Within the various districts established by the Zoning and Property Chapters or amendments that may be adopted, there exist structures and uses of land and structures which were lawful prior to the effective date of the ordinance from which said chapters derived but which would be prohibited under these chapters. It is the intent of this section to permit these nonconformities to continue until they are removed, but not to encourage their survival. Such uses are declared by this section to be incompatible with permitted uses in the districts involved. It is further the intent of this section that such nonconformities shall not be enlarged upon, expanded or extended.