John McPhee is the best nonfiction writer alive. My opinion, of course. But I happen to be right. Nobody describes anything better. No writer does a better job of digging into subjects most would find dull (rocks, pine barrens, river levees, minor species of fish) and making them not only interesting but relevant. Sometimes extremely so.
Take what he wrote in The Control of Nature about the Mississippi river, describing, among much else, what would happen to New Orleans when a levee failed. Which, ineviably, one would. In a chapter titled Achafalaya, McPhee handicapped the Army Corps of Engineers against the Mississippi. That was in 1987. The New Yorker ran it again in 2005, after Hurricane Katrina gave McPhee’s words the ring of phophesy.
Another chapter in The Control of Nature is “Los Angeles vs. The San Gabriel Mountains.” That one has special relevance today, when torrential rain on mountains denuded by fires brings the threat of mud slides — a term that doesn’t describe what really happens. McPhee:
|In the blue light they saw a massive blackness, moving. It was not a landslide, not a mudslide, not a rock avalanche; nor by any means was it the front of a conventional flood. In Jackie’s words, “It was just one big black thing coming at us, rolling, rolling with a lot of water in front of it, pushing the water, this big black thing. It was just one big black hill coming toward us.”|
|In geology, it would be known as a debris flow. Debris flows amass in stream valleys and more or less resemble fresh concrete. They consist of water mixed with a good deal of solid material, most of which is above sand size. Some of it is Chevrolet size. Boulders bigger than cars ride long distances in debris flows. Boulders grouped like fish eggs pour downhill in debris flows. The dark material coming toward the Genofiles was not only full of boulders; it was so full of automobiles it was like bread dough mixed with raisins. On its way down Pine Cone Road, it plucked up cars from driveways and the street.|
Geologists call mountain-building “orogeny.” In his Pulitzer-winning book on geology, Annals of the Former World, McPhee explains, “in the fight between orogeny and erosion, erosion always wins.” Fires side with erosion. Rain does too, especially when teamed with fires.
It is important to understand, if you live on or under their slopes, that the mountains of Southern California are brand new and not all well built. There are volcanoes that grow slower than some of these mountains, and come down slower too. Many of the canyons and ravines in the San Gabriels — the Big Tujunga, the Pacoima — are flanked by dirt whose angles of repose nearly exceed the temporary frictions that hold the land in place. Water-soaked dirt can weigh more than rock, and will seek a level lower than its own. Burn off the desert chapparal that carpets the slopes, and debris flows become certain once the rain soaks in.
So that’s not just what to watch for in the current heavy weather. It’s what to expect.