The board of any county may establish county roads over, across or along any dike maintained by any diking, or diking and drainage, district in the manner provided by law for establishing county roads over or across private property, and shall determine and offer the amount of damages, if any, to the district and to the owners of the land upon which the dike is constructed and maintained: PROVIDED, That every such county road must be so constructed, maintained, and used as not to impair the use of the dike.