Effects and Costs of Landslides
Landslides cause damage to transportation routes, utilities, and buildings and create travel delays and other side effects. Fortunately, deaths and injuries due to landslides are rare in Pennsylvania. Almost all of the known deaths due to landslides have occurred when rockfalls or other slides along highways have involved vehicles. Storm induced debris flows are the only other type of landslide likely to cause death and injuries. As residential and recreational development increases on and near steep mountain slopes, the hazard from these rapid events will also increase. Most Pennsylvania landslides are moderate to slow moving and damage things rather than people.
One small landslide in 1990 that involved a broken petroleum pipeline is an extreme example of the costs of related damages. Spilled petroleum products entered a major river, causing city water systems to shut down. The identified costs of repair of this landslide damage, clean-up of the spill, technical investigations, legal and court costs and environmental fines were approximately $12 million. The incalculable costs include: lost productivity while people stayed at home because their businesses were closed or to care for children normally in schools that were closed due to lack of water supply, costs for the National Guard to deliver water to neighborhoods and costs to the pipeline company and its customers due to business loss for several months. Although this example is extreme, "associated damages" such as this occur with many landslides.
Most damages are less expensive, but significant. "Backyard" landslides, common in the Pittsburgh area, are usually repaired incompletely or not at all. Cost estimates of several hundred thousand dollars for stabilization and repair of a landslide affecting two or three properties are typical. With repair estimates exceeding the value of the properties, abandonment is a frequent "solution". Sometimes local governments assist with relocation costs or "buy out" homeowners. Insurance covers landslide damage only for some business situations.
The Pennsylvania Department of Transportation and large municipalities incur substantial costs due to landslide damage and to extra construction costs for new roads in known landslide-prone areas. One PA DOT estimate in 1991 showed an average of $10 million per year in landslide repair contracts across the state and a similar amount in mitigation costs for grading projects. A number of highway sites in Pennsylvania are in need of "permanent" repair at estimated costs of $300,000 to $2 million each.
A study done by The U. S. Geological Survey found that the total public and private costs of landsliding in Allegheny County averaged at least $4 million per year from 1970 to 1976. No more recent similar accounting is known.