FAQs
- radar-based slope scanning;
- visual inspections;
- groundwater level monitors;
- targeted survey monitoring of critical slope areas; and
- drone surveys.
- visual inspections;
- targeted survey monitoring of critical slope areas; and
- drone surveys.
- installing a sheet pile wall along the highest risk portion of Robert Service Way in the spring of 2022 to create a barrier between the road and the escarpment that will slow down and contain landslide debris;
- manually removing a large portion of material from the escarpment that posed a landslide risk and created a berm along Robert Service Way with the discarded material in the spring of 2023; and
- paving the shoulder of Robert Service Way to shift traffic away from the base of the escarpment.
- Tetra Tech Canada Inc: escarpment monitoring, geohazard zone updates, long-term options analysis, and various other escarpment tasks requiring local expertise.
- BGC Engineering: third-party review and recommendations.
- SLR Consulting: groundwater monitoring at the airport and hydrogeological input.
- In emergencies (imminent slope failure or public safety risk): contact the Whitehorse Fire Department using 9-1-1.
- After hours (non-emergency): contact the City reporting line at 867-667-2111
- For questions and general slope observations: contact City of Whitehorse staff using the following ways:
- Engage Whitehorse using the “Ask a Question” tool
- Report a Problem
FAQs
What is the 2024 monitoring plan for Robert Service Way?
The City of Whitehorse is working with Tetra Tech Canada to monitor the escarpment along Robert Service Way during the 2024 freshet season. Monitoring began mid-March and will continue until experts determine that freshet is over, likely at the end of June.
Multiple methods for regularly monitoring the slope are being used, including:
What is the 2024 monitoring plan for the rest of the escarpment?
The rest of the escarpment will be regularly monitored with the following methods:
Will Robert Service Way be closed in 2024?
Robert Service Way may be closed this year if geotechnical engineers recommend closure if the condition of the slope becomes unsafe. Landslides along the escarpment are now a regular occurrence and spring closures should be expected annually until a permanent solution can be implemented.
Closing or reducing traffic through Robert Service Way is a decision not taken lightly and is done to protect the public. The City of Whitehorse understands the inconvenience this may cause, however, sometimes closing Robert Service Way is the best method to protect the public when slope movements suggest imminent failure.
What is the long-term solution for the escarpment along Robert Service Way?
Pending funding approval, the City plans to realign the north end of Robert Service Way by moving it away from the base of the escarpment and re-grading the slope in 2026. In partnership with the Government of Yukon, the City applied for the federal government's Disaster Mitigation and Adaptation Fund to support this long-term plan to lessen the impacts of potential future landslides.
What has the City done so far to mitigate landslides off the escarpment?
The City has implemented several initiatives to mitigate landslides off the escarpment, including:
If movement is detected along the escarpment, the City has 400 concrete lock blocks in storage to build a retaining wall at the problem area. This will reduce the impact of small slides along Robert Service Way.
What experts is the City working with to provide escarpment recommendations?
The City of Whitehorse has retained local geotechnical and hydrogeological consulting firms and a third-party engineering consultant specializing in geohazards to review work conducted by the local firms. The team of experts includes:
The Yukon Geological Survey has also engaged with the City of Whitehorse. It has provided its expertise and observations as required.
What causes landslides off the escarpment?
Many geologic factors can contribute to landslides, but the most likely cause is groundwater seepage. This is when an excess amount of water seeps through the escarpment, loosening its soil, sand, and silt, causing slides.
2021 and 2022 saw some of the highest snowfall levels on record in Whitehorse. When that snow melted, it created an excess of groundwater. This is likely one of the main causes of the landslides that have taken place in the last few years.
The City is monitoring groundwater in the escarpment throughout freshet season with data loggers and remote telemetry in order to help predict slides.
Can the City predict future landslides before they occur?
Predicting the size and timing of landslides is difficult.
For example, an engineering consulting firm identified the Jeckell Street area as having the potential for a large landslide to occur in 2021, which prompted the closure of Cliffside Park and area. However, that slope did not fail until 2022. On the other hand, Robert Service Way did not show any signs of developing instability in 2021, and it failed in 2022.
I live near the escarpment, should I be concerned, and who can I contact to discuss in more detail?
