Puget Sound Landslides
In the Puget Sound landslides are fairly common, mostly due to a very wet climate and ever changing environment.
The definition of a landslide is: A gravity driven down slope movement of a mass composed of soil, rock, and vegetation. A landslide generally happens when the material in the down slope is heavier then the supporting soil. There are many contributing factors that cause landslides, steepness of slope, composition of soil and rock, groundwater condition, recent precipitation patterns, slope aspects vegetation on slopes, and anthropomorphic activities (land clearing).
There are generally four types of landslides; Shallow bluff, deep seated Debris flows, and submarine landslides. In a shallow bluff landslide they generally occur on the steep Puget Sound marine bluff. Generally they …show more content…
are caused by the clearing of vegetation to improve views but in turn can lead to soil instability and slope erosion.
Deep seated landslides can be as large as thousands of acres but can also be relatively small and confines to a smaller area, and usually occur when the slope is lower than 15% Debris flows are considered to the most hazardous to life. Debris flows are generally fast moving water saturated masses of soil, rock, debris and tree trunks. These landslides can be triggered by intense rainfall and are mostly found in the mountains of Peirce County.
Submarine landslides primarily occur underwater along the delta of the Puyallup River. These slides are triggered by rapid sedimentation caused by and unstable slope, the loss of soil strength due to static liquefaction, loss of slope support because of bottom current erosion of material at the base of the delta slope. These slides are also triggered by the additional loading at the top of the delta slope with artificial fill, this caused increased weight on the slope. Liquefaction caused by earthquakes is also a huge factor in submarine earthquakes. Submarine landslides in the Pacific Northwest generally occur on the deltas of major rivers and streams. Submarine landslides can trigger tsunamis.
There have been many documented occurrences of landslides in the Pacific Northwest, specifically Peirce County. In February 2001 a hillside above Salmon Beach went downhill following the earthquake on February 28th 2001. The damage following this earthquake and landslide includes numerous houses as well as knocking out electricity.
In 1996a landslide caused two trains and two cars to fall into the Puget Sound resulting a hazardous spill.
In 1991 in the lower Nisqually river near Fort Lewis a landslide occurred and ended up blocking the river with debris. This debris temporarily caused the river to back up, change course and flow through a forest.
In 1984 several train cars were derailed after the ground gave way south of DuPont due to a landslide. Only minor injuries were reported, not including a nonfatal heart attack following the disaster.
In 1949 only a few days after the earthquake in Olympia the ground was so saturated that it broke just north of Salmon Beach, below Fort Nisqually thus sliding into the Tacoma narrows.
Those people who demand to a have a house with a few is largely vulnerable to landslides due to the ever changing climate as well and the ever changing soil structure.
The rapid development of coastal areas and areas prone to landslides has increased the areas vulnerability to landslides.
Landslides are known to typically damage roads, railroads, sewer lines, water lines and homes, but that list should also include public buildings. Landslides are known for being detrimental to utilities because the force behind them can take down power lines like they are made of twigs. Even “small” landslides can be expensive. Clean up costs include but are not limited to, the clearing of minor to major debris, renewing and/or replacing the supports for bridges and roads and railroad embankments. Damages from these disasters include but are not limited to minor vehicle damages, minor to major building damage, personal injury up to and including death, and as mentioned before, loss of important
utilities. Unfortunately as of today there are currently links set up on Peirce County’s emergency preparedness website for every natural disaster, except landslides. But that is likely to change as the climate and environment changes. In the pacific northwest you become accustomed to severely wet weather and you are taught at an early age what should be done. With the rainy season being severe this year, they will likely have to add a like to emergency preparedness for landslides in Peirce County.
In 1949 only a few days after the earthquake in Olympia the ground was so saturated that it broke just north of Salmon Beach, below Fort Nisqually thus sliding into the Tacoma narrows.
