Within the districts established by this chapter or amendments thereto, there exist certain uses, structures, and lots which were lawful before this chapter was enacted or amended but which do not conform to the provisions of this chapter or amendments thereto. These uses, structures, or lots are referred to as nonconformities. The regulations governing existing nonconforming uses, structures, and lots are set forth in this Part and are intended to provide a gradual remedy for the undesirable conditions resulting from such nonconformities. While such nonconformities are generally permitted to continue, these regulations are intended to restrict further investment in such nonconformities and to bring about their gradual reduction.