The governing body of any city and the board of county commissioners of the county in which such city is located may provide for a system of storm drainage in any natural drainage area located within the corporate limits of the city and the adjacent unincorporated area of the county. The governing body of the city and the board of county commissioners of the county may by joint resolution create a joint storm drainage district and provide for the construction of, and maintenance of main and lateral storm water drains therein. Such joint resolution shall provide for the method of assessment to be utilized in assessing the cost of improvements against the property within the district and the portion, if any, of the cost to be borne by the city at large. Final engineering plans for any proposed improvement shall be approved by both the governing body of the city and the board of county commissioners of the county. Improvement projects within such district, including that portion lying outside the city, shall be administered by the city and shall be initiated, authorized, and financed by the issuance of bonds and the levying of special assessments in the manner provided for the initiation, authorization and financing of improvements under the provisions of article 6a of chapter 12 of the Kansas Statutes Annotated, and amendments thereto, and on the basis of any reasonable assessment plan which considers land use and which will result in imposing substantially equal burdens upon property similarly benefited, and in accordance with the provisions of the joint resolution. Moneys received from special assessments levied against property located outside the corporate limits of the city shall be paid to the city for the retirement of bonds issued by the city for payment of the cost of improvements within such district for which such assessments were levied.