network is not capturing the full flow from the catchments

Question

Hi, 
 I have an issue with my Hydraulic Model. 
 I have analysed my model with two different approaches. 
 
 For Catchbasins I used Full Capture type in Inlet option. Dimensions are 0.6mX0.6m. 
 
 Used user-defined gutter-> Conventional-> Max Gutter depth 0

Defined a catch basin with same dimensions in Inlet catalog and used it. Also defined gutter in catalog. 
 
 Used max gutter depth 0.06 m in this case(global edit in Catchbasin FlexTables) 
 Now the issue is, in second case it looks like the network is not capturing the full flow from the catchments. I checked the total flow from catchment contributing to a pipe and checked the flow in the pipe, they are not matching. In case 1 its matching. 
 I want to know if I had done a mistake. Please help me through this. 
 
 Case 1 Images:

Case 2 Images:

Jesse Dringoli · Answer

Hi Kartheek, 
 I have taken a look at the model files and I see that in both cases all of the flow is captured, but the ponded area that you have chosen to add above the rim is causing the inlet inflow to be attenuated in the case where the inlet type is set to Catalog Inlet. You can see this by graphing "Flow (total in)" along with "Flow (total out)" for the catchbasin. 
 I believe the reason why this does not happen when the inlet type is set to full capture is because in this case, the gutter is not considered, so the ponded area above the gutter does not come into play, and thus the catchment runoff enters directly into the catchbasin. (if overflow later occurs, the ponded area would be considered). 
 In the case where the inlet type is set to catalog inlet, gutter hydraulics are enabled, and the program considers the impact of the ponded area. Catchment runoff first enters the ponded area and then becomes attenuated as it enters the inlet, similar to pond hydraulics with outlet structures. I am discussing this internally with our developers to confirm that this is indeed expected behavior. In the meantime, please confirm if you intended to have a large ponded area above the inlet.

Yashodhan Joshi · Answer

Hello Kartheek, 
 This is the overflow from the catch basins. Due to less storage area (50 sqm) now, there is overflow at the catch-basins which is causing the high HGL values. Try to use the gutter element in parallel to your catch-basins to capture the overflow. 
 Basically what is happening is that once the storage area for your "In Sag" inlets is getting filled up; its overtopping with overflow and hence the high HGL values.

Jesse Dringoli · Answer

Hi Kartheek, thanks for providing the new, smaller model. 
 In the example case you highlighted with catchbasin P4-IN248-15, you are only comparing the peak flow values, which do not necessarily indicate loss of flow. As mentioned earlier, the introduction of the ponded area introduces attenuation (like a pond), flattening the peak but with the same volume. To see this, graph the catchment flow together with the catchbasin outflow: 
 
 For the example case you highlighted with Profile-1, that covers a different part of the network. If you graph hydraulic grade for one of the catchbasins such as P4-IN236-5 for example, you can see that the high HGL happens for brief periods of time due to what may instability ( fine tuning of the calculation options may be necessary) 
 With that said, after discussing this with our development team, it was found that the combination of ponded area surface storage along with a catalog inlet, is not a valid combination and will lead to the unexpected overflow. You will need to select full capture in this case to see valid results for the in-sag inlet with ponded area. Note that in this case, if you have a gutter connected downstream, any overflow (from the subsurface network spilling out of the rim) will travel down the gutter. If you global edit the inlet type to catalog inlet in your smaller example model, you will no longer see overflow (lost to the system) and the high HGL you saw in that profile example will no longer occur.

Jesse Dringoli · Answer

Hi Kartheek, 
 The catchbasins you are using are all in-sag without any gutters. Can you confirm that you intend to keep them this way and not add any gutters? Are the ponded areas above these inlets all indeed in-sag, where flooding would never have the chance to pass down a gutter? 
 After further investigation it was found that the unexpected overflow (lost from the system, when using catalog inlets in-sag with ponded surface area) is due to the "Maximum Gutter Depth" property. Flooding depth above this will cause overflow. If you want to assume that all overflow will remain in the ponded surface storage (and potentially later recede), set the maximum gutter depth property to a large value such as 10 meters. 
 Here are the calculation option adjustments that worked well for me to achieve stable results in the "Phase 4C" model that you had provided. This is in addition to setting all the catchbasin max gutter depth fields to a large value: 
 Routing Step: 1 second Output Increment: 0.05 hours Use Bentley Transition Equation: True 
 With this, overflow (lost to the system) does not occur, and the results appear to be stable (at least from a few spot checks, in addition to noticing a low continuity error). Note that the flooding depth does still get a bit high at the flooded nodes, but this may be expected due to the surface storage size and the extent of the flooding.

Jesse Dringoli · Answer

Kartheek, the overflow is caused by the flooding depth exceeding the max gutter depth property. In other words, it assumes that when the max gutter depth is overtopped, the excess water becomes overflow. Your model exhibits excessive flooding causing relatively high flooding depths. 
 In the real system, what happens when the water level exceeds 0.1 m?