California Code, Streets and Highways Code - SHC § 5105

(a) Whenever, in the opinion of the legislative body, the public interest or convenience may require, the legislative body may undertake any work necessary or incidental to the prevention, mitigation, abatement, or control of a geologic hazard or to repair damages resulting therefrom.

(b) For purposes of this division, “geologic hazard” means an actual or threatened landslide, land subsidence, soil erosion, earthquake, or any natural or unnatural movement of land or earth.

(c) Such work may be performed on private property with the prior written consent of the owner thereof, if the legislative body, in the resolution of intention, determines that it is in the public interest to do so.