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Intellisolve's Hydraflow VS Engenious StormSHEDHelpful Member!(3) 

kswanson (Civil/Environmental) (OP)
6 Mar 08 12:38
Hi, I need to get this situation resolved. I need to verify a stormwater conveyance analysis and I'm puzzled as to why the two models provide different flow capacity values.  A consultant provided me a Hydraflow conveyance model that shows "Cap Full" (Capacity Full I presume?) values are substantially larger than "Full Q" values I modeled in StormSHED.  The Q values that actually flow through each reach are very close for both programs, but the max capacity values dictate whether or not the conveyance model passes the design criteria. His model passes because his capacity values are so high that it will never overtop, but my StormSHED model says that it fails because my capacity values are much lower.  Here are the capacity values for each reach.
StormSHED (cfs)     Hydraflow (cfs)
17.74               32.65
11.45               25.34
6.28                5.25
2.9                 5.33
6.4                 5.35
3.25                7.54
3.68                6.74

It was brought to my attention that StormSHED is a gravity- based program so when it computes pipe full capacity, it's based on gravity, not some surcharge. How does Hydraflow compute "Cap Full" values? I don't have a copy of the program so I can't research it.  Thanks so much for your time.

elev8848 (Civil/Environmental)
6 Mar 08 12:48

Hydraflow uses Manning's equation to calculate full flow capacity. The slope of the pipe is used--not the friction slope. And it is what you get by pencil/paper calculator, too.

Use my if you don't have pencil/paper.

Compare the result for at least one pipe.

Helpful Member!  RWF7437 (Civil/Environmental)
6 Mar 08 17:58
It appears you may be confusing or comparing two different things?

As far as I know, HydraFlow Hydrographs does NOT calculate pipe capacities flowing full. It is primarily a hydrology program. It generates hydrographs and routes them through storage devices; such as ponds, buried pipes or other "chambers". It may be that when it reports "Cap Full" it is telling you the volume of a storage device ( in cubic feet) when it is full, NOT the flow capacity in Cubic Feet per second. This explanation would account for the large discrepancies you note in the data you posted.

To check this; take any two or three pipes in your system and calculate the flow capacity ( cfs) using Manning's Eq. and also calculate the volume if each of those pipes (cf).

Then compare them to the two sets of data you posted.

By the way, Intelisolve has sold out to AutoDesk so Hydrographs 2007 is, sadly, no longer available as a stand alone program. If you do not have a copy, borrow one from a friend or send me your input file.  That'd be rwf7437 AT comcast DOT net.

good luck
kswanson (Civil/Environmental) (OP)
6 Mar 08 18:23
So, what is Full Q and Cap Full supposed to represent?  These values must represent the carrying capacity of the pipe when flowing full. In StormSHED there is even a % Full Ratio column which yields values less than 1 if the pipes meet design criteria.

RWF7437 (Civil/Environmental)
6 Mar 08 18:29
"So, what is Full Q and Cap Full supposed to represent? "

I can't answer your question without seeing what it is you are looking at. It is possible, as I noted, that CapFull means a volume, NOT a flow rate.
RWF7437 (Civil/Environmental)
6 Mar 08 18:36
To check this; take any two or three pipes in your system and calculate the flow capacity ( cfs) using Manning's Eq. and also calculate the volume if each of those pipes (cf).
RWF7437 (Civil/Environmental)
6 Mar 08 20:06
To simplify this just fill in the blanks below:

"StormSHED (cfs) Hydraflow (cfs) Size(in) Slope(%) Length(ft)
17.74               32.65
11.45               25.34
6.28                5.25
2.9                 5.33
6.4                 5.35
3.25                7.54
3.68                6.74
kswanson (Civil/Environmental) (OP)
10 Mar 08 19:49
kswanson (Civil/Environmental) (OP)
10 Mar 08 19:51
here is the word file that shows reach #, flow values, slope, length, and pipe diameter.
RWF7437 (Civil/Environmental)
10 Mar 08 21:04
Here's a partial answer to one of your questions. I spot checked two of the pipes in your system, using neither StormShed or Intelisove's software, with the following results:

"StormSHED (cfs) Hydraflow (cfs) Size(in) Slope(%) Length(ft)
17.74               32.65          36"    0.24        196
3.68                6.74           24"    0.09        349

For these two pipes I get full flow capacities of 32.68 cfs and 6.78 cfs for the 36" and 24" pipes, respectively.  This leads me to conclude that the Intelisolve software is giving you accurate flow results.

