Hello Danielle,

Could you post a screenshot of the plan view layout?

You should be able to model a retention pond like the below screenshot. Ensure that the outfall is set to boundary element and is connected to the pond.

If this doesn't help and you do not wish to provide a screenshot, you also have the option to privately send the model to Bentley. See below.

Sharing Hydraulic Model Files on the Haestad Forum

Yes - basically graph the pond water surface elevation as you have done, and find the difference between the peak and the maximum value on the graph. Or, go by the peak value reported in the pond properties.

The PondMaker tool directly reports freeboard and is a factor in its semi-automated design capabilities, but there's an assumption that you have an outlet structure and are reducing the peak outflow to be less than the predevelopment rate. You may still be able to use PondMaker though to size the pond with the estimated storage step, but you'll have to make some adjustments to account for that fact that you essentially want all of the water stored. Manual sizing of the pond works as well (observing max WSE, adjust size, try again, etc)

In your screenshot it looks like the simulation ends before the pond reaches its peak. You may want to extend the simulation duration in the calculation options.

Hi Danielle,

Thanks for sending the screenshot. Remove that outfall; that would only be used for water entering the pond, hence it is considered to be orphaned.

Regarding freeboard, yes, you can compute the model, the either graph the pond elevation, or look at the result field in the properties of the pond called "Elevation (Water Surface, Peak)" and compare it to the pond top of dam.

For the reference of other users who will refer this post, we have updated the wiki on modeling detention ponds.

communities.bentley.com/.../25905.how-do-i-model-a-retention-pond