ALERT! The Wundermap folks have made changes in the usability of their product. It no longer allows you to map the USGS gauges. I’ll be looking into a replacement for paddlers. I have been using several apps fro paddle trips now. Rivercast and River Data. You might also consider RecGovCamp as a way to find campsites. Since many of them also are located near water, you should be able to find a location close to a desired locale.
If you are looking for places to go, check here first for local conditions. Make sure you click the panels on the right to show USGS river gauges.