Mudflow Information

Posted on 02/13/2025

PAGE UPDATED 3/6/2025

Mudflow Risk & Preparation for Upcoming Storms
The City of Sierra Madre is closely monitoring two incoming storm systems that may increase the risk of mudflows and debris flows, particularly in areas impacted by recent fires. Residents in high-risk zones should be aware of these forecasts and take necessary precautions to protect their property.

Storm Forecasts & Potential Impacts

First Storm: Monday, March 10 – Tuesday, March 11
Expected Impacts: Light to moderate rainfall, with limited risk of significant mudflows. However, saturated soils may increase vulnerability for the second storm. 



Second Storm: Wednesday, March 12 – Friday, March 14
Expected Impacts: Heavy rainfall over multiple days, increasing the risk of mudflows, debris flows, and flooding in burn scar areas and steep terrain.



Residents in flood-prone areas should remain alert for potential evacuation warnings.

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Public Safety Update: Evacuation Warning Issued for Upcoming Storm

No Phase Alert Issued by Los Angeles County
Los Angeles County has issued a "Phase 1" alert for the upcoming rain event. However, due to potential flooding and debris flow risks, the City of Sierra Madre is issuing an Evacuation Warning for high-risk areas, effective 6:00 AM on Wednesday, March 5, through 6:00 AM on Friday, March 7, 2025.

🚨 NO STREET PARKING IN DESIGNATED EVACUATION WARNING OR ORDER AREAS.

Important Information About This Storm
Unlike the mid-February storm, which filled all local debris basins to capacity, this storm presents a Phase 1 event. Although debris basins have been partially cleared, they are not empty. Any significant rainfall could trigger severe flooding, mudflows, and debris flows.

🔴 Once a mudflow starts, it is too late to evacuate.
🚫 Public safety and public works crews will NOT be able to enter an active debris flow zone.

If you choose to stay behind, you could be trapped for days before emergency crews can reach you. Do not put yourself or first responders at risk.

Evacuation Warnings & Orders – What You Need to Know

• Evacuation Warning (Effective March 5 at 6:00 AM)
• Prepare now: Pack essentials, secure your home, and plan where you will go.
• Genasys App Update: You may not see the “Evacuation Warning” in the Genasys App until it becomes active on March 5 at 6:00 AM.

Evacuation Order (If Issued)

• Mandatory evacuation: You must leave immediately.
• Do NOT delay. Once conditions worsen, roads may become impassable.
• Emergency responders will NOT be able to assist you once debris flow begins.
• Ignoring an Evacuation Order puts you and first responders at risk.

What You Need to Do NOW

✔ Stay alert – Monitor weather updates and city alerts.
✔ Be prepared – Have your emergency bag and evacuation plan ready.
✔ Follow orders – If an Evacuation Order is issued, leave immediately.
✔ Parking Restrictions – No street parking is allowed in designated Evacuation Warning or Evacuation Order areas.
✔ Sandbags – Available for residents at the City Yard.

Evacuation Warning Zones (Effective March 5, 6:00 AM)

Residents in the following zones should be prepared to evacuate if conditions worsen.
Check theGenasys App to find your zone.

Evacuation Warning Zones:

SMD E002B
SMD E003
SMD E004
SMD E005
SMD E006A
SMD E006B
SMD E007
SMD E008
SMD E009
SMD E010A
SMD E010B
SMD E010C
SMD E011A
SMD E011C
SMD E012A
SMD E012B
SMD E012C
SMD E012D
SMD E019

🚫 NO STREET PARKING ALLOWED in areas under an Evacuation Warning or Order.

🔎 Check the Genasys App to see if you are affected and for real-time updates.

Instructions & Next Steps

• Evacuation Warning takes effect at 6:00 AM on Wednesday, March 5, 2025.
• Check the Genasys App to confirm if your area is affected.
• No street parking is allowed in Evacuation Warning or Order zones.

For updates and further instructions, continue monitoring official city alerts. Your safety is our priority.

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Temporary Parking Restrictions & Service Changes

Canyon Crest Drive – No Street Parking

Effective immediately: No street parking from 7:30 AM to 4:30 PM, seven days a week.

This restriction allows heavy equipment access for the removal of an estimated 200,000 cubic yards of sediment and debris from the Sierra Madre Dam and other debris basins in the city.

To date, 80,000 cubic yards have been removed from the Sierra Madre Dam.

