Document Type

Thesis

Abstract

Research at Back Bay National Wildlife Refuge, Sandbridge, Virginia investigated the behavior of sand dunes near a breach in the large foredune. Breaches in the foredune similar to the breach at the study site are forming in many places along the foredune at Back Bay National Wildlife Refuge. It is important that the refuge preserve a variety of coastal environments for wildlife, and therefore, research on the impact of the breaches on sand dunes and the surrounding areas is important. Aerial photographs, sand traps, and sand elevation markers showed the changes in the sizes and shapes of dunes, the amount of sand movement across their surfaces, and the migration rates of mobile dunes near the breach. Aerial photographs from 1953, 1970, 1990, and 1994 showed that the dunes in the study site have been migrating and changing shape during the last fifty years. In 1953, parabolic dunes were inland of a low, discontinuous foredune. By 1970, the foredune was larger and more continuous, and linear shore parallel dunes and medano dunes had formed to the west. By 1990, the foredune was eroded and breached. The shore parallel dunes were shorter, and transverse dunes oriented east-west were forming to the south of the shore parallel dunes. By 1994, more erosion had affected the foredune, and the breach had widened. The transverse dunes had grown and the shore parallel dunes had experienced more erosion. Sand trap measurements indicated that the average sand flux on the dunes is 42 cm?/day. Repeat measurements from Nov 4, 1999 to March 18, 2000 of sand elevation markers at various points on the dunes using showed as much as 125 cm of aggradation on the two transverse dunes, and erosion on three shore parallel dunes. Sand elevation markers on the borders of the transverse dunes indicated an average migration rate of 5.2 m/year.

Date Awarded

2000

Department

Geology

Advisor 1

Heather MacDonald

Advisor 2

Gregory S. Hancock

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