Case in point..... I was planning a trip for the latter part of November on the St. Mary's River. After checking the stream flow ( watching it for about two weeks ) I realized it was not a good idea since the water level is going down and hit the Don't paddle the river depth. They don't say ... Don't paddle it .... just give you the depth and stream flow day by day.
To double check the information I called the outfitter and in basic language he said the river was great for backpacking but not paddling since the water level is way down and he will not shuttle anyone to the section I wanted to paddle and camp for a week.
I use the USGS site almost every day. But since I started paddling more down around the Gulf Coast, I've had to learn some new truths about cfs and stream volume.
Up on the piedmont, and in the mountains, the cfs figure will often tell me whether a stream is big enough and deep enough to paddle. In most of Georgia, for example, if a creek or small river carries at least 300 cfs, it may be comfortable to paddle. A larger, wider river may need more cfs to cover the shallows and shoals. Another rule of thumb I use is that a creek with a 30 square mile watershed area (above the USGS gauge) may be negotiable after a heavy rain, but it's better to have a watershed area well over 100 square miles if you hope to find a stream that's runnable throughout the spring.
You can find watershed area for a particular gauge by going to the pull-down data menu for that stream and clicking on the "location". A wonderful selection of maps will come down, mouse-controlled. And above the map you should see the watershed area in square miles. I used to calculate watershed areas from topos I bought. Now I seldom have to.
Whether a stream has enough watershed area and current streamflow in cfs is knowledge you need to accumulate from experience. Use the USGS data to find out what streamflow you had on your last attempt to paddle a stream. You can often extrapolate from one stream to another, such as from Hatchet Creek to Weogufka in central Alabama. They are similar in size. Hatchet takes 600 cfs for a decent run, and if Hatchet is high enough, Weogufka should be also.
Back to the coast. Rivers with good flow, like the Bogue Chitto, obey roughly the same rules as piedmont and mountain rivers. Smaller streams like Coldwater in Florida probably do too. But I found that for bayous, which often have good channels but very slow flow, the USGS cfs figures do not predict runnability. A bayou might have a 30 cfs flow in a dry period, yet be big enough for outboards. Sometimes when the flow is low enough, the USGS gauge only reports gauge height, not flow, and that's just as well.
As someone quoted an army seargeant, it's the situation and the terrain.
Another factor in the Great Lakes area, and others across the country, are rocks. 12" of water is nice, but when there are 10" rocks scattered about, 24" of water is a lot nicer. And, of course, flow rate says nothing about downed trees across the river. A few years ago we spent over half of our time going over/under/around/through downed trees on the Muskegon River in western Michigan.
If flow rate were stated in percentage of flood stage it would provide even more info. Some rivers, upper Allegheny in NY comes to mind, need more water to be navigable than others. Grandpa Paddler and I dragged a canoe for half the trip there a few years ago.
Yeah, trees and rocks are obstacles one has to learn to predict from experience with similar rivers at similar flows. If there is a decent gradient (descent gradient, perhaps?), then floods may sweep trees out of the way, but at a lower gradient they may "stick" across the channel. The smallest creek I have explored, with a watershed of only about 11 miles, had a 60 ft per mile gradient, and while only two rapids were of significance, periodic flooding had kept the channel clear of trees.
I once ran the Galien River from Warren Woods State Park in SW Michigan down to Lake Michigan. There were a few trees, but fishermen told me that locals had cleared most trees recently. Fifteen years later, I thought to do it again, but when I scouted the bridges, there were many, many trees, and I was told recent storms had toppled them into the channel. I imagine a lot of smaller Michigan rivers would not stay clear unless an outfitter or some sportsmen bothered to clear them occasionally.
Yano, Jack, up there "favorite links" might refer to sausage. I grew up near Chicago, and as a kid, I don't recall ever seeing sausage patties.
We're told not to remove wood from streams by the USFS and the trout fishing groups. But if the wood's an imminent danger, it will disappear. In north Georgia, I've seen small streams where uncreosoted RR ties are staked to the stream bed with rebar. That's supposed to improve fishing, but it ain't natural.
In Michigan's Au Sable river, "Jewel of the North", out Department of Natural Resources (DNR) had the Army National guard choppers lay in whole trees in the river for fish habitat. Problem is, they laid them in on the outside of curves, right were current sweeps unwary canoeists into them. On the inside of the curve would have been much better.