(1) Special district special assessments shall be imposed only on real property within the district that uses or will use the special district's facilities or receives or will receive special benefits from the special district's operations and facilities. Both privately owned and publicly owned real property, including real property owned by the state, is subject to these special assessments. Mobile homes located on real property within a special district shall be considered an improvement to the real property for purposes of imposing special assessments.

(2) Special assessments imposed upon real property, other than improvements, shall be a function of the dollar value of benefit or use per acre and the assessment zone in which the real property is located. Special assessments imposed upon an improvement shall be a function of the dollar value of benefit or use assigned to the type or class of improvements and the assessment zone in which the improvement is located.

(3) Assessment zones shall be established in which each zone reflects a different relative ratio of benefit or use that the real property within such a zone receives, or will receive, from the special district's operations and facilities. That real property receiving the greatest benefits, or which uses the special district's facilities to the greatest extent, shall be placed into class No. 1 and assigned a value of one hundred percent; that real property receiving the next greatest benefits, or which uses the special district's facilities to the next greatest extent, shall be placed into class No. 2 and assigned a lower percentage value; and so on, extending to the class of least benefits or use. That real property receiving no benefits or use shall be designated "nonbenefit." If all real property in the special district is found to have the same relative ratio of benefit or use, a single assessment zone may be established.

(4) Any one or more of the following criteria shall be used in measuring the manifest degrees or ratios of benefit or use: (a) Proximity to the special district's facilities; (b) height above or below dikes and levees; (c) easier accessibility; (d) facility of drainage; (e) minimization of flood or inundation damage; (f) actual flood protection; (g) use of the special district's facilities; and (h) any other criteria established by the county under RCW 85.38.160 that measure manifest degrees of benefit or use from the special district's facilities and operations.

(5) Special assessments may be imposed to pay for the construction, repair, and maintenance of special district facilities and for special district operations. Administrative and operational costs of the special district shall be proportionally included in these special assessments.