; 1486)) $1,000,000,000 and any amounts appropriated pursuant to this section shall remain available until expended. (b) Water and energy efficiency Not less than 10 percent of all amounts made available pursuant to this section shall be used only for activities relating to water and energy efficiency and, at the Secretary’s discretion, other strategies to reduce emissions. 5. Flood Mitigation Assistance Grant Program (a) In general There is authorized to be appropriated for carrying out the Flood Mitigation Assistance Grant Program under section 1366 of the National Flood Insurance Act of 1968 ( 42 U.S.C. 4104c ) $1,000,000,000 and any amounts appropriated pursuant to this section shall remain available until expended. (b) Multifamily residences and attached and semi-Attached homes With regard to any structure that is a multifamily residence or an attached or semi-attached residence, the Administrator shall consult with the Secretary of Housing and Urban Development and establish alternative forms of mitigation. (c) Definitions For the purposes of this section, the term multifamily residence has the same meaning as in the Flood Disaster Protection Act of 1973 and the National Flood Insurance Act of 1968. 6. Housing Trust Fund (a) In general There is authorized to be appropriated for the Housing Trust Fund under section 1338 of the Housing and Urban Development Act of 1992 ( 12 U.S.C. 4568 ) $5,000,000,000 and any amounts appropriated pursuant to this subsection shall remain available until expended. The Secretary shall ensure that priority for occupancy in dwelling units assisted with amounts made available pursuant to this section that become available for occupancy shall be given to persons and households who are homeless (as such term is defined in section 103 of the McKinney-Vento Homeless Assistance Act ( 42 U.S.C. 11302 )) or at risk of homelessness (as such term is defined in section 401 of such Act ( 42 U.S.C. 11360 )). (b) Water and energy efficiency Not less than 10 percent of all amounts made