Wyoming has seen an unusual amount of snowpack in many parts of the state, causing concern of flooding in some counties.
One of the counties with the highest threat of flooding is Fremont County, specifically around the towns of Lander and Riverton. The region has collected around 190% of the average snowpack this winter and spring. According to the 2017 Wyoming Spring Snowmelt Flood Potential from the National Weather Service, Freemont County has a flood potential of 80% or greater and is one of the most at-risk areas in the state. Other areas that have a moderate to high (40-80%) risk of flooding include Dubois, Pinedale and Jackson.
“Our trigger points are if we get three days of 80-degree weather down here in the basin, that’s going to keep it above freezing on the mountain, which will allow that melt to continue during the night and that will raise our moisture,” Kathi Metzler, Coordinator of Freemont County Emergency Management, said. “If we develop rain on snow when the snow is extremely ripe and ready to come, that will increase our runoff there with that aspect of it.”
The Pogo Agie River originates in the Wind River Mountain Range and runs near both Lander and Riverton, but the latter city is generally safe from flooding because of its position above the river. One of the main drainages from the river runs directly through Lander and close by the town of Hudson, and could cause problems if not dealt with properly.
Metzler said the flooding could affect homes, the water treatment plant near Hudson, wells inside of the county, and even the drinking supply in Lander. If the runoff makes it to the street level, the flooding could also raise the levels in the sewer lagoons, which would require specially approved pumping to lower the levels. Another concern is the bridges along the river and potential debris damaging or destroying them.
“At this stage in the year we’re monitoring weather forecasts, long range forecasts, averages for temperature and precipitation, local weather conditions, weather gauges, that type of thing to stay ahead of it and hopefully be informed before all of a sudden [flooding] happening for us,” Metzler said.
Hudson has hosted sand bag parties, filling sand bags to help protect some of the homes along the river that generally have problems with flooding. Lander has been preparing in a similar fashion, handing out sand bags to citizens that they fill themselves.
Lander has also considered the construction of the”Wall of Fremont”, which is a Hesco bastion placed on Fremont street to direct the water back to the nearby creek.
“We would encourage people, if they’ve had historic flooding problems, to obtain sand bags,” Metzler said. “We’re providing the sand bags through the county but we’re not providing the fill material. Those sand bags can be obtained through the vehicle maintenance shops in Lander and Riverton during normal business hours.”
The southeast part of the state hasn’t seen as much snowpack this season, and although Laramie is at 20-40% risk of flooding, the nearby Saratoga has historically had flooding problems, with two major flooding seasons in both 2011 and 2014.
“The thing you have to remember about Saratoga and the North Platte River is there is no control above it, it’s not like Casper, Douglas and the state where you have major reservoirs above that have the ability to control some of the flow,”
Jon Winter, Director of Saratoga Public Works, said. “This is free flowing from the peak of the edge of the drainage basin into Saratoga.”
The city works with the Local Emergency Planning Commission in Carbon County, Homeland Security, and if necessary, the National Guard to help provide assistant in the event of flooding.
“When you look at the predictions on the snowpack sites, you have to realize that obviously there is a bunch of snow up there and there is a lot of potential,” Winter said. “It all has to do with how the snow comes off. You could have various years where you have well above the mean [snowpack], but if it comes off cool and steady, you can be thankful and not have much of a problem.”
