421.12  Eminent domain.--An authority shall have the right to acquire by the exercise of the power of eminent domain any real property which it may deem necessary for its purposes under this chapter after the adoption by it of a resolution declaring that the acquisition of the real property described therein is necessary for such purposes. An authority may exercise the power of eminent domain in the manner provided in chapters 73 and 74. Property already devoted to a public use may be acquired in like manner, provided that no real property belonging to the city, the county, the state or any political subdivision thereof may be acquired without its consent.