Did you know? Floods do not only occur near bodies of water. Heavy rainfall can flood entire cities.    Unanticipated flooding can happen in areas previously considered out of flood reach.    About one in four flood disasters occurs in areas with a low to moderate risk of flooding.    Property damage from flooding now totals more than $1 billion each year in the United States.    The most dangerous type of flooding is a flash flood, which usually occurs within minutes or hours of a heavy rainfall, a dam or dike failure or a large break in an ice jam.