ASSESSMENT OF A GIS MODEL FOR THE IDENTIFICATION OF STREAM TERRACES AT THE HEADWATERS OF THE NEW RIVER, BLUE RIDGE PHYSIOGRAPHIC PROVINCE

Stream terraces represent past periods of landscape stability, however the mechanisms by which they form are variable, relating to stream capture or environmental change. These landforms are not commonly preserved in the Appalachian region due to high relief, narrow valleys, and active erosional processes. We have developed a GIS model for identifying stream terraces in the Blue Ridge through the geomorphometric analysis of a set of four cut-in-fill stream terraces located immediately upstream of the confluence of Roan Creek and the South Fork New River in the Jefferson 7.5’ quadrangle. The presence of alluvium was verified using shallow geophysical surveys. The characteristics of identified terraces are analyzed through remote sensing and GIS analysis. Of particular importance is the height of each terrace above the modern river level (ARL), which has been used to estimate relative age in other studies. We have developed a GIS method for measuring terrace height ARL. As a result, we identified two additional terraces and an abandoned river meander at the study site, four additional terrace sets in Ashe County, and a unique terrace (the “Piney Creek Terrace”) in Alleghany County. The “Piney Creek Terrace” is 121.3 meters above the modern river level and extends as far as 3 kilometers away from the New River. The terraces located in Ashe County are between 2 and 46 meters ARL. Our data indicate that the preservation of T0 and T1 terraces in Ashe County greatly exceeds that of any other terrace class. The preservation of T5 and T6 terraces is extremely rare, with only one T6 and two T5 terraces being identified in Ashe County. In addition there is a strong correlation between terrace class and distance from the river. Terrace area is independent of both terrace class and distance from the river. The distance of the Piney Creek Terrace from the New River and its greater height ARL in comparison to terraces identified further upstream, as well as the absence of terrace sequencing, indicates that the Piney Creek Terrace was likely formed through stream capture. The terraces upstream of the junction between the North and South Fork New River are likely formed by alternations in landscape stability due to long term environmental change.