(A) Show the limits of the one hundred (100) year flood-prone area on the final plat in a surveyable and readily retraceable manner with frequent ties to intersecting lot lines for all flows of fifty (50) cubic feet per second or more.

(B) Watercourses that are relocated, altered, or include any man-made improvements, shall be developed with channel treatments that allow for the reestablishment of vegetation. The use of concrete will be limited to headwalls, cut-off walls, transitions, and areas with limited right-of-way because of existing improvements. The placement of concrete structures shall be at the discretion of the public works director.

(C) Culverts for streets shall be designed to convey at the fifty (50) year peak discharge with no flow over the roadway. Additionally, the flow depth over the street shall be limited to one (1) foot for one hundred (100) year peak discharge if the street provides all-weather access.

(D) A minimum pipe diameter of eighteen (18) inches shall be required for all street crossings and a minimum pipe diameter of twelve (12) inches for all driveways. All culvert sizes must be calculated as a part of the drainage report.

(E) Culvert outlet velocities shall be kept below ten (10) feet per second unless special conditions exist. The maximum velocity shall be consistent with the channel stability requirements at the culvert outlet. If the culvert velocities exceed permissible velocities for the proposed outlet (greater than five (5) feet per second for natural conditions depending on soil types), suitable outlet protection must be provided. Calculations are required.

(F) Drainage ditches or storm drains along streets and adjacent areas shall be required to avoid trapping water and to ensure positive drainage away from the streets. Street drainage shall be designed to provide for one (1) lane of traffic on all local streets and one (1) lane of traffic in both directions for all collectors and arterials for the ten (10) year peak discharge. (Ord. No. 2008-12, §§ 1, 2, 9-16-08; Ord. No. 2019-02, § 1, 2-5-19. 1976 Code § 12-4(f))