Idaho earthquake caused popular beach, fishing spot to collapse

Weeks after a magnitude-6.5 earthquake shook Idaho, officials discovered a casualty of the quake, which was the state’s second-most powerful on record.

On Saturday, the Sawtooth National Forest reported in a news release that the earthquake caused the Stanley Lake Inlet Beach to collapse.

The damage wasn’t immediately visible following the earthquake due to snowpack and ice in the area.

“Initial reports noted that this former boat launch, beach, and popular fishing area was flooded with deep water and had seemingly disappeared,” the news release said.

The Sawtooth National Recreation Area constructed a new boat launch away from the inlet beach in 2019, and a campground near the inlet was moved to the east side of the lake at that time.

Still, it remained a popular spot for fishing and swimming.

“The loss of the inlet beach for fishing and recreation is unfortunate because that area was so popular with visitors at the lake. Fortunately, the new boat ramp and campground construction were completed before this event, ensuring access for boaters and campers going forward,” said Brian Anderson, deputy area ranger for the Sawtooth National Recreation Area, in the news release.

How does a beach just disappear?

Idaho Geological Survey experts looked at satellite images and compared before and after photos of the area to try to find an explanation.

“The most probable cause for the ‘disappearing’ of the inlet delta is a combination of liquefaction and compaction of saturated sediments and some possible sliding and lateral spreading on the delta toward the deeper part of the lake as a result of the March 31 earthquake or the associated aftershocks,” said Claudio Berti, state geologist and director of the Idaho Geological Survey.

Berti and other Idaho Geological Survey researchers will continue to investigate the site to try to better understand the March earthquake.