Landslides

Case Study 2 Week 3

https://www.nap.edu/read/1784/chapter/8

https://www.accuweather.com/en/weather-news/armero-colombia-tragedy-disaster-30-year-anniversary-lessons-learned-nevado-del-ruiz-volcano/53554025

https://www.unisdr.org/archive/46666

https://www.csmonitor.com/1985/1119/ocano.html

My favorite resource is also a case study of the Armero Tragedy. This resource is useful primarily because of the organized and obvious facts it presents. A lot of the information that I have learned in my various research so far on this tragedy parallels the details given in the case study. Not only that, but there is additional information given that I did not previously know. Ultimately, this resource presents useful and new facts in a “to the point” and efficient manner.

Case Study 2 Week 2

Something I learned from this week was that there actually was an evacuation issued for the surrounding towns of the Nevado del Ruiz volcano. Previously, I though the Colombian government was notified of the risk of eruption and mudslides, and they simply just brushed it under the rug. Actually, the government did contact Red Cross to notify an evacuation, but due to stormlike conditions mixed with the heavy ashfall from the eruptions, there was a power outage in that particular area. Regardless, the Red Cross could’ve sent units out there to spread the word once they realized their messages were not being received. This would’ve gave the residents at least three hours to get to higher ground before the series of lahars decimated Armero.

Flooding Hazards Game / Landslides Ideas

My second case study is focused on the Armero Tragedy – the deadliest lahar in recorded history. Seeing as the volcano mitigation game focuses primarily on the actual eruptive aspect of a volcano and not the landslide/lahar aspect, I decided it was best to play around with the flood game as well as come up with a few ideas for a landslide game.

The most useful thing about the flooding game was the little bits of information and advice they would periodically bestow on you as you progressed through the game. The more the game advised me, the more comfortable I was with making decisions regarding the safety of the town.

Something that got annoying to me was the time it took to preform upgrades on buildings. Realistically, if a town had to put up new buildings in preparation for a known destructive event, one would think that the proper “upgrades” would be included with the building originally. It would make the experience more worthwhile if there was an option that included the appropriate upgrades upon each time you built something, for more time could be focused on protecting and developing other areas.

In my eyes, a fun and engaging landslide mitigation game would follow nearly the exact format as the various mitigation games: as time went on, the towns risk of a landslide would increase ever so slightly. One would be assigned a budget and a number of people in need of protection and/or displacement due to their location in relation to an area likely to give way or act as a channel for a landslide. The budget would be used to build new homes for people to move out of landslide prone areas, as well as things like walls to catch sliding debris or chain-link meshes encasing slopes or anchors driven into rock faces. As one would progress through the game, they would be given hints that might help them in their future decision making upon their timing and strategy as far as when and where to conduct certain upgrades. Eventually, the landslide would ensue and the player would a receive a report card of sorts including information on casualty rate and number of homes destroyed.

Case Study 2 Week 1

On November 13, 1985 the Nevado del Ruiz volcano in Colombia erupted and triggered the deadliest lahar in recorded history. The presence of the volcano is due to the convergent margin formed by the Nazca plate subducting beneath the South American plate. Again, the eruption wasn’t the deadly factor, but the lahar that the eruption generated is responsible for burying 25,000 people. The most interesting thing that I have learned thus far is that the Colombian government was actually warned about an eruption here and chose not to evacuate. This evacuation without a doubt would have saved thousands of lives, so it is still a mystery to me why it wasn’t executed.

Oso Landslide

 

Geologists say a landslide has caused this slope near Oso to drop 4 feet since Tuesday. (Washington State Department of Natural Resources)Oso Land Slide

 

My favorite source was number three on the list below. I think that is fascinating that though a little more investigation it was learned that this area has been prone to landslides for thousands of years. The original theories were that over logging of the mesa above the homes was a root cause. But the lidar takes some of the burden of the blame off the logging and back on to county planners. This disaster was a good example of how better building review could help save lives.

Another great article was the first on my list below. You can see the amazing resilience of people and how positive they can be finding the good out of all the bad that happened. It is inspirational to me. However, it can also help us understand how people can rebuild in the same flood plane time and time again. People believe that it was a “freak” event isolated in time. They don’t see that it is a pattern from the geologically unstable soil and debris left by a glacier.

 

  • Oso Mudslide: Residents Remember Tragedy One Year Later https://www.nbcnews.com/storyline/deadly-mudslide/everyone-came-together-residents-remember-oso-mudslide-one-year-later-n327931

 

  • Oso landslide hit fast, hard and with no warning                 https://www.usatoday.com/story/news/nation/2014/03/28/oso-landslide-seismic-records-two-slides-no-warning/7019249/

 

  • New analysis shows Oso landslide was no fluke                  https://www.seattletimes.com/seattle-news/science/new-analysis-shows-oso-landslide- was-no- fluke/

 

  • State investigates landslide near Oso; some residents evacuate  https://www.seattletimes.com/seattle-news/environment/landslide-near-oso-is-slow-                                   moving-washington-state-investigates-as-residents-evacuate/

Image: Oso Mudslide

Oso Landslide

 

 

 

 

 

The Oso landslide was a massive landslide that killed at least 25 people on March 22nd, 2014. The slide destroyed over two dozen homes in Oso, Washington and it came without seismic warning.

I chose this slide because of the recent mudslide and debris flows here on the central coast of California. Although the cause of the sides is different. The sides in Santa Barbara California were the result of very heavy rain in a very short period of time over steep recently denuded soils from a wildfire. The Oso slide was due to long periods of continues rain beneath an over logged mesa. I also chose this event because it is a great normative example of how better planning and mitigations for a known hazard could have saved lives.

 

Oso Washington sits near a complicated system of plate boundaries and faults. This area is near where the Pacific plate if forcing a chunk of the crust is known as the Juan de Fuca plate under the North American plate creating a very seismically active area. The nearest plate boundary to Oso Washington is the convergent boundary where the Juan de Fuca plate subducts beneath the North American plate. However seismic activity is not the cause of the Oso landslide.

What caused the landslide was the result of glaciers that retreated more than 15,000 years ago, leaving behind an unstable mix of till, sand, clay and lake sediments. The valley floor is smooth and flattened by the alluvial flows that the river has helped to shape. The valley is bordered by the steep hillsides that are a transaction of the loose glacial sediments.

The main contributors to the event were the predisposition to soil failure and the steady rain for 45 days. The water saturated soil broke loose from the hillside and slid destroying a community of tract homes that were recently built. The slide spanned nearly a half mile in length and several hundred feet thick at the highest point of the debris. The initial slide lasted approx. 2.5 min and had several smaller slides as the face of the scarf continued to slough off.

What is fascinating is what was learned after the slide. The area was observed with LIDAR (the map at the top of the post)  and mapped several slides in the area over the last 5000 years. The research shows that a major slide like the Oso slide happens approximately every 140 years. The study also reveals that the landscape is much more fluid and is expected to continue to have slid all along the valley.