When authorized by appropriate laws passed by the legislature, the state of Alabama may, in promoting and aiding the commercial flow of agricultural products within the state or in aid of commerce and use of the waterways of the state, at a cost not exceeding $10,000,000, engage in works of internal improvement by promoting, developing, constructing, maintaining and operating within the state or along navigable streams and waterways now or hereafter existing within the state all manner of elevators, facilities, warehouses, docks, water and rail terminals and other structures and facilities and improvements needful for the convenient use of the same; provided that any such works or improvements shall always be and remain under the management and control of the state through the Alabama state docks department or other state governing agency and shall become part of the inland waterways facilities of the state. When authorized by appropriate laws passed by the legislature, the state may, in addition to all other bonds of the state, become indebted in an aggregate principal amount of not exceeding $10,000,000 for the purpose of carrying out the provisions of this amendment and may cause to be issued its general direct obligation bonds for the repayment of such indebtedness and interest thereon and pledge the faith and credit of the state thereto.