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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It's important to treat yourself well. Constantly deferring to others will deprive you of the finer things in life. Carve time out of your busy schedule to pamper yourself. Taking a nap, solitary walk or hot bath will revive your spirits. Get into the habit of spending more money on creature comforts. Treat such as gourmet food, beautiful clothes and intriguing books are investments in your happiness. Others may object at being put farther down on your list of priorities, but that's their problem.More