19: Landslide Hazards Flashcards
What are some types of landslides and some ways landslides can cause big social impacts?
debris flow:
- is a very deadly landslide that can wipe out cities and has killed thousands of people before (Venezuela, Peru, etc.). Can be started through torrential rainfall.
rockfalls:
- massive rocks can fall and crush housing, block roads, etc.
Slow Moving Landslides:
- These happen from months to years. They can heavily damage roads, infrastructure, housing,
What is the landslide velocity class?
a rating system from 1-7 with
1 being 16mm/year,
4 being 1.8m/hour, and
7 being 5m/sec.
1 is seen as extremely slow, imperceptible without instruments
4 is seen as moderate with some temporary and insensitive structures temporarily maintained
7 is extremely rapid, with catastrophe of major violence
What is landslide risk?
Risk is a combination of the likelihood of a landslide and its consequences
How can we learn from the past when it comes to landslides?
Ex/
Alberta has turtle mountain where first nations people know it as the mountain that walks
Killed 70 people in 1903. Government of Alberta has since implemented strategies like monitoring,
hazard zoning,
emergency response protocols
Identified 14 new areas of potential instability.
What’s the difference between debris flow and mudflows?
debris flow:
- generally includes boulders, sand, trees, etc.
- much higher consequences
- way faster and happens after extreme/intensive rainfall
Mud flow:
- usually just clay, finer particles, etc.
- lower consequences and impact
- much slower and happens after prolonged rainfall
What is the definition of a landslide and what is the process of one?
Landslide:
- A mass movement of material such as rock, earth, debris, or mud down a slope
Process:
cause (geological, mechanical, hydrological, geomorphological, biological, human,…)
trigger (initiates failure, ex/ gravity)
effect (rock slide, topple, mud flow, rock fall, debris flow,…)
What are the 3 types of material relative to types of landslides?
Types of material:
rocks (Solid rock that’s transported down a slope in a rockslide)
Debris (A material made up of coarser fragments, such as rocks, stones, and boulders, trees, etc.)
Earth (A material made up of sand-sized or finer particle)
What are the 4 types of movement in landslides?
Falls:
- Material collapses from a steep slope or cliff and falls, bounces, or rolls through the air. Little to no shear/sliding taking place
Topples:
- A mass of material rotates forward out of a slope around a pivot point below its center of gravity. Similar to falls but with rotation.
Slides:
- they involve large volumes of rock or soil moving as an initially coherent mass on a sliding surface
Flows:
- Occurs when there is a large volume of water present in a mixture of soil and debris. Rather than moving downslope as a coherent mass, the material flows downhill as a chaotic mixture.
Where do rock falls occur?
Rock falls occur on steep slopes with loose rock that periodically detaches from a surface on which little or no shear/sliding takes place
What are the 2 types of slides?
Rotational Slides:
- soil or weak rock collapse along a curved rupture surface that forms due to the shear forces in the slope exceeding the shear strength of the rock/soil
translation slides:
- where blocks of strong rock move along a weak fracture in the rock (e.g. jointing, bedding planes) or weak soil moves on top of a hard bedrock interface. Can be 1 or 2-plane
How does geology influence what kind of movement we have in a landslide?
Geological planes of weakness play a huge role:
Toppling and rockfall:
- tends to happen when the planes of weakness aren’t aligned or perpendicular to the direction of sliding / falling
Sliding and flowing:
- tends to happen when the planes of weakness are aligned with the direction of flow
