Duluth UDC § 1016.06

1. All new proposed channels shall be designed to carry at least the fully developed 25-year storm with freeboard equal to 20% of the design flow depth. 2. Transition channels shall be provided at the inlet and outlet ends of all culverts and pipe systems, unless otherwise provided herein. 3. The maximum flow velocity at the project site's downstream property line shall not exceed the predeveloped velocity. 4. In cases of potential erosion due to irregular channel alignment, extreme velocities, or excessive slopes, a paved ditch may be required. However, if, in the opinion of the City, the expected long-term maintenance of a surface drainage system could prove impractical, a pipe design may be required. 5. The cross-sectional shape of channels shall be as found in the Gwinnett County Standard Drawings. "V" shaped cross-sections are not permitted in grassed channels. 6. If the channel will be affected by backwater from culverts, bridges, other structures or floodplains, backwater curves shall be shown in profiles of the channel. 7. All channels, must be capable of conveying sufficient flows to ensure that overflow of the channel would not result in a likelihood of dwelling flooding, property damage or public access and/or utility interruption being greater than one chance in 100 years. 8. Channels shall be designed to carry the fully developed 25-year flow in accordance with the Georgia Stormwater Management Manual.