312 IAC 10-3-3 Delineation of flood plains and floodways in the absence of a Federal Emergency Management Agency designation

Sec. 3. (a) This section governs the delineation of a flood plain (or a floodway and fringe) by the department where section 2 of this rule does not apply. The delineation referenced in this section may be performed by: (1) the department; or (2) another person subject to review and approval by the department. (b) The magnitude of the peak discharge of the regulatory flood of a waterway is established. Using this discharge, the regulatory flood profile is determined. The extent of a flood plain (or a floodway and fringe) is delineated using appropriate elevations from the regulatory flood profile and the best available maps. (c) The peak discharge of the regulatory flood shall be established using standard engineering and statistical techniques acceptable to the commission. (d) The profile for a regulatory flood is determined using standard engineering techniques acceptable to the commission. A determination shall start a sufficient distance downstream from the area of interest in order to ensure reasonable accuracy. A bridge is assumed to remain open and free of debris and ice unless local conditions indicate otherwise. Where possible, the profile for a regulatory flood is correlated with known high watermarks. (e) The extent of a flood hazard area is delineated on the best available maps. Supplemental information from field surveys are used as needed to locate the boundaries of a flood plain. (f) If there is a need to delineate flood plain and detailed engineering information is not available, a flood plain may be delineated on a temporary basis using other available information or methods acceptable to the commission.