Whenever a county road improvement district is established for the safeguarding of open canals or ditches as authorized by RCW 36.88.015 the rate of assessment per square foot in the district may be determined by any one of the methods provided in chapter 35.44 RCW for similar improvements in cities or towns, and the land specially benefited by such improvements shall be the same as provided in chapter 35.43 RCW for similar improvements in cities or towns.