The district, hereinafter designated as combining FF (flood fringe) district is established to be combined with other districts in certain areas which are uniquely susceptible to periodic inundation as determined by an engineering analysis of hydrological, meteorological, topographical, and other data. The regulations are intended to require that uses vulnerable to floods be protected against future flood damage at the time of initial construction. The regulations of any district with which an FF district is combined shall remain the same, except as to matters specified in Section 17.30.060, which shall apply in addition to those contained in the zoning district with which it is combined. (Prior gen. code § 8-44.7)