Apart form causing death and injury directly, tornadoes and bizzards can also cause floods. Naturally, floods are usually caused by heavy rainfall, but whichever way they are created, they can be very destructive. The most dangerous and dramatic ones are know as flash floods. In June 1976, hot air blew north form the Gulf of Mexico, bringing huge thunderstorms to the Big Thomson Gorge, where they released 10 inches of rain in six hours. All mountain streams filled up and met at the Big Thomson Gorge. The water then flowed through the canyon, removing everything in its path, killing 139 people, and causing damage worth $36 million. Other floods on record have developed more slowly but have been equally destructive.