Yellowstone River flooding is a 1 in 500-year event, US Geological Survey says

The devastating flooding that occurred along the Yellowstone River this week constitutes a 1 in 500-year event, according to a US Geological Survey (USGS) news release.The devastating flooding that occurred along the Yellowstone River this week constitutes a 1 in 500-year event, according to a US Geological Survey (USGS) news release.