Document Type

Thesis

Abstract

Concordant topographic highs within the central Virginia Piedmont suggest recent dissection of a once more continuous, low-relief surface. This interpretation is supported by documentation of recent (~1 Ma) acceleration in river incision and recognition of migrating knickzones along trunk rivers in the Virginia Piedmont. Taken together, these observations suggest a landscape in disequilibrium, with some portions of the landscape that have not yet responded to accelerations rates of fluvial incision. As fluvial knickzones migrate upstream, incision lowers the boundaries for the adjacent hillslopes, translating the wave of erosion to the surrounding landscape. Through a series of morphometric analyses in the James River system, we attempt to identify signatures of the “landscape knickzone” that represents the location of this wave of erosion in the nonfluvial portion of the landscape. Proposed characteristics of increased erosion in the landscape include steeper slopes, increased relief, and increased drainage density, all tending to promote increased landscape “roughness”. Landscape analyses were conducted on both topographic swaths through the entire James River watershed and on smaller topographic squares, located around possible migrating knickzones. Along the swaths identification of concordant summits and variations in relief and landscape roughness were assessed by statistical measures. Within the squares analyses of basin hypsometry, relief over multiple scales, and hillslope steepness were used to attempt to identify the position of the landscape knickzones as well as to confirm that the landscape is in disequilibrium. Identification of migrating knickzones and relief and slope patterns confirmed the interpretation of a Piedmont landscape in disequilibrium. No positive identification of the landscape knickzone was made.

Date Awarded

2007

Department

Geology

Advisor 1

Gregory S. Hancock

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