Emergency Management

Landslides & Debris Flow

Landslides are caused by disturbances in the natural stability of a slope. They can accompany heavy rains or follow droughts, earthquakes, or volcanic eruptions. Mudslides develop when water rapidly accumulates in the ground and results in a surge of water-saturated rock, earth, and debris. Mudslides usually start on steep slopes and can be activated by natural disasters. Areas where wildfires or human modification of the land have destroyed vegetation on slopes are particularly vulnerable to landslides during and after heavy rains.¹

Some areas are more likely to experience landslides or mudflows, including:

Areas where wildfires or human modification of the land have destroyed vegetation;
Areas where landslides have occurred before;
Steep slopes and areas at the bottom of slopes or canyons;
Slopes that have been altered for construction of buildings and roads;
Channels along a stream or river; and
Areas where surface runoff is directed.

Landslide/Mudflow Safety Tips

Before intense storms and rainfall:
- Assume that steep slopes / areas burned by wildfires are vulnerable to landslides and debris flows.
- Learn whether landslides / debris flows have occurred previously in your area.
- Contact local authorities about emergency and evacuation plans.
- Develop emergency and evacuation plans for your family and business.
- Develop an emergency communication plan in case family members are separated.
During intense storms and rainfall:
- Listen to the radio, watch TV and monitor social media for warnings about intense rainfall or for information / instructions from local officials.
- Be aware of any sudden increase or decrease in water level on a stream or creek that might indicate debris flow upstream.
- Look for tilted trees, telephone poles, fences, or walls, and for new holes or bare spots on hillsides.
- Listen for rumbling sounds that might indicate an approaching landslide or mudflow.
- Be alert when driving. Roads may become blocked or closed due to collapsed pavement or debris.
- If landslide or debris flow danger is imminent, quickly move away from the path of the slide. Getting out of the path of a debris flow is your best protection. Move to the nearest high ground in a direction away from the path.