Most of the Northwest's coast is equipped with early warning systems for tsunamis. (See, for example, this article from the Newport (Oregon) News-Times.) But that doesn't make us immune from giant earthquakes and the resulting tsunamis. The 1964 Alaska earthquake was actually bigger on the Richter scale than the recent Indonesian temblor, and it set off a giant wave that swept a few Oregonians and Washingtonians to their deaths. A similar-scale quake and wave with more-local origins likely occurred around 1700, according to a good article in the Coos Bay (Oregon) World.
Flooding rivers pose a similar threat. They're typically not as sudden as tsunamis, but far more northwesterners are exposed to them. And unlike tsunamis, river flooding is an annual occurrence, with massive floods coming once or twice in a lifetime. (As climate changes, the severity of flooding may be accelerating.)
And though we have more systems in place, preparedness in the form of disaster kits, escape routes, and early-warning sirens is still a pale imitation of true preparedness for high waters.