(1) The assessors for the several counties and the board of assessment and equalization may adopt such units for assessment purposes as they deem practicable and advisable, such as the acre for rural lands; the lot for real estate in cities, towns, and villages; the plant and the land on which it is located for industrial properties; and the mile for railroads, tramroads, telegraph and telephone lines, electric high power lines, and rural electrification lines.
(2) They shall assess the properties in each class according to the special benefits which accrue by reason of levee protection to property of the character embraced in the particular class.