SWMM-USERS Digest - 24 Apr 2012 to 26 Apr 2012 (#2012-43)

[SWMM-USERS automatic digest system]

There are 3 messages totaling 213 lines in this issue.

Topics of the day:

1. Dual Drainage with traplows (3)

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Date: Thu, 26 Apr 2012 16:06:59 -0600
From: "Schafer, Tyler" <Tyler....@STANTEC.COM>
Subject: Dual Drainage with traplows

We are currently modeling some dual drainage systems, with major segments and minor segments.

If we look closely at a drainage subcatchment draining down a street to a traplow where there are catchbasins that allow flow into the minor segment, and excess overland flows pond in the street (major segment) and then spill over and continue down the street to the next traplow.

We are running a dynamic model with Horton infiltration.

We are currently comparing results from PCSWMM to other modeling programs. Looking closely at our PCSWMM storage node, we have created a tabular storage curve based on the street segment and slopes, in order to portray what the street actually looks like. With the streets (major segments) modeled as irregular conduits connecting traplows to other traplows, with high points and low points, for when looking at a profile view, it looks just like a street in a subdivision. The results that we are finding are that our storage node is storing the right amount of water based on the curve we gave it, but the streets (major segments/irregular conduits) are also storing water, as it ponds and backs up from the storage unit, which is technically doubling up on our storage, which creates less overland flow that should spill from this traplow.

Does anyone have any thoughts or experience with a dual drainage system that have traplows for ponding?


Thanks,
Tyler Schafer



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Date: Thu, 26 Apr 2012 16:27:58 -0600
From: Robert Dickinson <Robert.E....@INNOVYZE.COM>
Subject: Re: Dual Drainage with traplows

HI Tyler,

The name trapflow seemed familiar so I looked it up and found this earlier thread that discusses trapflows http://www.chiwater.com/BBS/forums/thread-view.asp?tid=3569&start=1

A SWMM node has an area that is the combination of the actual storage node area and usually 1/2 of the area from the connecting links. If you have a storage node with the surface area of the street and the streets as well you will have too much storage.

Robert Dickinson
Innovyze Inc.
9340 Pontiac Drive                Tel:     813-712-0664
Tampa, Florida USA 33626       
robert.d...@innovyze.com
www.innovyze.com


-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@LISTSERV.UOGUELPH.CA] On Behalf Of Schafer, Tyler
Sent: Thursday, April 26, 2012 6:07 PM
To: SWMM-...@LISTSERV.UOGUELPH.CA
Subject: [SWMM-USERS] Dual Drainage with traplows

We are currently modeling some dual drainage systems, with major segments and minor segments.

If we look closely at a drainage subcatchment draining down a street to a traplow where there are catchbasins that allow flow into the minor segment, and excess overland flows pond in the street (major segment) and then spill over and continue down the street to the next traplow.

We are running a dynamic model with Horton infiltration.

We are currently comparing results from PCSWMM to other modeling programs. Looking closely at our PCSWMM storage node, we have created a tabular storage curve based on the street segment and slopes, in order to portray what the street actually looks like. With the streets (major segments) modeled as irregular conduits connecting traplows to other traplows, with high points and low points, for when looking at a profile view, it looks just like a street in a subdivision. The results that we are finding are that our storage node is storing the right amount of water based on the curve we gave it, but the streets (major segments/irregular conduits) are also storing water, as it ponds and backs up from the storage unit, which is technically doubling up on our storage, which creates less overland flow that should spill from this traplow.

Does anyone have any thoughts or experience with a dual drainage system that have traplows for ponding?


Thanks,
Tyler Schafer



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Date: Thu, 26 Apr 2012 16:45:01 -0600
From: Ben Urbonas - Personal <b...@URBONAS.ORG>
Subject: Re: Dual Drainage with traplows

Tyler,

I would like to add few thoughts to what Robert said.

This is a common problem with modeling storage connected with open channels
or large conduits. You get double flow volume routing. I pointed that our
couple years ago under this forum.

You may want to eliminate the storage node/function or at least reduce it to
an insignificant size to avoid this. Another way, if travel time is of
little conquered, you can use dummy links to connect the surface storage
units. In other words, you have to gimmick around this problem.

Unfortunately, most SWMM or other dynamic routing software users do not
account for this mathematically induced extra routing and accept answers,
often resulting in undersized storage units, whether they are trapflow units
you are using, detention basins of large reservoirs. I discuss this topic
in some detail at all the SWMM-related classes I help teach here in Denver.

Ben Urbonas
(H & F) 303-765-0155
(M) 303-728-4449

-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@LISTSERV.UOGUELPH.CA] On Behalf Of
Robert Dickinson
Sent: Thursday, April 26, 2012 4:28 PM
To: SWMM-...@LISTSERV.UOGUELPH.CA
Subject: Re: [SWMM-USERS] Dual Drainage with traplows

HI Tyler,

The name trapflow seemed familiar so I looked it up and found this earlier
thread that discusses trapflows
http://www.chiwater.com/BBS/forums/thread-view.asp?tid=3569&start=1

A SWMM node has an area that is the combination of the actual storage node
area and usually 1/2 of the area from the connecting links. If you have a
storage node with the surface area of the street and the streets as well you
will have too much storage.



Robert Dickinson
Innovyze Inc.
9340 Pontiac Drive                Tel:     813-712-0664 Tampa, Florida USA
33626 robert.d...@innovyze.com www.innovyze.com


-----Original Message-----
From: SWMM-USERS [mailto:SWMM-...@LISTSERV.UOGUELPH.CA] On Behalf Of
Schafer, Tyler
Sent: Thursday, April 26, 2012 6:07 PM
To: SWMM-...@LISTSERV.UOGUELPH.CA
Subject: [SWMM-USERS] Dual Drainage with traplows

We are currently modeling some dual drainage systems, with major segments
and minor segments.

If we look closely at a drainage subcatchment draining down a street to a
traplow where there are catchbasins that allow flow into the minor segment,
and excess overland flows pond in the street (major segment) and then spill
over and continue down the street to the next traplow.

We are running a dynamic model with Horton infiltration.

We are currently comparing results from PCSWMM to other modeling programs.
Looking closely at our PCSWMM storage node, we have created a tabular
storage curve based on the street segment and slopes, in order to portray
what the street actually looks like. With the streets (major segments)
modeled as irregular conduits connecting traplows to other traplows, with
high points and low points, for when looking at a profile view, it looks
just like a street in a subdivision. The results that we are finding are
that our storage node is storing the right amount of water based on the
curve we gave it, but the streets (major segments/irregular conduits) are
also storing water, as it ponds and backs up from the storage unit, which is
technically doubling up on our storage, which creates less overland flow
that should spill from this traplow.

Does anyone have any thoughts or experience with a dual drainage system that
have traplows for ponding?


Thanks,
Tyler Schafer



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End of SWMM-USERS Digest - 24 Apr 2012 to 26 Apr 2012 (#2012-43)
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