For the accomplishment of the purposes of this part, any city, incorporated village, township, or board of county road commissioners may acquire any interest in land necessary to any flood control, drainage, or beach erosion control project, or to preserve flood plains, by purchase, gift, exchange, condemnation, or otherwise. If an easement to preserve a flood plain is acquired, the acquiring agency, in any instrument conveying such right or in any eminent domain proceedings instituted therefor, may acquire the further right to use the land subject to the easement, or any part of the easement, for any other public purpose, but only to the extent that the other uses are specifically enumerated in the conveyance or eminent domain proceedings. The legislative body of any city, incorporated village, or township, or the board of county road commissioners of any county when directed by the county board of commissioners of the county, may institute and prosecute proceedings under the power of eminent domain in accordance with the laws of the state or any local charter relative to condemnation. Two or more adjoining cities, villages, or townships are authorized to maintain proceedings in accordance with the procedure prescribed by Act No. 81 of the Public Acts of 1925, being section 123.71 to 123.73 of the Michigan Compiled Laws. The purposes contemplated by this part are declared to be public purposes within the meaning of the constitution, state laws, and charters relative to the power of eminent domain.