Summer fires plus winter rain raise landslide danger

By Gordon Williams 

The drenching rains of fall and winter have ended the summertime danger of wildfires in Washington state. But now the sequence of fire and rain has set the stage for yet another potential disaster — landslides and mudslides. Thus, heavy rain brought a recent mudslide warning to parts of Western Washington — the first of the season, but certainly not the last. 

The United States Geological Survey (USGS) warns, “Post-fire landslide hazards include fast-moving, highly-destructive debris flows that can occur in the years immediately after wildfires, in response to high-intensity rainfall events.” Fire strips the ground bare, and rain starts the mud flowing.

Fortunately, there is advice from the USGS, the Federal Emergency Management Agency (FEMA) and the American Red Cross to help you spot a landslide in the making and to keep you safe if you are caught in a slide. There are also steps you can take to make your property more secure from slides.

First bit of advice from FEMA is to know the landslide risk in your area. “Contact officials for information on local landslide hazards,” FEMA says. “Ask whether there is a landslide map for your area or how to get your property checked. Avoid new construction in areas at risk for a landslide, such as steep slopes or property close to cliffs or near drainage ways or streams.” Make sure you know about past slides in the area. A slide in the past could identify ground that is ripe for slides in the future.  

FEMA notes that there is a difference between a landslide and a mudslide. “A landslide is rocks, earth or other material moving down a slope. A mudflow is a landslide that is combined with up to 60 percent water.” The distinction is purely technical — you don’t want to get caught in either.  

The USGS adds to FEMA’s list of what makes land landslide prone. It warns about homes built at the base of slopes, or at the top or bottom of hills created by fill. Further, it lists indicators that could warn you that a slide may be imminent: 

• The sudden appearance of standing water or soggy ground in areas that have not been wet before.
• New cracks or bulges in the ground, street pavement or sidewalks. 
• Tilting or cracking of concrete floors and foundations.
• Leaning telephone poles, trees, retaining walls or fences. 
• Sticking doors and windows which did not stick before.
• Rapid increase in creek water levels. 

As to who to contact about your potential landslide risk, USGS suggests the state geological survey, the state Department of Natural Resources, or the Department of Geology at a local college or university. If your locale appears to pose a real risk, ask for a referral to someone who can study your site, assess the danger and recommend measures to reduce the risk. 

What should you do if a landslide does seem imminent?  Here the Red Cross offers advice. 

• Listen for unusual sounds that might indicate moving debris, such as trees cracking or boulders knocking together.
• If you are near a stream or channel, be alert for a sudden increase or decrease in water flow. Notice whether the water changes from clear to muddy. That could mean there is debris flow activity upstream.
• Be especially alert while driving — watch for collapsed pavement, mud, fallen rocks and other indications of possible debris flow.  

If you see any of these danger signs, be prepared to evacuate immediately. Inform affected neighbors if you can, and contact your public works, fire or police department. 

A severe storm can trigger a landslide without much warning. If there is a risk of slides, keep listening to local news stations on a battery-powered radio for warnings and evacuation alerts. Stay awake until the danger has passed. Many deaths from landslides occur while people are sleeping, says the Red Cross. Even if there is no evacuation order, and it seems safe to do so, move your family to someplace secure until the danger has passed.

When you do return home after a slide, stay away from the slide area, as one slide may be followed by another.

• Check for injured or trapped persons, but don’t enter the slide zone to assist.  Pass on their location to rescuers.
• Direct rescuers to anyone who might need special assistance —someone elderly or disabled, someone with infants.
• Check your dwelling for damage and report downed power lines or broken gas lines to local utilities and rescuers. 

Stay tuned to your radio to hear emergency messages or new warnings. Not only is there the danger of further slides, but debris could have blocked rivers and streams, causing sudden flooding.

The American Red Cross Landslide Safety Checklist is available online at RedCross.org and in nine languages to ensure the maximum number of people are able to prepare at a time when it may be more important than ever.