Rural Roads:

Road Related Landslides

Landslides with the potential to fail during periods of intense and prolonged rainfall events are identified in the field by tension cracks, scarps showing vertical displacement, corrective regrowth on trees, and perched, hummocky fill indicating surface instability. Types of road related landslides typically include (1) road fill failures, (2) landing fill failures, (3) hillslope debris slides, and (4) deep-seated, slow landslides. The majority are often the result of failure of unstable fill and sidecast material from earlier road construction. Preemptive excavation of small, current or potential landslides is an effective technique for erosion control, achieved by removing the unstable material and redepositing it in a stable, designated location either at or near the treatment site.

Examples of Road-Related Landslides

In a forested area, a dirt road has partially slid into the deep ditch, leaving a ragged edge.

Road fill failure on stream-side road. (PWA)

On another forest road, an entire section of the fill slope has eroded into the stream.

Fill slope failures on roads built on steep slopes near stream channels have a high likelihood of delivering sediment directly to the stream channel. (PWA)

Examples of Unstable Fillslope Excavation

Example 1 Before and After:

A dirt road image is labelled, with a section of unstable fill (that looks uneven and convex) outlined and labelled.

The area of unstable fill has been re-graded. It looks even and concave all down the bank.

Example 2 Before and After:

Another unstable, convex road bank is shown.

This bank has been fixed by a re-grading. It now slopes gently and evenly away from the road.


What should I do about road related landslides?

  • Contact the Marin RCD: call, email, or use the submission form in the sidebar of this page.
  • Secure permits: This practice may sometimes require permits.

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How can I get help?

RCD staff can work with you to assess erosion sources, develop improvement plans, and oversee implementation. Cost-share for this service may be available or the RCD may perform work as "fee-for-service." Contact the RCD by submitting your information: