Geog312- Tutorial 6 Questions
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Simon Fraser University, Fraser International College *
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Course
312
Subject
Geography
Date
Dec 6, 2023
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docx
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2
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1.What were the causes and trigger of the 2014 Oso slide?
There were a few causes that ultimately contributed to the 2014 Oso slide,
including the weakened soil consistency of the slope due to previous
landslides, the erosion of the toe of the slope due to the rushing river
beneath it, and the intense rainfall that occurred just before the landslide. As
stated by David Montgomery in the short video, the soil and material that the
slope was made of is weak and it was only a matter of time until it slipped.
The river beneath it was also eating away at the toe of the slope, further
contributing to the deterioration of the slope’s strength and resistance.
Although these factors all contribute to the cause of the landslide, scientists
have determined that the intense rainfall was likely the trigger as water
stored within sediments decreases the friction between sediment particles,
increasing risk of a slip. Although not an unusual winter in terms of weather
and precipitation, the repetitive rainfall, erosion of the slope toe, and weak
soil formation finally caused the slope to have a large failure.
2.Risk is determined by both the probability of a hazard and the vulnerability
to that hazard when it occurs. In what ways did humans affect the probability
of the Oso landslide hazard? In what ways did human activity change
vulnerability to the slide?
Humans affected the probability of the Oso landslide hazard in a number of
ways. First, the presence of human activity in the region, including immense
clear-cut logging, road construction, as well as home and community
building, caused soil and debris to become more unstable. Particularly with
logging, open areas allow water and debris to flow much more freely,
especially in times of intense precipitation, and trees are no longer available
to block debris contents flowing down slope. Furthermore, the high levels of
precipitation in the area are partly caused by human-induced climate
change, which ultimately increases the amount of rainfall in the area. The
increased population means industrializing the area so that more people can
live, which further contributes to the destabilization of the slope.
Human acitivity also changed the vulnerability to the slide as more people
populated the area over the years. By 2014, there were 41,037 individuals
living in Oso, which was close a 40% increase compared to the 24,435
individuals in 1990. By increasing the number of people living in the area,
more people are at landslide risk, which increases overall vulnerability.
Furthermore, development continued in the runout zone of the landslide from
the 1980’s onward, which was quite shocking given the slope history.
Continuing these actions in a known hazard zone shows how humans
continued to increasing their vulnerability to landslides in Oso as years went
on.
3.In what ways do you think the Oso landslide may have been preventable or
risk reduced? Are these methods practical for the mitigation of future slope
failures in the Stillaguamish River valley near Oso?
After reading, there are some ways in which the Oso landslide may have
been risk reduced or preventable. The area of the slope could have been
monitored more closely by the researchers and scientists for signs of
instability. Particularly in winter months when there is intense rainfall in Oso,
monitoring the groundwater levels, observing for any changes in the slope
itself, or measuring the nearby streams or river levels could have been
beneficial in determining an increase risk for landslides at the time.
Furthermore, increasing slope drainage or runoff areas for intense rainfall
seasons could be implemented to help with erosion issues of the hillside and
removal of excess water. This would help reduce the risk of potential debris
flow from recurring landslides. I think that these methods are practical and
can be implemented in Oso quickly and are relatively cost-effective when
comparing it to the damage that can be caused if unprepared.
4.Would the costs of buying out the property owners in the year 2000 and
forcing them to leave, outweigh the costs of the landslide itself? Explain.
What other problems might exist with this strategy of mitigation?
I believe that the costs of buying out the property owners in the year 2000
and forcing them to leave would not outweigh the costs of the landslide
itself. This is because the damage and destruction caused by the landslide,
including loss of life and damage to homes and other property and
infrastructure, is not worth the risk of staying in the area. The 43 people who
lost their lives in the 2014 Oso slide would agree. The damage caused by the
landslide would also be substantially more than the cost of relocating the
individuals, especially in an area where landslides are known to be recurring.
Overall, it would make sense to buy out the property and remove those
individuals from any future harm or risk.
However, this may strike a problem amongst the community as they may not
want to leave. Relocation may be met with resistance. Additionally, people
may not be able to afford to live elsewhere, leaving a big issue regarding
displacement. If a population is being forced to leave without any means to
find a new place to live, the mitigation strategy may be met with some
serious backlash.
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