There’s nothing wrong with what the reporter said. He doesn’t mean that only 100 acres will be flooded. He is simply stating that within 30 minutes 100 acres was flooded with a foot of water. Just showing the speed with which the flooding is taking place.
by my math that is only 1.086 million gal/min far less then the 12 million gallons/second in the headline:
((100 acres x 43560 sf/ac x 1 ft deep)x 7.48 gal/cu. ft.) / 30 minutes