Ala. Code § 11-60-11
The principal of and interest on any bonds issued by the corporation shall be secured by a pledge of the revenues and receipts out of which the same shall be made payable and may be secured by mortgage or deed of trust covering all or any part of the projects from which the revenues or receipts so pledged may be derived, including any enlargements of and additions to any such projects thereafter made.
The resolution under which the bonds are authorized to be issued and any such mortgage or deed of trust may contain any agreements and provisions respecting the maintenance of the projects covered thereby, the fixing and collection of fees, rates, tolls and charges for the services, facilities and accommodations furnished by the corporation and of the rents for any portions thereof leased by the corporation to others, the creation and maintenance of special funds from such revenues and the rights and remedies available in the event of default as the board of directors shall deem advisable not in conflict with the provisions of this chapter. Each pledge, agreement, mortgage and deed of trust made for the benefit or security of any of the bonds of the corporation shall continue effective until the principal of and interest on the bonds for the benefit of which the same were made shall have been fully paid.
In the event of default in such payment or in any agreements of the corporation made as a part of the contract under which the bonds were issued, whether contained in the proceedings authorizing the bonds or in any mortgage and deed of trust executed as security therefor, such payment or agreement may be enforced by mandamus, the appointment of a receiver or by foreclosure of any such mortgage and deed of trust or any one or more of said remedies.
Ala. Code § 11-60-11 (1975)