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River mouth opens on Dec. 27, 2020

Dec. 28, 2020, Gualala River mouth has opened; photo by Teresa Denniston.


The mouth of the Gualala River opened to the ocean on Sunday, Dec. 27, 2020 at ~11:30am, reconnecting the important lagoon fish rearing habitat for out-migrating salmonids, synchronized with suitable stream conditions for returning spawners.

This is a high tide, high swell, low-energy breach condition in the photos. When the lagoon is full and it breaches on a low tide during low swell, the difference in water levels (and the lack of “push-back” by big waves) is like a dam breach. The mouth erodes to an oversize width releasing the lagoon volume, up to about a quarter of the spit, then it shrinks to an equilibrium size for the daily tidal prism.

Flows upstream on the river are pretty light, low energy. The gravel and cobbles in the bed are still in place from last year, coated with old dead algal mats. There is still Azolla washing out, and the river is slightly turbid from dissolved organics rather than fine mineral sediment. Full of eDNA, we hope. Tributaries are running clear and clean. No fish activity observed or reported yet, though, outside of the lagoon.