MUltiDisiplinary Benthic Exchange Dynamics Clay Bank area on York River Chesapeake Bay, VA Micro tidal ( 0.7 to 1 meter) Secondary Channel ~ 5 meter depth Seabed During Neap >75% mud ~10% Organics Sand D50 ~100 µm up to 30% Pellets (~60-90 μm) Kraatz, (2010, personal comm), Rodriguez-Calderon (2010)

Study Period October 6, days before Neap Slack-Slack bracket Flood (~6 hrs) Each Sample PICS Turbulence dissipate sec Collect 30 sec 8 frames/sec Collect second burst ~1 min later ADV 2 minute 10 Hz LISST 2 minute 2/3 Hz CTD 2 minute 1 Hz Pump Samples 1 sample right away 2 nd sample mid CTD burst Every Hour Water column “cast” 5-6 samples (~1/m) Bottom samples every min (Picture from Smith and Friedrichs, 2010) Two Grab Samples of Bottom Sediment

Depth 5.8 m Number particles 400 d 50,p = 54.7 μm d 50,m = 68.1 μm ws 50,p = mm\sec ws 50,m = mm\sec By particle count Flocs: 75.5 % Bed Agg: 24.5 % Primary: 0.0 % By mass Flocs: 78.0 % Bed Agg: 22.0 % Primary: 0.0 % seq 08:47:03 Example PICS Results 3 classes: Density 1. primary > 1800 kg/m 3 2. bed aggregate kg/m 3 3. flocculants < 1150 kg/m 3

Preliminary Results Concentrating on bottom samples only

Water Velocity from ADV

% >60 μm (by weight) from Pump Sample SPM % SPM > 60 μm

50 percentile grain-size from PICS For each sample sec bursts approximately 1 minute apart

50 percentile settling velocity from PICS For each sample sec bursts approximately 1 minute apart

Bulk settling velocity from PICS and ADV For each PICS sample sec bursts approximately 1 minute apart

Future Work (Figure from Smith and Friedrichs, 2010) Work up LISST data Process the bottom sediment Repeat Study for Spring Tide PICS lab experiment to find Ws for isolated fecal pellets