North Bay preps burn areas ahead of storm, risk of mud and debris flow
OAKLAND, Calif. (KTVU) - In the Wine Country burn areas, most eyes are on the skies as rain threatens to saturate unstable hillsides, which could produce mud and debris flows.
It's anybody's guess how significant these rains will be and what it could potentially do to the steep terrain that may only be clinging to some hillsides.
Just a year ago, any worries about landslides were rooted in unending "atmospheric river" storms totally saturating the hillsides. This year, even the mostly dry winter still produces fear because the fires denuded so much of the land above of trees and brush that hold the hills together.
Wednesday night’s rain will be watched by the county's Emergency Operations Center which is only partially activated right now. "We're getting people ready for an activation and we'll be sending out regular alerts so that people stay on top of this. We have rain gauges throughout the county. We have creek and river gauges so we're monitoring those very closely. And, if the situation changes, we'll activate as according and get wireless emergency alerts out to people as well," said Interim Sonoma County Emergency Services Director James Colangelo.
For example, Hood Mountain, which looks out over Sonoma County, is an area where danger is increased. It’s closed indefinitely because the terrain is so steep and the mountain so bare, landslides are highly possible as they are at neighboring Sugar Loaf Ridge Park.
The Reibli-Wallace neighborhood, with numerous surviving homes, also finds itself at risk. These areas are at the most risk because they have weak rocks underlying a top layer where at least two-thirds of that top layer are moderately to highly burned.
"As you've said, we've had a relatively dry winter, but we've had some rains come in and they've been light and intermittent and so it's allowed some of the vegetation regrowth to start, which is key to stabilizing hillsides," said Colangelo.
According to the U.S. Geological Survey, places like these face and 80 to 100 percent risk of mud or debris flow because, with just a short, intense rain burst, like a quarter inch in 15 minutes, it can happen.
If there is any good news to all of this, it is that these hillsides in this region are in far better condition than in southern California, which has already experienced deadly landslides. The serious concern in Wine Country is if they face another relentless string of atmospheric river storms.
Heavily burned areas in Napa County such as Atlas Peak, Mt. Veeder and others are under similar risk and are being closely watched.