HR: 1300h
AN: OS52B-21    [PDF]
TI: Bedform Migration and Bed Envelope Statistics
AU: * Gallagher, E L
EM: edith.gallagher@fandm.edu
AF: Franklin and Marshall College, PO Box 3003 , Lancaster, PA 17604-3003 United States
AU: Holman, R
EM: holman@coas.oregonstate.edu
AF: Oregon State University, COAS-OSU 104 Ocean Admin Bldg, Corvallis, OR 97331-5503 United States
AB: The generation and migration of bedforms (ripples, megaripples and sand bars) on sandy bottoms in the nearshore (0-8 m water depths) provides a mechanism whereby objects on the seafloor can become buried. As a bedform migrates past an object, the object will fall to the low point of the bedform trough and be buried by the passage of the following bedform crest. Existing data sets are being used to examine the statistics of spatial and temporal bed variability. Specifically, the evolution of the bottom profile envelope and the likelihood of burial after a given amount of time are being investigated. The maximum envelope thickness, Dmax, is defined as the difference between the maximum and minimum extent of the bed during a given time window (4, 6, 8, 10, 12, 14 and 16 day-windows are used in this study). Dmax is observed to grow in time and although preliminary results suggest linear growth, the inclusion of longer time series may support the hypothesis that Dmax would grow as an exponential taper (quickly at first, then slowing and approaching an asymptotic value). Both megaripples and larger-scale morphological changes (eg, bar migration) effect Dmax, with megaripples creating envelopes less than 50 cm and bar-scale erosion and accretion generating envelopes that are typically larger that 50 cm. When the instantaneous elevation of the seafloor above envelope minimum, D, exceeds W, the vertical scale of an object, the object will be buried. The likelihood of burial after a set amount of time is being examined by looking at D-W at the end of set time windows. Percent burial is shown to increase with time and to decrease in deeper water.
DE: 3020 Littoral processes
DE: 3022 Marine sediments--processes and transport
DE: 3045 Seafloor morphology and bottom photography
DE: 4546 Nearshore processes
DE: 4558 Sediment transport
SC: Ocean Sciences [OS]
MN: 2004 Ocean Sciences Meeting