Date of Award

1-24-2024

Degree Type

Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Geography

Advisor(s)

Peng Gao

Keywords

Alluvial river;Anabranching channel;Channel pattern;Floodplain;Meandering channel

Subject Categories

Geography | Social and Behavioral Sciences

Abstract

Alluvial rivers exhibit diverse forms and dynamic processes based on the physiographic configuration and in response to the interactions between water flow, sediment transport, and channel morphology. The current understanding of the formative and evolutionary processes controlling channel morphology and the dynamics remains incomplete, as it falls short of explaining and predicting a variety of channel forms and processes. Using data derived from remote sensing analysis and field measurement, this dissertation investigates the morphological characteristics, lateral adjustment, and channel-floodplain interactions of meandering and anabranching rivers in a pristine, high-altitude environment in the source watershed of the Yellow River, eastern Qinghai-Tibet Plateau. Through three chapters (i.e., Chapter 2, 3, and 4) that respectively examine meandering channels, meandering river floodplains, and anabranching channels, this dissertation explores the pioneer issues regarding fluvial processes in these systems, demonstrating the morphodynamic complexity embraced in meandering and anabranching systems. In Chapter 2, I characterize meander-bend morphology and propose a quantitative criterion to distinguish compound-form meander bends from simple meander bends. I also quantify the lateral migration of meander bends, examine the relationships between bend morphology and lateral migration, and assess the geomorphic implications of it, highlighting the inherent mechanism of meander-bend evolution through which the planform structures remain stable. In Chapter 3, I characterize hydrologic connectivity and morphological variation of oxbow lakes, an essential geomorphic unit in floodplains of meandering rivers, and find very low hydrologic connectivity between oxbow lakes and the main channel, owing to the unique paleogeographic setting of the study area, using a newly proposed probability-based index for quantifying hydrologic connectivity. In Chapter 4, I scrutinize the dynamic patterns of the anabranching system and assess their flow efficiency based on five heuristic anabranching structures. The results explicitly suggest that island dynamics and their interactions with channels are the key components for understanding anabranching evolution and stability. Overall, as Chapter 5 concludes, this dissertation provides new insights into the morphodynamic complexity of alluvial channel forms and processes and sets a foundation for future research to serve global and trending needs.

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Open Access

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Geography Commons

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