Tex. Gov't Code § 1505.207

As additional security for the encumbrance, a municipality that encumbers a harbor improvement or facility under Section 1505.203 may provide in the encumbrance for a grant, to a purchaser under sale or foreclosure, of a franchise to operate the harbor improvement or facility, including any improvement, for a term not to exceed 30 years from the date of purchase, subject to all laws regulating the same then in force.