How does fire contribute to flooding and erosion hazards?

Wildland fires are inevitable in the western United States. Expansion of human development into forested areas has created a situation where wildfires can adversely affect lives and property, as can the flooding and landslides that occur in the aftermath of the fires.  Wildfires change the landscape, destroying root structure and creating top soil that could repel water instead of absorbing it.  

Post-fire landslide hazards include fast-moving, highly destructive debris flows that can occur in the years immediately after wildfires in response to high intensity rainfall events, and those flows that are generated over longer time periods accompanied by root decay and loss of soil strength. Post-fire debris flows are particularly hazardous because they can occur with little warning, can exert great impulsive loads on objects in their paths, and can strip vegetation, block drainage ways, damage structures, and endanger human life. Wildfires could potentially result in the destabilization of pre-existing deep-seated landslides over long time periods.

Flood After Fire - Video from the Department of Water Resources

Show All Answers

1. How should we prepare our property for rain?
2. How does fire contribute to flooding and erosion hazards?
3. What does fire do to the soil?
4. What are hydrophobic soils?
5. How does fire turn soil hydrophobic?
6. How do I tell if my soil is hydrophobic?
7. What is a flash flood?
8. What is debris flow?
9. What is a mudflow?
10. Debris flows and mudflows sound similar. How are they different?
11. What is the difference between a debris flow and a landslide?
12. Why are debris flows and mudslides so dangerous?
13. Where do debris flows occur?
14. What are the flooding and debris flow impacts that could potentially occur after a fire? For how long after the fire am I facing potential threats?
15. What type or size of storm event should I be concerned with?
16. What are some of the warning signs of a potential landslide or debris flow?
17. What effect does fire have on the trees on my property?
18. What steps should I take before removing trees on my property?
19. Can I remove trees that do not pose a health and safety hazard?
20. Does it matter what type of trees I would like to remove?
21. Can I remove burned trees and install a vineyard or other project in their place?
22. My property did not burn. Should I be concerned with post-fire debris flow and/or erosion?
23. Are there other organizations and agencies that can provide financial and technical assistance tree removal and watershed protection?
24. How do I protect my property from erosion, flash flooding, mudflows, and debris flow?
25. I'm concerned that using straw mulch as erosion control will increase my fire risk.
26. What is the purpose of the debris flow mitigation advice that Engineering offers in fire-affected areas?
27. I rent or lease my home. Will Napa County notify me and provide me debris flow mitigation advice?
28. Will Napa County install the erosion control measures for me on my property?
29. Where can I get assistance in placing erosion control measures on my property?
30. What do I do about debris that deposits on my property?