Tuesday, May 17, 2011

Prepare for the Worst! Erosion

This is what happens when you don't Prepare for the Worst!
Welcome back to the only Pacific Northwest blog series about natural disasters that can kill you (and your little dog too), Prepare for the Worst! This installment of everyone’s favorite natural disaster series focuses on nature’s silent killer, Erosion!

But first a quick explanation for why there was such a long break between posts. Given the Great East Japan Earthquake recently, coupled with the odd timing of my most recent post about tsunamis, (just two weeks prior) I felt it best to take a bit of time off from Prepare for the Worst. Plus, I was lazy and busy with other life events, but that's certainly no excuse for not preparing for the worst!

So, without further ado and before the desk under my keyboard washes away! Erosion!
Showers might bring flowers or CANYONS!
We all have heard that old adage that April showers bring May flowers, though there is no scientific claim I've seen to back that up, but did you know that April showers also bring May Erosion? They do!

Now, I know it isn't as catchy to say, but it's the truth! Not only that, those same showers bring erosion year round, not just in spring months! In fact, there's evidence of erosion all around us, from the beaches low to the mountains high, erosion is ever nigh! I'm done rhyming for the rest of the post. I promise.

Erosion! Natures Silent Killer!

Erosion is all around us and is as natural as the sun rising and rush hour traffic in Seattle on a Friday afternoon. All things erode and break down over time. Everything from roads to hillsides to boulders and even your computer wears away ever so slowly. In fact, everything that is touched by our skin’s acidic oils, or even water, breaks down. Nothing is immune to Nature’s Silent Killer!

However, not all types of erosion are natural disasters. Although some would argue that the numbers wearing off of on their remote qualifies as a disaster, I won’t address that here. The scale of disaster I think of when I imagine erosion is more akin to large masses of land shifting around like a puzzle that just been flipped off a table in some old western saloon. Yee-haw!
There are all sorts of erosion that can qualify as a natural disaster, and plenty of examples of it in history. The King County Office of Emergency Management (KCOEM) website on landslides points to the severe winter storms of the 1996-97 season, which led to over 100 landslides in King County alone within a two month period.

“Hey, Erosion! I thought I told you never to come in here…”
KCOEM also mentions the Nisqually Earthquake, which caused a landslide in the Renton area that dammed the flow of the Cedar River. These dammed waters then flooded the area and damaged homes along the river. In review, an earthquake (Nature’s Schoolyard Bully) caused a landslide, which caused a flood. Wow! What a chain of disasters!

Other regions have experienced worse disasters due to erosion and other related hazards. The Loma Prieta earthquake in 1989 that struck the Bay Area in Northern California suffered some of its worse damage in the Marina District of San Francisco. This was due to liquefaction of the soil that occurred because of serious design flaws in the city foundation.

In order to create waterfront property, the Marina District was built by injecting a mixture of sand, dirt, rubble, and waste (not sure what they mean by waste, but I’m sure it doesn’t smell nice) into the ground. This area of land also contains a large percentage of ground water (its on the bay), so when the earthquake occurred, the soil was loose and wet (kind of like jello pudding) and the vertical movement of the earthquake damaged more structures than if the ground had been consolidated and not water saturated. Some 12,000 residences and 2,600 businesses were damaged in Marina District alone. By the way, waterfront property is always a bad idea. Always.

Other significant damage due to soil liquefaction during the Loma Prieta earthquake included the collapse of the Cypress Street Viaduct, which had been built on a former marshland (once again, wet and loose soil). The structure was also not completely retrofitted to meet structure design guidelines after the 1971 San Fernando Earthquake (which occurred just a few hundred miles south and along the same fault line, mind you).

What can those of us in Seattle learn from this? Well, take a stroll along the Seattle Waterfront and look up toward the city; you’ll see the Alaskan Way Viaduct. Is this structure any safer than the one that collapsed in San Francisco over 20 years ago? Not according to experts who say there is a 1 in 20 chance that an earthquake will take it down in the next decade.

Another victim of soil liquefaction!
This is why the City of Seattle, in a surprising move, has proposed a tunnel project to replace the rickety, outdated structure. Given the amount of foresight and the preventative nature of the move, it shocks me to see it proposed before the structure lay in ruins. The 4.25 billion dollar (!) project will well exceed what the city, state, and county can fund for the project, so guess the most likely place the bill is going to fall to? Taxpayers, I’m sure.

