(a) Class I projects, as defined by section 871.1 of this Title, shall be subject to review and approval by the commission.

(b) Class II projects, as defined by section 871.2 of this Title, shall be subject to review and approval by a duly empowered State or local agency; and if there be no such State or local agency, at any time on and after January 1, 1978, and only during such time, the commission may review any such project which has been identified by the executive director as having special flood hazards; and