Simple metrics predict salt-marsh sediment fluxes

Abstract

The growth (or decay) of salt marshes depends on suspended‐sediment flux into and out of the marsh. Suspended‐sediment concentration (SSC) is a key element of the flux, and SSC‐based metrics reflect the long‐term sediment‐flux trajectories of a variety of salt marshes. One metric, the flood‐ebb SSC differential, correlates with area‐normalized sediment flux and can indicate salt‐marsh resilience over months to years. We hypothesize that these metrics may be relevant over shorter time periods. With data from 13 salt‐marsh channels, we show that sediment flux direction and magnitude can be inferred from SSC differential over a wide range of timescales. Furthermore, in settings characterized by a standing tidal wave, the water‐level gradient can be used instead of velocity to compute the SSC differential, enabling less‐intensive measurements that capture fundamental sediment‐flux parameters. Distilling the sediment‐flux trajectory into simple metrics improves sediment‐budget assessment, drives geomorphic model development, and clarifies field observations.