Tuesday 1 October 2013

Five killed by Colorado rockfall.

Five hikers have been killed and a teenage girl suffered a broken leg after a rockfall hit a viewing station overlooking Agnes Vaille Falls in Chalk Creek Canyon in Chaffee County, Colorado, on Monday 30 September 2013. Around 100 tonnes of rocks, some described as boulders the size of cars,  are said to have fallen following heavy rains in the area, though it has not yet been established that the two are connected. Landslides are a common problem after severe weather events, as excess pore water pressure can overcome cohesion in soil and sediments, allowing them to flow like liquids. Approximately 90% of all landslides are caused by heavy rainfall. The area is still unstable, and engineers from the nearby Climax Molybdenum Mine have been asked for advice on recovering the bodies of the deceased. 

A helicopter from the organization Flight for Life at the scene of the Chalk Creek Canyon landslide. James Redmond/The Mountain Mail/AP.

Heavy rains began to fall across much of the state on Monday 9 September 2013, with over 38 cm falling over the next five days, nearly half the average yearly rainfall, leading to what has been described as a 'hundred year flood'. By 11 September the ground in many areas became waterlogged, and a series of mudslides began, washing away roads and houses across fifteen counties.

The event is being attributed to a low pressure system that hovered over Nevada for about a week, drawing moist air north from storm-hit Mexico. In many hilly areas normal ground cover had been lost due to extensive wildfires earlier this year, making slopes much more vulnerable to landslips.

The approximate location of the 30 August 2013 Chalk Creek Canyon Landslip. Google Maps.

Follow Sciency Thoughts on Facebook.