OF-87-02 Preliminary Investigation of the Telluride Airport Debris Flow of April 30, 1987, San Miguel County, Colorado


Preliminary investigation of the Telluride Airport Debris Flow of April 30, 1987, in San Miguel County includes maps, cross-sections, and observations on the mechanics and occurrence immediately following the event. 18 pages. 6 figures. 1 plate (1:600). Digital PDF download. OF-87-02D

From the Introduction:
Starting at approximately 8:30 p.m. on April 30, 1987, a series of landslides occurred on the upper edge of Deep Creek Mesa, 4.5 miles west of Telluride, Colorado. The landslides initiated in a bowl-shaped depression that had been partially filled with engineered materials in order to build the runway for the Telluride Airport. As the landslides moved over the edge of the mesa and through a narrow notch in the sandstone rim, they mobilized into debris flows. The debris flows then traveled downslope, crossed State Highway 145, and stopped in the San Miguel River Valley. Up to 12 feet of material was left on the highway and the Animas Aggregate buildings and equipment on the valley floor sustained extensive damage.

In this report, we describe our observations from a 4-day (5/4/87 to 5/7/87) field investigation of the landslide and the subsequent debris-flow events. The report includes a description of the geologic and geomorphic settings, a compilation of eye-witness accounts of the events, and our description of the landslide scar, debris-flow path, and runout zone. The emergency advice and assistance provided by the CGS to local authorities immediately following the event is described, as well as our assessment of any remaining immediate hazard. We also suggest a possible sequence of failure in the scar area.