Various parts of a drainage facility must accommodate runoff water as follows:
(A) Minor drainage systems.
(1) The minor drainage systems such as inlets, catch basins, street gutters, swales, sewers and small channels that 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 allowable spread of water on arterial and collector streets is limited to maintaining two clear 10-foot moving lanes of traffic. One lane is to be maintained on local streets, while marginal access streets can have a water spread equal to one-half of their width.
(2) 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.
(3) 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 Transportation rural functional classification system and are classified as principal or minor arterial, major or minor collector roads.
(B) Major drainage systems. Major drainage systems are defined in § 157.07 and shall be designed in accordance with Indiana Department of Natural Resources Standards.
(Ord. 2000-22, passed 12-28-00)