From remote weather stations to laser imaging to autonomous drones, the state and borough are working together to deploy cutting-edge monitoring technology at the 11-Mile landslide site.
LiDAR maps that were created before and after the slide will help geologists study potential landslide risks on the island.
LiDAR, which stands for Light Detection and Ranging, is a laser-based imaging method that creates detailed, three-dimensional maps of the Earth’s surface. LiDAR instruments consist of a laser, a scanner and a specialized GPS receiver to ensure the mapping stays on track, according to the National Ocean Service, and are usually operated from a plane or helicopter.
In mid-July 2023, the U.S. Forest Service and state Division of Geological and Geophysical Surveys conducted a LiDAR flyover to create an updated, snow-free model of Wrangell Island’s topography.
“They just released that data, coincidentally, the Tuesday morning after the slide occurred,” said Mitch McDonald, an engineering geologist with the state Department of Transportation.
Having a detailed LiDAR map of the island shortly before the slide is “the best case scenario” from a scientific standpoint, McDonald added. This way, state geologists can compare the pre-slide map of Wrangell to the mapping done immediately after Nov. 20.
With the help of these models, researchers can examine whether water was pooling in the same areas of the land before and after the slide, for example. “It helps us to determine a cause.”
LiDAR mapping isn’t the only technology that DOT may use to monitor the slide site moving forward.
The department plans to install a drone docking station near 11-Mile that would allow a remotely operated drone to take off from Juneau and land in Wrangell to take video of the area.
“The drone dock, that’s new technology,” said McDonald. “Alaska is out there on the leading edge of this drone technology, just because of the remote nature of our state, it becomes such a great tool for us.”
Using emergency funding, the DOT also plans to set up weather stations near the road and near the top of the slide to keep track of soil moisture, temperature, wind and rainfall in the area.
Wrangell already has a weather station at the airport. But thanks to Southeast Alaska’s microclimates — places with localized atmospheric conditions that can differ substantially from surrounding areas — the amount of rainfall near the slide site doesn’t line up with the rainfall that is measured at the airport station.
“We’re measuring higher rainfall amounts (at the slide site) just with some over-the-counter analog main gauges,” said McDonald. “We’re measuring more than what they’re reporting at the airports.”
High winds, heavy rain and water-saturated soil were all probable factors in triggering the Nov. 20 slide, so tracking these pieces of data can help borough and state officials determine when risk is high.
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