Forebay and Micropool Modeling

[cfj104]

Can anyone offer some advice on how to model a sediment forebay and micropool within a detention basin? Do I set up the model so the forebay would be a separate pond flowing into the basin or maybe add it as an additional outlet? If I include the volume in the storage, is this all that needs to be done?

I have my basin laid out so that the inflow water flows into a forebay, then through a low flow channel, and then to a micro pool prior to final discharge. I am just trying to find the best way to lay out the system within the model.

Thanks!

 

[psmart]

Yes, you could model the forebay as a separate pond with appropriate storage and outlet device(s). But if the forebay doesn't provide enough storage to create significant detention, there may be no point to including it in the model at all.

Another approach is to model the forebay as part of the storage in the main pond. Just include it on a separate line in the storage tab. This is appropriate if the two storage volumes will usually be equalized. For details see

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

For general modeling tips please see

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

Peter Smart
HydroCAD Software

http://www.hydrocad.net

 

[murdock]

I wouldn't model the forebay as a separate pond node, it will get confusing when trying to figure out the dry storage area; storage will be across the two nodes, and the outlet behavior may differ from a single-node pond.

Typically I just add the storage in the forebay and micropool together and make sure that the starting elevation is the permanent pool elevation. If you need to know the permanent pool volume of the sections separately, use Peter's suggestion of adding another line on the storage tab.

I try to stay simple in the model; I wouldn't model the low flow channel. If anything, you're being more conservative by not accounting for the travel time through the channel.