Road Related Landslides

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)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

A forest path with lush greenery, ferns, and rocks, alongside a small stream. A few people walk in the distance on the trail.
Road fill failure on stream-side road. (PWA)
A road has eroded significantly, creating a steep drop-off, with lush greenery surrounding the area and a vehicle nearby.
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:

The image shows a dirt path with "unstable fill" noted along a sloped area, indicating potential ground instability.
A person stands near a concave excavation surface along a dirt road, with vegetation and a vehicle in the background.

Example 2 Before and After:

The image shows a hilly terrain with dry grass, scattered branches, and a person with a dog in the background.
The image shows a hillside covered with straw, debris, and fallen tree branches, surrounded by forest.

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.