Why did flooding continue after the rain ended? A flood related Question Read inside for more info.?

Question

On May 31, 2000, thunderstorms began dropping rain over parts of Minnesota, Iowa, Wisconsin, Illinois. Up to 7 inches of rain fell in about 12 hours. The rain ended by June1, but flooding caused by the storm lasted through June 3. Why did flooding continue after the rain ended?

Answer 1

Rivers overflowing,spring thaw,ground already saturated etc .....

Answer 2

Usually this has to do with runoff and the flood stage will crest sometime after the event happened...