Tectonically dominant surface denudation and topography in the Himalaya: Evidence from coupling between bedrock channel and valley hillslope topographies

The Himalaya, a leading example of active mountains, is jointly shaped by intense tectonics, extreme climate and surface denudation. However, the causal relationship among these agents remains controversial. In this work, by an integrated analysis of bedrock channels and valley hillslopes using process-based models, we discover 3D-linear correlations in logarithmic space among precipitation-estimated stream discharge, channel gradients and valley hillslope gradients. This finding indicates that channel incision and hillslope denudation are dynamically coupled in sculpting the erosional topography in tectonically active domains of the Himalaya. The channel-hillslope coupling provides an independent approach to quantify key parameters of erosional models. Surface denudation indices simulated along streams and in drainage basins present a regular arrangement of high- and low-denudation zones across the Himalaya, which coincides well with available thermochronological and structural data and thereby supports a tectonic dominance on surface denudation rates and topography over medium-long timescale.

Automated summary

Through integrated analysis of bedrock channels and valley hillslopes in the Himalaya, linear correlations in logarithmic space among precipitation-estimated stream discharge, channel gradients and valley hillslope gradients were discovered, suggesting a dynamic coupling between channel incision and hillslope denudation in sculpting erosional topography. This coupling provides an independent approach to quantify key parameters of erosional models, and the simulated surface denudation indices show a regular arrangement of high- and low-denudation zones across the Himalaya, supporting a tectonic dominance on surface denudation rates and topography over medium to long timescales.