Gully Rating Curve

Question

As I know the Rating curve for the gully is usually can be got from the manufacture. can I generate the rating curve for "Curb Inlet on Grade" by using Bentley FlowMaster? if yes; how that can be done? 
 is the rating curve is the relation between the discharge flow and depth of water ponding over the grate? I was not able to find that relation in FlowMaster. 
 
 Regards, 
 Mohamad

Jesse Dringoli · Accepted Answer

With on-grade inlets, only the approach flow vs. captured flow rating curve can be used. Having the ability to enter an approach flow vs. gutter depth curve would not be enough information for on-grade inlets since they need to know how much flow gets captured vs. bypassed. Perhaps the ability to use HEC-22 catalog inlets with the "Bentley Enhanced" SWMM solver is a major benefit you could point out, toward using that solver (rather than the EPA version of the solver)

Regards,

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

Jesse Dringoli · Answer

Hi Mohamad, 
 Can you provide more background on why you need to do this and exactly what type of rating curve you need? 
 Currently, the curb inlet on grade worksheet in FlowMaster can plot a rating curve of Efficiency, Intercepted flow or curb opening length (depending on whether you solve for curb length or efficiency) versus discharge, gutter depth, gutter slope, roughness, efficiency, local depression or local depression width. Select the "solve for" and click the "Rating Curve" button on the toolbar, then configure and click OK to see the curve. 
 The curb inlet in sag worksheet can plot a rating curve of gutter depth vs. c aptured flow , because the flow in that case is essentially fixed (since an in-sag inlet captured 100% of the flow) so it is able to vary that flow and plot the resulting gutter depth or spread. On the other hand for an on-grade inlet, captured flow and depth are both calculated results. In other words, the program solves for both based on other input such as approach flow. 
 If you want to see the relationship between approach flow (flow approaching the inlet from the upstream side of the gutter) and gutter depth for an on-grade curb inlet, you could manually vary the Discharge input and observe the "depth" value on the right side (for example you could note the pairs in a table in Excel) 
 If you are trying to model a network of inlets and you have a rating curve from the manufacturer, you can use StormCAD, CivilStorm or SewerGEMS where inlets can be defined by rating curves . (Gutter Depth vs. Captured Flow for in-sag and Flow to Inlet vs. Flow Captured for on-grade)

Jesse Dringoli · Answer

Mohamad Azzam said: The relation would be Discharge input vs Depth? Or would be Intercepted Flow vs Depth? 
 It depends on what you mean by "discharge". For an on-grade inlet you would look at approach flow (flow upstream of the inlet, some of which will be captured (intercepted) and some of which will bypass) versus the gutter depth. As mentioned in my previous reply, both gutter depth and intercepted flow are calculated based on other input (like approach flow) for on-grade inlets, so you would not vary the intercepted flow for an on-grade case. 
 Mohamad Azzam said: As you remember the discussion about the SWMM engine and how it does consider the 100% capturing flow, what do you think if I have the rating curve of the "On Grade" and used that curve with the SWMM engine? I am thinking that the On Grade gully is not going to capture 100% of the flow, so the part would be captured and the rest will bypass to the gutter. 
 Are you referring to this discussion? - On Grade Inlet with SWMM 
 If so, that discussion is about how on grade catalog inlets will assume full capture when you have the compatibility calculation option set to use the basic EPASWMM solver instead of the "Bentley Enhanced" SWMM solver, because EPA-SWMM does not have HEC-22 inlet calculations. If you want to model on-grade inlet capture efficiency calculations with the SWMM solver, you will need to select the "Bentley" version of the SWMM solver. As mentioned in the other discussions, this is still the SWMM solver, but has additional capability above and beyond the SWMM solver, including the HEC-22 inlet capture calculations. 
 If there is a reason why you need to use the "SWMM" version of the SWMM solver (without the benefits of the Bentley version), then you do indeed still have the option of modeling the on-grade inlet using a rating curve, but as per the article mentioned in my previous reply, on-grade inlets would use the rating curve that defines approach flow vs. intercepted flow (selected from the inlet type dropdown in the catchbasin properties). You could indeed develop that curve using the same HEC-22 principles by using the rating curve option in FlowMaster, by choosing to plot intercepted flow vs. "discharge" (where "discharge" is total approach gutter flow). 
 
