Reducing debris flow hazards during an El Niño winter

Protection from debris-flows and the damage they cause

The disastrous consequences of this combination of floods, debris flows, and landslides in the past (particularly during El Niño years) have led to mitigation efforts:

• Starting in the 1930's, constructing systems of protective works, including debris basins and flood control channels. [Photo of debris basin]
• Chiefly in the 1960's and 1970's, revising building codes that require special design measures and construction methods to protect homes and other structures from potential landslide (including debris flow) hazards.

These efforts have proven effective in greatly reducing economic losses and personal injuries. However, they are not capable of protecting every resident in every southern California location. An obvious example would be those structures built before the code provisions were established.

Questions to ask

• Is my home located in the paths of potential debris-flows?
• Are protective engineering works, such as debris basins, lined channels, flow deflection walls, drainage interceptors, or other structures uphill or upstream from my home?
• Are engineered structures modern or do they need maintenance to make them more effective?
• If my home is in a vulnerable location, what can I do to minimize the risk of damage and injury?

In addition to working with the emergency preparedness and response agencies that serve their localities, hillside and canyon residents can prepare for and defend against debris flow hazards to some extent. Some basic information about the form and character of the terrain around their homes, about the common characteristics of debris flows and floods, and about the kinds of rainstorms associated with past debris-flow events, point the way to some "common sense" measures that could be considered by residents.

Los Angeles County personal preparedness site

How to prepare for debris flows.

What are debris flows?

Photographs of landslides and debris flows in Southern California.

LINKS: El Niño pages for Southern California

For further information, contact David Miller

http://geology.wr.usgs.gov/wgmt/elnino/scampen/reducing.html, 29 December 1997, Contact: El Niño Web Team