Flood — Juneau Borough, Alaska

2022-10-27 · near Douglas, Juneau Borough, Alaska

Event narrative

The USGS Mendenhall Lake gauge started to rise from moderate rainfall through the afternoon of October 25th. The lake continue to rise from heavy rain of 1 to 2 inches with more in the mountains. Mendenhall Lake water level rate of rise changed and it started to rise at a steeper and more constant rate. This is an indicator that a glacier lake outburst flooding event happening from Suicide Basin. Another indicator was old images from the basin which showed significant amount of water in the basin. Mendenhall Lake continue to rise for the next 2 days as water continue to drain from Suicide Basin and the lake crested in the afternoon hours of October 27th 10.33 feet above moderate flood stage of 10.0 feet. Skaters Cabin road was flooded along with areas within the USFS Mendenhall Lake campground. The camp ground was closed for the season but there were some roads flooded with possible erosion damage.

Wider weather episode

A late season glacier lake outburst flooding event took place along the Mendenhall Lake and River. Water from Suicide Basin which is dammed by the Mendenhall Glacier released starting October 25th with the Mendenhall Lake cresting above moderate flooding by October 27th. There was flooding to the Mendenhall Lake campground but it was closed for the season. There was also heavy rain from a strong weather front that masked the event at first and might have triggered the event. Rain amounts ranged from 2 to 3 inches.

This was the latest impactful outburst flooding event on record with most event happening in the summer months. Also the amount of water in Suicide Basin was the most on record for late October.

View location on OpenStreetMap → (58.4140, -134.6005)

Source: NOAA Storm Events Database, event_id 1058965. Narrative written by the NWS forecast office that issued the report.