The rental trailer wasn’t in great condition before the muddy rivers spilled their banks in Columbus, Ind., but it provided a home for the family of five. The parents worked in the fields and their baby played happily on the kitchen floor in the evenings, surrounded by the chatter of the two elder siblings doing homework and the smells of supper being prepared. Then summer came, and with it came flooding rains — 11 inches within seven hours. Levees broke. Dams failed. Much of the Midwest was left underwater, with places in Indiana seeing the worst flooding the state had experienced in more than a century.