 You could then enter this in SewerGEMS/CivilStorm using the Inflow-capture option previously mentioned. That would enable you to get the same capture efficiency results (how much gets intercepted vs. bypasses). However, you would not be able to get depth or spread results (they will be "N/A") since those require the full HEC-22 catalog inlet calculations (which are not supported with the basic SWMM solver version, only the Bentley SWMM solver version). If you need to see inlet depth and spread results, you will need to use the "Bentley" option for the SWMM solver version, or use the Implicit solver. 
 I have added notes to this related article based on the above information.

Jesse Dringoli · Answer

Mohamad Azzam said: 1-Regarding the article that you have mentioned in your reply; The Solution -in-sag is used the Inlet Type is "Gutter Depth vs. Captured Flow", I need to develop that curve from the FlowMaster, and I guess (correct me if I am wrong) the depth and the captured flow (intercepted flow) would be on the right side in the FlowMaster by varying the Discharge input (on the left side)? 
 Yes, in-sag inlets can use a depth vs. captured flow curve but you might think of it the other way around - the "captured flow" is really the approach flow (and also the captured flow since in-sag captures 100%), and the program would look up the gutter depth resulting from a given approach flow (all of which is intercepted). In FlowMaster you would use the curb inlet in-sag worksheet, click the rating curve button and plot depth vs. discharge. I'm not clear on whether the inlets you're trying to model are actually in-sag or on-grade, though. 
 Mohamad Azzam said: 2- when you say "Discharge" (where "discharge" means the total approach gutter flow), is that in the Flowmaster in the left side (the input)? jut to confirm, please 
 See the screenshot below where I said this in my previous reply - when you click on the "Rating curve" button above the worksheet in FlowMaster, you can choose the two fields to plot. This is where you would select "discharge". "Discharge" in this case refers to the total approach flow. There is indeed also a "discharge" input field in the worksheet form itself, and this does refer to the same flow. Meaning, the "Rating curve" option does the same thing as manually varying the related parameter. For example for an on-grade curb inlet worksheet, plotting Intercepted flow vs discharge is the same as varying the "discharge" input in the worksheet and noting the resulting "intercepted flow" in the results section on the right side. 
 Mohamad Azzam said: 3- Can "Gutter Depth vs. Captured Flow" be used for " Solution-on-Grade)? because I noticed that "Flow to Inlet vs. Flow Captured" is used there, and also vice versa can "Flow to Inlet vs. Flow Captured" be used for Solution -In- Sag? and what if I would apply "Gutter Depth vs. Captured Flow" for both (on grade & In Sag)? Please elaborate more if there is any limitation. 
 "Gutter depth vs. captured flow" only applies to in-sag inlets and "flow to inlet vs. flow capture" only applies to on-grade. The reason is explained in my reply from Sunday. 
 Mohamad Azzam said: 4- If I have a model built in the SewerGEMS with the gullies without rating curve as input, can the model produce those rating curves? i.e. can I generate the rating curves as in the FlowMaster then use them in other models? 
 Yes in SewerGEMS you could potentially vary the approach flow and observe the change in results for catalog inlets (for example using the Bentley version of the SWMM solver). You could set up a small model with just one inlet to achieve this. However, it seems to me that it would be easier to just do this in FlowMaster. Once you have the rating curve defined in the inlet catalog, you could export that to an engineering library to then import into other models as needed. Note that the rating curve may depend on parameters such as the road slope that would change, so you might need a different rating curve for each variation of such parameters.

Jesse Dringoli · Answer

Mohamad Azzam said: from what you said for the "On Grade" it can be generated the rating curve "Gutter depth vs captured flow" and can be used for the on garde gully. if I miss understand that; please let me know why can not be used?. 
 For on-grade, you can generate a rating curve of approach flow (upstream gutter) versus gutter depth. However, as mentioned in a few earlier posts, with on-grade inlets, both the depth and the intercepted flow are calculated results (with on-grade), so you cannot solve for one, varying the other. This is why the "gutter depth vs. captured flow" rating curve is only applicable to in-sag inlets. See more explanations further up in the thread.

Gully Rating Curve

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