Adams and his team overcame this challenge by combining regression techniques with numerical models of how rivers erode.

“We tested a wide variety of numerical models to reproduce the observed erosion-rate pattern across Bhutan and Nepal. Ultimately only one model was able to accurately predict the measured erosion rates,” Adams said. “This model allows us for the first time to quantify how rainfall influences river incision and hillslope erosion rates in mountainous landscapes.”

“Our findings show how critical it is to account for rainfall when assessing patterns of tectonic activity using topography, and also provide an essential step forward in addressing how much the slip rate on tectonic faults may be controlled by climate-driven erosion at the surface,” Whipple said.

The findings of this study also carry important implications for land-use management, infrastructure maintenance and hazards in the Himalaya.

Rainfall-driven variations in erosion rates can lead to important differences in landscape instabilities and hazards. In the Himalaya, there is the ever-present risk that high erosion rates can drastically increase sedimentation rates behind dams, jeopardizing critical hydropower projects.

Furthermore, enhanced river incision can undermine hillslopes, elevating the risk of debris flows or landslides, some of which may be large enough to dam the river, creating a new hazard — lake outburst floods. 

“Our data and analysis provide an effective tool for estimating patterns of erosion in mountainous landscapes such as the Himalaya, and thus, can provide invaluable insight into the hazards that influence the hundreds of millions of people who live within and at the foot of these mountains,” Adams said.

Building on these findings, Whipple is leading the team in an effort to extend this analysis in an application to the full length of the Himalaya.

“This study will test our model against additional data sets from the central and western Himalaya and apply the results to estimate patterns of erosion rate across the entire range,” Whipple said. “Erosional patterns will allow us to differentiate among competing models of the mountain-building process and help refine estimates of seismic and erosional hazards.”

This article was written by Byron Adams and Victoria Tagg of Bristol University (UK) with contributions by Karin Valentine of ASU’s School of Earth and Space Exploration.