Buffer screen. A dense evergreen screening hedge at least 10 feet in height as approved by the Planning Board shall be installed along the property line of any R-7 multifamily development abutting any R-1, R-2 or R-3 Residential Zone. Said screening hedge shall be used as a buffer to physically screen the multifamily from the one- and two-family areas. The buffer screen may be waived or modified by the Planning Board, in whole or in part, if the Planning Board concludes that because of topographical or site conditions the same shall not be necessary to protect the abutting or facing premises located in any abutting residential zone.