How do wildfires affect flooding?

Washed away road

NPS Photo/Bridget Edwards

Flooding is a major concern after a wildfire, even in the arid desert. Desert environments are naturally prone to flash flooding because of their soil and vegetation profiles. Plant root systems help retain moisture and stabilize the soil. Plants in the Mojave Desert are spaced out, so the landscape has a limited capacity to accept water, and the soil itself is compacted, so water doesn’t quickly penetrate the surface. This desert soil is unable to keep up with the amount of water it receives during heavy rain events, particularly in the monsoon season. With nowhere else to go, water flows from high points on the landscape to low points, often in high volume, which creates flash flooding that can destroy human infrastructure. When a wildfire burns through the desert, it removes the already sparse vegetation, decreasing the soil’s ability to absorb water and increasing the capacity for water flow to cause more damage. Mojave National Preserve’s infrastructure was built to sustain rain events before the York Fire changed the landscape. This makes structures like roads, buildings, and culverts more vulnerable in post-fire rain events. Culverts in the preserve may be unable to manage the amount of water during a heavy rain event; causing roads to flood, buckle, and become undercut. This creates unsafe or impossible travel conditions.The Burned Area Emergency Response (BAER) team has been helping the preserve prepare for rainstorms that may pose threats to life, safety, and property. BAER hydrologists used field data and historic data to create predictions about what might happen during different instances of rain. They created virtual models that predict the impact of moderate, heavy, and extraordinary rain events to advise the management team at the preserve on how to prepare and mitigate the effects of rain after the York Fire.The roads at the preserve allow the public to visit this special place. With the support we’ve received from the BAER team, preserve management is better equipped to address infrastructure vulnerabilities that might otherwise limit visitor access. We’re grateful for the knowledge and support we’ve received from these experts!