A cross-divide contrast index (C) for assessing controls on the main drainage divide stability of a mountain belt

A main drainage divide is a high terrain that separates neighboring drainage basins. It is dynamic through time and naturally evolves towards a steady state, which depends on tectonics, lithology, precipitation, base level, and drainage-basin morphology. How these factors influence the position of main drainage divides is the precondition for tectonics and climate reconstruction from the main drainage divide. However, their controls on the main drainage divide stability are not fully quantified. Here, we introduce a cross-divide contrast index (C) to amalgamate the differences in lithology, precipitation, channel height, and drainage-basin morphology across the main drainage divide. We derive an analytical solution to quantify the relationship between these factors and the predicted stable location of the main drainage divide in a mountain belt. We then use numerical landscape evolution models to test and visualize the formula. We further show how the equation applies to three distinct natural examples for tectonic information extraction. We conclude that (1) the sinuous shape of the main drainage divide in a mountain belt is caused by the along-divide variation in the C value; (2) the ratio of uplift rates at two edges of a mountain can be reliably extracted from the main drainage divide once the C value is considered; and (3) for a migrating main drainage divide, our method can be used to predict its final stable location, which could provide useful information for ecological studies and geoengineering.(c) 2021 The Authors. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http:// creativecommons.org/licenses/by-nc-nd/4.0/).

Automated summary

In this study, a cross-divide contrast index (C) is introduced to quantify the differences in lithology, precipitation, channel height, and drainage-basin morphology across the main drainage divide. An analytical solution is derived to establish the relationship between these factors and the predicted stable location of the main drainage divide in a mountain belt. The formula is tested and visualized using numerical landscape evolution models. The study demonstrates the application of the formula in extracting tectonic information and predicts the final stable location of a migrating main drainage divide.