Environment, Coasts, Oceans, & Infrastructure

Hello Everyone,

I can't remember where I heard it, but at the Congress I heard a brief mention about somebody or some task committee working on/interested in developing curve numbers for either green infrastructure or low impact development. Did I hear that correctly? Is there a group working on this? If so please let me know, and maybe provide a very brief overview of the work that is being done. Thank you!

 - Glenn

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Glenn Moglen Ph.D., P.E., F.EWRI, F.ASCE
Professor and Laboratory Director
Virginia Tech
Manassas, VA 20110
(703)361-5606 EXT 142
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Hi Glen,

Nashville's manual has good explanation of how they calculate adjusted curve numbers for retained volume (see section 3.2.5) https://www.nashville.gov/Portals/0/SiteContent/WaterServices/Stormwater/docs/SWMM/2016/Vol5LID/2016_FullVol5LIDManual.pdf

--Rebecca

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Rebecca Stack A.M.ASCE
Deputy Executive Director
Washington DC

Talk to Karen Karvazy

Sent from my iPhone

------Original Message------

Hello Everyone,

I can't remember where I heard it, but at the Congress I heard a brief mention about somebody or some task committee working on/interested in developing curve numbers for either green infrastructure or low impact development. Did I hear that correctly? Is there a group working on this? If so please let me know, and maybe provide a very brief overview of the work that is being done. Thank you!

 - Glenn

------------------------------
Glenn Moglen Ph.D., P.E., F.EWRI, F.ASCE
Professor and Laboratory Director
Virginia Tech
Manassas, VA 20110
(703)361-5606 EXT 142
------------------------------

Hi Glenn,

I don't know about that study but here is some relevant information. Several years ago I Developed equations and charts to evaluate allowable Curve Number reduction of impervious and pervious areas due to implementation of various LID techniques. Here is the reference to it (it should be available online):

Zomorodi, K. 2004 “Curve Number and Groundwater Recharge Credits for LID Facilities in New Jersey”, Proceedings of the Conference “Putting the LID on Stormwater Management!” The Inn and Conference Center- Marriott, College Park, Maryland, September 21-23, 2004. Proceedings published electronically on a CD, to reach this paper on the CD first select “Program and BIOS” and then “Read BIOS and papers”. pp. 508-514.

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Kaveh Zomorodi, Ph.D., P.E., M.ASCE
Senior Hydrologist
Dewberry
Fairfax VA
(703) 849-0336
kzomorodi@...

------Original Message------

Hello Everyone,

I can't remember where I heard it, but at the Congress I heard a brief mention about somebody or some task committee working on/interested in developing curve numbers for either green infrastructure or low impact development. Did I hear that correctly? Is there a group working on this? If so please let me know, and maybe provide a very brief overview of the work that is being done. Thank you!

 - Glenn

------------------------------
Glenn Moglen Ph.D., P.E., F.EWRI, F.ASCE
Professor and Laboratory Director
Virginia Tech
Manassas, VA 20110
(703)361-5606 EXT 142
------------------------------

------Original Message------

Hello Everyone,

I can't remember where I heard it, but at the Congress I heard a brief mention about somebody or some task committee working on/interested in developing curve numbers for either green infrastructure or low impact development. Did I hear that correctly? Is there a group working on this? If so please let me know, and maybe provide a very brief overview of the work that is being done. Thank you!

 - Glenn

------------------------------
Glenn Moglen Ph.D., P.E., F.EWRI, F.ASCE
Professor and Laboratory Director
Virginia Tech
Manassas, VA 20110
(703)361-5606 EXT 142
------------------------------

What are curve numbers?

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Johnny Lee P.Eng, CP, M.ASCE
Kitchener ON
1519 8948591

Johnny,

Curve Numbers are approximations of interception and infiltration based upon land use and soil characteristics. It's a popular rainfall-runoff methodology in the United States. The methodology was developed by the US Department of Agriculture's Natural Resource Conservation Service (though when developed it was the Soil Conservation Service or SCS). The paper which outlines the methodology and is still in use today is TR-55 (Technical Release 55) and can be found here: TR-55 Online. It's a little more difficult to implement outside of the United States as some of the input data is developed by the NRCS (Hydrologic Soil Groups being the one I'm thinking of right now).

