California Code, Government Code - GOV § 25680

(a) The construction of works, improvements, levees, or check dams to prevent the overflow and flooding of streams and rivers in the county.

(b) The protection and reforestation of the watersheds of such streams and rivers.

(c) The conservation of the flood waters of such streams and rivers.

(d) The making of all surveys, maps, and plats necessary to carry out any work, construction, or improvement authorized by this section.

(e) The carrying out of any work, construction, or improvement authorized by this section outside the county, if the rivers or streams flow in or through more than one county.