What Wildfires Have Done to Oregon’s Rivers and Salmon

In early November on Coast Highway 101, it’s almost as rainy of a day as it was smoky two months ago. Driving north, I am reminded of that day I drove along a different stretch of the same highway, making an early departure from my camping trip in the Redwoods home to Newport. That morning, I had awakened to a red sun and headache-inducing campfire smell, the latter of which penetrated my tent from far outside any of the metal fire rings in the campground where I was staying. Wildfires in Northern California and Oregon’s west Cascades were burning millions of acres, and prevailing easterly winds brought their smoke plumes all the way to the sea. While of lesser acreage, a fire also burned on the Oregon coast, just an hour’s drive from my home, in a place I previously worked and lived in—the object of today’s drive.   

Back in September, I decided to leave the Redwoods before I had any idea what was going on in Oregon, and on that drive, I passed through perhaps three distinct smoke plumes. To my dismay, the final of these did not dissipate when I finally reached my apartment in Newport. Ash was falling from the sky, and inside the apartment. My partner neglected to close the cracked windows before he headed to work that morning—we are accustomed to sleeping to ocean sounds. I wept as I closed windows, unpacked, and showered. I wished I could stay under that falling water rather than to reemerge to these airborne particles of forest and homes. Instead, I got out, soaked my used towel and placed it at the base of the front door, hoping to prevent any more bad air from coming inside.   

That night I dreamt of smoke encroaching upon me along a trail on the northern California coastline, woke frantic that it was indeed getting harder to breathe, calmed myself enough to call hotels in town and ask if they had central air– a luxury our apartment lacks–wept again after receiving negatives. Before dawn, my friend and former roommate called, already dealing with the emergency at work, worried about her dogs, and hoping I could check in on them. I said yes, of course, and asked if my partner and I could stay at her house overnight, knowing she had a HEPA filter. She said yes, of course, so I stayed there on her couch, dogs snoozing beside me, until the smoke cleared.   

I was lucky.   

“We don’t smell the smoke any longer and we’ve moved into winter, and for many, their brains have turned off, nobody’s thinking about the fires anymore,” Kevin Bladon, Associate Professor in the Forest Engineering and Management Department of Oregon State University’s College of Forestry, tells me later in the month, “but to me this is when all the issues are starting to happen.”  

Bladon has been on site post-fire at all the “Big Five” fires that hit Oregon’s western Cascades in 2020, has worked for OSU since 2014, and has spent the last 15 years focusing his research on wildfire impacts on water quantity, quality, aquatic ecosystem health, and implications to community drinking water supply.  

 Following the Big Five—Riverside, Beachie Creek, Lionshead, Holiday Farm and Archie Creek—as well as the Echo Mountain and Almeda fires, perhaps the longer-term impacts of wildfire will be more obvious for Oregonians than ever before. On the most drastic end of things, people may have lost their loved-ones and homes. While others may have been spared these tragedies, they will still likely feel the impact of their community’s grappling with ongoing clean-up efforts and water quality protection and treatment. Looking even further down the line, many Oregonians will have to contend with the diverse values—many tied to their livelihoods and identity—lost when the forests went up in flames.   

Knowing that these impacts are likely to happen again as climate change induced droughts prolong conditions for severe wildfires to occur, no one can really claim that they won’t be affected by these disasters personally, to some extent, at some point in time. If you were almost anywhere in the state in early September, 2020—the high desert or the mountains or the valleys and yes, even along the sea—I know you have a story at least similar in scope to mine, if not worse. However tired we are of hearing the statistics of our collective pain splayed out in front of us, we might do well as a society to continue thinking about the impacts of these fires—to take actions in their aftermath in the ways we can—even in the heart of winter. 

 Hydrology 101  

When a fire burns a forest, it impacts every aspect of the hydrological cycle,  Bladon tells me over the phone. He begins the story from the top, in the canopy: “When we have a fire that burns the canopy we have less [rain] interception. The precipitation that generally falls on the canopy and doesn’t make it to the soil and evaporates back up—that process no longer functions the way it normally did. So we have more water actually hitting the forest floor.”   

After a severe wildfire, that forest floor is not the same as it once was either. The soil structure itself changes, no longer allowing water to infiltrate as easily. When needles from the canopy and leaves in the understory went up in the flames, their natural waxes and resins – organic compounds—turned to gaseous forms through combustion, then condensed onto soil particles when the fire went out. Bladon says, “It’s like you have this layer of wax coating the soil particles now that causes water to bead up on the surface…it’s like it’s concrete, it’s really unbelievable.”    

