Comment on “Piezometric response in shallow bedrock at CB1: Implications for runoff generation and landsliding” by David R. Montgomery, William E. Dietrich, and John T. Heffner

Piezometric responses to rainfall on hillslopes commonly dictate the timing of landsliding. Insight to this phenomenon can be gained by evaluating the timescales for pore pressure perturbations to propagate normal and parallel to the ground surface, and these timescales can be estimated using characteristic values of hydraulic diffusivity [Iverson, 2000]. However, Montgomery et al. [2002] employed an erroneous definition of hydraulic diffusivity, leading to flawed assessment of the piezometric response timescales identified by Iverson [2000]. This comment aims to rectify the errors of Montgomery et al. [2002] and clarify the methods used by Iverson [2000] to estimate piezometric response timescales at the CB1 field site studied by Montgomery et al.