Upon delineation of the floodway under the national flood insurance program [42 U.S.C.

4001 et seq.], uses shall be permitted within the floodway to the extent that they do not result in any increase in flood levels during the occurrence of the base flood discharge. Any exception to the national flood insurance program [42 U.S.C. § 4001 et seq.] in implementing regulations granted by the appropriate federal agency to a community participating in the national flood insurance program is an approved exception pursuant to this section.