Addressing landslide safety concerns in Denali National Park
Learn how the National Park Service deployed a Trimble® automated monitoring system to track acceleration at the Pretty Rocks Landslide and make critical safety and maintenance decisions.
Key achievements
Solutions leveraged
Summary
The Trimble monitoring team implemented a system that met our needs for making safety and maintenance decisions for the Pretty Rocks Landslide project. Before implementing the automated monitoring system, we had a poor understanding of what meteorological conditions were the primary drivers of increasing displacement.
— Denny Capps
Park geologist, Denali National Park and Preserve
Background
Addressing accelerating landslide risks
Alaska’s Denali National Park and Preserve comprises six million acres of celebrated wildlife, outdoor adventures and natural beauty, including the Pretty Rocks Landslide. While active for at least 60 years, the landslide evolved from a minor maintenance nuisance into a major safety issue causing road restrictions.
Prior to 2014, park staff noticed small, easily repairable cracks in the road surface. Each year following, staff observed substantial increases in movement. A monitoring program initiated in 2016 tracked movement that escalated from 6–12 inches per year to up to 0.65 inches per hour by 2021. Standard maintenance activities were no longer safe or effective, forcing major road closures while park leadership determined long-term solutions. Crucial to the effort was evaluating safety and understanding the underlying causes of movement beyond previously observed rain and temperature correlations.
Solution
Deploying an automated monitoring solution
To overcome the limitations of manual RTK GNSS campaigns—which provided accurate points but lower temporal resolution—the National Park Service partnered with Trimble to implement an automated monitoring total station (AMTS) system. The system allowed continuous measurement from a safe distance across steep topography and loose volcanic rock.
The installed monitoring setup featured:
Trimble S5 AMTS: Accurately measured distances and angles at hourly intervals, 24 hours per day, across approximately 35 small prisms.
Trimble Settop M1: Served as field computer, device server, router, cellular modem and remote switch to power the total station and stream data.
Trimble 4D Control™ (T4D) software: Managed data, generated visual graphs, and provided automated movement and weather threshold alerts to park staff.
Weather station and time-lapse camera: Collected local temperature, wind and rainfall metrics correlated to movement while providing visual confirmation.
Solar power and satellite internet: Powered the remote installation and transmitted near-real-time data directly to park headquarters.
Results
Informing safety and infrastructure decisions
Through drilling, additional investigations and continuous AMTS data, experts determined that Pretty Rocks is a rock glacier accelerating due to warming ground temperatures and heavier precipitation.
Near-real-time data provided by the Trimble system delivered essential visibility into displacement trends. This intelligence helped park staff make informed safety decisions, including temporary road restrictions in 2019 and 2021, an early seasonal closure in 2021, and a full road closure in 2022. The collaboration delivered a robust monitoring campaign tailored to extreme environments.
