McPhee on Debris : THE CONTROL OF NATURE <i> by John McPhee (Farrar, Straus & Giroux: $17.95; 272 pp.) </i>

In a period belatedly eager to befriend Mother Nature, America’s most distinguished nature writer has chosen to write about those who defy her. “Atchafalaya,” the first of his book’s three long essays, all originally published in The New Yorker, deals with the attempt of the U.S. Army Corps of Engineers to control the channel of the Mississippi River. “Cooling the Lava,” the second essay, tells how Iceland’s National Emergency Operation Center saved a fishing village from an erupting volcano. “Los Angeles Against the Mountains,” the third, pits the Los Angeles Flood Control District against “debris flows” in the San Gabriel Mountains. Each of the three puts a different subset of John McPhee’s formidable gifts on display.

The Mississippi, laden with silt churned up from points as remote as Montana and Alberta--thousands of tons per annum of “mountain butter,” as McPhee calls it--has long since begun to gum up its own channel and overflow into the Atchafalaya River, whose course to the Gulf of Mexico from the point where it branches off from the Mississippi is deeper, cleaner and shorter by 400 miles than the course of the Mississippi itself. Should the Atchafalaya ever “capture the channel” of the Mississippi, however, New Orleans would be cut off from river commerce, and the “American Ruhr” between Baton Rouge and New Orleans would be deprived of the millions of cubic feet of water that make its industries possible.

Channel control efforts have culminated in the Old River Control Auxiliary Structure, “the most advanced weapon ever developed to prevent the capture of a river and a handsome gift to the American Ruhr, worth three hundred million dollars.” The structure consists of seven towers whose composite weight is 2,600 tons. “Each of them is sixty-two feet wide. They are the strongest the Corps has ever designed and built . . . in grandeur and in profile they would not shame a pharoah.”

But will even this pharaonic effort suffice to preserve the channel against the might of a hundred-year flood? No one knows, but to quote McPhee quoting Mark Twain: “A discreet man will not put these things into spoken words; for the West Point engineers have not their superiors anywhere; they know all that can be known of their abstruse science; and so, since they conceive that they can fetter and handcuff that river and boss him, it is but wisdom for the unscientific man to keep still, lie low, and wait till they do it.”

When a new volcano turned the remote island village of Heimaey into a modern Pompeii, the immediate and acute effects were horrendous: Some houses were incinerated, others buried to their eaves in volcanic ash. And yet today, with the volcano cool, the village has been rebuilt. Had its harbor been clogged with congealed lava, however, no one would have bothered to rebuild the village; for without a harbor, Heimaey--a tiny island off the south coast of Iceland proper--cannot fish; and without fishing, it cannot live.

What saved Heimaey, therefore, was the decision of its rescuers to abandon its houses to the lava and try to save its harbor. They did this by implementing Prof. Thorbjorn Sigurgeirsson’s seemingly simple-minded plan to cool the lava by hosing it down with sea water. Heimaey’s initial pumping efforts--11,000 gallons a day--were more quixotic demonstrations than serious countermeasures. But when the volume of pumped seawater rose to 11 million gallons a day, Quixote was proven right. Enough of the lava was cooled to create a dam against the rest of the lava. The harbor was saved.

Pauline Kael once commented that in American movies the game is never won by brains. Typically, when the pointy-heads are talked out, our guy wades in there and settles things with his own two hands.

Not so in McPhee. Though he has a knack of presenting even the most ordinary folks in their best, most ingenious moments, his true heroes are those to whom he himself turns for instruction; namely, the professors.

McPhee’s professors are not just the smartest, they are also the most colorful, the most likable and somehow the most enviable characters on his large and populous stage, a sunny aristocracy in which Thorbjorn, the University of Iceland academic who came up with the funny-brilliant notion of turning hoses on the lava, now steps to the front rank.

The finest of the three essays in this volume, however, and in my opinion one of the finest that McPhee has ever written, is the last: “Los Angeles Against the Mountains,” a study of how greater Los Angeles protects itself against debris flows.

Debris flows are not on the list of natural hazards that most Angelenos worry about, though The Times has reported on them reliably enough. What are they? In McPhee’s words, they “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.” One recent debris flow in the San Gabriel mounains “was so full of automobiles it was like bread dough mixed with raisins.”

The entity charged with controlling nature in the guise of debris flow is the Los Angeles County Flood Control District, which does its job by maintaining an awesome set of dams and a staggering 2,000 miles of underground conduits and concrete-lined open stream channels, “a web of engineering that does not so much reinforce as replace the natural river systems.”

No one living in Greater Los Angeles--a community which has been, from the beginning, anything but a reasonable deal with nature--will read McPhee’s description of this engineering marvel without feeling that one of the region’s greatest secrets and proudest achievements has been laid open to his gaze, a feat comparable in size and hubris to the construction of the Mulholland Aqueduct. And yet impressive as McPhee is on the engineering, he is more impressive still on the genesis of debris flow itself.

Debris flow cannot be understood until one has understood such diverse natural phenomena as earthquake, brushfire, the tectonic youth of the San Gabriel Mountains and their “oversteepened” angle of repose, the chemical composition of chapparral (and chaparral ash) and not least the particular intensity of Southern California rainfall: “Some of the most concentrated rainfall in the history of the United States has occurred in the San Gabriel Mountains. . . . In January, 1969, for example, more rain than New York City sees in a year fell in the San Gabriels in nine days.”

“The setting up of a debris flow,” McPhee writes, “is a little like the charging of an eighteenth-century muzzle-loader: the ramrod, the powder, the wadding, the shot. Nothing much would happen in the absence of any one component. In sequence and proportion each had to be correct.” A brilliant image, and this reader, for one, was spellbound as McPhee explained, in effect, what a ramrod is, how the powder works, etc.

McPhee’s discussion of debris flow in the San Gabriels might loosely be called popular science; but it would be a mistake to suppose that there exists anywhere in the scientific literature some single, comprehensive account of that phenomenon which McPhee could simply write up (or write down) for The New Yorker. No, that kind of one-step popularization surely has its honorable place, but McPhee achieves something different: first, a synthesis of primary scientific work in several fields; second, the presentation of that synthesis in language any serious reader can understand.

No one does this as well as he does, and few even attempt it. Fewer, even among the best popularizers of science, attempt as he does in this piece to combine scientific synthesis with a description of engineering in action--and then to situate the engineering in a vivid and deeply instructive human context. McPhee is not just the master, he is nearly the inventor of this kind of writing; and what he has invented may ultimately be a model for more than writing alone. In the coming decade, we all have a lot of environmental thinking ahead of us. McPhee offers a unique clue to how we should proceed.