Resources
http://www.co.pierce.wa.us/xml/abtus/ourorg/dem/EMDiv/MP/PC%20Landslide.pdf
The definition of a landslide is: A gravity driven down slope movement of a mass composed of soil, rock, and vegetation. A landslide generally happens when the material in the down slope is heavier then the supporting soil. There are many contributing factors that cause landslides, steepness of slope, composition of soil and rock, groundwater condition, recent precipitation patterns, slope aspects vegetation on slopes, and anthropomorphic activities (land clearing).
There are generally four types of landslides; Shallow bluff, deep seated Debris flows, and submarine landslides. In a shallow bluff landslide they generally occur on the steep Puget Sound marine bluff. Generally they …show more content…
are caused by the clearing of vegetation to improve views but in turn can lead to soil instability and slope erosion.
Deep seated landslides can be as large as thousands of acres but can also be relatively small and confines to a smaller area, and usually occur when the slope is lower than 15% Debris flows are considered to the most hazardous to life. Debris flows are generally fast moving water saturated masses of soil, rock, debris and tree trunks. These landslides can be triggered by intense rainfall and are mostly found in the mountains of Peirce County.
Submarine landslides primarily occur underwater along the delta of the Puyallup River. These slides are triggered by rapid sedimentation caused by and unstable slope, the loss of soil strength due to static liquefaction, loss of slope support because of bottom current erosion of material at the base of the delta slope. These slides are also triggered by the additional loading at the top of the delta slope with artificial fill, this caused increased weight on the slope. Liquefaction caused by earthquakes is also a huge factor in submarine earthquakes. Submarine landslides in the Pacific Northwest generally occur on the deltas of major rivers and streams. Submarine landslides can trigger tsunamis.
There have been many documented occurrences of landslides in the Pacific Northwest, specifically Peirce County. In February 2001 a hillside above Salmon Beach went downhill following the earthquake on February 28th 2001. The damage following this earthquake and landslide includes numerous houses as well as knocking out electricity.
In 1996a landslide caused two trains and two cars to fall into the Puget Sound resulting a hazardous spill.
In 1991 in the lower Nisqually river near Fort Lewis a landslide occurred and ended up blocking the river with debris. This debris temporarily caused the river to back up, change course and flow through a forest.
In 1984 several train cars were derailed after the ground gave way south of DuPont due to a landslide. Only minor injuries were reported, not including a nonfatal heart attack following the disaster.
In 1949 only a few days after the earthquake in Olympia the ground was so saturated that it broke just north of Salmon Beach, below Fort Nisqually thus sliding into the Tacoma narrows.
Those people who demand to a have a house with a few is largely vulnerable to landslides due to the ever changing climate as well and the ever changing soil structure.
The rapid development of coastal areas and areas prone to landslides has increased the areas vulnerability to landslides.
Landslides are known to typically damage roads, railroads, sewer lines, water lines and homes, but that list should also include public buildings. Landslides are known for being detrimental to utilities because the force behind them can take down power lines like they are made of twigs. Even “small” landslides can be expensive. Clean up costs include but are not limited to, the clearing of minor to major debris, renewing and/or replacing the supports for bridges and roads and railroad embankments. Damages from these disasters include but are not limited to minor vehicle damages, minor to major building damage, personal injury up to and including death, and as mentioned before, loss of important
utilities. Unfortunately as of today there are currently links set up on Peirce County’s emergency preparedness website for every natural disaster, except landslides. But that is likely to change as the climate and environment changes. In the pacific northwest you become accustomed to severely wet weather and you are taught at an early age what should be done. With the rainy season being severe this year, they will likely have to add a like to emergency preparedness for landslides in Peirce County.
In 1949 only a few days after the earthquake in Olympia the ground was so saturated that it broke just north of Salmon Beach, below Fort Nisqually thus sliding into the Tacoma narrows.
Resources
http://www.co.pierce.wa.us/xml/abtus/ourorg/dem/EMDiv/MP/PC%20Landslide.pdf