(1) Only improvements authorized in writing by the department or consistent with the approved plan of development may be placed on the state lands under lease. Improvements are subject to the following conditions:
(a) A minimum reasonable time must be allowed for completion of the improvements;
(b) Improvements become the property of the state at the expiration or termination of the lease unless otherwise agreed upon under the terms of the lease; and
(c) The department may require improvements to be removed at the end of the lease term at the lessee's expense.
(2) Any improvements placed upon any state lands without the written authority of the department become the property of the state and are considered part of the land, unless required to be removed by the lessee under subsection (1)(c) of this section.