## Flow rate if Oroville Dam aux spillway fails?

## Flow rate if Oroville Dam aux spillway fails?

(OP)

Greetings,

I work on river issues in California. I am trying to figure out how to estimate the potential flow rate if the Oroville Dam auxiliary spillway fails. Can you help?

worst case scenario - the whole spillway fails, creating a 25' x 1450' opening, with 25' of head at first, 25 square mile reservoir. what is the max flow rate out of the dam if failed completely.

more likely scenario - the spillway fails partially, creating ~ 10' x 250' opening, with 10' head at first, 25 sq mi reservoir.

Can someone help with an equation to estimate flow?

I work on river issues in California. I am trying to figure out how to estimate the potential flow rate if the Oroville Dam auxiliary spillway fails. Can you help?

worst case scenario - the whole spillway fails, creating a 25' x 1450' opening, with 25' of head at first, 25 square mile reservoir. what is the max flow rate out of the dam if failed completely.

more likely scenario - the spillway fails partially, creating ~ 10' x 250' opening, with 10' head at first, 25 sq mi reservoir.

Can someone help with an equation to estimate flow?

## RE: Flow rate if Oroville Dam aux spillway fails?

Should be one in the EAP for the dam.

Mike Lambert

## RE: Flow rate if Oroville Dam aux spillway fails?

## RE: Flow rate if Oroville Dam aux spillway fails?

Peter Smart

HydroCAD Software

www.hydrocad.net

## RE: Flow rate if Oroville Dam aux spillway fails?

All in all, looks like it is going to be hard to save the existing spillways and if the erosion starts moving toward the embankment, the whole thing could go. Quite a mess, will be interesting to see why they think the spillway slab failed.

Mike Lambert

## RE: Flow rate if Oroville Dam aux spillway fails?

If you want a rough estimate, just assume a broadcrested weir.

weir coefficient ~ 2.8

typical case

width 250 feet

head 10 feet

Discharge is approx 22,000 cfs

worse case

width 1400 feet

head 30 feet

Discharge is approx 640,000 cfs

## RE: Flow rate if Oroville Dam aux spillway fails?

That sounds right. I did you the weir equation to get a ballpark of absolute worst case scenario - over 400,000 cfs. I think it is more reasonable to think worst likely case is more like 300,000 cfs - which is still double the capacity of the downstream levees.

Thanks, Steve

## RE: Flow rate if Oroville Dam aux spillway fails?

Thank you for those estimates. 640,000 cfs is a frightening number. Fortunately virtually impossible for the conditions to set up that way. Half of that is still a devastating flow for the region - likely inundate well over 150 sq miles, tens of thousands of homes.

Thanks again.

## RE: Flow rate if Oroville Dam aux spillway fails?

## RE: Flow rate if Oroville Dam aux spillway fails?