Five people have been confirmed dead flooding in Colorado, four in Boulder County, and one in El Paso. A further 631 people remain unaccounted for across the state, 398 in Larimer County alone. In addition around a thousand people are known to be still stranded in isolated regions, 17 500 people have been evacuated and are living in temporary shelters and over 19 000 homes have been partly or completely destroyed.
Vehicles and other debris in Gold Run Creek to the north of Boulder on Friday 13 September 2013. Matthew Kennedy/Earth Vision Trust/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 Wednesday the ground in many areas became waterlogged, and a series of mudslides began, washing away roads and houses across fifteen counties. 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. As the state's electricity, phone and internet services broke down, many people lost contact with the outside world. Over the weekend much of the state received around 6 cm of rain, with flooding spreading further, and while the rains eased on Monday 16 September, they are predicted to resume on Tuesday.
While many people have been evacuated from the worst hit areas, many more chose to remain with their properties. Additionally in some areas it was judged unsafe to rescue people, as this could not be done without moving them via roads considered to be in extreme danger of washing away. No fresh water or food is reaching people trapped in many areas of the state.
A section of road washed away by flooding on the South Platte River in Weld County on Saturday 14 September 2013. John Wark/San Francisco Chronicle.
Authorities are hoping that as communications are restored the number of people missing in the state will begin to fall sharply, but are concerned that the number of deaths is also likely to arise. President Obama has officially declared a state of emergency in the region, authorizing the spending of federal aid money.
The event is being attributed to a low pressure system that has been hovering over Nevada for about a week, drawing moist air north from storm-hit Mexico. In many hilly areas normal ground cover has been lost due to extensive wildfires earlier this year, making slopes much more vulnerable to landslips.
See also At least eighteen deaths as Tropical Storm Manuel hits Guerro State in southern Mexico, Arizona man injured in rockfall on Mount Elden, north of Flagstaff, 13 killed by landslide in Veracruz State, central Mexico, At least one dead as Tropical Storm Juliette crosses the tip of Baja California and Collision leads to oil spill on swollen Mississippi.
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