1986 Southcentral Flooding
Overview
October 9-12 brought intense rain and heavy flooding to southcentral Alaska. Both the Seward area of the Kenai Peninsula and the lower Susitna River Valley were particularly impacted. Seward received 15 inches of rain in the 24-hours between October 10-11; the highest 24-hour record in the state. Multiple points along the Parks and Seward Highways became impassable, due to flooding and washouts, temporarily halting traffic between communities. The Alaska Railroad shut down after two bridges washed out. Communities experienced utility and telephone disruption as well as major river and stream bank erosion. In Willow, Talkeetna, and Skwenta, 116 homes were damaged or destroyed. In Seward and on the Kenai, 166 homes were damaged or destroyed.
Weather woes
The atmospheric river system that brought heavy rainfall to southcentral originated as western Pacific Typhoon Carmen. Normally, weather patterns of this nature last for 12-16 hours. During this event, the moist air lasted 36 hours. In addition, the orographic effect, which leads to heavy precipitation on the windward side of mountains, influenced high rainfall rates in southcentral.
Disaster declared
Oct. 13: Governor Sheffield declared state disaster emergencies for Cordova, Seward, Talkeetna, Willow
Oct. 27: President Reagan signed federal disaster declaration
Public assistance and individual assistance granted for the Kenai and Matanuska-Susitna Boroughs, disaster totals estimated at $20 million (in 1986 dollars)
Rainfall totals Oct 9-11*
| Location | Rainfall (in) |
|---|---|
| Seward | 17.97 |
| Cordova | 12.57 |
| Whittier | 8.24 |
| Talkeetna | 8.11 |
| Kenai | 7.49 |
| Willow | 6.40 |
| Homer | 4.28 |
| Houston | 3.40 |
*U.S. Geological Survey Open File Report 87-391
Community specific impacts
The storm influenced infrastructure and communities at many levels, from individual residential subdivisions to state roads.
Seward: The community was particularly hard hit. The steep mountain slopes make the area prone to debris flows in rain events. Debris blocked rivers created dams, which then broke in “surge-release” flooding causing heavy damage. The sewage treatment plant was inundated with floodwaters.
Talkeetna: Widespread flooding caused severe bank erosion.
Alaska Railroad: Damage occurred primarily to the railroad tracks; 69 sites had documented damage.
Parks Highway and Seward Highway: Washouts along the road caused closures that temporarily cut off communities.
Ecosystem health
River and stream channels shifted and eroded influencing many aquatic species. Young juvenile fish became trapped in vegetation along bank areas when water receded. Pools used by migrating salmon were washed out. Many incubating eggs were lost due to dewatering in some areas as well as burial due to heavy sediment deposition in others.