A system in which peak ebb speeds exceed peak flood speeds, usually because the ebb is shorter than the flood or because river flow adds to it. Ebb-dominant channels tend to flush sediment out and stay deep, while flood-dominant ones import sand and mud and tend to shoal. The asymmetry is tied to the phase between M2 and its overtide M4 and to the area of flats and marsh that fill on the flood.
Main channel is ebb-dominant so it keeps itself open, but the side channel is flood-dominant and silts every year.
Related terms
Overtide
A higher-frequency constituent, such as M4, generated when a tide distorts in shallow water.
Tidal prism
The volume of water that flows into a bay or estuary on the flood and out on the ebb.
Ebb
Tidal current running out toward the sea and down rivers and estuaries, mostly while the water is falling.
Flood
Tidal current running in from the sea and up rivers and estuaries, mostly while the water is rising.