EPISODIC MOVEMENT OF A SUBURBAN SLUMP

The Mile High Drive Landslide, located in a mountain-front residential neighborhood of Provo, Utah, is an active slump that has been monitored by Utah Valley State College Department of Earth Science students and faculty since 2003. The slide, approximately 150 by 300m in area, has damaged several homes, streets, and possibly a ground water level monitoring well. One house has been condemned and demolished and several homes are experiencing significant slide damage. The long term goals of this work include correlating slide movement with climate and ground water level to gain a predictive knowledge of conditions that lead to slope failure. Slide movement is monitored several times a year with RTK GPS phase-differential survey equipment to locate marker positions on the slide relative to an exposed bedrock reference point to a precision of ±1.5cm. Total slide movement is approximately 27 cm since UVSC began acquiring GPS data in 2003. Movement has been episodic. No movement was detected from 2003 to September 2004, followed by 14.1 cm of apparent creep between September 2004 and September 2005 and 9.6 cm between March 2006 and June 2006. Periods of accelerated movement correlate with wet years as recorded by annual precipitation records for Provo. Precipitation for the 04-05 water year (10/1/04 to 9/30/05) was 65 cm, compared to the 25-year average of 51 cm. Precipitation for the 05-06 water year was 2.5 cm below average. This suggests that slide movement occurs mostly during late spring following wet winters. Continued movement in 2006, during an average precipitation year suggests multi-year influences on the water table may be important. Future work will include monitoring movement of the slide toe and ground water level to gain a more complete picture of slide movement.