(A) Runoff quantities shall be computed for the area of the parcel under development plus the area of the watershed flowing into the parcel under development. The quantity of runoff which is generated as the result of a given rainfall intensity shall be computed by a method, as approved by the County Surveyor.
(B) Various parts of a drainage facility shall accommodate runoff water as follows:
(1) The minor drainage system such as inlets, catch basins, street gutters, swales, sewers, and small channels which collect stormwater shall accommodate, at a minimum, peak runoff from a ten-year return frequency storm.
(2) These minimum requirements shall be satisfied:
(a) The allowable spread of water on collector streets is limited to maintaining two clear ten-foot moving lanes of traffic. One lane is to be maintained on local roads, while other access lanes (such as a subdivision cul-de-sac) can have a water spread equal to one-half of their total width.
(b) Open channels carrying greater than 30 cubic feet per second shall be capable of accommodating peak runoff for a 24-hour, 50-year return frequency storm within the drainage easement.
(c) Culverts shall be capable of accommodating peak runoff from a 24-hour, 50-year return frequency storm when crossing under a road which is part of the INDOT rural functional classification system.
(d) Rear and side lot swales shall not carry more than four cfs and only two cfs if a swale crosses a sidewalk.
(3) Major drainage systems are defined in § 153.182 and shall be designed in a method approved by the County Surveyor.
(Ord. 1997-16, passed 12-8-1997; Ord. 2005-01, passed 2-17-2005) Penalty, see § 153.999