TY - JOUR
T1 - Three years of morphologic changes at a bowl blowout, Cape Cod, USA
AU - Smith, Alex
AU - Gares, Paul A.
AU - Wasklewicz, Thad
AU - Hesp, Patrick A.
AU - Walker, Ian
N1 - Funding Information:
This work was supported by National Science Foundation grants to P. Hesp and I. Walker (# 1024125) and to P. Gares (# 1024160), which facilitated this study. We are thankful to the Cape Cod National Seashore, particularly Dr. Megan Tyrrell and other staff at the Atlantic Research and Learning Center for facilitating access to study sites and encouraging our work. P. Hesp acknowledges the support of Louisiana State University and Flinders University. The East Carolina Division of Research and Graduate Studies has provided several grants to T. Wasklewicz to facilitate purchase and maintenance of the laser scanning equipment used in this project. The Terrain Analysis Lab at East Carolina University has also provided funds, equipment, software, office space, and data storage to this project. Finally, we thank the numerous students who provided field assistance: K. Reavis, M. Roman-Rivera, M. Haynes, K. Adams, D. Kirk, C. Chapman, K. Abhar.
Publisher Copyright:
© 2017
PY - 2017/10/15
Y1 - 2017/10/15
N2 - This study presents measurements of blowout topography obtained with annual terrestrial laser surveys carried out over a three-year period at a single, large bowl blowout located in the Provincelands Dunes section of Cape Cod National Seashore, in Massachusetts. The study blowout was selected because its axis is aligned with northwest winds that dominate the region, and because it was seemingly interacting with a smaller saucer blowout that had recently formed on the southern rim of the primary feature. Assuming that blowouts enlarge both horizontally and vertically in response to the wind regime, the objectives of the study were to determine both the amount of horizontal growth that the blowout experiences annually and the spatial patterns of vertical change that occur within the blowout. Changes to the blowout lobe surrounding the feature were also determined for areas with sparse enough vegetation cover to allow laser returns from the sand surface. The results show that the blowout consistently expanded outward during the three years, with the greatest expansion occurring at its southeast corner, opposite the prevailing winds. The most significant occurrence was the removal, in the first year, of the ridge that separated the two blowouts, resulting in a major horizontal shift of the southern rim of the new combined blowout. This displacement then continued at a lesser rate in subsequent years. The rim also shifted horizontally along the northwest to northeast sections of the blowout. Significant vertical loss occurred along the main axis of the blowout with the greatest loss concentrated along the southeast rim. On the lobe, there were large areas of deposition immediately downwind of the high erosion zones inside the blowout. However, there were also small erosion areas on the lobe, extending downwind from eroding sections of the rim. This study shows that: 1. blowouts can experience significant areal and volumetric changes in short periods of time; 2. significant changes may occur relatively suddenly when adjacent blowouts combine into a single feature; and 3. the sediment transport paths are highly controlled by the topography. The joining of two blowouts not only creates a new larger feature, but it also releases large amounts of sediment that are then distributed across the landscape downwind, creating a potential for major changes to a landscape over the longer term.
AB - This study presents measurements of blowout topography obtained with annual terrestrial laser surveys carried out over a three-year period at a single, large bowl blowout located in the Provincelands Dunes section of Cape Cod National Seashore, in Massachusetts. The study blowout was selected because its axis is aligned with northwest winds that dominate the region, and because it was seemingly interacting with a smaller saucer blowout that had recently formed on the southern rim of the primary feature. Assuming that blowouts enlarge both horizontally and vertically in response to the wind regime, the objectives of the study were to determine both the amount of horizontal growth that the blowout experiences annually and the spatial patterns of vertical change that occur within the blowout. Changes to the blowout lobe surrounding the feature were also determined for areas with sparse enough vegetation cover to allow laser returns from the sand surface. The results show that the blowout consistently expanded outward during the three years, with the greatest expansion occurring at its southeast corner, opposite the prevailing winds. The most significant occurrence was the removal, in the first year, of the ridge that separated the two blowouts, resulting in a major horizontal shift of the southern rim of the new combined blowout. This displacement then continued at a lesser rate in subsequent years. The rim also shifted horizontally along the northwest to northeast sections of the blowout. Significant vertical loss occurred along the main axis of the blowout with the greatest loss concentrated along the southeast rim. On the lobe, there were large areas of deposition immediately downwind of the high erosion zones inside the blowout. However, there were also small erosion areas on the lobe, extending downwind from eroding sections of the rim. This study shows that: 1. blowouts can experience significant areal and volumetric changes in short periods of time; 2. significant changes may occur relatively suddenly when adjacent blowouts combine into a single feature; and 3. the sediment transport paths are highly controlled by the topography. The joining of two blowouts not only creates a new larger feature, but it also releases large amounts of sediment that are then distributed across the landscape downwind, creating a potential for major changes to a landscape over the longer term.
KW - Airflow
KW - Blowout
KW - Lobe deposition
KW - Rim expansion
KW - Terrestrial laser scanning
KW - Wind events
UR - http://www.scopus.com/inward/record.url?scp=85026759841&partnerID=8YFLogxK
UR - http://www.scopus.com/inward/citedby.url?scp=85026759841&partnerID=8YFLogxK
U2 - 10.1016/j.geomorph.2017.07.012
DO - 10.1016/j.geomorph.2017.07.012
M3 - Article
AN - SCOPUS:85026759841
SN - 0169-555X
VL - 295
SP - 452
EP - 466
JO - Geomorphology
JF - Geomorphology
ER -