There is no answer to your question. Or maybe, "it depends" is the correct answer. Look at it this way. A spectacular water view vs. a comparable that faces a garbage dump, would likely require a large adjustment. A spectacular water view vs. a spectacular city view may require no adjustment.
Also consider the property. A spectacular view on a million dollar home would likely have a higher contributory value than a spectacular view on a one hundred thousand dollar home. One thing is for sure. If someone has a set answer to your question, they have no idea what they are talking about!
One last thing. I'm an appraiser who lives in West Linn. The most important thing is to get the property appraised by someone with West Linn knowledge. Even though properties in Oregon City, Gladstone, or Milwaukie may be within one-mile, they will have completely different values.