Section 503.2, Flood hazard areas, is hereby deleted in its entirety and the following provision shall be substituted therefor:

For buildings and structures in flood hazard areas established in Section 1612.3 of the International Building Code, or Section R322 of the International Residential Code, as applicable, any alteration that constitutes substantial improvement of the existing structure shall comply with the requirements provided in the TMC Chapters 14.20 (building code) and 17.30 (floodplain management). Alterations to buildings and structures in such flood hazard areas that do not constitute substantial improvement are not required to comply to meet the requirements provided in the TMC Chapters 14.20 (building code) and 17.30 (floodplain management).