In this subchapter, "net revenue" means the gross revenue derived from the operation of a port improvement or facility the net revenue of which is pledged to the payment of an obligation less:
(1) the reasonable expenses of maintaining and operating the port improvement or facility, including necessary repair, maintenance, and insurance of the port improvement or facility; and
(2) if the municipality pledging the net revenue is a home-rule municipality, any annual payment of the municipality provided for in the charter.