What StormShed is telling you is not clear to me. I don't use StormShed but the two files you posted are confusing.

First, it appears that it is NOT Intelisolve's Hydrograph program that is being used but instead it is a different program. It appears to be Intelisolve's Storm Sewers 2008 which is used. I have that program and have used it a little but it does sometimes confuse me. I've found, when using it, that one must be very careful to be certain one is using it to analyze an existing system or to design a proposed system.

"Let me tink on this a little." to quote Einstein.
RWF7437 (Civil/Environmental)
10 Mar 08 21:13
RWF7437 (Civil/Environmental)
10 Mar 08 21:24
Sorry, my mistake.

I meant , have you asked Engenious for an answer ?

At $2,400 per copy O would hope you'd get some tech support!

good luck
RWF7437 (Civil/Environmental)
11 Mar 08 0:05
Other anomalies;

The schematic and tabulation don't seem to make sense.

The tabulation lists two pipes with 0% slopes:
From MH223 to MH260 and
from MH269 to MH03
This is not very likely to be true in a real collection system.
If true, neither pipe can carry any flow. So, how does water get from MH260 to the outlet ?

Two pipes appear to "cross" in your schematic but they don't "connect". That is, no flow goes from one pipe to the other.

Are you sure you have modeled the system realistically in StormShed ? It is just possible that the program will give you an answer even if you've modeled the system incorrectly. That answer, of course, is wrong but that might not be immediately obvious to you. It is also true that many programs do nor do a very good job of trapping such logical errors.

good luck
Helpful Member!  TerryScan (Civil/Environmental)
11 Mar 08 9:34
Check your manning's N values.  I find the full flow values for Stormshed would be valid with an N value of 0.024 (cmp) and the Hydraflow values valid for an N value of 0.013(rcp).
kswanson (Civil/Environmental) (OP)
11 Mar 08 11:53
The reach flowing south to north (MH223 to MH220) is negatively sloped, and the only way the consultant could model it was at a 0% slope (or a 0.001% slope in StormSHED).  Please don't ask me why; that's just the way the system was built. Either that or they measured the inverts incorrectly, but they assured me that the inverts were correct.  One of the issues brought to my attention was the pipe materials were different, and that if I entered in the same pipe material it would yield better results. Problem is, the network uses an array of pipe materials such as CMP, concrete, and plastic.  I had to model the system as it exists.

Yes, a pipe appears to "cross" another; that's because flow is going from CB01 to CB02 to MHO4 then to the Vault then to MH03. Flow is also piped directly from MH223 to MH260. The Vault represents a StormFilter device to satisfy oil control BMP requirements.

The consultant provided me this model.  Whether or not it makes logical sense is another issue.  smile

The area between MH04, MH05, CB06, CB07b, and CB07 is going to be widened by one lane (I should've raised CB07b and CB07 up on the schematic a little more so they would be in line with the other drainage structures); anyway, they are interested in hooking that area up to the existing conveyance system.  
I can add in the inverts if you like.  Here, why don't I just give you the StormSHED model and you can take a look at it.  Everything I entered in StormSHED was the same as what the consultant provided me in the Hydraflow model. The thing that perturbs me is that I don't believe the consultant is using the right inverts; I think he is fudging them to make his model work.

kswanson (Civil/Environmental) (OP)
11 Mar 08 11:57
yes, we spoke with Engenious, and they weren't familiar with the inner workings of Hydraflow.  We need to speak with someone who is knowledgeable about Hydraflow models. That's why I posted here, hoping that somebody could answer my question.  At least I'm getting some responses!  Thanks so much! smile
RWF7437 (Civil/Environmental)
11 Mar 08 14:47
TerryScan seems to have discovered one of the problems you are having.

