I don't know much about Naselle other than its a logging town in WA's poorest county. I would look at the precipitation maps for WA.
http://content.lib.washington.edu/cmpweb/resources/map-rainfall.html
Because logging rules this poor county I would guess there is a lot of clearcutting, lots of rain, and therefore lots of flooding. That's at least how it is in Lewis Co.
Here's some flooding info I found on the Naselle river with a quick google search:
http://weather.hamweather.com/rivers/gauge/NASW1.html
1) 20.62 ft on 01/07/2009
2) 19.26 ft on 03/18/1997
3) 18.45 ft on 11/24/1990
4) 17.62 ft on 12/20/1994
5) 17.10 ft on 11/23/1986
6.25 ft is normal.