Indiana Code 14-8-2-99 defines floodplain as "the area adjoining a river or stream that has been or may be covered by floodwater". The amount of flooding used to establish permitting jurisdiction is known as the regulatory flood. The regulatory flood is defined in 312 IAC 10-2-35 (Adobe pdf file) as "a flood having a 1 % probability of being equaled or exceeded in a year as calculated by a method and procedure that is approved by the commission. The regulatory flood is equivalent to the base flood or the 100-year frequency flood." The floodplain is divided into two districts: floodway and fringe. Proposed new developments and improvements are subject to different floodplain regulations depending on the location in relation to the floodplain.