Development of Saucer Blowouts and their role in Dune Field Evolution

Authors: Paul Gares*, East Carolina University, Thad Wasklewicz, East Carolina University, Patrick Hesp, Flinders University, Ian Walker, Arizona State University
Topics: Coastal and Marine, Geomorphology
Keywords: coastal dunes, blowouts, topographic change
Session Type: Paper
Day: 4/10/2018
Start / End Time: 2:40 PM / 4:20 PM
Room: Oakley, Sheraton, 4th Floor
Presentation File: No File Uploaded

Saucer blowouts have been observed in a variety of locations and environments but, of the few studies that have observed their long-term evolution, most rely on aerial photography to chronicle the changes. This study follows the development of 5 saucer blowouts located in the Provincelands dunes section of Cape Cod National Seashore over a period of 5 years. At this site, this type of blowout develops just landward of the crest of large dune ridges or of large trough blowouts. Changes to the blowouts have been determined by using laser scanning generally carried out in the fall and late spring of each year from 2011 to 2016. Visual observation of the saucers reveals that they expand rapidly both horizontally and vertically, which eventually results in ridge breaching and expansion of the blowout into full trough or saucer forms. Laser scanning surveys have quantified the rate of ridge crest retreat and lowering that takes place prior to complete ridge breaching. The high-resolution topographic data also provide an extremely accurate measure of volumetric change both within the potholes themselves and on the blowout lobes located in a downwind direction. This study provides information about the role that these features in the overall modification of the larger dune landscape. Changes in the areas of saucer blowout development can be compared to those that take place in places without saucers and this establishes the importance of this mechanism in the overall development of large dunefields.

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