Adjacent to single-family, single-family detached or duplex residential use, no portion of the structure shall be closer to a single-family, single-family detached or duplex residential property line than the height of that portion, except that the minimum setback stated in subsection 3 shall apply. However, when the residential use property line abuts an alley or street right-of-way, the city aqueduct, or a body of water such as Sikes Lake or Wichita River, the additional setback shall be computed by including their width.