to model chute drains in sewergems

Question

Hi, I am trying to model chute drains in sewergems. Scenario is , that we have to model a very steep drain from start to stop ground level of 13m to 10m respectively in a length of 10m in the embankment, as in the picture below.

Jesse Dringoli · Answer

Hi Arunima, 
 Which numerical solver are you using with SewerGEMS? (Implicit, Explicit (SWMM), GVF-Convex or GVF-Rational) 
 What do you need the model to tell you? Meaning, are you only interested in the capacity of the curb cuts (notches in the curb) to capture runoff and reduce spread/depth in the road, or do you need to ensure the chutes and "energy dissipating basin" are sized correctly? 
 You could model the cut in the curb in the same manner as described in this article - use the curb inlet type in the inlet catalog with the catchbasin element, to model the capture efficiency, spread and depth at the curb. As for what happens to the captured runoff as it travels down the "chute" and into the drainage network - you could try modeling that explicitly with the Implicit or Explicit solver using a steep conduit or channel, connected to a transition or manhole (with structure loss method as appropriate) which would then connect to the subsurface pipe network. 
 However, you may want to consider simplifying the approach by estimating the headloss through the chute and "energy dissipating basin" as one of the structure loss methods. Meaning, you would use the same catchbasin element to model the curb inlet plus the structure loss method property to account for headloss (see guidance on structure loss methods here ) You could set the invert elevation of the catchbasin to the bottom of where it connects to the subsurface drainage network (and connect conduits downstream of it to model the subsurface drainage network). 
 If the standard curb catalog inlet type is not appropriate for modeling the capacity of those curb cuts/notches, you you could use a rating table if you have it from the manufacturer. See more here: Modeling Custom Inlets Using Inlet Capture Curves

Jesse Dringoli · Answer

Thanks for clarifying. In that case, you can use the suggestion in my previous reply where the curb cut is modeled as a catchbasin element with either a catalog inlet set to the curb inlet type, or a custom rating curve. The chute would be modeled using a channel or conduit element with cross sectional shape modeled according to the shape of the chute, and the energy dissipation basin could be modeled as a manhole or transition element with structure loss method set to model the resistance through it.

Regards,

Jesse Dringoli
Technical Support Manager, OpenFlows
Bentley Communities Site Administrator
Bentley Systems, Inc.