Displacement and groundwater pressure data from the Carmel Knoll and Johnson Creek landslides, Oregon, USA

Coastal landslides such as the Carmel Knoll and Johnson Creek landslides located in Lincoln County, Oregon, reactivate during most winter rainy seasons when groundwater pressures are elevated. We collected landslide displacement and groundwater pressure head data at 15-minute to 60-minute intervals using solar- and battery-powered dataloggers at the aforementioned landslides to assist with studies of their reactivation and movement. Vibrating-wire piezometers that measured pressure head were installed by Oregon Department of Transportation (ODOT) during studies performed prior to our involvement. For Carmel Knoll, this data release provides displacement data from a cable extension transducer (extensometer) that we installed across the landslide headscarp, and pressure head data from near the landslide toe from a vibrating-wire piezometer located just above the landslide base at an elevation of 0.88 m above mean sea level, according to unpublished ODOT notes (eroding coastal bluff topography at the piezometer location rendered piezometer depth ambiguous; Schulz and others 2012; 2014). These data cover the period January 29, 2008 to June 19, 2014, with some omissions due to sensor and(or) datalogger problems. For Johnson Creek, displacement data provided herein were obtained near the landslide center from an extensometer affixed to a stainless steel cable previously installed in a borehole and anchored beneath the landslide (LT-1 inclinometer of Schulz and others, 2007, and Priest and others, 2011), and pressure head data from a piezometer located at a depth and elevation of 24.80 m and 0.38 m, respectively, about 1.4 m above the estimated landslide base (LT-1p of Priest and others, 2011). These data cover the period November 20, 2004 to March 12, 2014, with some omissions due to sensor and(or) datalogger problems. Both extensometers had manufacturer-stated ±0.7 mm accuracy, whereas both piezometers had manufacturer-stated ±0.345 kPa accuracy.

References
Priest, G.R., Schulz, W.H., Ellis, W.L., Allan, J.A., Niem, A.R., and Niem, W.A., 2011, Landslide stability: role of rainfall-induced, laterally propagating, pore-pressure waves: Environmental & Engineering Geoscience, v. XVII, no. 4, p. 315-335,  https://doi.org/10.2113/gseegeosci.17.4.315.
Schulz, W.H., and Ellis, W.L., 2007, Preliminary results of subsurface exploration and monitoring at the Johnson Creek landslide, Lincoln County, Oregon: U.S. Geological Survey Open-File Report 2007-1127, 11 p., 1 appendix, https://doi.org/10.3133/ofr20071127.
Schulz, W.H., Galloway, S.L., and Higgins, J.D., 2012, Evidence for earthquake triggering of large landslides in coastal Oregon, USA: Geomorphology, v. 141-142, p. 88-98, https://doi.org/10.1016/j.geomorph.2011.12.026.
Schulz, W.H. and Wang, G., 2014, Residual shear strength variability as a primary control on movement of landslides reactivated by earthquake-induced ground motion: Implications for coastal Oregon, USA: Journal of Geophysical Research, Earth Surface, v. 119, no. 7, p. 1617-1635, https://doi.org/10.1002/2014JF003088.


Acknowledgements
We thank David Kibler, Sarah Rickard (formerly Galloway), Joshua Thuele, Joel Smith, Bernard Kleutsch, Ed Duffy, Jeffrey Coe, George Priest, and Rex Baum for assistance with obtaining data presented herein.