Santa Barbara County knew mudslides were a risk. It did little to stop them

During severe winter storms, Cold Springs Creek above Montecito turns into a torrent of mud, uprooted trees and shed-size boulders as it drains three square miles of sheer mountain front. The only thing protecting the people, homes and businesses below is a low dam that the Army Corps of Engineers built in 1964 at the mouth of the creek’s canyon, forming a basin between the steep banks to catch the crashing debris. Over the decades, the basin filled up with sediment and grew thick with brush and trees. Few officials gave much thought to the condition of the old structure — or to that of the 16 other basins built along the mountains’ edge from Santa Barbara to Carpinteria — until the Thomas fire last December left the slopes bare and vulnerable to rapid erosion. On Jan. 9, a storm unleashed mudslides that ravaged Montecito, killing 23 people, destroying 130 homes and causing hundreds of millions in damage.

An eight-month Times investigation found that government officials did not heed decades-old warnings to build bigger basins that could have made the mudslides far less catastrophic — and that Santa Barbara County failed to thoroughly empty the existing basins before the disaster, drastically reducing their capacity to trap debris. County flood control officials and the Army Corps had known for half a century that there were too few catchments and that the ones they had were far too small to stop the enormous debris flows that the Santa Ynez Mountains were prone to produce. In 1969, the Corps’ district engineer for the region, Col. Norman E. Pehrson, issued a dire warning to the county about the Montecito area. “The danger of loss of life and the menace of public health is great,” said a memo summarizing Pehrson’s conclusions five years after the Cold Springs Creek basin and five others were built in 1964.

The catchment on Cold Springs Creek — about the size of a Little League baseball field — has a 16-foot high dam with a culvert at the bottom to let water and mud pass through. It was designed to stop 20,000 cubic yards of debris. But even after it was cleared out in 2005, the basin still only had two-thirds of its capacity, a county survey indicated. During a major mudflow, that reduction would enable 7,000 cubic yards of storm debris that could have been trapped to flow into Montecito. (A cubic yard is about the size of a washing machine.) It wasn’t only the Cold Springs Creek basin that had shrunk, according to records included in a 231-page county report on state of the flood control system, published online six months before the January disaster. Altogether, the 11 catchments surveyed had only 44% of their designed capacity. But neither the flood control agency nor the community was worried. In documents released to The Times — in response to a public records request seeking all communications or records about the condition of the basins — no officials remarked that the catchments were more than half full with sand and rocks. At the time, the mountains were stable, covered in thick chaparral. Then last December, the fire came.

Rest of the story here:

https://www.latimes.com/local/california/la-me-montecito-debris-basins-20181220-htmlstory.html