I will add this. The Wynoochee Dam was for flood control and has worked. For the Chehalis in tide water it is Olympic and Upper Basin both at flood stage with wind holding the bay. The dam times it discharges in emergency situations to reduce the Wynoochee flows at high tide in flood events, mostly. Had some difficulties few years back when TP managed to flows but it is my understanding the Army Corp straightened that out. My house is 20 ft from the Chehalis in tidewater so I am well aware of how the river works. Big flood Satsop years back 18 in below floors, the big event upper Chehalis around 8 in below the floors. The big / flood with the windstorm that blew everything apart, 1 in. Full flood and that wind held the river at full flood at slack water ( and I mean the river went slack ) for nearly two hours.

Contrary to common beliefs Mother Nature is not a nice person and you will never be able to plan for everything, she will getcha sooner or later be it a flood, hurricane, volcano, or earthquake. Your never 100% safe.