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How does a newly-formed drainage divide migrate after a river capture event? Insights from numerical simulations and two natural cases (Yarlung-Yigong, and Dadu-Anning) in the Tibetan Plateau region
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  • Shuang Bian,
  • Xibin Tan,
  • Chao Zhou,
  • Feng Shi,
  • Yiduo Liu
Shuang Bian
Institute of Geology, China Earthquake Administration
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Xibin Tan
Institute of Mountain Hazards and Environment, Chinese Academy of Sciences

Corresponding Author:[email protected]

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Chao Zhou
State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration
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Feng Shi
State Key Laboratory of Earthquake Dynamics, Institute of Geology, China Earthquake Administration, Beijing 100029, China.
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Yiduo Liu
Institute of Mountain Hazards and Environment, Chinese Academy of Sciences
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Abstract

Tectonic and/or climatic perturbations can drive drainage adjustment. The capture events, significantly changing the river network topology, are the major events in river network evolution. While they could be identified through field observations and provenance analysis, reconstructing this evolution process and pinpointing the capture time remain challenging. Following a capture event, the steady-state elevation of the captor river will be much lower than that of the beheaded river. Then, the newly-formed drainage divide will migrate towards the beheaded river, a process also known as river-channel reversal. The migration of the newly-formed drainage divide provides a new perspective for identifying the reorganization of the river network. Here, we employ numerical modeling to reproduce the characteristic phenomena of drainage-divide migration following capture events and analyze the effects of different parameters on the migration rate. We find that (1) the migration of newly-formed drainage divides can last for tens of millions of years, with the migration rate decreasing exponentially over time; (2) larger captured area, higher uplift rate, and lower erosional coefficient, all of which cause a higher cross-divide difference in steady-state elevation, will cause higher migration rate of the newly-formed drainage divide. This insight was further applied to the Dadu-Anning and Yarlung-Yigong capture events. We predict the present Dadu-Anning drainage divide would further migrate ~65–92 km southward to reach a steady state in tens of millions of years. The Yarlung-Yigong capture event occurred in the early-middle Cenozoic, which implies that the late-Cenozoic increased exhumation rate is not related to the capture event.