All areas not within the City of Petaluma but within the boundaries of the “Areas of Special Flood Hazard” identified by the Federal Insurance Administration through a scientific and engineering report entitled “The Flood Insurance Study for the County of Sonoma” dated May 31, 1979, or any updates thereto and which are also within the City of Petaluma planning area as shown on the Petaluma General Plan are hereby prezoned to the FP-C (Flood Plain-Combining Zone) or FW (Floodway Zone) in accordance with the principles set out in Sections 6.040 through 6.050 and this Chapter.