Evaluating lithologic controls on erosional fluvial landforms using digital topographic data with 1 to 30 meter resolution

Jin, Xi

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https://hdl.handle.net/2142/122030 Copy

Description

Title

Evaluating lithologic controls on erosional fluvial landforms using digital topographic data with 1 to 30 meter resolution

Author(s)

Jin, Xi

Issue Date

2023-12-06

Director of Research (if dissertation) or Advisor (if thesis)

Anders, Alison M

Department of Study

Earth Sci & Environmental Chng

Discipline

Geology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

DEM, lithology, erosional fluvial landforms

Abstract

Lithology influences the development and morphology of landscapes. Specifically, lithology influences rates of fluvial erosion, the steady-state steepness of river profiles and the length of hillslopes. Lithology may also influence the relative importance of groundwater to river discharge, impacting the energy available for fluvial erosion. We measure differences in drainage density and valley extent between monolithologic basalt and sandstone watersheds in the Oregon Coast Range, USA and near the eastern margin of the Tibetan Plateau in the Xichang-Zhaotong region of China. We use a well-established method to extract channel networks from high-resolution (1-m) digital elevation models (DEMs) in Oregon. We compare these results with an evaluation of drainage density derived from a globally-available 30-m resolution DEM and with a new metric of valley extent (dimensionless valley density) we created for use with 30-m resolution data. We find that sandstone watersheds in both study areas consistently exhibit larger drainage density and valley extent than neighboring basalt watersheds although these two areas are quite different in both geomorphology and structure. In a steady-state landscape like the Oregon Coast Range, uplift is balanced everywhere by erosion. We find that the balance between uplift and erosion in basalt basins is characterized with steeper and longer hillslopes and shorter and steeper rivers, resulting in a low drainage density. In contrast, sandstone basins in the Oregon Coast Range have lower slope and shorter hillslopes, longer, lower-sloped, more sinuous and branching river channels and a higher drainage density. In a transient landscape like the Xichang-Zhaotong region, drainage density increases over time to respond to the river incision propagating from the deep valleys along the edge of the low relief surfaces towards the interior. Here, the higher erodibility of sandstone allows for more rapid development of river networks (both vertical incision and headward extension) than in basalt. We also demonstrate that previous methods for evaluating drainage density with 30-m resolution data are strongly dependent on the assumed value for a threshold contributing area for channelization and this sensitivity needs to be examined in interpreting the results. Further, we show that our new metric of dimensionless valley density captures differences in landscapes from low-resolution data that are also apparent in high-resolution data. Overall, we demonstrate that lithology has a strong influence on fluvial geomorphology and that 30-m resolution data can reveal aspects of this influence.

Graduation Semester

2023-12

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Xi Jin

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