TR-55 Sheet Flow

[johnengr]

We are working with a sports field that has artificial turf, with a clean stone base. Would like some opinions on an appropriate N value to use for the sheet flow until it enters the piping system.

 

[psmart]

I wouldn't expect much (if any) sheet flow with artificial turf. Depending on the base, the rainfall will pass through the turf pretty quickly rather than flowing on the surface. I believe there have been several threads on this topic.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[beej67]

I used to think the same thing, Peter, until I started playing soccer again last year for the first time since the Clinton administration. Why, I'm not sure. I guess you get craze when you get middle aged. I've witnessed a couple of real gutter washers hit the turf fields we play on, and inundate the whole thing.

I would estimate the runoff velocity of sheet flow on an artificial turf field on which I'm trying to play soccer during a torrential downpour to be approximately 0 ft/s to 0.5 ft/sec if the other team has the ball, and 0.5 ft/s to 1.0 ft/sec when I have the ball.

Hope that helps.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[psmart]

beej67: Do you think it was sheet flow or ponding? Most of the the turf designs I see are completely flat, so there is no slope or flow path for calculating sheet flow. When modeling these systems it is usually assumed that the rainfall flows immediately into the stone base, which is usually designed to hold/detain a 3"-4" event.

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[beej67]

Over time the things clog up with dust and whatnot, and ponded water always goes somewhere. In this case, the whole thing ponded up and then spilled over a curb into the parking lot. The place I play at uses the fields outside the stadium for rec league soccer on the weekdays and (possibly ill advisedly) for parking on the weekends. The surface isn't great.

Hydrology, Drainage Analysis, Flood Studies, and Complex Stormwater Litigation for Atlanta and the South East -

http://www.campbellcivil.com

 

[johnengr]

In talking with some guys yesterday we decided that the N value for rip rap which is in the 30ths would be appropriate to use for the sheet flow time of concentration calculation.

 

[cvg]

this has been discussed before

thread162-358396
thread162-343617
thread162-246301