USGS installs 2022 high-water markers to provide flood information

Historic flooding on June 12-13, 2022 occurred in the Gallatin, Absaroka and Beartooth Mountains of Montana and Wyoming, near Yellowstone National Park. The flooding was initiated by rainstorms that produced between 1-5 inches of rain on top of an above-average snowpack, causing the snow to melt faster and rush downstream. The combined rain and melted snow led to record floods on the Yellowstone, Boulder, and Gallatin Rivers and Rock Creek near Red Lodge, Montana, as well as many other streams and rivers in the area.

The US Geological Survey, in cooperation with the Montana Silver Jackets and local communities, plans to add high water mark signs to mark the highest level the rivers reached during the flooding. These signs will provide the date of flooding, site information, the maximum flood depth (known as river stage, in feet), and links to the National Weather Service’s river forecasting website and US Geological Survey’s streamgage website.

Streamflow has been measured along the Yellowstone River for over 100 years and these data are used to estimate the frequency of large flood events. The floods of 2022 ranged from once in 100 years to once in 500 years likelihood. Though the chances of these floods are rare, they have an equal chance of happening each year, so it is always possible to have historic flood events back-to-back.