It is hereby declared the public policy of the State of North Carolina to encourage development of such river and harbor, flood control and other similar civil works projects as will accrue to the general or special benefit of any county or municipality of North Carolina or to any region of the State. To this end, it is also hereby declared that within the meaning of the North Carolina Constitution expenditures for such projects and obligations incurred for such projects are for public purposes, that county and municipal and other? local government expenditures and obligations incurred therefor are necessary expenses, and that county expenditures therefor are for special purposes for which the special approval of the General Assembly is hereby given. (1969, cc. 724, 968.)