Upon submission of as-built construction plans, the applicant shall be provided a notice of final approval in writing if, in the executive director's opinion, no significant variance from the approved plans occurs during the course of construction. Thereafter, any enlargement or other modification of the project, including any subsequent rehabilitation or reconstruction of the project in a manner differing in any way from the approved project plans must be submitted to the commission for approval as a new levee or other improvement pursuant to this chapter.