Oregon Revised Statutes Revenue and Taxation § 308A.368

(1) When land that has been designated as exempt from taxation under ORS 308A.350 to 308A.383 as riparian is applied to some use other than that compatible with riparian use, as defined in the management plan, except through compliance with ORS 308A.365 (2), or except as a result of the exercise of the power of eminent domain, the owner shall within 60 days after the change in use notify the county assessor of the change in use. The assessor or assessors shall withdraw the land from designation and immediately give written notice of the withdrawal to the State Department of Fish and Wildlife. Thereafter, the land shall be assessed and taxed as other property similarly situated is assessed and taxed.

(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applicable to the property after its most recent change of ownership) preceding the tax year in which the land was withdrawn from designation.