Cal. Wat. Code § 8414
If a public agency fails to adopt flood plain regulations pursuant to Section 8411, or fails to adopt new flood plain regulations within 180 days of receipt of the department's or board's notice pursuant to Section 8412, or fails to adopt or modify such regulations in the manner determined as necessary by the department or board pursuant to Section 8413 within 90 days of receipt of the department's or board's notice pursuant to Section 8413, the local flood control agency having jurisdiction over the project area may adopt flood plain regulations for the designated floodway necessary to comply with the requirements of Section 8411. Such flood plain regulations adopted by the local flood control agency shall take effect 30 days from the date of their adoption and shall be enforced by the public agency and have the same force and effect as if adopted as flood plain regulations by the public agency.
Ca. Water Code § 8414