REPORT A LANDSLIDE
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WHAT IS A LANDSLIDE?

The term "landslide" describes a wide variety of processes that result in the downward and outward movement of slope-forming materials including rock, soil, artificial fill, or a combination of these. The materials may move by falling, toppling, sliding, spreading, or flowing. Many factors contribute to slope failure, but all can be categorized as affecting two components: the shear strength and the shear stress. The shear strength is the sum of all forces acting to keep the mass in place; the shear stress is the sum of all forces acting to move the mass.

When shear stress exceeds shear strength, a landslide occurs. Surficial geology, in combination with local hydrogeology, is the major determining factor in landslide propagation. Landslides are most likely to occur in fine grained, low porosity, low permeability units (i.e. silts and clays). The glacial and deglacial history of New York State is such that large areas of the landscape are underlain by marine or lacustrine silts and clays, which when saturated have a high susceptibility for failure.

Landslides in the United States cause approximately $3.5 billion (year 2001 dollars) in damage, and between 25 and 50 fatalities annually.

LANDSLIDES IN NEW YORK STATE:

1. Keene Valley, 2011
82 acres, rotational earth-slide

2. North Shore, Long Island, 1904
75 acres, rotatinal earth-slide

3. Tully Valley, 2001
53 acres, rotational earth-flow

NY State Emergency Management Office
NY State Landslide Hazard Profile [PDF 2MB]

USGS Landslides Page
http://landslides.usgs.gov/

Tully Valley Study
USGS: http://pubs.usgs.gov/of/1994/ofr-94-0615/tvstudy.htm
USGS: http://pubs.usgs.gov/fs/fs13-98/
Science Direct: Geomorphic studies of landslides in the Tully Valley, NY

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    REPORT A LANDSLIDE
    » Download Report Form (pdf 180kb)