The Intelisolve programs are no longer available as standalone  programs and are, sadly, no longer supported by them. They have been sold to Autodesk and are now part of that company's offerings. Whether or not Autodesk can or will help, it might be worth trying to contact them.

good luck
RWF7437 (Civil/Environmental)
12 Mar 08 19:20
Without running a complete analysis of the system you've described, it appears that the design will probably work. Despite the fact that there appear to be errors in the Hydraflow output, the last line in the system, a 36" CMP pipe ( n=.024)at a slope of 0.0024 with a free outlet has a capacity of 17.7 cfs. From your previous posts you say your design flow values agree closely. According to your schematic the design flow into this 36" pipe is only 12.4 cfs. This is 30% less than the capacity so the outlet pipe should be adequate.

There may be pipes in the system which are surcharged under your assumed design conditions. The two pipes with reverse grade, especially, would be of concern. Whether or not these are existing is not clear from the information you've provided. It may be possible to replace these pipes but that too is unclear.

If the question is "should this system be approved?" then the answer appears to be yes. If some existing pipes should be replaced, that is a separate question. If the questions are something else, tell us what they are please.

good luck
kswanson (Civil/Environmental) (OP)
13 Mar 08 11:21
You stated, "Without running a complete analysis of the system you've described, it appears that the design will probably work. Despite the fact that there appear to be errors in the Hydraflow output, the last line in the system, a 36" CMP pipe ( n=.024)at a slope of 0.0024 with a free outlet has a capacity of 17.7 cfs."

The data you typed is from my StormSHED model, not the hydraflow model. The last item attached in this thread was the StormSHED model data.  I don't have the hydraflow model data output available in digital format.  Previously, I attached a word document comparing the two programs but it wasn't labeled properly. Here is a better attachment you can look at.

The information for the last reach should be as shown in this attachment:
StormSHED- design Q: 12.4062 cfs  max Q: 17.7468 cfs    
Hydraflow- desigh Q: 15.92 cfs  max Q: 32.65 cfs    
reach length- 196.1 ft        
pipe size- 36 in        
slope- 0.24

Now, my biggest problem will be the mannings N values.  Again, the pipe material used in the conveyance system is composed of different materials.  I can't just use one mannings N value for the entire conveyance system because it wouldn't accurately represent the real-life situation.  

Thanks, RWF! Your assistance is greatly appreciated!

FYI- I drove to the site on the night of the big flood in the Chehalis area back in Early December (this site is in Longview but it was raining just as hard) and I did not notice any flooding or overtopping of the roadway.  It appeared the conveyance design worked then. They are adding some additional impervious surface, but not enough in my opinion to warrant concern over conveyance system failure.  The stormwater discharges into a diking system.  I don't know if that would make a difference or not.
Helpful Member!  bank (Civil/Environmental)
17 Mar 08 18:38
I think your attachment has the columns labeled incorrectly. I use Hydraflow Storm Sewers quite a bit, and have never seen columns labeled "Full" and "Full Q". On the other hand, Hydraflow does have the columns "Total Flow" and "Capac Full" in their report printout.
Hydraflow will through you a curve now and then so it behooves one to check the results carefully. Reach No. 3 on your attachment, between MH224 and MH223 appears to have an erroneous number somewhere. At 0.52% with an assumed n value of 0.013 a 12" pipe will have a capacity of 2.57 cfs. Could that possibly be a 36" pipe (Q=48.10)instead?
kswanson (Civil/Environmental) (OP)
24 Mar 08 12:23
I did mislabel the StormSHED and Hydraflow columns.  Thanks for pointing that out to me.  The labels need to be switched.  And yes, the reports do indicate that the pipe is 36" diameter.  I had to retype the information in Word, so mistakes do happen. It would be nice to have both a hard copy and a digital copy of the report so I could copy and paste the data into Word.

It would be nice to find out why the Full Q and Cap Full values differ so much with both programs.  Any ideas as to why this happened?
bltseattle (Civil/Environmental)
31 Mar 08 16:47
Stormshed accounts for tailwater conditions, as I recall, which would yield lower pipe capacities than free-flowing pipe outlets - especially since you have some very flat pipes (S<0.5%)
mjwoodruff (Civil/Environmental)
11 Apr 08 9:02
I read in the Civil 3D stormwater discussion group that Hydraflow recently updated it's modeling of pipe flow. I would check that forum, because people were getting different flows even between version of Hydraflow.

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