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

Wang, Lixin; Leigh, David S.

doi:10.1016/j.ancene.2015.11.005

Cited by 7 publications

(6 citation statements)

References 61 publications

(92 reference statements)

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“…Errors in OSL dates were comparable (~10%, e.g., refs. 43 , 44 ), and the same 25% error level was applied to these data. Rates determined using 137 Cs, archeological finds and stratigraphic markers rely on accurate assignment of markers to specific historical dates.…”

Section: Methodsmentioning

confidence: 99%

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The human impact on North American erosion, sediment transfer, and storage in a geologic context

2020

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Humans are primary agents of geomorphic change, and rates of anthropogenic landscape change likely far exceed the pace of change expected from natural geologic processes. Nevertheless, our understanding of the impact of humans on the natural landscape is limited by difficulties in accurately comparing past and present rates of change across wide spatial and temporal scales. Here, we present a compilation of >4000 rates of alluvial sediment accumulation that provide an indirect record of North American erosion, mass transfer and sediment storage from the late Pleistocene to the present day. Continent-wide rates of alluvium accumulation were broadly stable for ~40,000 years, but increased 10-fold during the rapid expansion of agriculture and river system modification associated with European colonization. Interpreted in terms of mass transfer, humans have moved as much sediment in North America in the past century as natural processes can transfer in 700–3000 years.

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Section: Methodsmentioning

confidence: 99%

“…Most of the data associated with these methods have an upper date at the sediment surface, and errors were set at 15% (e.g., ref. 44 ). Dendrochronology dates have the potential to be highly accurate 40 but a conservative approach was adopted and these were also simulated with 15% error to reflect possible tree ring counting errors.…”

Section: Methodsmentioning

confidence: 99%

The human impact on North American erosion, sediment transfer, and storage in a geologic context

2020

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“…The Atlantic Multidecadal Oscillation (AMO), however, does influence streamflow of the lower Mississippi River (Enfield et al., 2001; Munoz et al., 2018), and a persistent cool phase of the AMO during the LIA (Mann et al., 2009) may account for the increased fluvial activity in the southeastern United States (Engstrom and Waylen, 2018). The warmer MCA was characterized by frequent extreme floods in paleoflood chronologies (Daniels and Knox, 2005; Harden et al., 2015), but a decline in extreme flood frequency in others (Munoz et al., 2015; Wang and Leigh, 2015). The lack of a cohesive regional fluvial response in the regional watershed chronologies during the MCA implies that fluvial activity was more localized at this time.…”

Section: Resultsmentioning

confidence: 99%

Fluvial activity in major river basins of the eastern United States during the Holocene

et al. 2020

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In the eastern United States, existing paleo-reconstructions in fluvial environments consist primarily of site-specific investigations of climate and human impacts on riverine processes. This paper presents the first meta-analysis of fluvial reconstructions focused on regional watersheds of the eastern United States, including the Lower Mississippi, Tennessee, South Atlantic–Gulf Coast, Ohio, Mid-Atlantic, and New England regional watersheds. Chronologies of fluvial activity (i.e. alluvial deposition) and stability (i.e. landscape stability) were developed by synthesizing data from existing, published, and site-specific fluvial reconstruction studies conducted across the eastern United States. Overall, regional watersheds show variable patterns of synchronicity across watersheds and did not demonstrate cyclic behavior through the Holocene. During the last millennium, only the Lower Mississippi and Ohio regional watersheds exhibit high rates of fluvial activity active during the ‘Medieval Climate Anomaly’ (650–1050 yr BP), while nearly all other regional watersheds in the eastern United States were active during the ‘Little Ice Age’ (100–500 yr BP). These findings imply that fluvial activity may be more spatially restricted during warmer/drier climatic conditions than during cooler/wetter periods. We find an increase in fluvial activity during the era of Euro-American colonization (400 yr BP to present) in the southeastern United States but not the northeastern United States, implying a heterogeneous response of fluvial systems to human activities in the eastern United States related to climatic, cultural, and/or physiographic variability. These new insights gained from fluvial chronologies in the eastern United States demonstrate the utility of regionally synthesized paleo-records to understand large-scale climate variation effect on rivers.

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“…The thick forest mantle remained intact through to the late nineteenth century, when a short period of clearfelling and selective logging occurred on Coweeta's hillslopes before establishment of the Hydrologic Laboratory in 1934 (Douglass & Hoover, 1988). An increase in sedimentation rates have been recorded in alluvium in the area (Wang & Leigh, 2015), but without producing an obvious increase in landsliding rates (Eschner & Patric, 1982;Parker et al, 2016). The short period of increased sediment flux is unlikely to have significantly affected hillslope morphology.…”

Section: 1029/2017jf004453mentioning

confidence: 99%

Controls on Zero‐Order Basin Morphology

et al. 2018

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Zero‐order basins are common features of soil‐mantled landscapes, defined as unchanneled basins at the head of a drainage network. Their geometry and volume control how quickly sediment may reaccumulate after landslide evacuation and, more broadly, zero order basins govern the movement of water and sediment from hillslopes to the fluvial network. They also deliver water and sediment to the uppermost portions of the fluvial network. Despite this role as the moderator between hillslope and fluvial processes, little analysis on their morphology has been conducted at the landscape scale. We present a method to identify zero‐order basins in landscapes and subsequently quantify their geometric properties using elliptical Fourier analysis. We deploy this method across the Coweeta Hydrologic Laboratory, USA. Properties such as length, relief, width, and concavity follow distinct probability distributions, which may serve as a basis for testing predictions of future landscape evolution models. Surprisingly, in a landscape with an orographic precipitation gradient and large hillslope to channel relief, we observe no correlation between elevation or spatial location and basin geometry. However, we find that two physiographic units in Coweeta have distinct zero‐order basin morphologies. These are the steep, thin soiled, high‐elevation Nantahala Escarpment and the lower‐gradient, lower‐elevation, thick soiled remainder of the basin. Our results indicate that basin slope and area negatively covary, producing the distinct forms observed between the two physiographic units, which we suggest arise through competition between spatially variable soil creep and stochastic landsliding.

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

Cited by 7 publications

References 61 publications

The human impact on North American erosion, sediment transfer, and storage in a geologic context

The human impact on North American erosion, sediment transfer, and storage in a geologic context

Fluvial activity in major river basins of the eastern United States during the Holocene

Controls on Zero‐Order Basin Morphology

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