California Code, Water Code - WAT § 12579

It is hereby declared that recurrent floods on streams and rivers, and other waterways of the State, causing loss of life and property, disruption of commerce, interruption of transportation and communications, and wasting of water, are detrimental to the peace, health, safety, and welfare of the people of the State. The control, storage and full beneficial use of flood waters, and the prevention of damage by flood waters, and the washing away of river and stream banks by floods are proper functions and activities of the State, in cooperation with counties, cities, state agencies and public districts, and in cooperation with the United States, or any of its departments or agencies.