You can't destroy the header or footer area in a Word 2016 document, but you can remove all text and other stuff: Edit the header or footer, press Ctrl+A to select everything, and press the Delete key. Poof!
The more official way to remove a header or footer is to follow these steps:
Edit the document's header or footer.
Click the Header & Footer Tools Design tab.
In the Header & Footer group, click the Header button.
Choose Remove Header.
The header is gone.
Click the Footer button and choose Remove Footer.
The footer is gone.