Like I was saying there every where. A couple years ago a company I was working for relocated there office and it was close to Fanno creek in the tigard area. Out of curiosity I threw a trap in the creek and I let it soak from 3:00 one friday afternoon showed up at 7:00 sat. morning and there were 63 fairly decent dads in it all eater size.
Smaller creeks like Fanno, Abernethy,Butte etc. can be fished out very fast so you need to have several spots. And not put to much pressure all in the same area.
My best advice to find crawdads is a slow moving creek, river like the tualatin,the pudding river and just toss a trap in make sure your bait is in a bait cage.So your bait will last. And what ever you use for bait make sure its fresh or frozen fresh. I've heard tales of the more rotten the better. Thats hogwash the fresher the better. I try to make shad my first choice. If I dont have shad salmon and steelhead carcuss works well to especially if they still have the gills.