In September 2020, a windstorm sparked five “megafires” in Oregon that spread to more than 100,000 acres. At the same time, twelve other fires, spanning from 100 to more than 50,000 acres, broke out. Within days, more than one million acres of western Oregon were torched, decimating forests, destroying 5,000 homes and other structures, and killing nine people. The 2020 Labor Day Wildfires were the most destructive sequence of simultaneous wildfires in Oregon’s history.
Will Long (USGS) had just moved to Portland to start his Master’s program in Geography at Portland State University when the wildfires erupted. This historic event influenced Will and Heejun Chang (PSU), professor of geography, to study wildfire impacts in their recent paper, “Spatial analysis of streamflow trends in burned watersheds across the western contiguous United States.”
Published in Hydrological Processes, this paper explores the impact of wildfires on the hydrology of watersheds across the western contiguous United States (WCONUS). Will and Heejun computed trends for commonly-used landscape metrics, which quantify the spatial patterns of fires, and studied 130 different watersheds burned between 1984 and 2020. These variables were then used to compare the output of two different models: Ordinary Least Squares, a linear regression, and Geographic Weighted Regression (GWR), a novel spatial analysis approach in post-fire hydrology.
Their research examined the metrics of peak flow, low flow, center timing of flow, and Richard-Baker Flashiness Index. Will explains, “We hypothesized that there would be some obvious clustering of metrics in certain regions. We confirmed that by finding positive peak flow trends clustered in the central Rockies, around Yellowstone, and then we found negative peak flow trends in the Southwest desert– findings that had already been documented.”
They noticed that center timing of flow, which is the time when 50% of a river’s streamflow has passed for the year, was trending earlier and earlier in the season in the Yellowstone watershed, the eastern Pacific Northwest, and areas in the Texas Gulf.
The researchers were somewhat surprised to discover that the R-B Flashiness Index, which measures how quickly a river might respond to a rainfall event, was dispersed across the study area. Even more astonishing was the output of the landscape shape index metric, which quantifies the fragmentation or aggregation of burn severity patches. This metric was significant in explaining peak flow trends across WCONUS and their results suggest that there are spatial patterns of fire, or at least, that fires are influential in the spatial patterns of trends.
The Benefits of a Collaborative Partnership
Heejun Chang has conducted collaborative research with USGS scientists since he arrived at PSU more than 20 years ago. “I think PSU faculty and USGS scientists have complementary expertise, [so] this partnership provides great collaborative opportunities for everyone.”
One of Heejun’s PhD students, Junjie Chen, contributed to this project, creating a database important for spatial analysis. After this experience, Junjie went to work for a County office and then a consulting company and attributed his success to the technical and soft skills he learned from collaborative work.
“I asked [Junjie], ‘how did you get a job in this field?’ and he said employers are not only looking for specific technical skills, but also people’s collaborative and communication abilities.”
Heejun hopes to see his PSU colleagues take advantage of the UPP and what this partnership has to offer–even something as small as attending a networking event.
“The UPP’s networking events are a place where people can discuss their ideas and interests in a more casual or informal way. Those social gatherings and spaces for creating mutual trust are important, but you have to be willing to go there first,” says Heejun. “I always believe that having more than one brain is better. The water system is complex, so we need different experts and diverse ideas to solve its issues.”
Will sees the value in this partnership because it enables organizations like USGS to leave their usual schools of thought and paradigms and be exposed to new ways of thinking.
“The USGS relies heavily on its techniques which we are proud of and consider the gold standard for hydrology, but sometimes we rely on methods that are very old and very proven. It’s great to come into a university setting where there’s constant progress and new ways of thinking. I’m hoping to take some of what I learn back with me in my day-to-day work.”
From Grad Student to USGS Hydrologist
After starting graduate school, Will was hired through USGS as a hydrologic technician where he conducted water quality studies in Upper Klamath Lake.
“Coming here to Portland gave me the opportunity to go to PSU. I was able to participate in the UPP, and that streamlined my track to begin working as a hydrologist after graduation,” says Will. “The UPP was instrumental in my transition from hydrologic technician to a hydrologist. There was opportunity for collaboration and networking, and being within the university bubble.”
Students interested in working for the USGS should expect on-the-job training for entry-level positions (such as a hydrologic technician), but should also be familiar with different types of hydrologic field work, such as taking discharge measurements and collecting water quality samples, and understand why it is important to collect these data.
Will also advises students to understand the unique requirements for a hydrologic technician versus a hydrologist.
He suggests “looking at what the [federal] Office of Personnel Management lists for their position requirements. This could help students plan their educational track to ensure they understand the basics and know what math and physics courses they need to take to be a technician or a hydrologist. This can help open doors down the road and avoid having to retake classes.”
Next Steps
Will and Heejun hope their work can act as a jumping-off point for future post-fire hydrology research. As climate change and wildfire events become more common, water resource managers will need to develop strategies to mitigate their impacts on watersheds. As Heejun explained, “When you have peak flow, you will have concerns about turbidity, or the measure of relative clarity of water. When you have low flow, stream temperature can increase which may cause more frequent algae growth, which will eventually increase the cost of drinking water treatment.”
They also hope new research can conduct more in-depth analysis through studying adjacent watersheds, characterizing the stream flow of re-burned watersheds, and implementing GWR in future large-scale, post-fire investigations.