Show only Parent Forums on bbPress front page

Question

I want to show only the very top level forums on my front page. I have tried:

<?php if ( bb_forums("depth=1") ) : ?>

But that didn't work and all the forums still show up. I only want to show the very top level, so for example if I have the following forums:

Main
- Sub Forum 1
- Sub Forum 2
--- Sub Forum 2.1
--- Sub Forum 2.1
- Sub Forum 3
Community
- Sub Forum 1
- Sub Forum 2
--- Sub Forum 2.1
--- Sub Forum 2.1
- Sub Forum 3

Only Main and Community would appear on the home page.

I would seem I need to create a custom loop on the front page that will only show the very top level forums, but I need some help.

Thanks.