# Cubic feet to miles per hour

Discussion in 'MISSOURI RIVERS TALK' started by fishingbuddy4, Jul 30, 2007.

1. ### fishingbuddy4New Member

Messages:
1,564
State:
Warner Rob ga
Wanting to see if anyone knows how to change cubic feet per second to miles per hour? Looking to make a float trip on the missouri and need to know how many mile i can float in a day

Messages:
524
State:
Ohio
Depends on the volume of the river you are flowing into.

Have to know the width and depth, and then assume they are constant, then you can approximate current flow.

3. ### Mr.TActive Member

Messages:
2,554
State:
MO
There's no relation between the two.

The speed of the river is determined by the gradient (how far the elevation drops per mile) and the volume of water flowing. I doubt there's a simple way to calculate velocity even if you knew both of those things.

If you have a GPS, get on the river, kill the engine and watch your speed for 15 or 20 minutes. That should give you a reasonable idea, at least as long as the river level

4. ### BKS72New Member

Messages:
3,361
State:
East of KC
The COE says it averages 3-6 MPH on the Missouri River. 3.5 is probably a safe number as it's what I usually come up with when floating and watching the GPS. That number has been pretty constant everywhere I've fished it from Lexington to the confluence at current river levels. I've seen around 4.5 on some outside bends where the river's narrow. If you're using that 3.5 number for planning a float trip, you may want to reduce it some to account for wind in the wrong direction which might slow you down.

5. ### hovis223New Member

Messages:
11
State:
missouri
the conservation department has a detailed map book you can buy that tells you the elevation drop per mile if you tell me which river and which stretch your looking at i can tell you the drop.

6. ### TeamWhiskersNew Member

Messages:
536
State:
Missouri
Just time what it takes between the green channel markers and figure from there.

7. ### cougarNew Member

Messages:
29
State:
Green Ridge, Missouri
If its any help, we floated it from I-70 to Hartsburg last year after the navigation season. The gage at Boonville said 4.2ft and we were floating into the wind. It took on average 24min to float a mile, but if you remember that was when everyone was having a hard time finding a boatramp that was still in the water. During the navigation season this year it is averaging 7ft.

8. ### smhmc6Member

Messages:
744
State:
Kansas
To convert a volumetric flow rate to a velocity, you would need to know the exact cross sectional area of the river at each place you want to know the velocity. V=Q/A ( V is velocity, Q is volumetric flow rate, and A is cross-sectional area). If the cross sectional area is smaller, like a bottleneck it acts as a nozzle and the flow is faster. The volumetric flow rate stays the same but the velocity will change depending on how deep, wide, and many other things. However, if you look at my picture, it will give you a rough estimate at least. It isnt going to be exact by any means but I bet its close within +/- 5 mph. So you can probably add 5 mph to be conservative. First you gotta estimate how wide you think the river is and how deep you think it is. Also the shape of the bottom matters as you can change how many triangles you have and all that, but this is pretty basic.

Heres how you get it:

You already know the flow rate, now all you gotta know is an estimate for the cross-sectional area. The area of triangles 1 and 3 combined is D*W/2 (D is depth, W is total width of the river). The area of the rectangle is obviously W/2*D and add them together you get A= D*W. If you think you have a different bottom shape, like I said, you can just add more triangles or different shapes and add the areas together.

So, now you know the area roughly. So the velocity V=Q/(D*W). The only think you have to worry about is that its in the same units that you want like Q is in cubic feet per second and D and W are in ft. you get ft/second. Then to convert from that to mph you divide by 5280 and multiply by 3600.

Final equation for the shapes in my picture if D and W are in ft. and Q is in cfs is:

V (in mph)=3600*Q/(5280*D*W)

Like I said, rough approximation but sometimes thats all you need. Hope this helps!

9. ### smhmc6Member

Messages:
744
State:
Kansas
Sorry, had to make my picture into a JPEG to get it to work. Here it is

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10. ### fishingbuddy4New Member

Messages:
1,564
State:
Warner Rob ga
Thanks guys ,guess the best way is just hit the river and try it

11. ### osageNew Member

Messages:
38
State:
Grain Valley Mo.
Did anybody understand what Steve said?oooh: LOL I always felt like I was somewhat smart. Now I feel like the slow kid from grade school. Wow, my brain hurts.

12. ### SkipEyeWell-Known Member

Messages:
7,525
State:
Winfield, MO
Name:
Darryl
Jason,

Of course we all understand what Steve said.:0a10:

You are the only person who doesn't understand, to the end of the line with ya.

I think he said he was going to college to be an engineer or something. Almost about to graduate even.

Heck, the rest of us Boccer's finished that schooling up years ago.

YUP! Sure did! Easy stuff!:0a26:

13. ### TN GregMember

Messages:
627
State:
MO
I still can't get over how big that fish is............

14. ### SkipEyeWell-Known Member

Messages:
7,525
State:
Winfield, MO
Name:
Darryl
Greg, theres a 'formula' for BIG fish, you know that. Ask Steve will ya? Geez!:tounge_out:

15. ### TN GregMember

Messages:
627
State:
MO
Good point. This is kind of like the smallmouth and walleye world records that they are trying to take away from my home state of TN based on old photographs, but just the opposite. If we can get someone to really analyze that picture, I bet Robert has a line class record or something. Steve, are you a guru with such analysis capabilities?