Other Parking Restrictions & Temporary Closures

• All other "No Street Parking" orders have been lifted.
• However, streets may be intermittently closed for additional cleanup and water leak repairs.

County Crews will also clear and maintain all Sierra Madre debris basins, but no additional parking restrictions are required at this time.

Resident Access & Traffic Control

• County personnel will assist residents with accessing and leaving their homes during operations.
• All persons in the area, whether in vehicles or walking, must follow the directions of County traffic control staff.

Private Property Mud & Debris Removal

To clarify the level of assistance available to residents dealing with mud and debris accumulation on private property:

• City Public Works crews will NOT enter private property to remove mud and debris.
• Residents will have a designated number of days to move storm-related mud and debris to the street for removal by heavy equipment.
• Household and landscaping waste are NOT permitted in debris piles for removal.

Debris Removal Timeline

• The timeframe for removal will be determined based on the severity of the storm event and will account for weekends and holidays to allow residents sufficient time.
• The specific number of days will be announced as soon as possible following a storm event or series of events.

Stormwater Quality Regulations

• Once street sweeping or washing has occurred, additional deposits of mud or debris on the street are prohibited under stormwater regulations and may result in fines.

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Key Actions to Take Now:

Stay informed - Sign up for emergency alerts. 
Know your evacuation zone - Use the Genasys Protect App. 
Prepare your home - Secure property and access mitigation resources. 

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Evacuation & Emergency Notifications

Some areas may require evacuation. Be ready and monitor updates.

How to Check Your Evacuation Status:

Genasys Protect App

• Provides real-time, zone-based alerts regarding evacuation orders and warnings.
• Find your zone: Search Your Zone Here
• Enter your address in the search bar.
• Press Enter or click the search icon.
• Your zone ID and status will appear on the map.
• Download the app:
• iOS (App Store)
• Android (Google Play)

Sign Up for Nixle Alerts
The City of Sierra Madre sends emergency notifications via Nixle Alerts, delivering trusted updates directly from the Sierra Madre Police Department.

• Text your ZIP CODE to 888777 for real-time emergency alerts.
• Register online to receive email and text notifications.

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Mudflow Mitigation Efforts

The City of Sierra Madre, in partnership with Los Angeles County, is actively working to reduce mudflow risks. Current efforts include:

• Strategic K-rail placement to divert mudflows.
• Debris removal from roadways and storm drains.
• Sandbag distribution to residents.

Need property-specific mudflow mitigation advice?
Call the LA County Mudflow Hotline at 1-800-933-0930.

City & County Response Efforts

Public Works Coordination:

• Daily meetings with LA County officials to assess key impact areas and coordinate response efforts.
• Storm drains and debris basins inspected and cleared as needed.
• Sierra Madre Dam debris basin cleared – 2,500 truckloads of debris removed.
• Over 500 feet of K-rail installed based on past fire and mudflow data.
• Thousands of sandbags distributed (pre-filled and empty).

Evacuation Planning & Safety Measures

If an evacuation is ordered, leave promptly.
Plan ahead – Have a go-bag ready with essential items:

• Important documents
• Medications
• Basic supplies

Check on neighbors and assist them in preparing.

Emergency Response Limitations

• Fire, Police, and Public Works crews will NOT enter areas experiencing active mudflows.
• If you choose to stay under an evacuation order, you must shelter in place until emergency crews can safely enter.

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Additional Resources

To help residents understand mudflow risks and prepare for potential hazards, the following resources are available:

Watershed Emergency Response Team (WERT) Report– Comprehensive assessment of post-fire hazards and debris flow potential.

County Phase Mudflow Forecast – Los Angeles County Public Works evacuation zones and at-risk areas.

Homeowner's Guide for Flood, Debris, and Erosion Control – Detailed guidance from LA County Public Works on protecting properties from flooding and debris flows.

Request Engineering Advice – Submit a request for property-specific engineering advice related to mudflow concerns.

Debris and Mudflow Potential Forecast - The debris and mudflow potential forecast is based upon a review of watershed conditions and weather forecasts from the National Weather Service and other weather predicting sources. It represents conditions within the watershed that could lead to debris and mudflow events. Debris and mudflows are highly unpredictable events.

To monitor debris and mudflow conditions in Sierra Madre, you can access live camera feeds provided by ALERTCalifornia, a program by the University of California, San Diego. They have installed several cameras in key areas to enhance situational awareness and public safety.

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