According to the nonfiction book, Janesville, what disaster happened soon after the announcement that the GM plant would be closing?

Soon after the announcement that the GM plant would be closing, more than seven inches of rain fell onto land still soaked from a harsh, snowy winter. The waters spilled over the downtown river wall, inundated the Mole-Sadler housing development, submerged Traxler Park, and turned farms into shallow lakes. On Main Street, water filled the shops and offices. The Rock River crested at 13.51 feet, 4.5 feet above flood stage. The county estimated the damage at $42 million.