The Effects of Rainfall Temporal Variability on Landscape Evolution

Abstract Rainfall characteristics such as intensity, duration, and frequency are key determinants of the hydrogeomorphic response of a catchment. The presence of non‐linear and threshold effects makes the relationship between rainfall variability and geomorphological dynamics difficult to quantify. Yet, this is particularly relevant under predicted exacerbated erosion induced by an intensification of hydroclimatic extremes and ensuing erosional processes. In this study, we evaluate the effects of rainfall temporal variability on catchment morphology and sediment erosion, transport, and deposition across diverse grain sizes, catchment shapes, and climates. Specifically, we simulate multiple rainfall realizations using the modified Bartlett‐Lewis rectangular pulse model and assess catchment geomorphic response through the CAESAR‐Lisflood landscape evolution model. Virtual catchments are used in the numerical experiments and simulations are conducted over centennial timescales. Simulation results show that higher rainfall temporal variability increases net sediment discharge, domain erosion, and deposition volumes. Particularly, more arid regions respond more actively to rainfall variations and coarser grain size configurations amplify the hydrogeomorphic response. We derive a power‐law function linking standardized changes in catchment net sediment discharge and fluctuations in rainfall temporal variability, with a consistent exponent across simulations and supported by long‐term observational data. Such quantification of the effects of predicted changes in rainfall patterns on catchment hydromorphological response is crucial to forecasting the implications of expected changes in rainfall patterns for downstream sediment delivery. Results further highlight the need to explicitly account for local variability in rainfall intensification when estimating potential changes in soil erosion fluxes.