is filed by the taxpayer for any taxable year— (A) for purposes of determining the amount of any credit allowed under subsection (a) for such taxable year, the dollar amount under paragraph (1) shall be doubled, and (B) for purposes of determining the amount of any reduction under paragraph (2)(A) for any taxable year, the dollar amounts under such paragraph (after application of subparagraphs (B) and (C) of paragraph (2)) shall be doubled. (c) Definitions For purposes of this section— (1) Qualified disaster mitigation expenditure (A) In general The term qualified disaster mitigation expenditure means an expenditure relating to a qualified dwelling unit— (i) for property to— (I) improve the strength of a roof deck attachment, (II) create a secondary water barrier to prevent water intrusion or mitigate against potential water intrusion from wind-driven rain, (III) improve the durability, impact resistance (not less than class 3 or 4 rating), or fire resistance (not less than class A rating) of a roof covering, (IV) brace gable-end walls, (V) reinforce the connection between a roof and supporting wall, (VI) protect openings from penetration by wind-borne debris, (VII) protect exterior doors and garages from natural hazards, (VIII) complete measures contained in the publication of the Federal Emergency Management Agency entitled Wind Retrofit Guide for Residential Buildings (P–804), (IX) elevate the qualified dwelling unit, as well as utilities, machinery, or equipment, above the base flood elevation or other applicable minimum elevation requirement, (X) seal walls in the basement of the qualified dwelling unit using waterproofing compounds, or (XI) protect propane tanks or other external fuel sources, (ii) to install— (I) check valves to prevent flood water from backing up into drains, (II) flood vents, breakaway walls or open lattice for homes located in V zones, (III) a stormwater drainage system or improve an existing system, (IV) natural or nature-based features for flood control, including living shorelines,