Morphological and sedimentological responses of streams to human impact in the southern Blue Ridge Mountains, USA

Abstract

Morphological and sedimentological responses of streams to basin-scale impact have been well documented for intensively agricultural or urban areas. Sensitivity thresholds of streams to modest levels of disturbance, however, are not well understood. This study addresses the influence of forest conversion on streams of the southern Blue Ridge Mountains, a region that has received little attention with respect to human impact on stream channels. Basins were chosen for this study to represent the end members of the range of human impact in the area, with the forest cover of the basin used as a proxy for level of impact (ranging from about 70- 100% regionally). Two pairs of lightly impacted (>go% forest) and moderately impacted (70-80% forest) sub-basins of the upper Little Tennessee River were identified for comparison. Reach characteristics (e.g., slope, drainage area, and riparian cover) were aligned in each pair to isolate contrasting forest cover as the primary driver of any detected differences in morphology and sedimentology. A suite of standard cross-sectional and longitudinal data was collected for each reach for characterization of the sedimentology and morphology of the streams. Difference of means tests were conducted to identify parameters significantly differing between the lightly and moderately impacted streams in both pairs. Consistent and significant differences within both pairs were demonstrated in bankfull width/depth ratios, baseflow wetted width, and particle size on the stream bed both in the thalweg and throughout the channel bed. The moderately impacted streams are narrower than the lightly impacted streams, and the bed texture of the moderately impacted streams is finer than that of the lightly impacted streams. The moderately impacted streams contain a higher percentage of

Citation

Price, Katie; Leigh, David S. 2006. Morphological and sedimentological responses of streams to human impact in the southern Blue Ridge Mountains, USA. Geomorphology, Vol. 78: 142-160