Dynamic Modeling 2

[pcgarner]

Many states are beginning to move toward requiring hydrologic software that "dynamically" models a given network or watershed. For instance, Massachusetts may require such analysis when it releases its new regs for stormwater management late this year.

Can HydroCAD respond to this? Any proposed changes in the works?

Patrick C Garner Co., Inc.
Northborough, MA

 

[psmart]

I'm not sure what you mean by "dynamic".

If you're referring to the ability to handle tailwater effects, this can be done by selecting the correct routing procedure. For details please see

http://www.hydrocad.net/dsi.htm

 

[pcgarner]

Peter,
See the latest CE News (July 07), page 35. Seeing that article prompted me to ask. They refer to two tiers of software, one that is a "fully valid hydraulically dynamic model," and one that is a "simplified routing method." My understanding is that HydroCAD is the latter, but as I noted initially, many states are beginning to edge toward requiring the former.

Regardless, the terms are new enough that I'm uncertain where HydroCAD fits in. Thanks--

Patrick C Garner Co., Inc.
Northborough, MA

 

[RWF7437]

Mr. Garner,

Is it possible to ask the State of MA, or any of the other States considering such a requirement, to provide a list of acceptable software and an example or two of how they expect to use such programs ? The US EPA publishes such a list for floodplain studies, as you probably know.

I know it is a lot to ask but I thought I'd try.

good luck

 

[pcgarner]

I work in Massachusetts and sit on a DEP technical advisory committee for stormwater. A subcommittee has been working on that issue, & is expected to release final recommendations in the fall. Whether they will list "approved" software is doubtful, as that hasn't occurred in the past.At this point I'm waiting on more detail, but preliminary presentations have emphasized the need to shift to "dynamic" modeling (vs TR20 & TR55-type programs).

Patrick C Garner Co., Inc.
Northborough, MA

 

[RWF7437]

Thanks for the disappointing information. O knew it was too much to ask. I'll wish for a pony next time.

 

[psmart]

For your consideration:

While dynamic modeling may be needed in some cases, requiring it on a wider basis will lead to all sorts of problems, including lack standards, minimal software availability, lack of experience by engineers and reviewers, difficulty in doing hand-checks, etc.

While it may seem better in theory, you need to do a real cost/benefit analysis before mandating such a change. Over the past 25 years, localities that have decided to use locally-developed modeling techniques have isolated themselves from the large pool of engineers and commercial software that are available for more standardized techniques. Even if a new procedure is better in theory, you have to weight this against the inevitable errors and costs of a less-known approach with an unproven track record.

 

[pcgarner]

I'll let you know how this plays out as I learn more... Thanks.

Patrick C Garner Co., Inc.
Northborough, MA

 

[RWF7437]

Yes Mr. Garner,

Please do keep us informed.

And also, when you can, please clarify what the State of MA thinks "dynamic routing" is. As far as I recall neither TR-20 or TR-55 is a "routing program" at all. Both merely calculate a runoff hydrograph from a known, or assumed, rainfall pattern. Neither provides a way to route the resulting hydrograph through a system of ponds, pipes, channels or other hydraulic structures. Indeed, it is hard to understand what the difference might be between a "dynamic" program and a "static" one. If water is moving in the program it would be called dynamic, wouldn't it ?

 

[pcgarner]

A quick update: I just read the latest "draft" release by Massachusetts DEP on the new stormwater management regs & there's no discussion of "dynamic" modeling other than in a new section on exfiltration calculations. So it's back to the usual TR20 & TR55 methodologies.

Patrick C Garner Co., Inc.
Northborough, MA