Oak Forest Water Tank Slide: This is one of several landslides developed in Quaternary deposits and Tertiary to upper Cretaceous rocks on the eastern slopes of City Creek Canyon just north of Salt Lake City, UT. The landslide scarps form prominent scars on a steep northeast facing slope that are visible for miles. The slide is approximately 25 m wide at the head, 70 m wide at the toe, and 90 to 100 m long, with a topographic relief from toe to head scarp of roughly 70 m. The base of the slide is marked by a steep-sloped toe and a gully that is partly filled by landslide debris. The landslide presumably formed in the early 1980s, but has not been monitored in recent years.

We took aerial photographs of the landslide on June 1, 2007 using the Slow-stick aircraft with 3.2 Megapixel digital still camera. These images were compared with a USGS orthophoto of the landslide obtained in 2003. The images were processed to enhance exposed soil and vegetation before scarps and vegetation were mapped using an automated classification algorithm (see next page). The area of exposed soil decreased between 2003 and 2007 as grasses and shrubs spread, suggesting that the slide has stabilized. There was some new but minor slumping along the margins of the slide in the 2007 image, and downslope creep of several meters between 2003 and 2007 based on offset clumps of vegetation. The slide has probably stabilized in the last few years because of relatively dry climate with below normal precipitation.

LANDSLIDE MONITORING AND MAPPING BY UAV