Flood — Juneau Borough, Alaska

2018-07-19 · near Douglas, Juneau Borough, Alaska

Event narrative

In the early morning hours of July 18th the Mendenhall Lake and River began to slowly rise as the glacier dammed lake in Suicide Basin about 2 miles from the terminus started to drain. Mendenhall Lake and River continue to rise for the next day and a half as the dammed lake emptied. The water levels reach minor flood stage of nine feet by the morning of July 19th and by the mid-afternoon around 5pm Mendenhall Lake crested at ten point ninety two feet. After the lake and river crested the water level receded very quickly and was below minor flood stage just before midnight on the 19th. There was minor to moderate flooding around Mendenhall Lake and the upper portions of the river above Back Loop Road. The Mendenhall campground was evacuated due flooding of up to three feet at the entrance and within the campground with some damage done to the road system. The West Glacier spur road and the area around Skaters Cabin was flooded with three feet water. View Drive was flooded with two feet of water and the road cut off. There was minor flood damage to some homes that border the river along the road. There was also more flooding along the dredge lakes trail area and and few other trails around the Mendenhall Glacier Visitor Center run by the USDA Forest Service.

Wider weather episode

Throughout spring and the first part of the summer Suicide Basin, a side valley that is dammed by the Mendenhall Glacier, filled with water from snow melt and rainfall. In the afternoon hours of July 17th visual reports showed signs of the basin beginning to drain as the glacier dam was starting to fail. The river gauge in the Mendenhall Lake started to show this inflow of water from the basin through the evening hours and by the morning of the 18th the event was well on its way. For the next 2 days the Mendenhall Lake and River rose five in a half feet and crested at 10.92ft in the afternoon of the 19th.

View location on OpenStreetMap → (58.4330, -134.5796)

Source: NOAA Storm Events Database, event_id 774303. Narrative written by the NWS forecast office that issued the report.