(a) An individual, corporation, or association authorized to act by this chapter may acquire by purchase or by the exercise of the right of eminent domain any approach the individual, corporation, or association considers necessary for a structure.
(b) Subject to Chapter 51, Natural Resources Code, the state grants to an individual, corporation, or association acting as authorized by this chapter 500 feet on each side of the structure with the right only to dredge from that area or beyond for material required to construct or maintain the causeway.