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What Landforms Do Mudslides Make?

If you are looking at the side of a hill that has recently experienced a mudslide, you might be curious about the resulting features. Landslides happen when a piece of earth shears off after a disruption like a heavy rain or an earthquake. Mudslides, technically called mudflows, are a type of landslide that occurs when soil becomes supersaturated with water and surges down the hill in a wave of rock and mud. There are landforms that are more prone to mudslides and other that are the aftermath of these dramatic events.

Landforms Where Mudflows Are More Likely
- In simplest terms, mudflows happen on hills, the steeper the more likely. Besides steep hills, you can look for other features if you are worried about mudflows. Portions of the hill that are concave, such as scars from previous mudflows, tend to collect water and are more prone to mudflows. Likewise, hills with an impermeable layer, a layer of rock or soil that water cannot pass through, collect water in the surface soil, making them saturated and unstable. Soil type, geology and vegetation cover are other risk factors that are independent of landforms.
The Main Scarp
- The scarp is the scar on the hillside that remains after the mudslide has occurred. The scarp is exposed soil and bedrock where the mudslide started. It is usually curved at the top, dropping precipitously into a cliff and then a concave piece of hillside. The scarp will eventually grow vegetation again, but it will maintain its characteristic shape and that area will always be less stable and prone to further mudslides.
Track of the Mudflow
- Between the scarp at the top of a mudflow and the toe at the bottom lies the track of the mudflow. Most have a characteristic hourglass shape, with a large scarp at the top, a narrow track and a wide toe. The track often follows the preexisting topography of the landscape, such as a ditch, gully or streambed, since the fine particles that make up the flow move in much the same manner as the water that formed the topography. Compared to other landslide types, the track of a mudflow is relatively elongated.
Toe of the Mudflow
- The toe of the mudflow is where the material from the side of the hill is deposited. It is a pile of debris where the slope of the hill abates enough that the mudflow slowed down and, finally, stopped. As the toe settles into place, the debris pile becomes the surface on which the rest of the hillside rests. Mudflows are more liquid than other forms of landslides, so the toe tends to be more diffuse and the transition from the slide scar to the toe tends to form a fan shape at the bottom of the flow.

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