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14 Mud Flow/ Debris Flow A MUD FLOw is a mass of water and f i ne-gra i ned earth materials that flol'ls down a strealn, ravine, canyon, arroyo or gu I ch. I f more than ha I f of the so I' ds I n the mass are larger than sand grains--rocks, stones, boulders-- the e~ent Is ca I I ed a JEdR I 5 FLOW. Characteristics Debris and mud flows are a combination of fast moving water and a great volume of sediment and debris that surges down 5 lope with tremendous force. fhe cons I stancy 15 like that of pancake batter. They are sim! lar to flash floods and can occur suddenly without time for adequate warning. When the drainage channel eventually becomes less steep, the liquid mass spreads out and slows down to form a part of a debris fan or a mud flow deposit. ,In the steep channel Itself, erosion Is the dominant process as the flow picks up more solid material. A drainage may have several mud flows a year, or none for several years or decades. They are common events in the steep terrain of Colorado and vary widely In size and destructiveness. Cloudbursts provide the usual source of water for a mudflow in Colorado. Consequences r""ud/debris flows ruin substantial improvements with the force of the flow itself and the burying or erosion of them by mud and .debris. The heavy mass pushes In walls, removes buildings from foundations, fills in basements and excavations and sweeps away cars, trucks, heavy equipment and other substantial objects. 80ulders and trees swept along by the muddy mass demol ish bui ldings, flatten fences and uti llty poles. In mountain areas, portions of valleys have been eroded to a depth of several feet by the flow process. Aggravating Circumstances The likel ihood of mud flows and mud flow damage 15 increased by actions which increase the amount of water or soi Is