AutoCAD Civil 3D - Stormwater

[#1]

It's my first time using SSA, and I'm finding the program definitely has it's share of quirks - I'm not sure I'm sold on it yet.

I had finally created a network and storm that I thought was working properly (using TR-20 routing with an SCS II storm), until I took a closer look at the profile outputs - and noticed that the graphed Max HGL line does not match the Max HGL listed in the table below.  The difference was 856.2 on the graph and 858.01 on the table at one my structures, for example.  Does anyone know why this is?  Which is incorrect?  How to fix it?

The ability to import pipe networks is nice in SSA, but if the output data is always this wacky I may have to go give up on SSA and go back to using Hydrocad.

--Jeremy

[#2]

Jeremy -

The report will be the maximum HGL over the time of the analysis based on the time steps in the reporting step.

The profile will show the HGL at the current time.  I would suggest looking at the Output animation.  In other words - the profile is showing a time-variable HGL and the report is showing you the maximum.

You can review each structures time-varying HGL in the time series plot as well.

[#3]

Thanks.

I found out by trial and error it's actually more complicated than that - but I think I found the solution:

You need to be sure the "reporting" interval is the same as the "routing" interval.  I had 1-minute routing intervals but 10-minute reporting intervals.  The table was then showing the max HGL from the 1-minute interval, but the graph showed the max from the 10-minute interval.  Apparently the peak was midway between the two 10-minute intervals, so there was a substantial difference between the values.  After I made the reporting interval also 1-minute, the data aligns much better.

--Jeremy

[#4]

Jeremy -

Yes, that would also provide different answers.  By having the taken only ten-minute reporting interval, you are dismissing 9 possible other points within a 10-minute window that could show a peak.

That is why I answered originally with

"The report will be the maximum HGL over the time of the analysis based on the time steps in the reporting step."

Hope that helps.

[#5]

Thanks.

Of course this leads to the question:  "Why even have two boxes for intervals if they must always be set the same?"  I was trying to reduce the raw data in a table, but I had hoped that the Max HGL would come from the routing data, not the reporting data.

May I also ask what routing-reporting interval you typically use?  Have you found a good balance between accuracy and computational speed?

Jeremy

[#6]

Jeremy -

There are two ways to answer that question;

1.)  Because we support EPA SWMM import/export which allows the variables to be different. 

2)  One isn't always seeking a design level [In model calibration we may have reported intervals that we are attempting to match, yet we want smoother hydraulic routing calculations,

What do I use? Depends on model size and method - rationals 1 min reporting / 30 sec routing;  SCS 5 min reporting/1 minute routing are typical. 

[#7]

I'm so sad.  I had such high hopes for SSA.  It looked so amazing.

Unfortunately my last fix didn't fix everything.  Some nodes look OK, but others still have differences of several feet between the Max HGL shown on the graph and the Max HGL shown on the table.  I've matched routing and reporting times, and even looked at the reports per minute to compare them with the graphs per minute.  They are showing completely different values.  Why the tables are using a different formula from the graphs I don't know, but at least one of them is obviously wrong.

Oh well, I'm done alpha-testing the program.  It's broken.  I'm going to uninstall it from my system now.  Back to the old way.

Jeremy

[#8]

Jeremy -

That is a quick dismissal of the software.  Could you have missed something? Do you want help?

Have you opened a service request with Autodesk Support? They are there to help.

Have you posted your model here to the discussion group so that we can assist?

SSA contains a lot possible settings - from the profile plots to the routing time steps, to hydraulic modeling parameters.  It's hard to telll what is up with the model.

If you want, email me the file and I can take a look.  matt dot anderson at autodesk dot com

[#9]

I have been having the same issue as Jeremy. I have looked at and matched reporting/routing intervals. I have attempted to replace the junction node 105 as well as replaced the connecting pipes. (also same issue with Jun-74)I have also tried different invert elevations and rim elevations with no luck. I hope that someone could please look at this model and see if you can fix this issue. Thank you and please see attached.

Please note - The forum does not allow me to attach my model. I get the warning that it does not support .spf file extensions. Ideas?

[#10]

Just rename the file to something different, i.e., use .txt in lieu of .spf and note the change.

Bill