Wyoming: Landslide Warning

US Forest Service

Campbell Scientific dataloggers at the heart of a landslide warning system

Loss of life from large landslides, such as those in Oso, Washington, and West Salt Creek, Colorado, has increased awareness of landslide hazards among public-land managers in the western United States. About 20 years ago, a large landslide occurred adjacent to Cook Lake in the Bear Lodge Mountains in northeastern Wyoming. As a result, RESPEC was contracted by the US Forest Service (USFS) to design an early-warning system to protect recreational users and a downstream community from potential disaster in that region of Wyoming.

In 1997, after several years of record rainfall, soil saturation caused a large, 27-acre landslide to occur overnight in the mudstone strata of the Jurassic Sundance and Redwater Formations. A near-vertical, 15-meter head scarp was formed along with a large muddy toe from the extrusion of fluidized clay that displaced the western shoreline of the 31-acre lake. A 19-unit campground and popular hiking trail were evacuated and closed. The lake’s dam was threatened with failure from overtopping, which could have led to downstream flooding and loss of life. The landslide remains active today with numerous occurrences of audible tree cracks, visible rockfall, tension cracks, and a fluctuating shoreline.

In fall 2016, RESPEC drilled two deep boreholes to investigate the landslide-failure plane. Downhole piezometers, time-domain reflectometer (TDR) cables, and inclinometers were installed and integrated with Campbell CR6 and CR300 dataloggers. Data are transmitted to a base station equipped with a CR300-RF407 datalogger with radio. Data are then relayed to a repeater station 13 miles away, also equipped with a CR300-RF407, and then sent by cellular modem to a RESPEC server. . Additional tiltmeters and rain gauges were installed along the landslide periphery to detect shallow landslide movement and provide local precipitation data. Single tiltmeters were integrated with CR300-RF407 dataloggers that also transmit data to the base station. Data are compiled with the eagle.io web browser, which provides a real-time data interface and early-warning alarms to the USFS staff. Recently RESPEC installed an additional site to provide onsite warning using audible and visual signals if monitored parameters exceed values determined to indicate additional landslide activity.

Since the implementation of the system, the USFS has been able to reopen the campground and lake for recreational purposes.