Regional scale sandbar variability : observations from the U.S. Pacific Northwest Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/8g84mp31v

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  • Understanding sandbar dynamics and variability is integral to developing a predictive capacity for nearshore flows, sediment transport, morphological change, and ultimately for determining coastline exposure to damaging storm waves. Along the high-energy U.S. Pacific Northwest (PNW) coast, sandbars typically dominate the bathymetry of the active zone. Here we report on a nearshore bathymetric data set that covers an exceptionally long stretch of coast and crosses several littoral cell boundaries. Our study area stretches from Point Grenville, Washington to Cascade Head, Oregon, including 8 littoral cells and approximately 250 km in the alongshore. We describe and quantify the morphological variability of sandbars in the PNW over large spatial scales as well as attempt to explain the inter-littoral cell variability via trends and variability in environmental parameters. From 560 bathymetric profiles (~1000 km of measurements) we have extracted over 500 distinct subtidal sandbars. The bar zone extends to over 1km from the shoreline in the northern part of the study area, but only to about 600m in the southern part. Maximum bar crest depths are typically 7m below MLLW. Bar heights range from a step in the cross-shore profile to over 3m from crest to trough. The northernmost littoral cells typically have two or more bars per cross-shore profile whereas the littoral cells in the southern part of our study area have only one bar. The mean depths of the bars, however, are much more consistent across littoral cells. The mean depths remain consistent even while the upper shoreface slope significantly increases from north to south, requiring that the maximum bar distance from the shoreline decreases from north to south. This regional gradient in upper shoreface slope is likely a response, at least in part, to a general coarsening trend in the sediment from north to south and hence linked to variations in regional geology.
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  • description.provenance : Approved for entry into archive by Julie Kurtz(julie.kurtz@oregonstate.edu) on 2013-01-04T22:49:47Z (GMT) No. of bitstreams: 1 Di Leonardo Thesis - Final Draft2.pdf: 3666607 bytes, checksum: b9db7d91abca1dada7deeb370e31defc (MD5)
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  • description.provenance : Submitted by Diana Di Leonardo (dileonad@onid.orst.edu) on 2013-01-04T19:05:41Z No. of bitstreams: 1 Di Leonardo Thesis - Final Draft2.pdf: 3666607 bytes, checksum: b9db7d91abca1dada7deeb370e31defc (MD5)
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