Dynamic Hydraulic Modeling - Green Roofs
Dynamic Hydraulic Modeling - Green Roofs
(OP)
I am new to this forum but have used it many times to find helpful informaiton. I could not find another posts where others have modeled using a a dynamix model like ASSA or XPSWMMM. I am in NY and have worked with the regulators on the best way to treat a green roof or other runoff reducing practice such as a dry swale in a dynamic model. I would like to account for the peak flow rate reduction and also the runoff reduction. If I treat it as a storage node as the regulator sugests, I do not think this helps mimic how water is going into the extensive system and what is being absorbed my the soil. Once saturated or "full" then what is the outlet structure for the green roof in larger storms. I would love to hear from anyone that has modeled a practice similiar to this in ASSA or similiar programs. ASSA speaks about how it allows for modeling of a green roof but I cant find how to execute this. Thank you for the help.





RE: Dynamic Hydraulic Modeling - Green Roofs
Ordinarily, I have simply assigned a curve number to the pervious portions of the green roof, and included that in my weighted CN calculation on the basis that the roof will mimic a ground level hardscape with landscape islands. It's a simple approach, and regulators usually buy it. If you do this, do *not* also account for storage in the node, because if so you'll be double dipping.
I have only accounted for the rooftop storage in a storage node once. It was a significant amount of storage on a grass-topped parking deck with a chamber system in it and a drawdown orifice. I modeled this just as I would a concrete vault with the appropriate outlet control structure geometry.
I have modeled storage within rain gardens on occasion, and I did that by using known porosity of the backfill material and reducing the subsurface volume accordingly, including full volume for detention above the surface.
It's hard to know the best approach without seeing some design plans.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Dynamic Hydraulic Modeling - Green Roofs
RE: Dynamic Hydraulic Modeling - Green Roofs
RE: Dynamic Hydraulic Modeling - Green Roofs
In actual practice, some of the stormwater is going to cling to the rain garden media, but I'd neglect that to be conservative.
Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East - http://www.campbellcivil.com
RE: Dynamic Hydraulic Modeling - Green Roofs