John McPhee: "Los Angeles Against the Mountains"

The San Gabriel Mountains

Back in 1988, John McPhee wrote in the New Yorker about the geology behind what's happening in the Los Angeles area right now: first you have fire and then you have the massive debris flows off the San Gabriel Mountains after a heavy rain. The excerpts below are from Los Angeles Against the Mountains II, October 3, 1988, The New Yorker):

...In November, 1933, the chaparral burned in numerous watersheds above Pasadena, La Canada, La Crescenta, and Montrose, and slopes were left black and bare. Rainfall in amounts that the Flood Control District called a "Noah-type storm" followed in the last days of the year, mobilizing, on January 1, 1934, a number of almost simultaneous debris flows that came out of the mountains, went through the orchards and into the towns, killed dozens of people, destroyed hundreds of houses, and left boulders the size of icebergs far down the fans...Out of Pickens Canyon came a debris slug of such magnitude that it traveled all the way to Foothill Boulevard, crossed it, and passed through the business district of Montrose. 

A boulder eight feet in diameter came to rest on the main street of town, three miles south of the mountain front. The New Years Day Flood, as people still refer to it, killed thirty-four in Montrose and neighboring towns, ruined nearly five hundred houses. All over the bajada, Model A's were so deeply buried that their square roofs stuck out of the mud like rafts. Streets of La Crescenta were like braided rivers of Alaska, with channels of water looping past islands of debris...

...There are three debris basins along Country Club Drive. There were two in 1964. The upper one failed. The slug that came down the street and invaded houses killed Aimee Miller, the wife of Frank Sinatra's piano accompanist. Her home was knocked off its foundation. Her husband was swept downhill and into a debris basin. He survived by hanging on to a Volkswagen that was part of the debris...

Sally Rand lived in Glendora, pretty far up the fan. At Christmastime that year[1968], in the Kingdom of Rubelia, she did her phan dance at Mike Rubel's castle. 

Four weeks later came the devastating rain. Listening to it thump his roof, Art Cook[City Manager of Glendora] said to himself, "This is the night. I'd better get down to the Hall." He got into his car and went down Palm to Grand; as he turned onto Grand, the flow met him. It picked up his car and carried it a quarter of a mile. ("I just sat there, scared as hell.") Eventually, his slithering wheels found traction, and he drove off none the worse for having been part of the snout of the debris. "A wave six to eight feet high came out of Rainbow Canyon," he said. "The rock, debris---everything was suspended in the liquid mass. Horrendous boulders, trees, car bodies were suspended in the mass. It sounded like a train---a runaway express train. Just a roar."