According to the City of Dallas Storm Drainage Design Manual, detention ponds are required to maintain a minimum of 2.0 feet of freeboard above the design water surface elevation to provide a safety buffer against overtopping, outlet blockage, and storm events exceeding the design criteria.

Freeboard must be verified through stage–storage analysis, not assumed. A detention pond that meets the required storage volume but does not maintain the minimum freeboard is considered noncompliant and may increase the risk of embankment failure and downstream impacts.