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Title: Bed form development and distribution pattern, Parker and Essex estuaries, Massachusetts
Authors: Boothroyd, J. C.
Hubbard, Dennis K.
Keywords: Estuaries--Massachusetts--Parker River--Essex estuary
River channels
Sand waves
Publisher: Coastal Engineering Research Center (U.S.)
Engineer Research and Development Center (U.S.)
Series/Report no.: Miscellaneous Paper;no. 1-74
Abstract: Abstract: Velocity, depth, temperature, grain size, and bed form scale and orientation were measured for complete tidal cycles at 50 stations in two New England estuaries. Scuba observation of bed form change and migration, fathometer profiles, and 700 bed form scale and orientation readings were also carried out. This investigation led to the recognition of a sequence of bed forms based on increasing "flow strength." Bed form type is governed by maximum flood and ebb velocities (Umax) attained at a given locality. Velocity asymmetry and duration are important in determining bed form morphology and amount of crossbedding bimodality. Froude number (Fr) shows good correlation with bed form type only in depths less than 2 meters. In the intertidal and shallow subtidal (<2 meters MLW) zone, sand waves are characterized by Umax 80 centimeters per second, large velocity asymmetry (Fr = 0.15-0.25), planar crossbedding, little crossbedding bimodality, and dominant flood orientation. Cuspate megaripples are characterized by Umax 80 centimeters per second, small velocity asymmetry (Fr = 0.25-0.4), festoon crossbedding, high crossbed bimodality, and no dominant orientation. In deep subtidal (>2 meters MLW) areas, sand waves are the principal bed form. They show no dominant orientation. However, where Umax exceeds 80 centimeters per second, megaripples are superimposed on the sand wave form and crossbedding is complex.
Description: Miscellaneous Paper
Rights: Approved for public release; distribution is unlimited.
Appears in Collections:Miscellaneous Paper

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