Structural and sedimentological connectivity on a rilled hillslope

Xiaoyu Lu; Yingkui Li; Robert A Washington-Allen; Yanan Li

doi:10.1016/j.scitotenv.2018.11.137

Structural and sedimentological connectivity on a rilled hillslope

Sci Total Environ. 2019 Mar 10:655:1479-1494. doi: 10.1016/j.scitotenv.2018.11.137. Epub 2018 Nov 16.

Authors

Xiaoyu Lu¹, Yingkui Li², Robert A Washington-Allen³, Yanan Li⁴

Affiliations

¹ Department of Geography, University of Tennessee, Knoxville, TN 37996, USA.
² Department of Geography, University of Tennessee, Knoxville, TN 37996, USA. Electronic address: yli32@utk.edu.
³ Department of Agriculture, Veterinary and Rangeland Sciences, University of Nevada, Reno, NV 89557, USA.
⁴ Department of Geography, Texas State University, San Marcos, TX 78666, USA.

PMID: 30577139
DOI: 10.1016/j.scitotenv.2018.11.137

Abstract

Sedimentological connectivity describes the continuity of sediment transport across a topographically heterogenous landscape. Sedimentological connectivity reflects the changes in the balance between flow sediment load and transport capacity and is mainly influenced by the longitudinal (dis)continuity of channels that is associated with channel depressions and confluences. Past studies have focused on structural and sedimentological connectivity at the basin scale, with only a few examining this phenomenon at the hillslope scale. Important questions have yet to be answered, including "How do within-channel barriers and channel confluences affect the flow/sediment balance?" and "At what spatial extent do these influences take place?" This study investigated the structural and sedimentological connectivity within a rill network on a hillslope in Loudon, Tennessee, USA. We used the difference in a ground lidar generated time-series of seven digital elevation models (DEMs), the DEM of Difference (DoD or ΔDEM), to quantify the spatio-temporal dynamics of erosion and deposition on a hillslope for 6 periods from December 2014 to December 2016. We found that later periods had the greatest amount of erosion and net sediment loss (0.59 ± 17 m³). We compared the observed sediment redistribution patterns to a GIS-based index of connectivity (IC). In order to examine the influence of structural (dis) connectivity on sedimentological connectivity, we compared the time series of patterns to the occurrences of rill channel confluences and depressions. We found a spatially consistent relationship between the IC and the observed erosion/deposition pattern. However, sediment detachment can also be driven by gravitational sidewall failure, which is not well described by the IC. The scouring at rill confluences leads to higher erosion in both upslope and downslope sections of a rill channel; the ponding at rill depressions yields upslope deposition and downslope erosion.

Keywords: Connectivity; Geomorphology; Hillslope processes; Sediment movement; Signal processing.