(a) Generally.
(1) The subdivider shall provide for the design of drainage facilities and improvements in accordance with this section and to the satisfaction of the City Engineer.
(2) The Engineer may require the subdivider to evaluate the flooding and drainage hazards downstream from the subdivision that may be caused or compounded by the proposed subdivision.
(3) Subdivisions shall be protected from flood hazard and inundation by stormwater, springs and other surface waters.
(4) Natural watercourses entering the subdivision shall be received and discharged from the subdivision as nearly as possible in the manner that existed prior to construction of the drainage facilities within the subdivision.
(5) Outlets for all drainage facilities shall be approved by the Engineer and provide for permanent control of erosion, scouring, siltation and sedimentation.
(6) Where property damage is a possibility, stricter design standards than those specified in these Subdivision Regulations shall be required.
(b) Hydrologic design.
(1) As used in this section:
A. Major waterways. "Major waterways" means those waterways with a tributary area in excess of six square miles. Such major waterways shall be designed for a minimum storm frequency of 50 years.
B. Minor waterways. "Minor waterways" means those waterways with 320 acres or less of tributary area. Such minor waterways shall be designed for a minimum storm frequency of five years.
C. Secondary waterways. "Secondary waterways" means those waterways with a tributary area of between one-half and six square miles. Such secondary waterways shall be designed for a minimum storm frequency of ten years.
(2) Design quantities of flow for major waterways shall be provided to the subdivider by the County Engineer. Design flows for secondary waterways shall be in accordance with the procedures contained in the most current publication of the Ohio Department of Natural Resources, Division of Water, Bulletin 43, Floods in Ohio. Design flows for minor drainage facilities shall be computed by use of the rational formula: Q = CIA. The method for determining design flows may be modified where deemed advisable by the City Engineer.
(c) Drainage plans. The detailed engineering drawing shall include and shall have appended to it sufficient data for the City Engineer to check the feasibility of the drainage system as proposed by the subdivider. The following data shall be provided:
(1) Tributary drainage areas delineated on a map, times of concentration, intensity, run-off coefficients and design flow for all critical points in the subdivision;
(2) The plan and profile of all drainageways, including a cross-section of open channels showing the maximum depth of flow;
(3) Sizes and types of drainage improvements, including all special structures, typical sections, permanent erosion control features and easement widths; and
(4) The erosion and sediment control plan during the construction period, including the location of temporary seeding of exposed areas, temporary erosion and sediment controls and any other proposed measure.
(Ord. 78-O-31, passed 3-6-1978)