Still Learning & Need Help-----

[Apakrat]

This is probably a simple hydraulics 101 problem but my 75 year old brain is totally blank on how to estimate the flow velocity of water given only the average slope of a river bed and average water depth.

Any suggestions using calculations with simple algebra formulas?



At 74th year working on IR-One2 - - UHK PhD - - -

 

[Ryb01]

For simple hydraulics, mannings equation would be your best bet. The depth of flow portion of the calculation would be factored into the area component of the equation.

 

[bimr]

You can use one of the online calculators to estimate flow:

http://www.flowsizer.com/

 

[Apakrat]

Thank You Good People



At 74th year working on IR-One2 - - UHK PhD - - -

 

[beej67]

If you can approximate the river as a trapezoidal channel Manning's Equation will give you a good first stab at it, but take some pains to try and get your roughness coefficient right. Also do realize that if the river either changes slope near to your point of interest or there's an obstruction near your point of interest then the normal flow depth assumption won't really be right.

If it's an unusual cross section you can still use Manning's but it's a harder process. If it's very unusual, or you're dealing with overbank flooding and whatnot, just download HEC-RAS and build yourself a little reach in your model and see what it tells you.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[beej67]

Oh, one other thing, be aware with Manning's you're dealing with average velocities. If you're trying to figure out the velocity of a particular streamline in the river then it's more complicated. Water in the middle flows faster than near the banks / etc.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[Apakrat]

Thanks beej67

Useful addition information


At 74th year working on IR-One2 - - UHK PhD - - -