RFG 2018 Conference

landslide

Landslides in the northern Colorado Front Range caused by rainfall, September 11-13, 2013

During the second week of September 2013, nearly continuous rainfall caused widespread landslides and flooding in the northern Colorado Front Range. The combination of landslides and flooding was responsible for eight fatalities and caused extensive damage to buildings, highways, and infrastructure. Three fatalities were attributed to a fast moving type of landslide called debris flow. One fatality occurred in Jamestown, and two occurred in the community of Pinebrook Hills immediately west of the City of Boulder. All major canyon roads in the northern Front Range were periodically closed between September 11 and 13, 2013. Some canyon closures were caused by undercutting of roads by landslides and flooding, and some were caused by debris flows and rock slides that deposited material on road surfaces. Most of the canyon roads, with the exceptions of U.S. Highway 6 (Clear Creek Canyon), State Highway 46/Jefferson Co. Rd. 70 (Golden Gate Canyon), and Sunshine Canyon in Boulder County, remained closed at the end of September 2013. A review of historical records in Colorado indicates that this type of event, with widespread landslides and flooding occurring over a very large region, in such a short period of time, is rare.

Living with Unstable Ground

Most of us take the stability of the ground for granted. However, many ongoing natural processes and human activities, and occasionally complex combinations of both, displace the ground. Whether ground displacements are large and catastrophic or small and slow, their cumulative impact during the lifetimes of humans or civilizations may be large and destructive. Parts of every state in the United States are affected by these instabilities of the ground. As the demand for land grows and humans increasingly modify their environment, more and more people will be exposed to these instabilities and suffer the consequences. Living with Unstable Ground, the 10th publication in AGI's Environmental Awareness Series, is a practical guide and will increase your awareness and understanding of how you can build safely in areas with unstable ground and what society can do to reduce the impact of unstable ground.

Estimating the costs of landslide damage in the United States

Landslide damages are one of the most costly natural disasters in the United States. A recent estimate of the total annual cost of landslide damage is in excess of $1 billion {Schuster, 1978}. The damages can be significantly reduced, however, through the combined action of technical experts, government, and the public. Before they can be expected to take action, local governments need to have an appreciation of costs of damage in their areas of responsibility and of the reductions in losses that can be achieved.

Landslide Loss Estimation Pilot Project in Oregon

In Oregon, economic losses due to landslides for a typical year are estimated to be over $10 million. In years with heavy storms, such as 1996, losses can be an order of magnitude higher and exceed $100 million. Oregon is one of seven pilot states funded by the U.S. Geological Survey to estimate losses. The study results are intended to illustrate the need to shift USGS current priorities to include mitigating landslide risks. Assuming ongoing population increases and current land use and construction practices, losses are expected to increase. High losses are expected in the areas of additional development on vulnerable hillslopes, stream banks, ocean bluffs and other coastal areas.

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