Quantifying tectonic, lithological, and climatic controls on upland river dynamics
File(s)
Author(s)
Zhou, Ziqiang
Type
Thesis or dissertation
Abstract
Upland rivers shape landscape evolution and release sediments into source-to-sink systems in response to tectonics, lithology, and climate. If and where their dynamics are quantified, channel geometry can be leveraged to provide long-term insights into seismic and erosion hazards. Yet, channel dynamics involve flux-dependent and threshold-stochastic processes that are yet to be fully understood. In this thesis, I probe these processes by examining tectonic, lithological, and climatic controls on channel geometry.
I first take a landscape-scale perspective to test the use of the simple, classic stream power incision model (SPIM) in tectonically active, lithological heterogeneous landscapes. I leverage the well-constrained Gulf of Corinth, Greece, as a natural laboratory to demonstrate that the classic SPIM successfully isolates tectonic and lithological signals. I then narrow my focus to two Corinth rivers to investigate how lithology, through its influence on sediment generation, modulates channel responses to tectonics via flux-dependent processes. I show that, until knickpoints migrate into abrasion-resistant rocks in these rivers, lithology dominates over tectonics in bedload sediment generation via abrasion. I further suggest that lithology-influenced sediment supply determines the excess shear stress required for equilibrium and influences how that excess shear stress is partitioned between channel width and slope adjustments. Finally, I zoom out to examine the role of threshold-stochastic processes on incision by comparing channel width and slope responses to discharge-variability proxies on a global scale. The results challenge the traditional slope-centred perspective and instead emphasise the sensitivity of channel width, likely because bank erosion requires a higher threshold than bed erosion.
In a nutshell, this thesis sheds new light on upland river dynamics in terms of flux-dependent incision and threshold-stochastic processes. In particular, I clarify when the classic SPIM is most effective and highlight the importance of channel-width dynamics, with important implications for assessing seismic and erosion hazards.
I first take a landscape-scale perspective to test the use of the simple, classic stream power incision model (SPIM) in tectonically active, lithological heterogeneous landscapes. I leverage the well-constrained Gulf of Corinth, Greece, as a natural laboratory to demonstrate that the classic SPIM successfully isolates tectonic and lithological signals. I then narrow my focus to two Corinth rivers to investigate how lithology, through its influence on sediment generation, modulates channel responses to tectonics via flux-dependent processes. I show that, until knickpoints migrate into abrasion-resistant rocks in these rivers, lithology dominates over tectonics in bedload sediment generation via abrasion. I further suggest that lithology-influenced sediment supply determines the excess shear stress required for equilibrium and influences how that excess shear stress is partitioned between channel width and slope adjustments. Finally, I zoom out to examine the role of threshold-stochastic processes on incision by comparing channel width and slope responses to discharge-variability proxies on a global scale. The results challenge the traditional slope-centred perspective and instead emphasise the sensitivity of channel width, likely because bank erosion requires a higher threshold than bed erosion.
In a nutshell, this thesis sheds new light on upland river dynamics in terms of flux-dependent incision and threshold-stochastic processes. In particular, I clarify when the classic SPIM is most effective and highlight the importance of channel-width dynamics, with important implications for assessing seismic and erosion hazards.
Version
Open Access
Date Issued
2026-04-20
Date Awarded
2026-08-01
Copyright Statement
Attribution-NonCommercial 4.0 International Licence (CC BY-NC)
License URL
Advisor
Whittaker, Alex
Bell, Rebecca
Hampson, Gary
Sponsor
Department of Earth Science & Engineering, Imperial College London
Publisher Department
Department of Earth Science & Engineering
Publisher Institution
Imperial College London
Qualification Level
Doctoral
Qualification Name
Doctor of Philosophy (PhD)