junctions in reclamation network

Dear All,

I'm trying to model with SWMM5 a reclamation network. I have a question about junctions: since my channels are all trapezoidal (that is to say open channels), my junctions are not manholes used in urban drainage. How can I model a junction like this? I have seen in the user's guide (extran addendum, page 22) that it is possible, but I don't know what kind of value I have to put for the junction's cross section, because the junction hasn't a cross section since it's just a channal's intersection.

In SWMM4.4 there were the parameter AMEN on B2 line (default surface area for all junctions), and I thought to put it equal zero until I read than this means a 4 ft diameter by default (extran addendum, page 15). What can I do? Is there a simple way to solve my problem in SWMM5?

Thanks to all,
Giorgio Camorani
giorgio.camorani@MAIL.ING.UNIBO.IT

Giorgio,

This is an interesting question with many ramifications in SWMM 4 and SWMM 5:

First, if you used a value of 0.0 for AMEN in SWMM 4 the program will change the area to 12.566 square feet or 1.22 square meters. If you use a value of 0.01 for AMEN in SWMM 4 then the minimum area will be 0.01. If you were using 0.0 then SWMM 4 and SWMM 5 have the same behavoir in your model.

The minimum area in SWMM 5 is hardwired at present to:

#define MINSURFAREA 12.566 // min. nodal surface area (~4 ft diam.)

since the internal units are American units in SWMM 5. We will have to test how important having a minimum area of 12.566 is versus 0.01, for example, in SWMM 5. It probably does not matter a lot if you are using medium sized trapezoidal channels. Again if you were using 0.0 for AMEN in your SWMM 4 data set then SWMM 5 will use the same default area.

Regards,
Bob Dickinson
DickinsonRE@CDM.COM