West Seattle weather: Get ready for slide season

(WSB photo from 2009 – slide behind condo building in 1200 block of Alki SW)
If you live in a potential slide zone – it’s time to take note and take precautions: Seattle Public Utilities says the wet weather has brought our area to the brink of what’s considered slide season, which means time for a few important reminders:

With more than an inch of rainfall forecast for Seattle over the next two days, the city is expected to cross the official U.S. Geological Survey (USGS) landslide threshold for the first time this year.

“Historically, the end of October is the start of landslide season,” said Seattle Public Utilities (SPU) meteorologist James Rufo-Hill, who writes a blog on local weather conditions. “Despite the fact that we have yet to experience widespread flooding or soil saturation this season, October is already much wetter than normal, so it shouldn’t be much of a surprise that landslide season is here.”

“The latest forecast indicates that by tomorrow over an inch of rain will fall citywide. SPU neighborhood rain gauges will have recorded nearly two inches in the past three days and nearly four inches over the past two weeks. Those totals are certain to push Seattle beyond the landslide threshold developed by the USGS and SPU,” he said.

Rufo-Hill said now is a good time for Seattle residents to prepare for landslides and to learn procedures to ensure their safety. He offered these pointers for protecting yourself and your property from landslides:

· If a landslide damages your property and you have an immediate concern for your safety, leave the premises and call 9-1-1. If you see uncontrolled street water in a steep slope area, please call SPU’s Operations Response Center, at 206-386-1800.

· Seattle property owners with structures that may be affected by or endangered by a landslide should contact a geotechnical professional for structural evaluation.

· For more information about Seattle landslides, please visit: http://www.seattle.gov/dpd/aboutus/whoweare/emergencymanagement/

· Protect yourself and your property by inspecting sloping areas for indications of slope movement (such as cracks in the ground, and newly tilting trees) and erosion.

· Check your downspouts, to make sure they are functioning and routed to a safe location.

· Be sure that your irrigation system is shut off.

· Keep fill and yard waste off slopes.

To view the current conditions of the USGS rainfall threshold for landslides, please visit: http://landslides.usgs.gov/monitoring/seattle/rtd/plot.php

Rufo-Hill’s blog,“The Convergence Zone,” discusses local weather events, implications of climate change and provides raw data about Pacific Northwest weather. SPU monitors a set of rain gauges stationed throughout Seattle, providing residents with up-to-date information about weather affecting their neighborhoods. Learn the facts beyond the forecast here.

1 Reply to "West Seattle weather: Get ready for slide season"

  • John October 30, 2014 (12:02 pm)

    Halloween to April Fools – that’s the official period for Seattle DPD’s wet season.

    DPD’s rainy season restrictions are far more comprehensive than SPU’s and actually prohibit hillside activities such as dumping anything and banning all excavation (even a wheelbarrow amount).

    Sites under development receive far more attention with added restrictions. They are required to have a site visit by their Geo-technical Engineer who then writes and submits a formal report with recommendations as required.

    The report on my sites had sections on Slope Stability, Temporary Erosion Control, as well as re-iterating the Wet Season Grading Restriction.

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