Understanding Post-Fire Hydrology: Published Research Study Insights

Congratulations to WRA Hydrologist/Geomorphologist Junjie Chen, PhD, first author of a research paper, “Predicting Post-Wildfire Stream Temperature and Turbidity: A Machine Learning Approach in Western U.S. Watersheds,” published in MDPI Water Journal in 2025. The following Field Notes blog summarizes insights from this study.

Wildfires are reshaping landscapes across the western United States, and their impacts extend far beyond the flames. One of the most overlooked consequences? How wildfires affect water quality. The recent wildfires in Los Angeles have once again highlighted the devastating chain reaction wildfires can set off—including post-fire mudslides and debris flows that further disrupted communities and infrastructure.

Why Does Post-Fire Water Quality Matter?

When a wildfire burns through a watershed, it removes vegetation that stabilizes soil and provides shade to streams. In areas that experience severe burn intensities, soil surfaces can also become “cemented”, reducing infiltration and increasing runoff. Without this natural cover and infiltration capacity, heavy rains trigger rapid erosion, washing sediment into waterways.

Post-fire sediment loading comes from multiple sources—not just hillslopes, but also degraded stream channels. In some cases, fire-damaged streambanks and channels contribute more sediment to downstream waters than hillslopes themselves. For example, recovery efforts after the Waldo Canyon Fire in Colorado revealed that unstable stream channels were responsible for nearly 60% of sediment contributions, compared to 40% from hillslope erosion. This highlights the importance of monitoring and stabilizing streams alongside traditional watershed treatments.

How Can We Better Predict and Manage These Changes?

Advanced tools like machine learning can help anticipate how wildfires will affect water quality. By analyzing past wildfires and their hydrologic impacts, we can improve predictions for stream temperature, sediment loads, and long-term watershed changes. This kind of forecasting can give water managers a crucial head start in preparing for post-fire challenges.

Key lessons from recent events:

• Mudslides and debris flows are an inevitable consequence of wildfire-damaged landscapes, but better modeling can improve risk mitigation.
• Reservoirs and stormwater systems need to be prepared for post-fire sediment surges.
• Rapid response water quality monitoring is critical for detecting and addressing contamination before it reaches drinking water supplies.

What This Means for Water Resource Management

Recent wildfires and mudslides in Los Angeles highlight the need for proactive water management in wildfire-prone regions. Key strategies include:

• Stream stabilization: Fire-affected streams often experience incision and bank erosion, contributing significant sediment loads. Interventions like grade control structures, engineered log jams, and bioengineering can help stabilize channels and reduce sediment transport.
• Riparian restoration: As streams recover, planting along banks can stabilize soils and provide shade to reduce temperature increases. However, restoration should align with the stream’s recovery stage—stabilization must come first in actively adjusting channels.
• Real-time water quality monitoring: High-frequency sensors can detect turbidity spikes early, guiding treatment plant responses.

At WRA, Inc., we apply science-based solutions to wildfire resilience, watershed planning, and water quality management. Contact us to explore how we can help safeguard water resources in a changing climate.