The announcement was made on Flood Relief with Vince Gill and Friends, a telethon held on local TV station WSMV.
The money will go directly to various flood relief organisations in the city rocked by storms and flooding that killed 30 people in three states, including 20 in Tennessee.
The gift was announced by the show's host after the star, who moved to Nashville when she was 14, finished an interview.
Cleaning up and repair of the area is expected to cost more than one billion US dollars. Thousands of homes were damaged, along with some of Music City's most important landmarks.
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