Non‐Linear Morphodynamic Response of Deltas to Extreme Events

Abstract Deltas, the interface between riverine and coastal systems, host ∼500 million people and function as crucial ecological nexuses. The magnitude and frequency of extreme floods are projected to intensify as climate changes, yet the potential impacts on delta morphodynamics remain poorly understood. Using the pyDeltaRCM numerical model, we explore the impact of extreme flow frequency on delta morphology. Morphometric analyses demonstrate a non‐linear morphodynamic response across two orders of magnitude of extreme flow intermittencies, I . Under medium I , deltas are smallest with the fewest, narrowest channels. In contrast, at both low and high I , deltas grow the largest, with the widest and most numerous channels. Channel mobility appears unaffected and delta slope declines monotonically as I increases. We identify drivers of this non‐linear response, generating a novel conceptual model of delta adjustment to extreme flows. Our morphodynamic projections can help anticipate and manage geomorphic change on deltas undergoing flood‐frequency change.