The county planning commission may also prepare, with the approval of the county commission, as parts of the official master plan or otherwise, sets of regulations governing subdivisions of land in unincorporated areas, and amend or change same from time to time as herein provided, which regulations may provide for the proper location and width of streets, building lines, open spaces, safety, recreation, and for the avoidance of congestion of population, including minimum width and area of lots. Such regulations may also include the extent to which and the manner in which streets shall be graded and improved, and the extent to which water, sewer and other utility services shall be provided, to protect public health and general welfare. Such regulations may provide that in lieu of the immediate completion or installation of the work, the county planning commission may accept bond for the county commission in the amount and with surety bond, cash bond, cash deposit with the county treasurer, letter of credit, or certificate of deposit and conditions satisfactory to the county commission, providing for and securing to the county commission the actual construction of the improvements and utilities within a period specified by the county planning commission, and the county commission shall have power to enforce the bond, surety bond, cash bond, cash deposit with the county treasurer, letter of credit, or certificate of deposit by all proper remedies. The subdivision regulations shall be adopted, changed or amended, certified and filed as provided in section 64.815. The subdivision regulations shall be adopted, changed or amended only after a public hearing has been held thereon, public notice of which shall be given in the manner as provided for the hearing in section 64.815.