(2) The assessor, upon discovery of the change in use to a use other than that compatible with riparian or upon withdrawal by the owner of the land from designation, shall compute an additional tax equal to the difference between the taxes assessed against the land and the taxes that otherwise would have been assessed against the land had the land not received exemption for each of the last five years (or such lesser number of years, corresponding to the number of years of exemption under ORS 308A.350 to 308A.383 applicable to the property after its most recent change of ownership) preceding the tax year in which the land was withdrawn from designation. [Formerly 308.798]