Channel Steepness Biases and Nonsteady Erosion in Landscapes Evolving Under Cyclical Climate

Abstract Changes in climate through time obscure tectonic signals in topography. Here, we derive expressions describing how accurately channel steepness reflects tectonics and substrate erodibility when the modern discharge proxy used to calculate channel steepness (a proxy for fluvial relief) does not equal the effective discharge defining fluvial relief over landscape evolution timescales (≥10 4 years). Through a sensitivity analysis, we show that these solutions likely apply to detachment‐limited landscapes evolving with Milankovitch timescale climate oscillations. A signature of climate oscillations in topography is mismatch (discordance) in discharge‐normalized channel steepness between adjacent hydrologically connected streams. Studies should seek to identify this signature, as it may indicate incomplete normalization for climate's influence on channel steepness.