How To Know If Your Home Is At Risk For Mudslides

When rain hits L.A., buildings, property and roads at the bottom or mouth of ravines or drainage courses are at risk for mudslides and debris slides, which can include trees and boulders. Land that's been burned within the past year is also especially vulnerable.

Experts do their best to predict which areas are in danger through a combination of satellite imagery, topography, on-the-ground mapping, rainfall estimates and the history of mudflows in an area, but there is no way to forecast such events with 100% certainty.

The U.S. Geological Survey issued its own map, which shows its preliminary assessment of the areas most likely to have debris flows during an intense rain.

Francis Rengers, a geologist with USGS who spoke with KPCC after the Montecito mudslides, summed it up like this: "If there's a big hill behind you, it's best to get out and play it safe."

And so, caution is advised. The California Department of Conservation recommends that anyone in at-risk areas be alert to unusual rumbling sounds, avoid sleeping in first-floor bedrooms facing precarious slopes, and pay attention to the amount of rain that's falling — once it exceeds three or four inches per day (or a quarter of an inch each hour), it's created a danger zone.

For those putting together a plan to stay safe, Rengers also offered these tips:

• Heed evacuation orders. Mudflows can move extremely quickly — up to 50 mph. So if you're told to leave your home, please do.
• Follow weather forecasts. Know when the rains are coming your way, so you can prepare your next move.
  
• Know where your shelters are. Look up where nearby shelters are — and multiple routes to get there, in case the roads are blocked.

For ongoing updates on mudflow forecasts, call the L.A. Department of Public Works at 626-458-6164, Monday through Thursday during regular business hours.

This story has been updated. A portion of it originally ran on KPCC.org.

UPDATES:

Jan. 30, 2019, 2:30 p.m. : This article was updated to remove time-sensitive weather forecasts from the previous year.

This article was originally published Nov. 28, 2018.

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