Fluvial Response to Land-Use Change in The Southern Appalachian Region: A Century of Investigation

Anthropic signatures in alluvium of the Upper Little Tennessee River valley, Southern Blue Ridge Mountains, USA

“…Meanwhile, agricultural practices in lower valleys currently emphasize livestock over growing row crops (Harden, 2004). These human activities led to accelerated soil erosion and hillslope failures, which provided substantial amounts of sediments to floodplains (Leigh and Webb, 2006;Knox, 2006;Leigh, 2016), leading to the significant increases of our observed post-settlement sedimentation rates.…”

“…AD 1870 (Leigh, 2010(Leigh, , 2016, as commercial timber harvest moved into the region. A detailed land use history over the past centuries in the region is described by Yarnell (1998) and Harden (2004) with the most notable features being extensive and intensive timber harvest that peaked in the early 20 th century, reforestation throughout the region since the 1940s, and vacation home development on hillslopes since the 1970s that has stimulated sustained erosional disturbance. Currently, the land cover classes within the catchment include, forest (79.5 %), pasture-grasses-shrubs (11.9 %), developed (7.9%), cultivated (0.4%), and others (0.3 %), according to the latest (2011) land cover data set (Homer et al, 2015 (Fig.…”

“…Clear-cutting for timber harvest was intensive, and widespread row-crop agriculture also occurred in the late 19th and early 20th century (Yarnell, 1998;Harden, 2004), causing soil erosion on upland slopes and accelerated sedimentation in lower valleys, as noted by Glenn (1911). The federal acquisition of Appalachian land in 1911 and later established national forests and regulated logging activities (Yarnell, 1998;Harden, 2004), but human disturbance on private land persisted in the form of forest clearing, agriculture, urbanization, and road construction (Price and Leigh, 2006;Kirk et al, 2012). Especially since the 1970s, as more people migrated to this area, second-homes and roads have been built on sloping portions of the basin (Leigh, 2007;Kirk et al, 2012).…”

Managing for large wood and beaver dams in stream corridors

“…Logging operations relied heavily on transport of cut logs in streams, resulting in widespread removal of naturally occurring instream large wood, simplification of channel geometry, and reduction of channel-floodplain connectivity to facilitate downstream movement of logs. Commercial, mechanized logging during the early 20th century involved clearcutting and an increase in fire frequency (Villarrubia 1982;Harden 2004). Consequently, even areas currently managed as wilderness are likely to be depleted in very large, old trees and instream large wood as a result of the legacy of past land use.…”

Modeling stream-bank erosion in the Southern Blue Ridge Mountains

“…In the southern Appalachians, a large amount of sediment was eroded in response to late 19th and early 20th century timber harvests and is stored within historical terraces in the smaller tributaries (Leigh, 2010). Currently, these deposits act as an important sediment source for locations downstream and within the associated watershed (Harden, 2004;Leigh, 2010). It is well known that large sediment inputs from relatively discrete events (i.e., timber harvests) in watersheds have lag and residence times that are critical to fluvial processes and geomorphic form (Kelsey 1982;Madej & Ozaki, 1996;Montgomery, 1999;Swank, Vose, & Elliott, 2001).…”