Storage Unit/Outlet Properties 1

[Ryb01]

Hello SWMM users,

I have a question(s) about the method used with regards to the Storage Unit and also the Outlet properties in SWMM 5.0. I have the understanding of the following;

Storage Unit Properties
-the user has the option to select either a functional or tabular shape curve which describes the geometric shape of the storage unit
- the Functional shape curve has the relationship of Area= A*(Depth)^B+C, with the coeff(A), exp(B) and constant(C)
- the Tabular shape curve allows the user to input a depth vs area curve

Outlet Properties
-the user has the option to select either a functional or tabular shape curve which describes the outflow based on a given head
- the Functional shape curve has the relationship of Q= A*(h)^B with the coeff(A), exp(B)
- the Tabular shape curve allows the user to input a flow vs head curve

A couple of questions......
1) (Storage or Outlet Properties) If you select say the Tabular method, would the A,B,C or AB coefficients be inputted as 0 as they would be overwritten by the selected Tabular method?
2) This may be a silly question but, what method do you use to calculate the A,B,C parameters for the Storage units properties and A,B parameters for the Outlet Properties assuming that I know specific areas at depths or flows vs head? My elementary math skills have diminished over time.

Any feedback on this would be greatly appreciated. Thank you in advance for your help.

 

[RWF7437]

"A couple of questions......
1) (Storage or Outlet Properties) If you select say the Tabular method, would the A,B,C or AB coefficients be inputted as 0 as they would be overwritten by the selected Tabular method?"

I'm not an experienced SWMM user but it it seems highly unlikely one could use both methods in the same model. You can use one method or the other in a single model. Or, you could create two models using one method in Model A and the other method in Model B.

"2) This may be a silly question but, what method do you use to calculate the A,B,C parameters for the Storage units properties and A,B parameters for the Outlet Properties assuming that I know specific areas at depths or flows vs head?"

To calculate coefficients and/or exponents for such an algebraic equation you can use regression analysis. This is a way of fitting data to an equation by an iterative ( trial and error) process. There are many computer programs available to do this. MS Excel has some limited capabilities for doing this but there are many other no cost and low cost programs out there. Google "free regression analysis" and you'll find many.

good luck