If the Master Plan or the Official Map provides for the reservation of designated streets, public drainageways, flood control basins, parks or other public areas within the proposed development, before approving a site plan, the Planning Board may further require that such streets, drainageways, basins or areas be shown on the plan in locations and sizes suitable to their intended uses. The Planning Board may reserve the location and extent of such streets, drainageways, basins or areas shown on the plan for a period of one year after the approval of the final plan or within such further time as may be agreed to by the developer. Unless during such period or extension thereof the Borough shall have entered into a contract to purchase or instituted condemnation proceedings according to law for the fee or a lesser interest in the land comprising such streets, drainageways, basins or areas, the developer shall not be bound by such reservations shown on the plan and may proceed to use such land for private use in accordance with applicable development regulations. The provisions of this section shall not apply to the streets and roads, flood control basins or public drainageways necessitated by the land development and required for final approval.