Fluvial System Response to Abrupt Base-Level Fall: Mapping Tributary Stream Terraces in the Lower Chippewa River Watershed

Authors: Katie Grong*, University of Wisconsin - Eau Claire, Douglas Faulkner*, University of Wisconsin-Eau Claire, Hunter Delikowski*, University of Wisconsin - Eau Claire
Topics: Geomorphology, Earth Science, Geographic Information Science and Systems
Keywords: Wisconsin, autogenic, complex response
Session Type: Virtual Poster
Day: 4/9/2021
Start / End Time: 3:05 PM / 5:50 PM
Room: Virtual 52
Presentation File: No File Uploaded

The Lower Chippewa River (LCR), a tributary to the Upper Mississippi River (UMR) in west-central Wisconsin, was a glacial meltwater stream during the Late Wisconsinan. During regional deglaciation, two significant episodes of UMR incision lowered the LCR’s base level abruptly, which incised in response. Based on terrace mapping and OSL dating, Faulkner et al. (2016) determined that LCR incision was prolonged and episodic and proposed a model to describe and explain the progression of incision up the LCR valley. Our research, which focuses on the incision of LCR tributaries, is a first step in testing the Faulkner et al. model. We began by mapping terraces along the two largest tributaries, the Eau Claire River (ECR) and Red Cedar River (RCR). We used LiDAR-derived DEMs to identify and digitize terrace remnants and to determine their heights above their adjacent rivers. We then created longitudinal terrace profiles to illustrate how incision may have propagated up the RCR and ECR valleys. We then applied previous methods to map terraces along smaller tributaries. In addition, we analyzed the size of tributary watersheds and their proximity to the UMR as possible controls on tributary terrace formation and preservation of terrace remnants. This was done to determine if the spatial pattern of terraces in tributary valleys. is consistent with the model of Faulkner et al. (2016). We found that it generally is. Dating of terrace remnants is necessary to determine if the timing of tributary incision is also consistent with the model.

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