The Department shall: Develop a comprehensive management plan for the use of vessels on the Severn River and its tributaries in accordance with the Administrative Procedure Act under Title 10 of the State Government Article; and Implement the comprehensive management plan no later than April 15, 1990. The comprehensive management plan for the use of vessels on the Severn River and its tributaries shall include, but not necessarily be limited to: Areas designated for specified uses; Noise level limits of vessels; Maximum speed limits of vessels; Other limits that address water surface capacity and the safe operation of vessels so as to maximize the recreational and aesthetic values of the Severn River and its tributaries, consistent with sound environmental practices; and A study of seaplane activity on the Severn River and its tributaries. This section may not be construed to change the authority previously granted to the Department to adopt regulations concerning the subject matter of this section.