Post-glacial rivers: Rates of development, utilization of inherited glacial features, and resulting morphology

Meghani, Nooreen Amina

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https://hdl.handle.net/2142/120106 Copy

Description

Title

Post-glacial rivers: Rates of development, utilization of inherited glacial features, and resulting morphology

Author(s)

Meghani, Nooreen Amina

Issue Date

2023-04-27

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

Anders, Alison M

Doctoral Committee Chair(s)

Anders, Alison M

Committee Member(s)

• Marshak, Stephen
• Phillips, Andrew
• Rhoads, Bruce

Department of Study

Earth Sci & Environmental Chng

Discipline

Geology

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

Ph.D.

Degree Level

Dissertation

Keyword(s)

• Post-glacial
• geomorphology
• Central Lowlands
• Sangamon
• Vermilion
• Quaternary
• fluvial
• river evolution
• drainage density
• post-glacial fluvial network development

Abstract

The Central Lowlands physiographic province (CL) is partially defined by the lasting influence of continental glaciation. Near the edge of the Laurentide Ice Sheet (LIS), glaciers were primarily depositional, and, over the course of several Pleistocene glaciations, deposited 10s to 100s of meters of sediment. River networks in the CL were profoundly disrupted by glaciation. Following glaciation, precipitation-fed fluvial systems began to act on the surface. I demonstrate that the CL generally recovered a mature drainage density in ~50 ka, less than the length of a typical interglacial episode. This timescale is surprisingly short given the low slopes and profound disconnection of the post-glacial landscape. I describe a new conceptual model of fluvial network integration that explains how this integration can happen so rapidly: instead of solely relying on channel-head incision to develop fluvial networks, developing river systems take advantage of the remnants of glacial forms, either reusing or repurposing them. In addition, when closed basins are integrated, a large area with developed channels can be added to the network. Piecemeal integration results in the deranged rivers that characterize the post-glacial landscape. I document examples of the forms and processes highlighted in my model in the Sangamon watershed of Illinois. My conceptual model emphasizes top-down processes, such as spillover from lakes, in addition to the typical bottom-up process of channel head cutting due to base level falls I show that the slow adjustment to bottom-up processes allows signals of piecemeal integration to be observed in the longitudinal profiles of post-glacial rivers and find that in the Vermilion watershed of Illinois the long profile has been evolving slowly and preserves a signature of base-level fall that occurred ~17 ka.

Graduation Semester

2023-05

Type of Resource

Thesis

Copyright and License Information

Copyright 2023 Nooreen Meghani

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