Geology Expert On Stability Of Slopes Part 2

Shallow Failures

Shallow or surficial failures are the most common type and are commonly called mudflow or erosion failures. Shallow failures occur when the upper few feet of fill or “colluvial” soil on a slope becomes saturated; that is, the internal pore spaces within the soil are filled with water. This weakens the internal strength of the soil and may cause the soil to behave more like a liquid than a solid causing the soil to “flow”. Most commonly, these types of failures occur on steep slopes, slopes that have sparse vegetation, or in areas that have a concentrated flow of water.

Downhill homeowners tend to bear the brunt of these failures when the soil and debris flow onto their properties and often into their homes resulting in substantial property loss and potential injury. These failures can be caused by triggering events such as broken pipes, poor drainage from upper properties, and from construction defects such as slopes that were built too steeply or inoperative or poorly maintained drain lines.