For all new construction and substantial improvements of residential structures, the lowest floor elevation (to include basement) of new residential structures shall be elevated to a minimum of one foot above the regulatory flood elevation; except that in Zone AO, the lowest floor (including basement) shall be as high as the depth number in feet on the effective FIRM above the highest adjacent grade or two feet if no depth number is specified on the effective FIRM. (Ord. 3477 § 1, 2019; Ord. 3210, 2011; Ord. 3097, 2007).