Mich. Comp. Laws § 560.138

Sec. 138. When any part of a subdivision lies within or abuts a floodplain area, the plat shall include and show the following: (a) The floodplain shall be shown within a contour line, established by the water resources commission, department of conservation. (b) The contour line shall intersect the side lines of the lots. (c) The sidelines shall be dimensioned to the traverse line from the street line and the established floodplain (contour) line. (d) The floodplain area shall be clearly labeled on the plat with the words "floodplain area".