However, no matter the cost, I love this move. Like I mentioned, it’s a preventative move, they are not waiting until people and cars are squeezing out the sides like a delicious peanut butter and jelly sandwich. I don’t care how much it costs, and I don’t blame leaders for the large bill. The money it would cost to clean up the mess of a collapsed viaduct would be higher than replacing it I’m sure, plus, we’d have to rebuild something else anyway. So, why not save some lives in advance and create something else safer that will be less of an eyesore anyway. That is, if they create a tunnel that is safe, state of the art, and immune to cost cutting measures that will leave us in the same place we are now.


Landslides are the most common disaster caused by Nature’s Silent Killer, erosion. They are fairly common all over the Pacific Northwest. This is due to our mountainous terrain, as well as the numerous valleys, bluffs, and various other geological features. Our region is bit more prone to landslides due to the fact that we receive so much rain throughout much of the year (once again, water + soil = disaster).

This could be YOUR viaduct next!
Also, we are prone to landslides in our area because of glaciers (Say whaaa?). It’s true! When much of the earth was covered with thick, mile high ice, this ice  covered our entire region. When it all melted, giant rivers carrying and depositing all sorts of sediment (kind of like a giant lahar!) flowed along carving out our region’s beautiful topography. The drawback to all this sediment being left behind is that it is not consolidated like hard rocks, so when water is introduced, it washes away pretty easily.

Prevention and Preparation!

You might be asking yourself, "But what can I do to avoid or prepare for erosion that will eventually destroy everything I love and hold dear?" Well, unfortunately not a whole lot, other than avoid areas where it’s obviously going to strike. These places, not surprisingly, are areas where erosion has already made its mark. Sometimes nature is throws us a curve ball, and other times it fires a laser right between the eyes.

"How do you know if landslides will strike at your home?" Well, King County advises residents to get a ground assessment or get advice from a "geotechnical" expert. That’s all well and good, but most people just aren’t going to block out a few hours on a weekend to do that. I imagine that having one of these guys assess your home is like waiting for the cable guy to show up (I'm still waiting Comcast...).

Another option is to look out for signs of potential landslides on your own. King County posts a list of potential signs of incoming landslides in a progressively alarming list of nine warning signs which I have organized into four easy to use alert categories:

I like this sign's style.
Not So Scary Signs of a Landslide
  • Doors or windows stick or jam for the first time.
  • New cracks appear in plaster, tile, brick or foundation.
Mildly Concerned About an Potential Landslide
  • Slowly developing, widening cracks appear on the ground or on paved areas such as streets or driveways.
  • Underground utility lines break.
A Landslide is Going to Destroy You
  • Bulging ground appears at the base of a slope.
  • Water breaks through the ground surface in new locations.
  • Fences, retaining walls, utility poles, or trees tilt or move.
You Are Neck Deep In a Landslide
  • You hear a faint rumbling sound that increases in volume as the landslide nears. The ground slopes downward in one specific direction and may begin shifting that direction under your feet.
  • Sinkholes - a sinkhole occurs when groundwater dissolves a vulnerable land surface, such as limestone, causing the land surface to collapse from a lack of support.
I wonder where the landslide will strike...
These warning signs are all well and good (outside of that last one which just explains why there is a giant hole in the middle of your yard or why you’re at the bottom of one) but my favorite warning sign of land slides is the eye test.

Do you live on a slope? If your answer is yes, you may be in danger of a landslide. Is there any long standing vegetation on the slope above or below your house? If your answer is no, or your slope is nothing but dirt or mud, you are in landslide central! Call the real estate agent who screwed you over in the first place and find a new place to live!

But I’m in a Landslide Right Now!

Let’s say you have found yourself in the unfortunate position of being downhill from an oncoming landslide. First of all, you obviously did not read the other numerous paragraphs I’ve written above to prevent this exact situation. Nice going, idiot. Here is what King County’s experts recommend for people like you (you moron):
  • Try to get out of the path of the landslide or mudflow.
Well, dur.
  • Run to the nearest high ground in a direction away from the path.
Well, duuuuuuuuur.
    Trees are terrific!
  • If rocks and other debris are approaching, run for the nearest shelter such as a group of trees or a building
This is fairly decent advice. Not everyone would think that a group of trees would be safe from debris during a landslide, but trees are actually great because their grounded with deep roots.
  • If escape is not possible, curl into a tight ball and protect your head.
This is obviously a last resort when all other options are exhausted. If it gets to this point, you must have screwed up somewhere along the way. Please read the rest of this post again to figure out where you went wrong.

1 comment:

  1. Wait...so what your saying is, that developing on sand is bad? And WETLANDS? Shit! There go all my plans for paving over sensitive ecosystems.