gauge height and cfs

[jkm001]

Hello, I am stupid. A few weeks ago I did a float on the Big Sugar Creek in Missouri. At that time I thought the creek was a little low, dragging bottom a couple times, having to walk once, and portaging around a low water bridge. The gauge on the creek at that time read 3.5 feet and around 80cfs. Just going by gauge height, I thought 5 feet would provide a better float.

Since then we've had crazy rain. The same gauge went up to around 25 feet with 25,000cfs. It has since come down to about 6ft and 1000cfs.

So, just by looking at these numbers is there a way to tell what is safe to float? Should I be more concerned about gauge height or cfs? Is there some mathematical model that connects gauge height and cfs? On this particular gauge, the height is up 70% from when I floated, but the cfs is up more than 1100%.

I'm just a beginner and wouldn't attempt to float this creek now without talking to a guide first. I also know that while the current may be manageable there is likely a lot of debris that would not be.

Thanks.

http://waterdata.usgs.gov/nwis/uv?07188653" onclick="window.open(this.href);return false;

[Cowper]

There's not any one magic formula we can point you to that relates gage height to cfs, because it depends on the shape and gradient of the river bed and channel near that specific gage. So even if you worked out a formula, it would be a different formula for each creek. USGS types might give a different or more technically complex answer, but for regular folks it is easier to just look at the gage charts and pick which one you want to reference by (height or cfs). Each has advantages, but gage height in feet is the most commonly used by boaters.

Another confusing factor is that each gage has a different "reference point". So while 3 feet on the gage might be just right on one river, it could be not enough on another, and too much on a third. You need to figure out "minimum" and "too high" levels for each individual creek/gage.

If you look at all the gages on the Ozark Whitewater page, it shows the "trigger" points for Low, Optimum, and "High". As you can see, for many gages, "optimum" begins with about 1 foot more water than "minimum". With 3 to 5 feet more water, the creek becomes too high to be safely navigated by most boaters.

So, and this is only a WILD GUESS; if you can't find any better info on line:

Minimum: 3.5 feet
Optimum: 4.5 feet to maybe about 6 feet
High: Above 6 feet (?)

I should also say that the "high" level is the hardest one to pick. It depends on the nature of the river, and your skill level.

[Roy Staggs]

Did a quick search on Big Sugar Creek and found this http://southwestpaddler.com/docs/elkmo4.html" onclick="window.open(this.href);return false;
looking at some of the pictures you will see a couple of low water bridges that I suspect could form very sticky hydraulics at higher water levels.
If the stated 9 fpm max gradient is correct, the thing probably would just be big wide moving flat water at higher levels.
If you plan on getting on at higher water levels, it might pay to check out those low water bridges before you get to them.
Looks like a good place to go fishing. I may have to go check it out.

[Cowper]

Good point on the gradient not being very much; the unknown for me is when does it start flowing fast through the willow trees?

Maybe I should retire so that I too will have the time to do more exploring (YOU DOG).

[jkm001]

I went up to the Elk and Big Sugar today just to look around. The river below the Noel dam still looks a little hairy. Both rivers looked swift, but the portions I saw didn't have too many strainers or root balls.

These are low water bridges on Big Sugar. How worried should a novice in a 12ft recreational kayak be about these? This is with a gauge height of about 6'. At 3.5' they were both about 6" below water so now they're around 3' under and uncrossable except by maybe an Abrams tank.

Crag O Lea



Cyclone

[Cowper]

How worried should a novice in a 12ft recreational kayak be about these?

If you have a spray skirt and hit them straight on, you should make it through. But to really answer your question, we need to know what is downstream of this? Is it something you would feel safe swimming with your boat in tow if you don't make it?

This is one method some use to judge rapids - not "how do I feel about running that?", but, "how would I feel about SWIMMING that?"