CA Geological Survey Warns of Possible Landslides - KTVN Channel 2 - Reno Tahoe News Weather, Video -

CA Geological Survey Warns of Possible Landslides

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SACRAMENTO – If you hear a rumbling and feel the ground vibrating, it may be something other than crowds rushing to the nearest holiday sale. The California Geological Survey (CGS) today reminded the public that when the weather turns rainy, the possibility of landslides increases significantly.

"Geologic phenomenon such as earthquakes and tsunamis certainly impact larger areas and tend to be more dramatic, but landslides can cause loss of life, injuries and tremendous damage in a localized area," said Dr. John Parrish, California's State Geologist and head of CGS. "Landslides tend to recur in the same locations or in areas that have been impacted by wildfires, but can happen on any sloped surface."

A landslide is any mass of earth and rock that moves downhill by sliding, flowing or falling. Large, slow-moving landslides composed of bedrock can cause extensive property damage, while debris flows, often called mudslides, move very quickly.

"People usually have time to get out of the way of the big ones; the smaller, faster ones are more challenging," said Chris Wills, who heads CGS' landslide mapping program. "If your residence is on or beneath a slope, the most important thing you can do to protect your safety is to avoid sleeping in lower-floor bedrooms facing the slope during periods of heavy rain."

For those living on slopes, it's a good idea to check for fresh cracks in the soil, areas of bare soil (the root systems of plants and trees hold soil together), and water or mud streaming downhill.

"A rumbling sound may be a sign that soil is giving way, which is how landslides start," Wills said.

Areas that received exceptional amounts of rain last year or have been subject to fires are particularly vulnerable. CAL FIRE has taken steps to mitigate the risk of landslides and debris flows from major summer fires, but residents nonetheless are asked to remain vigilant during heavy rains. Fire causes soil to become less absorbent; some burning plants give off a waxy residue and ash clogs pores in the soil, causing rainwater to run off faster and increasing erosion.

Three or more inches of rain a day or a quarter-inch an hour also increases the likelihood of a landslide as soil quickly becomes waterlogged.

More than 100 Californians have been killed by debris flows during the past 25 years. Two major landslides occurred in 2005: In January, 10 people were killed in the Ventura County community of La Conchita when, following 15 days of near-record rain, about 200,000 cubic meters of material destroyed 13 houses and severely damaged 23 others. In June, a slow-moving landslide in Laguna Beach's Bluebird Canyon caused no fatalities but destroyed 15 homes and severely damaged several others. More than 1,000 people were forced to evacuate about 350 homes.

"Unlike earthquakes, landslides typically give us some warning that they're on the way," Parrish said. "If you take a few precautions and know what to look for, you can minimize property damage and possibly save lives – including your own."

More information about landslides – including maps, tips for residents, and mitigation steps – can be found at http://www.consrv.ca.gov/CGS/geologic_hazards/landslides/index.htm.

From the California Geological Survey

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