Plain Language Summary
Rainfall in mountain landscapes often varies with elevation; a pattern
known as orographic rainfall. Rivers that sculpt these landscapes rely
on rainfall for their erosive power, where more rainfall typically means
greater erosive power. Rainfall also affects how steep these rivers are,
which in turn affects the steepness of the topography around them. Here,
we investigate how concentrating rainfall at higher and lower elevations
– representing two common orographic rainfall patterns that may be
enhanced or relaxed by climate change – influences the steepness
mountain rivers, erosion patterns, and thus the evolution of mountain
topography. We show that these orographic rainfall patterns complicate
simple expected relationships among metrics commonly used to quantify
the role of rainfall (and more broadly climate) on the topography of
mountain landscapes. Further, we show that rivers respond in unexpected
ways to changes in orographic rainfall patterns, as would occur
following a change in climate, suggesting that common wisdom about how
rivers and mountain landscapes respond to changing climates is
incomplete.