(1) Until June 30, 1989, the log storage rents per acre shall be the average rents the log storage leases in effect on July 1, 1984, would have had under the formula for water-dependent leases as set out in RCW 79.105.240, except that the aquatic land values shall be thirty percent of the assessed value of the abutting upland parcels exclusive of improvements, if they are assessed. If the abutting upland parcel is not assessed, the nearest assessed upland parcel shall be used.

(2) On July 1, 1989, and every four years thereafter, the base log storage rents established under subsection (1) of this section shall be adjusted in proportion to the change in average water-dependent lease rates per acre since the date the log storage rates were last established under this section.

(3) The annual rent shall be adjusted by the inflation rate each year in which the rent is not determined under subsection (1) or (2) of this section.

(4) If the lease provides for seasonal use so that portions of the leased area are available for public use without charge part of the year, the annual rent may be discounted to reflect such public use in accordance with rules adopted by the board.