GEOPAK Drainage error message

Re: GEOPAK Drainage error message

Robert Garrett — Fri, 06 Feb 2009 04:28:24 GMT

Josh

We have partially identified the problem. This error only occurs when the intensity works out to zero which means that the Tc works out to zero. Something odd is happening when you use the weighted method that is forcing you into this odd situation. We are in the trail to debuggin the network so we can track where the zero is popping out and then we can hopefully discover where (if any) the error in the drainage network lies.

In the mean time you should be bale to proceed with the weighted checkmark turned off without any ill effects. If your reviewing agency requires the weighted calculation then, hopefully we can finish the debug process before you have to submit any reports for review.

Re: GEOPAK Drainage error message

Josh M — Fri, 06 Feb 2009 02:29:48 GMT

Robert,

Thanks. You will find a zipped folder on your ftp site. I appreciate your time.

Josh

Re: GEOPAK Drainage error message

Robert Garrett — Fri, 06 Feb 2009 02:00:30 GMT

Josh - This just in from the original developer of the drainage program.

" If he is using the weight TC option, we might need to find out if he has some huge discrpancy in the areas and c values that is screwing up this weighting."

If you are inclined to then send me your DGN, GDF & drainage library. I will also need the GPK if any nodes are based off an alignment along with tin/gsf files and superelevation DGN file if they are used.

You can post on ftp://ftp.bentley.com/pub/incoming if they are too big for email

Re: GEOPAK Drainage error message

Josh M — Fri, 06 Feb 2009 01:46:59 GMT

Dan,

Thanks for your help. I took a look at my file using your/other's suggestions. Here is what I have concluded:

An Area report shows all Tc's used to be between 5 and 15.2 minutes - Seems OK, but error message still appears.

Links From and To node Cumulative Tc report show Tc' s of between 5 and 15.77 minutes - Seems OK, but error message still appears.

My normal preferences use the "Weight Time of Concentration" under Intensity Options. If I uncheck this and then design my network, the error message goes away. However, then I don't think my results are correct.

Any suggestions?

Josh

Re: GEOPAK Drainage error message

Dan Calistrat — Thu, 05 Feb 2009 23:28:06 GMT

Well in Texas, 14 thousand minutes isn't a long time to wait for it to rain... ;-)

But if your Tc is actually less than 5 minutes or more than 10 days, the easiest way to locate it is run the Report Builder and output the Tc values into a csv file, then use Excel to highlight the times outside that range.

Based on Robert's suggestion, output the Area variables to check that a drainage area isn't the offender. Based on what Alex says, ouput the Links's "From Node" and "To Node" cumulative Tc values as the offending Tc value could be inside a pipe or ditch.

Sometimes we use "fake" areas just to get a link or node connected to the system and we have to use a Q=.001cfs, if we forget the to leave that in and design/analyze the network the resulting Tc is huge. An excel conditional formatting statement should highlight the offender for you.

Re: GEOPAK Drainage error message

Josh M — Thu, 05 Feb 2009 20:17:19 GMT

Derricke and Robert,

My library has times of 5 minutes to 14400 minutes (10 days), so I don't think that is the problem. I will try Robert's suggestions to pinpoint the problem.

Thanks for your help,

Josh

Re: GEOPAK Drainage error message

Robert Garrett — Thu, 05 Feb 2009 18:47:11 GMT

Josh

Yes you should be concerned since this indicates that one or more nodes is probably receiving an invalid flow. If you can't find the rogue then you should submit a support call to track down the problem. You can send me your data but it might take me a a few days to get a chance to look at it.

Here's a hint that I would try first: For each drainage area go to the computations tab and click the compute button. See if the reported flow is a reasonable number. If one of the computations looks too large or too small then investigate this area more closely.

Another idea: Are you using the automatic Cvalue computations to determine a weighted C from multiple sub areas? Iwonder (guessing really) what would happen if one of the subareas was extremely tiny??????

Re: GEOPAK Drainage error message

derricke.gray — Thu, 05 Feb 2009 18:39:29 GMT

Josh,

I'm not a drainage expert but I asked Alex Mabrich and this is what he said:

"The time of concentration is not only for the drainage areas but it gets accumulated as runoff travels inside the pipe. E.g. Drainage area A starts with 5 minutes and thru a piping system travels to another inlet/drainage area B for 15 minutes. Then, the new time of concentration to calculate the intensity for drainage area B is 15 minutes.

If the system is too long, it could happen that the travel time/time of concentration falls outside the intensity table definition. Please, check the table since Agencies usually provide this tables and the time axis is quite enough."

Derricke