Section 965 Of Chapter 2. Powers And Duties Of Boards Of Supervisors From California Streets And Highways Code >> Division 2. >> Chapter 2.

. The board of supervisors shall, by order, direct the district attorney of the county to institute eminent domain proceedings, in the name of the county, whenever it is necessary to acquire real property or any interest therein to do any of the following things for the protection of a county highway:
  (a) Raise the banks along any stream.
  (b) Remove obstructions from any stream.
  (c) Widen, change, deepen or straighten the channel of any stream.
  (d) Construct flumes, ditches or canals, or make any improvements for the purpose of carrying off storm waters or floods.