From the sand bed to the free surface: an experimental study of wave-induced sediment transport over a sandbar
Abstract
Considerable progress has been made in predicting surf zone sandbar migration. Yet present-day models require extensive calibration to predict cross-shore morphologic evolution. Interaction between important physical processes, such as sheet flow and suspended load, under skewed-asymmetric waves may be improperly parameterized or neglected entirely due to lack of measurements. A large wave flume experiment was conducted at Oregon State University's O.H. Hinsdale Wave Research Laboratory to examine the relative contributions of suspended load and sheet load to the total transport rate over sandbars, using a fixed, barred beach profile with a mobile sediment layer on the sandbar crest. The hybrid beach profile allowed for the isolation of small-scale bed response to large-scale wave forcing over an immobile sandbar, where an array of sensors was positioned to measure hydrodynamic forcing and sediment response. Monochromatic waves were tested under a wide range of wave skewness and asymmetry parameters typically associated with accretive or erosive conditions. Measured sediment concentration profiles in the sheet flow layer and lower half of the water column were combined and then extrapolated to the free surface to determine the overall sediment load. Total load sediment transport rates were computed by multiplying this concentration profile by measured near-bed velocity profiles and velocities recorded throughout the water column. The relative contribution of each sediment transport regime to the total was then determined by integrating across phase-averaged transport rates for each wave condition. The result is a per-wave total volume of sediment transported over a sandbar per meter of beach width via sheet flow and suspended load under waves with varying degrees of skewness and asymmetry.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2016
- Bibcode:
- 2016AGUFMOS23B2039M
- Keywords:
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- 4544 Internal and inertial waves;
- OCEANOGRAPHY: PHYSICALDE: 4546 Nearshore processes;
- OCEANOGRAPHY: PHYSICALDE: 4558 Sediment transport;
- OCEANOGRAPHY: PHYSICALDE: 4560 Surface waves and tides;
- OCEANOGRAPHY: PHYSICAL