Locally, as we watch break-up take place and prepare for potential flooding, others are doing the same around the state. Forecasts from State and Federal agencies indicate a higher than normal risk of flooding in the Interior and other parts of the state.
The National Weather Service Forecast Office (NWS) has issued a special weather statement concerning Southeast Interior Alaska. The warning says anticipated increased temperatures this weekend will cause increases to ice melt that may result in flooding.
Highs are forecast to be in the 50s and possibly 60s for the next week with overnight lows increasing to above freezing – both conditions should increase melting.
Lower elevations are said to still have five inches of water in the snowpack, while higher elevations may have a foot or more of water in the snowpack. Water content of the snowpack determines the amount of melt that is expected in an area.
According to the NWS, the melt should be more significant on south facing slopes.
Three types of flooding potential exist in the local area. Riverbank erosion, ice-jam flooding, and localized snowmelt flooding.
Riverbank erosion, such as that seen in 2020 along Spengler Road and the Delta River results from both channel alignment in the river and ice jams. As the braided river channel moves and flows increase from upland melt, channels along the riverbank fill and erode the bank causing overflow in low lying areas.
Such flooding potential exists every year and is determined by the snowmelt rate mostly in upper elevations.
Ice-jam flooding occurs when large pieces of ice stop moving in the river and create a dam. These ice jams can back up water for miles and spill over the banks. With the exception of Jarvis Creek, the local area has generally been spared from such flooding.
Backups in the upper portions of Jarvis Creek can divert significant amounts of water into the old river bed that runs under Nistler and Jack Warren Roads and into the Tanana Loop Extension area. When the water backs up and then releases, amounts can increase quickly and overflow the old riverbed.
Flooding is usually first seen on Nistler Road near Emmas Road as backups occur where the water flows under Nistler Road.
Localized snowmelt flooding occurs every year and can be seen in the form of ponding in yards, fields, parking areas, and other low-lying areas. As the areas grow or form in new areas, localized flooding can occur. This was the problem in 2020.
As snow melted in 2020, the water seemed to run to different places than in years past. As the water flowed under the existing snow, it became diverted and flowed to other low-lying areas. The flooding visible to most people was along the Alaska Highway at in the vicinity of Delta Meat and Sausage and along Jack Warren Road.
When Delta Meat and Sausage flooded, the water flowing adjacent to the property diverted onto the parking lot at the plant. From there, the water was prevented from flowing onto the adjoining ground due to existing snow and ice, thus never reaching the ditch along the road and being able to flow downstream as it normally would.
A similar situation developed on Spriggs Lane where water from several properties became trapped by the road and flowed to the lowest lot in the area creating a significant flooding event.
There seems to be no way to predict where such flooding will occur other than the water flows to low-lying areas.
Properties owners need to take precautions to prevent flooding, including giving the snow melt a path to follow. Individuals should clear ice out of drainpipes, culverts, and drainage ditches and move vehicles to higher ground. Those with basements or garages that are subject to flooding should move items off the floor to prevent damage.
Local emergency responders have sandbags and pumps available to assist those that experience flooding. Responders can be dispatched by calling 911.
Individuals have made inquiries with local emergency service agencies about obtaining sandbags. Generally, these sandbags are acquired as part of an emergency supply and aren’t available for mitigation activities. Bags can be purchased from hardware stores and ordered online. Purchasers must then acquire sand, dirt, or other fine material to fill the bags and store them.
The Salcha Delta Soil and Water Conservation District has conducted two flights to review the conditions along the Jarvis Creek southeast of Fort Greely. The latest survey showed the location of the ice as approximately three miles further north than in previous years.
Conditions near the BAX, which is where water has previously escaped Jarvis Creek, appears to be staying in the creek.
The report says, “The area upstream of the BAX training area which usually sees ice formation in the forest appears to have little if any ice this year, and this is likely to decrease impacts to the BAX, as well as areas outside military lands along the Alaska Highway and Nistler Road. This will need to be monitored as the spring progresses.”
A release from the Alaska Division of Homeland Security and Emergency Management said break-up flood potential from Interior rivers is above average due to multiple conditions.
“Due to above average snow fall, infrequent thaw/freeze episodes and thick, in-place ice, the ice-jam flood potential for several interior Alaskan rivers is above average this spring,” said the release.
“We see some type of flooding each and every spring, but conditions this year require extra preparation based on current conditions. Only time will tell where flooding occurs and how severe the inundation is, so every community should be prepared,” said Mark Roberts, SEOC (State Emergency Operations Center) River Watch incident commander. “In addition, the large amount of snow could cause spring flooding not associated with an ice jam.”
According to Maj. Gen. Torrence Saxe, commissioner for the Department of Military and Veterans Affairs and adjutant general of the Alaska National Guard, the National Guard is preparing to assist throughout the state if the need arises.
“With the elevated risk of flooding this spring, the Alaska National Guard is leaning forward in the event of an emergency,” said Saxe. “We are ready if rural communities need help.”
The River Watch program provides aerial surveillance to get real-time updates so that accurate, on-scene flood advisors and warnings can be issued.
The Alaska Army National Guard’s Golf Company, 2-211th General Support Aviation Battalion will conduct its annual training requirements in western Alaska this year from April 30 to May 12 to assist with River Watch.
The unit prepositioned two Black Hawk helicopters each in Bethel and Nome in preparation. When training kicks off Bethel will have two HH-60M (Medevac) and two UH-60L helicopters. Guardsmen will train with three UH-60L aircraft out of Nome. Both locations will have hoist capable aircraft to support a wide range of emergency rescue scenarios.
“Conducting annual training in western Alaska gives our air crews valuable experience flying across all types of terrain and conditions,” said Saxe, “Also, our Guardsmen and their aircraft will be strategically located to provide emergency assistance to communities along the Yukon and Kuskokwim rivers that experience a flood disaster.”