Whenever specifically indicated on the zoning map by the use of symbols, figures or other suitable indication, setback lines of running streams or bodies of water are herewith established. Such setback lines shall mark that location closest to the stream or body of water at which any structure may be erected, regardless of other regulations in this or other ordinances regulating such setbacks, unless such other ordinances shall impose greater restrictions. This requirement shall not apply to structures necessary for access and safety such as bridges, culverts or protective walls and fences. Unless otherwise specified and indicated on the zoning maps, no structure shall be erected on land which is less than three feet above the normal or average level of any adjacent running stream, lake or body of water nor closer than 60 feet horizontally to such stream, lake or body of water, whichever conditions shall impose the greater requirements, such distance to be measured to the intersection of the finished grade with the structure at the lowest elevation of such grade.