CEDAR RAPIDS, Iowa—This once-bustling city was facing all the challenges of former manufacturing hubs across the country when it wrote a 25-year plan to revive its business and residential life.

The plans didn’t go very far, though—until the Cedar River flooded in 2008. Judged at the time to be one of the worst natural disasters in U.S. history, the flood left 10 square miles, or 14% of Cedar Rapids including City Hall and much of downtown, underwater.

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