Hydrodynamics and sediment suspension in shallow tidal channels intersecting a tidal flat. (15th May 2016)

• Record Type: Journal Article
• Authors: Pieterse, Aline; Puleo, Jack A.; McKenna, Thomas E.
• Is Part Of: Continental shelf research. Volume 119(2016)
• Page Start: 40
• Page End: 55
• Publication Date: 2016-05-15
• Subjects: Tidal flat -- Tidal channel -- Hydrodynamics -- Velocity -- Shear stress -- Sediment suspension; Continental shelf -- Periodicals; Submarine geology -- Periodicals; 551.41
• DOI: 10.1016/j.csr.2016.03.012
• Languages: English
• ISSNs: 0278-4343

Abstract

Abstract: A field study was conducted on a tidal flat intersected by small tidal channels (depth <0.1 m, width <2 m) within a tidal marsh. Data were collected in the channels, and on the adjacent tidal flat that encompasses approximately 1600 m 2 in planform area. Hydrodynamic processes and sediment suspension between the channels and adjacent flat were compared. Shear stress and turbulent kinetic energy were computed from high frequency velocity measurements. Maximum water depth at the field site varied from 0.11 m during the lowest neap high tide to 0.58 m during a storm event. In the channel intersecting the tidal flat, the shear stress, turbulence and along-channel velocity were ebb dominant; e.g. 0.33 m/s peak velocity for ebb compared to 0.19 m/s peak velocity for flood. Distinct pulses in velocity occurred when the water level was near the tidal flat level. The velocity pulse during flood tide occurred at a higher water level than during ebb tide. No corresponding velocity pulse on the tidal flat was observed. Sediment concentrations peaked at the beginning and end of each tidal cycle, and often had a secondary peak close to high tide, assumed to be related to sediment advection. The influence of wind waves on bed shear stress and sediment suspension was negligible. Water levels were elevated during a storm event such that the tidal flat remained inundated for 4 tidal cycles. The water did not drain from the tidal flat into the channels during the storm, and no velocity pulses occurred. Along-channel velocities, turbulent kinetic energy, and shear stresses were therefore smaller in the channels during storm conditions than during non-storm conditions. Highlights: Near-bed velocities and sediment concentration were measured on a tidal flat. Pulses in velocity occurred in the channels as water levels passed tidal flat level. Shear stress and turbulence peaked in phase with velocity. Sediment concentration peaks were correlated poorly with local shear stress. Smaller stress and no velocity pulse occurred during 2 days of elevated water level.