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

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.

Name thesis:degree_name

Ph.D.

Level thesis:degree_level

Dissertation

Discipline thesis:degree_discipline

Geology

Grantor

University of Illinois at Urbana-Champaign

Year dc:date

2023

Author dc:creator

• Meghani, Nooreen Amina

Contributors dc:contributor

• Anders, Alison M
• Marshak, Stephen
• Phillips, Andrew
• Rhoads, Bruce

• Post-glacial
• Geomorphology
• Central Lowlands
• Sangamon
• Vermilion
• Quaternary
• Fluvial
• River Evolution
• Drainage Density
• Post-glacial Fluvial Network Development

Statement dc:rights

• Copyright 2023 Nooreen Meghani

Language dc:language

en, eng

Handle dc:identifier

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

OAI record oai:identifier

https://www.ideals.illinois.edu/oai-pmh?verb=GetRecord&metadataPrefix=etdms&identifier=oai%3Awww.ideals.illinois.edu%3A2142%2F120106