Disaster Zone

Mud Slide in Washington State

Rain, gravity, clay = Slide

by Eric Holdeman / March 24, 2014 0

The very large mud slide in Washington State is a reminder of a number of things about the hazard, response operations and what we can expect in the future.

I have been expecting mud slides in Western Washington since the significant increase in rainfall began after the first of this year. For Snohomish County they have had 15.6” of rain (about half of what we’d get on average for a year) in the first three months of 2014.

What makes these slides predictable is the combination of heavy, persistent rainfall combined with hillside slope, gravity and the in most cases a layer of clay soils that can rapidly give way leading to the type of slide we observed in Oso, Washington.

 Oso mud slide

The picture above says it all about what the survival rate might be for people in their homes and hit directly by a slide this massive.

I have to say that I more expected slides to happen in the City of Seattle where they have an extensive history and written record of slide areas in the city. As noted in this linked story, people have to decide how much risk they are willing to accept. Unfortunately, not many people take the time to investigate the natural or technological hazards when they are looking to purchase a home. For instance, being near the water, of any type, lake, stream, ocean, and on a hillside with a view always brings increased risks.

Today the Governor was notified that the State of Washington was being given a limited Emergency Declaration, not to be confused with a Presidential Disaster Declaration. This one allows for Federal resources to be brought to bear to assist in the emergency response—at the Federal Government’s expense. Assistance of this type includes an incident support team, program specialists, and an Incident Management Assistance Team (IMAT).  If there is to be a Presidential Declaration it will take a more formal process to have that happen.

As to what to expect in the future from climate change in the Pacific Northwest:

• More frequent and severe storms
• Increase levels of rainfall due to warmer air temperatures
• The above will lead to an increased risks of flooding, failure of flood control infrastructures and yes, an increased chance of mud slides.

One of the big tasks for the local emergency management officials now is accounting for the missing.  Being listed as missing is not the same as "being missing."  People evacuate and go to live with friends or relatives, etc.  Finding the living is an ideal task for social media.  It is how students accounted for who was killed in the Virginia Tech Shooting from a few years ago.

 Claire Rubin shared the climate change link story above.