All storm drainage design shall be planned and executed so as to preserve natural topographic features and vegetative cover, to minimize change to existing topography, and to preserve natural drainage systems.
(a) Where an adequate public storm sewer is available at the plat boundary, the subdivider shall construct a storm sewer system and connect with such storm sewer line. If such a storm sewer system is not accessible, natural drainage channels with easements of adequate width shall be provided as determined by the City Engineer. Storm drainage from lots, including drain tile around basements, shall not be permitted to discharge into any sanitary sewer facility, but shall connect to an adequate drainage outlet.
(b) The subdivider shall construct all necessary facilities including underground pipe, inlets, catch basins, or open drainage ditches, as determined by the City Engineer, to provide for the adequate disposal of subsurface and surface water and maintenance of natural drainage courses. The best available technology shall be used to minimize off-site storm water runoff, increase on-site filtration, encourage natural filtration functions, simulate natural drainage systems, and minimize off-site discharge of pollutants to ground and surface water. Best available technology may include measures such as retention basins, recharge trenches, porous paving and piping, contour terraces, and swales. Storm water management shall follow the standards established in Hamilton County's Rules and Regulations governing the construction, operation and maintenance of the Hamilton County Storm Water Drainage System.
(c) When necessary, outlet ditches of closed sewers of an approved type and size shall be required as part of the construction. If same is across private property, rights-of-way or easements shall be obtained by the subdivider or developer for the construction and future maintenance. These rights-of-way or easements shall be shown on the construction plans. Whenever possible, post-development drainage patterns shall be the same as predevelopment drainage patterns. The design of streets and grading shall be such that run-off from roofs, driveways and other impervious surfaces will be collected in ditches and/or gutters in short runs three hundred (300) feet to four hundred (400) feet in length. The runoff shall then be diverted from the surface, if not already underground, into storm sewers or a natural water course. Streets shall be located away from water courses unless storm sewers are to be installed. The channel downstream of the subdivision shall be improved adequately by the developer to convey the storm runoff from the subdivision and across the adjacent property owner so that damages from erosion are minimized.
(d) The subdivider shall guard against the creation or continuation of swampy areas or stagnant pools, unless they are a component of a designed wetlands open space. The Planning Commission may require fill, swale and/or channel improvements in order to forestall such problems.
(e) Adequate measures for the protection of open and closed drainage channels shall be provided. Maintenance easement widths shall be determined by the Public Works Director. The velocity flow on an open ditch shall not exceed four (4) feet per second in soil ditches or six (6) feet per second in turf gutters. Paved gutters will be required if velocities of flow are greater than those specified or if it is otherwise likely that destructive erosion will result. Drainage ditches shall not be permitted to discharge into any sanitary sewer facility.
(f) No water course shall be altered in such a way as to change the amount or direction of flow; no fill, building or structures shall be situated in natural water courses unless provision is made for the flow of water in a manner satisfactory to the City Engineer.