Just days after the family of five was buried by a rock slide in Chafee County, the Colorado Department of Transportation says U.S. Highway 6 is closed between Interstate-70 and Colorado Highway 119 after large rocks fell on the roadway in Clear Creek Canyon on Thursday. No injuries were reported, but at least one rock was the size of a small car.
Rockslides occur when rock and soil slopes are weakened through saturation by snowmelt or heavy rains, such as those Colorado has experienced in the last month. Contributing factors include excess weight from accumulation of rain or snow, stockpiling of rock or ore, from waste piles, or from man-made structures may stress weak slopes to failure and other structures. Slope material that has become saturated with water may develop a debris flow or mud flow. The resulting slurry of rock and mud may pick up trees, houses, and cars, thus blocking roadways and bridges.
Landslides occur in every state and U.S. territory, but the Appalachian Mountains, the Rocky Mountains and the Pacific Coastal Ranges are known for severe landslide problems. Any area composed of very weak or fractured materials resting on a steep slope can and will likely experience landslides. It is estimated that in the United States, they cause in excess of $1 billion in damages and from about 25 to 50 deaths each year.
The U.S. Geological Survey offers these landslide warning signs:
- Springs, seeps, or saturated ground in areas that have not typically been wet before.
- New cracks or unusual bulges in the ground, street pavements or sidewalks.
- Broken water lines and other underground utilities.
- Leaning telephone poles, trees, retaining walls or fences.
- Offset fence lines.
- Sunken or down-dropped road beds.
- Rapid increase in creek water levels, possibly accompanied by increased turbidity (soil content).
- Sudden decrease in creek water levels though rain is still falling or just recently stopped.
- A faint rumbling sound that increases in volume is noticeable as the landslide nears.
- Unusual sounds, such as trees cracking or boulders knocking together, might indicate moving debris.