I am trying to model the interaction between stormwater and surface water using SWMM. Flow in the canal I am dealing with is maintained by gated spillways. The canal has very irregular and even  adverse slope i.e. slope against the direction of the flow as shown in the following figure.

If I provide the SWMM model with this exact canal profile against the direction of flow, will it be able to reflect the head loss due to friction and change in conveyance due to adverse slope? ( I am providing the gated spillway upstream to input the necessary head)

What alternative can I use to represent the effect of this adverse slope in a simplified way?

This is stressing the scope of SWMM I understand, but if I can do this,  this will be something very interesting .

I appreciate your help as always. Thanking you in anticipation.



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  • SWMM 5 handles the adverse slope this way so it will work correctly

    Subject:  Adverse Slope Convention  in  SWMM 5

    If the slope of a link  is negative and the solution  is dynamic wave then the following data will be switched in link.c in SWMM 5.  All upstream data for the  link  is switched to the downstream end of the link  and  vice versa.   The means that if the flow  is from the original upstream node to the downstream node the flow  will  be negative in the output of  SWMM 5. 

    Negative flow in SWMM 5 means:

    1.   The link has an adverse or negative slope,

    2.   The link  has reverse flow if the link slope is positive.


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