Hope this helps!

Cheers,

Joe

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Joseph Thomas P.E., M.ASCE
Engineering Manager
AECOM
Sacramento CA
(916)414-5842

Original Message:
Sent: 05-25-2016 09:07
From: Johnny Lee
Subject: NRCS curve numbers and green infrastructure

What are curve numbers?

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Johnny Lee P.Eng, CP, M.ASCE
Kitchener ON
1519 8948591

------Original Message------

Hello Everyone,

I can't remember where I heard it, but at the Congress I heard a brief mention about somebody or some task committee working on/interested in developing curve numbers for either green infrastructure or low impact development. Did I hear that correctly? Is there a group working on this? If so please let me know, and maybe provide a very brief overview of the work that is being done. Thank you!

 - Glenn

------------------------------
Glenn Moglen Ph.D., P.E., F.EWRI, F.ASCE
Professor and Laboratory Director
Virginia Tech
Manassas, VA 20110
(703)361-5606 EXT 142
------------------------------

Michael -

Would you be willing to post for all of us the documentation supplement to the MDE ESD manual you mentioned in your reply?

Thanks.

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Jeffrey Rice P.E., P.Eng, M.ASCE
Water Resources Engineer
Langley WA
(360)222-2057

Original Message:
Sent: 05-25-2016 08:59
From: Michael Clar
Subject: NRCS curve numbers and green infrastructure

Glenn,

I suppose that there may be a number of folks working on this.

One approach that you may be aware of is the procedure documented by the Maryland Department o the Environment (MDE) in their ESD manual. This approach is based on formulas developed by Dr. Rick McCuen back in 1983 when we were developing the Maryland Stds and Specs for design of infiltration practices.  I later adapted the approach in 2000  to estimate the effective CN value when volume based GI practices are used for LID design. I documented this approach in the Queen Anne's County,  LID/ESD design manual and also the Charles County LID/ESD design manual.  MDE liked the approach and adopted it in their ESD  guidance.  The way I do it is slightly different from MDE. I just solve the quadratic equation for an adjusted CN based on McCuen's equations while MDE prefers to use tables and interpolation, which I find to be cumbersome and less accurate.

I can provide a copy of the documentation to supplement the description provided in the MDE ESD manual.

Michael Clar, P.E., DWRE

Chair, LID Committee

Ecosite, Inc.

Ellicott City, MD 21042

410-894-8000

mclar@...

I was at a state stormwater conference in March were there was discussion on changes to the SCS method.  Here are some notes I took from the conference (nothing specific regarding CNs and green infrastructure though):

• NRCS revisions to the SCS method
• Nrcs has revised the method and testing it on sites less than 2 square miles
• SCS Type II is officially dead
• SCS is better for design storms but not as great if you are trying to model historical storms
• SCS not great for longer, low intensity storms
• For the revised
• winTR-55 has new method…download

• Distribution
• Nrcs used altas 14
• Nrcs established 6 different distributions…michigan has only 2 of the 6…#3 and #4…our areas will #3 mostly
• Distributions are pretty similar…the new #3 is actually more intense than SCS type 2. example from 0.14 to 0.17 between scs to #3. Appears to be about 10% difference in #4 area (with #4 10% lower).

Perhaps downloading the WinTR-55 and playing around with the CNs will answer your question...???

WinTR-55 Watershed Hydrology | NRCS

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Jennifer Morreale P.E., M.ASCE
Project Engineer
Hubbell Roth & Clark
Detroit MI
(248) 454-6828

I am part of a Standards Committee working on the ASCE Manual "Design, Construction, and Maintenance of Permeable Interlocking Concrete Pavement".  Attached is DRAFT text on defining CN for this type of pavement system; any feedback is appreciated.

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Glenn Herold P.Eng, M.ASCE
Director Commercial Solutions
Cambridge ON