; and (ii) consider the use of both traditional and natural infrastructure alternatives, alone or in conjunction with each other, if those alternatives are practicable. (6) Flood risk mitigation (A) Requirements Subject to subparagraph (B), the Secretary shall require that any structure that is located in an area having special flood hazards and that is newly constructed or is undergoing rehabilitation for substantial damage, for which substantial damage is repaired, or that is substantially improved, using amounts made available under this section, shall be elevated with the lowest floor, including the basement, at the higher of— (i) 2 feet above the base flood level; or (ii) any requirement set forth by the Administrator of the Federal Emergency Management Agency. (B) Multifamily housing (i) In general For rehabilitation of substantial damage or substantial improvement of multifamily housing, the Secretary may approve a proposal submitted by a grantee for an appropriate, cost-effective level of elevation above flood heights that is below the level described in subparagraph (A). (ii) Contents A proposal submitted under clause (i) shall describe how the proposed level of elevation will functionally achieve flood protection similar to or greater than the requirement described in subparagraph (A) with an alternative form of mitigation to assure the safety of residents and property, if applicable. (g) Administration In administering any amounts made available for assistance under this section, the Secretary— (1) may not allow a grantee to use any such amounts for any purpose other than the purpose approved by the Secretary in the plan submitted under subsection (d)(1) to the Secretary for use of those amounts; (2) may not permit a grantee to amend a plan to retroactively approve a beneficiary’s use of funds for an eligible activity other than an activity for which the funds were originally approved in the plan