Landslide: Finger of Blame Points at Loggers, God : Geology: Some environmentalists are angry over the timber industry for a nine-acre swath of forested hillside that came down in Mendocino County. Louisiana-Pacific Corp. contends it was God’s will.

Whether the falling trees in this remote forest made noise is anyone’s guess. Nobody was around to hear.

But weeks later the uprooted trees--along with tons of boulders, mud and shale--are still causing a stir.

Environmentalists blame loggers for the 80-foot-deep, nine-acre swath of hillside that tumbled into the Navarro River sometime in March. The landowner, Louisiana-Pacific Corp., contends it was an “act of God.”

But no one who’s seen the chunk of earth lying at the bottom of a Mendocino County gorge is arguing over the awe it inspires. Or its rarity. Geologists say such landslides come along every few hundred years or so.

“It’s pretty special. We know river-damming slides occurred in prehistoric time, so they’re not unknown, just very, very rare,” said Robert Curry, a geology professor at the University of California-Santa Cruz. “It’s the first time we’ve had a chance to actually see one happen.”

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“Amazing,” said Karl Poppelreiter, a Mendocino County ranger who patrols the river. “And I’m the lucky schmuck to have found it.”

Poppelreiter hopped in his canoe March 24 for a trip down the Navarro. He was familiar with the river’s winding route, and he knew its calm and its reputation as a rare waterway gentle enough for amateur kayakers to navigate safely all the way to the Pacific Ocean.

It didn’t take him long to realize something was wrong.

Four miles west of his station, the water slowed Poppelreiter’s boat to a near-halt. Soon, he was floating in an unfamiliar green lake. Ahead, he could hear the rush of whitewater caused by the 500-foot-long jumble of fallen trees, boulders and mud that nearly plugged the river.

Poppelreiter briefly explored the denuded hillside, a quarter-mile high and still gurgling with underground streams and flows of mud. Then he tried to guide his canoe through the river’s tree-strewn channel.

“A novice would have died in the river that day, no doubt in my mind,” said Poppelreiter, who later posted skull-and-crossbones warnings near the Navarro’s shores. “It threw me right into the water, kind of pinballed me around, knocked me up against some logs. The force was tremendous.”

By this month, the Navarro has calmed. Some of the fallen logs and debris have moved down river, and the water has carved itself a wider channel through the slide.

But one question lingers. Was it Northern California’s winter deluges that caused the slide, or years of human tampering with the hillside?

Environmentalists, and some geologists, take the latter view.

“I call that Lake Louisiana-Pacific,” said Chris Tebbutt, standing near the slide and pointing to the placid waters that had stalled the ranger’s canoe. “They knew not to log this land. The ground is much too steep to be taking away that amount of [tree] canopy. They just weren’t paying attention to what was happening up the slope.”

Tebbutt, a member of the local Redwood Coast Watershed Alliance, says the timber company robbed the hillside of its natural protection of Douglas fir and redwoods. That let the heavy rains of January and March batter the land with unnatural force.

In addition, rotting roots, an effect of logging, weren’t strong enough to bind surface soil to layers of earth beneath it, he said.

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Others believe logging roads may have weakened the slope by guiding rainfall into man-made contours on the hill. One such road marks the upper boundary of the slide.

“Hopefully, this serves as a wake-up call to regulators,” said Kathy Bailey of the Sierra Club. She says state rules governing timber harvests along rivers are too lax. “This highlights a regulatory weakness, and that weakness could allow this to occur anywhere along our waterways.”

Louisiana-Pacific officials have surveyed the slide and insist it was caused solely by the steady winter rains. Plenty of slides, some of them very large, occurred throughout California during the winter floods, they say.

“Things like this do occur,” said Tom Thompson, resource manager for the timber company’s western division. “[But] anything dealing with the timber company in this area gets to be news.”

The state also is investigating, examining a 1988 timber harvest plan that allowed the steep river gorge to be logged. A preliminary review shows the slide was natural, the result of nearly a foot of rain in the week or so leading up to it, said Julie Bawcom, an engineering geologist for the state. And the extraordinary depth of the slide, between 70 and 80 feet, indicates that logging wasn’t to blame, she said.

“These have been occurring for thousands of years, and there’s evidence of them all over Mendocino County,” she said. “They are what form the region’s topography. To witness one of these in our working lifetimes is a wonderful opportunity.”

Both sides in the debate are paying close attention to the effects of the slide. Environmentalists like Tebbutt fear sediment from the slide will damage vital fish spawning grounds and a downriver estuary. The jumble of logs will make it dangerous for summer swimming, he believes.

Louisiana-Pacific says the slide may actually benefit the long-term health of the river and the fish that live in it, and that recreation along the river isn’t likely to suffer.

Debating the cause probably will continue, through neither side is likely to satisfy the other.

“What caused it? What caused it was a lot of rain,” said geologist Curry. “But, beyond that, these are the kinds of things you’ll never know.”