Flood — Matanuska Valley, Alaska

2019-12-21 to 2019-12-31 · near Wasilla, Matanuska Valley, Alaska

Event narrative

Late on December 21, an ice jam on Willow Creek near the Deneki Bridge (61.77N, -149.956W) caused water to back up and flow through numerous residences. Deneki Road and access to the Deneki Bridge was closed for multiple weeks between December 21 and January 8, 2020. At least thirteen households evacuated on December 21-22 due to flooding or anticipation of road closures. Six homes were damaged by flood water; there was a report of knee-deep water in one home, as well as deep flowing water around the house, 'It formed a river in my yard' . Numerous, (>10), cars were flooded and frozen in place. Also some cars had to be abandoned after owners tried to drive across the flood waters and became stuck.

Examining the hydrographs, the most likely cause of the ice jam flooding was an ice dam which collapsed in the canyon, causing a mini breakup which was constricted and stopped at the Deneki Bridge.

The MatSu Borough worked with private contractors to divert the water and allow access to the Deneki Bridge and the subdivision of homes and farms to which it provides the single point of access. Using heavy equipment, they mechanically removed the ice jam, which allowed the water flow to return to the channel, preventing it from flowing through the neighborhoods overland.

Wider weather episode

A stretch of cold weather resulted in a freeze up ice jam on Willow Creek in the MatSu Borough.

View location on OpenStreetMap → (61.7772, -149.9324)

Source: NOAA Storm Events Database, event_id 867248. Narrative written by the NWS forecast office that issued the report.