SSA Simple Backwater Analysis

[hansenbk]

I'm attempting to run some simple backwater analysis using SSA 2012.

I am trying to simply provide a tailwater elevation at a downstream outlet, add a single peak flow to a serious of catchbasins and determine the HGL at each catchbasin using the flow inputs.

I'm trying not to use any of the hydrolic functions in SSA to compute the flows, only using the hydraulics fuctions and the flows I manually input.

It seems like the Average HGL is providing what I need, however it differs from the Max HGL.  I can't determine why this would be, as I am only looking at one set of flows and not a time series.

If anyone has any experience with something similar to this, I would appreciate any advice.

I've attached the model I created for clarification if that is helpful (renamed as a .dwg)

Thanks!