Fire in the Molalla River Watershed

Today, the light outside is an eerie yellow an overwhelming and oppressive reminder of the fires burning in the Cascades https://inciweb.nwcg.gov/incident/7174/. The fire reported as the Beachie Creek Fire (citing The Riverside Fire was an error) was driven by gale force winds and has burned west into the Molalla River Basin. This is one of three fires in the Northern Cascade Range is reported to have burned 120,000 acres, a century event. This fire with the Lionshead and Riverside Fires have burned some 500,000 acres.

This spring and early summer I undertook a series of trips into the Molalla River Basin, mostly in search of Oregon Oak https://www.inaturalist.org/observations?on=2020-05-28&place_id=any&user_id=carexobnupta&verifiable=any, https://www.inaturalist.org/observations?on=2020-06-11&place_id=any&user_id=carexobnupta&verifiable=any, and https://www.inaturalist.org/observations?on=2020-06-24&place_id=536&user_id=carexobnupta&verifiable=any. The current Northwest Large Fire Interactive Web Map is tracking the extent of the Riverside Fire. The extent of burning is clear with the Satellite (MODIS) Thermal Hotspots displayed. The Riverside Fire appears to have burned the locations of the earlier visits.

The first visit was into the Table Rock Wilderness. This location is reported to have been subject to a sever destructive fire in the 1880's https://www.blm.gov/or/resources/recreation/files/brochures/TableRockBrochureWeb.pdf. The access to the Oregon Oak glades was from the Old Bridge Trailhead via the High Ridge Trail. This trail passed through an exceptional forest. As the BLM Table Rock Wilderness brochure implies, two forest ages are present a younger closed canopy forest and an older open canopy forest. The older forest is composed of large diameter Douglass-fir with huge canopies. The understory was highly diverse with both shrubs and forbs. Along the upper reach of the High Ridge Trail there was a second unique landscape, an open conifer canopy with Erythronium oregonum.

The ecological impact of this fire is and will be significant. To understand the nature of the impacts it is helpful to review the 2017 Eagle Creek Fire. Traveling through the Columbia River Gorge since 2017 has been interesting to see the forest recovery. The 2017 Eagle Creek Fire https://en.wikipedia.org/wiki/Eagle_Creek_Fire left a mosaic of fire impacts from crown killing fire to unburned. The US Forest Service has mapped the impact with a Soil Burn Severity map https://www.fs.usda.gov/Internet/FSE_DOCUMENTS/fseprd600997.pdf. From Larch Mountain and the Larch Mountain Trail the fire burn area can be seen in a distinctive way from above along the perimeter. Access to the Table Rock Wilderness is now only possible next year. It will provide a better understanding of the impacts of this 140 year fire event.

While writing this note, Clackamas County just updated the Level 2 Evacuation Zone to 4 miles away and The Oregon Military Department Office of Emergency Management dashboard https://experience.arcgis.com/experience/6329d5e4e13748b9b9f7f33f06a3c376/ reports the Riverside Fire approaching Estacada and numerous fires in the Willamette Valley foothills. Although the wind has subsided down to 2 to 4 MPH the temperature is still high in the 80's. This remains a very threatening situation.

Posted by carexobnupta carexobnupta, September 10, 2020 23:06

Comments

Good summary. We had thought about hiking in Table Rock Wilderness Area this past Sunday, but didn't want to put up with the crowds getting in a last hurrah for the summer. I had hoped to get in a hike this coming weekend somewhere, but that won't happen this weekend, and probably won't until we get some decent precipitation. It will be interesting to return to areas visited that are burning to check on impact and recovery. And it will be emotionally unsettling at the same time, in line with what people felt after the Mount St Helens eruption.

Posted by geographerdave about 1 year ago (Flag)

My thoughts both then and now are of the people of Pompeii.

Posted by carexobnupta about 1 year ago (Flag)

Thanks for the excellent summary from a ecological viewpoint; it will be interesting to see how the area recovers. Meanwhile, my thoughts tonight are for all those in Oregon, Washington and California who are impacted by these devastating fires.

Posted by brewbooks about 1 year ago (Flag)

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