It has a focus on paddling routes in Canada. The route you're considering may be listed already, of if not, someone may know why not.
You may also be able to check it out on Google Earth, if the satellite photography for the route happens to be their best quality. If so, you can often see rapids, wave trains, probable portages, possible campsites, etc. You can name a town close to the river and GE will zoom right in. Also note that in the "File" pull-down of Google Earth, there is a Save Image function. If you have a photo editor, you can crop or link the images, and often you can get a clearer image with basic editing manipulation.