In the case of a planned development containing at least an aggregate of 100,000 square feet devoted to retail and/or recreational uses (including piers and platforms and excluding water area), parking may be provided in enclosed parking structures or open parking areas or in any combination thereof. Vehicles parked in open areas must be shielded or screened in such manner as substantially to prevent them from being observed from grade level outside the planned development. Such shielding may be provided by buildings, landscaping, fences or walls within the planned development.