| Product(s): | SewerGEMS, CivilStorm |
| Version(s): | 10.04.00.158 and higher |
| Area: | Modeling |
The following user notification appears when validating or computing a 2D model:
"The catch basin has wet weather flows defined either on the Inflow (Wet) Collection or with incoming catchment hydrographs. These flows are injected directly into the sewer network. To handle surface flows, you can apply these loads to 2D boundary points."
This message is informing you that catchment runoff will directly enter your subsurface pipe network (inside the catchbasin element). This is to make sure you are aware that the catchment runoff is not going onto the 2D grid first, and is not approaching the inlet location. Rather, it is directly entering the subsurface network because for inlets overlapping a 2D grid, surface flow is only assumed to be water on the grid itself.
If you would like the catchment runoff to first go onto the 2D grid and then approach the inlet opening (so that inlet capture occurs based on depth on the 2D grid), you will need to direct the catchment's "Outflow element" to a 2D boundary point or boundary line. As an example, take a look at the model named "Lesson_9_5 finished" located within the "Lessons" folder within the SewerGEMS installation folder. This model has a catchment whose Outflow Element is directed to a boundary line on a 2D grid. This allows the catchment runoff to discharge evenly onto the 2D grid along the boundary line. It can then disperse accordingly on the 2D grid and approach inlet openings (though, no inlets are present in this particular example model).
Here are some options to consider:
If you are only using 2D modeling for analyzing overflows out of catchbasins, and if you are OK with the assumption of full capture from catchment runoff, you could leave the model as-is (catchment directly connected to catchbasins).
If you are interested in analyzing how the catchment runoff interacts with the 2D grid and impacts catchbasin capture, then you could either enter a boundary point nearby each catchbasin location and change the corresponding catchment's "outflow element" to that boundary point, or you could define a long boundary line element at certain points and direct multiple catchments' "outflow element" to that boundary line. The boundary point and boundary line elements can be found in the "boundary conditions" section of the "2D Modeling" ribbon menu.
Another option would be to remove all catchments from the model and change the calculation option "Rainfall Method" to "Rainfall on grid and catchments". This will cause rain to fall on the entire 2D grid element and then travel on the 2D grid based on the terrain (and the Mannings n and SCS CN value you entered in the grid properties). Any water on the grid at the catchbasin location will be captured accordingly based on the water depth on the grid. You would need to use your judgement and knowledge of the system and terrain to determine is this is an acceptable approach.