Stanley Lake’s inlet beach has collapsed as a result of the March 31 earthquake, the Sawtooth National Forest reported over the weekend.
Forest Service officials were initially alerted to the beach’s collapse after several recreationalists reported deep floodwater at the inlet delta where Stanley Lake Creek empties into the lake. A subsequent Idaho Geological Survey review using satellite imagery attributed the collapse to the 6.5 magnitude earthquake in March, Sawtooth National Recreation Area spokeswoman Julie Thomas said in a statement.
Once a popular fishing and boat-launch area, the inlet beach most likely collapsed due to “liquefication and compaction of saturated sediment and some possible sliding and lateral spreading,” according to State Geologist Claudio Berti.
Fortunately, campground infrastructure near the inlet had been relocated to the east side of the lake in a recent project, Deputy Area Ranger Brian Anderson said. A new boat ramp was also completed in 2019.
“The loss of the inlet beach for fishing and recreation is unfortunate because that area was so popular with visitors at the lake,” he said.
A team of Idaho Geological Survey geologists led by Berti plan on visiting the site and completing their assessment in the coming weeks, Thomas said.