Terrestrial LIDAR Investigation of the December 2003 and January 2007 Activations of the Northridge Bluff Landslide, Daly City, California

On December 20, 2003 and again on January 1, 2007, landslides occurred along
the coastal bluff that forms the west boundary of Daly City, California sending
debris as far as 290 meters downhill and 90 meters into the ocean. This area is
known for large landslide events where 150-meter tall coastal bluffs extend
southward along the west boundary of San Francisco and San Mateo Counties (Fig.
1). The 2003 and 2007 landslide events occurred west of Northridge Drive in
Daly City and just south of Avalon Canyon, which bisects the bluffs in this
area (Fig. 2). Residential development, utility lines and roads occupy the land
immediately east of this location. As part of a comprehensive project to
investigate the failure mechanisms of coastal bluff landslides in weakly
lithified sediments along the west coast of the United States, members of the
U.S. Geologic Survey (USGS) Coastal and Marine Geology (CMG) Program performed
reconnaissance mapping of these landslide events including collection of
high-resolution topographic data using CMG's terrestrial LIDAR laser scanning
system.

The report provides a brief background on each landslide event and presents
topographic datasets collected following each event. Downloadable contour data,
images, and FGDC-compliant metadata of the surfaces generated from the LIDAR
data are also provided. LIDAR data collection and processing techniques used to
generate the datasets are outlined. Geometric and volumetric measurements are
also presented along with high-resolution cross-sections through various areas
of the slide masses and discussion concerning the slides present (2007)
configuration is provided.

[Summary provided by the USGS.]