1. 1.Debris flows, sometimes referred to as mudslides, mudflows, lahars, or debris avalanches, are common types of fast-moving landslides.
2. 2.These flows generally occur during periods of intense rainfall or rapid snow melt.
3. 3.They usually start on steep hillsides as shallow landslides that liquefy and accelerate to speeds that are typically about 10 miles per hour, but can exceed 35 miles per hour.
4. 4.consistency of debris flows ranges from watery mud to thick, rocky mud that can carry large items such as boulders, trees, and cars.
5. 5.When the flows reach flatter ground, the debris spreads over a broad area, sometimes accumulating in thick deposits that can wreak havoc in developed areas.
6. 6.Every year, landslides in the United States cause approximately $3.5 billion in damage, and kill between 25 and 50 people.
7. 7.Casualties in the United States are primarily caused by rockfalls, rock slides, and debris flows.
8. 8.Landslides often accompany earthquakes, floods, storm surges, hurricanes, wildfires, or volcanic activity. They are often more damaging and deadly than the triggering event
9. 9.The May 1980 eruption of Mount St. Helens caused the largest landslide in history— a rock slide-debris avalanche large enough to fill 250 million dump trucks to the brim traveled about 14 miles, destroying nine highway bridges, numerous private and public buildings, and many miles of highways, roads, and railroads. The debris avalanche also formed several new lakes by damming the North Fork Toutle River and its tributaries.
10. 10.In July 1994, a severe wildfire swept Storm King Mountain, Colorado, denuding the slopes of vegetation.
11. 11.Heavy rains on the Storm King Mtn. in September of ‘94 resulted in numerous debris flows, one of which blocked Interstate 70 and threatened to dam the Colorado River.