The National Weather Service has issued a flood alert until Monday morning to Mendenhall Lake and Mendenhall River following Suicide Basin began draining earlier this week.
Flood waters are predicted to peak sometime in the Saturday night, resulting in the possibility of a six-to-four foot rise in Mendenhall Lake. It could lead to flooding in the Mendenhall Lake campground and Skater’s Cabin Road, along with the possibility of tree falls and erosion in the Mendenhall River.
National Weather Service hydrologist Aaron Jacobs said glacial outburst flooding takes place slowly.
It’s a span style=”font-weight 400 ;”>”It’s not like a flash flood or like the wall in water” Jacobs said. “Usually it’ll take around two days, but it can be longer if some .”
A webcam in the basin captured a substantial decrease in the water level in the early morning of Friday. Measurements of Mendenhall Lake confirmed that water levels are increasing downstream.
Glacial outburst floods -also referred to as Jokulhlaups are a common summertime phenomenon since 2011. The thinned ice that resides in the mountains that are above the terminus of Mendenhall Glacier created an ice dam, which holds in the water in an area referred to as Suicide Basin.
The dam holds rainwater and meltwater within the basin, and it is filled up during summer and spring. This year, the dam filled to the top to levels that were not seen in 2021 and 2022.
However, Jacobs states that higher levels of water in the basin does not necessarily mean that there will be flooding waters downstream. The basin’s water flows through the Mendenhall Glacier through cracks in the ice, and may expand in a variety of ways that can affect the speed with which it drains from the basin.
“So the faster water moves from the Basin to the surface of Mendenhall Glacier and into the lake, the greater the peaks of flooding could become,” Jacobs said.
Jacobs said meteorologists will continue to monitor the water gauges downstream and update the information on flooding throughout the weekend.
