First‐Order River Delta Morphology Is Explained by the Sediment Flux Balance From Rivers, Waves, and Tides

We present a novel quantitative test of a 50-year-old hypothesis which asserts that river delta
morphology is determined by the balance between river and marine influence. We define three metrics to
capture the first-order morphology of deltas (shoreline roughness, number of distributary channel mouths, and
presence/absence of spits), and use a recently developed sediment flux framework to quantify the river-marine
influence. Through analysis of simulated and field deltas we quantitatively demonstrate the relationship
between sediment flux balance and delta morphology and show that the flux balance accounts for at least
35% of the variance in the number of distributary channel mouths and 42% of the variance in the shoreline
roughness for real-world and simulated deltas. We identify a tipping point in the flux balance where wave
influence halts distributary channel formation and show how this explains morphological transitions in real
world deltas.