Mean annual flood definition
Mean annual flood means a flood which has a magnitude (peak discharge) which is expected to be equalled or exceeded on the average once every 2.33 years and has a forty-three percent chance of being equalled or exceeded (0.43 exceedence probability) during any year, by application of the criteria defined in subsection (2) of this section.
Mean annual flood means that boundary which demarcates the extent of inundation for a flood event with between a 43% to 50% annual chance of occurrence as determined through methods described in the following document, “Guidelines for Determining Flood Flow Frequency, USGS Bulletin 17B of the Hydrology Subcommittee Revised September 1981; Editorial Corrections March 1982.” http://water.usgs.gov/osw/TRB/CohnFloodsTRB_B17B_003.pdf