16.10.120 Amount of runoff to be accommodated by various parts of drainage facility.
Various parts of drainage facility must accommodate runoff water as follows:
A. The minor drainage system such as inlets, catch basins, street gutters, swales, sewers and small channels which collect storm water must accommodate peak runoff from a 10-year return period storm. Rainfall duration shall be equal to the time of concentration or one hour if the time of concentration is less than one hour. A first quartile storm distribution shall be used for computer modeling. The following additional requirements must be satisfied:
1. Open channels carrying peak flows greater than 30 cubic feet per second shall be capable of accommodating peak runoff for a 50-year return period storm within the drainage easement.
2. Culverts shall be capable of accommodating peak runoff from a 50-year return period storm when crossing under a road which is part of the Indiana Department of Highways rural functional classification system and are classified as principal or minor arterial, major or minor collector roads.
3. Temporary water storage will not be permitted on any local street or road, except by special exception of the Board.
4. In urban areas first floor elevations of all living units, commercially or industrially used buildings, shall be such that all floors including basements shall have two feet of freeboard above the 100-year flood elevation or at the flood protection grade. In urban areas the land grade at houses shall be based upon the maximum flood of record or upon a flood which may occur once in 100 years, whichever is greater, together with a freeboard of two to three feet.
B. Major drainage systems are defined in JCC 16.10.040 and shall be designed in accordance with Indiana Department of Natural Resources Standards as described in JCC 16.10.090. [Ord. 12-1-97C § 10.]