The provisions of this chapter do not require any changes or improvements to be made to lawfully existing structures. However, when an improvement is made to any existing structure, the provisions of § 171-30 shall apply.
The following provisions shall apply whenever any improvement is made to an existing structure located within any identified floodplain area. No expansion or enlargement of an existing structure shall be allowed within any floodway area/district that would cause any increase in BFE.
A. 
No expansion or enlargement of an existing structure shall be allowed within AE area/district without floodway that would, together with all other existing and anticipated development, increase the BFE more than one foot at any point.
B. 
Any modification, alteration, reconstruction, or improvement of any kind to an existing structure to an extent or amount of 50% or more of its market value shall constitute a substantial improvement and shall be undertaken only in full compliance with the provisions of this chapter.
C. 
The above activity shall also address the requirements of the UCC.
D. 
Within any floodway area/district (see § 171-18A), no new construction or development shall be allowed, unless the appropriate permit is obtained from the DEP regional office.
E. 
Within any AE area/district without floodway (see § 171-18B), no new construction or development shall be located within the area measured 50 feet landward from the top-of-bank of any watercourse, unless the appropriate permit is obtained from the DEP regional office.
F. 
Any modification, alteration, reconstruction, or improvement of any kind to an existing structure, to an extent or amount of less than 50% of its market value, shall be elevated and/or floodproofed to the greatest extent possible.