Carkeek Park Salmon Professional Review and Guide
"In dry weather the creek here can be reduced to a rivulet crossing the sand, too small to carry even the slimmest of salmon fry to saltwater. This trickle, believe it or not, becomes a waterway with more gusto on a rainy fall day, allowing the chum and coho salmon that return to Piper’s Creek to make their entrance.
This is the struggling urban creek they left one to five years ago (each species differs in this regard), returning usually by the hundreds to spawn in their natal stream. They come at different times, but especially during a new or dark moon, after a heavy rain that plumps the stream to optimal fullness, and during high tide. Salmon gather in the Sound near the creek’s mouth, and when conditions are right, they begin their upstream migration."