No provision of this Act shall be construed as limiting or impairing the powers and rights heretofore granted to any board of park commissioners, now existing, where such board of park commissioners have control of a park or parks within the limits of cities having a population of 200,000 or over, and where such park commissioners are appointed by the Governor of the State of Illinois, or by judges of the Circuit Court of the county in which such park district is located. Provided, however, that before any new work is done by any such board of park commissioners affecting submerged lands in navigable waters of the State of Illinois the plans for all such work shall be submitted to the Department of Natural Resources for approval before said work is undertaken.