As we travel south on the 101 freeway after departing Santa Barbara, we soon come to the small community of La Conchita, built along a narrow strip of land between ocean beaches and the hills. It’s the sort of place of which many people would say, if only I could live here!
When approaching La Conchita from the opposite direction, you can see the pile of earth that buried homes, with white crosses placed above where people were crushed to death. That sight always sends chills down my spine, particularly knowing that a mother and her three young children were in one of those homes. The people of this community will never forget what happened there in the early afternoon of January 10, 2005.
It was California’s wet season, and the rains were welcomed. Sometimes when rains come to this arid land, they come in a deluge. Such was the case on that fateful day--about four inches had fallen in the area. A landslide had occurred there in 1995, destroying some homes but taking no lives. On this rainy day in 2005, some earth that moved during the 1995 landslide moved again, sliding on a deep vein of soil wet from water that had percolated far below the upper dryer layers. The dry top layer smashed into the town with terrible force, crushing everything in its path.
In 20 seconds, 36 homes were destroyed or seriously damaged, and 10 people were dead. In this close-knit community, everyone was a friend of the deceased. For the human toll, go to www.opl.ucsb.edu/grace/lc/index.html.
The area where La Conchita now stands was first settled by railroad workers. In 1924 it became a subdivision with about 200 lots in a strip of land just 800 feet wide, beneath bluffs 600 feet high. The land topping the bluffs was agricultural and became an avocado grove requiring extensive irrigation. Those trees are visible in the photograph. After the 1995 landslide, community residents faulted over-irrigation of the groves above them as a cause of the slide, but lost a lawsuit to restrict this irrigation.
The United States Geological Survey (USGS) did a study of the area after the deadly slide (http://pubs.usgs.gov/of/2005/1067). This particular area has witnessed many pre-historic landslides. The report indicated the 2005 slide was a re-mobilization of material from the 1995 slide. A photograph of the slope in 2004 showed heavy vegetation on the soil that was to collapse on the town a year later—a telltale sign of the drainage pattern that would become catastrophic.
Who is to blame for the La Conchita landslide? Was it the people who built homes under the bluff, the county who issued building permits, the agricultural land use permitted up to the bluff’s edge, or the legal system that thwarted mitigation attempts after the 1995 slide?
Why didn’t the people move away after the 1995 slide? Probably some did, but others would not be able to afford to live elsewhere after their property values fell. People loved where they lived. They probably felt another landslide would be similar, in causing some destruction but not killing people, and accepted that risk. The deep intrusion into the town by the 2005 debris flow was probably never imagined.
California soil is notoriously unstable. Buildings are not built with basements there for a reason. Two natural phenomena common to California, earthquakes and infrequent heavy rainfall, can mobilize the soil, particularly on hillsides. (Another factor can be wildfires that kill vegetation that helps hold soil in place.)
You can look at USGS soil-slip susceptibility maps of California. I was relieved to see that the hills around Santa Barbara are mostly of low to moderate susceptibility. Further to the south and east, susceptibility ratings of “high” are typical of hilly terrain. Apparently Orange County has been plagued by soil movements damaging homes and infrastructure in many areas. Once development has occurred on unsuitable terrain, there are no affordable fixes.
I’ve learned that landslides are likely immediately after heavy rains, and that the risk continues to be elevated for months afterward. There is no way to accurately predict when or how far a landslide will travel before the fact. Some say all of La Conchita remains at risk.
After what I’ve learned about southern California, I know that the entire region is at risk— from wildfires, landslides, and earthquakes, not to mention air and water pollution. Yet the climate, natural beauty, and booming economy will continue to bring more people and more development to this fragile land.
California is like the canary in the mineshaft. It is no surprise that people there have supported environmental legislation so strongly. This is a wakeup call to the rest of the nation.