Flood plain regulations adopted pursuant to Section 8412 shall take effect 60 days from the date of adoption by the public agency and shall be deemed to meet the requirements of Section 8411 unless the department or board determines that such flood plain regulations are not adequate to comply with the requirements of Section 8411. If the department or board makes such a determination, it shall so report to the public agency and shall recommend such regulations or modifications of the regulations of the agency, which it determines are necessary.