1999 Boundary Waters Canoe Area Derecho

Among the most remarkable derechos to have impacted the National Forests of the US in recent decades occurred on the fourth of July 1999. It crossed through the Superior National Forest near the Canadian border. The Boundary Waters Canoe Area Wilderness was hit especially hard, as were a large number of campers and canoeists who were on holiday there and then. 

A vast number of trees were snapped off by high winds that surged in excess of 90 mph. Estimates were that 25 million trees were killed over 370,000 of the 1 million acres of the Wilderness area. That is roughly a third of the Wilderness area.

Using Landsat 5 in HiForm, the damaged area was mapped to be about 50km (30 miles) long and from 5 to 20km (4 to 12 miles) wide, consistent with earlier assessments.