(A) The drainage facility shall be such that all habitable structures are free from a 100-year flood. Also, all land alterations shall be accomplished so as to prevent damage to adjoining property. Provision must be made for receiving and conveying off-site runoff through the site and for preserving existing drainage systems (including field tiles). A natural or surface channel system shall be designed with adequate capacity to convey through the development the storm water runoff from all tributary upstream areas. This bypass channel shall be designed to carry the peak rate of runoff from a 100-year storm, assuming all storm sewers are blocked and that the upstream areas are fully developed.
(B) Various parts of a drainage facility must accommodate runoff water as follows:
(1) 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. These minimum requirements must be satisfied:
(a) The allowable spread of water on collector streets is limited to maintaining 2 clear 10-foot moving lanes of traffic. One lane is to be maintained on local roads, while places can have a water spread equal to 1/2 their width. No reverse crown roadways will be constructed;
(b) 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;
(c) 1. Culverts shall be capable of accommodating peak runoff from a 50-year return period storm with less than 1 foot of backwater when crossing under a road which is part of the Indiana Department of Transportation rural functional classification system and is classified as a principal or minor arterial or major or minor collector road.
2. Driveway culverts shall have a minimum diameter of 12 inches and a minimum length of 20 feet.
(Ord. 1995-10 § IX, passed 10-13-1995)