Wash. Rev. Code § 85.18.005
The state declares that it has an interest in protecting and preserving productive land and buildings needed to make business function continuously. Where organized diking districts, through their improvements, have reclaimed land or protected it from overflow and have enabled erection of improvements thereon or have furnished such land and buildings protection against flood water, it is necessary to provide a just and equitable method to enable such diking districts continuously to function effectively. It is declared that there is a direct relationship, where such conditions exist, between the continuous functioning of such districts and the fair value of the lands and buildings thereon, or to be erected thereon, thus afforded protection.
RCW 85.18.005