If a county, soil and water conservation district, subdistrict of a soil and water conservation district, political subdivision of the state, or other local agency engages or participates in a project for flood or erosion control, flood prevention, or the conservation, development, utilization, and disposal of water, in cooperation with the federal government, or a department or agency of the federal government, the counties in which the project is carried on may, through the board of supervisors, construct, operate, and maintain the project on lands under the control or jurisdiction of the county dedicated to county use, or furnish financial and other assistance in connection with the projects. Flood, soil erosion control, and watershed improvement projects are presumed to be for the protection of the tax base of the county, for the protection of public roads and lands, and for the protection of the public health, sanitation, safety, and general welfare.