Since its inception, the city of Los Angeles has been dealing with natural hazards. One geological event that puts a burden on the city is called a debris flow. A debris flow is a moving mass that is composed of water mixed with solid material that is normally larger than sand size. Debris flow episodes tend to carry loose material like mud, sand, soil and boulders over far distances. Since debris flows are made up of large loose flowing material they tend to be deafening. John McCaffery, a man who is educated in debris flows, described the sound of an oncoming flow as that similar to thunder. The loud sound that he describes was in fact the large boulders, the size of a car, smacking against each other while they were being displaced
