JOINT BASE ELMENDORF-RICHARDSON – As the days get longer and temperatures warmer in the state’s interior region near Fairbanks, the US Army Corps of Engineers – Alaska District uses snow data to predict snow conditions. potential flooding on the Chena River during spring break-up season.
The organization is partnering with the U.S. Department of Agriculture’s Natural Resources Conservation Service to measure winter snowfall levels and collect additional data from nine monitoring stations in the Chena River Basin. The agencies analyze this information to estimate the volume of runoff during the melting of the snowpack in the mountains. In turn, the USACE can anticipate potential flood events and the need to regulate flow by operating the Moose Creek Dam at the Chena River Lakes Flood Control Project at the North Pole.
The interagency team traveled by helicopter on March 30 and again on April 30 to assess the latest snow conditions at remote sites. Spread over approximately 1,500 square miles, the water contained in melting snow, known as the snow water equivalent, will eventually flow into the Chena River and flow through downtown Fairbanks.
Based on this data, officials predict strong spring runoff that will require USACE personnel to be ready to act if the river rises to significant levels.
“Snow records measured about double the normal SWE in the basin, which is the highest recorded since measurements began in 1980,” said Nathan Epps, hydraulics and hydrology section chief.
Last winter, the greater Fairbanks area experienced record snowfall and a freezing rain event which contributed to the unusually high amount of water seen in the snowpack at some of the telemetry stations.
“The freezing rain event in late December left a layer of ice in the snowpack, which was not found in the higher elevations of the upper Chena Basin,” said Rosie Duncan, an employee of the USACE which participated in the snow survey work. “If freezing rain has fallen into the basin, the [monitoring stations] would still record this and report it as part of the snow water equivalent.
In other words, a lot of snow has accumulated and its density is higher than what is typical for the interior, Duncan said. According to the National Weather Service’s “Spring Breakup Outlook”, the flood potential of the Chena and Tanana rivers is above average. However, the speed at which this snow melts will influence whether or not dams are necessary.
“Ideally, there will be a gradual increase in temperatures to just above freezing without additional precipitation or ice jams, resulting in a longer period in which snowmelt will add to the catchment,” a- she declared.
During normal operations, the Moose Creek Dam regulates the flow of the Chena River to no more than 12,000 cubic feet per second through downtown Fairbanks. The effects of flooding downstream along the river also depend on conditions in the Tanana and Little Chena rivers as well as local drainages. Low-lying areas near the Chena River may experience minor flooding, while elevated groundwater may occur for several thousand feet downstream of the dam.
Although the floodplain behind the dam remains dry for most of the year, USACE officials may retain water when river levels are high due to heavy snowmelt, ice jams or heavy rains. After the 1967 Fairbanks flood that caused approximately $80 million in damage, the Chena Project was built in the 1970s to protect the city, the North Pole, and Fort Wainwright from future disasters. Since then, the 7½ mile earth dam has operated 30 times to keep local communities safe and prevent approximately $418 million in flood damage.
“The Moose Creek Dam is a valuable asset to the Fairbanks North Star Borough,” said Mark DeRocchi, Manager of Engineering, Construction and Operations. “In 20 years, this has prevented potentially catastrophic flooding in the region.”
Meanwhile, construction will begin this spring to strengthen the structure. Dubbed a “mega project” and funded by the recently enacted Infrastructure Investment and Jobs Act, the Bauer Foundation Corp. of Florida was awarded a $75.5 million contract to establish an in-situ mixed concrete barrier wall at the base of the dam that spans 6,200 linear feet at depths of up to 65 feet.
The project stems from a 2017 modification study that recommended strengthening the dam to extend its life and improve the protection of the greater Fairbanks area for many years to come. Construction is expected to be complete by January 2026. The dam will continue to operate and regulate the flow of the Chena River as needed while work is underway.
“The successful completion of this modification project will allow us to address the risks associated with aging infrastructure and deliver an upgraded infrastructure that is built to last,” DeRocchi said.
The public is encouraged to stay informed of weather and flooding conditions by monitoring news reports and social media posts. It is also recommended that people remove their belongings from low areas, such as basements and crawl spaces, to protect these items from potential flood damage.
As the USACE prepares for a busy spring that may involve the operation of the Moose Creek Dam to reduce flood risk and make safety improvements to the structure itself, local citizens can rest assured that the team has their best interest in mind.
“Public safety is always our top priority,” DeRocchi said.