Engineering Geologist: Rock and mudslides on the way


REDDING, Calif. - Don't be surprised if we see an increase in rock and mudslide in the coming weeks in the Northstate.

That's the opinion of Gary Simpson, a certified engineering geologist with SHN Engineers & Geologists, Inc. based in Eureka, Calif.

Simpson said the rain that followed snowfall in the Northstate the week of January 7 increases the potential for slides because it creates more run-off.

"Rain on snow events have a very high potential to create the mudslides and rock slides, but also a lot of flash flooding and flooding in low-lying areas," Simpson said. "These are really the peak events that will make run-off that's more significant than the amount of rain we're receiving."

He warned drivers to be extra aware of their surroundings and to not only keep their eyes on the road, but above it as well.

"My advice would be make sure you keep your eyes open, including looking up the hill," he said. "I mean, I know it's hard to look up a hill when you're driving a car, but expand your field of view so you're seeing what's in front of you as well as what's above you. I think that is critical."

Simpson said much of the geology of the Northstate tends to weather easily and is susceptible to high levels of moisture.

"Especially the ones in the hills to the west of Redding have been through the 'tectonic ringer', if you will. They're all highly deformed rocks," he said.

He also referenced marine rocks closer to the coast and volcanic rocks in Lassen National Forest as examples.

He said seeing a small number of rocks fall down a hillside could indicate more will follow. He also mentioned water flowing off of a hillside and trees falling laterally down a hillside as obvious indicators of a potential slide.