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1978. M.Sc., 131 pp.

BLOWOUTS IN THE SAND DUNES OF WASAGA BEACH

 Arbour, J. H.

Arbour.jpg (10669 ×Ö½Ú)This thesis is an investigation into the blowouts found in a coastal barrier dune system at Wasaga Beach, Ontario, Canada. A multidisciplinary approach has been taken with the aim of describing the characteristics of the process which produces them.
      
The Wasaga Beach area was lumbered heavily during the latter part of the nineteenth century. The exposure of the dunes that resulted increased the potential for erosion in the dunes. The shapes, sizes and location of the blowouts indicated that most occur on moderate to steep slopes and are oriented in a NW/SE direction. Almost two-thirds of the blowouts are stable or in advanced stages of stabilization. The other one-third have suffered disturbance due to recreational activities.
      
Many of the stable blowouts occur in well treed areas (Pinus resinosa and Pinus strobus dominant). The leaf litter from these trees is forming an extensive covering on the sand enhancing its moisture holding capacity, and preventing sand movement. This leaf litter along with a pioneering moss is an important indicator of blowout stability.
      
Wind velocity measurements made in the field indicated a linear relationship between the shape of the blowout and the velocity change of the wind as it flows through the blowout. The slope of the surface was used as a shape factor and correlations were determined between the velocity change and the slope. Measurements in the field yielded correlation coefficients ranging from r = 0.66 to r = 0.74. Additional measurements in a wind tunnel using a scale model of the blowout yielded correlations ranging from r = 0.74 to r = 0.79. A relation between the wind velocity changes and the slope was inferred from these results. However there are other variables that affect the wind flow that were not taken into account, such as the amount of turbulence, the affect of small changes in wind direction and the variability of wind velocity.
      
These wind results are used to make estimations of sand movement rates and patterns in the blowouts. Field measurements indicate low net rates of sand movement in the blowouts. The calculations of sand movement based on work done by Bagnold (1941) in flume and in desert conditions produced higher rates of movement than the measurements indicated. The temperate climate and vegetative cover of the area can be attributed with causing this difference.

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