Doctoral Dissertations

Date of Award

5-2018

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Geography

Major Professor

Yingkui Li

Committee Members

Jonathan M. Harbor, Nicholas N. Nagle, Robert A. Washington-Allen, Daniel C. Yoder

Abstract

The pattern, magnitude, and frequency of hillslope erosion and deposition are spatially varied under the influence of micro-topography and channel geometry. This research investigates the interrelationships between erosion/deposition, micro-topography, and channel connectivity on a hillslope in Loudon, Tennessee using the centimeter (cm) level temporal Digital Elevation Models collected using laser scanning. This research addressed (1) the effect of spatial resolution on the erosion/deposition quantification, and rill delineation; (2) the influences of micro-topographic factors (e.g. slope, roughness, aspect) on erosion and deposition; (3) the relationship between the structural connectivity -- depressions and confluence of rills -- and the sedimentological connectivity. I conducted (1) visual and quantitative assessments for the erosion and deposition, and the revised automated proximity and conformity analysis for the rill network; (2) quantile regression for micro-topographic factors using segmented rill basins; and (3) cross-correlation analysis using erosion and deposition series along the channels.Overall, rills are sedimentologically more dynamic than the interrill areas. A larger grid size reduces the detectable changes in both areal and volumetric quantities, and also decreases the total length and number of rills. The offset between delineated rills and the reference increases with larger grid sizes. A larger rill basin has higher erosion and deposition with the magnitude of erosion greater than deposition. The slope has a positive influence on erosion and a negative one on deposition; roughness has a positive influence on deposition and a negative one on erosion. Areas that are more north-facing experience higher erosion and lower deposition. Rill length explains 46% of the variability for erosion and 24% for deposition. The depressions are associated with higher erosion in the downslope direction. The correlations between the erosion and the confluence are positive; the correlation between the deposition and the sink is positive. Overall, the influence of structural connectivity on the sedimentological connectivity is within 25 cm in both upstream and downstream directions. This research contributes to the understanding in how the sediment movement on hillslopes is governed by topographic variations and channel connectivity, and future work may explore hillslope channels at broader geographical and temporal scales.

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