Spanning northern Wisconsin's Ashland and Iron Counties, the 125,000-acre Bad River Reservation contains portions of the Bad River, Beartrap Creek and Denomie Creek. In July 2016, 8-10 inches of rain fell on the Bad River watershed over a roughly 24-hour period, resulting in severe flooding that washed out roads, damaged critical infrastructure and led to multiple fatalities (Novak, 2016). The USGS streamgage on the Bad River at Odanah rose to a peak of 40,000-cubic-feet per second, the highest recorded streamflow since the gage was built in 1948. Record streamflow values were also observed on the nearby White and Tyler Forks Rivers.
When a flood occurs, it's important to know how far the flood waters reached and how deep they were so the community can prepare for and mitigate future floods. For the July 2016 flood, the USGS and Bad River Tribe partnered to measure and map the floodwaters. To understand how much water flowed during the storm, the USGS collected continuous streamflow data during the storm and peak water-surface elevation data captured at the highest point of the flood.
To understand where the floodwaters went, the Bad River Natural Resources Department and USGS identified and surveyed more than 100 high-water marks – physical evidence of floodwaters left behind on vegetation and buildings. The Bad River NRD identified high-water marks in the Bad River Reservation immediately after the flood. And because of their quick response using USGS high-water mark protocols, they were able to thoroughly and reliably document the floodwaters before the high-water marks became compromised by weather and time. Additional high-water marks were collected by the NRD and USGS over a broader area in and around Odanah through September 2016.
From all these data, the USGS was able to create flood inundation maps for the Bad River, Beartrap Creek and Denomie Creek that show the depth and extent of the flooding that occurred. These maps will be used to prepare for future floods and estimate the probability that a similar flood could happen again.
To explore the July 2016 flood inundation maps, view photos of the flood and high-water mark collection, and learn more about flood inundation mapping, check out the "Measuring the July 2016 flood in northern Wisconsin and the Bad River Reservation" story map.