It is declared that the preliminary work, establishment and completion of a drainage district shall be classified as a public improvement of an integral part of the county in which such district or part thereof be located, and it shall be the duty of the governing body of each county to cooperate in the promotion of the development of each of such parts of their county, including the construction of public roads, public bridges and the drainage canals of preliminary or finally established drainage districts, and the indirect benefits received by the development of each of the parts of a county are indeed substantial benefits received also by the county, and the value of the indirect benefits received by the county is full compensation for the performance of the duty assigned to the governing body of any county by this chapter, and that the preliminary payment of costs and expenses of surveys of drainage districts, and the assumption or responsibility for necessary bond issues required for established drainage districts, public bridges and public roads shall be construed as revenue producing investments for the county, from which increased revenues will be derived from increased assessments by reason of the improvements and the preliminary payment of the costs and expenses and the assumption of the responsibility by the governing body of a county, shall be considered the performance of a duty towards the several integral parts of their county, for which the county receives full potential value.
Va. Code § 21-294