HEC-HMS 3.5 and Multi-stage outlet stucture capabilites??

[Topshelf7000]

Hello all:

I've often lurked this site many a time for answers to my questions - I had to "join" to post so here I am. I am trying to set up a multi-stage outlet structure in the HEC-HMS program (pretty simple in Hydraflow-Hydrographs). Is this possible in HEC-HMS 3.5? I don't theink the auxilliary/main direction is the answer. I have my basin-reservoir-and outlets accounted for, just wondering if my outlets are going to perform independently...

Any help/input would be greatly appreciated...

Topshelf7000 (Scott)

 

[SMIAH]

You can use a rating curve. Calculating it with Excel and then only input the Elevation-Discharge relationship.
You could then only use your basin and a reservoir.
Watch out for tailwater effects.

You can set a multistage oulet in HMS by using different controls e.g. orifice, culvert, dam, etc.

Hope this helps.

 

[Topshelf7000]

SMIAH:

Thanks for the response. I do follow you that I can specify various outlets and types set at different elevations etc. What I will have is a 60" Manhole with 3 orifices punched in the side at various invert elevations and diameters. From this manhole, the ultimate discharge will be thru a 30" Culvert. The top of the Manhole will serve as an overflow weir as well - And lastly I will have an emergency overflow spillway completely separate from this outlet structure (auxiliary?) What I am hoping is that there is a routine?/function in HMS that will allow me to set up the combination (multi-stage) outlet. The 3 orifices and overflow weir are dependent on the capacity of the 30" culvert ya know what I mean?

I guess what I'm trying to say (and struggling - thats why I like numbers - is I need the multi-stage outlet to function as a unit. The Spillway can certainly be independent.

I've attached an image (hope it works), because a pictures worth a thousand words haha. Hoping perhaps someone has run a similar scenario to mine and that HMS CAN tackle this kind of outlet.

Thanks again!!!

Scott

 

[SMIAH]

Yes in the Reservoir you can choose "Ouflow Structures" as the method instead of "Outflow Curve".
Then if you scroll down the menu, you can add Outlets at different stage (e.g. 3 for you), Spillway and a Dam Top.
You will have to specify the method for your orifice (culvert or orifice), the number of barrels (i.e. 1), Center Elevation, Area and the coefficient for each of your 3 orifices.

Then HMS will route your hydrograph and it will calculate the multi-stage outlet.

Hope this helps.

 

[gbam]

I recommend using the rating table developed outside of HMS. That way you take into account tailwater and other headloss or hydraulic items. I am not sure how HMS computes the hydraulics of the opening. Back in the day, HEC-1 had the low level outlet option but it never really seemed to work correctly. Since I have always used a rating table hardcoded into HEC-1 or HMS.

 

[SMIAH]

I recommend it too but HMS can take into account tailwater effects (you have to select an option for it).

 

[Topshelf7000]

Okay guys - thanks for the help/input. I think I am just going to input all the values into the outlet dialogue boxes for the orifices, weir overflow, 30" Culvert (orifices and weir flow into this [see previously attached image] - I just wish there was a toggle or something that I could switch so the program knows these are "tied together" and dependent upon one another). spillway is separate and I will fill in the necessary data and see if this works out. I will compare to the multi-stage structure I set up in Hydraflow and compare the two.

The rating curve is just an excel (comma delimited) stage vs outflow data set? Sorry for all my questions, I just know that if someone has gone down this road that can save hours of "hacking" on my part..

thanks again for all

Scott

 

[froude]

You may be able to just do a regular Excel (.xls or .xlsx) spreadsheet and copy/paste the values into your HEC-HMS reservoir element.