AutoCAD Civil 3D - Stormwater

AutoCAD Civil 3D - Stormwater

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New Member
jab1776
Posts: 1
Registered: ‎10-30-2008
Message 1 of 6 (592 Views)

HydraFlow warning: Outflow greater than inflow

592 Views, 5 Replies
10-30-2008 06:10 AM
When I try to run my hydrographs through a pond I get an error stating something to the effect of: Outflow greater than Inflow on Hydrograph 6 for the 50-yr storm.

How can this be? How can the outflow be greater than what is flowing into it? Has anyone else recieved this before? This is not much of a hold up for me, but I was just wondering how the program can calculate this.
Contributor
TerryStringer
Posts: 22
Registered: ‎12-18-2007
Message 2 of 6 (592 Views)

Re: HydraFlow warning: Outflow greater than inflow

10-30-2008 09:40 AM in reply to: jab1776
This can happen when routing hydrographs with extremely small flows. Basically rounding errors. Try changing the Time Interval of the inflow hydrograph(s) to something either larger or smaller.
*Laurie Comerford
Message 3 of 6 (592 Views)

Re: HydraFlow warning: Outflow greater than inflow

10-30-2008 02:09 PM in reply to: jab1776
Hi jab1776,

The whole idea of a detention basin is that the outflow is delayed and
ALWAYS eventually the outflow will exceed the inflow. If you don't
reach the stage where outflow exceeds inflow, then you must be designing
something else.

Regards


Laurie Comerford

jab1776 wrote:
> When I try to run my hydrographs through a pond I get an error stating
> something to the effect of: Outflow greater than Inflow on Hydrograph 6
> for the 50-yr storm. How can this be? How can the outflow be greater
> than what is flowing into it? Has anyone else recieved this before? This
> is not much of a hold up for me, but I was just wondering how the
> program can calculate this.
Active Contributor
tspoon005
Posts: 29
Registered: ‎07-19-2011
Message 4 of 6 (464 Views)

Re: HydraFlow warning: Outflow greater than inflow

08-06-2012 12:04 PM in reply to: jab1776

True, but I think the number in question was the peak flow, not the flow at any one point.  I have been receiving the same message and I believe it has something to do with Hydraflow screwing up whether or not things should be controlled by inflow or outflow.

 

Although I believe I have diagnosed the problem, I have yet to find a solution and am curious if anybody else has found one.

 

Thanks.

Employee
Matt.Anderson
Posts: 2,909
Registered: ‎05-13-2005
Message 5 of 6 (458 Views)

Re: HydraFlow warning: Outflow greater than inflow

08-06-2012 01:18 PM in reply to: jab1776

A bit of an old post, but Terrys answer is correct.

Matthew Anderson, PE
Product Manager
Distinguished Contributor
annw2
Posts: 1,274
Registered: ‎03-07-2006
Message 6 of 6 (426 Views)

Re: HydraFlow warning: Outflow greater than inflow

08-28-2012 05:34 PM in reply to: jab1776

Usually this happens with a small flow & large weir.  A weir is usually the highest , ie. 100 year discharge.  With the flow dependant on H^1.5 you can go from 1 cfs discharge to 10 cfs discharge with a 0.01 ft increase in head.

 

Set your weir length for 100 year storm down to something very small, such as 0.5 or 1 ft weir length and see if you still get the error.

Ann Wingert, P.E.
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