September 1995 was a very wet month in south central Alaska. Included in a series of cyclones, or low pressure areas, was a single cyclone that produced in excess of 20 inches of rainfall in several days in some locations. The rain caused flooding on many streams in south central Alaska that caused an estimated $10 million in damage to private homes and public facilities.
During the latter half of September 1995, the precipitation-rich meteorological regime had its roots in a persistent long wave pattern. A long wave trough in the north Pacific Ocean and a blocking long wave high pressure system in eastern Alaska and western Canada provided a continuous flow of warm, moisture laden air over south central Alaska. The heaviest rainfall came with the shorter wave cyclones moving north in the long wave flow, bringing a new surge of rain into south central Alaska every couple of days. The warm air associated with one of the cyclones set record high temperatures in many areas of the state.
The series of cyclones prior to September 19 generated saturated soil conditions and greater than normal glacial melt in south central Alaska. Heavy rainfall began along the southern coastline of the Kenai Peninsula on the afternoon of September 19 and spread inland overnight. Strong southeast wind, aloft during the storm, forced against southeast-facing mountain slopes of the Kenai, Chugach, and Alaska mountain ranges generated the greatest rainfall intensities. This rain caused the flooding.
The strong southeast wind also led to the typical downslope conditions west of the Chugach and Kenai mountain ranges that resulted in very little rainfall in these areas. Thus, highly variable rainfall amounts were reported.
Steep mountain terrain caused rapid runoff that carried heavy sediment loads onto flatter terrain. There, the current slowed and sediments deposited in and adjacent to the channels. The sediment deposition decreased the capacity of the channels, thereby increasing the degree of flooding. Most streams in south central Alaska crested on the 20th, 21st, or 22nd of September. The lower Kenai River on the Kenai Peninsula did not crest until September 24 and remained above flood stage for over 10 days.
Impact of the flooding includes damage to cabins, permanent homes, sewage treatment facilities, roads, trails, bridges, power transmission lines, airports, and railroad facilities. Fast currents caused significant bank erosion, channel shifting, and damage to dikes and levees.