Any first class city may, if in the judgment of its city council, the public health or welfare of its citizens will be promoted thereby, divert any unnavigable stream, flowing wholly or partly within the corporate limits, from its natural bed to an artificial channel or to another watercourse. The diversion may take place at any feasible or desirable point within or without the corporate limits, and the new channel may be created within or without or partly within and partly without the corporate limits. For the purpose of controlling and regulating the flow of such stream in its new channel, the city may, by the erecting of dams or other suitable means, raise the waters of any lake or lakes from which the stream may flow, or through which the new channel may flow, and control and regulate the discharge from such lake or lakes, and straighten, enlarge, and make such changes and improvements in the channels as may be necessary for such purposes. Such new channels may, where necessary, cross any highway or railway; in which case suitable bridges shall be provided.