Tex. Local Government Code § 216.008

(a) For an off-premise sign that is required to be removed, the compensable cost is an amount computed by determining the average annual gross revenue received by the owner from the sign during the two years preceding September 1, 1985, or the two years preceding the month in which the removal date of the sign occurs, whichever is less, and by multiplying that amount by three. If the sign has not been in existence for all of either two-year period, the average annual gross revenue for that period, for the purpose of this computation, is an amount computed by dividing 12 by the number of months that the sign has been in existence, and multiplying that result by the total amount of the gross revenue received for the period that the sign has been in existence. However, if the sign did not generate revenue for at least one month preceding September 1, 1985, this computation of compensable costs is to be made using only the average annual gross revenue received during the two years preceding the month in which the removal date of the sign occurs, and by multiplying that amount by three. In determining the amounts under this paragraph, a sign is treated as if it were in existence for the entire month if it was in existence for more than 15 days of the month and is treated as if it were not in existence for any part of the month if it was in existence for 15 or fewer days of the month.

(b) The owner of the real property on which the sign was located is entitled to be compensated for any decrease in the value of the real property. The compensable cost is to be determined by the board according to standards applicable in a proceeding under Chapter 21, Property Code.