Wildfire in North Oregon Cascades Foothills, Oregon

The Riverside wildfire started around 0000PDT on September 8, 2020 in Clackamas county, OR at coordinates 45.049, -122.062. The fire grew to approximately 138,000 acres before being officially declared under control on December 3, 2020. Destroyed were 56 residences and 83 minor structures. There was damage to 19 structures. Affected were the communities of Estacada, Springwater, Dodge, Elwood, Colton, Fernwood, and Glen Avon. During this conflagration 75462 people were evacuated, 1 citizen and 4 first responders injured. The fire is believed to be human caused.

After a period of upper level ridging brought a return to above normal temperatures in early September, very strong easterly downslope and offshore winds off the Cascades and Coastal Ranges occurred. Winds increased rapidly during the afternoon and evening of September 7 with the passage of an unseasonably strong backdoor cold front, and persisted through much of the following day. This resulted in extremely critical fire weather conditions when the strong winds combined with extremely low relative humidity and exceptionally dry existing fuel conditions. The result was explosive growth of ongoing wildfires, and the new start and explosive spread of numerous new wildfires. Widespread wind gusts from 50-70 mph were common on ridge tops and numerous other in exposed areas, including portions of the greater Portland metro area, the Willamette Valley, and areas of the Oregon coast. Strong winds caused widespread damage to trees, and downed numerous power lines across the region, which started at least 13 additional wildfires. Large portions of the cities of Detroit, Mehama, and Gates were destroyed, and significant portions of Idanha, Mill City, and Lyons also burned. Resultant large wildfires included these named incidents - In Oregon: Beachie Creek, Chehalem Mountain/Bald Peak, Riverside, and Lionshead, and in Washington: Big Hollow. Rapidly spreading wildfires resulted in multiple fatalities, hundreds of displaced persons for many weeks, and billions of dollars in damage.