The City expropriated properties in the high-hazard zone and some in the moderate-hazard zone after the 2002 geohazard study to mitigate risks. If you are concerned about the escarpment slope, you can contact the City of Whitehorse Engineering Department at: 867-667-6401.
Who do I contact if I see something concerning around the escarpment?
Please reach out to us if you observe concerning activity around the escarpment. You can reach us:
How will the City communicate with the public about what’s happening with the escarpment?
The City uses a variety of tools to keep residents informed about the escarpment, such as:
Glossary
Debris Flow: like a debris slide, but sediment is water-laden, fast-moving, and forms thick muddy deposits. Typically, they are channelled in gullies where their speed and energy increase. These flows can readily move boulders and uproot trees.
Debris Slide: a relatively dry landslide of unconsolidated soil or rock that has slid or rolled rapidly down a steep slope to form an irregular hummocky deposit. These movements are somewhat slower than others.
Deep-Seated Failures: failures that initiate back from the crest of the slope with a failure plane that extends beyond the toe. This slope process has not been observed along the Whitehorse escarpment to date.
Earthflow: a viscous flow of fine-grained materials downslope saturated with water and moving under the force of gravity. This is an intermediate flow between downhill creep and mudflow.
Escarpment: a long, steep slope, especially at the edge of a plateau or separating land areas at different heights.
Extensometer: a device used to measure the displacement between two points using a string, weight, and ruler affixed to two posts anchored in the ground. Typically, extensometers are placed in a manner where one pole is anchored in the stationary soil mass and the other in the mass that is moving. These are usually installed perpendicular to tension cracks on a slope.
Failure Plane/Surface: a plane drawn through the soil that becomes the sliding surface for a landslide. The failure plane may be relatively uniform or it may undulate depending on soil conditions.
Freshet: a term used to describe a period of snow melt, an annual high water event on rivers from snow melt, and river ice melting. For the Whitehorse escarpment, freshet season is considered from mid-April to the end of June each year. During freshet, increased surface water and seepage flows are observed.
Frost Fracturing: the result of frost penetration into fine-grained soils that causes expansion and ice lenses. When the ground thaws, these fractures remain and can increase in size the following winter. Frost fracturing contributes to shallow mass movements on the escarpment.
Ground Based Interferometric Radar: radar technology used for continuous slope scanning to help find and track developing instabilities.
Headscarp: the head is the upslope portion of a landslide, and the scarp is a steeply inclined failure surface with exposed soil and/or rock that marks the top of a landslide. Headscarps are found throughout the escarpment and are easily identified as “large bowls” above gullies or where near vertical faces of soil are exposed.
Ice Lenses: Massive ice, millimetres to centimetres thick, forms as fine-grained soil freezes with excess pore water. Due to many years of growth, ice lenses can grow to be metres thick in permafrost areas.
Liquefaction: a process that occurs in saturated soil where disturbance causes excess pore water pressure and changes the behaviour of the soil from a solid to a liquid. The April 30, 2022 landslide’s reach was primarily due to saturated silt and clay liquefaction.
Mass Movement (landslide): a catch-all term for the bulk movement of soil and rock debris downslope in response to the pull of gravity; debris slide, debris flow, earthflow, and mudflow are all examples of mass movements.
Mudflow: similar to an earthflow, but sediment has liquefied and moves quicker.
Pore Water: water trapped in the interstitial space between soil grains.
Rilling Erosion: shallow channels formed in soils from the flow of water down a slope.
Runout: a term used to describe the reach of a landslide once it reaches the toe of a slope. Runout is controlled by many factors; topography, soil composition, velocity, etc.
Seasonal Frost: the seasonal freezing of near-surface soils. The expected frost penetration depth in Whitehorse is 2.4 m in undisturbed areas. It can reach up to 5 m depth in disturbed areas.
Seepage: the flow of fluids through soil. Groundwater is the most common form of seepage, but it can be other fluids such as air, hydrocarbons, etc. Seepage occurs throughout the Whitehorse escarpment, most notably in Baxter’s and Puckett’s Gulch. Generally, the number of seepage points from the escarpment face increases moving south.
Shallow Failures: the typical slope processes of the escarpment where failures occur within the slope between the crest and toe.
Tension Crack: soil has little to no tensile (pull apart) strength. Tension cracks are formed when a mass of soil moves differentially from another. These cracks are an indication of ground movement and can be measured using instrumentation.