How to approach LID or Discharge control in SewerGEMS?

Hello Sphurti,

To model swales in SewerGEMS you can consider them as open channels and model them to receive the runoff from your catchment. See the below article which provides some guidance on this;

How to model a swale in the storm and sanitary products

However, since you want to consider infiltration in the ground you can use LID elements to model this. Using the appropriate LID element and specifying the parameters such as permeability, storage conductivity etc. you can specify the infiltration for such elements. See the article below which can guide you in modeling LID elements;

Low Impact Development (LID)

Let me know if this helps.

Hi,

Thanks for the reply.

I did design swales as the channel, I didn't find any problem in that.

I wanted more of the technical background of LIDs. Plus what about the design of discharge control?

By discharge control, do you mean controlling the runoff from the catchment?

My earlier response provides technical description on LID's, their use cases and how to configure them in your model. 

yes controlling runoff in a catchment by designing pond or retention tank (EFA) and draining runoff with fixed volume through the orifice to the main outlet?

Hello Sphurti,

You can model your system with connectivity as shown below;

Catchment > Pond > Pond Outlet Structure > Outfall

Now to control the flow at the Pond Outlet Structure, you can set the "Has Control Structure?" option to "Yes" and specify your orifice parameters such as orifice diameter, coefficient etc. 

You can have a constant outflow from your catchment if you specify a user defined hydrograph with time and flow data. See the article below for details on this;

How to model fixed flow into a pond

I am also sharing an additional article for pond outlet structure modeling;

Pond and pond outlet assumptions in StormCAD, SewerGEMS, CivilStorm and SewerCAD

Hope this helps.

Sphurti,

Regarding catchment infiltration - are you referring to the portion of rainfall that soaks into the ground before it becomes runoff into your swale, or are you referring to infiltration in the swale itself?

For the former (catchment infiltration), typically you would account for this using a particular Loss Method in the catchment. A common method is the SCS CN loss method used in conjunction with the unit hydrograph and a time-depth rainfall curve.

What type of rainfall information do you have? Are you required to use a specific runoff method? (unit hydrograph, modified rational, epa-swmm, etc). Do you know the area and time of concentration of your catchments?

•  Hi Jesse,

Yes, I am talking about catchment infiltration portion of rainfall that soaks into the ground, yes I do know the area and time of concentration of catchment.

•  Hi Jesse,

Yes, I am talking about catchment infiltration portion of rainfall that soaks into the ground, yes I do know the area and time of concentration of catchment.