Post-fire, there is now more water hitting the forest floor than usual, and the soil is not as conducive to taking it up. As a result, that water flows more rapidly over the soil surface, and, Bladon says, “the whole thing can really start to unravel. We start to see rapid increases in erosion rates and in the worst case scenario, can see mass movements and debris flows that will move a large amount of sediment into our streams.”   

In addition to more sediment being moved into the streams from these processes, recall also that it is being carried there by water—more water itself is reaching the streams after a precipitation event than would have pre-fire. What that does is increase peak flows—think floodwaters—and in turn increases how fast the stream water is moving, enabling it to erode streambanks as well, adding another input of sediment to the system.   

“All of that comes together and leads to pretty dramatic increases in the delivery of sediment into our streams,” Bladon says. He follows up later with photos of the 2015 Stouts Creek fire and this year’s Riverside fire to put imagery behind his words. In one photo, blackened tree trunks and roots emerge out of a grayed soil, and though it’s not being shown here, I can easily imagine the concrete mimicry he has described—beads of water trickling down the soil surface instead of infiltrating it.   

In another photo, the confluence of two streams running through a similarly burned forest is shown. The stream water looks more like thick chocolate milk than the green-blue hues most Oregonians would find familiar in a forested setting. Carried in that water is ash and sediments, and in those constituents, serious concerns for water quality beyond the visible high turbidity. 

 Bladon explains: “We’ve seen wildfires increase limiting nutrients—like nitrogen, phosphorous, and carbon, which are the basic building blocks of aquatic ecosystems—as well as heavy metals like mercury, arsenic, iron, and lead anywhere from two to 2,500-times above their background levels. Such dramatic changes after fires can obviously have some significant implications for our aquatic ecosystems, invertebrates, and fish.”  

In the last photo, one of Bladon’s field crew members gives some scale to a woody debris jam in an otherwise lush-looking streamside forest. Bladon explained that high severity fires will weaken the root structures of trees so much that they are easily toppled by wind after the fire’s out. If they are on a steep enough slope or directly situated along a streambank, they will make it into the aquatic environment and move through it until they hit a constraint, then pile up. There are positives and negatives to this.   

Winners and Losers  

On the one hand, “we know that wood in streams for fish can help to provide some additional heterogeneity and structure in our streams that is not normally there, it can create pools and riffles that can benefit fish. We know some amount of input of wood to streams is really valuable to create complexity in habitat which helps fish.”    

“The problem is,” Bladon says, “in some places, the scale of the input of wood can then create barriers to migration. If you’re in a location where fish are anadromous and are moving back up into areas for spawning, too much wood can create those barriers.”   

Looking at that last photo, I wonder if a salmon or steelhead returning to spawn could make it through that huge woody debris jam. Salmonids are known for their resilience, for having evolved in places where wildfires and landslides have always played a role in creating the watersheds they occupy to spawn and rear in. But after millions of acres have burned this summer, the scales seem set more in line with supernatural than natural processes. For a salmon or steelhead that is migrating upstream and has already had to contend with fishing nets, urban chemical runoff, dams, undersized culverts, and chocolate milk tinted stream water—what if, this year, in some rivers and streams, that huge woody debris jam is one impact too many?   

“When you push the chair back it really depends on your perspective, there’s always winners and losers,” Bladon reminds me.   

This year, both salmonids and societies may find themselves on the losing end of some issues.  

When wildfires are actively occurring, the cost of the disaster is usually tabulated in terms of fire suppression, or how much it costs to put them out. Bladon explains to me that this cost has grown dramatically in recent years, with three of the last four years seeing an excess of three billion dollars to suppress fires.   

However, natural resource economists can’t quite pinpoint such an exact dollar amount when it comes to summing up the loss of values that occur after the fires are put out—things like the loss of recreational value and tourism, the loss of usable lumber for the mill to process, as well as all of the implications to water, including treating it for safe human usage. Currently, “the estimates on those are anywhere between two and 23 times greater than the suppression costs alone,” Bladon says.    

While these long-term costs of wildfires are so staggeringly large to the point that they may feel abstract, there are some concrete management actions humans can take to lessen the burden, and they are not completely constrained to the hands of trained scientists or land managers alone.   

Check back tomorrow for Part II of this series to learn how some of these methods are being applied.   

If you are interested in making a monetary or material contribution to support the needs of local communities impacted by September’s wildfires, consider donating to the following organizations: 

By Ari Blatt

Go To Part 2

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