- (a) The purpose of this section is to address increases in the frequency and magnitude of flooding caused by development.
- (b) Subject to (d), below, the 10-year, 24-hour post-development peak flow rate shall not exceed the 10-year, 24-hour pre-development peak flow rate for all flows leaving the site.
- (c) Subject to (d), below, the 50-year, 24-hour post-development peak flow rate shall not exceed the 50-year, 24-hour pre-development peak flow rate for all flows leaving the site.
- (d) A project area that directly discharges to a stream, waterbody, estuary, or tidal water shall be exempt from (b) and (c), above, if the applicant has provided supporting off-site drainage calculations for the 10-year and 50-year, 24-hour storm in accordance with Env-Wq 1504.09, showing that at a point immediately downstream from the project site the post-development peak flow rate from the site and the off-site contributing area does not exceed the pre-development peak flow rate at that point.
- (e) The applicant shall provide supporting information in accordance with Env-Wq 1503.09, showing that there is no impact to properties as a result of developing within the 100-year floodplain.
- (f) All proposed roadway culverts shall be designed to pass the 50-year, 24-hour post-development peak flow rate without overtopping the roadway.
Source. #9343, eff 1-1-09; amd by #9817-A, eff 12-1-10; ss by #12342, eff 8-15-17; ss by #14472, eff 1-19-26, EXPIRES: 1-19-36