Tsunami Mitigation

The zone has produced earthquakes measuring M8.0 and above at least seven times in the past 3,500 years. The intervals between quakes vary: from as little as 140 years to as much as 1,000. The last one occurred just over 300 years ago. Although scientists cannot predict when the next earthquake will occur, the region is within the window for a significant event.
The above source has some MAPS -- I love maps enough that I got a fancy certificate in GIS -- so you should actually LOOK at it. I've lived in Aberdeen over five years and basically it's mismanaged and all my efforts to get anything done here have been stymied, so there is little threat that anything I say about Aberdeen will result in development here.

But some of the issues Aberdeen has will be relevant to other towns in the region, so since this is the place with which I am familiar, this is the town I shall use for case studies -- or "examples" -- most of the time.

The above linked piece is two pages and page two says 77% of Aberdeen’s developed land, 71% of its residents, and 82% of its businesses are located within the tsunami hazard zone and that page has a MAP showing development. The large, dark red splotch on the north shore of the Chehalis where all the highways meet is "downtown."

That plus shopping just east of the Wishkah River -- about a ten minute walk from downtown -- accounts for the lion's share of shopping in Aberdeen. A lot of residential neighborhoods are uphill from downtown which is part of why the percent of businesses at risk is higher than the percentage of developed land at risk and the percent of residents at risk is lower than that figure.

There are rail lines south of downtown, located between downtown development and the water's edge. Five years ago or so, the area between the rail lines and water's edge was defacto a large homeless encampment and it was cleared out at some point for safety reasons. Homeless people would set fires to keep warm or cook, the fire would spread and there are no roads into there so the fire department couldn't even get a truck into there.

So it is basically undeveloped land and probably not in good shape generally, having served for some time as a large homeless encampment. This is a problem because it means NOTHING stands between downtown Aberdeen and oncoming waves in the case of a tsunami.

What I have been thinking for some time is that the land south of the rail tracks should be planted with trees, shrubs and other vegetation with an eye towards providing a barrier between downtown and oncoming waves in the case of storm surge or in the case of a tsunami event.

Now if you look at the maps on the piece linked above about tsunami zones in Aberdeen, you will note that downtown is a small part of the low-lying land in the tsunami zone and if you know how tsunamis work, it should be obvious that a few trees between downtown and an oncoming tsunami will be WHOLLY INADEQUATE protection.

Tsunami waves are regional events many feet in height. A limited barrier to protect one section of development won't do very much.

BUT if that area was developed to also be a sea otter sanctuary, sea otters foster the health of kelp forests and kelp forests mitigate storm surge and tsunamis. So there is potentially your REGIONAL protection and THEN a stand of trees and shrubs as a local barrier between downtown and the water WILL make a difference because the waves will already be less drama than they otherwise would have been.


I started r/urbanforestry in part because I was thinking of how mangrove forests are KNOWN to protect coastlines against storm surge and even tsunamis but Aberdeen is too far north for mangroves. Mangroves are a tropical species and I thought it would be easy to find another TREE to swap out, but, no. It has not proven that simple.

Links related to the above piece:

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