>> reporter: the governor declaring a state of emergency and activating the national guard. as officials predict river levels could exceed the great flood of 1993. that claimed nearly 50 lives and damaged or destroyed some 50,000 homes. the most devastating in modern u.s. history. in the town of west alton, near st. louis, the mayor urging his 500 residents to evacuate after water levels overtopped the levee. >> this is your notice, this is serious. you need to get final preparations and go. >> reporter: parts of union, missouri under water with homes, cars, restaurants completely submerged. and one photographer even capturing video of this cabin floating away. authorities urging drivers to stay off inundated roadways, fearing they'll get stuck and swept away. >> the vast majority of deaths we've had, i can't stress this enough, is people driving into water, especially driving into water at night. >> reporter: it's the race