Flood in Susitna Valley, Alaska

On August 31st, a resident of Petersville reported that the road along Cache Creek had been totally washed out in several places due to flooding along the creek itself, and the washouts had cut off residents from the main road network for several days. The resident also mentioned debris including large logs had washed into the road crossings and that the flood waters had overturned a few unoccupied vehicles. The creek that caused the flood damage was not gauged, so timing of the flood damage was estimated by comparing to timing of the highest water levels observed on the nearby Moose Creek during the same timeframe at the end of August.

An atmospheric river moved up from the North Pacific into Southcentral Alaska and produced widespread moderate rainfall between August 27th and August 29th. Strong southerly flow during the rainfall event caused south-facing slopes of the mountains across Southcentral to get the highest rainfall totals due to enhancement from upslope flow, including the north end of the Susitna Valley, where 2.5 to locally 6 inches of rainfall was recorded between 8/27 and 8/29. The runoff from the heavy rainfall pushed multiple waterways across the Susitna Valley into moderate flood stage from around 8/29 to 8/31, including sections of the Talkeetna River, Yentna River and Moose Creek.