What Should You Do After a Mudslide or Debris Flow?


The California Governor’s Office of Emergency Services (Cal OES) is geared up to address any potential hazards, such as mudslides, debris flows and other incidents triggered by excessive precipitation.  

The Cal OES Watershed and Debris Flow Task Force is actively overseeing high-risk zones to ensure communities receive prompt emergency information in the event of debris flows. If rainfall is expected to meet dangerous thresholds, the hazards are communicated to local jurisdictions.  

In preparation for heavy rainfall, Cal OES works with counties and state partners to install emergency protective measures prior to high flow events. These efforts address slope instability to protect lives and infrastructure.  


Mudslide and debris flow events, often triggered by heavy rainfall and subsequent soil saturation, are characterized by the rapid downhill movement of soil, rocks and other debris. Understanding the intricacies and triggers of mudslides and debris flows is essential for communities situated in regions prone to these occurrences. 

  • Mudslides: a type of landslide that result from the failure of a slope, and often occurs due to the accumulation of water from prolonged rainfall and/or saturated subsurface conditions.  
  • Debris Flows: described as a “sediment-dominated slurry,” debris flows are mostly made up of soil, resulting from short-duration, high-intensity rainfall events.  
  • A mudslide is a localized slope failure, while a debris flow is a runoff event, such as a flash flood, that entrains sediment from a broad area.  
  • Debris flows and mudslides can occur many years after wildfires. Both happen fast, so heed evacuation warnings immediately 


  • Emergency Services: Post-event, emergency services play a pivotal role in response efforts. Californians should expect a coordinated response, including search and rescue operations, medical assistance and the establishment of emergency shelters. Wait until emergency officials declare the area safe before returning to your home.  
  • Immediate Safety Concerns: Californians should prioritize safety in the aftermath of mudslides and debris flows. Be cautious of unstable ground, potential structural damage and ongoing hazards. 
  • Environmental Impact: Anticipate environmental changes, including disrupted infrastructure such as blocked roads and utility disruptions. Community members should prepare for potential sheltering-in-place scenarios and consider evacuation routes including alternatives. 
  • Evacuation Protocols Post-Event: Be aware that authorities may issue evacuation orders even after the initial event due to ongoing risks. Community members should stay informed and promptly follow official guidance to ensure their safety. 
  • Infrastructure Challenges: Expect challenges with transportation routes and utilities. The movement of debris, including trees, can hinder transportation and access to essential services. Californians should plan for potential disruptions and have alternative routes in mind. 
  • Terrain Reassessment: Assess the vulnerability of steep terrain, particularly in areas downhill and downstream from burned zones. Understanding the landscape’s post-event vulnerabilities is crucial for residents to mitigate risks effectively. Look for continued changes in debris placement and ongoing downhill erosion.  

After high-flow events, health hazards remain, including broken utility lines and disrupted infrastructure. Other risks lie in the debris itself as sharp or heavy objects can be displaced and hidden. 

Also, be sure to know what disasters your region is most susceptible to. To check your hazards, visit: https://myhazards.caloes.ca.gov/ 


Understanding the geographical and environmental factors contributing to these events in the region is crucial. This knowledge empowers individuals to make informed decisions about where to live, work and recreate, considering the potential risks posed by natural hazards. 


In areas affected by intense wildfires, soils may repel water due to the charred remnants of organic material. Less precipitation is required to produce flash floods, and the potential for mudslides and debris flows increases, especially in downhill and downstream locations from burned areas. 


In the early morning of January 9, 2018, when mud and debris loosened from burn-scarred areas in the Santa Ynez mountains and plowed through Montecito, a small coastal town of only 8,600 people. Tearing through homes and streets, the incident was responsible for grave injuries and the destruction of more than 100 residences.  


Mudslides and debris flows can easily knock out power lines and other critical infrastructure systems. Sign up for local alerts with your utility company to stay informed about possible power outages and public safety power shutoffs in your area. For those who require power for medical needs, contact your local utility providers for the medical baseline program which offers early notifications of possible shutoffs that give residents time to adjust emergency plans. Generators can also be helpful when the power goes out. Generators should be used properly, like using them outdoors and keeping them dry and protected from the elements.