No residential structure shall hereafter be constructed or substantially improved (see Uniform Building Code Section 104(b)) unless the lowest habitable floor (as defined for flood hazard area administration) including habitable basement is elevated above the base flood elevation. Nonhabitable attached garages and storage spaces may be constructed below the base flood elevation.  Unhabitable accessory structures may be constructed below the base flood elevation if designed to withstand the fluid forces and effects of buoyancy to the base flood elevation.  (Ord. S-36983, 1978).