It is unlawful to parade upon any street in the city without first notifying the chief of police and the city engineer, and obtaining a permit to do so from said chief of police. Such notification shall be made in writing and shall state the purpose of such parade, the place and hour of formation of the proposed line of march, and the names of the persons having charge or control of said parade. Such notifications shall be delivered to the chief of police and the city engineer 24 hours before such parade is to take place; provided, however, that this time limitation may be lessened or the notice entirely waived in the discretion of the chief of police for any unexpected occasion, or in case of a parade of visitors arriving in the city within less than the above-described period preceding the desired hour of parade; provided, further, the chief of police, with the approval of the city engineer, may direct such modifications of the place of formation and of the line of march and other details of any such parade as traffic conditions and public safety may require and with the approval or on the order of the mayor may forbid or stop any such parade whenever deemed necessary for the preservation of the public peace or safety. (1961 code § 11.24.040.)