Locational and Morphometric Characteristics of Landslide Deposits, Canyonlands National Park, Utah

Morphology and site characteristics of 512 landslide deposits were examined by means of a geologic/topographic map of Canyonlands National Park in an attempt to explain variations in deposit size and location. Eighty-nine percent of the landslide deposits mapped are associated with the Wingate Sandstone. Length of deposits was best explained by position beneath a scarp convexity (headland) or concavity (embayment), slope angle beneath the cliff, and cliff aspect. A t-test confirmed the importance of scarp geometry: headlands have the higher number of deposits beneath them, but landslide deposits beneath embayments are significantly longer and somewhat larger in area, suggesting that the degree of jointing in the sandstone is important. Variables representing stability factors associated with bedrock dip angle and direction relative to the cliff face did not explain a significant amount of variance. Angles of dip are apparently insufficient to contribute to instability, and a general lack of hydraulic throughflow largely eliminates sapping failure. The low explanatory power of the regression model (R2 = 0.124) can be explained by inaccuracies associated with using a 1 :62,500 scale map as the source of data, and an absence of field data on such possibly important variables as cliff height and degree of jointing. This study does, however, illustrate the importance of scarp geometry and aspect, as well as the absence of sapping, in the failure of Wingate Sandstone.