For purposes of sections 25-230 to 25-238, inclusive: (1) Any structure or related facility, including, but not limited to, a parking lot, septic system or pool or railroad right-of-way; (2) any surfaced area, including, but not limited to, a paved, bricked or graveled walk or driveway; (3) a lawn or other landscaped area which exists on the date the commissioner approves an applicable river corridor management plan; (4) a waste discharge, authorized under chapter 446k, which exists within a river corridor on the date the commissioner approves an applicable river corridor management plan; (5) a water supply diversion within a river corridor which diversion is authorized under chapter 446i on the date the commissioner approves the applicable river corridor management plan; or (6) agricultural land, identified by the Commissioner of Agriculture in the inventory provided to the river commission pursuant to section 25-234, which is in use on such date, including land reserved for crop rotation, may be maintained as such and, if on or after the date of approval of a river corridor management plan any such structure, related facility, surfaced or landscaped area or agricultural land is degraded, damaged or destroyed, it may be replaced or restored without regard to the provisions of sections 25-230 to 25-238, inclusive, and subsection (a) of section 13a-94, provided there is no significant change in its location, dimensions or elevations and provided further that nothing in sections 25-230 to 25-238, inclusive, shall preclude the performance of routine maintenance or repair activities for such structures, related facilities, surfaced areas, lawn or landscaped areas or agricultural land. Any waste discharge authorized under chapter 446k, which exists within a river corridor on the date of approval of a river corridor management plan or a water supply diversion within a river corridor which diversion is authorized under chapter 446i on the date the commissioner approves the applicable river corridor management plan may be reauthorized under said chapter 446k or 446i without regard to the provisions of sections 25-230 to 25-238, inclusive, and subsection (a) of section 13a-94. Land reserved for crop rotation shall not include “forest land”, as defined in section 12-107b.